GenVibe - Community for Pontiac Vibe Enthusiasts

Tire Size Calculator Click here

Here's another SPEED IN GEARS calculator that's working. It's loaded with GT specs. Easily changed. http://www.car-videos.com/tool...ulate

thanks for the post.... man that really helped out... told me that my 225/40/18's are almost the exact same size as my stocks... -0.8% it really dont get much closer than that

Quote, originally posted by faygolovinjuggalo »thanks for the post.... man that really helped out... told me that my 225/40/18's are almost the exact same size as my stocks... -0.8% it really dont get much closer than thatYou might also like 225/50/16 tiresGreat links BTW - especially the speed in gears. Thanks

That's pretty sweet... tells me that the 225/40-18 wheels/tires I'm lookin' at are nearly the same size as my stock 16s. That is very handy to know!

I re-calculated (Speed In Gears) for my 235/45/17 tires...that means if I could get to redline in 6th I'd be going 183 MPH!

Woah! There's nothing like jumping 3 years and 6 months to confuse a guy.

When using the tire size calculator, not sure if the math is being done correctly. In reviewing an explanation of tire sizes, the first number is width of tread, 2nd is hight of sidewall, and finally rim size. in putting in the stock vibe tire, and changing just the tread width to 275 (just messing around), it showed that my speedometer would show slower. to me that doesn't make sense. Just wanted to put that out there so people aren't relying on bad data.

screenshot of my results.

Attached files

The second number is the aspect ratio. It's in percent. 205 is the width in millimeters. The height of the tire from the rim to the tread is 55% of 205 or 112.75mm. A 275/55/16 would be 151.25mm high and being bigger would turn more slowly at 60mph and show up as slower on the speedometer which is calibrated for a 205/55/16 tire.

here's my results

This leads me to a question...If the factory size 16 is 205 55 16 &a factory 17 is 215 50 17...does that mean that my speedo is setup differently than a vibe with factory 16's?if so, then that would make sense on why I would go with a 235 40 18 instead of a 225 40 18...As you can see, the Diameter is off by 1/8" meaning I'll be traveling faster if the speedo's are the same...

this is a good thing

Keep in mind, many speedo's are designed to be reading 1-5% HIGHER than actual. You can check yours against a GPS. Thus, a taller tire may actually make your speedo MORE accurate than with the stock tire size. It also effectively raises the final drive ratio for possible MPG improvements. Again, any MPG comparison would need to take into account the speedo correction factor (GPS calibration) to be a correct comparison.

Here's another calculator that you can save to your PC and run from MS Excel or OpenOffice (www.filehippo.com)The offset worksheet is a draft, the tire size is pretty well tuned and gives you 4 tires to compare at the same time.

Attached files wheel_tirecalculator.xls (26.5 KB) 

Wow this is nice. But to some point, people does not normally compute the size of their car's tires.-------------------------------------------------------------------------------------wholesale parts