ok, so ive heard that changing your wheel diameter will offset your odometer as in mph and rpm. so if i have an b18 and a gsr ecu in my eg with some civic wheels, the reading will be off, rather than if i used some integra wheels, right?

 

wrong

 

ttt

 

The engine has nothing to do with the reading. The tires will but if you are using the same tires that came stock with the car before the swap the reading will be the same, it is only when you get a bigger size tire like 18s or something that the reading will be off.

 

wheel diameter AND tire size is what throws it off
If youre running wheels with the proper size tires, the speed will be correct.
If your running something larger or smaller than a 185/65 (or similar ratio) on a 14" it will be incorrect.
Same goes for any other wheel size.
Thats why larger wheels have thinner tires (usually). Not only for clearance, but for correct instrumentation.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by pdiggitydogg &raquo;</TD></TR><TR><TD CLASS="quote">wheel diameter AND tire size is what throws it off
If youre running wheels with the proper size tires, the speed will be correct.
If your running something larger or smaller than a 185/65 (or similar ratio) on a 14" it will be incorrect.
Same goes for any other wheel size.
Thats why larger wheels have thinner tires (usually). Not only for clearance, but for correct instrumentation.</TD></TR></TABLE>

Correct

Examples... Pulled from discount tires website.

185/60/14

195/50/15 or 205/45/15 or 205/50/15

205/40//16 or 205/45/16 or 215/40/16

205/40/17 - tires (GOOD, not kumho's, nitto's or hankook's) starting to get expensive here (just for tires)

215/35/18 - Yoko Parada's 177.00 per tire

 

thnks

 

this will help you figure out what's going on

http://miata.net/garage/tirecalc.html

 

I've got a civic with 205/40/17s and my speedometer is off a couple of miles per hour for the better though...

Example
MY speedo says I'm doing 70 but I'm really doin' 67...