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Old 11-14-2007, 03:54 PM
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oversize tires

Hey all,
I just bought a set of smoothies for my as yet to be delivered HHR. I want to get a set of tires for the rims. I believe the factory size is either 205-5516 or 215-5516 (not exactly sure of the size) anyway if I wanted to go to a wider tire say a 50 series and mantain the same tire height ( would the 50 series be too wide for the rims? the rim width is the same as factory 6 1/2 I think) what would the new size be? 245-5016, larger? Are there any cross reference charts out there that give the actual tire height?
Thanks,
-Patrick R
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Old 11-14-2007, 04:06 PM
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First of all, the 50 series you speak of is the aspect ratio. That's the percentage of the section width in millimeters. The stock 16" size is 215/55/R16. If you look @ tirerack.com they explain all of this in detail. Also, the have comparison charts for different sizes, giving overall diameter for each size. Very informative!
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Old 01-23-2008, 10:02 PM
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very good answer.
I just clicked on tire rack's site, which I have been to many times.

find a tire in the stock size, and look at it's "specs" link. Overall diameter is quite crucial...as is the section width.

then look at a "plus 0" size which means same size rim, different size tire. The first number is the tread's section width...the second number is the aspect ratio(a % of the width = the hight of the sidewall), and the third number is the wheel's O.D.(overall diameter)

so...a 215/50-17 has a tread width of 215mm. the aspect ratio is 50, meaning 50% of the tread width is the sidewall height, and the 17 is the wheel size.

select a 215/50-17
the look at a 225/50-17

you will find differences in load capacity, as well as overall diameter.

the two tires I looked at showed a O.D. of 25.5 for the 215/50 and the O.D. of a 225/50-17 is 25.9

therefore, a 225/50-17 tire has a O.D. that is .4 taller than the 215/50-17

that is measured without any load on the tire, inflated to specs, and set for 24 hours.

Now, if you load the tire(on the car, under weight) the O.D. will be reduced by 50% due to what is referred to as "static loaded radius"...the bottom half of the tire...the part that is actually under "load". The top half of the tire will not affect ride height because it has no load on it.

therefore, if the O.D. difference is advertised at .4, then the SLR or 'static loaded radius" is 1/2 that... or .2

so, a 225/50-17 is only .2 taller than a 215/50-17
it is also only 3/10" wider, which...isnt much.

hope that helps.

My next set of tires will most likely be a 225/50-17...larger footprint(3/10ths), but barely any taller, so fuel mileage, and final drive gearing wont be affected too much, if at all.
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Old 01-24-2008, 07:52 PM
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Got this from someone else here
http://www.miata.net/garage/tirecalc.html
Thanks to whoever it was
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Old 01-24-2008, 08:19 PM
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Originally Posted by FUTHRRE OWNER
Hey all,
I just bought a set of smoothies for my as yet to be delivered HHR. I want to get a set of tires for the rims. I believe the factory size is either 205-5516 or 215-5516 (not exactly sure of the size) anyway if I wanted to go to a wider tire say a 50 series and mantain the same tire height ( would the 50 series be too wide for the rims? the rim width is the same as factory 6 1/2 I think) what would the new size be? 245-5016, larger? Are there any cross reference charts out there that give the actual tire height?
Thanks,
-Patrick R
HI Patrick try out this site real easy to use www.scirocco.org/ just click on the word tires.What`s nice about this one is it has the stock fender clearance calculator so just insert that info then when you play with the different sizes you can see if it`s going to rub or not.
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Old 01-24-2008, 08:49 PM
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Excellent Post Smoke. Thank you. Even Mr. Michilen gives you a thumbs up on your post!!



Peace,

MWG2
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