October 02, 2010 11:05AM
Quote
Michiel 318iS
Ronal it is. How much is your speedo and odo off by having smaller tyres?

Use this calculator for the tire size you want...
[ejelta.com]
October 02, 2010 01:01PM
Great site, I'll even use it at work if it's correct:
October 02, 2010 01:14PM
I'm pretty sure it's accurate but you will have to factor in the 'optimistic' readings the car under test displays on the speedo.
October 02, 2010 04:04PM
We don't use speedo figures as a measurement, they're way to much off for that, we've got GPS equipment for that (not the stuff being used for navigation, it's way more sophisticated). Sometimes we need to accomplish a certain acceleration figure, which can be reached by playing a bit with the tyre sizes. I have lists for that, but not in such a nice way as the site you mentioned.



Edited 1 time(s). Last edit at 10/02/2010 04:05PM by Michiel 318iS.
October 02, 2010 05:35PM
Quote
Michiel 318iS
We don't use speedo figures as a measurement, they're way to much off for that, we've got GPS equipment for that (not the stuff being used for navigation, it's way more sophisticated). Sometimes we need to accomplish a certain acceleration figure, which can be reached by playing a bit with the tyre sizes. I have lists for that, but not in such a nice way as the site you mentioned.


Interesting... I always figured it by setting cruise control to 100mph and driving until a nice office volunteered to tell me how far off my speedo is. This isn't the way most people do it?

That tire calc I've seen around. It's one of those gems of the internet smiling smiley

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1989 - E30 - M20 - Manual. Approximately 270,000 miles
2000 - E46 - M52TUB28 - Manual. Approximately 110,000 miles

rkj
October 02, 2010 07:23PM
Quote
Michiel 318iS
Ronal it is. How much is your speedo and odo off by having smaller tyres?

I'm pretty sure it's five miles an hour; reads 50, actual is 45. I think our cars come with a 5 MPH error so mine probably is a little more than 5 confused smiley
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