Going from 235/55-18 to 255/45-18...
05-01-2012, 07:24 PM
#1
2nd Gear Member
Thread Starter
Join Date: Dec 2010
Location: Ca
Posts: 187
Going from 235/55-18 to 255/45-18...
I am almost ready to step up to getting some new wheels and tires. I'm looking at the charcoal AMR wheels and NITTO tire combo from AM in 18". I have 235/55-18 Pirellis on my stock 19" wheels and I wanted to stay with 19s but I wanted NITTOs more so it looks like I'll be switching to 18s. Will I have to recalibrate my speedo?
05-01-2012, 07:53 PM
#3
5th Gear Member
Join Date: Oct 2008
Location: CA
Posts: 2,073
how do you have 18" tires on 19" rims currently?
Did you mean you currently have 235/55R19 currently? if so, the tire height is about 29.18"
so the 255/45R18 will be about 27.04", or over 2" shorter, yes you will need to recalibrate. Are the stock 19's really a 55 sidewall?
Did you mean you currently have 235/55R19 currently? if so, the tire height is about 29.18"
so the 255/45R18 will be about 27.04", or over 2" shorter, yes you will need to recalibrate. Are the stock 19's really a 55 sidewall?
05-01-2012, 09:06 PM
#4
3rd Gear Member
Join Date: Apr 2006
Location: Owensboro Kentucky
Posts: 635
how do you have 18" tires on 19" rims currently?
Did you mean you currently have 235/55R19 currently? if so, the tire height is about 29.18"
so the 255/45R18 will be about 27.04", or over 2" shorter, yes you will need to recalibrate. Are the stock 19's really a 55 sidewall?
Did you mean you currently have 235/55R19 currently? if so, the tire height is about 29.18"
so the 255/45R18 will be about 27.04", or over 2" shorter, yes you will need to recalibrate. Are the stock 19's really a 55 sidewall?
05-02-2012, 01:06 AM
#7
2nd Gear Member
Thread Starter
Join Date: Dec 2010
Location: Ca
Posts: 187
So if I have 18" tires I must have 18" rims? Sonofabitch I've been swindled...Anyway, I guess I must have 18" rims. Will I need to recalibrate my speedo? I don't have a tuner and I don't really want to have to pick one up just yet.
05-02-2012, 02:30 AM
#8
5th Gear Member
Join Date: Oct 2008
Location: CA
Posts: 2,073
So, you're only about an inch off on the tire height, your speedo will be off by about 3.5% on the fast side (so when the speedo says you are doing 65, you will be doing more like 62.5... enough to justify tuning? only you can answer that.
05-02-2012, 06:05 AM
#9
6th Gear Member
You'll lose about 1.14" in tire OD and the speedo will read 65 MPH at 62.37 MPH (using one of the many, many online tire size calculators).
And how the heck do you NOT know what size tires you have and how does thinking about putting an 18" tire on a 19" wheel NOT light that little bulb ? LOL!
And how the heck do you NOT know what size tires you have and how does thinking about putting an 18" tire on a 19" wheel NOT light that little bulb ? LOL!
05-02-2012, 10:54 AM
#10
2nd Gear Member
Thread Starter
Join Date: Dec 2010
Location: Ca
Posts: 187
Well first, thanks for the calculations guys. Second, I know what size tires I have but I was told that I had 19" wheels so idk. I came from a wrangler where the only size that anyone cared about was the height. Is there a way to recalibrate the speedo without a tuner?