What are the largest tires I can have on my car?
05-29-2002, 09:58 PM
#1
Instructor
Thread Starter
What are the largest tires I can have on my car?
I just purchased my first Porsche this past weekend....an '89 951. <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" /> When I bought the car I noticed that it had 17" wheels & big tires on it, but they were fairly new & I didn't think much of it....thought it looked pretty cool. The fronts are 245/45/17's and the rears are 275/40/17's. Now that I've driven it a bit I notice that under moderately hard driving there seems to be tire rub. I plan on doing DE events at Mid Ohio and am wondering if this could damage the tires or body of the car. Has anyone ever used or seen anyone use tires this large? What are my options? The tires (Yokohoma 520's) only have about 1000 miles on them and look brand new....I hate to buy new if I don't have to. Thanks in advance!
05-29-2002, 10:07 PM
#2
Race Director
Take off the tires and look in the fender wells to see where the rub is occuring. It will show up as shiny spots where the tire has rubbed off the paint.
In the front this typically occurs at a 45-degree angle upwards towards the front. This is the point where the tire crosses the outside edge of the fender when the wheel is turned. Then hit a bump that compresses the suspension more than 2" and you've got RUB! Nothing you can really do about this...
In the rear, the 1" taller 275/40-17 tire will front on the fender directly in front of the tire. That's because the extra 1" reaches forwards and that point comes closest to the tire.
In the front this typically occurs at a 45-degree angle upwards towards the front. This is the point where the tire crosses the outside edge of the fender when the wheel is turned. Then hit a bump that compresses the suspension more than 2" and you've got RUB! Nothing you can really do about this...
In the rear, the 1" taller 275/40-17 tire will front on the fender directly in front of the tire. That's because the extra 1" reaches forwards and that point comes closest to the tire.
05-29-2002, 10:42 PM
#3
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On an '89 you can easily fit 275/40/17 all around if you have the right offset on your wheels. If you are rubbing currently it is because you have wheels from another car...
05-29-2002, 11:26 PM
#4
Instructor
Thread Starter
Yes, the wheels are an aftermarket wheel. Is it possible that there is some kind of spacer in place that I can remove to bring the wheels closer together? Is there any real danger in the tires rubbing? <img src="confused.gif" border="0">
05-30-2002, 04:39 AM
#5
Race Director
You might have the TurboS vs. Turbo offset difference here. The stock TurboS wheels are 65/60mm offset F/R which sits inwards about 1/2" more than the standard Turbo offsets of 52.3mm F/R.
Some people 'think' that you can put a set of Turbo offset wheels onto a TurboS. And yes, most of the time, you can get away with it in stock rim widths and stock tire sizes. BUT, when you go to <a href="http://members.rennlist.com/951_racerx/WheelsFAQ-SizusMaximus.html" target="_blank">sizus maximum</a> on your rims, you have to customize offset for each and every model iteration specifically.
Here's a test, take the rear wheel off and look for bare metal along the outer fender lip where the paint has been rubbed off. Most likely it's on the fender at 9 and 3 o'clock directly in front of the tire. Also look for a rubbed spot on the inner fender well at 45-degree upwards towards the front where the undercoating has been worn away. If you only have rubbing on the outside, most likely you have the Turbo (non-S) offsets on your rear wheel because the wheel is sitting too far outwards.
Some people 'think' that you can put a set of Turbo offset wheels onto a TurboS. And yes, most of the time, you can get away with it in stock rim widths and stock tire sizes. BUT, when you go to <a href="http://members.rennlist.com/951_racerx/WheelsFAQ-SizusMaximus.html" target="_blank">sizus maximum</a> on your rims, you have to customize offset for each and every model iteration specifically.
Here's a test, take the rear wheel off and look for bare metal along the outer fender lip where the paint has been rubbed off. Most likely it's on the fender at 9 and 3 o'clock directly in front of the tire. Also look for a rubbed spot on the inner fender well at 45-degree upwards towards the front where the undercoating has been worn away. If you only have rubbing on the outside, most likely you have the Turbo (non-S) offsets on your rear wheel because the wheel is sitting too far outwards.
05-30-2002, 06:13 PM
#6
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Brian, Just trade your wheels in for 17" 993 wheels. You can run 275's and have no rubbing unless your car has been lowered more than the typical 1.5". They work on my 88 944ts.
