May 14, 2008 update to the Mazda STS2 Miata project car

Toyo vs. Bridgestone

STS2 Miata on the new surface at Driveway Austin
Testing at Driveway Austin
The soft Toyo grained quite a bit during our test

With a new season comes new equipment choices, as the aftermarket is never stagnant. In particular, new street tires are coming out all the time and this past winter has seen several new models that look to be perfect for autocross in the Street Touring category. Toyo has introduced a new tire called the R1R, which is being marketed heavily to SCCA members with a $100 rebate program and strong contingency program for National Tour events.

With that background, we decided it was time to test a set. The good news is that the tire is currently available in the same size (195/50-15) that we’ve been running in the venerable Bridgestone RE-01R. The Bridgestone is a wonderful tire, which works well in a variety of conditions on a variety of surfaces. It is responsive and grippy, and provides very long service life with little drop-off in performance throughout.

When our new Toyos arrived we noticed that the sidewalls were quite spongy when given the “squeeze test”. Furthermore, the tread surface area was also not very stiff when compared to the Bridgestone. This, in a tire that is marketed as having an “autocross-inspired carcass”. But the biggest difference was the compound: the Toyo was soft. Very soft.

To properly test the tires (all shaved to 3/32nds), we took our Miata to our favorite facility in Mineral Wells, TX. There, we did skid pad testing first, to establish baseline air pressures and to compare steady state grip. After that, we took to our standard test course (slalom, on-camber & off-camber sweepers, offsets) for a more comprehensive test. What we found was surprising.

First, we baselined with the Bridgestones at our customary pressures developed from a year of competition (34 lbs) and saw the following lap times:

Bridgestone 34 10.563 10.599 10.667 10.756 10.734

On went the Toyos and we immediately went a tad faster:

Toyo 28/34 10.407 10.536 10.582 10.512 10.501

Oops, but when we rechecked the air pressure, we had forgotten to air up the fronts, so we re-did that test at 34 all around:

Toyo 34 10.876 10.882 11.047 11.051 11.06

Hmmm…slower now. And the car is pushing a lot. Maybe those lower front pressures were better?

Toyo 30 11.079 11.123 10.624 10.411 10.383

Wow, better grip for sure. But it is hard to find the edge. The first couple of laps show this, then we locked onto it by the end. Let’s try lower still.

Toyo 27 10.195 10.123 10.142 10.152 10.041

Yowza! Now that’s really kickin’ it! Ok, so how low can we go?

Toyo 24 10.307 10.411 10.403 10.33 10.422

Well, I guess that there really is a limit. 24 is obviously too low. Let’s go back and repeat to verify.

Toyo 28 10.485 10.279 10.233 10.27 10.154

Good. So the Toyos like less air than the Bridgestones, at least on a Miata. But perhaps the course has gotten better as we’ve swept the line clean? Time to bracket our test against the Bridgestone:

Bridgestone 34 10.279 10.211 10.24 10.231 10.227

Hmmm…pretty consistent and a bit better than the first set, but still not quite as fast as the Toyo’s best. Let’s try a little less air in the Bridgestone just for fun.

Bridgestone 31 10.286 10.273 10.279 10.248 10.383

Nope, no help there.

Skidpad Conclusions: The Toyo had the best lap times in the 10.0-10.1 range, while the Bridgestone was consistently close at 10.2. But the Bridgestone was more consistent and easier to drive at the limit.

Ok, off to our test course. We’ll start with two sets on the Bridgestone to warm up and set good baselines:

Bridgestone 34 26.345 25.679 25.574 25.695 Bridgestone 34 25.621 25.908 25.461 25.893

On go the Toyos and…

Toyo 28 25.85 25.467 25.112 25.004 24.908

Wow. Significantly better. Time to bracket the test to verify surface consistency.

Bridgestone 34 25.558 25.47 25.221 25.483

A little better than earlier, but not much. So the Toyo wins the test course, as well.

Tthe ambient temperature throughout this test was around 65 degrees, so it was not the warmest of days. Also, Mineral Wells is a medium grip asphalt. We noticed that the tread on the Toyo was graining quite a bit and we wondered how the tires would fare on a stickier surface in warmer weather. Well, a warming trend was coming to Austin, TX, and we knew just the place to take advantage of it.

Driveway Austin is relatively new motorsports educational facility, which does the typical high performance driver’s ed types of course, but also does quite a bit of government work for EMT’s, DoD training and the like. While it is a road course, the turns on the short “old” course are similar to autocross turns, and the main straight can be pyloned down into a seven-cone slalom. With just a few cones, we get a great test course. Even better is that the entire surface has just been repaved in hi-tech polymer-based racetrack-grade asphalt. And this stuff is sticky! Combine that with a 95-degree day and we now have a test indicative of summer events around the country.

For our test procedure, we would spray down the tires after each run to get them back to optimal temps. Using our trusty MaxQData system, we divided the course into segments and put down “virtual beacons” so we could better analyze our results. Segment one was a 90-degree left, an offset and another 90 left. Segment two is the long slalom. Segment three is a big left 90 and a big offset, while segment four is a long left-hand sweeper into some tighter offsets.

We started on the Toyos for two runs and got this:

10.988 7.766 7.566 8.398 34.718 11.213 7.397 7.576 8.13 34.316

And now the Bridgestones:

11.554 7.02 7.686 8.208 34.468 10.866 7.567 7.428 8.062 33.923 11.03 7.452 7.567 7.95 33.999 11.29 7.254 7.528 7.799 33.871

And back to Toyo:

11.073 7.349 7.485 7.999 33.906 10.966 7.341 7.448 8.281 34.036 11.073 7.045 7.423 7.863 33.404

Conclusions for the second test: The Toyo had the single best run by far, but it was less consistent. It was also harder to drive quickly, especially through the slalom. Subjectively, the Toyo put power down better but made the car more pushy. It was also vague in feel due to the soft compound and carcass, though the rubber never got “tacky” like an R-compound. In short, each tire had its pros and cons.

Toyo will be coming out with more sizes later this season that will potentially change things up even more. There is a 205/50-15 which will provide more width at a slight gearing disadvantage. Even more interesting, though, is the 225/45-15 size which could easily be The Tire for 2008. Or not.

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wbjones
wbjones UltimaDork
11/12/14 7:22 a.m.

saw the title … was really looking forward to some new info … turns out this (for some reason) was just a 6 yr old info dump

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