Wider fronts only?

I have a 987.2 Boxster S manual with stock 19" 235/265 setup. The car gets tracked as much as possible, 5-10 times in a summer, but being fun takes priority over lap times as I only compete against my own. The car understeers on power, track corner exits suffering the most. With the stock power, gearing and PSM off, overcoming the 265 rears still requires considerable lateral load. I would like the ability to rotate the car more on throttle both on track and twisties. Has anyone tried stepping up the front tire width from 235 to 245 while keeping the rear as 265? I see a lot of people sizing up front and rear in search for more grip, but I would like to chill with adding rear width until power mods require it. I'm running Goodyear Eagle F1 SuperSports and the next set will be Michelin Cup2. I have maxed out the stock camber in front and rear and will be trying out front camber plate efficiency (2.5deg) before deciding on new front tire width.

You might look at the new RE71RS as a competitor to the Michelin Cup2. This tire just became available in the US this spring. I have a set of 255/35/18 f and 275/35/18 r. They match up very well. The car simply needs a little more hp. I still can rotate the car with these tires though. I do have a Wavetrac LSD to help transfer power to the outside tire. These tires are completely different than the older model. Suited to track work as well as street. They are outstanding in the wet as well.

The car doesn't have TPMS so I figured the new Connect feature from the cup2 would help me learn quite a bit about tire behaviour on track. I know they are not the best for lap times Thanks for the suggestion though! I've been thinking of getting a Wavetrac as well. The thing keeping me on the edge is the fun factor of a plate locking diff vs a torsen. I know you can do elevens and drifts with a torsen as well but I wonder if the stability takes away from the fun... Wavetrac should pair up well with the braking differential system in our cars, as a lifting wheel should be automatically braked, in addition to Wavetrac's own locking wave... It would be awesome to get to test these back to back somewhere.

Roksi- Here is the comparison link between Michelin Cup 2 and Bridgestone RE71RS for use on the street and some track duty. https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwjhp6q75e_7AhUTOH0KHbBCCNcQFnoECBEQAQ&url=https://tirewheelguide.com/tires/compare/michelin-pilot-sport-cup-2/bridgestone-potenza-re-71rs/&usg=AOvVaw0w9_JfZaZBioi4pdgMvvNQ You can google the web site directly tirewheelguide.com. The Wavetrac is a ATB LSD, which means it has a slide wave that moves depending on the thrust difference between the two axles. The uses I think are very important is the ability to nail the throttle just a split second before the apex. This system allows additional thrust to be delivered to the outside tire from the inside one, but not totally in a lock up mode. That means not as much understeer out of the corner. It also works in braking to stabilize the rear preventing rear wobble and smooth trailbraking without any rear tire snap oversteer. Most track guys say the Wavetrac is not as dynamic as the clutch style LSD. It does not totally lock up. I find it very useful for both the street and track for exactly that reason.

You can do that except that you said you maxed out stock camber. I assume you mean negative camber....so that is a variable that it might rub if you go taller and wider with same wheels and offset. Otherwise it should be fine. With that said, I wonder about your air pressures. If they are too high, you will reduce your contact patch. What pressures do you run cold and do you adjust when hot? The Michelin Supersports, CS4 and Goodyear F1 are assymetrical tires with an outer third that is just for that, for cornering and usually the inside part is for rain and actually even different rubber compounds. If you negative camber is too extreme and your car is flat, you could be a heavier load on the inside of the tire than what it could handle on the outer third. Do you take temperature readings on the tires to see if they are significantly hotter on the inside than outside? I think 10-15 degrees hotter on the inside is ok but that would help you determine if the tire is getting even use on the track. If no temperature readings, is it greatly worn on the inside? Racecars with slicks have a consistent surface but as I mentioned modern street tires have thread blocks and rubber compounds used for different purposes. So using cups2 will probably help you more than increasing size, but even then, you should find the optimal hot tire pressures and optimal amount of negative camber. Post what pressures you run and chances are someone here might give you a good temp to try and maybe even a camber setting that works well.

I’m mostly worried that the 245 front with 265 rear still isn’t enough to counter the plow on throttle. @Apex1 do you drive on track or just autocross? How is the corner exit understeer with 255 fronts and 275 rears? I imagine the balance with my suggested setup could ve similar. @InigoMontoya 987 maximum negative camber stock is only one degree, which makes the fronts wear on the outer shoulder. Thus trying to solve the issue with camber plates first. The Goodyear Eagle F1 range goes beyond the Asymmetric model. They have equivalents up to Michelin Cup 2 R under that name. The SuperSport is like PS4S with bit more feel due to harder sidewall. I set hot tire pressures at the track to a few PSI under the door card, exactly how many depends on track temperature, and I measure and fix them again until I feel them settle.

I do not like the Porsche understeer. The Tarett GT adjustable sway bars are set up to remove the understeer with the available tire foot print of the 255/35/18 f and 275/35/18 r. I use -2.8 degree camber f and -2.5 degree r achieved by OEM and Tarett Cup Race LCA's. I have not had the oppertunity ot test this set of tires on the track, only autocross. However, in autocross we have 180 degree corners. slaloms and other features to bring out the inherent Porsche understeer. Also keep in mind that I have a mechanical LSD that adds understeer. So to remove understeer, the wider wheel/tire setup and the Tarett GT swaybars really need to do their job to achieve a neutral balance. This balance really allows me to put maximum throttle into the corners much earlier, which means better exit speed down the straights. My camber allows more flat tire patch meeting the road, booth front and rear. Hoosier A7 is another tire/wheel setup I use, requires -3.0 negative camber f to prevent tire rollover, So, I try to stay close to that recommendation. The RE71RS tire walls are much stiffer than the Hoosier A7, so I think more camber in front the better. The only penalty I pay is inner tire shoulder wear. But from the old set of RE71R's that I receently removed, the inner shoulder and outer shoulders wear as even (did flip them once). That is even with 4 minutes toe out each side to increase quick turn in. I think the good tire wear is due to the Tarett Cup LCA's solid bearings, not allowing the suspension to flex.

@Apex1 Would you say the wavetrac adds understeer?

Roksi- The purpose of a LSD is to add more torque to the ground through both tires equally or what the torque slider suggests mechanically. That added push from both rear tires is what causes the additional understeer. This understeer is manageable with a larger tire patch in front and sway bars that change the balance point to place more grip on the front tires The R has a clutch style LSD to add thrust, but the R suspension, swaybars, wheels and tires help manage this additional LSD understeer very nicely. The Wavetrac helps with getting more traction down from the apex, but also helps in the braking process, keeping the car straight and also helps in trail braking. The clutch LSD, certainly does help here as well, but they can lock up too much causing snap oversteer in the braking process.You can order different ramps that affect the clutches braking action. The other issue of clutch style LSD's is the clutch need lubrication that is different than the 6 speed manual Porsche gear box. I use Motul 75-90 gear lube which Wavetrac recommends and is on Porsche transmission/transaxle list. No clutch emulsifiers that Guard would recommend to aid the clutch action though. Come to find out that those emulsifiers can have negative effects on the Porsche synchro's. Not sure why Guard cannot use the same transmission/transaxle lube as the Porsche R uses in their clutch LSD. So, the mechanical LSD adds more thrust to the outside tire and takes away some thrust from the inside slightly unweighted tire. Thats why the slider in the Wavetrac works so well. you do not notice it working, even when you slam the throttle down coming out of the corners. It just manages to give each rear tire enough thrust without causing traction loss. So having tires that have a longer sticking curve through their slip angle (Bridgestone RE71RS) seems to work well without inducing snap oversteer. The limited amount of power produced by the M-97 favors using less slip angles (8-10 degrees) through the corners. This is where a good racing coach can help you set up your car. All these pieces need to work together to get to the "R" suspension working correctly. I did my setup a step at a time over 4 years. But, also I bought modifications that are adjustable as much as possible. Wheels, light weight, correct off set and wide (offset can be changed with wheel spacers). Coilovers. same approach, used Ohlin R&T, after 4 years and 30k miles, no issues (spring rates and valving restriction can be modified). Tarett Cup LCA's that do not have rubber to breakdown and have camber GT3 style shims giving an additional -2.0 degree camber plus the OEM process. Most shops will only go a certain amount of shims though. These shims adds to the overall track width, so be careful with adding track width as your wheels/tires may be pushed out too much and touch the fender lips.

'06 987.1 Boxster S with 18" Michelin 4s 235/265, that I've been tracking, Laguna Seca, Buttonwillow and daily driving. I have been starting at stock 30/37 lbs. pressures then taking out 4 pounds at lunch no matter what the pressures say. (the rights may be higher than the lefts etc) keeping it simple. I'm running Tarett sway bars f/r and adjustable links on the front. My car is handling perfectly neutral so I don't want to screw with much. My shop did change my camber "half street half track" so somewhere in the middle on there brand new 4 wheel alignment machine. My plan is to get an extra set of wheels and a set of 100TW tires like Toyo R888R's ... most of the guys that have been racing for a very long time are running Cup 2's (19"-20" only) or the Toyo's. I feel like this is a safer approach so I don't screw up my balance.

David- Check out the Cup vs Stone comparison. https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwjhp6q75e_7AhUTOH0KHbBCCNcQFnoECBEQAQ&url=https%3A%2F%2Ftirewheelguide.com%2Ftires%2Fcompare%2Fmichelin-pilot-sport-cup-2%2Fbridgestone-potenza-re-71rs%2F&usg=AOvVaw0w9_JfZaZBioi4pdgMvvNQ

Hi Apex1 ... Well I'm always a little leary about opinion polls especially if the people have no track experience. But I would believe your advise. Are the RE71R's track/drive to the track tires ie: "DOT Legal" as opposed to Xtreme street tires? have you tried the Nitto NT01's or the Toyo R888R's as a comparison? thanks

Yes, the RE71RS is certified DOT Legal. That's why I am pushing these tires because I feel they are even better that Michelin Cup 2 tires. Better than my Michelin PS4s. A better overall tire than my Hoosier A7's slicks (that is what you were asking about DOT legal.) The Nitto's and Toyo 888/r;s seem to be a moderate track tire. I find the direction Bridgestone is going fits my needs better especially when looking at the profile of the new RE71RS. At first, I wondered if it would work for me, but I eliminated some competitors due to their wear factor. A052 just were to soft, as I have a set of Hoosier A7's on lite Titian 7 TS5's. So to your question, what if you were presented with new style Nitto NT01 that had better grip yet lasts longer. The same to the Toyo R888R. Sooner than later, you will find side by side comparisons of these tires to the new RE71RS. I believe that the results are coming. A Tirerack full on track test using a higher HP mid engine car like the Cayman would certainly go a long way to showing you what I am talking about. Cayman at some mid length track using your two suggestions as well as the Michelin Cup 2 and the RE71RS. I really can't tell the Tirerack what to test, but in their last test with the BRZ, they left a longer track test open suggesting they may do such a test.

thanks a lot Apex1 that is what I wanted to know, interesting you like the RE71RS better than the Hoosier A7's ! Not sure I'll ever make it up to Washington but it would be fun to get on track with you. If you ever hit a track in Cali make sure you tell me. My Laguna Seca instructor 997 4S, and I do events together last weekend at Buttonwillow his buddy brought a new GT2 RS wooo which he promptly drove off track haha. cheers David

David, I drive my car on the street. The Hoosier are not for every day street driving. I do transit to the track though with them on my car. I've been in rain on my way home from the track going 50 mph and leaving plenty of room for avoidance of standing water. An ugly 40 mile trip. Earlier in the day though they really showed their stuff even though it was raining. The soft rubber was grippy enough to attach to the track better than treaded tires. So for a few runs, I looked like i knew what I was doing. Then it rained harder and my advantage went away. That's the reason I place the RE71RS well above the Hoosier A7. As I use my car in all sorts of weather except for ice,snow and very cold weather. Please read the comparison report in the Tirerack analysis of extreme summer tires. The RE71RS came out on top for their wet drivability but much better in the wear catigory than the A052.