Here some information I found poking around Spec Miata web forums. Much was centered around a test SCCA did for Spec Miata
In the end, my only concern is that ALL of the drivers at the test gave the R888 the worst feedback of the three as far as driveability etc. Most said the turn in was great due to stiffer sidewalls but the compound wasn't as good as the sidewall construction and mid corner grip and predictability were not as good as the RA1 or the Hoosier. Is the R888 the right choice? I don't know... I think the cars will be harder to drive fast. In a class widely populated by relatively un experienced drivers... I don't think a tire that is hard to drive on is the best choice, but when you throw in all the other factors, it may have been the best decision. The sky isn't falling, we will have to get used to a new tire, but at the end of the day, we should all be fine with the R888.
Jim
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Jim Drago
East Street Auto Salvage
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2006-2007 Mid-West Division
Champion
EAST STREET RACING
Based on my experience so far with the R888 on an SM, it is a much more consistent tire than the RA1 - i.e. the laptimes are the same whether it's a new 4/32 shaved tire or a nearly worn out tire. It's fastest about in the middle of that lifespan, and it is only slightly faster at that point. Overall, I'd say it's consistency is similar to that of the Hoosier.
What we do not know yet (haven't had a chance to test yet,) is whether or not it's considerably faster at 2/32 shave. I certainly hope it's not.
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-Jason Saini :: Fort Worth, TX
-Team MER :: 2006 MX-5 Cup Runner Up
-2007 MX-5 Cup Champion!
From the Aim Tire Website...
There are a multitude of questions being asked about the difference between the RA-1 and the new R-888.
Our company was the very first company to sell the RA-1 back in 1992. In fact we were the company that originally tested a prototype RA-1 that allowed TOYO the feedback necessary to commit the RA-1 to the USA market. Thus, we have a bit of experience with the RA-1 tire!
The greatest difference between the RA-1 and the R-888 is the tires construction. The R-888 is of an all new design both in tread and construction.
The most obvious difference being the tread pattern and molded tread depth. The R-888 grooves are molded to 6/32nds of an inch. Whereas the RA-1 grooves are staggard with the inner grooves at 8/32nds of an inch and the outer most grooves at 6/32nds. Additionally the R-888 has less and larger tread blocks to promote a quicker steering response and better mid-corner grip.
It should be noted that shaving a R-888 due to the wider grooves will not ceate a 'slick tire' as in the case of shaving a RA-1 to below 4/32nds. The R-888 when shaved even as low as 2/32nds will not be a virtual slick tire but will continue to have wide rain grooves.
The wider grooves on the R-888 does enhance the wet weather performance of the tire and has proven superior in the wet than the RA-1.
To maximize the performance of the R-888 over the RA-1, especially on Front wheel drive RACE cars and Spec Miata's camber, tire pressure and driving technique must be modified.
The R-888 with the stiffer sidewall and softer undertread construction requires significantly less initial camber settings and higher pressure.
By design the R-888 promotes higher levels of grip under braking and at mid-corner.
So, if you simply switch out a RA-1 for a R-888 don't expect your FWD car to rotate in at mid-corner without taking all of the camber out of the rear suspension settings. Furthermore, less camber in the front will aid turn-in. And an increase in starting and operating pressure of the R-888 over the RA-1, will aid in overall traction and increase tire life.
I received information from Toyo on some of the differences of the RA1 and the R888.
The tire is not a bolt on and away you go replacement.
From Toyo Tire USA
The Toyo Proxes R888 is a totally redesigned product. The construction is completely different than the RA1. Therefore it may require a setup change.
The Proxes R888 is a more refined product that requires less slip angles and less camber than the Proxes RA1. If the R888 is driven with the same setup, tire pressures and driving style it may go slower.The Proxes R888 will not respond well if driven at the same slip angles as the RA1. For example if you slide your car around and build up to much heat the tire will wear prematurely. Toyo Tire USA
With that being said consider this.
High negative camber will give you more bite in the turns but has less contact patch straight ahead, so you have less braking force. With less negative camber braking points can be deeper.
All of the instructors I've talked to say "smooth is fast." Sliding scrubs off speed and overheats the tires. High tire temps should not exceed 200 degrees.
The new tread design of the Proxes R888 is less succeptable to tread squirm so shaving is less of an issue. But shaved tires are lighter so they have less rotating mass. The Proxes R888 has tread grooves full depth, so a 3/32 tire will still have some water channeling.
When I get more information I'll be sure to pass it on.
Joe
TheTireShoppe
Nothing definitive, but more information to put in our caps. I am also probing the Spec-E30 forums to see what I can learn.