[torsen] Re: [s-cars] Tire mix em up?

QSHIPQ at aol.com QSHIPQ at aol.com
Fri Oct 26 09:55:40 EDT 2001


I wouldn't mix an match tire sizes ever.  The torsen center diff has brass 
shims which are very heat sensitive.  Different tire sizes will bias the 
torsen to something other than the 50/50 it constantly hunts for.  This can 
lead to premature center diff failure.  

Mixing and matching tire compounds/size adds another variable into a 
complicated traction matrix of the center diff.  I'm not at all convinced 
that a 60/40r quattro will 'O' changing tire tractive abilities.  Remember, 
once you exceed the tractive ability of a tire and the rear driveshaft 
attempts to spin faster than the front, 56% of engine torque will shift to 
the opposing driveshaft, 78% of engine torque to the steering tires of a 
60/40 quattro doesn't at all sound like O to me.

Torsen equipped audis *can* oversteer.  But that is a moment in time, not a 
constant.  That would require a fixed split of something other than 50/50 
equilibrium the audi quattros center diff constantly tries to achieve.

Also, a rear tire with less tractive ability will also reduce the 
effectiveness of the rear braking ability.  Those with bigger brakes may not 
notice, but both bigger brakes and stock G60  will become less effective (or 
ar more likely to get overloaded sooner).

This isn't an area I'd mess with.  Keep tire size and compound constant.  
Change effective spring rates, ride height, and weight distribution.

My .02 

Scott Justusson

Derek writes:
only thing I can add to this thread is just be careful with the mix and 
match.  Depending on the characteristics of the tire, the handling/breakaway 
bias of your car can change accordingly.

I see the question coming up from time to time, how to make the quattros 
oversteer more...well there you have it.  That or deeper braking.

As it stands, I think I have one of those rare oversteering quattros.  
Change of rear toe helped some, but those rear tires of mine are terrible.  
Mildly put it can get um, interesting in the wet!

Derek Pulvino
"oversteering in seattle"

>From: jolly at zoomtown.com
>To: s-car-list at yahoogroups.com
>Subject: [s-cars] Tire mix em up?
>Date: Tue, 23 Oct 2001 01:04:04 -0000
>
>Hi,
>Unfortunately, I had some prankster(s) poke pinholes in my pass side
>sidewalls this weekend.  Which I did not "notice" for 2 miles driving-
>   boy can the tires get hot.
>
>I'm using 235/45/17 Yoko AVS Z4's  which is no longer being sold in
>that size.  So now I have 2 good tires which I cannot match.  Since I
>have a set of tires for summer/track, and this is street use only,
>i'm thinking of using another high-performance-All-season.  Any recs?
>Light snow for about 4weeks total/yr. in my locale.
>
>Jolly
>
>BTW I am assuming it is bad to have 2 sizes on the car at the same
>time.  Ie:  245/40/17 and 235/45/17 will affect the transmission, yes?
>



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