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Old 04-28-2008, 12:54 PM   #1
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Default Foam Tire Compound & Width: Laptimes??

As the title says, I'd like to discuss everyones opinions on the relationship between Foam Tire Compounds & Widths in relation to Laptimes on a carpet track.... My goal is to get some good information compiled here for us to share.

Here is a quick background. At my local track most of us run Jaco Prism Pinks, Magenta's, Double Pinks, or Parma Pro Magenta's. Over the past few weeks, I've been running Jaco Pinks or Parma Magenta's. Neither seemed perfect to me, but I stuck with the Pinks for a few months now.

Shore Rating:
Jaco Pink = 30
Jaco Magenta = 32
Jaco Double Pink = 35
Jaco Lilac = 38

Parma Magenta = 35

This last weekend I wanted to test the entire race day using Jaco Prism Double Pinks, but narrowed to 26mm. Jaco and Parma tires are roughly 28mm wide out of the box. To my surprise, the narrowed double pinks worked better than 28mm Pinks, and provided more consistent lower laptimes. Another racer took the tires right off my car and mounted them on his for some practice and confirmed my findings.

My theory is that too soft a tire increases rolling resistence and scrubs off more speed in the turns. Conversely, while a narrower tire reduces the contact patch, it increases the load on a smaller contact patch, and has less rotational mass.

What are your thoughts and experiences?

Last edited by kn7671; 04-28-2008 at 01:08 PM. Reason: title change for more accurate description
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Old 04-28-2008, 01:10 PM   #2
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I don't think you can ever have too much traction.

My personal opinion is more traction = more corner speed, faster laptimes.

If the laptimes are slower with more traction then the car is not setup for the extra traction. If you go to a big race the laptimes always get faster as the week goes on. If more traction were worse, wouldn't you get slower?

Pinks don't always have more traction. I find most of the time they have less traction/side bite because they are softer they car "moves" around more causing it to be looser. At a big race if your car is lifting, pinks will usually help it out if you can't find a way to keep the wheels down. This way you are taking away traction, but if you can't drive it or tune the car right there is no advantage to more traction.

Traction is your friend if you can tune your car to handle it.

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Old 04-28-2008, 04:09 PM   #3
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So is it not possible to have too much traction? To the point that you now have to tune out traction?

Wouldn't it be easier to use the tire compound that works best?
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Old 04-29-2008, 04:09 AM   #4
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it's easier to start with harder compound for practice. the harder compound has more forgiven characteristics because it's firmer and more stable. it losses traction easier, but also regains traction easier.

once you get familiar to the track and your car's setting, then you can harden the spring with a fix rate in match to the softer compound. Then you would be race ready.

Softer compound is not always the best. on a very good traction surface and hot weather, over traction can easily lead to accident with lift off/roll over.

Use firmer insert or cut the foam to lower profile, could greatly improve stability when using soft compounds.
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Old 04-29-2008, 07:17 AM   #5
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This is also a reason why a lot of foam shod cars will use sway bars, to get the optimum handling from the car. Rubber tyres tend to be more forgiving and do not use sway bars so much to help the handling
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Old 04-29-2008, 12:58 PM   #6
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Quote:
Originally Posted by tc3team View Post
This is also a reason why a lot of foam shod cars will use sway bars, to get the optimum handling from the car. Rubber tyres tend to be more forgiving and do not use sway bars so much to help the handling
Not true, since rubber tires tend to roll more and need to generate more traction, we use roll bars to control the kind of roll. Many rubber cars use roll bars.
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Old 04-29-2008, 02:55 PM   #7
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To be honest, most foam tire cars today don't use sway bars at all.
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