944spec R888 Tire Review - First 3 Heat Cycles
10-09-2008, 03:46 PM
#31
Race Director
Thread Starter
Toyo R888 Review Heat Cycles 3-6.
I ran 3 more heat cycles on my R888 this past weekend. Temps were 90F and 85F for each day. I ran the pressures lower starting at 34 to 35 psi cold. Hot pressures were 41 to 43 psi. I also took tire temps, but a red flag during the first practice session meant temps were of limited value since I was sitting on track for 4 minutes before I came on.
Over all the tire feels softer at these hot pressures. They rolled over the side wall bit more, but never over the edge of rain groove in the tire. Based on data on construction I believe this is acceptable. Next track day I will experiment with still lower pressures and target 40 hot.
Speeds seem to improve and the gap between the RA-1 and R888 is smaller. By the 6th heat cycle I consider this not only 0.3 to 0.5 seconds. The R888 do require a different driving style as they do not take well to sliding. If you slide the R888 they will lose grip and lap time will increase.
I was able to take tire temps on Sunday back to back with the RA-1 and the temps were very similar and in many cases with in 5 degrees. The profiles across the surface were reasonable as well.
Here are some photographs of the tires after 5 and then 6 heat cycles. The tires were rotated in X pattern meaning LF when to RR as compared to the first 3 heat cycles. This means all 4 tires ran backwards this weekend. This was my pattern of use with RA-1s to even up the wear on each tire to maximize overall life.
Jim Foxx has record 14 heat cycles on a set of R888 and they still have tread depth and still have good grip.
Heat cycle data (Note PIR is most left hand and has a left hand oval just before the PIT in. This will bias tire temps and to a lesser degree pressures.
Heat Cycle 4 (Temps & pressures taken after redflag on track)
Pressure = 34 cold all 4 tires
LF = 42 Hot, Temps (O, M, I) 129,143,165
LR = 42 Hot, Temps (O, M, I) 132,158,163
RF= 43 Hot, Temps (O, M, I) 131, 154, 158
RR =44 Hot, Temps (O, M, I) 178, 176,162
Heat Cycle 5 (Pressures take in Paddock after session no temps)
Pressure = 35 cold on all 4 tires
LF = 41 Hot, Temps (O, M, I)
LR = 41 Hot, Temps (O, M, I)
RF= 41 Hot, Temps (O, M, I)
RR =43 Hot, Temps (O, M, I)
Photos After Heat Cycles 4 and 5
Left Front
http://members.rennlist.org/m758/HC5-LF.jpg
Left Rear
http://members.rennlist.org/m758/HC5-LR.jpg
Right Front
http://members.rennlist.org/m758/HC5-RF.jpg
Right Rear
http://members.rennlist.org/m758/HC5-RR.jpg
Heat Cycle 6 (Temps & pressures in paddock after “hot” cool down lap)
Pressure = 35 cold all 4 tires
LF = 43 Hot, Temps (O, M, I) 128,139,161
LR = 43 Hot, Temps (O, M, I) 129,153,164
RF= 43.5 Hot, Temps (O, M, I) 150, 163, 166
RR =43.5 Hot, Temps (O, M, I) 173, 179,171
RA-1 Temp data (Temps & pressures in paddock after “hot” cool down lap)
Pressure = 31.5 cold all 4 tires
LF = 39 Hot, Temps (O, M, I) 122,144,162
LR = 39 Hot, Temps (O, M, I) 137,169,156
RF= 40 Hot, Temps (O, M, I) 147, 161, 165
RR =40 Hot, Temps (O, M, I) 170, 177,171
Photos After Heat Cycles 6
Left Front
http://members.rennlist.org/m758/HC6-LF.jpg
Left Rear
http://members.rennlist.org/m758/HC6-LR.jpg
Right Front
http://members.rennlist.org/m758/HC6-RF.jpg
Right Rear
http://members.rennlist.org/m758/HC6-RR.jpg
I ran 3 more heat cycles on my R888 this past weekend. Temps were 90F and 85F for each day. I ran the pressures lower starting at 34 to 35 psi cold. Hot pressures were 41 to 43 psi. I also took tire temps, but a red flag during the first practice session meant temps were of limited value since I was sitting on track for 4 minutes before I came on.
Over all the tire feels softer at these hot pressures. They rolled over the side wall bit more, but never over the edge of rain groove in the tire. Based on data on construction I believe this is acceptable. Next track day I will experiment with still lower pressures and target 40 hot.
Speeds seem to improve and the gap between the RA-1 and R888 is smaller. By the 6th heat cycle I consider this not only 0.3 to 0.5 seconds. The R888 do require a different driving style as they do not take well to sliding. If you slide the R888 they will lose grip and lap time will increase.
I was able to take tire temps on Sunday back to back with the RA-1 and the temps were very similar and in many cases with in 5 degrees. The profiles across the surface were reasonable as well.
Here are some photographs of the tires after 5 and then 6 heat cycles. The tires were rotated in X pattern meaning LF when to RR as compared to the first 3 heat cycles. This means all 4 tires ran backwards this weekend. This was my pattern of use with RA-1s to even up the wear on each tire to maximize overall life.
Jim Foxx has record 14 heat cycles on a set of R888 and they still have tread depth and still have good grip.
Heat cycle data (Note PIR is most left hand and has a left hand oval just before the PIT in. This will bias tire temps and to a lesser degree pressures.
Heat Cycle 4 (Temps & pressures taken after redflag on track)
Pressure = 34 cold all 4 tires
LF = 42 Hot, Temps (O, M, I) 129,143,165
LR = 42 Hot, Temps (O, M, I) 132,158,163
RF= 43 Hot, Temps (O, M, I) 131, 154, 158
RR =44 Hot, Temps (O, M, I) 178, 176,162
Heat Cycle 5 (Pressures take in Paddock after session no temps)
Pressure = 35 cold on all 4 tires
LF = 41 Hot, Temps (O, M, I)
LR = 41 Hot, Temps (O, M, I)
RF= 41 Hot, Temps (O, M, I)
RR =43 Hot, Temps (O, M, I)
Photos After Heat Cycles 4 and 5
Left Front
http://members.rennlist.org/m758/HC5-LF.jpg
Left Rear
http://members.rennlist.org/m758/HC5-LR.jpg
Right Front
http://members.rennlist.org/m758/HC5-RF.jpg
Right Rear
http://members.rennlist.org/m758/HC5-RR.jpg
Heat Cycle 6 (Temps & pressures in paddock after “hot” cool down lap)
Pressure = 35 cold all 4 tires
LF = 43 Hot, Temps (O, M, I) 128,139,161
LR = 43 Hot, Temps (O, M, I) 129,153,164
RF= 43.5 Hot, Temps (O, M, I) 150, 163, 166
RR =43.5 Hot, Temps (O, M, I) 173, 179,171
RA-1 Temp data (Temps & pressures in paddock after “hot” cool down lap)
Pressure = 31.5 cold all 4 tires
LF = 39 Hot, Temps (O, M, I) 122,144,162
LR = 39 Hot, Temps (O, M, I) 137,169,156
RF= 40 Hot, Temps (O, M, I) 147, 161, 165
RR =40 Hot, Temps (O, M, I) 170, 177,171
Photos After Heat Cycles 6
Left Front
http://members.rennlist.org/m758/HC6-LF.jpg
Left Rear
http://members.rennlist.org/m758/HC6-LR.jpg
Right Front
http://members.rennlist.org/m758/HC6-RF.jpg
Right Rear
http://members.rennlist.org/m758/HC6-RR.jpg
10-09-2008, 05:19 PM
#33
Race Director
Thread Starter
What I can say is that at 6 heat cycles a shaved RA-1 was just getting into the fast range.
Looking closely at the lap time data from this weekend makes me think the difference in lap times between RA-1 and R888 is only 0.3 seconds at this point. That gap could easily close on 7th or 8 heat cycle.
10-09-2008, 11:16 PM
#34
Rennlist Member
Joe excellent data. I downloaded the tech info from Toyo. While I will be running the the 19 inch Toyo, next year I plan on doing some tire temp comparisons like you are doing hear. I read in the download like you stated in your post above that the R888 does not like the sliding driving style. that makes me sad as I have become accustom to sliding the car in turns and wonder how that is going to gel with this tire. Are you adjusting your driving style??
10-10-2008, 11:34 AM
#35
Race Director
Thread Starter
Frank,
I HAVE to adjust my drivng style. There is no other way. One of the important turns at PIR which we run quite alot is a 100 mph entry decreasing radius left with maybe 60 mph exit. On RA-1 you could get on brakes, toss the back end allowing the car to rotate to where you wanted it and get on the gas and go. It was the fast way around. Now with R888 you that once and then you flying off track in the next left hander since the right rear is overheated and greasy. You really need to work on keeping that rear end planted rather than sliding through that corner. Once you start sliding the grip just goes away and before long you will get passed. One practice session I ran with R888 I worked hard focusing on keeping the rear end planted. Ran some good lap times till I did a bit too much sliding.
So I need to work on technique. I may also need to change the set-up. Camber,sway bars, shock damping all may need to be adjusted to accout for the style change that I need to do. Right now I am just getting a handle on how to drive the tire so I have yet to understand what chassis adjustments need to be made. I do know that while balance is simiar on RA-1 and R888 it is not the same and may need to be adjusted to allow for the change in driving style as well as change in grip levels.
I just don't have skills to learn that fast enough right now. So more testing will be requried.
I HAVE to adjust my drivng style. There is no other way. One of the important turns at PIR which we run quite alot is a 100 mph entry decreasing radius left with maybe 60 mph exit. On RA-1 you could get on brakes, toss the back end allowing the car to rotate to where you wanted it and get on the gas and go. It was the fast way around. Now with R888 you that once and then you flying off track in the next left hander since the right rear is overheated and greasy. You really need to work on keeping that rear end planted rather than sliding through that corner. Once you start sliding the grip just goes away and before long you will get passed. One practice session I ran with R888 I worked hard focusing on keeping the rear end planted. Ran some good lap times till I did a bit too much sliding.
So I need to work on technique. I may also need to change the set-up. Camber,sway bars, shock damping all may need to be adjusted to accout for the style change that I need to do. Right now I am just getting a handle on how to drive the tire so I have yet to understand what chassis adjustments need to be made. I do know that while balance is simiar on RA-1 and R888 it is not the same and may need to be adjusted to allow for the change in driving style as well as change in grip levels.
I just don't have skills to learn that fast enough right now. So more testing will be requried.
10-10-2008, 02:46 PM
#36
Rennlist Member
dont you think those pressures are way too high? I think many of the WC T and GT teams are running 37 psi hot . (starting at 28 to 32 psi cold depending on if they are running Nitrogen or not)
It sure looks that way based on the temp spread as well.
It sure looks that way based on the temp spread as well.
10-10-2008, 04:59 PM
#37
Race Director
Thread Starter
Plus I see temps very close to RA-1 where I have been pretty confident in. I figure maybe try 40 hot and see how it works out.
What do you see?
10-12-2008, 07:22 PM
#38
Rennlist Member
Joe don't get discouraged. Soon you will not be able to buy the RA1 and allot of people will be doing what you are doing and rewriting the book on that tire. You are doing the right thing trying to put some science to the process. Next season, I hope to be doing the same thing. Just speculation on my part, but it appears that the R888 has either a bit softer compound in the rubber that is more susceptible to heat or something in the constructions that gets it hotter. It is not as much fun driving If I can't do a bit of sliding. Since the Nitto NT1 is supposed to be the same tire, are you allowed to use that tire in your class, if so, might be worth checking it out.
