Kinda Dumb Question- Fuch Centers/BBS Shells

[jamesjedi]

Looking for a little guidance. Help is appreciated.

Car; 1977 911S, turbo flares.

Wheel Centers; machined Fuch centers.

Shells; BBS 20 hole.

If I have 4.75 back space using BBS shells, what would make a 11 inch wheel? I am guessing that I would need 6 inch. Which would make a 10.75???

Would it fit under my flares?


THANKS!

[gumba]

bbs halves come in .500" increments, so you would have 5.00" backspacing. A 5.00" back & 6.00" front give you a 11.00" wheel. To fit a 11.00" wheel you should have either a 6.00" or 6.500" backspacing. I think a 5.500" backspacing would also work, but a tight fit.
I prefer a little more backspacing, then use a small spacer to place the wheel in the wheel well where I want it. I find the flairs aren't always the same size so I end up using different spacers to get the wheel to outer lip distance the same.
I have turbo flairs on our '75 Carrera race car. I run either 11x15's (5.500" backspacing)w/295/40/15's, or 11x17" 3 pc Fuch w/6.00" back spacing) and 315/35/17's

[jamesjedi]

Thanks for the description. This helps me a great deal.

I just thought about... the beed to beed measurement. It is usually done form the inside of the beed.

This would mean that if I used 6 in. and 5 in. shells, the actual measurement from the outside beeds would be closer to 12 in.?

I assume BBS takes this into account?

[gumba]

You use the inside measurement as the reference. Measured inside to inside is a 11" wheel.

[mskala]

This would mean that if I used 6 in. and 5 in. shells, the actual measurement from the outside beeds would be closer to 12 in.?

You're right. It is roughly 1/2" for the lip of each shell.

Backspacing is obviously relative to the hub-mounting surface of your center.
I have fuchs-centered bbs wheels made off of old 6x16's but can't remember
where the hub-mounting surface is relative to the 20 mounting holes. However,
there are 3 choices anyway:
1) Mount the center on the back of the 2 shells
2) Mount the center on the front of the 2 shells
3) Mount the center between the 2 shells, increasing width about 1/2" and also
requiring sealant rather than the BBS wheel seals.

So determine the backspace you need and start from there.

[jamesjedi]

Just to clarify; The BBS shell that is called a 6 in. outer, is actually a little wider than 6 inches.

Thanks for the help. It is simple, just want to make sure.

MSKALA; is there a structurally "better" method of mounting when bolting together? It looks like a good way to make a better fit.

[mskala]

is there a structurally "better" method of mounting when bolting together? It looks like a good way to make a better fit.

I'm not the expert, but it seems like any of them will be equally strong for what
they are. Also I checked, at least on my centers, the hub is within a few
thousandths of the back side of the bolt face, making calculations easier.

[jamesjedi]

Thanks to all who replied!

I think I have it.