Rolling On Bigger Wheels - Will It Affect My Speedo?

[G0DZLR]

just a question to everyone on the boards here whos upgraded their wheels to larger diameters than standard (id imagine most of you.

going from 15 to 17s, 18s even, obviously the mathematics are that the larger the diametre, the more chance the ratio will be out and my speedo will become inaccurate. will it be dependent on the profile of the tyres? say if i used my curretn overall diametre including tyres and then minus the diametre of the new rim, then add the remainng diametre to the profile the new tyres qwill be? im just not real sure and need some opinion from people whov done this before.

cheers

[QWK32]

yep, you got it. you try to get the overall diameter the same by using a smaller profile on bigger rims.

use a tire size calculator like this: http://www.miata.net/garage/tirecalc.html

it will tell you what the overall diameters are, also what you actual speedo reading will be with the new rims and tires at 100kph

[G0DZLR]

yep, you got it. you try to get the overall diameter the same by using a smaller profile on bigger rims.

use a tire size calculator like this: http://www.miata.net/garage/tirecalc.html

it will tell you what the overall diameters are, also what you actual speedo reading will be with the new rims and tires at 100kph

cheers for the link mate, exactly what i was after