So, I've aquired some new wheels, Audi Pepperpots, and my current wheels are 14". Will the switch to 15" mean I need to recalibrate my speedo? The current tyres on the new wheels will not be staying, I will be looking at a lower profile tyre perhaps 45s not sure on width. Current tyres are 165/70/14.

I have searched this on here but didn't manage to find any results, other sites did offer some information though but I just wanted to see if anyone on here had any ideas. I'm not too fussed about the speedo being a couple of miles an hour slow but if it's an easy job to recalibrate it I will look into it.

Never heard of anyone recalibrating the speedo on a car, most people just live with it being inaccurate. Maybe check it against GPS once to see how far it is out?

use the calculator on this page clicky! and it'll tell you how far out your speedo will be with different wheel/tyre combos

Thanks for the guide mgavin01.

Tav, yeah I did think about hooking up the sat-nav and seeing what it read my speed as. So getting the speedo redone isn't really an option?

i always thought you are speedo stayed the same as when u get bigger wheels the profile of the tyre put on them is lower so the overall wheel + tyre diameter is the same, speedo will only be wrong surely if you put stretch's on or the similar. anyways i have big stretch on my 15's and have checked speedo against sat nav and only appears 7 mph more on the speedo than actual speed.

Edited 21 June, 200818 yr by smiffyraf1

The speedo is never 100% accurate, even from the factory theres still minor discrepancy. Theres always differences too, a smaller wheel with bigger profile wont be exactly the same, its very hard to work out, especially when there are different tyre sizes from the factory as standard. I'm sure its possible to get it recalibrated, but its not worth the effort if you figure out how far out you are.

Yeah, I've worked it out and the speedo would read about 4mph faster than actual speed so it's not too bad anyway.

Thanks for your help guys. :)

your speedo is probably out anyway now. mine is currently 5mph under actual speed so it would actually be more accurate with the bigger rims. However, if you get lower profile tyres which I'm sure you will the rolling radius will be the same. i have a set of 15s with 195/50s on them and they are the same as stock.

your speedo is probably out anyway now. mine is currently 5mph under actual speed so it would actually be more accurate with the bigger rims. However, if you get lower profile tyres which I'm sure you will the rolling radius will be the same. i have a set of 15s with 195/50s on them and they are the same as stock.

Yeah, I know that speedos are normally out, mine is 3mph under actual speed as standard. So getting say a 194/45/15 could have the same rolling radius as a 165/70/14? I'm not that knowledgable on rolling radius figures if you wouldn't mind explaining. I've read some guides but it's still not completely in my head.

Correct me if I'm wrong... but when you say mine is 4mph out are you using that online site?

cos if so thats only 4mph out at 70mph

it will be much less at say 30mph as its a percentage increase