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hmmm, I wonder if it is something like the R888’s stiffer sidewall needs a higher pressure to make the face of the tire be equally stiff, vs. a relatively floppy face of the tire interfacing with a stiff sidewall and wearing faster. Runs counter to what happens in a hoosier with stiff sidewalls though.
Interesting that we heard about this via the SM board vs. from the west coast!!!
bruce
Guys,
I have some information to report on thse R888’s that may be usefull to you.
I run a 944 spec car in Arizona and just cycled out my first set of R888. We use 225/50 R15 on 7" wheel. 2600lbs and 130-135 whp.
I would get consistantly 24-28 heat cycles from RA-1 (full tread or 4/32 shave). My first set of R888 got me 14.
Pressure… I ran hot pressures as high as 48 psi and as low as 39 psi. 39-40 psi hot producees much better grip and can approach the speed of a worn RA-1 (which were always fastest on therse cars).
The hot pressures did not produce a bad or scary tire, but it just does not have grip that it does at low pressures. My first set got even wear over the tire face and simply cycled out. It felt like an old RA-1 (hard and firm), but without the grip. I also have been working hard to limit sliding the car, but still find the tires go away 3-6 laps into a session. They drop off 0.5 to 1.0 seconds and don’t come back even if you back off. They do settle down after this however and are consistant, but just at slower pace.
Right now I am on my 2nd set also started full tread and have 6 heat cycles on them. My typical pressure gain is 7-8psi or so. I am running peak lap times at may be 0.5 second off track record for my class.
Ok I did some more tire testing this weekend at Mid Ohio. Basically I ran the whole of Saturday and morning practice on Sunday with my normal setup that is about 38 hot and the tires were fine. They started life as 4/32 tires they are set# 2 from my previous posts. They now have 3 races on them and about 10 cycles and still have life left. I would say they are still getting to their prime depth. Now Anthony Magagnoli was there doing his first race. He had brand new set of R888’s and did not heat cycle them. He ran the same hot pressures as me but was visibly sliding the car more during the races on Saturday. He had some serious graining problems on all tires, not just the left front which I get graining on sometimes. He also looked to have a groove of doom appearing. So for practice on Sunday morning Anthony who was already fast puts on some old RA1 scrubs and is noticeably faster. Enough that I had to try something for my tires. I had the set from Nationals in the truck that were set #3, started 3/32 4 heat cycles and 2 races. I had them pumped up to 40 because I wanted to try the higher pressures this weekend. I decided to go for broke in qualifying and try the higher pressures. The car did seem slightly faster but went away quickly in qualifying. I started them at 38-40 psi and I came back after a cool down lap and drive to the paddock and they were close to 47 hot so I backed them down to around 44.5 at that point for the race to try and get to 45-47 hot. In the race I was running good times, probably deceiving as the track was green from rain on Friday and was getting faster, but it seemed I was pretty even with Anthony on the RA1’s who I think would have been faster than me if I had stayed with my other setup. I did check the tire pressures after I had driven the car onto the trailer after the race and they were around 46 hot, so I still might have to fine tune my starting pressure. So long story short so far I like the higher pressures and the tires looked good from a wear stand point only 2 sessions but no graining. The tires did go off during the race but that happened also when I was running the lower pressures. The car felt like it was a little more nimple but would possible slide a little more, its kinda hard to explain but it did feel a little different and potentially a little looser. I’m going to continue with the high pressures and will report back after Putnam which is very hard on left fronts so it will be a good test.
Hello Simon
Thanks for the info, I am going to be getting a fresh set of 888’s soon not sure which way I am going to go on pressures…
I am proud to have started a thread that is 15 pages long…
Al
My 2 cents…
I tried 38psi cold for the PBOC sprint races at Barber. I don’t know if the car was any faster as I’ve not raced there before and had no previous times for comparison. I will say that the car felt better than it has on previous outings at Barber. I didn’t have an opportunity to get hot pressures or temps unfortunately. I’ll go with the “if it feels better, it probably is better” for now.
FARTBREF wrote:
[quote]I am going to be getting a fresh set of 888’s soon not sure which way I am going to go on pressures…
[/quote]
Al keep in mind that it sounds like the RA1 might be going back into production in just our sizes. I’m guessing you would prefer to run those if you had the choice. You might want to look into availability.
Here’s some more information - purportedly from Toyo (via SCCA Board member Howard Allen and distributed to the Club Racing Board and Spec Miata Advisory Committee).
Significantly lower pressures are recommended than the conventional wisdom…
http://www.nwspecmiata.com/SpecMiataSetupGuidelines.pdf
Steve D.
Disclaimer: Use at your own risk. May cause swelling, itchiness, rash, psoriasis, ringworm. Do not operate heavy machinery while taking this medication.
Steve D wrote:
[quote]Here’s some more information - purportedly from Toyo (via SCCA Board member Howard Allen and distributed to the Club Racing Board and Spec Miata Advisory Committee).
Significantly lower pressures are recommended than the conventional wisdom…
http://www.nwspecmiata.com/SpecMiataSetupGuidelines.pdf
Steve D.
Disclaimer: Use at your own risk. May cause swelling, itchiness, rash, psoriasis, ringworm. Do not operate heavy machinery while taking this medication.[/quote]
so, one can try 26 cold on LF and 38 cold on RF and see which way the car goes?
:S
csrow wrote:
[quote]one can try 26 cold on LF and 38 cold on RF and see which way the car goes?
:S[/quote]
Guess I have another pressure to try :unsure:
That is an interesting article. We ran 28psi on a brand new set of R888’s at the Feb CMP Enduro. There was almost no tread left in the center third of those tires after the race. Based on that article we should have run a bit less camber (the car has 3deg right now). I wonder if that might have helped with reducing center wear. Something else to try I guess…
NASA National sent the article to Toyo to see if it is legit info from Toyo - stay tuned.
bruce
jlevie wrote:
There are folks out there saying that the answer to the “groove of doom” is, unintuitively, higher pressures. Which is just one more assertion to mix into this stew.
Ranger wrote:
[quote]jlevie wrote:
There are folks out there saying that the answer to the “groove of doom” is, unintuitively, higher pressures. Which is just one more assertion to mix into this stew.[/quote]
That is why I tried 38psi at Barber. The point of that post is that I’ve run pressures very close to what was recommended in that article and experienced the “groove of doom”. Supposedly high pressure is the cure for that.
So on one hand we have a recommendation (supposedly from Toyo) that the tire should have low cold pressure and on the other hand we have empirical data saying that high pressure prevents center wear.
Ranger wrote:
[quote]jlevie wrote:
There are folks out there saying that the answer to the “groove of doom” is, unintuitively, higher pressures. Which is just one more assertion to mix into this stew.[/quote]
That article is very interesting as most of what they said is what some of us have already chosen to do. I know some went one way with tire pressures and others have gone the other way. I personally like the way the car feels with lower pressures. I had problems with the “groove of doom” when I tried to run the same setup as I had for the RA1’s.
I believe the “groove of doom” is a result of cupping due to extreme camber and not from lack of pressure. One way to fix the depression in the center of the tire is to increase the pressure. The other is to decrease the camber. It seems a lot of drivers have not adjusted their setup to accommodate the new tire. You will also need to make changes to your toe as the R888’s do not like toe out. To get the car to turn with the RA1’s we needed to run a lot of negative camber. With the R888’s this is not necessary. Try what you want but I think you will find that the higher pressures is not the answer.
Just my 2 cents on the subject.
Is anyone actually recording data or is all of this “seat of the pants” and “visual inspection”?
To really make any conclusions, you need to check the alignment, record the tire temps in the pits with a pyrometer, and check tire pressures, before going through a cool down lap, cruising into the paddock, unbelting, grabbing some water, etc.
TheRedBaron wrote:
[quote]Is anyone actually recording data or is all of this “seat of the pants” and “visual inspection”?
To really make any conclusions, you need to check the alignment, record the tire temps in the pits with a pyrometer, and check tire pressures, before going through a cool down lap, cruising into the paddock, unbelting, grabbing some water, etc.[/quote]
I have plenty of data to back up my suggestions.
The “Toyo document” recommends 2.5deg of camber and I run 3deg, which I don’t think is “extreme camber”, but I could be wrong about that. I also run zero toe, so I’m not so sure that what you are saying necessarily applies. CMP is rough on tires, but that much center wear in 3 hours with the shoulders showing relatively little wear suggest to me that there are things going on that I don’t understand. I really need to get hot pressures and temps as that might shed some light on what’s happening.
Might you share that data?
I have not tried running higher tire pressures so I cannot definitively say that lower tire pressures (32-38psi) are faster than higher ones (46-48psi). I have just figured out how to eliminate “the groove of doom” and run 1 second a lap faster without increasing tire pressures and instead decreasing camber and toe. I will try the higher tire pressures in the future as many people have seemed to like the way the car “feels” but until I have some time to actually “test” the higher tire pressures I’m going to stick with what works for me.
disclaimer: All of my testing was performed at VIR only. At a track such as Mid-Ohio that has a significant amount of sealer on it i’m sure the setup and tire pressures would need to be much different. Also any track with concrete is going to require a different setup as well. So summit should be interesting. I will still use tire pressures on the lower end of the scale but might adjust my camber and toe according to what the pyrometer reads after practice.
cheers,
It seems that we need to experiment more with the R888 to find the optimum camber. This is made more difficult by Toyo telling us that the inside of the tire should be hotter then the outside.
And we can expect to be using both R888’s and RA1’s this year because we either own both, or will soon own both. And that means that we might want to change our camber every time we change our tires. Sigh.
So Fred, and I have just bought one of the good camber gauges that fasten to the wheel rim, not hub, and is theoretically accurate to 0.1deg. We expect that trackside rental terms will be reasonable. $10, or help me change my motor .
jlevie wrote:
The “Toyo document” recommends 2.5deg of camber and I run 3deg, which I don’t think is “extreme camber”, but I could be wrong about that. I also run zero toe, so I’m not so sure that what you are saying necessarily applies. CMP is rough on tires, but that much center wear in 3 hours with the shoulders showing relatively little wear suggest to me that there are things going on that I don’t understand. I really need to get hot pressures and temps as that might shed some light on what’s happening.
Might you share that data?[/quote]
I would recommend running less camber. I think you will be pleased with the results. I was getting really high tire temps on the inside of the tire with the camber around -3.2 - -3.5. I backed the camber off about 1 degree and the temps were perfect with ~25 degree difference vs. the 60 degree difference before.
.com was running ~2.2 degrees of negative camber if I remember correctly when he won nationals. After seeing my tire temps I went down the same road.
I’m not handing out all my data but I’ll be happy to e-mail you the spreadsheet I use to record my data.
Hope this helps