RE: Wider tires on the front!

["Graydon D. Stuckey" <graydon@apollo.gmi.edu>]

On Sun, 3 Aug 1997, Brendan wrote:

> >the centre diff, but in this case, I was willing, at least for a while, to 
> >take that risk.
> 
> You think?  I'm certainly no expert, and haven't read up on this, but just
> thinking about it myself I would tend to disagree.  If what you are
> suggesting is true, that slightly different diameter tires front/rear
> causes more wear on the center diff, you are then concluding that anytime
> the front and rear travel at anything but the *exact* same speed, the
> result is extra wear on the center diff.  Let's think about that.  Assuming

That is true.  But obviously, the factory has designed the system to 
accept that much extra friction in stride.

> these things require the center diff to compensate for the front and rear
> wheels traveling at different speeds.  With this in mind, do you really
> think that a very slight difference in diameter between the front and rear
> is going to cause a measurable amount of increased wear on the center diff?
>  I can't see it, but I'd be interested in hearing from an expert on this. :)

Yes, having different sized tires will cause extra wear.   I don't think 
it is a huge amount, hence my decision to run with the different sized 
tires fro quite a while this past spring.   It is a significant amount 
extra though.  If the tires have 5% more circumference, then you'll end 
up with roughly 5% more friction in the centre diff.   The problem I 
didn't like was that when I locked the centre diff (for maximum traction 
on a drag race style launch) the dogs in the locker would not unlock 
without alot of screwing around in the parking lot.

So, yes, it does cause extra wear, but no, it isn't a whole lot.  It isn't
noticeable in regular street driving, but if you lock the centre diff, you
will have a hard time unlocking the diff. 


Later, 
Graydon D. Stuckey 
'89 Thunderbird SuperCoupe
'86 Audi 5000 CS Quattro
'86 Mazda RX7 GXL 2+2
'85 Mazda RX7 GS