<VV> Junkyard wheels

[Sethracer at aol.com]

_ricorvair at cox.net_ (mailto:ricorvair at cox.net)  writes:
 
What is  backspace?  I know its a stupid question, but at least I admit I 
don't  know.- Thanks.

 
So Seth  writes:



It is not a stupid question at all. A stupid question would be "What is  
offset?" Because there is no correct answer. Offset is, of course, a real  number 
- But "positive" and "negative" are "non-terms" - Like the Queen's  
proclamations in "Alice in Wonderland" those terms mean what the  speaker wants them to 
mean - and nothing more. Backspace, on the other hand is  ALWAYS an exact 
number, and always means the same thing- The distance from the  mounting pad of 
the wheel to the inner most point of the inboard wheel  flange.  It is also 
relatively easy to measure. 
 
>From a web site: 
 
The easiest way to measure backspace is to lay the wheel face down onto the  
ground so the backside of the wheel is facing up.  Take a straight edge and  
lay it diagonally across the inboard flange of the wheel. (Not on the  tire) 
Take a tape measure and measure the distance from where the straight  edge 
contacts the inboard flange to the hub mounting pad of the wheel.   This 
measurement is backspace.  
 
 
The wider the wheels get, the backspace will usually increase some. But the  
backspace is the best indicator of fit, because at some point, no matter what  
the offset or width of the wheel, an increase in backspace will cause the 
wheel  to contact the inner suspension of some kind. Most wider wheels add the  
additional width on the outside, after the backspace has reached it's 
mechanical  maximum (the suspension). That is why wide wheels are usuall really deep 
wheels.  An alternative is to rework the suspension to allow additional tire and 
wheel  clearance on the inside, usually an expensive exersize!
On the Corvair, there is a little bit of extra backspace available  when 
using 13" diameter wheels. (Larger backspace wheels often hit the steering  
components, depending on which steering arms the car has.) When you start  
increasing the wheel diameter, you can increase the backspace because there is  less to 
hit at that bigger diameter. - Seth  Emerson