Wheels/tires for a chump car

[Blue55]

Hi Guys, this is my first post.

We are building an e30 to run in Chump Car. We will be running stock calipers and rotors, and stock springs. We can roll the fenders all we want and move the fenders out. We are running a stock motor.

We have some racing experience in a Nissan 240, but this is our first BMW build. We are looking to run a square setup with the most tire possible so that we can rotate wheels mid-race. Cost is also an issue as we cannot run expensive wheels. The treadwear rating must be 180 or higher

I've been looking at something like D-Force LTW5 15x7.0" ET25 wheels ($115) with a 225/45/15 tire as there are plenty of options like the RS3, Rival, and 1R1 which are relatively inexpensive in that size. ($120-$140).

Can I run a square setup like this without any rubbing issues? What about 15x8" rims. Are there good options?

Is it possible to squeeze a 245/40/17 like the NT05 onto this car with a square setup?

We're trying to do this on a budget and still somewhat confused about what the biggest square setup we can fit on the car is.

thanks guys!

[Emre]

The cheapest option would be NASCAR-style steel wheels. Since you're forced to run street tires, a tiny bit of sidewall stretch is actually helpful (makes transitions less sloppy). Get some 15x9" from Diamond, Bassett, etc. and put the 225/45/15 tires of your choice on them.

From my personal experience, I can tell you that 225 mm wide street tires on 7" wide wheels is a recipe for disaster. Turn-in is really mushy, which makes it difficult to hit your marks on the track. When I was running 15x7" wheels and street tires on my E30 track car, I actually found 205 mm gave me better performance than 225 mm.

As for tire choice, I'm a big fan of the Hankook R-S3. The Toyo R1R was a disaster for me on two cars: my E30 and my 190E Cosworth. Very uneven tire wear and lot of feathering/chunking. The old Azenis RT215 and 615 were ok for a few laps, but would geat greasy after 20 minutes, which is a real issue when running longer sessions. The newer RT615K is supposed to be better, but I havn't tried them. The Dunlop Direzzas are very popular. For me, I found they didn't grip as well in the dry or wet as the Hankook. But people love them.

[Blue55]

The cheapest option would be NASCAR-style steel wheels. Since you're forced to run street tires, a tiny bit of sidewall stretch is actually helpful (makes transitions less sloppy). Get some 15x9" from Diamond, Bassett, etc. and put the 225/45/15 tires of your choice on them.

From my personal experience, I can tell you that 225 mm wide street tires on 7" wide wheels is a recipe for disaster. Turn-in is really mushy, which makes it difficult to hit your marks on the track. When I was running 15x7" wheels and street tires on my E30 track car, I actually found 205 mm gave me better performance than 225 mm.

Emre - thanks for your suggestions, this is super helpful. I'm looking at NASCAR style wheels now. Do you think I would be able to run a 15x9 square setup with no rubbing? I can't use wheel spacers because they result in points in ChumpCar.

Do you think 15x8 would be too narrow for 225/45/15?

I'm a big fan of RS-3 as well as I've tracked them quite a bit in a heavy car, but I've never tried them for an enduro race.

[joey30]

225 isn't too narrow on 15x8. Its what I run at the track. I'd look at the TR Motorsports wheels...http://www.tirerack.com/wheels/Wheel...int&tab=wheels

They're good and inexpensive. My brother's chump car team runs 15x7 and 205 width Falken 615s on their car and seem to be real happy with them.

[Blue55]

225 isn't too narrow on 15x8. Its what I run at the track. I'd look at the TR Motorsports wheels...http://www.tirerack.com/wheels/Wheel...int&tab=wheels

Thanks! I've been looking at the TR Motorsports wheels as well. They seem like a good, inexpensive option. I think I can run 15x8 and 225/45/15 without rubbing from what I have read, but as Emre said we may be sacrificing turn in on a tire that wide. Personally I put a lot of value on turn in which improves precision and confidence. I assume there would be a decrease in overall levels of grip though.

[Emre]

15x9" is ideal, but 15x8" will still work well.

15x9" will fit on all corners as long as you roll the rear fender lips slightly.

[kronus]

We run 15x8 TRM C1s, 225/40R15 RS3s now and are happy with them. Previous to this, we ran 15x7 TRM C1s with 205/50R15 ZII star specs and were also happy with them.

[funcrew]

On a 15X8, make sure your offset is no more than +20. +25's rub on the strut with 225/45 AutoX tires.

[Blue55]

On a 15X8, make sure your offset is no more than +20. +25's rub on the strut with 225/45 AutoX tires.

Thanks guys. This is super helpful. I'm now looking at:

http://www.tirerack.com/wheels/WheelCloseUpServlet?target=runWheelSearch&initialPartNumber=K8R581LG&wheelMake=Kosei&wheelModel=K8R&wheelFinish=Light+Grey+Painted&autoMake=BMW&autoModel=2002&autoYear=1975&autoModClar=

15x8, +20 offset. I can get them at a good price and will run 225/45/15 RS3 on them.

[GillesBigCowboy]

Yes, those K8Rs look like a niiice choice.
I am thinking about the exact same setup for our next chump race.

[Blue55]

I've been shooting video of our build and I'm gonna put it all up on a Youtube channel in a few weeks. =) I'll post here when it's ready.

[Blue55]

Yes, those K8Rs look like a niiice choice.
I am thinking about the exact same setup for our next chump race.

Have you run RS3s in an enduro yet? I've only run them in HPDE sessions and they're great, but you can't overdrive them. I'm working on the assumption they are gonna grease out after a little while, but hold up until the end of a race.

[kronus]

I have. They held up decently for one 7.5+7 hour race, but got pretty greasy in the second one.

Star specs held up better and I like the way they break away more, but you can't get then in 225 and the total grip increase is better with RS3s.

[Axxe]

The key with RS-3 is pressure. When I get them greased up they really are only a few pounds too high, so once bled down it's business as usual. They fall off fast when hot and over pumped. The issue with a chump is then the next guy goes out who isn't as fast and the tires are too low for him. So I just back off once the tires get greasy and they come back within a lap or two, and then hold that as the pace. Lots of speed in RS-3's.

[Blue55]

I've found in 20 minute track sessions they perform optimally when you keep the pressure under about 38psi (at least on a heavy car). Suggestions for the e30 on pressure range?