ttal8

I'm considering getting larger wheesls and tires. The factory 17" with the bridgestone RE040's have a diameter of 25 inches. I was thinking about getting an 18" wheel with tires that are size 235/40x18. This would increase the diameter to 25.4 inches. Has anyone increased the tire diameter? Has anyone had any problems with rubbing and the bigger tires? Thanks for the info!

Jenner

<ul><li><a href="https://www.audiworld.com/forum/m.new/wheel">https://www.audiworld.com/forum/m.new/wheel</a</li></ul>

Colonel Bogey

<ul><li><a href="http://www.powerdog.com/tiresize.cgi">Powerdog</a></li></ul>

grishfish

do you also have to recalibrate the speedometer? How do you go about doing that?

I have 225/40/18 on my 18" wheels. I would consider going to the larger diameter just for the slight (I don't know how much) decrease in ride harshness.

JustJeff

decrease the aspect ratio of the tire, from say 40% to 35%, you decrease the amount of rubber between the wheel and the road, thereby *increasing* the harshness of the ride.
No squirm room.

grishfish

go from 225/40ZR18 to 235/40ZR18. That would slightly increase the overall diameter by 0.3 inches.

JustJeff

I see, boy, I don't think that's gonna make a huge diff. in the speedo, or ride.

Mike B

<ul><li><a href="http://www.miata.net/garage/tirecalc.html">http://www.miata.net/garage/tirecalc.html</a</li></ul>

FLVA

The spec. you want to know is Revs Per Mile, that makes it easy to compute speedo error.