Grassroots Motorsports: The Hardcore Sports Car Magazine

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.

With everyone off to the Mitty, the Saab progress is going to stop for a few days. Here’s where we are at:

Almost all of the rust on the passenger side of the car, including the front and rear wheel wells, passenger door, trunk and battery tray, are fixed. There’s one spot on the inner fender near the tie rod that needs a patch, but that will be easier with the suspension arms and shocks out of the car, something we see happening a little later down the road.

There is a Centerforce clutch on the way to us. This will replace the oil soaked one in the car. We ordered and received a new rear main seal if that’s part of the problem in there.

Also, we’ve ordered another set of four Carroll Shelby rims. That gives us seven. Our goal is 11 of these wheels, six for rally tires and five for tarmac tires.

After we get back from the Mitty, we’ll probably have the clutch and get that done. That will allow us to take the car to the tag office and get it official-like. Next, we’ll work on the rust on the driver’s side of the car.

More later.

Our WRX was the only STU entrant in this weekend’s DeLand autocross. A win’s a win, but some competition would have been nice. The car does feel so much better with its new suspension. Look for the car at this weekend’s Mitty, too.

Bob Snodgrass, the owner of the Brumos Porsche dealership, passed away last night. His red, white and blue Porsches have been a staple of American sports car racing for decades, whether you’re talking the early-’70s 911 RSR or today’s Daytona Prototypes.

DC Williams wrote a nice piece about him on the Grand-Am site. Here’s the link: Grand-Am page

Honestly, I wish I could say that I knew Mr. Snodgrass that well, but we really only met a year or so ago. The affair was a slot car race in Jacksonville that was benefitting the Victory Junction Gang Camp. Brumos was also supporting the event, and team driver Hurley Haywood was also there. One of the Brumos cars was parked out front. I got my butt kicked, but at least the entry fee went to a good cause.

I saw him a few times since then, and the main subject was always the same: slot cars. He kept telling me to stop by and see his track, and I was always too busy to call him.

We’ve been continuing our rust repair work on the Saab 99. If nothing else, it’s a fun diversion while we wait for the clutch to get the car registered and back on the road.

This is what the trailing edge of the right rear wheel well looks like. Several small perforations around the lip. While we could just mud this up with some polyester filler, the repair wouldn’t last long with gravel being thrown from the tires on stage.

We used a wire wheel attachment on an angle grinder to remove paint and previous filler.

The paint and most of the rust is gone, but it’s not good enough to weld, yet.

A grinding disk does a better job of getting the metal ready for a weld.

A small piece of 20-gauge steel is tack welded to the area over the hole.

The piece is then completely welded down and the welds are ground nearly flush.

The repair continues around the mudflap mounting points. You can also see that the bottom of the trunk needs some work.

Before the trunk is repaired, the factory sound deadening and undercoating need to be removed. We used a propane torch to soften up the asphalt based goop.

A scraper was then used to scrape everything clean.

Skipping ahead, after the trunk welding, the metal was treated with POR-15s Metal Ready and a coat of POR-15 paint. Next, we’ll be using seam sealer to smooth over the joints and fill any pinholes.

Metal Ready and POR-15 were also used around the fender lips. The metal repair will provide a strong foundation for polyester filler on the outside of the fender and a strong mounting point for rally-strong polyethylene fender liners on the inside.

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

Our 2007 MINI Cooper S racked up another win this Sunday with Per at the wheel. Kim had some problems with those pesky cones.

Here are the results:
CFR DeLand Results

We’ve also done some testing comparing the new car to a well-prepped 2005 Cooper S. The results were quite surprising and will be published in an upcoming issue of the magazine.

In other news, we’ve started using Hoosier A6s on the car and will soon be comparing 17x7-inch Enkei wheels to our current 16x6.5-inch Rotas. The larger wheels can fit some pretty big (but tall) race rubber under the fenders, which might help our wheelspin issues. We’ve also begun to consider upgrading our shock absorber package.

We recently finished up our six-week trip to CA where we competed with good success in two National Tours, a Pro Solo and a regional event. But some of the best times we had were in-between competitions as we took a slow crawl up the Pacific Coast Highway (PCH) seeing the sights and stretching the legs of our dual-purpose STS2 Miata. Here’s some pics of just a few highlights.

The start of something very special

Our Miata takes a breather as we enjoy the view

Mulholland = miles and miles of twisty-turny mountain road

Stretching the Miata’s legs along the PCH near Big Sur

A classic PCH moment

After a long day of exercise, our Miata all settled in for the night

When home in Texas, our usual morning routine is to take the Miata out for a Starbucks along a nice twisty canyon road. Its only a couple mile drive, but it gets the juices flowing nicely (as does the caffeine). The Monday after our win at the El Toro Pro Solo found us at a campground right on the PCH where the Santa Monica Mountains meet the Pacific Ocean. In fact, we were right at the intersection of Mulholland Highway and the PCH. Perfect! Up early and feeling the need for a caffeine fix, the top came down on the Miata and off we went in search of coffee. Mulholland through the national forest is like a 90 minute autocross. Driving briskly, but carefully, we had a blast through turn after turn after turn after turn. Coming to the end of the paved portion, we found a Starbucks as we eyed up the morning parking lot on the nearby LA freeway. After a nice conversation with local Spec miata racer who spyed our Miata at the coffee shop, we were back off on the return trip. It was one of those glorius drives that is what sports cars are all about. 2+ hours of twisty-turny in a great-handling car with little traffic. It just doesn’t get much better than this.

Further up the coast we dropped the car a couple more times to drive along twisty sections of the PCH around San Simeon and Big Sur. Jaw-dropping scenery and perfect convertible weather made the days memorable as we decompressed from the race weekends. Through it all, our Miata performed flawlessly.

We always look forward to running at Atwater for two reasons. First, its a huge site laid up in clean, smooth concrete, which promotes big, fast courses. This year’s Tour courses were typical, with emphasis on large sweepers. Secondly, the San Francisco region knows how to put on a major event, and always exceeds expectations. For example, we were fed each day for free! Friday evening was a major buffet dinner, and each day of competition we had free lunch of sandwiches and sides.

The only downside this year was the weather. We had been in CA for six weeks to do the San Diego Tour, El Toro Pro and now this event, and had nary an inclement day. But nature made up for it by dumping rain on much of Saturday’s competition. We ran in the second heat and had a drying condition from rain in the first heat. We used this opportunity to try out our rain tires, a set of the Goodyear F1 GS-D3 in 215/45-16. These things were awesome, with very consistent breakaway that paid big dividends in driveability in the rain. We were wishing it would start raining again, they were that good!

As the track continued to dry, we switched back to our standard tires, the 205/40-16 Falkens that we had been running all year. In fact, its the same set, nearing the end of their useful life. Being slightly conservative on our single driest run, we were in second place after Saturday’s competition, with a 3 tenths deficit.

Sunday, Mother Nature played her cards again with some very strong winds throughout the day.
Ignoring that, we pulled out all the stops and really brought our A-game to the table, and took the win going away by just under 2 seconds.

There was some drama, though, as we did a NASCAR tire change before our final runs. There was a very fast section that led into a huge sweeping turn, which finally led into a tighter slalom. With our short 16″ Falkens, we were forced to shift to third to carry speed across the back of the course into the big sweeper. But there was no good place to downshift consistently without upsetting the car in the sweeper or the slalom. So we slappd on the taller 15″ tires for the staggered setup we had used some in Dixie, and that proved to be perfect to allow us to carry second acroos the back, bang the limiter a couple of times, and finesse the entire to both the big sweeper and then the slalom. Options are always good to have.

Next, we move back to the middle of the country for events in Arkansas and Texas. But before that, we have some exciting testing to do on the Bridgestone RE-01R in some new sizes that should work very well for our Miata and Civic. More on that in an upcoming entry.

Last week I came oh so close to seeing a girl get hit by a car. It happened right around the corner from my house. Two girls were walking down the sidewalk, and one was on a cell phone. Then the one on the phone just started walking into the street—-right into the path of a Toyota FJ. The Toyota driver blew the horn and came to a sudden stop. The girl gave him a “whatever” look and crossed the road.

Today I came home to work after we all went out for lunch. Margie said there were all kinds of emergency vehicles at the railroad crossing that’s outside my office. Looks like another car vs. driver incident, but this time the car won: news report