Is this true?.....

Dougiebaby · 10-24-2002, 09:47 AM

When changing tire size (for example: from a 235/45-17 to 225/45-17) you can change either wider or narrower as long as the overall diameter does not change more than 3% (so that I will not screw up speedo and other monitoring devices)?

In the above example the diameter for the 235/45-17 is 25.4 and the diameter for the 225/45-17 is 24.9 so...

25.4 - 24.9 = .5
.5 / 25.4 = .019685 or 1.9685%

Getting back to the question, is the key 3% or is it some other percentage?

MikekiM@PureMS · 10-24-2002, 10:37 AM

3% isn't fixed by any means.
Really, the goal in increasing or decreasing the width of the tire is to maintain the same overall diameter. There are some margins allowed in increasing, or decreasing the overall diameter, but the percentage isn't necessarily fixed at 3%.

It depends on a number of factors, but most important is what you the driver is willing to deal with. Increasing the diameter causes a couple of issues, rubbing, mis calibrated speedometer, and slower acceleration.

The amount your car is lowered will most likely determine the rubbing factor. Stock heights certainly allow for more room.
There are calculators on the net that can show what your corrected speedometer will read. What you're willing to accept is up to you.
And slower acceleration will definitely be noticeable. Just chip the car, and that'll go away.

Good luck

Singletrack · 10-27-2002, 01:24 AM

Eddie@Tirerack · 10-29-2002, 10:53 AM

10-24-2002, 10:37 AM	#2
MikekiM@PureMS Audiworld Premium Sponsor Garage is empty, add now Join Date: Dec 2000 Location: San Diego, CA Posts: 15,547	Sort of 3% isn't fixed by any means. Really, the goal in increasing or decreasing the width of the tire is to maintain the same overall diameter. There are some margins allowed in increasing, or decreasing the overall diameter, but the percentage isn't necessarily fixed at 3%. It depends on a number of factors, but most important is what you the driver is willing to deal with. Increasing the diameter causes a couple of issues, rubbing, mis calibrated speedometer, and slower acceleration. The amount your car is lowered will most likely determine the rubbing factor. Stock heights certainly allow for more room. There are calculators on the net that can show what your corrected speedometer will read. What you're willing to accept is up to you. And slower acceleration will definitely be noticeable. Just chip the car, and that'll go away. Good luck __________________ www.purems.com 866-397-5487 \| San Diego, CA \| mike@purems.com \| Specials on Twitter!

10-27-2002, 01:24 AM	#3
Singletrack AudiWorld Super User Garage is empty, add now Join Date: Sep 2001 Posts: 16,037	The 3% is just a guideline really. __________________ 2008(9?) S5 - ordered 3/29/08 2004 Subaru Impreza WRX STi 2000 A6 2.7T - Sold "On the run from Johnny Law; ain't no trip to Cleveland."

10-29-2002, 10:53 AM	#4
Eddie@Tirerack Member Garage is empty, add now Join Date: Mar 2000 Posts: 3,429	Copy paste me on MikekiMs post- good advice :) __________________ Eddie 2107- FORMER AudiWorld Wheel/Tire Forum Moderator

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10-29-2002, 10:53 AM
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