Can too much grip hurt track times?

[7thgear]

Originally Posted by rice_classic

And I bet you don't have any empirical data to disprove either?

forget him, anyone that needs to have science explained to them isn't worth the effort.

[robispec]

Originally Posted by Huehuecoyotl

what road course, curious>?

buttonwillow 13 ccw really hard on tires...

[GTM_Challenge]

Im still sitting on the fence on this one. I keep getting faster and faster in my s2000 all the time...and Ive had the car for years and am still getting faster. Same for my miata and same for my FRS. Track temps vary a lot through out the season here. Of course old wide tires will be slower than new skinnier tires.

I think it's highly driver dependent too. If you corner at the exact same rate because you brake in the same place and get on the gas in the same place with the smaller tires as the larger tires, i can see the smaller tires being faster. But if you are able to utilize the grip, you can brake later, corner quicker, and have a higher exit speed which in my mind is faster at a lot of tracks as long as they aren't high HP/long straight courses.

Feel free to disagree, but I don't think ANY of us are consisent enough and have the same control variables all the time to make any sort of blanket statement at this point.

[renfield90]

Originally Posted by rice_classic

...

Thank God we don't drive Spec Miatas. I speak from the experience of having tracked a ~120whp car...

Originally Posted by 7thgear

forget him, anyone that needs to have science explained to them isn't worth the effort.

And you need a lesson in how science works. He made the original assertion, he should have the data to back it up. I believe in data. I don't believe in conjecture unless it can be tested and verified.

What is the coefficient of rolling resistance for the wider tire compared to the smaller tire? How many Newtons of resistive force does that translate to? How much does the wider tire slow you down on, say, a 300m straight? Even simple data logging things like apex speed, max lateral g, and top speed at the end of a straight will help sort out what's going on here. If you come to me with zero data, the scientist in me is required to question your conclusions.

[renfield90]

Originally Posted by GTM_Challenge

Feel free to disagree, but I don't think ANY of us are consisent enough and have the same control variables all the time to make any sort of blanket statement at this point.

By far the best point in this entire thread.

[CSG Mike]

Originally Posted by GTM_Challenge

Im still sitting on the fence on this one. I keep getting faster and faster in my s2000 all the time...and Ive had the car for years and am still getting faster. Same for my miata and same for my FRS. Track temps vary a lot through out the season here. Of course old wide tires will be slower than new skinnier tires.

I think it's highly driver dependent too. If you corner at the exact same rate because you brake in the same place and get on the gas in the same place with the smaller tires as the larger tires, i can see the smaller tires being faster. But if you are able to utilize the grip, you can brake later, corner quicker, and have a higher exit speed which in my mind is faster at a lot of tracks as long as they aren't high HP/long straight courses.

Feel free to disagree, but I don't think ANY of us are consisent enough and have the same control variables all the time to make any sort of blanket statement at this point.

Consistency doesn't matter when the data from on-board dataloggers is so conclusive.

More importantly, the straightline speed differentials are SO huge that we don't need to verify with data.

E.g. with 225 RS3, I'll hit 112mph before "lost hill" at Buttonwillow. With 245 RS3, I barely hit 106mph. This is all through large sweeping turns where you're WOT. The limiting factor to the entry of this section is "busstop". With the 225, I'm hitting the exit apex at about 84mph. With the 245, I hit it at about 86.

Think of it this way. How many turns are you limited by tire grip? How many turns are you power limited.

Buttonwillow 13CW (the socal standard), turn, turn name, limiting factor, approx entry (before braking) and apex speeds (for the CSG BRZ) on 225 RS3 :

T1 Sunrise - grip - 107, 70
T2 Buttonhook/Offramp - grip - 89, 35
T3a Cotton Corners - grip (hot entry) - 92, 55
T3b - grip (sacrifice) - 50
T3c - Power - 55
T4 Grapevine - power - 70
T5 Club Corner - power - 90
T6 Left kink- power - 98
T7 Bus Stop - grip - 103, 81
T8 Right kink - power - 88
T9 Riverside - power - 97, 100
T10 Left Kink - power - 108
T11 Lost Hill/Phil Hill - grip - 112, 72
T12 Right kink - power - 85
T13 Drag strip - power - 92
T14 Sweeper - grip - 106, 58
T15 Esses - power - 98 (final left apex)
T16 Sunset - grip - 110, 65

Speeds for identical car (same coilovers, same damper setting, same brakes, but with bolt-on power adders) with 245 RS3, same driver (me):

T1 Sunrise - grip - 98, 73
T2 Buttonhook/Offramp - grip - 83, 39
T3a Cotton Corners - grip (hot entry) - 88, 57
T3b - grip (sacrifice) - 54
T3c - Power - 57
T4 Grapevine - power - 70
T5 Club Corner - power - 87
T6 Left kink- power - 93
T7 Bus Stop - grip - 108, 83
T8 Right kink - power - 89
T9 Riverside - power - 95, 95
T10 Left Kink - power - 99
T11 Lost Hill/Phil Hill - grip - 105, 74
T12 Right kink - power - 85
T13 Drag strip - power - 92
T14 Sweeper - grip - 101, 60
T15 Esses - power - 93 (final left apex)
T16 Sunset - grip - 13, 66

[GTM_Challenge]

Mike, were those taken the same day, no headwind or tailwind, same track temps, same barometric pressure so the air density is the same, etc? I get the data, and see it, but unless testing was done under the EXACT same circumstances, I take all data with a grain of salt. There are many, many outlying factors than just lap times IMO.

Edit* - Even two equal cars, EVERYTHING being the same - one car will be faster than the other. Its physics. One car will always be faster. They aren't going to return the same exact lap times. One motor will be stronger, one will corner better, etc.

I'm not saying you're wrong, Im just urging people to keep their minds open, that's all. You know how I am.

[CSG Mike]

Conditions no longer matter, when the comparison has already been done so many times at the same track, and the results are consistently the same.

I think between Robi and us, we typically have 5 sets of rims and tires at the track on weekends where we both show. A lot of confounding variables simply are meaningless (heat cycles don't affect straightline speeds, etc.)

[GTM_Challenge]

Sigh. I already know which side your on. Ive got to prove it to myself. I trust no one.

[robispec]

My but dyno says that the 205's are FAST in a straight line but slightly slower in the corners...then I get off track and my spotter tels me I'm KILLEN them in the corners lol....

[CSG Mike]

You're alone in testing your FR-S locally, for the most part. Between Robi and I, we've probably driven a few hundred different setups (thanks to people who ask us to drive their respective cars).

It's REALLY REALLY easy to test straightline speed...

[GTM_Challenge]

Originally Posted by CSG Mike

You're alone in testing your FR-S locally, for the most part. Between Robi and I, we've probably driven a few hundred different setups (thanks to people who ask us to drive their respective cars).

It's REALLY REALLY easy to test straightline speed...

Easy fix...you need to move to Chicago.

Womp womp.

[Dave-ROR]

Originally Posted by GTM_Challenge

Sigh. I already know which side your on. Ive got to prove it to myself. I trust no one.

I agree. It's why I bought another set of wheels with the smaller tires to test. I had the same results as Mike and Robi. I tested on the same weekend, but not the same day..

[CSG Mike]

He's got the resources to do it...