Interesting info: Rear ARB sizes for all 997 models inside! - Page 2 - Porsche General - PistonHeads UK

Hi there I love all tech type stuff and others may find this interesting especially those tuning the handling dynamics of their cars with roll bars:- 997.1 C2S PASM rear ARB to be 19.6 x 2.6 mm 997.1 C4           standard                        22.5 x 3.5mm 997.1 C4           PASM                           18.5 x 2.5mm 997.1 C4           sports                           19.6 x 2.6mm 997.1 C4S         PASM                           18.5 x 2.5mm 997.1 C4S         sports                           19.6 x 2.6mm 997.1 Turbo       w/o rear diff lock             21.7 x 3.0mm 997.1 Turbo       with rear diff lock            22.5 x 3.5mm 997.1 GT3/RS                                        23.6 x 3.5mm 997.1 GT2 / 997.2 GT3                          25.2 x 4.4mm 997.2 C2           standard                        18.5 x 2.5mm 997.2 C2           PASM                           18.5 x 2.5mm 997.2 C2           PASM + sports              18.5 x 2.5mm 997.2 C2S         PASM                           19.6 x 2.6mm 997.2 C2S         PASM + sports              18.5 x 2.5mm 997.2 C4           standard                        20.7 x 2.8mm 997.2 C4           PASM                           21.7 x 3.0mm 997.2 C4           PASM + sports              20.7 x 2.8mm 997.2 C4S         PASM                           21.7 x 3.0mm 997.2 C4S         PASM + sports              20.7 x 2.8mm Interesting info and clearly shows on 997.2 GT3 Porsche fitted the rear GT2 bar to dial out understeer the new GT3 had. Anyone knows any other measurements be good to add them to this thread. Even better is the rear arbs direct from Porsche are only approx £150

The 997.1 GT3 ARB doesn't exist anymore. It was too small and Porsche superseded it to the GT2 size. This bar spec was then given a new number and applied across the entire GT3 range for both 997.1 and 997.2 There was no notice of the change however. It's up to owners to be proactive and buy a new one if they have the original small version.

fioran0 said: The 997.1 GT3 ARB doesn't exist anymore. It was too small and Porsche superseded it to the GT2 size. This bar spec was then given a new number and applied across the entire GT3 range for both 997.1 and 997.2 There was no notice of the change however. It's up to owners to be proactive and buy a new one if they have the original small version. Yep I remember you saying, as it was a good move to help cure understeer on the 997.1 GT3s. I did try a GT2 bar in my 997.1 C2S, but I gave too much oversteer, even on softest setting. No doubt simply due to the lack of grip in the rear on a C2S with it's skinnier tyres and lack of LSD. Am contemplating giving the stock C4 bar a go as at 22.5 x 3.5 mm it's thicker than my C2S bar but nowhere near as thick/stiff as the GT2 bar so worth a go I think to see if it gives me the result I need.

What front bar do you have fitted?

I am not surprised you had over steer with a GT3 rear bar as the front will be too soft and also you will not be running enough negative camber on std C2S suspension. The roll bar is just a final adjustment in my book, the spring rate and damper settings have to take priority then adjust with the bar. If still on std dampers/springs then the bar may be too stiff for the setup? How is the engine upgrade coming along ? Mike

But springs/shock settings and sway bars are controlling different things? Spring and shock settings are primarily concerned with wheel control and fore/aft movement while sway bars are primarily concerned with roll and its associated side/side forces.

Reading the above I might consider swapping a7 GT2 rear bar for the one on my 7GT3, anyone wtb my 7gt3 bar cheap ? PM me.

Nice one Gibbo! I'll have to have a look and see if mine has an early or late one - because I get very little understeer .... Has anyone with a 997 GT3 done the swap to the 997 GT2 bar?

I had one of the 1st 997.1 GT3 RS's in UK, ( orange 2006 car) and upgraded this pretty soon after purchase. I wouldn't have said this is I final solution to dialling out the understeer. I ran the new bar on full stiff, and the car was pretty damned snappy on the limit. Never had a chance to move the bar off of full stiff to try next setting down, before I sold it, and am now on passive dampers on my green car, so will never know. G.

fioran0 said: gibbo if he is wanting a smaller one Edited by fioran0 on Monday 7th January 15:17 I have the 997.2 GT3 bar, could swap for your 997.1 GT3 bar if you wanted?

sportsandclassic said: I am not surprised you had over steer with a GT3 rear bar as the front will be too soft and also you will not be running enough negative camber on std C2S suspension. The roll bar is just a final adjustment in my book, the spring rate and damper settings have to take priority then adjust with the bar. If still on std dampers/springs then the bar may be too stiff for the setup? How is the engine upgrade coming along ? Mike Engine upgrade, you mean remainder of X51 kit? If so brain kicked in and said why you spending so much money for 10-15BHP at which point I though mmmm a lot of money for a small increase. So spent the money on tyres and other stuff.

majordad said: Reading the above I might consider swapping a7 GT2 rear bar for the one on my 7GT3, anyone wtb my 7gt3 bar cheap ? PM me. gibbo if he is wanting a smaller one what diff set up do you have gibbo? some details on this and what front bar you had fitted would be nice. Edited by fioran0 on Monday 7th January 15:23

aarrgghh, you beat my edit: what diff and front bar have you got on the car with the 997.2 rear one?

fioran0 said: aarrgghh, you beat my edit: what diff and front bar have you got on the car with the 997.2 rear one? Got 997.2 front on softest, though the front bar did not change from 997.1 I am told. I love the front, its great, but with rear 997.2 bar its too oversteer in wet. On a dry track day I did the car was almost perfect. Like Mike says if I had GT3 springs/dampers I'd be OK, but I do not, so I need a rear bar not quite as stiff. Car has no diff, its just regular open diff Carrera has. I've thought about a diff due to the extra traction they give, especially in the wet, but at the same time having a diff will also spin you around quicker when the back-end lets go compared to an open-diff car, not sure if true though.

fioran0 said: But springs/shock settings and sway bars are controlling different things? Spring and shock settings are primarily concerned with wheel control and fore/aft movement while sway bars are primarily concerned with roll and its associated side/side forces. Hi Neil, I agree with what you say but you can't run one with out the other... you are trying to have a roll bar that was designed to work in conjunction with a certain drive line setup, not just the stiffest bar will do. If the dampers/spring rates are not firm enough then you end up with all sorts of geometry related issues running a stiff bar. If loaded up on one side quickly it will jerk the other side up a lot faster if on std spring/damper rates.... Best option is to get stiffer springs and adjustable dampers. mike

the diff question was simply to establish your baseline as it related to the cars balance. without a diff you will have much less natural push than a 997 GT3 (even allowing for their weak diff). a fast dry setup will not be a good wet setup and a good wet setup will leave a bunch on the table in terms of dry. if you only run road tyres and want a compromised dry/wet dual setup then it should be achievable however one has to accept the limitations that will be present in each condition. be careful of just chasing your trail round and round. it may be time to sit down and think through logically what you want to achieve going forward with the car and your expectations for it. if you dont you just end up shelling out a ton of money and get nowhere. having a well balanced and rewarding car doesnt always require changing a ton of bits either. just a methodical approach. Edited by fioran0 on Monday 7th January 16:08

fioran0 said: the diff question was simply to establish your baseline as it related to the cars balance. without a diff you will have much less natural push than a 997 GT3 (even allowing for their weak diff). a fast dry setup will not be a good wet setup and a good wet setup will leave a bunch on the table in terms of dry. if you only run road tyres and want a compromised dry/wet dual setup then it should be achievable however one has to accept the limitations that will be present in each condition. be careful of just chasing your trail round and round. it may be time to sit down and think through logically what you want to achieve going forward with the car and your expectations for it. if you dont you just end up shelling out a ton of money and get nowhere. having a well balanced and rewarding car doesnt always require changing a ton of bits either. just a methodical approach. Edited by fioran0 on Monday 7th January 16:08 I found this out! Fitted GT2 bar end of Summer, car felt ace on hot dry days, did a track day etc. etc. Car was very neutral, no push at all. Then it rained and I was witnessing oversteer even at corner entry, quite frightening experience infact. With the C2S bar on I have lots of push in the wet and overall the car does drive very nice, very managable as the push can be turned into power oversteer. I can only try and next on the list is 997.1 GT3 bar probably on middle setting as I think if I read right, the GT2 bar is 30% stiffer than the gen1 GT3 bar even when the gen1 bar is set to full stiff? If GT3 bar don't do the trick then I can try the 22.5mm x 3.5mm C4 bar. I might just end up back at square 1 with the C2S bar back on but as these bars cost sub £200 from OPC I don't mind giving a couple more a try. Mike who knows, I might end up changing the entire suspension, shall see how it goes. I've just booked 3rd February (Sunday) at Donnington, you coming?

Gibbo - can you remember the part number for your (current) anti roll bar? I think I need to check what's in mine!

MadMark911 said: Gibbo - can you remember the part number for your (current) anti roll bar? I think I need to check what's in mine! I think the 997.2 GT3 bar aka GT2 bar is:- ARB: 997.333.701.94 Bushes 2 x 997.333.792.94 If you've got the gen1 bar, be happy to swap.

Gibbo205 said: I found this out! Fitted GT2 bar end of Summer, car felt ace on hot dry days, did a track day etc. etc. Car was very neutral, no push at all. Then it rained and I was witnessing oversteer even at corner entry, quite frightening experience infact. With the C2S bar on I have lots of push in the wet and overall the car does drive very nice, very managable as the push can be turned into power oversteer. I can only try and next on the list is 997.1 GT3 bar probably on middle setting as I think if I read right, the GT2 bar is 30% stiffer than the gen1 GT3 bar even when the gen1 bar is set to full stiff? If GT3 bar don't do the trick then I can try the 22.5mm x 3.5mm C4 bar. I might just end up back at square 1 with the C2S bar back on but as these bars cost sub £200 from OPC I don't mind giving a couple more a try. Mike who knows, I might end up changing the entire suspension, shall see how it goes. I've just booked 3rd February (Sunday) at Donnington, you coming? Who is the track day organiser ?

sportsandclassic said: Who is the track day organiser ? Javelin Mike

fioran0 said: hey mike, as with many things on a car, theres interplay at work but you absolutely can run one without the other. the shocks/springs and sway bars are there for different reasons. this is why the 996 cup runs the same sway bar as the 996 gt3 despite having springs 6 times harder. a soft spring/hard sway combo is not only a valid setup but often a better setup for a driver/car, especially one who is new to track and not carrying a ton of speed yet. you can tune the car without giving up grip (which you would lose with a harder spring). the role of the spring and shock is to work together to keep the tyre on the ground both in compression and rebound. as such you need a rate that is matched to the forces the wheel sees as it hits bumps etc. use a rate thats either too hard or too soft and you give up grip and feel. as speed increases, the amount of force the wheel sees increases and a harder spring is needed to keep the wheels under control and in contact with the ground. the sway bar is then used to control sideways forces. the most common mistake made on suspension setup is throwing more spring at a car by default or at a problem that doesnt need a spring solution. this is why many people with a big investment in suspension parts see no improvement, or end up just chasing their tails round and round. while everyone can benefit from the qualities of a better shock, one only needs a spring rate change if the current rate can no longer control the wheel itself. while a harder spring obviously resists bodyroll, this is only as a secondary characteristic. using a spring in this situation helps the bodyroll but removes the ability of the car to keep tyre contact. since the only thing on the car trying to keep tyre contact is the spring/shock you give up all your grip by changing spring rate to solve something thats not its problem. in gibbos case, he doesnt mention anything that suggests he it outwith the range of the current spring yet (though it will likely come if he continues to track). as such he is correct in addressing the nature of the car via adjustable sway bars. he should also ensure his geo is correct so that he is maximising use of the tyres width. without a diff his car will be seeing much less natural push than a gt3 and this likely explains the results of the larger rear bar. if it were me, id leave the big bar and fit a diff interestingly the spring rates for the C2S and the GT3 are very similar. identical front and 10N/mm difference at the rear. Hi m8 Your writings is what I've found, I am happy with the spring rates on my car, it is 80% road use and as such it needs an element of softness for our UK roads, so for the roads I find it nearly spot on, dampening could be better which Porsche did indeed improve on 997.2 cars but I do preferre the rawer feel of the 997.1 What was for sure when I did the trackday with the uprated bars in they really cured the body roll, the car was completely flat, so roll bar tuning by itself does certainly work like you say. I just need a less stiffer rear bar, or keep the GT2 bar and get a diff like you say. I shall try either a C4 (22.5 x 3.5mm) or a gen1 GT3 bar and see how it feels on both road and track, at £150ish and 10 minutes to fit its very little expense. I've managed to get some Pirelli Corsa N1 tyres too, which a GT3 owner took of his brand new GT3, so can't wait to test them on track as heard great things about those, nearly CUP dry levels grip but a far better road/wet tyre than the Michelin CUP. Shall play with a different bar to see if it gets the result I want. Out of curiosity what diff can I buy for a Carrera, Porsche have the sport DIFF which was an option on Carreras and its pretty cheap, is it any good? Otherwise I've seen carbon diffs get raved about which are approx $1100, so about £800 landed in UK plus fitting. Is there a UK favourite diff wise or is the Porsche o.e. one OK? If I got a diff there is only one man I'd have fit it, which is Mike as I know how much he loves diffs/gear boxes, everytime I've been to his place he is messing with his GT3's diff/gearbox in someway.

mike will know more on what diff will work in the 997 C2 box. its made by aisin and ive no idea. the 996 C2 box can take the cup or GT3 diff, it just fits right in. if that works on the 997 box then thats your answer right there.

sportsandclassic said: Hi Neil, I agree with what you say but you can't run one with out the other... you are trying to have a roll bar that was designed to work in conjunction with a certain drive line setup, not just the stiffest bar will do. If the dampers/spring rates are not firm enough then you end up with all sorts of geometry related issues running a stiff bar. If loaded up on one side quickly it will jerk the other side up a lot faster if on std spring/damper rates.... Best option is to get stiffer springs and adjustable dampers. mike hey mike, as with many things on a car, theres interplay at work but you absolutely can run one without the other. the shocks/springs and sway bars are there for different reasons and responding to different things. this is why the 996 cup runs the same sway bar as the 996 gt3 despite having springs 6 times harder. the wheel forces the Cup sees are significantly greater (hence spring) while the actual weight of the body roughly the same (so same bar) a soft spring/hard sway combo is not only a valid setup but often a better setup for a driver/car, especially one who is new to track and not carrying a ton of speed yet. you can tune the car without giving up grip (which you would lose with a harder spring). the role of the spring and shock is to work together to keep the tyre on the ground both in compression and rebound. as such you need a rate that is matched to the forces the wheel sees as it hits bumps etc. use a rate thats either too hard or too soft and you give up grip and feel. as speed increases, the amount of force the wheel sees increases and a harder spring is needed to keep the wheels under control and in contact with the ground. the sway bar is used to control sideways movement on the chassis (which in simplistic terms are related to the weight of the car) the most common mistake made on suspension setup is throwing more spring at a car by default or at a problem that doesnt need a spring solution. this is why many people with a big investment in suspension parts see no improvement, or end up just chasing their tails round and round. while everyone can benefit from the qualities of a better shock, one only needs a spring rate change if the current rate can no longer control the wheel itself. while a harder spring obviously resists bodyroll, this is only as a secondary characteristic. using a spring in this situation helps the bodyroll but removes the ability of the car to keep tyre contact. since the only thing on the car trying to keep tyre contact is the spring/shock you give up all your grip by changing spring rate to solve something thats not its problem. in gibbos case, he doesnt mention anything that suggests he it outwith the range of the current spring yet (though it will likely come if he continues to track). as such he is correct in addressing the nature of the car via adjustable sway bars. he should also ensure his geo is correct so that he is maximising use of the tyres width. without a diff his car will be seeing much less natural push than a gt3 and this likely explains the results of the larger rear bar. if it were me, id leave the big bar and fit a diff interestingly the spring rates for the C2S and the GT3 are very similar. identical front and 10N/mm difference at the rear. edited: to add a bit more clarity Edited by fioran0 on Tuesday 8th January 10:58

fioran0 said: mike will know more on what diff will work in the 997 C2 box. its made by aisin and ive no idea. the 996 C2 box can take the cup or GT3 diff, it just fits right in. if that works on the 997 box then thats your answer right there. Fingers crossed then! Apart from the additional push a DIFF gives, any other dis-advantages? I heard from some that the added traction can come as a dis-advantage as in a back-end out moment the diff can actually cause the car to spin a lot quicker and be harder to control. Would fitting a GT3 or any diff effect the PSM, I suspect not as PSM operates on detecting a percentage of slip so that should be no different.

Gibbo205 said: Fingers crossed then! Apart from the additional push a DIFF gives, any other dis-advantages? I heard from some that the added traction can come as a dis-advantage as in a back-end out moment the diff can actually cause the car to spin a lot quicker and be harder to control. Would fitting a GT3 or any diff effect the PSM, I suspect not as PSM operates on detecting a percentage of slip so that should be no different. I'll check my roll bar part numbers this weekend and let you know what's on - but as I've debated the stiffer rear anyway - a swap sounds good! In terms of the downsides, you can get a little extra "push on" if you add more power when the front end is already running wide. However, if you're too brutal with the throttle the diff will light up both rears and if you're cornering when doing this, the rear can slide promptly, particularly on sticky tyres. On the positive side, I've found that the diff makes it easier to control the tail when it steps out. Holding the throttle steady helps hold the attitude of the car to make it more predictable and will help straighten it up when the tyres gain traction. A slight lift or gettting out of the throttle when it's sliding actually pulls the tail back as the diff locks tighter on the overrun. You can actually feel the improved traction when you gun it out of a junction, particularly a T-junction (and the 911 is already very good in this respect) because you're not losing power to one spinning wheel.

If a chasis is well set up with a decent balance it should display the same balance in the dry or wet. The relationship between the anti roll bars should not change. I have been in several races on slicks that have started dry and ended wet or on wets in races that have ended dry. In each occasion the fundamental balance in the car did not change only the levels of grip so I was always a simple case of changing driving style and driving to threshold at all times.

Steve Rance said: If a chasis is well set up with a decent balance it should display the same balance in the dry or wet. The relationship between the anti roll bars should not change. I have been in several races on slicks that have started dry and ended wet or on wets in races that have ended dry. In each occasion the fundamental balance in the car did not change only the levels of grip so I was always a simple case of changing driving style and driving to threshold at all times. This is how car feels right now with C2S bar in rear, push in both wet and dry conditions which is easy to control and turn into power oversteer with more loud pedal. When GT2 bar was fitted on softest, in dry car was neutral with a hint of oversteer. But in wet that oversteer was amplified more so and took a lot of confidence out the car. Bar simply to stiff for my setup.

Hi Gent I'm trying to up grade my rear sway bar on my 997.1 GT3 to a GT2 bar. The part number I've quoted my local OPC is 997.333.701.94 or 96. My OPC confirm that either number refers to the same part but because my GT3 had PASM it already has this part. This doesn't stack up with me as all 977 GT3 have PASM and the sway bar was an up grade on the gen 2 cars. Can anyone confirm what part number I need? PS Gibbo you still looking for a trade? Jon

you need 96. the original smaller bars fitted were 92 though as a result of supersession only 96 (the GT2,997.2GT3 bar) can now be ordered as a replacement. this is where your parts guy is getting confused. 96 is the only part listed for your car but this is not what was originally fitted and caused the problems.

Which measurement does the " x2.6mm" in the original post refer to?

fioran0 said: you need 96. the original smaller bars fitted were 92 though as a result of supersession only 96 (the GT2,997.2GT3 bar) can now be ordered as a replacement. this is where your parts guy is getting confused. 96 is the only part listed for your car but this is not what was originally fitted and caused the problems. Thanks that clears it up.

Output Flange said: Which measurement does the " x2.6mm" in the original post refer to? Its the wall thickness of the tube the arb is made from. you never would, but if you cut it in half you could measure it with a vernier to get the wall thickness

BIG GT2 said: Its the wall thickness of the tube the arb is made from. you never would, but if you cut it in half you could measure it with a vernier to get the wall thickness

Cunno said: Hi Gent I'm trying to up grade my rear sway bar on my 997.1 GT3 to a GT2 bar. The part number I've quoted my local OPC is 997.333.701.94 or 96. My OPC confirm that either number refers to the same part but because my GT3 had PASM it already has this part. This doesn't stack up with me as all 977 GT3 have PASM and the sway bar was an up grade on the gen 2 cars. Can anyone confirm what part number I need? PS Gibbo you still looking for a trade? Jon Holding onto it for the moment, just in case I ever fit an LSD as then I'd need it again. You need to order:- 1x 997.333.701.96 approx £250 2x 997.333.792.92 approx £25 for the pair. Another great thing you gen1 GT3 guys should try is the gen2 shifter 997.424.010.91 with metal bushes, gives a more precise shifting feel. Edited by Gibbo205 on Tuesday 15th January 21:23

Gibbo205 said: Another great thing you gen1 GT3 guys should try is the gen2 shifter 997.424.010.91 with metal bushes, gives a more precise shifting feel. +1 also add cup shifter cables & bingo!

Hi, just thought i would ask the question , I have a 997 gen 1 cab with pasm I am going to replace the drop links and the anti roll bars soon is it worth upgrading ( stiffening it up a bit ) while i have the job to do . Not really a track man anymore , possibly something to do with completely spinning my 3.2 Carrera on the Nürburgring ring a few years ago.lol