718 GT4/Spyder Is there a handling issue? - Page 3 - Boxster/Cayman - PistonHeads UK

I am slowly coming round to the way of thinking that the Latest GT4 and Spyder chassis may not be one of Porsche’s finest efforts. I think that something is less than ideal with the rear geometry when you push the car really hard. Most of this is just supposition and idle gossip but I do have some experience to back it up as well. My Spyder tried to kill me twice during track days and both times it was unexpected rear end breakaway mid corner at high speed and without any warning, I managed to gather it all up both times but it wasn’t nice. This was on a car set up for the track and in perfect condition. I also have many years of experience of racing and track driving under my belt so I know what I am doing. I am not tracking that car again! I had a 981GT4 and it was brilliant on track. Now the idle gossip! I watched most of this years N24 race, (what there was of it!) and as usual there was lots of midfield BMW and Porsche Cayman GT4 out to play. Literally every other shunt involved a GT4! Barely a few laps went passed without a GT4 falling off the track it was quite funny at times, we ran a book on how long before another one fell off. I was at Silverstone track day yesterday and blow me parked in the barriers was a very sad looking GT4. So is this all just coincidence or does the latest GT4 chassis have a few quirks? Any thoughts?

The GT4 Clubsport is a completely different setup from the road car. The front suspension for example is taken from the GT3 Cup. So I don't think race cars falling off the track would have any relevance.

bigmowley said: I am slowly coming round to the way of thinking that the Latest GT4 and Spyder chassis may not be one of Porsche’s finest efforts. I think that something is less than ideal with the rear geometry when you push the car really hard. Most of this is just supposition and idle gossip but I do have some experience to back it up as well. My Spyder tried to kill me twice during track days and both times it was unexpected rear end breakaway mid corner at high speed and without any warning, I managed to gather it all up both times but it wasn’t nice. This was on a car set up for the track and in perfect condition. I also have many years of experience of racing and track driving under my belt so I know what I am doing. I am not tracking that car again! I had a 981GT4 and it was brilliant on track. Now the idle gossip! I watched most of this years N24 race, (what there was of it!) and as usual there was lots of midfield BMW and Porsche Cayman GT4 out to play. Literally every other shunt involved a GT4! Barely a few laps went passed without a GT4 falling off the track it was quite funny at times, we ran a book on how long before another one fell off. I was at Silverstone track day yesterday and blow me parked in the barriers was a very sad looking GT4. So is this all just coincidence or does the latest GT4 chassis have a few quirks? Any thoughts? I heard about the 718 GT4 from yesterdays event also.. into Copse.... not nice. Interesting comments though.... and there are threads on other forums that raise similar points. There was a particular thread where a very very seasoned trackday driver and race series competitor in his 718 GT4 had a very high speed incident at Sochi - unexpected rear end breakaway on long high speed sweeper, which he has driven 1000's of times. In one of the 718 GT4/Spyder handling threads there is some supposition that for the road car at least, the PASM programming and the spring/damper setting for the rear might be making the car spiky? - also many people are just driving the car directly from the dealership and onto track without even getting a geo read to make sure the car is actually straight and not just within OEM range as set by the factory.. where they then don't get touched again even after transportation across Europe and the world. PASM programming doesn't explain what you observe at N24 - as those race cars are running Passive 2-way or 3-way suspension. I drove a friends 718 GT4 on a bit of a soon a few months back where we swapped cars for a while - he had complained about rear instability before, so i was cautious with it, because I'm so used to my car which is wearing a pretty good set-up. Pointed the 718 at the twisties, on power and immediately the rear started walking sideways in an unexpected manner.... so decided to keep the pace in check. He subsequently took for the car for full alignment and its much much better for him now. The car is particularly sensitive to toe settings on the rear - so need to ensure this is set. Edited by TDT on Tuesday 10th August 16:52

I’ve done over 5,000 miles in mine, mainly on track. Never had the back stepping out without me lifting off or simply carrying too much speed into the corner. DSC/ Traction Control can help cover a number of driving errors but your on your own pretty much with lift-off oversteer. Biggest issue is the understeer and lack of available camber on the rear without toe links. As TDT says though, the car needs a geo, if for no other reason than the speed you wreck front tyres without.

Yep, there's not enough camber from the factory and you really feel the difference in road holding when you crank it up.

Is this only a concern with track driving? Or is (spirited) road driving also an issue? If the car needs to be checked on alignment, what settings are recommended?

IMHO, as a minimum: Shims up front to get -2 deg of camber. Toe to taste. Max the rear camber to -1.5 on standard parts and also set the toe to taste. Leave ARB settings on mid-mid and ride height as standard.

Romo said: Is this only a concern with track driving? Or is (spirited) road driving also an issue? If the car needs to be checked on alignment, what settings are recommended? Rough guide: Fast Road & Light Track Use: There is quite a bit of variance in how much adjustability people might get out of a completely stock car... 100% OEM range might be the following: Front: Camber -1.6 to – 2.0; Toe zero, or slightly toe in Rear: Camber -1.4 to -1.6; Toe in. Moderate Track Use: You will need parts for this whether Porsche Motorsport or other aftermarket. Range might be the following: Front: Camber -2.5 to – 2.75; Toe zero, (or maybe very slightly toe out) Rear: Camber -2.0 to -2.25; Toe in. Aggressive Track Use: You will need parts for this whether Porsche Motorsport or other aftermarket. Range might be the following: Front: Camber -3.0 to -3.5; Slight toe out Rear: Camber -2.5 to -3.0; Toe in.

Oh good not just me them. Some good points here and certainly the lack of rear adjustment is a Porsche cock up without a shadow of a doubt. We could only just get my Spyder into the Porsche standard rear camber setting window without running out of toe adjustment on the std links. Matt fitted some old RSR links to mine, with a small mod I think, and that allowed a full range of adjustment. There are off the shelf links now I believe. This was not lift off oversteer by the way but flat out in fifth gear with everything settled and composed, or so I thought! As to the race cars I will stand to be corrected but the rear suspension is geometrically the same as I understand it just with more adjustment built in through the links and arms? The characteristics are typical of mid engined cars, but the GT4 does seem mighty sensitive at the limit.

bigmowley said: Oh good not just me them. Some good points here and certainly the lack of rear adjustment is a Porsche cock up without a shadow of a doubt. We could only just get my Spyder into the Porsche standard rear camber setting window without running out of toe adjustment on the std links. Matt fitted some old RSR links to mine, with a small mod I think, and that allowed a full range of adjustment. There are off the shelf links now I believe. As to the race cars I will stand to be corrected but the rear suspension is geometrically the same as I understand it just with more adjustment built in through the links and arms? The characteristics are typical of mid engined cars, but the GT4 does seem mighty sensitive at the limit. As you say, lots of options for adjustable rear toe links are available. Yep race cars are the exact same type of set up... they have slightly different rear wheel carriers for a lower roll center, and use a blade style ARB, and have adjustable toe links already. But it's still a McPherson strut based architecture. bigmowley said: This was not lift off oversteer by the way but flat out in fifth gear with everything settled and composed, or so I thought! Do you have any video to watch the moment back? - that can help you confirm what happened. I always run my GoPro on track so that i can review stuff. Its good fun! Edited by TDT on Tuesday 10th August 21:29

TDT said: Rough guide: Fast Road & Light Track Use: There is quite a bit of variance in how much adjustability people might get out of a completely stock car... 100% OEM range might be the following: Front: Camber -1.6 to – 2.0; Toe zero, or slightly toe in Rear: Camber -1.4 to -1.6; Toe in. Moderate Track Use: You will need parts for this whether Porsche Motorsport or other aftermarket. Range might be the following: Front: Camber -2.5 to – 2.75; Toe zero, (or maybe very slightly toe out) Rear: Camber -2.0 to -2.25; Toe in. Aggressive Track Use: You will need parts for this whether Porsche Motorsport or other aftermarket. Range might be the following: Front: Camber -3.0 to -3.5; Slight toe out Rear: Camber -2.5 to -3.0; Toe in. Tx. great info. will get my spyder set up for fast road once it comes in.

bigmowley said: This was not lift off oversteer by the way but flat out in fifth gear with everything settled and composed, or so I thought! Flat out in 5th? What track/corner were you taking? Have you changed geo at all? Was this pre or post apex? As TDT says, video would help a lot. I’ve never experienced anything like that. The car is mid engined so it’s going to turn quickly, especially at the speeds you’d be doing flat out in 5th, but I’ve always found it predictable rather than spiky personally. AFAIK, the Silverstone crash yesterday was more to do with the heavy rain and the car aqua planing rather that any particular handling characteristics, but you were there, what happened?

TDT said: bigmowley said: Do you have any video to watch the moment back? - that can help you confirm what happened. I always run my GoPro on track so that i can review stuff. Its good fun! Edited by TDT on Tuesday 10th August 21:29 I usually have the GoPro running but i hate watching it back . I just get cross with myself every time I make a mistake or don’t hit the apex. I have got one big twitch on film at the ring. Now in my defense i don’t like the ring and I just haven’t done enough laps there to really build up some pace. I did a track day there on my own last summer to try to learn it a bit better and that helped loads, much better than tourist laps. This one is more about the corner than the car, now I know it’s there I can do it quicker with a bit of corrective lock just before the kick, still scary though, doesn’t look much in the video but it was a right tank slapper It’s here: https://youtu.be/VimdIR2BCM4 Sorry about the crap editing. My really big moment was at Goodwood and I didn’t have the camera in for that one. There was a dirty great big set of tyre marks on the track and the tyres were buggered afterwards.

keepup said: bigmowley said: This was not lift off oversteer by the way but flat out in fifth gear with everything settled and composed, or so I thought! Flat out in 5th? What track/corner were you taking? Have you changed geo at all? Was this pre or post apex? As TDT says, video would help a lot. I’ve never experienced anything like that. The car is mid engined so it’s going to turn quickly, especially at the speeds you’d be doing flat out in 5th, but I’ve always found it predictable rather than spiky personally. AFAIK, the Silverstone crash yesterday was more to do with the heavy rain and the car aqua planing rather that any particular handling characteristics, but you were there, what happened? I wasn’t there, but heard about the incident and it sounds much more like it was down to the conditions and Aquaplaning at those high speeds more than anything else. Shame as not long after it all dried up and was set until end of day.

bigmowley said: My really big moment was at Goodwood and I didn’t have the camera in for that one. There was a dirty great big set of tyre marks on the track and the tyres were buggered afterwards. Where at Goodwood…. Fordwater? You do have to be careful there and the circuit moves up and down and can catch people out if you try to stay completely flat.. you need to ‘breathe’ the throttle with the circuit through there in my experience.

TDT said: bigmowley said: My really big moment was at Goodwood and I didn’t have the camera in for that one. There was a dirty great big set of tyre marks on the track and the tyres were buggered afterwards. Where at Goodwood…. Fordwater? You do have to be careful there and the circuit moves up and down and can catch people out if you try to stay completely flat.. you need to ‘breathe’ the throttle with the circuit through there in my experience. Impressive track knowledge yes Fordwater, had done it flat every time before that lap, and afterwards just to check I hadn’t lost my bottle

TDT said: Romo said: Is this only a concern with track driving? Or is (spirited) road driving also an issue? If the car needs to be checked on alignment, what settings are recommended? Rough guide: Fast Road & Light Track Use: There is quite a bit of variance in how much adjustability people might get out of a completely stock car... 100% OEM range might be the following: Front: Camber -1.6 to – 2.0; Toe zero, or slightly toe in Rear: Camber -1.4 to -1.6; Toe in. Moderate Track Use: You will need parts for this whether Porsche Motorsport or other aftermarket. Range might be the following: Front: Camber -2.5 to – 2.75; Toe zero, (or maybe very slightly toe out) Rear: Camber -2.0 to -2.25; Toe in. Aggressive Track Use: You will need parts for this whether Porsche Motorsport or other aftermarket. Range might be the following: Front: Camber -3.0 to -3.5; Slight toe out Rear: Camber -2.5 to -3.0; Toe in. Thanks, much apreciated ! Can the aliignment change be done at the OPC, or a spelialists job? Edited by Romo on Wednesday 11th August 06:08

Romo said: Thanks, much apreciated ! Can the aliignment change be done at the OPC, or a spelialists job? Edited by Romo on Wednesday 11th August 06:08 Ref OPC, I think it depends. A number of OPCs are now offering ‘GT car setups’…. but I’d imagine that it they would still fall into the factory ranges for Geos which may or may not be enough for you. You could ask your service dept and see what they say. So then it’s a specialists/independents job. There are quite a few about, so it depends on where you are.

Romo said: Thanks, much apreciated ! Can the aliignment change be done at the OPC, or a spelialists job? Anything outside Porsche specs will need fo be done at a specialist, which is camber greater than -1.5 degrees on either the front or rear axle. I'd go to a specialist anyway, OPCs don't generally seem inclined to set alignment very accurately, as long as it's within (a wide) tolerance they'll say it's OK.

bigmowley said: TDT said: bigmowley said: My really big moment was at Goodwood and I didn’t have the camera in for that one. There was a dirty great big set of tyre marks on the track and the tyres were buggered afterwards. Where at Goodwood…. Fordwater? You do have to be careful there and the circuit moves up and down and can catch people out if you try to stay completely flat.. you need to ‘breathe’ the throttle with the circuit through there in my experience. Impressive track knowledge yes Fordwater, had done it flat every time before that lap, and afterwards just to check I hadn’t lost my bottle Haha ok. So I’ve seen car off through there including a GT4 that was totalled. There is a line you can take through there which you can stay flat depending on the car but as it rises and falls though there you do need to be careful and just maybe manage the throttle and steering, and ‘breathe gently’ with the circuit. Looks innocent until you drive it at speed. Great feeling when you get it right, through there though.

TDT said: Haha ok. So I’ve seen car off through there including a GT4 that was totalled. There is a line you can take through there which you can stay flat depending on the car but as it rises and falls though there you do need to be careful and just maybe manage the throttle and steering, and ‘breathe gently’ with the circuit. Looks innocent until you drive it at speed. Great feeling when you get it right, through there though. That sounds a lot like the corner in the video. The car seems to get upset while the left rear is compressed. I’m not smart enough to know what kind of weakness on the car (if any) that points to.

le_gazman said: TDT said: Haha ok. So I’ve seen car off through there including a GT4 that was totalled. There is a line you can take through there which you can stay flat depending on the car but as it rises and falls though there you do need to be careful and just maybe manage the throttle and steering, and ‘breathe gently’ with the circuit. Looks innocent until you drive it at speed. Great feeling when you get it right, through there though. That sounds a lot like the corner in the video. The car seems to get upset while the left rear is compressed. I’m not smart enough to know what kind of weakness on the car (if any) that points to. The ‘yump’ in the video from the ring is a bit more pronounced than it is through Fordwater imo, but, quite right, the effect is similar.

Interesting discussion if unexpected. There aren't any really major differences in suspension afaik between the 981 and 718 with spring rates, geometry settings are going to be broadly similar, I can't imagine that ride height or weight distribution is dramatically different. As TDT suggest the main remaining factor might be PASM programming but that wouldn't be affecting the race cars...... Unusual that this instability/nervousness wasn't an issue on the 981 really if it is now.

bigmowley said: It’s here: https://youtu.be/VimdIR2BCM4 You need some driver training at the 'ring before blaming the car for that IMHO. Your throttle application is most likely at fault through pflanzgarten as through the various edits you're off and on all over the place. I couldn't rule out you clipping the inside curb either even if you were unaware of it (my mate liked to do that to scare passengers on laps back in the day-it's surprising what a good launch it gives you!). FYI, in the 997 GT3 RS I'll short shift into 5th gear and stay flat on the throttle all the way through pflanzgarten 2, the S's and into Schwalbenschanz. Staying 4th and into 5th will be quicker but I personally find I'm faster being more confident in keeping the car more settled without the change mid way through.

Could it be 911 drivers switching to GT4s and not adjusting driving style accordingly? Less weight on the rear than they're used to? I find it hard to believe that the 718 is that different thi the 981 as I believe the chassis hardware is identical across versions.

Twinfan said: Could it be 911 drivers switching to GT4s and not adjusting driving style accordingly? Less weight on the rear than they're used to? I find it hard to believe that the 718 is that different thi the 981 as I believe the chassis hardware is identical across versions. Most 911 drivers, certainly in the 991s onwards drive them much like mid engine cars anyway with the weight creeping ever forward and with all the electronic stuff to make it handle less like rear engine one But I don't think so anyway, bigmowley was saying the car was unsettled mid corner all of a sudden. At that point, in my (very limited) understanding there wouldn't really be all that much difference in driving styles.

Fair point, just musing

TDT said: Ref OPC, I think it depends. A number of OPCs are now offering ‘GT car setups’…. but I’d imagine that it they would still fall into the factory ranges for Geos which may or may not be enough for you. You could ask your service dept and see what they say. So then it’s a specialists/independents job. There are quite a few about, so it depends on where you are. I live in the netherlands, Porsche enthousiast go to Jan Steverink Tyre centre Apedoorn https://www.steverinkbanden.nl/specialiteiten/uitl... They use Hunter's HawkEye Elite geo system, FWIW

LaurasOtherHalf said: bigmowley said: It’s here: https://youtu.be/VimdIR2BCM4 You need some driver training at the 'ring before blaming the car for that IMHO. Your throttle application is most likely at fault through pflanzgarten as through the various edits you're off and on all over the place. I couldn't rule out you clipping the inside curb either even if you were unaware of it (my mate liked to do that to scare passengers on laps back in the day-it's surprising what a good launch it gives you!). FYI, in the 997 GT3 RS I'll short shift into 5th gear and stay flat on the throttle all the way through pflanzgarten 2, the S's and into Schwalbenschanz. Staying 4th and into 5th will be quicker but I personally find I'm faster being more confident in keeping the car more settled without the change mid way through. Totally agree on all points. I’ve only ever done about 30 laps in the last 20 years and I don’t like the place that much. I have decided to try to learn it better before I get too old. I am not in the slightest bit interested in lap times there just want to be quick and safe. TBH I was a bit pissed off that my lad drives it so much better than me, can’t be having that now can we . PlayStation generation and all that. I have been booked for a couple more days this year but they have had to be postponed, currently back early October for another session. I will take the R8 this time as it’s definitely a nicer chassis.

TDT said: Haha ok. So I’ve seen car off through there including a GT4 that was totalled. There is a line you can take through there which you can stay flat depending on the car but as it rises and falls though there you do need to be careful and just maybe manage the throttle and steering, and ‘breathe gently’ with the circuit. Looks innocent until you drive it at speed. Great feeling when you get it right, through there though. On that day I was using the R8 as well. Similar configuration but quite a bit quicker. I never had any issues with the R8 at all a little bit quicker too but not flat obviously. What surprised me and very nearly caught me out was that the Porsche gave no warning and went from a nice balanced drift into a massive oh my god slide very suddenly. It took a hell of a long time to gather it up as well. It wasn’t the actual stepping out of line that frightened me but the severity of it and the duration of it. My point is that right on the limit they do seem a bit sensitive.

bigmowley said: LaurasOtherHalf said: bigmowley said: It’s here: https://youtu.be/VimdIR2BCM4 You need some driver training at the 'ring before blaming the car for that IMHO. Your throttle application is most likely at fault through pflanzgarten as through the various edits you're off and on all over the place. I couldn't rule out you clipping the inside curb either even if you were unaware of it (my mate liked to do that to scare passengers on laps back in the day-it's surprising what a good launch it gives you!). FYI, in the 997 GT3 RS I'll short shift into 5th gear and stay flat on the throttle all the way through pflanzgarten 2, the S's and into Schwalbenschanz. Staying 4th and into 5th will be quicker but I personally find I'm faster being more confident in keeping the car more settled without the change mid way through. Totally agree on all points. I’ve only ever done about 30 laps in the last 20 years and I don’t like the place that much. I have decided to try to learn it better before I get too old. I am not in the slightest bit interested in lap times there just want to be quick and safe. TBH I was a bit pissed off that my lad drives it so much better than me, can’t be having that now can we . PlayStation generation and all that. I have been booked for a couple more days this year but they have had to be postponed, currently back early October for another session. I will take the R8 this time as it’s definitely a nicer chassis. Funnily enough, at my mates 50th we played on his son's Playstaion rig at the end of the night and despite being well sloshed, I posted a near identical time to what I do in real life! It's very accurate and a great way to learn. Pick someone good to learn it from and you can be insanely good these days very quickly-I would have say learning it the old school way took me more than 80 laps, I reckon I was good once I got past 500!

bigmowley said: TDT said: Haha ok. So I’ve seen car off through there including a GT4 that was totalled. There is a line you can take through there which you can stay flat depending on the car but as it rises and falls though there you do need to be careful and just maybe manage the throttle and steering, and ‘breathe gently’ with the circuit. Looks innocent until you drive it at speed. Great feeling when you get it right, through there though. On that day I was using the R8 as well. Similar configuration but quite a bit quicker. I never had any issues with the R8 at all a little bit quicker too but not flat obviously. What surprised me and very nearly caught me out was that the Porsche gave no warning and went from a nice balanced drift into a massive oh my god slide very suddenly. It took a hell of a long time to gather it up as well. It wasn’t the actual stepping out of line that frightened me but the severity of it and the duration of it. My point is that right on the limit they do seem a bit sensitive. Double wishbone all around on the R8, Means that its geometry will main it's shape much more consistently vs McPherson strut through the arc of movement. Unequal length Arm top to bottom mean that as you lean on a corner more... you will get more neg camber as the suspension compresses. It's just more sophisticated and therefore expensive.

TDT said: Double wishbone all around on the R8, Means that its geometry will main it's shape much more consistently vs McPherson strut through the arc of movement. Unequal length Arm top to bottom mean that as you lean on a corner more... you will get more neg camber as the suspension compresses. It's just more sophisticated and therefore expensive. While all entirely right, it doesn't quite explain why the OP (and some others it seems) have not had the same issue for the 981 which I believe he has also had before. 718 and 981 are struts.....

isaldiri said: TDT said: Double wishbone all around on the R8, Means that its geometry will main it's shape much more consistently vs McPherson strut through the arc of movement. Unequal length Arm top to bottom mean that as you lean on a corner more... you will get more neg camber as the suspension compresses. It's just more sophisticated and therefore expensive. While all entirely right, it doesn't quite explain why the OP (and some others it seems) have not had the same issue for the 981 which I believe he has also had before. 718 and 981 are struts..... Agreed. I don't think there is a difference, doesn't appear so from hardware part numbers - Only possibly the PASM/PSM configuration between the road car generations. The GT4 i've seen go off heavily at the same spot was a 981... so it's going to be down to specific setup on the individual car, in particular toe and then whatever the driver is doing at that point.

Some very knowledgable posters on this thread re set up PH at its best....

isaldiri said: While all entirely right, it doesn't quite explain why the OP (and some others it seems) have not had the same issue for the 981 which I believe he has also had before. 718 and 981 are struts..... Who else has had issues, I didn't read that in the thread. The 'ring video suggest a rather binary application of the throttle won't be helping the balance. Would love to see the clip of going flat through Fordwater in a GT4, as TDT says, it's bumpy through there and definitely pushing the limits. My best is 50% throttle application from a 1:26.6 lap (stock geo).

keepup said: isaldiri said: While all entirely right, it doesn't quite explain why the OP (and some others it seems) have not had the same issue for the 981 which I believe he has also had before. 718 and 981 are struts..... Who else has had issues, I didn't read that in the thread. The 'ring video suggest a rather binary application of the throttle won't be helping the balance. Would love to see the clip of going flat through Fordwater in a GT4, as TDT says, it's bumpy through there and definitely pushing the limits. My best is 50% throttle application from a 1:26.6 lap (stock geo). That is a really interesting graph. What gear would you have been in there? The rate of acceleration is remarkably linear between 50% throttle and 100%. I don’t collect data on track days, I only do them for fun after all, but it’s good to see. I was using 5th gear after a short shift on the little straighter bit after Madgwick, then completely flat. I was enjoying it as it was clearly close to or on the limit at that and there was a bit of work to do to keep on line. Interesting to see your speed on that trace as I was fairly sure that I was at around 135mph which looks about right on your numbers. I am not on standard geo. Ignore the Ring bit it’s not my finest driving . I like cars that move around a bit and I am a bit rough with my inputs, not ideal I know but I’ve been like that for the last 42 years of racing, rallying and circuit driving so I’m not going to change now.

isaldiri said: Interesting discussion if unexpected. There aren't any really major differences in suspension afaik between the 981 and 718 with spring rates, geometry settings are going to be broadly similar, I can't imagine that ride height or weight distribution is dramatically different. As TDT suggest the main remaining factor might be PASM programming but that wouldn't be affecting the race cars...... Unusual that this instability/nervousness wasn't an issue on the 981 really if it is now. I did wonder if the additional aero on the 718, I think it’s 50% more? was having any impact compared to the 981. In my limited experience the 981 is a nicer car on the limit than the 718. It would appear that some people agree.

bigmowley said: I did wonder if the additional aero on the 718, I think it’s 50% more? was having any impact compared to the 981. In my limited experience the 981 is a nicer car on the limit than the 718. It would appear that some people agree. Of all the potential reasons for that difference, imo aero is likely amongst the least likely. 50% more of not a lot that in total makes up a pretty small % of the total overall weight of the car means the net effect of downforce is small and probably very small at that. Now I admit to being in a little biased given i have constantly been bemused at the touting of 'downforce' on road cars as the latest marketing must have but so far, there hasn't really been all that much that realistically suggests how all that supposed downforce is making a huge difference on 1400+kg cars....

I’ve had my 718 for a week now and put 1850 miles on it blasting round the Highlands and I’m definitely not happy with the rear end when pushing on (especially) in the wet. It’s booked in on Friday for a fast road set up at a local recommended place. I know how I liked my old 911s but not sure what to ask for rear stability with regards to toe on the GT4? Will some extra toe in make it more stable like the old 911s? At this stage I’m not going to add shims or links but might in the future. Any expert advice would be appreciated.

johnycarrera said: I’ve had my 718 for a week now and put 1850 miles on it blasting round the Highlands and I’m definitely not happy with the rear end when pushing on (especially) in the wet. It’s booked in on Friday for a fast road set up at a local recommended place. I know how I liked my old 911s but not sure what to ask for rear stability with regards to toe on the GT4? Will some extra toe in make it more stable like the old 911s? At this stage I’m not going to add shims or links but might in the future. Any expert advice would be appreciated. Welcome to the world of 718 rear suspension adjustment. I can only speak for my car but Matt at Fernsport did the work on mine and with the standard components as delivered new he could only just get my car to the factory settings for camber and toe. The problem was that as you dial in more negative camber you run out of adjustment on the toe links to set the correct toe. Normally you would expect the factory settings to sit in the middle of an adjustment window. Not on my car. To get more toe adjustment I would have to sacrifice rear negative camber. I think you will need to play around with yours to see what you can do, just don’t expect a lot of adjustment to be possible without changing parts. Incidentally I never had any problem with my 981 GT4 rear adjustment so something is different.

Hmmm, so for better stability, sacrifice “some” rear camber and go with more toe until starting to add links and shims? I’m so used to driving old 911s on their nose to get them to turn in and having a planted rear end. My 981CGTS with X73 ARBs would run rings round this GT4 but maybe it’s just crap out the factory and I’ll be happy with a decent fast road set up ignoring the actual factory settings. I can learn to drive around it as long as the rear is stable.

johnycarrera said: I’ve had my 718 for a week now and put 1850 miles on it blasting round the Highlands and I’m definitely not happy with the rear end when pushing on (especially) in the wet. It’s booked in on Friday for a fast road set up at a local recommended place. I know how I liked my old 911s but not sure what to ask for rear stability with regards to toe on the GT4? Will some extra toe in make it more stable like the old 911s? At this stage I’m not going to add shims or links but might in the future. Any expert advice would be appreciated. Set up in the rear is going to be somewhat limited, with stock parts only. If you look back a few posts you’ll see the upper range for stock parts under fast road/light track. The main issue being that the standard rear toe link whilst being a spherical joint… is a fixed length rod. All the adjustment is in the eccentric bolt which doesn’t really give much scope. So usually the first thing to do is to change this arm out for an adjustable one which gives much more range. Of course you don’t have to do this…but it’s a great help. Why is this even a problem?… as the wheel moves up and down, based on rear suspension architecture, the toe angle actually changes (dynamic toe) so as the rear becomes unloaded toe moves out.. if you haven’t started with much toe in the first place you can end up in a toe out situation which makes that wheel then very reactive… which we then get as instability…. To counter…. We add more toe-in (statically) so that as the rear get unloaded and the toe moves out(dynamically)...we don’t get to a toe-out situation and the rear stays moving in the direction we want it and not undesirably reactive. The other element on the rear (certainly for 981 GT4) to consider is what is mostly solid mounted or ball joints which is great apart from one key joints… the LCA inner… this is a hard rubber bushing and this will be for a number reason probably chiefly NVH, but the problem is that because every other joint on the rear is solid, if there is high loading it is the only joint that has any give in it and all the load can be localised and inflected onto this bushing…. small movements here can also contribute. As it is, this part will perish, like all rubber, and a common mod is to replace this is with a spherical bushing. The benefit is precision. Some one would need to check if the 718 LCA is also a rubber bushing in the LCA, as I know for 991.2 GT3 and RS Porsche went to more spherical bushings (which will come with its own maintenance schedule/burden). If it is a solid LCA then it’s possible that zero give, in the rear is causing a kick back in certain conditions, and the forces actually kick back all the way to the contact patch, and this makes the rear unstable? Where the 981 rubber LCA inner might soak a little bit up so then you don’t get the kick back though the rear. That’s a pure guess, and probably wrong though, as I believe so far that all the hardware is the same 981-> 718, and I had looked at most of it myself before, a part from this part, but just thought to mention it as a possibility. Edited by TDT on Wednesday 11th August 22:14

Thanks TDT that’s really helpful and interesting. I’m sure in the end we’ll all get them right and it’s not too expensive, I’m not looking for the last 10th, just something that’s predictable in all situations and I don’t get a totally unexpected tank slapper on the road, more so the fear that goes with not knowing if it’s going to bite you!

What settings were you driving in when it happened? I assume suspension was in Sport but what traction and stability settings were you using? Do you know / remember if you happened to make any slight throttle or, especially, steering corrections just prior (within m/s) to the issue? I am not entirely sure but I do wonder if stability management software can cause issues if you react (pre-emptively, from feel) just as / prior to the software reacting and suddenly you're in an overcorrection situation. Evos with the Anti-Yaw Control are renowned for spitting people off of the track and I'm sure that is a result of overcorrection induced by the AYC. Likely much different in a Porsche and with more modern ESM & TC software but if a 4WD, front-engined Evo can be spat off track then a mid-engined, RWD car most definitely could. Probably barking up the wrong tree but it just makes me wonder ...

TDT said: Set up in the rear is going to be somewhat limited, with stock parts only. If you look back a few posts you’ll see the upper range for stock parts under fast road/light track. The main issue being that the standard rear toe link whilst being a spherical joint… is a fixed length rod. All the adjustment is in the eccentric bolt which doesn’t really give much scope. So usually the first thing to do is to change this arm out for an adjustable one which gives much more range. Of course you don’t have to do this…but it’s a great help. Why is this even a problem?… as the wheel moves up and down, based on rear suspension architecture, the toe angle actually changes (dynamic toe) so as the rear becomes unloaded toe moves out.. if you haven’t started with much toe in the first place you can end up in a toe out situation which makes that wheel then very reactive… which we then get as instability…. To counter…. We add more toe-in (statically) so that as the rear get unloaded and the toe moves out(dynamically)...we don’t get to a toe-out situation and the rear stays moving in the direction we want it and not undesirably reactive. The other element on the rear (certainly for 981 GT4) to consider is what is mostly solid mounted or ball joints which is great apart from one key joints… the LCA inner… this is a hard rubber bushing and this will be for a number reason probably chiefly NVH, but the problem is that because every other joint on the rear is solid, if there is high loading it is the only joint that has any give in it and all the load can be localised and inflected onto this bushing…. small movements here can also contribute. As it is, this part will perish, like all rubber, and a common mod is to replace this is with a spherical bushing. The benefit is precision. Some one would need to check if the 718 LCA is also a rubber bushing in the LCA, as I know for 991.2 GT3 and RS Porsche went to more spherical bushings (which will come with its own maintenance schedule/burden). If it is a solid LCA then it’s possible that zero give, in the rear is causing a kick back in certain conditions, and the forces actually kick back all the way to the contact patch, and this makes the rear unstable? Where the 981 rubber LCA inner might soak a little bit up so then you don’t get the kick back though the rear. That’s a pure guess, and probably wrong though, as I believe so far that all the hardware is the same 981-> 718, and I had looked at most of it myself before, a part from this part, but just thought to mention it as a possibility. Great post. There's a reason for everything the engineers at Porsche do, and that sole remaining rubber bush in the rear suspension will be there with good reason. Of course one would hope the reason is not down to cost ... but rather that the rear suspension needed/relied on that additional bit of compliance in extremis, but ... Porsche have previous on these matters, and we only have to head back to twenty years to the introduction of the 996 GT2 to see a similar "flaw" in its rear suspension. The 996 GT2 used (I think) the widest section rear tyres ever fitted to roadgoing 911 up until then, those being specially designed 315 section PS2's. I did a driving limits day with Bernard Aubrey in my car at Chobham : https://www.pistonheads.com/gassing/topic.asp?t=93... and in the safety of a grippy wide open space, Bernard asked me to drive round in circles on a fixed throttle setting and constant steering input/radius. Once the car was settled, he asked me to increase the throttle whilst maintaining the same steering input. I expected the rear to quickly lose grip and to spin shortly after, but I was staggered just how much grip those 12" wide tyres were capable of serving up before they lost their battle with the car's prodigious torque and horsepower. I expressed my surprise to Bernard, who quickly responded that the surface at Chobham was very grippy, but also it was smooth and that there were no poor road repairs, drain covers or surface changes to contend with ... Despite this excellent insight as to just how much grip the old PS2's were capable of generating, the engineers at Porsche chose to retain the standard 996 Turbo rear toe arms complete with marshmallows for bushes on the inner end. My guess is these parts also saw duty on the C2/C4 and the Mk 1 GT3 ... Neither of those cars had tyres anything like as wide as the GT2, nor did they have its prodigious torque. The X50 Turbo did have the same torque figure, but was equipped with 4 wheel drive and narrower tyres, so perhaps the standard toe links were considered up to the task. Just. When it came to the 996 Cup cars, which had considerably less power than the GT2, but would have been running fat, grippy slicks, the Motorsport dept sensibly specified a toe link with LH and RH threads that enabled it be adjusted without resorting to the hopeless stock eccentric bolt arrangement, and a chunky spherical bearing at its inner end to remove every last vestige of compliance from the arm, and they specified lockout plates in the rear crossmember to ensure the eccentric adjustment bolts/washers could not shift and allow the toe to change. I had the Cup rear toe links fitted to the GT2, it made the rear of the car a lot more stable, but also a lot more predictable ... One wonders whether that rubber bush in the rear LCA on the 718 Cayman GT4 needs eradicating to ensure the same strange things don't happen to the camber in extremis as the toe arms on the 996 GT2 ... Edited by Slippydiff on Thursday 12th August 17:58

So just had the call from my local geo guys and out of the factory not one wheel was pointing in the same direction, no wonder I was having major difficulties in the wet! Not ideal as I set off on an 1800 mile Highland Hoon the day after it was PPF’d Anyway as said, they could only get 1.5 degrees of camber at the rear to get the required toe in so maybe look at adjustable toe arms next. Car was already booked in but glad I saw this post, definitely worth checking straight from the factory!

johnycarrera said: So just had the call from my local geo guys and out of the factory not one wheel was pointing in the same direction, no wonder I was having major difficulties in the wet! Not ideal as I set off on an 1800 mile Highland Hoon the day after it was PPF’d Anyway as said, they could only get 1.5 degrees of camber at the rear to get the required toe in so maybe look at adjustable toe arms next. Car was already booked in but glad I saw this post, definitely worth checking straight from the factory! Speak to Chris and Pete at Center Gravity, they'll confirm that most of the brand new Porsches they see, have poorly adjusted suspension that's often out of, or right on the limits of the specified tolerances. Two things are at play here, first the production line operative will adjust the settings so they're in tolerance and nothing more, and secondly, as the suspension/springs settles in the days/weeks after manufacture, the already mediocre geometry adjustment will be compromised (the lower the car settles, the more camber and toe increases). Many, many years ago there was guy who wrote a running report on his 3.2 Carrera for 911 & Porsche World, he said the first thing he did with all of his new Porsches, was to have the ride heights checked and adjusted, the end result corner weighted and the geometry adjusted accurately. And that was when Porsche pretty much handbuilt the cars and actually cared about their customers ...

The timing is amusing/amazing…

Question remains; Would the caused lift off over steer been different, i.c. resulting in no accident, if the geo would have been changed as recommended on the 1st page overhere?

Interesting video, poor bloke has quite a crashathon just of late. Fundamentally everything he says is OK. A few things I would add are that lift off oversteer in a mid engined car can be quite a desirable characteristic and you use it to tighten the line or to reduce understeer. Obviously it’s about being gentle with the throttle inputs, I find that normally the Spyder, in my case, is easy to balance on the throttle. Not every mid engined car will go into full oversteer on a rough lift off. My beef with my car was that it went into a humongous oversteer slide without any throttle lift so not lift of oversteer. I held onto it through counter steering without lifting. I know full well that if I had lifted it would have buried itself in the earth bank on the outside of Fordwater, which is not a place I ever want to be.

bigmowley said: This one is more about the corner than the car, now I know it’s there I can do it quicker with a bit of corrective lock just before the kick, still scary though, doesn’t look much in the video but it was a right tank slapper It’s here: https://youtu.be/VimdIR2BCM4 You went up the kerb, at the second 'jump' in the pflanzgarten section (Sprunghügel), where touching the kerb is a no-no ;-) https://www.youtube.com/watch?v=n6O06XenkL0&t=... https://www.youtube.com/watch?v=7kjhyVJSeeA&ab... The above two videos represent decent drivers at the ring in a GT4, both of which are going through that section similar-ish speed, maybe a bit faster Not sure that one was anything related to the car Edit - I've just checked your full lap vid... you have lots of 'moments' where you shouldn't have, e.g. T13, the exit of hatzenbach, Aremberg, miss-hit-miss, brunchen2 I'd recommend: a) get your hands at 9 and 3, not 10 and 2 (or 11 and 1 at times) b) smoother inputs on throttle and steering, and deffo avoid tugging at the wheel and fully lifting off the accelerator c) get TC and ESC back on - you're not Kevin Estre ;-) d) avoid the kerbs... you clip them at times in dangerous points, i was nervous watching the foxhole! e) close the cup holder in the middle to stop it sliding around... could see that lucozade falling out lol Might be worth some tuition, a few of your lines are a bit off and it'll put you in the right bit of the track for each corner, which makes things easier and faster. Bergwerk, kleines-karussel and galgenkopf looked a bit uncomfortable Edited by dashobbit on Tuesday 17th August 16:28