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 see too much camber up front and too much pressue in the rear based off temps. Anybody see something different or am I correct? I'm not an expert, just guessing.

Thanks for the info Joe.

You can't really use the left side tires to determine temps. There reason is that they don't generate the same heat/wear patten due to the banked oval that makes up about 1/2 of the track. It will heat in the inside of the left front alot.

Notice also a near identical temp profile as compared to the RA-1's I have been using for 5 years at PIR.

Also the right rear takes a betting from sliding Turn 2. It was no big deal with the RA-1, but causes the R888 to lose grip. So I need to manage that corner with minimal sliding.

So Joe, as general rule, how much set-up (camber/caster) and air pressure adjustment do you do based on tire temps and temp distribution?

Well done data, Joe. I take it you're still running the RA-1 setup? Given our taller tires, I'm not sure we can get a way with the lesser camber for the R-888 that Toyo recommends. You wear looks fairly even, but remember that these tires often cord with some tread still showing (I'll have to take a picture of the one I have at home). They may be more worn than they look. I'd venture a guess that yours will cord in the center with the progression in wear in those pictures, but we'll see.

The R-888's don't tolerate abuse well wear-wise. We had a track that really unloads the inside rear tire, and one of our racers with a heavy right foot, and no LSD, corded a set of rears in his second weekend on them- it shredded down the middle.

Yes I am running the car 100% for RA-1's. No changes to the set-up other than air pressure. The overall balance is still there although the R888 tends torward more loose than the RA-1. I believe this is mostly due to turn 2 which is a 100 mph entry decreasing radius left. It is very easy to heat up the tire there.

Based on the tire temps I don't see changing the camber at least of for this track. This is not to say I won't make a change at some point, but for now all seems reasonable.

Now... Front camber... maybe I could pull some out. Hard to say for sure, but at most 0.5 degree. I run -3.5 now so maybe -3.0? Interestingly the fastest guy over the weekend consistantly on R888 was Darren Griffith. He ran some very nice times, but cord a R888 after 7-8 heat cycles. His reason was due to an alignement issue combined with not watching his tires. He was running -4.0 camber and could not get it out easily. It had to do with his camberplats and such. Anyway this caused his left front tire to cord on the INSIDE edge. This is not surpising due to the high wear on this inside due to dragging around th oval. Remember PIR is really alot like Gateway with a combined oval road course. Anyway I think the tire could been saved had he checked it sooner and rotated it to another spot on the car. Unfortunatley he only spotted it too late and the tire had a cord.


So I agree you can abuse the R888 the way we could the RA-1. In end I believe this is a critical point. The RA-1 was a very tough tire. It took little in the way of set-up to learn and no realy technique. In fact it was always perfect for hamfisted rookies. Well most of us got used to that abusive driving style on the RA-1 and need to relearn how to be smooth for R888. I know that to be fast on the R888 I need to be much smoother in the car than I was on RA-1. Otherwise I will overheat the tire and go slow. I do feel that in time we will figure out the R888, but since it involves more than just tire pressures and camber I think some drivers will respond to it better than others.

I hope here to remove the mystery of these tires and let the class know that they can work.