Speedometer Calibration

[gazza1602]

Hey all, I'm just about to replace my alloys with some Audi TT Competition alloys. They are the same diameter but slightly wider. Original alloys are 7J whilst the Audi ones are 7.5J. Therefore the tyres on the new ones will be larger. I was wondering if anyone knew how to recalibrate the speedometer? I'm assuming its not an electronic system due to the age and wondered if it was the old gear system? Hope this all makes sense.

Cheers,

Gaz

[gasketface]

i don't think you can recalibrate the speedo but you can use this to get an idea of tyre size you will need :- http://www.miata.net/garage/tirecalcold.html

[VW BUSH]

Only need to change it if the radius of the wheel is different to std.

[Bandit127]

Yes, use the same profile tyre with stretch or go lower profile in a wider tyre to maintain the same diameter (within 2%).

Both will keep your speedo accurate.

I haven't read any way to calibrate a Mk3 speedo. You only get that with a Mk4.

[Wayne]

205/40/17 tyres will keep the gearing / speedo close enough

[gazza1602]

cheers guys for all your help its been much appreciated. would the tyres at 205/40/17 fit okay on wheels that are 7j wide without too much stretching?

thanks again

Gaz

[Wayne]

cheers guys for all your help its been much appreciated. would the tyres at 205/40/17 fit okay on wheels that are 7j wide without too much stretching?

Yes fine, I ran them on 7.5 rims all ok.