I recently got ahold of a set of 4 lug 15 in rims off of a chevy cobalt. I removed the 14 in 185 tires and replaced them with these rims with 195 tires. I believe this change has caused my speedo to be off. Any math majors out there that may be able to tell me what variance I am getting from stock setup. Also is there anything I can do to tune computer to account for this variance. Please Advise.
Tire Size Calculator - Tire & Wheel Plus Sizing
You can calculate a difference of speed by tire size
As long as it was a 195 50 15 tire there shouldn't be any change at all.
185/60r14 > (185/25.4)(.60 x 2)+14 = 22.75" diameter
195/60r14 > (195/25.4)(.60 x 2)+14 = 23.21" diameter
22.75/23.21 = 98.01 => @ 2% change in speed.
its a 15" wheel though...Originally Posted by petrified.rabbit
http://www.1010tires.com/Tools/Tire-...0R15/185-60R14
-6.08%difference
You never said the height of the tire, You only stated their width and rim size....
I wouldn't worry about tire differences on an Aveo. The percentage difference can't be much unless you lift it. I've got tires on my Aveo so big they rub every time I make full turns or hit bumps hard or when I'm out on the trail. 215/70r14... The speedo reads a perfect 65mph when my GPS says 70mph. I don't know what the math says it should say and I don't really care enough to search it up. My Toyota on 40's is off a bunch and my Chevy on 44's is off a whole bunch. After a week or 2 of driving you'll get used to the way they make the car feel and it'll feel normal again. Mine are super fat so It follows the road crown and wonders on bad roads. But it's fine. I forget their big tires till they grawl at me hahaha
Last edited by Lola; 07-19-2013 at 10:15 PM.
He said the width and aspect ratio...which it is very easy to determine the height from....
And a lift won't affect a speedo at all, I don't know where you are going with that...
Yeah that is a bit off. The factory 15" Aveo tires are Hankook Optimo 185/55/R15 which happen to be just about the only tires you find in that size. According to that website, the stock 15" are 1.18% "faster" than the 14", but when comparing my car to my GPS I find my speedo is FASTER than the GPS, so you can't always make a comparison like that...
Hmmm. Ok, I just read every post and Wayde never stated his Aspect Ratio. Just tire width and rim size. He asked 2 questions. How much variance will his tire change make, and about tuning the computer to adjust the speedo to read correct. We can only assume his aspect ratio or make guesses but all we know are his new tires are 10mm wider than his previous tires. I've got 215's on my car. It yanks into puddles hard and follows road crown a lot more that it used to with skinny's.
The point I made when I said you shouldn't worry much on an Aveo is that on my 04' with tires big enough that rub only read 5mph slower at 70. Unless you lift it to allow room for even larger tires which will than get you some slow speedo syndrome worth correcting. There isn't enough room in stock Aveo's to go tall enough to make it a concern worth fixing. In my opinion.
Last edited by Lola; 07-20-2013 at 04:13 AM.
^ahh ok the lift part makes sense now... and I guess he didn't post his aspect ratio lol... I must've just googled it for a cobalt
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