Tire size - 986 Forum - The Community for Porsche Boxster & Cayman Owners

koya1893 · 07-20-2007, 03:25 AM

I know this particular thread is like any other posted before but I need to ask the question. I have the stock 17" on my 986 I was going to get some new wheels and tires but recent purchase prevented from doing that, a new car for my daughter going to college. what brand and what is the widest tires I can install on the stock 17" wheels? some of the combination wheels I was looking at had 225 in front and 275 for the rear? Can I install the same size on the stock wheels without rubbing?

Boxtaboy · 07-20-2007, 04:06 AM

I simply upsized my front tires from 205/50 to 225/45, and kept the rears at the factory spec 255/40. The reason I did this is because it helps to reduce the understeer by reducing the stagger from 50 to 30 (225 front / 255 rear). Porsche built in a lot of understeer with the 205 front / 255 rear setup for novice drivers who might have the tendancy to swap ends, imo.

vipola · 07-20-2007, 05:01 AM

This will look like a newby question but, what's that thing about understeering?

I bought my boxster with already some 225 in front. I find It great because some tires are hard to find in 205 size. But what does it change to drive with 225 or 205 in front?

Thanks

Boxtaboy · 07-20-2007, 05:26 AM

Quote:

Originally Posted by vipola

This will look like a newby question but, what's that thing about understeering?

I bought my boxster with already some 225 in front. I find It great because some tires are hard to find in 205 size. But what does it change to drive with 225 or 205 in front?

Thanks

Ok, in layman's terms, let's say you are driving down a road and you are coming up to a right hand turn- as you turn right into the corner, the front of your car feels as if it wants to go straight instead of turning right. That's understeer. Oversteer is as if as you're turning right, the rear end of the car feels like it wants to swing out from behind you and make the car spin. That's the best way I can explain it.

Generally, if you are a more experienced driver, you like to have a bit more balance, and less understeer because you can better utilize the throttle to power through turns. I am sure that the lawyers at Porsche, however, encouraged designers to make the basic set up of the car to provide more understeer so that novice drivers don't end up spinning the car in turns, and thus causing litigation problems for Porsche saying that the car is dangerous.

ChrisZang · 07-20-2007, 05:59 AM

Here is the explanation about understeer and oversteer from Walter Roehrl, multiple Rally World Champion and now Porsche test driver:

Understeer is when you SEE the tree you are about to hit
Oversteer is when you only HEAR the crash ...

vipola · 07-20-2007, 06:03 AM

Lol

So there is nothing wrong having 225 in front comparatively to 205 except that It may turn a bit more agressively on the front?

koya1893 · 07-20-2007, 07:03 AM

Thank you for all the input. Reading all the diologing about "understeer and oversteer" I can honestly say that my car has Oversteer. the reason I say that is when ever I take it out on some back roads and take a corner at 60-70mph the back end wants to beat the front end around the corner.
Any thought on General UHP tires? How about 19" wheels? What size to go with for 19"?