question on 18" tire size?
The Tirerack lists height for all their tires. It's quite helpful. And yes, not all tires are created equal when it comes to diameter for a particular size. Like someone pointed out the diameter can be as much as 0.4". That's pretty significant.
Even better about the Tirerack site is they list tire weights. Same size tires can vary in weight by as much as 3lbs. That's significant. Many will be amazed at how much tires weigh too. A set of 225/45R18 weigh around 26-27lbs.
Adding shorter diameter tires will cause the speedo to read high and taller tires will do the opposite. Shorter tires will also change the gearing and your overall torque multiplication. A perfect and extreme example is my 225/50R15 drag radials which are 23.8" in diameter. I've run these tires at the track and the gearing of the car is completely changed. Instead of just tapping the rev limiter in 3rd with the stock 17s just as I pass the 1/4 marker, the DRs force me to shift well over 150' short of the finish line. This hurt my 1/4 times and MPH. I went from 14.4s@98mph on the 17s to 14.5s@96mph. As I passed the finish, the speedo said I was doing 110mph instead of 100mph.
Even better about the Tirerack site is they list tire weights. Same size tires can vary in weight by as much as 3lbs. That's significant. Many will be amazed at how much tires weigh too. A set of 225/45R18 weigh around 26-27lbs.
Adding shorter diameter tires will cause the speedo to read high and taller tires will do the opposite. Shorter tires will also change the gearing and your overall torque multiplication. A perfect and extreme example is my 225/50R15 drag radials which are 23.8" in diameter. I've run these tires at the track and the gearing of the car is completely changed. Instead of just tapping the rev limiter in 3rd with the stock 17s just as I pass the 1/4 marker, the DRs force me to shift well over 150' short of the finish line. This hurt my 1/4 times and MPH. I went from 14.4s@98mph on the 17s to 14.5s@96mph. As I passed the finish, the speedo said I was doing 110mph instead of 100mph.
Last edited by DaveB; Jul 20, 2005 at 11:45 PM.
so i went to the tire site sumitomotire.com and they had the chart for the tires i wanted HTR Z II and the closest size to match factory is 245/40 if someone could descibe what would would be different on the tire if i compared this tire to a 245/45 tire?
Originally Posted by 03silverG
so i went to the tire site sumitomotire.com and they had the chart for the tires i wanted HTR Z II and the closest size to match factory is 245/40 if someone could descibe what would would be different on the tire if i compared this tire to a 245/45 tire?
alright thanks for the help guys i think im going with 245/40 thats fairly close to the stock 17" tire, but will have a nice low profile to it without looking to small.
Originally Posted by 03silverG
so i went to the tire site sumitomotire.com and they had the chart for the tires i wanted HTR Z II and the closest size to match factory is 245/40 if someone could descibe what would would be different on the tire if i compared this tire to a 245/45 tire?
http://gs.tolan-hoechst.com/tirecalc.htm
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Originally Posted by Texasscout
as long as you get a tire with the same "rolling circumference", you should be fine. You may see a 1 to 2 mph difference, but not much.
KayGee56, yes it will change your speedo! It's the law of physics, smaller tire turns faster (more turns per mile) for a given road speed (speedo reads fast), larger tire turns slower (fewer turns per mile) for the same road speed (speedo reads slow).
KayGee56, yes it will change your speedo! It's the law of physics, smaller tire turns faster (more turns per mile) for a given road speed (speedo reads fast), larger tire turns slower (fewer turns per mile) for the same road speed (speedo reads slow).
touche
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