I have 315-25-19's on the rear and 235's on the front. I want to go a bit wider on the front tires.

What is the correct size? I know it is 255 something................

Tanks in Advance to the Brain Trust

 

Contact Tire Rack...

 

Someone posted it B4 and I am trying to find it.

 

a few guys are running 245 35/19 ( or even 255.35.19 up front) but don't you need compatibility w/ rear tire diameter due to the AWD? you can also try the 1010tires.com tire calculator

 

You can contact Damon at tire rack...
here is the thread which spends a bit of time talking about wheel / tire sizes.
https://rennlist.com/forums/wheel-an...leggerita.html
From my view the 245 45/19 F , 295 30 /19 or (305 30 /19) R would be your best option for track useage. While a few H class guys are running the 255 up front! At that point you will need to roll the fenders.

Please keep in mind that much of this is based on GT3 wheel ofsets... Seeing as you did not mention which offsets you are using.

 

Tim, I'd avoid the 1010 calculator unless you want just a rough estimate. Find the tires you like and check our their specs. Tire rack posts most of the major tires specs. Make sure your diameter is near the same front to back. Not nearly as important to stay at 25" but rather same front to back. So, if you have a tire you like and the diameter in rear is 25.7", try to find the front in that tire that matches up. If they don't make the correct size, MOVE ON! Quickest way to fry your AWD system is to mismatch the diameters.

By the way, what are you running right now that you want to keep the rears?

 

Very good point Dell!

 

Dell, I know. The front diff on my 97 993TT went POW a few weeks after I had it. The tires were incorrect on the front and that might have caused it to blow.

Actually the place I got the Nitto's from is replacing them for me with Toyo's. The Nitto's were flat spotting real bad. The Toyo's I had on my 03TT never had an issue.

315 25 19 (Rear)
SW= 3.1
Rev= 800

255 30 19 (Front)
SW=3.0
Rev=806

So a 255/30 would give me the width AND would be much closer in RPM's.

235 35 19 (Current Front)
SW=3.2
Rev=792

 

That should be perfect! I am guessing you are running the T1R? Those two sized are within .1" of each other.

You were probably flat spotting the NT01 since it is a very soft compound (DOT-R) compared to the performance street tires.

 

Yup. The TR1 is a good tire

 

From previous threads one point has been 235 in the front is good enough since the car oversteers anyway, so you are only adding more drag going higher width. Unless your front is sliding out on you just stick with 235.

Some prefer to stay away from 19" rims on the track going 18 or 17". I road use 19's and they are like riding on rails till the back end brakes loose. But for track with odd curbing met at speed or grass and gravel to be dived into the 18 or 17" option probably is best. You don't mention track but just in case you lean that way. Also,....... ah forget it

I am not certain if the 25 profile of your 315/25/19 rear tires was good. Is that a stock configuration? Some of these fancy handling options starting with ABS to traction controls I wouldn't trust for dealing your car an easy time if the circumfrences of wheel and tires don't add up right for the computer. I hope thats not what cause the front gearing failure.

 

In the first place, what is your front wheel width?

 

yep, first question to ask.

Tim, my C4S had 235/35/19 on 19x8.5 front

 

Well, I am not sure what the width on the front TechArts is at the moment. It is at the shop at the moment so I will look when it gets back. Now the fronts with the Nitto's LOOKED like the tire was not wide enough. The sidewall was slanted in and the rim guard was not protruding as it did properly in the rear.

PLUS the fact that the 255 is closer to the rears in height and rotation is much better.

I did a little looking and the stock tires are as such:

225-40-18 (front)
SW Height-3.5
RPM-804

295-30-18
SW Height-3.5
RPM-809

19in Tires

255 30 19 (Front)
SW=3.0
Rev=806

315 25 19 (Rear)
SW= 3.1
Rev= 800

So as I see it there might be a slight variation in the Speedo. But it is almost dead nuts on with regards to the front to rear differences in stock vs. non-stock.

SW is off by .1 and RPM is off by 6 where as the stock SW is even and the RPM is off by 5.

 

I just looked up the rpms for the 315/25/19 and it was more like 825, not 800 ( on 1010tires)


this is what I wrote before checking the #'s: Tim, your current rears are way taller, that's why they only make 800 rpm vs the 809 on the stock 18's. for the fronts, no prob 804 vs 806. therefore 806/804 =1.0024 faster. Rears otoh, 800/809
= .9888 slower.

either way, your new fronts are faster than OEM and your rears are slower than OEM.

to me, the ratios are reversed, in a bad way...