tesla

i just got 18in shelby rims and tires.. my Q's is i had 18" 235/50/18 from stock. new ones are P255/45R18 Goodyear Eagle F1 do i need to reprogram for the speedometer since they are bigger tires ?

hammeron

it's a good question tesla, i would use an
on-line tire calculator and figure the revs
per mile for each tire. if there is a difference
then update your pcm accordingly.

you can also use a hand held gps, to see how
your speedometer compares. if it's right on,
no need to do anything.

Chris07GT

there is less than a 1/4" difference in tire height between the two. I doubt your speedo will be affected much

tesla

ok thanks jus curious is all

candymanjl

this is a great tire size calculator...

http://www.discounttiredirect.com/di...foTireMath.jsp

I put in your sizes and it's only .21" difference in diameter between the two tire sizes. so on the old tire when you going 65mph on the new tire at the same RPM you'll be going 64.48mph. that's not enough of a difference to worry about.

Ken04

there's probably lots of these, but here's the tire size calculator I've always used; http://www.miata.net/garage/tirecalc.html

SirKnightTG

I plan on getting the CS69. I'd like to get the CS69 SE but they only come in 20". BAH!

onederful100

go with the 20's!!!

TPony

And were are those pics?

Mustangmike48

/Users/mbrady38/Desktop/000_0379.JPG

Man, I just bolted those wheels on last weekend but still can't figure out how to post a damn picture, can anyone help an old guy figure this out?