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Max Front Tire Diameter (986)

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Old 02-15-2018, 03:21 PM
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thegiant24
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Default Max Front Tire Diameter (986)

Hey guys, I’m looking at plus sizing the front tires on my 99 Boxster from the stock 205/50R17 25.1” diameter to a 235/45R17 25.3” diameter. My question is regarding the extra couple of tenths in diameter up front. Will this cause any rubbing or ABS issues?

Im stuck on the 235/45R17 because I get a hook up on Contis and the ExtremeContact Sport doesn’t come in a 235/40R17.

The car is a base model without any TCS.

Thanks in advance!
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Old 02-15-2018, 06:55 PM
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2RedPorsche
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I ran 225/45R17 front with 255/40R17 rear with no problems before changing to 18s on my 986. I can't say what the 235s would do, it does leave you with about a 3% difference between front and rear outside diameter. I'm not sure if that's too much though. I'm not really sure what you meant about being stuck on 235 Contis but then said they don't make that size? I'd consider the 225s if you can get them.
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Old 02-15-2018, 07:01 PM
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thegiant24
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Thanks for the response! I can get 225/45R17 as well, I just wanted to put the widest tire I could fit on the front wheel. sounds like I should just stick with the 225.

Originally Posted by 2RedPorsche View Post
I ran 225/45R17 front with 255/40R17 rear with no problems before changing to 18s on my 986. I can't say what the 235s would do, it does leave you with about a 3% difference between front and rear outside diameter. I'm not sure if that's too much though. I'm not really sure what you meant about being stuck on 235 Contis but then said they don't make that size? I'd consider the 225s if you can get them.
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Old 02-17-2018, 12:28 PM
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The Radium King
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235 on the front are great. from what i’ve read, you want max 4% diameter difference between front and rear so as to not confuse the abs.
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Old 02-24-2018, 07:04 PM
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I have the exact Conti tires with 235 front, 255 rear on 17x8.5" rims front and rear and love them. No issues what so ever with tire rubbing or ABS, had to spacer the front wheel 5mm due to a wheel weight skimming the lock collar on my PSS9 shock. Before I put the PSS9s on I noticed the bottom of the stock struts spring perch just clears the top of the tire by about 10mm. My car has a good deal of negative camber(-2.6, -2.3) and is corner balanced, this tire set up has kept the car very neutral at track speeds. If your not tracking the car the 225 up front will be more then fine, prob just fine on track too. Tires have done 6000k miles with 10 hard track days and have 85% remaining up front and 70% in rear. Great in the rain too!
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