Planet-9 Porsche Forum banner
1 - 8 of 8 Posts

·
Registered
Joined
·
481 Posts
Discussion Starter · #1 ·
I am having a friendly disagreement with someone on low profile tires and performance. He maintains that a taller sidewall (such as 45 or 50 series) on a 17" wheel will perform better than a 35 series on a 19", due to better tire flexibility and compliance with uneven road surface. Seems to me most people putting Porsches on the track are using 18s and 19s for a reason (other than having to big enough to fit around brakes). Would an 18 or 19 offer superior lap times vs a 17, all else being equal? I told this person that most Porsche track guys are using 18s and 19s because they work best, and he responded by simply saying you are all wrong. That money does not equal intellect. I can not let that go without a response!

- Phil
 

·
Premium Member
Joined
·
311 Posts
Walter Rohrl has been quoted as saying that 19's (with PASM) are necessary to extract the most performance on the track from the Cayman. Who am I to argue? ;)
 

·
Premium Member
Joined
·
3,862 Posts
He may be correct that their flexibility and compliance may improve handling over uneven road surfaces - but that does not usually apply to a race track or smooth surface. I think that it is pretty well-accepted that a shorter sidewall increases steering response and contact patch (because of less sidewall flex). Here's what Tire Rack has to say in one of their tech articles:

"The shape of a tire's contact patch or "footprint" greatly influences its performance and is dependent on its profile or "aspect ratio". Low profile tires (most performance tires) have a short and wide contact patch that is effective in converting the driver's input into very responsive handling, cornering stability and traction...especially on dry roads.

High profile tires (light truck and most passenger tires) have a long and narrow contact patch which helps to provide predictable handling, a smooth ride and especially good traction in snow."
 

·
Registered
Joined
·
621 Posts
That's right. Taller sidewalls are indeed more tolerant of (adhere better to) bumps. But, we are primarily interested in handling on relatively smooth roads and tracks. These cars are more closely related to road-racing cars than other forms of motorsport. If this were a rally-oriented group (i.e., Subaru), then we would necessarily get into taller profiles.
 

·
Registered
Joined
·
2,795 Posts
I agree with the above, and I too wouldnt argue with Walter Rohl :D

In all seriousness, I tried an AX event with my old car once (Citroen C4) and it had 15" wheels... Lets just say they added a speed breaker and made everyone repeat the track because of me. I flexed my tires so hard going into the last corner that the tire almost came off the rim!
 

·
Caymaniac
Joined
·
5,663 Posts
I knackerd my 18 inch wheels so badly, I will be running my 19s on OEM Bridgestones at the home track at the end of the month. I will see if it makes a difference.

People run 18s versus 19s for cheaper tires and better selection. Not for perceived handling improvements, AFAIK.

Out on the street, the advantages of more cushion between your wheel and the road may outweigh the ultimate advantage of a lower profile tire.
 

·
Caymaniac
Joined
·
5,663 Posts
Walter Rohrl has been quoted as saying that 19's (with PASM) are necessary to extract the most performance on the track from the Cayman. Who am I to argue? ;)
Whom? Um, you are a guy who is extracting the most performance out of his Cayman by trading it for a GT3.:hilarious:

I'd say that is better than PASM + 19 inch wheels, and that you are, in fact, arguing with Walter. ;)
 

·
Registered
Joined
·
16 Posts
1 - 8 of 8 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top