quick tire size question

[fivepointnine]

Im currently running the stock 205/255 17" combo on my 02 Boxster S....Its coming time for new fronts, is it OK to run 225's on the front with the stock rims?

[Topless]

Yes and you will appreciate the improvement in front grip and braking distance. The tradeoff is that the car will hydroplane at a slightly lower speed.

[Idaho Red Rocket 3]

I did it. Love it. Improved straight line handling. Got rid of the front end wiggle.

[fivepointnine]

awesome thanks guys!

[pjS03]

you mean 225/45/17 ? I also have the stock 17's 7 and 8.5, mine are still good. I have the same on the 84 Carrera.

[fivepointnine]

yeah thats the size I was looking at, pretty reasonably priced in that size too

[Mrmaddbrad]

Yeah that seems like what people are running these days.

Can you put 265's on the rear wheels?

[thstone]

Yes, the 225/45/17 on the front is the way to go. This combination of increased width and lower profile maintains the stock tire diameter of 25.0". If the diameter changes, then your speedo will be off and it might affect the ABS system.

Now, let's look at the rear tires:

255/40/17 = 25.0" (stock rear size has same diameter as the fronts)
265/40/17 = 25.3" (too big)
265/35/17 = 24.3" (too small)

To keep the diameter the same, the next matching size tire is a 285/35/17 (= 24.9" which is close enough). However, a 285 is a bit too large for the stock rear rim.

Thus, we are all kind of stuck with the stock rear tire sizing unless you go to aftermarket wheels.

Here is a handy tire size calculator: Tire size calculator

[stephen wilson]

You, or the car, will never notice the .3" difference of a 265 tire. That's only .15" difference in the rolling radius (a touch over an 1/8").

[blue2000s]

You can vary by as much as 5% in diameter and still really be OK.

[thstone]

Sorry, I should have mentioned something about the variance. I was just trying to explain how the 225/40 in the front is an exact fitment where the 265/35 in ther rear is not.

Also, remember that the primary reason to go to 225/45 in the front is to reduce the inherrent understeer. If you also go wider in the rear, then you've mostly negated that benefit.

[Mrmaddbrad]

If you want to start talking about the diameter of wheels, then you should talk about the performance aspect of it. Smaller tires are easier to spin and give you a better gearing ratio for racing. The wideness is also extremely helpful. If it fits (Maybe use 5mm spacers), then i dont see the problem with having 265/35's on the rear.... Stock rim size is just a place to start... I guess you're going to try to tell me that the people that put 19's on their boxsters are ruining everything about the car?

Well sir, you're most definatly wrong about that. Your ABS will only slightly be affected with that small of a change, as will your speedo.... (maybe +/- 1mph at 50mph)....

[Overdrive]

...why ask a question if you were already prepared to answer it for yourself...?

[Mrmaddbrad]

Originally Posted by Overdrive

...why ask a question if you were already prepared to answer it for yourself...?

I'm wondering if they have enough clearance... I was just arguing that overall diameter doesn't matter if it clears all corners. So if anyone has put 265's on there car. Or heck, even 275's, thats what i'm going to run as race tires.

[WhipE350]

Originally Posted by Mrmaddbrad

I'm wondering if they have enough clearance... I was just arguing that overall diameter doesn't matter if it clears all corners. So if anyone has put 265's on there car. Or heck, even 275's, thats what i'm going to run as race tires.

I used the following to figure out spacing and clearance. Wheel Offset Calculator