Board: Porsche - 911 - 996 - Turbo Language: English Region: Worldwide Share/Save/Bookmark Close

Forum - Thread

    Wider Tires

    I have been interested in installing wider rubber for awhile now on my 2001 996tt. Availability of larger tires that are compatible is not good. I found the other day what I believe to be a good match but would require some slight fender work (widening the fenders just a little which I would do all in metal, undetectable to the naked eye). Michelin in the Pilot Series makes a 335/30ZR18 and a 255/40ZR18. The 335's have an outside diameter of 26.1" and the 255's have an outside diameter of 25.9". Changing the outside rims on my present three piece Fikse FM/10's would be fairly easy. I already have a spread inside due to the GT3R brakes. The JRZ triple adjustable race suspension would be easy to adjust. I have already modified the gears, so my current top end @ 7000 rpm's is 185 mph. These tires would raise the top end to about 193 mph and the new motor we are building with a 8000 rpm red line will raise the top end to about 210 with these tires.

    Any input as to how this should affect handling?

    Re: Wider Tires

    One small caution! My experience with 993TT car at very high speed is this: above 330 kph the ABS does not function! The warning light will flash.Actually my whole panel lights up when we exceed that speed. Ruf says the ABS function will return when the speed drops below 330 kph. We have done very hard braking from 330 kph without incident however the panel lighting up is a major distraction.
    Hey bring that bad boy to the Silver State. You got a roll cage yet?

    Re: Wider Tires

    Roland, thanks for the heads up on the ABS system. To date the car just won't go that fast. I am not sure even when I'm done if it will see 210 mph or 330 kph. It will be close. The trip to 330 kph will be like catapulting off an aircraft carrier. Time to 185 mph is right at 18 seconds currently. Hopefully by Christmas time we will be done with everything. I have had the car for fourteen months, eleven of those months have been with three different tuners. It has been at S Car Go Racing for the last two weeks. Not scheduled to see it for another two weeks. I don't have a roll cage, but do have a pretty stout roll bar. I really don't want the cage part unless the cage part can be made removable.

    About handling...

    Just remember that you're adding alot of unsprung weight by doing that, so car's handling will suffer a little (but ultimate grip may increase). Also, I have 255s on the front of a 944TS track car and it does tramline pretty badly on the street (follows the grooves in the road).

    Re: About handling...

    Grant, good question. Which set up would handle better?

    Well, with the bigger wheels/tires,the car wouldn't be as

    nimble (able change directions as quickly) or ride as well (the weight of the wheel going up and down would overwhelm the shocks and springs more),but you could probably go around a corner a bit faster. So, I think for the track (or very smooth road), the bigger setup might be better,otherwise, you might prefer the smaller ones.

    Re: Well, with the bigger wheels/tires,the car wouldn't be as

    Grant, the car is presently set up wit JRZ triple adjustable race suspension, monoballs and GT3R sway bars front and rear. Also GT3R brakes 380mm front/350mm rear. Would this set up change your above opinion?

    Re: Wider Tires

    There is no problem with the ABS on the 996 Turbo, even at speeds over 330 kph. We know a guy (he's tuning 993/996 Turbo engines) who drove slightly over 360 kph (speedo reading) in a 996 Turbo and no problems occured. However he said that it was pretty scary (20 kph more seem to mean worlds at that speed) and he didn't trust the tires (which were actually approved up to a top speed of around 350 kph (incl. the "upper margin").

    I don't know, I think cjv is doing the right thing. Building a real power giant and keeping a more "real life" top speed to avoid tire problems.

    CJV- Well you certainly have the suspension to cope w/ it

    Even though you have an awesome suspension, it will still react quicker with less unsprung weight. But it you're looking for maximum grip, you definitely have a suspension that can handle the extra weight if you choose!

    Is there a way you can try some bigger wheel/tires before buying? That would be the way to go - short test-drive...

    Good luck with your sweet ride,


    02 C2 coupe
    88 944TS track car
    73 911S
    03 GT3 on order

    Grant is right

    CJV, it all gets very complicated. If the road is glass smooth and the suspension extra hard then unsprung weight won't be important. But if the road starts getting bumpy then it becomes very important.

    In my own case, there is one corner at Nürburgring which is bumpy at the final braking point and at the apex (Kallenhard). Everyone tends to brake off-line and go around the outside of this corner. Before adding the PCCB's I would do likewise. But now, with the lower unsprung weight of the PCCB's, I am able to brake and corner through the bumps of this corner. Unsprung weight does make a very big difference.

    Wider tyres increase unsprung weight. But they also increase the amount of contact with the road. And wider tyres can also mean a slower turn-in based upon the geometry of the contact patch (which is what Grant is talking about). Going wider has deminishing returns and could have costs in terms of the flexability of the car.

    And let's also remember that the size of the tyres is one of the biggest factors in the aerodynamic area of the car. So increased drag with wider tyres (the C4 vs. C4S shows this well).

    The only way to answer your question on how wide to go if you want to go that route is to experiement.

    But if I were you CJ, given the number of miles you are travelling each year, I would be looking not for wider tyres but for stickier tyres. I would look to using Pirelli Corsa, Michelin Cup or similar. Sure they won't last as long but do you care? If you have to contend with rain then I'd look for some sticky wet weather "R" tyres on a second set or rims. Or alternatively you could use standard tyres for the rain (and believe me, width is not an advantage in the rain) and some really nice "R" compound tyres for those beautifully sunny days.

    Barely street legal "R" compound tyres are just going to blow your mind so far as braking, turn-in, cornering, etc. are concerned. There's no comparison to regular street tyres no matter how wide they are.


    Fixed Wing -Please tell me more about the PCCB's

    I have ordered a new GT3 and will have to decide whether to buy these or the more conventional brakes. Some people have said that they didn't care for them, but I've also heard that they have improved them since their introduction.

    I'd love to hear a review from you!


    Grant: check email.

    Re: Grant is right

    FixedWing, Pirelli makes two sizes in the P Zero Corsa that would be compatible. For the fronts the 235/18's and the rear 295/18's and 315/18's. I am currently running the Fikse FM/10's. They are 8.5" wide in the front and 11.5" wide in the rear. Which rear tire do you believe would be best.


    If the AWD is still hooked up then I personally would go with the 295/18 Corsa at the rear. My reasoning would be that I prefer a more neutral handling car and I think a sticky 295 is more than enough. If you go with the 315's with the 235's at the front then I suspect that you will maintain, or maybe even make worse, the understeer on the Turbo.

    If you prefer an understeering car then you might want to go for 315's. Also, this could be a good choice if you've disconnected the AWD (a la GT2).

    With Sticky Corsas and AWD you will have absolutely no trouble getting the power down. If anything, you might have to be a little more careful about breaking things as these tyres just aren't going to slip the way a street tyre would if you do a high RPM standing start.

    Just lately, people prefer the Michelin Cup tyres to the Pirelli Corsas but I think you will have trouble getting the sizes that you need. That might change 1Q2003. But either of these is going to give you a much more solid car in the dry. Not only will it handle a lot better but that handling will be a lot more dependable (by this I mean that when the car takes set in a corner it will just stick -- you won't find yourself constantly having to catch the back and make little adjustments mid-corner). For this reason, I think a car with a little less understeer would be acceptable -- and for me, even preferable.

    Does this help?


    Re: tt996 at 360!?

    This may seem silly/trivial, but how much tuning is required to get the car up to that level of performance?... Is this a Gemballa job? I am looking for tuners in the USA (New York city area)... and was interested (not that I intend to take the car up to that high a speed around here).



    Board Subject Last post Rating Views Replies
    Porsche Sticky SUN'S LAST RUN TO WILSON, WY - 991 C2S CAB LIFE, END OF AN ERA (Part II) 5/15/24 8:44 AM
    819614 1808
    Porsche Sticky Welcome to Rennteam: Cars and Coffee... (photos) 4/7/24 11:48 AM
    Boxster Coupe GTS
    455503 565
    Porsche Sticky OFFICIAL: Porsche 911 (992) GT3 RS - 2022 3/12/24 8:28 AM
    277959 323
    Porsche Sticky The new Macan: the first all-electric SUV from Porsche 1/30/24 9:18 AM
    93730 45
    Porsche Sticky OFFICIAL: Taycan 2024 Facelift 3/15/24 1:23 PM
    CGX car nut
    11380 50
    Porsche 992 GT3 7/23/23 7:01 PM
    979401 3868
    Porsche The moment I've been waiting for... 2/1/24 7:01 PM
    897411 1364
    Porsche GT4RS 4/21/24 11:50 AM
    413905 1454
    Porsche Welcome to the new Taycan Forum! 2/10/24 4:43 PM
    408012 1526
    Others Tesla 2 the new thread 12/13/23 2:48 PM
    CGX car nut
    395540 2401
    Porsche Red Nipples 991.2 GT3 Touring on tour 5/12/24 6:23 PM
    296337 669
    Porsche Collected my 997 GTS today 10/19/23 7:06 PM
    CGX car nut
    272434 812
    Lambo Huracán EVO STO 7/30/23 6:59 PM
    246108 346
    Others Corvette C8 10/16/23 3:24 PM
    224561 488
    Others Gordon Murray - T.50 11/22/23 10:27 AM
    175519 387
    Motor Sp. 2023 Formula One 12/19/23 5:38 AM
    126144 685
    BMW M 2024 BMW M3 CS Official Now 12/29/23 9:04 AM
    125766 303
    Porsche 2022 992 Safari Model 3/7/24 4:22 PM
    88432 239
    AMG Mercedes-Benz W124 500E aka Porsche typ 2758 2/23/24 10:03 PM
    78088 297
    Porsche 992 GT3 RS 3/3/24 7:22 PM
    57555 314
    Motor Sp. Porsche 963 5/18/24 9:44 PM
    29805 249
    Ferrari Ferrari 296 GTB (830PS, Hybrid V6) 1/21/24 4:29 PM
    23631 103
    BMW M 2022 BMW M5 CS 4/8/24 1:43 PM
    22505 140
    AMG G63 sold out 9/15/23 7:38 PM
    18354 120
    AMG [2022] Mercedes-AMG SL 4/23/24 1:24 PM
    17777 225
    Porsche Porsche Mission X Hypercar 12/3/23 8:52 AM
    12877 63
    Porsche 911 S/T 10/10/23 8:53 AM
    11526 55
    Motor Sp. Formula 1 2024!! 6/15/24 11:25 AM
    10482 217
    Others Tesla thread N°3 5/1/24 11:09 PM
    CGX car nut
    10461 93
    Porsche Macan EV 1/25/24 9:10 AM
    9545 28
    102 items found, displaying 1 to 30.