R888 vs RA-1 Set-up from Toyo - For Spec Miata

[944-Spec#94]

I saw this came out for spec miata. The suprise is 32 psi hot.

 

http://www.nwspecmiata.com/SpecMiataSetupGuidelines.pdf

 

I have no idea how this applies to 944 spec. I have a feeling 32 psi hot is bad news for the sidewalls especially with reduced camber.

 

BTW..

SAE tire axis system

x: tractive (Forward/aft)

y: lateral (side to side)

z: normal (up/down)

[Sterling Doc]

This is interesting, again. There seems to be very little consensus on R-888 pressures. There also seems to be a gap between lab testing of "grip" versus real life experience. This seems consistant enough to beg for an explanation instead of just being written off to driver issues, or even completely explained by set up issues (or the set-up window is so small no one's found it yet).

 

What interests me is that the RA-1 gains significantly more traction when it is shaved than the R-888. I think there's not too much arguement that a full tread R-888 is likely faster than a full tread RA-1. I suspect that the RA-1's tread design allows further gains at around 2/32nds, when it becomes "slick like" The R-888 design does not do the same. I haven't seen any testing done at 2/32nds or less, but we all race there quite often, and with the RA-1's durability, for quite a while. My theory is the perforamce gap closes, and even swings in the RA-1's favor, at low tread depths. I think this is what explains the difference between the lab and race track, but I have no proof. I'd love to see lab testing done at 2/32nds & less to answer this, though!

 

I did run the R-888's at 28 PSI cold at Nationals - seemed to work pretty well for me, though turn in was not as sharp. I did not have any weird wear, but those tires were bought shaved for Nationals, and were pretty well done (worn about smooth across), though not corded after the 4 days Nationals (with some rain time). I'll have to experienment with pressures some more this year...

[944-Spec#94]

Eric, I think some of that data is very very good. It confirms some ideas of how the tire responds, but 32 psi hot seems scary low.

 

This past weekend I went out with 3.1 and 2.0 camber on my 944. This less than I had been running with RA1-1's. I once tried 3.0 with RA-1 and it just did not work. With R888 it seem ok. Then I made a sway bar adjustment and I could feel a major improvemnt. Lap times also dropped by a good deal. I was running 42 psi when I came off track for 3 of the 4 tires. One tire inside front was only 40 psi. The only issue was that I was starting to see a really bad wear patter developing where the tread rubber meets the sidewall rubber. It seemed like I was rolling over the edge a bit much. Now the car did run well so I decided to bump up pressures by 1 psi all the way around to reduce this effect. Next race was at night so I never really saw what the tires look like after and lap times were hard to judge at night since in the dark I never quite got the braking zones perfect.

 

Anyway this makes me very concerned about 32 psi hot in these tires.

 

So in some ways it adds information, but in other it contines the mystery since we have heard that Toyo says 2-4 psi more than RA-1, Toyo says 2-4 psi lower than RA-1, and Toyo says 32 psi for spec miata (we ran close to spec miata pressures on RA-1) and some guys even suggest 45+ psi hot. So what is the stroy on pressures?

[944-Spec#94]

Guys,

I have been doing quite a bit of scanning of other forums. Like spec miata, spec E30, Honda Challenge and American Iron.

 

So far the consistant things I can take from all these groups and looking at all the toyo "recommendations" is the following.

 

1) Tire pressures = 39-44 psi. This comes in at 2-4 lbs higher orginally recommended by Toyo

 

2) Less negative camber. Take some camber out as will help even the wear up over the width of the the tire

 

3) Shaving is not a big deal. The differene between shaved and not does exists, but is much less than that of the RA-1.

 

4) Anything over 12 heat cycles and still fast is a very good thing if you can do it. I suspect most cannot.

 

5) Once you change the camber you will also need to adjust the overall balance and driving style. Sliding around dirt track style is not good. Bottomline is if are sliding the car around you need to back down the pace and learn to not slide it. That could mean a change to technique or a change to setup to prevent the sliding.

 

6) R888 can be as fast as RA-1 over the course of a race. How you get there is different. If you just bolt them on and drive them like RA-1's you will be slower.

[philstireservice]

Guys,

I have been doing quite a bit of scanning of other forums. Like spec miata, spec E30, Honda Challenge and American Iron.

 

So far the consistant things I can take from all these groups and looking at all the toyo "recommendations" is the following.

 

1) Tire pressures = 39-44 psi. This comes in at 2-4 lbs higher orginally recommended by Toyo

 

2) Less negative camber. Take some camber out as will help even the wear up over the width of the the tire

 

3) Shaving is not a big deal. The differene between shaved and not does exists, but is much less than that of the RA-1.

 

4) Anything over 12 heat cycles and still fast is a very good thing if you can do it. I suspect most cannot.

 

5) Once you change the camber you will also need to adjust the overall balance and driving style. Sliding around dirt track style is not good. Bottomline is if are sliding the car around you need to back down the pace and learn to not slide it. That could mean a change to technique or a change to setup to prevent the sliding.

 

6) R888 can be as fast as RA-1 over the course of a race. How you get there is different. If you just bolt them on and drive them like RA-1's you will be slower.

 

 

Joe,

 

It's good to see someone doing his "due diligence"....

 

Tire pressure is sort of a personal choice to a degree. Physics tells you, the more pressure you run the less rolling resistance you will have. Hence the faster you will go, but with that said there are many other factors that will come into play. Along with that, driving style, which you already mentioned, will notably be the most important factor.

 

As far as tire shaving....Shaving a tire makes the tire "come in" sooner....

[Litespeeds]

There has to be some positive effects for removing a pound or two of rubber from each corner of your car due to the decrease in unsprung weight. Braking and handling should definitely be better.

[philstireservice]

removing 1lb of weight from the tire/wheel (unsprung weight/rotating mass) area is like taking 20lbs out of the car.