Up size tire

[turbomangt]

Goodyear dealer near me said that by going to a wider tire (215) I have to also lower the middle number (215-45-17) which I guess is the height ratio, has to do with clearence I guess. Does this make sense?

[IRPT]

Gary, yes that is correct, you want to keep your new tire size within plus or minus 3% of the OEM size in order to maintain correct odometer readings. Go to the links below and enter in different tire sizes, you will be able to see how they compare to the stock tire size. The first link gives you a visual representation or both front and side view of the differents between the two tires.

http://www.miata.net/garage/tirecalc.html

http://www.dakota-truck.net/TIRECALC/tirecalc.html

[redrum]

another item to be aware of is that the various manufacturers can have different tire heights when compared to an identically numbered tire from someone else. i have been looking for replacements for the stock treads and am suprised at the amount of difference in the tire O.D. between manufacturers. a good source of info on this is www.tirerack.com. another source would be the various mfg. websites.
i have gone into tire stores and put a couple of choices side-by-side to make sure the O.D. is the same. am bummed that "blue scorchers" are not available in an O.D. that matches the stock treads..
redrum
03 GT

[macster]

quote:Originally posted by turbomangt

Goodyear dealer near me said that by going to a wider tire (215) I have to also lower the middle number (215-45-17) which I guess is the height ratio, has to do with clearence I guess. Does this make sense?

turbomangt

215 is not wider but taller. Now having said that, you can run 215/50's on the stock GT rim. Jody and a few others here have successfully done it.


macster

[MichaelDay]

quote:Originally posted by macster

turbomangt

215 is not wider but taller. Now having said that, you can run 215/50's on the stock GT rim. Jody and a few others here have successfully done it.


macster

Actually the 215/50R17 is wider than the 205/50R17 by 10mm. It is also taller by 10mm x .5 = 5mm below the rim and 5mm above the rim. So the 205 is 8.07 inches wide with a sidewall height of 4.035 inches and an overall tire height of 25.07 inches while the 215 is 8.46 inches wide with a sidewall height of 4.23 inches and an overall tire height of 25.46 inches.

Going to a 215/45R17 would give the same 8.46 inch tire width but the sidewall height would be only 3.81 inches giving an overall tire height of 24.62 inches.

[SteelBlueGT]

Keep in mind that less sidewall height will also give you a somewhat harder ride (all else being equal) than a higher sidewall height! The key factor being that the sidewall deflection acts like a mini shock absorber!!