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YOUR RESEARCHMax tire size on 9x18 rear wheel - 986 Forum - The Community for Porsche Boxster & Cayman Owners
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Run 315-35-17
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heck, many cobra guys ran a 315-35-17 on a 17x9 inch rim until the aftermarket companies made replicas to 17x10.5
Max tire size on 9x18 rear wheel - 986 Forum - The Community for Porsche Boxster & Cayman Owners
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Leading evidence: 'Run 315-35-17' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Recommend best size' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Suggestion
There is the recommended best size and then there's everything else
Max tire size on 9x18 rear wheel - 986 Forum - The Community for Porsche Boxster & Cayman Owners
Recommend psi
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Max tire size on 9x18 rear wheel - 986 Forum - The Community for Porsche Boxster & Cayman Owners
Recommend size
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Suggestion
265 is stretching the the recommended size for a 9" rim.
Max tire size on 9x18 rear wheel - 986 Forum - The Community for Porsche Boxster & Cayman Owners
Recommend size, not what you can get fit
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Suggestion
I said the recommended size, not what you can get fit on a rim.
Max tire size on 9x18 rear wheel - 986 Forum - The Community for Porsche Boxster & Cayman Owners
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By this picture it looks like your under inflating the tire and still not getting full contact of the tire and it's showing the bow.
Car: 2000 Boxster base
Wheel: 9x18 Turbo twist Porsche Factory Wheels
Rear suspension & camber: Car has stock suspension & camber alignment.
Currently I have 265/35/18 on the rear wheels.
Qn: what is the max tire size I can install in my 9x18 wheel without having to use any spaces, fender rolling, any rubbing and performance issues?.
Tire preference: Michelin Pilot Super Sport tires. Car will be used in both track and street.
Following are some options, let me know what you think:
Michelin Pilot Super Sport 275/35/18
Michelin Pilot Super Sport 285/35/18
Thank you.
Chamilka
I'm not saying 275 won't fit. I would worry about the contact patch not being as good (since it will be putting a bow in the tire) as if you were running a 265 tire.
EDIT: I am curious as to your tread wear using 265's on a 9" rims.
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Do you deflate the tire? How are you getting the tire to get full surface contact? A 275 tire is 10.83 inches wide.
Do you happen to have a close up picture of this combo?
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heck, many cobra guys ran a 315-35-17 on a 17x9 inch rim until the aftermarket companies made replicas to 17x10.5
Not saying you should put such a big tire back there but just because someone says its not ideal does not mean its not possible.
It is too true. I said the recommended size, not what you can get fit on a rim.
Understand this, 9" rim, 275 tire is 10.83 inches wide. That's not a proper combination. Not even close. 265 is stretching the the recommended size for a 9" rim.
Please by all means ignore the tire/wheel site I posted.
This is the wheel I have decided to go with on my Boxster. Notice the rec tire size, from Tire Rack? 265 and that's on a 10" wheel. However I will be going with 275 tires on the rear.
Not attacking just saying. And not correct does not mean it does not work. Just because a 265 will work ideally with a "XX" inch rim does not mean a 275 won't work better even though a 275 may work better with a larger rim. I love the big tire look, but in many cases it just does nothing but deter the performance.
Here is my old car with the big tire. Yes I know today most are into the other direction and like the stretched tire look but I'm old school.
I'm sticking within the recommend size for those wheels. 235 front, 275 rear. This combination gives a better front to rear tire speed rotation too.
The are lots of things to look at when buying tires, way more then how wide a rear tire you can fit on a wheel.
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On the rears I keep pressures at 34 psi. The car does have -3.2 degrees camber and it wears the inside edges. Since these tire are directional, about mid tire life I'll flip the tires on the rims and put them on the other side.
Loss of torque multiplication is the unavoidable downside of running taller than spec rear tires. This is very noticeable on 986's. That leaves a 285/30/18 as the only option along with 10" X 18" wheels. Now the car resists rotating into turns!
I tell you what, the 275/295 combo on the benz sure was undrivable in the snow! Esp since they were summer tires they just floated on top of the snow... lol
And just to re-emphasize, when you have so much camber with a wide tire, and low sidewall, you will get a lot more tire wear than a narrower tire.
This is a source reference. Confirm exact model applicability in the original material.
