Grassroots Motorsports: The Hardcore Sports Car Magazine

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.

STS2 Miata on the new surface at Driveway Austin

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.

Testing at Driveway Austin

The soft Toyo grained quite a bit during our test

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.

This past weekend saw us taking home our third SCCA NationalSeries victory in as many weekends, but it was anything but typical. Running in the fourth and final heat of each day with temps running in the 90’s, it was difficult to keep the driver cool and focused, much less the car and tires. And with C-Prepared running in our heat, there were copious amounts of gooey rubber being laid down which changed the feel of the track dramatically from what we had experienced during the Friday Test and Tune sessions.

After 10 national wins this year, its time for a break.

During Saturday’s competition runs, we adapted quickly to the changing surface improving our driving on each run. However, the heat was taking its toll on the brain as we started off the third and final run with the parking park set! There was a slight incline at the start and we had clicked it up to keep from rolling back while we awaited the “go” signal. It took until about halfway through the run where the course exited a slow 180 until it was clear that something was amiss. Reaching down and releasing the brake made the car rocket forward, but the time damage was already done.

Reviewing our MaxQData logs after the slower final lap showed that we ran the second half of the course 4 tenths faster than the previous run, but the first half was over a second slower. This allowed our competition to close in to within a half second on the first day, but it was reassuring to know that we could have run much faster save the mental error.

On Sunday, we decided to stay in the air conditioning of our tow vehicle most of the day, and even did so between runs. This kept us mentally fresh, and we were able to put down strong runs right from the beginning. Good thing too, because others in the class ran similar times to ours. In the end, though, the total margin of victory was a solid 8 tenths.

With 10 wins at National events this year out of 11 tries, and 11 Pro Solo victories in a row starting early last year, its time for a change. So we’ll be shelving the STS2 Miata for a bit and bringing out our STS Civic for the next round of Pro Solo events (Finger Lakes and Toledo). This also makes sense due to changes in the prize money offerings by Honda and the SCCA. Not to worry, though, as we have plans for the Miata.

[photo credit: Jeff Cashmore]

It was another week, and another NationalSeries win for our Miata. While it sounds very “ho-hum”, it was anything but as the competition was fierce this time. Indy region member Geoff Chambers used his local knowledge of the site and the course designer’s tendencies to put up a strong fight in his Miata, as did Ian Baker whose CRX prowess is well-known. After the first day, only a tenth of a second seperated each of the top three places.

Proper motivation is key at the start line

Our Miata diggin’ Peru’s amazingly grippy concrete

The second day’s course provided a more of a technical challenge, but still retained the sweeper-oriented flavor of the previous day. It also presented a setup choice for us, as the first section featured some quick sections where we’d run out of gear on our 15″ Bridgestones, but the back half of the course was full of slower corners that we’d need the shorter tires to dig out of. In the end, the trade-off seemed worth it, and we just banged the rev limiter a bunch on the first half. The other big challenge was getting used to the amazing level of grip provided by the Peru surface. We never pushed the car hard enough the first day, and only on our second run of the second day did we finally find the limits consistently. Doing so, we pulled out to a half-second lead which is where it ended.

The other setup note is that we did not initially run our normal concrete setup (more rear bar) because the car felt great during the Test and Tune runs on Friday. Given the sweeper-oriented nature of the competition courses, we *should* have gone back to those settings. It was only when we finally found the limits of the surface during competition that the dreaded steady-state understeer reared its head. For our final run on the second day we hooked the rear bar back up and dropped another tenth on the clock. More importantly, the car felt a LOT better. That one will go in the setup notebook for future reference.

Next up is Milwaukee for another National Tour against some of the same competitors. But this time its on medium grip asphalt and at a site that we struggled at last year. Hopefully, this will not be a repeat of San Diego…

We started our east coast national event swing with a traditional Pro Solo at FedEx field and took home a dominating victory in our STS2 Miata. As in El Toro, the two-course format at a large venue drew a sold-out field of strong drivers and we renewed our love for this unique format.

Workin’ the hills at DC

Having grown up in the area it was great to see some of our family and old friends, some still competing and others just stopping by to chat. But with 13 STS2 drivers in the hunt, including some majorly talented folks, we worked hard all weekend to bring our A-game to bear right from the get-go.

These were two of the best Pro Solo courses we have ever driven. Lee Piccione outdid himself in using elevation changes and undulations to provide two courses that looked a bit like each other, but drove completely differently. That doubled the challenge and made course-walking Friday evening a very focused affair. Apparently it worked, because we put down very strong runs right out of the box Saturday morning and matched them within a tenth every run each session thereafter. Only our final run of the competition on the left course was a significant improvement when we decided to risk a “Hail Mary” entry to the tricky final hillside slalom. Luckily we got it right, which cemented the class win and earned us third overall qualifier money. Unfortunately, that also sealed our fate for the Super Challenge as we were unable to match that performance in the hot afternoon temps, going out in the first round. It was a calculated choice since the Street Challenge money no longer exists, having been replaced by the Honda Tuner Challenge which our Miata is not eligible for. In short, the “bird in hand” was better than the “one in the bush”.

We again ran our Bridgestone RE-01R tires in the 195/50-15 size, which ended up suiting the courses perfectly. The lighter weight and better gearing helped the car accelerate up the hills, and we only barely touched the rev limiter at several spots on course.

We are now headed for Peru and Milwaukee for a pair of National Tours.

–Andy

[ photo by Team WTF?! ]

Sometimes the best competition experiences are born of adversity and such was the case at the SCCA National Tour in Huntsville this past weekend. Not that *we* had anything go wrong, but one of the other STS2 competitors had his car rendered inoperative as a result of his co-driver’s off-course excursion. And even though the car owner (Rick Cone) is one of the strongest drivers in the class, we immediately offered up a co-drive in our car. This changed everything since our car is better developed than most and we’d now be on completely equal footing. Not only that, but he would drive second, having the advantage of knowing where the bar was set.

Another STS2 win at Huntsville!

Got stickers?

Our entire mental outlook changed with the new arrangment. Rick was able to turn very fast raw times (some faster than ours), but coned away his fastest runs each day. Could he have done it cleanly? We’ll never know, but the experience made us bring out our A-game that we usually reserve for the National Championships in September. Lots of mental focus, and strong discipline in putting down fast clean runs.

In the end, we won by over a full second. Also, we scored first overall on the PAX index amongst all competitors at the event. A lot of the credit for that has to go to our new Bridgestones (we were on the new 195/50-15 size) since they have given an extra boost of performance to everyone who is running them.

Speaking of the good folks at Bridgestone, they were out in force with an 18-wheeler support vehicle and lots of knowledgeable staff. We took the opportunity to mount up a fresh set of full-tread RE-01R’s to use as rains and also on the street. We immediately noticed how the extra tread depth really improved the ride quality versus the shaved tires we run in dry competition.

We’ve got two weeks off now before the next leg of our national competition season (DC Pro, Peru Tour, Milwaukee Tour) begins. Time for a little R&R, some honey-do’s, and a few more development tweaks.

This past weekend in Houston brought us our third STS2 National Tour victory this year. It also gave us an opportunity to test and compare the performance of the two new sizes of our Bridgestone Potenza RE-01R tires.

Gridded up and ready to go in Houston

Before the event, we visited our friends at Soulspeed to mount up the 195/50-15 tires and then took them to a local parking lot to run some circles and put a heat cycle on them. The 205/45-16 tires that we ran on in our initial test session at Mineral Wells, and then competed on at Walnut Ridge were barely showing any wear despite having some 40 laps on them. We used the Test and Tune course at the Tour on Friday to do out comparisons. It consisted of a slalom with 63’ spacing, a crossover, a huge sweeper with camber changes, back through a crossover, and then a series of large offsets into the finish. This gave a good mix of transitional elements, steady state cornering, and acceleration zones.

After spending two hours on the course instructing others at the Cone Clinic, we were quite familiar with the layout. Given that, out first four runs on the 16” tires were extremely consistent, all at 26.6 seconds. Next we mounted up the 15’s and went back out to turn 26.7, 26.5, 26.3 & 26.4. Noting the better results, we went back to the 16’s to bracket the test and turned 26.4, 26.5 & 26.6. The 15’s were certainly no worse than the 16’s, and looked to be slightly faster. That said, the 15’s were fresher so there may have been an influence there. One good piece of news is that the two sizes had similar steering feel, so it will be easy to swap back and forth depending on desired gearing.

With testing done, it was on to the competition. The courses each day had a good mix of large sweepers, and transitional elements. Given the lower-grip surface, we had to disconnect our rear sway bar to stabilize the car and put power down. After the adjustment, the car was a dream to drive. Not only were we able to take the STS2 win by quite a large margin (3 seconds), we beat a strong STS class for a change. In fact, we finished 4th overall on the PAX index.

Next up is the Huntsville National Tour in two weeks.

Back when we first were building our STS2 Miata, we did a quickie install of a pair of Kirkey economy circle track seats, both for the additional driver support and for the weight savings. We had planned to go back and do a better job on the bracketry we built in between racing trips, but never got around to it. With the new season, a rule change has gone into effect which raises the minimum weight of replacement seats and adds the mounting bracketry into that weight calculation. This negates most of the weight savings from a seat replacement.

Our old CSP setup: stock Miata sliders modded to fit a kart seat

With the slider bolted in place, we tack-weld on two new cross braces

All welded up and painted

From the side you can see the angle of the seat mounting surface

Slider is bolted to the seat with hi-quality hardware

From the side shows just how close we got it

All bolted in place

Our initial response to the new regs was to put the stock passenger seat back in to make street driving cushier for our better half. We also threw 5 lbs worth of flooring tiles inside the seat bottom cushion on the driver’s race seat to make it legal, yet retain the awesome support it provides while competing. Today, we finally found the time to fabricate some proper bracketry that is much stronger than last year’s setup. And with the extra weight of the additional metal, we can legally remove the ballast shims.

The Kirkey seat is designed to be mounted either from the bottom or the sides. We chose to mount it from the bottom by modifying a set of original Miata seat sliders. These were leftover from our CSP days when they had a kart seat mounted to them and still had an extra cross brace attached. Our plan is to add two additional cross braces to form a box on which to mount the seat, and use two different thicknesses of material to incline the seat and clear the adjuster mechanism. For the front brace we use 3/4″ steel square tube and in the rear a piece of 3/4″ steel angle. After cutting to size, the rear brace is massaged with a grinder to form flats on either side which will fit it over the slider rails. The front brace requires no additional work.

With all of our pieces in hand, we bolt the rails into the car and proceed to tack-weld the two new braces into place. We’ve learned our lesson the hard way that welding can quite easily distort metal, but not when it’s held securely in place. A straightedge is then used to angle each brace slightly prior to welding so that the inclined seat will have a flat mounting surface. Once everything is solid and square, we remove the sliders and do the final welds out in the open where we can do a better job. Any screw-up here could mean injuries in the case of an accident. Satisfied with the coverage and penetration of our welds, we cover it all with a coat of black paint.

The next step is to drill mounting holes in the bracket to match those already in our seat bottom. A hand-held variable-speed drill makes quick work of that task, and we bolt everything together with some Grade 8 hardware we picked up earlier from the local Home Depot. After re-installing the seat cover, the whole unit is bolted back into the car using the stock attachment bolts/holes. Interestingly, we immediately notice a more solid feel to the whole assembly. Hopefully, we’ll never have to experience its ability to withstand the higher level forces of a sudden impact, but its nice to know that it can.

As you may recall from our early build-up entries last year, we have been balancing our brakes front/rear via staggered compounds. In the front we’ve been running some generic parts store pads and in the rear were Carbotech’s 913 compound. Well, as you can see from the first picture, our Carbotech’s have finally given up the ghost. Given that, we decided to try out some of Hawk’s products since they are big supporters of SCCA Pro Solo.

Our old, dead Carbotechs and a scored rotor

Hawk HP Plus pads and NAPA rotors

Vise grip and spare jack stand make the job much easier

Changing the rear brakes is relatively simple on the Miata, if you follow the factory service manual carefully. For example, make sure and back the piston out via the allen screw in the back of the caliper. Failure to do so can result in major badness (been there, done that, have a new caliper). Likewise, its also critical to re-adjust the piston position carefully after new pad installation as per the FSM, and then readjust it again after the brakes have worn in.

It’s also handy to use a vise grip to hold the pads in place while the spring clips are installed and the caliper lowered into position. Otherwise, it takes three hands. Use a spare jack stand to hold the caliper out of the way during this process and a lug nut to hold the rotor on the hub.

While we typically use OE Mazda parts only, we found good quality OE-spec rotors at NAPA for less than $15 each. That’s a LOT less than Mazda wanted.

We’ve been quite happy with the feel of the new combination, though we still have to heat up the rears to get them to bite early in the run. Driving up to the start line with the parking brake on does the trick. We’ll be trying some other Hawk compounds in the near future to try and avoid pre-heating.

Wearing our new Bridgestone Potenza RE-01R tires, we took another pair of STS2 victories at the National Tour and Pro Solo events at Walnut Ridge, AR. Due to low pre-registration numbers, both events were combined into one single weekend. The entire Tour was run this past Saturday, and the Pro Solo was run on Sunday. While it made for a hectic weekend, it was both enjoyable and successful for our Miata.

Baby’s got a new pair of shoes: Bridgestones

On Friday, we did some very informal tire testing by taking practice course runs on both our 205/50-15 Falkens and our new 205/45-16 Potenzas. The surface at Walnut Ridge is quite unique in that it’s old concrete that has a lot of exposed aggregate. Since the aggregate is mostly polished stones, hard street tires typically skate over the surface. Our Potenzas, being a bit softer than our Falkens, instead had a tendency to be able to get in and around the aggregate for more grip. As a result, the difference in performance of the two tires on the practice course was much larger than it was during our testing at Mineral Wells. Also, the practice course had a very large and long skid pad element, which played to the new tire’s strength (ultimate grip). Result? We were a full second faster on the Bridgestones!

Later, during the actual competition, the difference looked to be much less. We attribute this to the much higher percentage of transitional elements in the full courses, and the absence of significant steady state manuevers. This put the difference back to the 2-3 tenths margin we saw during testing earlier in the week. We’ll need many more data points to confirm these early conclusions, though.

Saturday morning at the Tour, we were able to eke out only a 2-tenths lead in the large class of 13 drivers. In the afternoon, however, we added another half-second to take the win comfortably. On Sunday, in the experimental “best of four runs” single-course Pro Solo, the margin of victory was 6 tenths. This makes 9 Pro Solo victories in a row for our project car!

Next up: the Houston National Tour, where we hope to do some comparison testing of the 16″ and 15″ Potenzas.

Testing tires at Mineral Wells

Some of the contestants begin to line up

Sure glad we bought that cordless impact gun!!

As mentioned in an earlier installment, Bridgestone has decided to once again support grassroots motorsports in a big way. In addition to tire purchase discounts to all SCCA members, they will also have on-site service at select events including the Solo Nationals and a contingency program. Most importantly, they are bringing two new sizes of their proven RE-01R tire to the states that will fit our STS2 Miata. These are 205/45-16 and 195/50-15. These two sizes are equal in external dimensions to the 205/40-16 and 205/50-15 Falken Azenis that we currently run. While retail sale of these new sizes is imminent, we were able to obtain early samples to do some testing.

Since Nationals is now held on asphalt, performance on that surface is the most interesting metric. We arranged to once again use the Mineral Wells Airport where we’ve done previous testing, since we have a standard test course painted down, as well as a large skid pad. We chose to test a fresh set of shaved RE-01R’s in the 205/45-16 size, against some fresh Falken RT615’s in the 205/50-15 size. This removes the gearing change from the test since these tires have the same outside measurements. Two of the Falkens were completely fresh, while the other two had several heat cycles on them. Conventional wisdom is that the Falkens work best after several heat cycles and we’ll test that concept, as well. All of these tires are on 7.5” wide, lightweight SSR rims.

Courtesy of STS2 competitor Neal Bellamy, we also have available a cycled-in set of 205/40-16 Falkens on 16x7.5” SSR’s for some of our testing. And finally, we have some old RT215 Falkens on 7” rims in 205/50-15.

Our test plan involves first using the skid pad to establish a pressure/performance curve for the new Bridgestones. We use tire temps and lap times to figure that out. With that data in hand, we move through each set of tires collecting similar data at the pressures we’ve previously determined to work best. After all of that is done, we move to the practice course to run some comparison laps. Here is all of the nitty-gritty:

Skid Pad (182’ diameter, ambient temps 65-75 degrees)

Data format: start psi, (F temp:out/mid/in) (R temp:out/mid/in) (lap1, 2, 3, 4) => end psi

Bridgestone RE-01R 205/45-16
1: 36 (126/126/106) (101/106/101) (11.013, 11.048, 11.104, 11.130) => 38
2: 41 (123/124/109) (100/102/097) (11.240, 11.271, 11.284, 11.217) => 41
3: 37 (136/139/126) (110/117/104) (10.997, 11.067, 11.074, 11.053) => 39
4: 36 (132/136/118) (103/108/100) (11.066, 11.203, 11.259, 11.337) => 37
5: 33 (127/134/121) (115/117/108) (11.163, 11.553, 11.635, 11.644) => 34
6: 37 (127/134/120) (109/116/106) (10.986, 11.103, 11.245, 11.188) => 38

Comments:
Set 1 baseline at 36 psi. Tires were at ambient temp to start.
Set 2 add 4 psi to existing pressure and performance drops by 1-2 tenths.
Set 3 drop 4 psi back out to bracket the test and performance is restored.
Set 4 drop another 3 psi and performance drops slightly. Tire gets squirmy.
Set 5 drop another 4 psi and performance drops even more.
Set 6 back to previous best to bracket the test and performance is restored.

Falken Azenis RT615 205/50-15 (F: fresh, R: cycled)
7: 36 (124/123/107) (104/104/095) (11.530, 11.622, 11.494, 11.355) => 37
8: 36 (133/130/116) (120/115/110) (11.323, 11.501, 11.482, 11.478) => 37

Set 7 baseline, tires at ambient. Squirmy feel, slow times.
Set 8 redo for test confidence. Slightly better times as tire warms

Falken Azenis RT615 205/50-15 (F: fresh, R: cycled)
9: 36 (135/130/118) (110/116/104) (11.221, 11.434, 11.345, 11.243) => 37

Set 9 swap front and rear tires. Performance improves with cycled tires in front.

Falken Azenis RT615 205/40-16
10: 36 (133/124/113) (104/101/096) (11.284, 11.335, 11.264, 11.310) => 39
11: 36 (143/141/130) (113/113/110) (11.343, 11.488, 11.424, 11.438) => 37

Set 10 baseline, tires somewhat warm from use on another car
Set 11 backup for confidence. Performance drops as front tires get too warm.

Falken Azenis RT215 205/50-15 (Front only, rear as above)
12: 36 (128/121/116) (115/105/100) (11.297, 11.420, 11.422, 11.399) => 37
13: 36 (142/138/133) (127/115/110) (11.207, 11.448, 11.397, 11.400) => 37

Set 12 baseline, tires at ambient
Set 13 backup for confidence. Similar results.

Skid Pad conclusions: Clearly the Bridgestone generates better numbers for basic lateral grip. Unlike the Falken, the RE01R is quite sensitive to pressures, requiring only a few psi off optimal to affect performance. The temperature pattern seemed unusual, in that lower pressures made the center temps go up and the outers down. Temps indicate that less camber may be needed.

Test course: (sweeper, 7 cone slalom, sweeper, offsets, 3-4 laps)

Falken RT615 205/50-15 @ 36 psi
1: 25.991, 26.208, 25.817, 25.393
2: 25.975, 26.031, 25.799, 25.603
3: 25.579, 25.733, 25.296, 25.535

Sets 1 & 2 are familiarization runs to establish rhythm for the course.
Set 3 is the focused test set.

Bridgestone RE-01R 205/45-16 @ 37 psi
4: 25.211, 25.104, 25.293, (timer failure on 4th lap)
5: 25.103, 25.716, 25.744

Set 4 is the test set
Set 5 was run immediately after set 4. Tires were extremely hot afterwards.

Falken RT615 205/50-15 @ 36 psi
6: 25.790, 25.694, 25.664, 25.618

Set 6 brackets the test and shows similar performance to the first set

Test Course Conclusions: The Bridgestone was quicker on the test course than the Falken by several tenths of a second. Overheating will hurt the RE01R’s performance, so temperature management will be critical.

We have additional electronic data acquisition information from the test course laps to process which should help us back up our driver’s impressions. In general, though, the Bridgestone’s strength seems to be basic ultimate grip. It is a bit vague in transitional elements, but holds on in a big way through steady state maneuvers. Transitional performance can likely be enhanced through suspension adjustments, though.

Two other interesting things we noticed: 1) The RE01R shows 2-3 pts softer at ambient temps on a durometer vs the fresh RT615. Also, its circumferential grooves are about 2/32nds deeper than the void area in the tread blocks. Shaving or wear to 2/32nds yields a virtual slick tread design.

Bridgestone clearly has winner on their hands and we will be committing to their use for this season for our Miata. We hope to test the 195/50-15 size in the very near future to determine which size is the best for our application.

Our new arrivals from Bridgestone

The 195’s stack taller than the 205’s!

195 is definitely shorter than the 205

But the 195 looks about the same width as the 205

205 vs Falken RT215

205 RE01R looks narrower than 15” RT615 Falken

195 RE01R looks wider than 16” RT615 Falken

Same size donut, different size hole