M3 BMW wheels on a 69 Chevelle Questions.......

[chevyracer8262]

Hello every one I'm new to this site and so far I'm loving what I'm seeing and the info that I'm finding.... I have a few questions on the BMW wheel's, I have a buddy that has a set of BMW 18" x 8.5" AC Schnitzer Type III wheels with a 42mm offset that I can pickup for $300 with almost new tires... Has anyone put those type or a similar size wheel all around on a GM abody? If my maths correct those wheels should have a 6" backspace and I've got no idea if they'll fit the front of my car... Here's the setup I'm going with, tubular upper and lower control arms, 66 Chevelle Drum spindles w/C5 front disc brake conversion, the rear wheels I'm not worried about at all because I'm building a custom Ford 8.8 so I can adjust my rearend width to clear and sit like I want it to. My main concerns getting the fronts to fit...

Any information or suggestions is greatly appreciated,

Thanks

[Rhino]

If my maths correct those wheels should have a 6" backspace and I've got no idea if they'll fit the front of my car...
Offset is simply the distance from the true centerline of the wheel to the wheel mount surface. Positive offset places the wheel mount surface closer to the outside of the wheel; Negative to the inside.
You can approximately convert mm to inches by dividing by 25.4
Wheel width is typically measured from inside the wheel lips. Backspace is measured from the wheel mount surface to the most inside point of the wheel.
Wheel lip width varies from wheel to wheel, but .5" seems to be a close approximation.

Add this all together and it's pretty simple to convert offset to backspace. It can be approximated by the following:

backspace = (wheel width / 2)-(offset mm / 25.4) + .5"

I can't speak definitively on what backspace would fit your particular setup.
In addition to backspace there are a few other items to think about when using these wheels. There is a difference in bolt pattern (5 x 4.75in vs 5 x 120mm) It is a slight, but not completely insignificant difference. Most BMW wheels are hub centric, rather than lug centric so you'll also want to add ring spacers to accommodate the difference in wheel center bore. If you search you'll find an almost religious battle on whether or not it's safe to run in this fashion. I'll leave it to you to make an informed decision based upon your use case.

If using true wheel adaptors, rather than spacers, you avoid the above issues however it will at least double the cost of using those wheels.

[chevyracer8262]

ok thx for that input, I did a quick google search and found a pair of adapters 1.25" thk for $90+ship so that'll help with both the clearance and the bolt circle, as far as the rear goes i'm building a custom ford 8.8 rear so when I order my axles I'll just order with a 5 on 120 pattern. Anyone ever have any adverse effects from running wheel adapters? I've never ran any but have run 3/4" spacers on my old Camaro drag car.

[Rhino]

You'll find people who have had issues with wheel adaptors, however it typically involves improper assembly. I will mention you're likely to have much less issues with adaptors than spacers. I've also seen very portly cars (modern GTO's) being thrown about in autocross with an improper bolt pattern with no ill effects. I'd again reiterate that YMMV and everyone needs to make their own informed decisions and calculated risk.

I will mention for the moment my '68 is also riding on 5x120mm wheels without adaptors. I happened to get a smoking deal on a set of TSW's I couldn't pass on.
I'm not certain I'd trust it to a track day, however I feel that with the ARP wheels studs I'm running, and close monitoring I feel it's good until I do pick up a good set of forged wheels.

[csouth]

Hello every one I'm new to this site and so far I'm loving what I'm seeing and the info that I'm finding.... I have a few questions on the BMW wheel's, I have a buddy that has a set of BMW 18" x 8.5" AC Schnitzer Type III wheels with a 42mm offset that I can pickup for $300 with almost new tires... Has anyone put those type or a similar size wheel all around on a GM abody? If my maths correct those wheels should have a 6" backspace and I've got no idea if they'll fit the front of my car... Here's the setup I'm going with, tubular upper and lower control arms, 66 Chevelle Drum spindles w/C5 front disc brake conversion, the rear wheels I'm not worried about at all because I'm building a custom Ford 8.8 so I can adjust my rearend width to clear and sit like I want it to. My main concerns getting the fronts to fit...

Any information or suggestions is greatly appreciated,

Thanks


As far as the Ford 8.8, you might want to consider a GM 8.5 10 bolt. These are the same strength wise and you don't have to worry about getting the geometry setup right on spring perches and upper control arm mounts. If the brackets aren't setup right it will have and effect your suspension travel and proper pinion angle.


ok thx for that input, I did a quick google search and found a pair of adapters 1.25" thk for $90+ship so that'll help with both the clearance and the bolt circle, as far as the rear goes i'm building a custom ford 8.8 rear so when I order my axles I'll just order with a 5 on 120 pattern. Anyone ever have any adverse effects from running wheel adapters? I've never ran any but have run 3/4" spacers on my old Camaro drag car.

You might want to consider spending a little more and getting some hub centric adapters. This company could makes some the would be hub centric to the BMW wheel and your current hubs. I have nothing against spacers or adapters, I just prefer mine hub centric.

http://www.motorsport-tech.com/

Hope this helps....

[chevyracer8262]

Thx for the link I'll deffinatly be ordering my adapters from there. Not trying to come off like an ass but as far as the rearends go the 8.8 i'm building came factory with 31 splines, 3.73 gears, lsd, and disc brakes so it is stronger than the factory 8.5 10bolt stock vs stock, and can be built much stronger much cheaper than the 8.5, by time I get a good lsd, disc brake swap, c-clip eliminators and gears i'd have probably double what I'll have in building my 8.8 cause all I have to buy for it's axles, currie a-body housing brakets and the big bearing 9" housing ends and of coarse refurbish the junkyard disc brakes. Building a killer 8.8 that can handle all the abuse I could ever want to throw at it's only going to set me back about $650 cause I have a narrowing fixture and rearend fabrication table from where I built the gm 12bolt and full custom 9" prostreet rearends for some of my buddies... Oh by the way I have 3 8.8's (2-3.73 and 1-4.10 all 31spl w/lsd's w/disc brakes) and 2 gm 8.5's at my disposal and I prefer the 8.8