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Rob S.

TTS/TTU tire width rule

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Rob S.

OK.....I'm going to throw this out there and hopefully the lashing is not too severe.

 

My question is focused around tire width in the TTS and TTU classes. What are two aspects of the car, which are currently defined in the TTS/TTU rules, that have a big impact on lap times; whp and tire width (we will assume the same car, tire brand and tire compound for this example). In the TTS/TTU rules adjustments are made for drive type (FWD being a disadvantage therefore getting "points" to decrease weight to power ratio therefore increasing whp and AWD just the opposite => advantage, therefore less whp). Body type is also defined yet tire width is only adjusted up to a 275?? Just as a car under the weight of 3201 is perceived as an advantage so is using a bigger tire (increased grip for non-aero corners and putting the power down coming out of these corners.

 

Alright.....so on to my example and again this is just an example and I want to get people's opinion not a beat down for bringing it up. I'm sure the people running > 295 wide tires are not going to be super stoked about the idea but this is in the interest of pointing out an aspect of the current rules.

 

 

Tire Adjustment for weight to power ratio:

If: 245 or smaller, add 0.8

If: 275 to 250, add 0.4

If: 295 to 280, zero

If: 325 to 300, subtract 0.3

If: 345 to 330, subtract 0.6

If: Greater than 345, subtract 1.0

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RAFTRACER

Sounds to me alot like you need several things.....1) saw 2) fender flares (or not) 3) BIGGER wheels 4) BIGGER tires....

 

These two particular classes do not have tire issues like TTA> , The rules are the same for me as they are for you....Why would we want to take a negative modifier for tire sizes that we can easily fit in OUR fenders.....Or why would you want to make more power on tiny little insufficeint tires.......S,U,R isn't really for street cars and they fixed almost all of the rules issues that they had previous to this year... Although at least I know of two registered ,insured and licensed cars that won two of the S,U,R classes at the championships.

 

 

If I remember correctly, I have seen a 240 with 315 tires in that "other" sanctioning body running around cones...looked pretty nasty....

 

Your proposed modifier would take my 5.95:1 TTU car straight to TTR.......My vote would be "NO WAY" obviously, but I dont make the rules.

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Rob S.
Your proposed modifier would take my 5.95:1 TTU car straight to TTR.......My vote would be "NO WAY" obviously, but I dont make the rules.

 

It wouldn't make your 5.95 lower (more allowable whp) it would make it higher and you'd have to make a little less whp. You should add 0.3 or 0.6 to your current weight to power ratio and then recalculate allowable whp. Now that you mention TTR, didn't you beat the 1st place TTR car by 3 seconds??? Great lap by the way!

 

The question is not about whether I can cut up my car (and change wheels bearings and ball joints after everything event), it's about making fair, close competition. Otherwise you end up with a spec classe.

 

My car:

Body type = coupe: 0 adjustment

Drive type = RWD: 0 adjustment

Tire = 275: +0.4 (bonus whp for small tires)

Weight = 2725lbs: -0.5 (penalty for being light)

Result is 8.8

 

Body type = coupe: 0 adjustment

Drive type = RWD: 0 adjustment

Tire = 335: 0 adjustment

Weight = 3300 - 3349lbs (I'm not sure on the weight): +0.05 (bonus for being heavy)

Result is 8.65

 

The C5 Z06 has a lower weight to power ratio then my car with me running 275 tire. Let's look at it with >275 tires:

 

My car:

Body type = coupe: 0 adjustment

Drive type = RWD: 0 adjustment

Tire = > 275: 0 adjustment

Weight = 2725lbs: -0.5 (penalty for being light)

Result is 9.2

 

I guess if I run 335 tires I can run in TTA (ratio < 8.7). OK. Sign me up. Just like you said....I don't make the rules either. I just bring up areas of concern and abide by whatever the sanctioning body decides on.

 

BTW - TTR is the only true unlimited non-street car class.....just based on the rules. Otherwise there wouldn't be adjustments for body type and drive type in TTS/TTU.

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Spectator Racing

I'm undecided on the issue. I also have to run 275's on all four corners to get the 0.4 point bonus. I usually run 315's on the rear, 275's up front (pretty typical for a 'vette).

 

What I learned this season is that my rear tire size mattered very little. I swapped back and forth at different events, and all of my best laps were on the 275's. I do notice a difference (the rear feels looser) but clearly in my case there was no additional speed to be had with wider rears.

 

I ran scrubs all year, and bought my first set of new tires (Hankooks) for Nationals and knocked over a second off my previous best. New tires made a much bigger difference than wider tires. I know this is nothing we didn't already know, but to me it shows that tire size is a bit less of a factor than we all think.

 

Example #2 is Ken, who won TTA on 275's with 2nd, 3rd, and 4th all running larger tires (at least 295) in the exact same car type (Z06).

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Rob S.

I can see how changing just the rears could have less of an affect than changing the fronts also. A large stagger can cause understeer if suspension settings are not changed to take advantage of the larger rear tires. However, I'm sure your lap times would decrease with 315's square. Your mechanical grip would increase with the 315's in the front and your corner speed would increase.

 

I'm sure Ken's lap times would have be even lower with 315's but he probably was using the 275's because he didn't have any points left in TTA.

 

Also put 275's on Jeff Moser's Z06 and I bet he would have a hard time running a 1:33.1.

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L98Terror
I can see how changing just the rears could have less of an affect than changing the fronts also. A large stagger can cause understeer if suspension settings are not changed to take advantage of the larger rear tires. However, I'm sure your lap times would decrease with 315's square. Your mechanical grip would increase with the 315's in the front and your corner speed would increase.

 

I'm sure Ken's lap times would have be even lower with 315's but he probably was using the 275's because he didn't have any points left in TTA.

 

Also put 275's on Jeff Moser's Z06 and I bet he would have a hard time running a 1:33.1.

 

100% agreed, IMO for Jon to really have a good comparision he would have needed to run the same brand with the same heat cycles in different sizes. It's hardly a valid test when your using scrubs.

 

I ran 275s square because that is the largest tire Hankook makes and Hankook is the best tire there is, not to mention they paid $1k for 1st.

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