PaulMc

I know this has been covered many times before, but not recently and I have a memory like a sieve.

I am thinking of changing tyre sizes from 205/45/17 to 215/40/17. However, I dont' want the rolling radius to change (or must be minimal) will this idea work for me. What will the rolling diameter change from and to and how would this equate to a speedo reading.
What sizes will work if the above idea doesn't?

Thanks in advance.

Jim_B

iTrader: (1)

The change to the radius would be fairly small ( actually -1.95% ). You can find a few web sites around like http://www.tyresave.co.uk/tyresize.html that will allow you to calculate differences in diameter.

PaulMc

Thanks Jim, that's great. A useful website.

So how does a -1.95 or -12mm equate on the speedo?

markwild

try here

It actually gives the speedo difference, including a sample 60mph reading...

Mark

PaulMc

Thanks Mark. I'll I need to know is there.