When Are R Compounds Shot?
09-15-2005 | 09:41 AM
#46
Three Wheelin'
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From: Plano, TX
Originally Posted by Bob Rouleau
My input - The Michelin Cup is good for about 25-30 heat cycles if driven hard. After that it takes FOREVER to get heat into the tire. If you can heat them up grip is pretty good. At somewhere ae 20 heat cycles I see a degradation in lap times. Past 25 or so, I get my butt handed to me by guys on fresher tires with the same car.
I have never corded a set of Cups at my home track which has a very smooth surface. They simply get too hard. On tracks with an abrasive surface, they might cord before getting too hard. Track surfaces vary widely and the issue of cording or not is not a solid indicator unless the experience if from the track you run on and the car is similar in weight and power.
Tim, you have a large investment in the car, why risk it for the price of a set of tires? Looking at ten good track days, I spend nearly as much on gas as I do on tires. I don't put low test in my car to save money.. mind you gas costs more here in the North Today 94 octane dropped(?) to only $1.37 (Canadian) a liter.
Rgds,
I have never corded a set of Cups at my home track which has a very smooth surface. They simply get too hard. On tracks with an abrasive surface, they might cord before getting too hard. Track surfaces vary widely and the issue of cording or not is not a solid indicator unless the experience if from the track you run on and the car is similar in weight and power.
Tim, you have a large investment in the car, why risk it for the price of a set of tires? Looking at ten good track days, I spend nearly as much on gas as I do on tires. I don't put low test in my car to save money.. mind you gas costs more here in the North Today 94 octane dropped(?) to only $1.37 (Canadian) a liter.
Rgds,
George
09-15-2005 | 11:03 AM
#48
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Three Wheelin'
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Larry, No way did Norm get 1.7 g's unless a highly banked turn or at the bottom of a hill. It takes a downforce car going fast to get a number up there. On a level turn, a normal car can get 1.3 or maybe 1.4 lat g's. Anything higher than this is open wheel type downforce stuff.
Bob, I didn't know that it would take the tires longer to heat up as they aged but you sure are right (Yes I am an idiot). I now have a low and high temperature tire alarm so that I know when they are cold and when they are too hot. You don't really need the hot alarm as you can feel it but the low temp helps if you forget.
I will throw the new tires on and try them for both events. I may take it a little easy at the first event.
Bob, I didn't know that it would take the tires longer to heat up as they aged but you sure are right (Yes I am an idiot). I now have a low and high temperature tire alarm so that I know when they are cold and when they are too hot. You don't really need the hot alarm as you can feel it but the low temp helps if you forget.
I will throw the new tires on and try them for both events. I may take it a little easy at the first event.
09-15-2005 | 11:35 AM
#50
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Originally Posted by ColorChange
Larry, No way did Norm get 1.7 g's unless a highly banked turn or at the bottom of a hill. It takes a downforce car going fast to get a number up there. On a level turn, a normal car can get 1.3 or maybe 1.4 lat g's. Anything higher than this is open wheel type downforce stuff.
BTW- I did tire tests all weekend with Dunlops and Pirelli. The Dunlops were faster since the Pirellis caused tremendous understeer. I was running similar compounds and sizes. Pirelli does make one size wider front and I am checking if they have 1 compound softer front. The rear pirellis were fine. The Dunlops are fastest right out of the box, the Pirellis took 1 session before they were reaspnable. All tire temps and pressures were good. I dont yet know about Pirelli longevity...
On the objective data side, with Dunlops, my max g's was 1.78 with Pirellis only 1.51
Norm
On the objective data side, with Dunlops, my max g's was 1.78 with Pirellis only 1.51
Norm
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Larry Herman
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Larry Herman
2016 Ford Transit Connect Titanium LWB
2018 Tesla Model 3 - Electricity can be fun!
Retired Club Racer & National PCA Instructor
Past Flames:
1994 RS America Club Racer
2004 GT3 Track Car
1984 911 Carrera Club Racer
1974 914/4 2.0 Track Car
CLICK HERE to see some of my ancient racing videos.
09-15-2005 | 11:36 AM
#51
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No problem Larry, I wasn't coming after you, just saying I don't believe the data. There is a problem somewhere as I am quite confident 1.7 is WAY too high for anything resembling a normal car in a normal turn.
Last edited by ColorChange; 09-15-2005 at 12:00 PM.
09-15-2005 | 12:06 PM
#52
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Since this pertains to VIR, there is a downhill right hand turn that flattens out (Hogpen) and causes significant suspension compression. That could explain the readings that you feel are higher than normal, but I really don't know. Norm's car is pretty aero, and seems to have enough wing to create a lot of downforce.
09-16-2005 | 01:45 PM
#53
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From: NorCal
Originally Posted by Bob Rouleau
My input - The Michelin Cup is good for about 25-30 heat cycles if driven hard. After that it takes FOREVER to get heat into the tire. If you can heat them up grip is pretty good. At somewhere ae 20 heat cycles I see a degradation in lap times. Past 25 or so, I get my butt handed to me by guys on fresher tires with the same car.
I have never corded a set of Cups at my home track which has a very smooth surface. They simply get too hard. On tracks with an abrasive surface, they might cord before getting too hard. Track surfaces vary widely and the issue of cording or not is not a solid indicator unless the experience if from the track you run on and the car is similar in weight and power.
Tim, you have a large investment in the car, why risk it for the price of a set of tires? Looking at ten good track days, I spend nearly as much on gas as I do on tires. I don't put low test in my car to save money.. mind you gas costs more here in the North Today 94 octane dropped(?) to only $1.37 (Canadian) a liter.
Rgds,
I have never corded a set of Cups at my home track which has a very smooth surface. They simply get too hard. On tracks with an abrasive surface, they might cord before getting too hard. Track surfaces vary widely and the issue of cording or not is not a solid indicator unless the experience if from the track you run on and the car is similar in weight and power.
Tim, you have a large investment in the car, why risk it for the price of a set of tires? Looking at ten good track days, I spend nearly as much on gas as I do on tires. I don't put low test in my car to save money.. mind you gas costs more here in the North Today 94 octane dropped(?) to only $1.37 (Canadian) a liter.
Rgds,
What are you guys getting for tire temps for the cups? I put on fresh cups for the last event at Tremblant and the highest I saw on the probe pyrometer was 181-183 rear (inside - outside) and 174-177 front (inside -outside).
09-16-2005 | 03:01 PM
#54
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Originally Posted by ColorChange
No problem Larry, I wasn't coming after you, just saying I don't believe the data. There is a problem somewhere as I am quite confident 1.7 is WAY too high for anything resembling a normal car in a normal turn.
09-16-2005 | 06:16 PM
#55
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sjanes - using an infrared (but a good one) I see 183-187-190 across the back and 175 175 179 across the front of fresh Cups. Those are surface temps measured from about 12 inches. Not as accurate as your probe but good enough for getting pressures in the sweet spot. My car is heavier and has more HP ( I think) than yours does, which has to impact the temps.
Rgds,
Rgds,
09-16-2005 | 06:33 PM
#56
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RJay, bigger tires does not yield direct higher g's. Stickier rubber does. And most slicks get to 1.3- or maybe 1.4. To get higher than this, you need super low cg and/or downforce. How do I know? Looking at numerous car's data and the literature.
09-17-2005 | 03:33 PM
#57
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From: NorCal
Originally Posted by Bob Rouleau
sjanes - using an infrared (but a good one) I see 183-187-190 across the back and 175 175 179 across the front of fresh Cups. Those are surface temps measured from about 12 inches. Not as accurate as your probe but good enough for getting pressures in the sweet spot. My car is heavier and has more HP ( I think) than yours does, which has to impact the temps.
Rgds,
Rgds,
09-18-2005 | 02:27 PM
#58
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Do any of you guys do a "scrub" session on your tires? I never hear anybody talking about it with R compounds, so I don't know if it is a relavent concept for these tires.
Doing a scrub session with the soft slicks we use on the formula car makes a real difference in the number of heat cycles they're useful for. The first time the tires are placed on the car I run a couple gentle warm up laps, 2 hot laps (being careful not to slide the car), and a couple cool down laps. The tires are then allowed to sit and cure for 24+ hours. Tires treated this way are good for qualifying and a race and a few practices sessions before the grip becomes completely unacceptable. If I qualify on stickers, by the end of the race the tires are ready to be added to the tracks tire wall. I'm curious if there is any similar phenomenon in the tires you guys use. It may be that the chemistry of tires for 3000lb cars is so different from an 1100lb car's slicks that the "scrub" heat cycle is irrelavent.
Doing a scrub session with the soft slicks we use on the formula car makes a real difference in the number of heat cycles they're useful for. The first time the tires are placed on the car I run a couple gentle warm up laps, 2 hot laps (being careful not to slide the car), and a couple cool down laps. The tires are then allowed to sit and cure for 24+ hours. Tires treated this way are good for qualifying and a race and a few practices sessions before the grip becomes completely unacceptable. If I qualify on stickers, by the end of the race the tires are ready to be added to the tracks tire wall. I'm curious if there is any similar phenomenon in the tires you guys use. It may be that the chemistry of tires for 3000lb cars is so different from an 1100lb car's slicks that the "scrub" heat cycle is irrelavent.
09-18-2005 | 02:32 PM
#59
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Originally Posted by prg
Do any of you guys do a "scrub" session on your tires? I never hear anybody talking about it with R compounds, so I don't know if it is a relavent concept for these tires.
09-18-2005 | 06:30 PM
#60
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From: Mount Pleasant, South Carolina
I don't have the track/time to do that, unless one could do it with one set of tires and wait until the next DE and it still applies? But, then you've lost your 24 hour window.
Originally Posted by prg
Do any of you guys do a "scrub" session on your tires? I never hear anybody talking about it with R compounds, so I don't know if it is a relavent concept for these tires.