Re: Off-diameter tires

[STEADIRIC@aol.com]

>One of the tire companies (I forgot which one) has a web site (I 
>think it's Goodyear) that'll help you figure out what different tire 
>sizes will fit on a given size rim (15 X 6 in your example), and 
>tells you the overall diameter of the tire.  This info would probably 
>help you out a lot.  I don't know what diameter you're shooting for, 
>but on 6" wide rims you could probably fit 215, or maybe even 
>225/50R15 tires, which would give you a larger tire contact patch, 
>and a larger overall diameter that I suspect would be closer to what 
>you have now.  When you change the tire diameter (outer diameter, not 
>inside diameter) it not only changes the speedometer calibration, it 
>also changes the RPM range your engine works in.  A car that turns 
>2000 RPM at 60 MPH might spin at 3000 RPM at 60 MPH with a smaller 
>diameter tire.  I don't know what's involved in recalibrating an 
>Audi speedometer, though.

Whoa there Richard, But anyone putting a 225 on 6" rim is asking for BIG 
Problems, ESPECIALLY on a Audi with stock suspension.  Tire Squirm would 
not only make the car VERY Nervous but there is a very real possibility 
of Beading the tire. (Yanking it off the rim)  All the Tire Manufactures 
that I deal with Recomend a 7" wheel for a 225 as the narrowest that you 
mount.  As for the size a 225/50-15"s OD is 23.86", The Stock 205/60-15 
has a OD of 24.68" So the 225/50 is too small, It will not fit in the 
rear wheel wells anyway with out taking a Baseball bat to them and 
flaring them, Carefully!  As for changing the Overall Tire OD you need to 
be carefull that you don't change OD by more than +/- 5% you can screw up 
the ABS computer.  It has been programmed with a Tire OD that it use's in 
it's pump timing, Too short and the computer will not allow you to get 
near the threshold of lockup.  Too tall and it lets the wheels stay 
locked too long.

As for the 205/50's they are too short and exceed the +/-5% that is alowable.


Later!

Eric Fletcher
'87 5KCSTQIA2RSR2B

STEADI RIC@aol.com