Kuntryboy865
New member
I got me some 16.7 sparco wheels, now im wondering if my speedmeter is off and how to fix it if it is.
they were 99 bucks and within my budget so lol.Wait....not 17" but 16.7"?
Use this calculator Tire Dimensions Made Simple - Discount Tire. Put in orig tire size, then new tire size, will tell you speed difference at various speeds if any. It won't be exact, all wheels/tires being slightly different, but it will give you a rough idea.
If it is off, I've heard that trifecta can adjust your tune to account for new tire size in the speedo. But I havent done it myself and can't say for sure if it is just something I think I remember, or something that actually existed on the interwebs.
Got a link to the ones you got? Curious about the size
16 x 7, I'm guessing.
Simple way to find out how far it's off. Download a free GPS speed app for your phone. Drive at a steady 65mph according to your speedo, and take note of what the GPS says.
If it's +/- 2mph, I'd just live with it. If you have a Trifecta tune, you can log, and send it in with the info. Tell them how fast your speedo says when GPS tells you you're doing 65mph, or vice versa.
Trifecta can. In case there is any doubt.
Laborsmith
If the tires you get/have are 24.9-25.1 inches tall, your speedo won't be off. The ideal size would be 205/55R16. That's the size that Sonics with the optional 16" wheels use.