Jump to content

Welcome to RennTech.org Community, Guest

There are many great features available to you once you register at RennTech.org
You are free to view posts here, but you must log in to reply to existing posts, or to start your own new topic. Like most online communities, there are costs involved to maintain a site like this - so we encourage our members to donate. All donations go to the costs operating and maintaining this site. We prefer that guests take part in our community and we offer a lot in return to those willing to join our corner of the Porsche world. This site is 99 percent member supported (less than 1 percent comes from advertising) - so please consider an annual donation to keep this site running.

Here are some of the features available - once you register at RennTech.org

  • View Classified Ads
  • DIY Tutorials
  • Porsche TSB Listings (limited)
  • VIN Decoder
  • Special Offers
  • OBD II P-Codes
  • Paint Codes
  • Registry
  • Videos System
  • View Reviews
  • and get rid of this welcome message

It takes just a few minutes to register, and it's FREE

Contributing Members also get these additional benefits:
(you become a Contributing Member by donating money to the operation of this site)

  • No ads - advertisements are removed
  • Access the Contributors Only Forum
  • Contributing Members Only Downloads
  • Send attachments with PMs
  • All image/file storage limits are substantially increased for all Contributing Members
  • Option Codes Lookup
  • VIN Option Lookups (limited)

Tire Size Help requested...

TurboLove

By TurboLove
in 996 TT, 996 TT S, 996 GT2

 Share

Recommended Posts

TurboLove Member

TurboLove

Posted
Posted

I asked this question on another board and wanted to get some expert advice.

I just put on Michelin PS2s 235 40/18 in front and 295 30/18 in the rear....will keeping 235s in the front and 295s in the rear hurt my car? (since the stock fronts were 225s)

Someone made the below comment and recommended I go with 315/ 30/18 for the rear:

"Yeah, it's going to mess up your differential.

The front diameter is too large for the rear diameter. As a result, the differential is going to try and "compensate" for it which is going to work it overtime.

There's a certain "range" where a little size variation is allowed. However, the 235/295 combo is out of that range."

Need I be concerned???

wross996TT Member

wross996TT

Posted
Posted

comparison (theoretical)

Specification Sidewall Radius Diameter Circumference Revs/Mile Difference

225/40-18 3.5in 12.5in 25.1in 78.8in 804 0.0%

295/30-18 3.5in 12.5in 25.0in 78.4in 808 -0.5%

235/40-18 3.7in 12.7in 25.4in 79.8in 794 1.3%

315/30-18 3.7in 12.7in 25.4in 79.9in 793 1.4%

TurboLove Member

TurboLove

Posted
  • Author
Posted
comparison (theoretical)

Specification Sidewall Radius Diameter Circumference Revs/Mile Difference

225/40-18 3.5in 12.5in 25.1in 78.8in 804 0.0%

295/30-18 3.5in 12.5in 25.0in 78.4in 808 -0.5%

235/40-18 3.7in 12.7in 25.4in 79.8in 794 1.3%

315/30-18 3.7in 12.7in 25.4in 79.9in 793 1.4%

Thanks WrossTT! Since I am not sure what the comparison shows, would you mind summarizing/interpreting?.....I'm a total novice.

thanks!!

wross996TT Member

wross996TT

Posted
Posted
comparison (theoretical)

Specification Sidewall Radius Diameter Circumference Revs/Mile Difference

225/40-18 3.5in 12.5in 25.1in 78.8in 804 0.0%

295/30-18 3.5in 12.5in 25.0in 78.4in 808 -0.5%

235/40-18 3.7in 12.7in 25.4in 79.8in 794 1.3%

315/30-18 3.7in 12.7in 25.4in 79.9in 793 1.4%

Thanks WrossTT! Since I am not sure what the comparison shows, would you mind summarizing/interpreting?.....I'm a total novice.

thanks!!

The table doesn't align well, but there are seven columns of information....bottom line is you want to keep the % differences to a minimum (some is OK). Less difference is better...or you could get poor performance/wear/psm...I believe you should strive for less than 1% difference.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share
Go to topic listing
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.