wider tires - conventional wisdom?

[David993s]

What is the conventional wisdom regarding going one size wider in tire width on the same wheels? i.e. my 993 has 8" fronts, 10" rears with 225 and 285, respectively, being the correct size for the wheel. Can one generally go one size wider? i.e. can I go 235's and 295's on the same wheels with no problems?

What say you?

Thanks.

[Bill Verburg]

the 285 rear is already wider than oe spec
for 8 & 10 x18 wheels oe is 225/40 and 265/35

Larger tires and wheels can be fitted if the wheels have the correct specs
8ET52 front and 10ET65 rear are oe you can fit 285/30 but will need to massage the fenders at low ride height

in front there is more room but the issue is to keep the rolling radius of the tire close to equal in order to keep the ABS happy, it can live w/ a small disparity but gets more unhappy the greater the differential.

Wider tires can be used, i've seen up to 295/30 x18 on 10s in the back of a track 911, I suspect a lot of massaging was done to get it to work

Ideally you would want 245/35 on 8.5ET54(+/- a tad) fronts and 285/30 on ET65 rear, this is the setup that the factory came up w/ after a lot of testing as best for the 993 Cups.

[David993s]

Originally Posted by Bill Verburg

the 285 rear is already wider than oe spec
for 8 & 10 x18 wheels oe is 225/40 and 265/35

Larger tires and wheels can be fitted if the wheels have the correct specs
8ET52 front and 10ET65 rear are oe you can fit 285/30 but will need to massage the fenders at low ride height

in front there is more room but the issue is to keep the rolling radius of the tire close to equal in order to keep the ABS happy, it can live w/ a small disparity but gets more unhappy the greater the differential.

Wider tires can be used, i've seen up to 295/30 x18 on 10s in the back of a track 911, I suspect a lot of massaging was done to get it to work

Ideally you would want 245/35 on 8.5ET54(+/- a tad) fronts and 285/30 on ET65 rear, this is the setup that the factory came up w/ after a lot of testing as best for the 993 Cups.

Thanks Bill. My 993 S (widebody with hollow spoke technology twist wheels) came from the factory with 225's front and 285's rear as oe spec. Front wheels are 8 x 18 et 52, and rears are 10 x 18 et 40. I checked my door sticker to confirm and that is indeed what it states.

That's why I was thinking one size wider would be no problem on the wheels. However, I have M030 springs so I am wondering about contact with the fender lip on hard cornering. The 225's and 285"s don't have any fender lip contact issues under cornering at DE's.

[Bill Verburg]

Originally Posted by David993s

Thanks Bill. My 993 S (widebody with hollow spoke technology twist wheels) came from the factory with 225's front and 285's rear as oe spec. Front wheels are 8 x 18 et 52, and rears are 10 x 18 et 40. I checked my door sticker to confirm and that is indeed what it states.

That's why I was thinking one size wider would be no problem on the wheels. However, I have M030 springs so I am wondering about contact with the fender lip on hard cornering. The 225's and 285"s don't have any fender lip contact issues under cornering at DE's.

You might have mentioned that
the widebody cam e w/ the same front wheels and tires as the n/b
in back they used either 10ET40 or 10ET65 w/ a 25mm spacer and 285/30 tires

You still need to be concerned w/ tire heights being close to the same front and rear

You can go to 235/40 & 295/30 on the 8 & 10 wheels that you have but no wider

Those tires are at the limit

There is a decreasing performance gain as the tire gets closer to the minimum wheel width, ie for max performance from a given tire use the widest wheel for which it is spec'ed, for max comfort use the narrowest wheel for which the tire is spec'ed

[Kein_Ersatz]

Bill knows of what he speaks ( types) big 993 following on rennlisters and considerable factory spec knowledge and loads of track experience.

Quote de Bill Verburg

the 285 rear is already wider than oe spec

for 8 & 10 x18 wheels oe is 225/40 and 265/35



Larger tires and wheels can be fitted if the wheels have the correct specs

8ET52 front and 10ET65 rear are oe you can fit 285/30 but will need to massage the fenders at low ride height



in front there is more room but the issue is to keep the rolling radius of the tire close to equal in order to keep the ABS happy, it can live w/ a small disparity but gets more unhappy the greater the differential.



Wider tires can be used, i've seen up to 295/30 x18 on 10s in the back of a track 911, I suspect a lot of massaging was done to get it to work



Ideally you would want 245/35 on 8.5ET54(+/- a tad) fronts and 285/30 on ET65 rear, this is the setup that the factory came up w/ after a lot of testing as best for the 993 Cups.

Thanks Bill. My 993 S (widebody with hollow spoke technology twist wheels) came from the factory with 225's front and 285's rear as oe spec. Front wheels are 8 x 18 et 52, and rears are 10 x 18 et 40. I checked my door sticker to confirm and that is indeed what it states.



That's why I was thinking one size wider would be no problem on the wheels. However, I have M030 springs so I am wondering about contact with the fender lip on hard cornering. The 225's and 285"s don't have any fender lip contact issues under cornering at DE's.

[wesleyc]

I have a 993 with mo30 springs and 235 /40/ 18 on front and 275/ 35 /18 on rear. They tend to seem a bit heavier. ( unsprung weight). Wish I would have gone smaller.