<VV> Big Rims

[Bryan Blackwell]

On Oct 3, 2006, at 2:41 PM, Padgett wrote:

> Now to maintain geometry the backspacing should be around 3.75" on a 
> 6" rim and 4" on a 6" rim.

No.  If you are seeking correct geometry then wider wheels require more 
backspace than that.  A stock Corvair car wheel is 5.5" wide and has 
about 4.25" BS.  Go to a 6" wide wheel and you'd need 4.5" to maintain 
the geometry (5" for a 7" wide rim).  However, a 13" wheel with more 
than stock BS will hit the suspension, so the '60s era racers put the 
additional width on the outside.  Most other applications with the GM 5 
on 4.75" pattern have less than optimal BS - usually around 4" - but 
will bolt onto a Corvair and work acceptably for most folks as long as 
the front tires aren't too wide.  However, a 15" diameter wheel that's 
6 or 7 inches wide can have correct backspace, will clear the 
suspension, and a 205/60-15 will fit without trimming *anything*.  The 
car will steer better since the contact patch is in the right place.

--Bryan