tires, tires, tires!

[Schumi_Jr]

I figure we should start a thread on tires since they ARE the most important component of a racecar...

first I have a question about Radials. I haven't looked that carefully into any of the typical suppliers (Hoosier, Goodyear, Avon, etc) products, but I am curious why most teams run bias-ply slicks. Is it the lower mass/ rotating inertia? I noticed from the FSAE Goodyear tire data that their construction has a really low cornering stiffness. It looks like peak cof at 12 deg slip. The drag at that high a slip angle would be huge. I have seen data for the Hoosier 7.5x13 R25's and I noticed very similar cornering stiffness. All this would make me think that radials would be much better. Their higher stiffness means lower slip angles and less drag for the same amount of grip. The only downsides I can think of are a higher rotating inertia (a big deal when you only have 80hp) and decreased driveablility. Can someone more knowledgable offer some insight?

On another note, has anyone tested the new Goodyear R065 compound? We will be sticking with Hoosiers this year, but I definately want to test the new Goodyears this summer. thanks

Aaron Johnston
Muffler Team Director
University of Waterloo FSAE

[This message was edited by Schumi_Jr on January 31, 2003 at 12:05 PM.]

[Schumi_Jr]

I figure we should start a thread on tires since they ARE the most important component of a racecar...

first I have a question about Radials. I haven't looked that carefully into any of the typical suppliers (Hoosier, Goodyear, Avon, etc) products, but I am curious why most teams run bias-ply slicks. Is it the lower mass/ rotating inertia? I noticed from the FSAE Goodyear tire data that their construction has a really low cornering stiffness. It looks like peak cof at 12 deg slip. The drag at that high a slip angle would be huge. I have seen data for the Hoosier 7.5x13 R25's and I noticed very similar cornering stiffness. All this would make me think that radials would be much better. Their higher stiffness means lower slip angles and less drag for the same amount of grip. The only downsides I can think of are a higher rotating inertia (a big deal when you only have 80hp) and decreased driveablility. Can someone more knowledgable offer some insight?

On another note, has anyone tested the new Goodyear R065 compound? We will be sticking with Hoosiers this year, but I definately want to test the new Goodyears this summer. thanks

Aaron Johnston
Muffler Team Director
University of Waterloo FSAE

[This message was edited by Schumi_Jr on January 31, 2003 at 12:05 PM.]

[David Money]

We tested the Goodyear R065 compound and it is real sticky. It is designed to last only through the endurance event. As to how it compares to the Hoosiers, we recently bought a set of hoosiers (mid sticky compound, can't remember the number) and our star driver said that he can tell a huge difference and that there is less grip with the new Hoosier tires.

As to the tire data, I would LOVE to get my hands on the Hoosier data as we have none from them...any help here?

David Money
Univ of Texas at San Antonio

[Charlie]

We tested the Goodyears recently, in an auto-x style practice. They are OK, not significantly soter than the softest Hoosiers. We didn't do a direct comparison with the Hoosiers though, but we ran them last year.

The Goodyears are also about 1 lb heavier each.

If you can find radials that have a soft enough compound they might be better. I imagine that's the reason nobody runs them though.

-Charlie Ping
Auburn University FSAE 1999-present

[vinHonda]

Interesting......

University of Toronto Formula SAE Racing Team
www.fsae.utoronto.ca (http://www.fsae.utoronto.ca)

[Wouter Mollers]

I'm surprised to hear that the Goodyears weigh slightly more than their Hoosier counterparts. We've requested the numbers from both Goodyear and Hoosier some time ago. A Goodyear 20.0 x 6.5 - 13 R065 weighs 8.8 pounds and a Hoosier 20.0 x 6.0 - 13 R25 is supposed to be 12 pounds. Can anybody (Charlie perhaps) confirm these numbers?

Wouter Mollers
Suspension Manager
Delft University of Technology

[Charlie]

I can't remember the exact numbers (stupid that I didn't record them). But I weighed a new sticker Hoosier R25 vs a new Goodyear R065 and the goodyear was right at 1 lb heavier. I seem to recall the weight was around 10 lbs.

I've weighed worn tires and they can lose a lot of weight, so beware of weighing used tires to compare.

I'm sure the superior compound will be more of a factor than weight, so I look forward to some back-to-back testing of the two.

-Charlie Ping
Auburn University FSAE 1999-present