Tire width?

[thstone]

Don't forget that changing the tire stagger (the difference between the width of the front tires vs the rear tires) will affect handling.

The 17" stock tire widths (205F/255R = 50mm difference) were selected to ensure that the car would understeer at the limit. Adding more stagger (205F/285R) will typically result in even more understeer (I would expect a 205F/285R car to handle like pig, i.e., terminal understeer).

Most Boxster owners reduce stock stagger to 30mm by running 225F/255R. This reduces understeer and moves the car towards more balanced handling. Many track cars run 235F/255R (20mm stagger) to further reduce understeer. And yes, some track cars run a so-called "square" setup of 255F/255R (zero stagger) to dial out most if not all of the tire width induced understeer (this setup also typically requires some other changes (alignment and sway bar settings) to keep the car from too much oversteer).

So remember, when going wider in the rear to also consider going correspondingly wider in the front to maintain whatever stagger (and handling characteristics) you prefer. This will keep the car's overall handling characteristics relatively constant.

[evan9eleven]

Originally Posted by thstone

Don't forget that changing the tire stagger (the difference between the width of the front tires vs the rear tires) will affect handling.

The 17" stock tire widths (205F/255R = 50mm difference) were selected to ensure that the car would understeer at the limit. Adding more stagger (205F/285R) will typically result in even more understeer (I would expect a 205F/285R car to handle like pig, i.e., terminal understeer).

Most Boxster owners reduce stock stagger to 30mm by running 225F/255R. This reduces understeer and moves the car towards more balanced handling. Many track cars run 235F/255R (20mm stagger) to further reduce understeer. And yes, some track cars run a so-called "square" setup of 255F/255R (zero stagger) to dial out most if not all of the tire induced understeer (this setup also typically requires some other changes (alignment and sway bar settings) to keep the car from too much oversteer).

So remember, when going wider in the rear to also correspondingly go wider in the front to maintain whatever stagger you prefer. This will keep the car's overall handling characteristics relatively constant.

Thanks for the info, I didn't know that about the stagger, so I have learned something useful there.

OEM on the 18" Carrera wheels are 225/40 and 265/35. So 40mm of stagger. Following your advice then, if I go with 275's in the rear I should also upsize the fronts to 235's. Or downsize to 255s in the rear, though I don't know if my desired tires are available in that size over here or in the correct aspect ratio.

[thstone]

Originally Posted by evan9eleven

Thanks for the info, I didn't know that about the stagger, so I have learned something useful there.

OEM on the 18" Carrera wheels are 225/40 and 265/35. So 40mm of stagger. Following your advice then, if I go with 275's in the rear I should also upsize the fronts to 235's. Or downsize to 255s in the rear, though I don't know if my desired tires are available in that size over here or in the correct aspect ratio.

Yes, this can result in a lot of searching for specific tire sizes that may or may not exist. At the end of the day, most of us just do the best we can in balancing all of these tradeoffs.

[Joe B]

On 8" front, 10" rear rims, run the stock sizes. You don't want or need big fat meats on there. I had 235/40 and 275/35, and I went to the stock 225/40 and 265/35 sizes. The car is now more nimble with lighter steering. Also the 235s were rubbing a hole in the front wheel liner when I turned sharply.

[evan9eleven]

Originally Posted by Joe B

On 8" front, 10" rear rims, run the stock sizes. You don't want or need big fat meats on there. I had 235/40 and 275/35, and I went to the stock 225/40 and 265/35 sizes. The car is now more nimble with lighter steering. Also the 235s were rubbing a hole in the front wheel liner when I turned sharply.

Good to know. though as I pointed out we don't have the selection of sizes in Europe like you guys do stateside, so I'm struggling to find what I want. I'd just go stock if that was an option.