gracer7-rx7

iTrader: (16)

Planning out the wheel purchase for my race car FB. I'm also having difficulty understanding what the correct dimensions are.
Where can I buy a set of 15x7 4x110 steelies?
What is the correct "back spacing" and the SAE equivalent of 4x110?

Thanks.

YELLOWGSLSE

iTrader: (7)

Diamond Racing should have everything you need.

gracer7-rx7

iTrader: (16)

^what about

haven't been able to figure that out...

Carl

iTrader: (2)

4" back spacing is the way to go. I am not sure that anyone makes reasonably lightweight 15x7 steel wheels. I believe they are all pretty heavy. Diamond (I think) made/makes lightweight 13x7's that we favorites of the SoCal Pro7's.

Are you thinking of Chump-style racing? If so, you pretty much need 15" wheels. If you are planning on racing with DOT race tires I would stick with 13" wheels. They are lighter and more readily (kind of anyway) available. There are quite a few 13" race tires available. Generally they are cheaper than the 15's too.

Carl

Carl

iTrader: (2)

I have added spacer/adapters to my RX7 so that I can use Miata wheels. That way I can share race tires/wheels with my spec miata and also have cheap 15" wheels and tires for Chump-style.

Just got back from two days of endurance racing at Laguna Seca. The Falken 615K's look almost like new after 14 hours and several spins (by various team drivers including me).

Carl

gracer7-rx7

iTrader: (16)

it is indeed chump racing.

I thought you were using stock Miata 15x6 wheels? Those seem to go for $200-250 or more used which is about the same as just buying the steelies.

Is there any reason one approach would be better than the other?

Thanks.

Carl

iTrader: (2)

I am using the stock Miata 15x6 wheels for Chump racing. I think they work great. They are perfect for 205-50-15 street tires.

When I race the RX7 with SCCA though I use the same wheels/tires I use for the Spec Miata with SM7 Hoosiers. The 205-50-15 Hoosiers are noticeably wider than the same sized DOT street tire (and even wider than the same sized Toyo RR).

I recommend going with the spacer/adapters ($100 per pair) and the Miata 15x6 wheels. They will be way lighter than the steel wheels. We had a pair of diamond 15" wheels made and they were 17-19 lbs each compared with 13lb for the stock miata wheels. I actually have 3 pairs of adapters, two mounted on the car and one set as a spare mounted on spare front rotors. Makes changing during a Chump car race easier if a rotor goes bad.

Expanding this discussion, I recommend the Raybestos ST-43 pads for RX7 endurance racing. I have 18 hrs at Texas World Speedway, 14 at Willow Springs and 14 at Laguna Seca and the pads and rotors are still like new. They dont have the aggressive bite of Hawk Blues, but I do not think that is really helpful in an endurance race and definitely not with noobie drivers (as you might have in Chump). I actually have a set on my Spec Miata and they work OK. I am thinking that for sprint races though I would really like a little more bite for driving 10/10ths instead of 9.7/10ths in endurance.

I hope your carb work all came together.

Carl

gracer7-rx7

iTrader: (16)

Interesting.

Thanks for sharing your experience.

I was intending on using the ST-43 or perhaps even the Porterfield R4E. You are the second person I see recommending the ST-43 so I'll probably go that route. Especially since I was having a mental block figuring out what bolt patterns translate to 4x110 from inches. Getting old I guess...

Carl

iTrader: (2)

Yeah 4x110 doesn't translate to anything :-)

Carl

gracer7-rx7

iTrader: (16)

Got lucky tonight. Not THAT kind of lucky! Found a set of 15" NB Miata wheels cheap. Back to building.

mhr650

I have 6 15X7 Diamond steel wheels, and 6 15X7 Koenig Rewinds that I am no longer using. I can make you a great deal on them, but I would never consider running the Diamond wheels on anything again. The problem with the Diamond wheels is that the center hole is just rough stamped in the center piece and welded to the rim, once they get an order they drill the bolt pattern centered on the rim, but tire balancers use the center hole so the wheels aren’t centered on the balancer, it took as much as 9oz of weights to get some to balance and if you took the wheel off the balancer and put it back on it would be completely different depending on just how far off the wheel was now. As a workaround we took the center disk from an old 3 piece racing wheel and bolted it to the Diamond wheels and then used that to pilot on the balancer, but it still shook like a cement mixer. We had a race scheduled at Charlotte on the high banks and knew if it shook as bad as it had been we would be toast so we bit the bullet and got the Rewinds.

Now I am running adapters with 15X9 Miata wheels and 245-40-15 tires. It is way better but you have to make sure that you get pretty much everything right to clear the 245 tires.