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Tire Sizing

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Old 11-24-2001, 02:59 PM
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Tire Sizing

I always forget what each number means. Could somebody help? I know my tires are P235/55R16. Also, what is the best tire size for stock wheels? I know that in the new CHP they said the biggest you could fit on 16*9.5 rims are 255/55. I need some new tires and I'd like to get the best size for my stock rims. Oh yeah, and I do know that stock size is 16*8. Thanks guys.
Old 11-24-2001, 03:26 PM
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235 is the width (in millimeters) of the tire tread.
55 is the percentage of the overall height of the tire that the sidewall takes up and the 16 is the height of the wheel itself.

You can fit much wider than 255 on a 9.5 inch wheel, I've got 255 on my stock wheels. I might try 265 but thats probably pushing it.
Old 11-24-2001, 05:18 PM
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Whats the widest you can put on a 15x7 without the sidewalls sticking out too far?

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Old 11-24-2001, 07:58 PM
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If you have the stock wheels and want to use
Z/V rated tires, go with the stock size
245/50/16. Unless you want All/Season
tires stick with what you are now using.
Old 11-24-2001, 08:06 PM
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<font face="Verdana, Arial" size="2">Originally posted by iansane:
[B]235 is the width (in millimeters) of the tire tread.
55 is the percentage of the overall height of the tire that the sidewall takes up and the 16 is the height of the wheel itself.
[B]</font>
This is not 100% correct.


* The 235 is the width in millimeters as stated.
* The 55 is the sidewall height as a percentage of the WIDTH of the tire.
* The 16 is the rim diameter

Oh, and yes, you can definitely go wider than 255 on a 9.5" wide rim. I have 275 on mine..


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Old 11-27-2001, 11:46 PM
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Ok, I've got another question. I just got 245/50's all the way around. Someday I'd like to go bigger in the back, after total car mods are done. It will see mild strip action and autoX but will mainly be daily driver. What would be a good size for the back on stock wheels?
Old 11-28-2001, 12:35 AM
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I'd say 255's if you really want (on 16x8's) but no bigger... if you get any bulging on the sides its gonna hurt your cornering more than it helps... bulge is only acceptable for flat out drag racing.
Old 11-28-2001, 03:19 PM
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I didn't want too much bigger so I'd probably go with the 255's, now what would I want the sidewall to be, 255/what? Thanks.
Old 11-28-2001, 03:42 PM
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<font face="Verdana, Arial" size="2">Originally posted by duke_mushroom:
I didn't want too much bigger so I'd probably go with the 255's, now what would I want the sidewall to be, 255/what? Thanks.</font>
255-50-r16 is the closest you'll get to the stock height 245-50-r16. You can also go with a 265-45-r16, but the only things i'm aware of thay are made in that size are Kuhmo autocross/road race tires.
Old 11-29-2001, 01:50 PM
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Whats the widest I can get on mine? I currently have 245 50 R16's. I don't want to mess up the speedo, so I want to stick with 50's right?

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Old 11-29-2001, 02:10 PM
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To stay close to your stock size sidewall do a little math. Say you are going from a 225/70-15 tire to a 245/?/15 tire and you want to maintain ride height and not affect your speedometer. Well 225 x 70% = 157.5mm and 245 x 65% =159.25. That is treadwidth x sidewall percentage. Try to stay within 5-10mm to maintain stock setting. You can also use the same formulas in changing rim sizes. Convert the rim sizes say 15 inch and 16 inch into mm. A 15 inch rim is 381mm and a 16 is 406mm. So when going up to a 16 you would want to decrease the sidewall relative height by about 25mm or the inch difference. That is how you can go from a 70 series tire on a 15 inch rim to often a 50 series on a 16 rim. Remember it is all relative to the wheel width. Good Luck!

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Old 11-29-2001, 02:15 PM
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Goodyear recommends putting a 245 tire on a 7.5 inch rim. Remember the rim width will effect bead contact. You run the chance of breaking the bead and rolling the tire off the rim if you have too much "bulge". To put the large tire on the smaller rim you are pulling the rubber inward thus you have less bead contact on the rim.

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Old 11-29-2001, 02:46 PM
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Car: 1987 Camaro IROC Z28
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Here's a list of tire sizes with a very small speedo error (2% or less), or even 0 speedo error:

245-50-R16
255-50-R16
265-45-R16
275-45-R16
285-45-R16
295-40-R16

the real problem is finding tires in these sizes. a few of the sizes just aren't made, and a few are only made in autocross/road course tires. The only one readily available is the 255-50-r16.

Old 11-29-2001, 02:55 PM
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or if you're into drag only tires, the mickey thompson ET Streets have two offerings which are really good for thirdgens:
26" tall x 10.5 wide for 16" rim.
which is something like a 265-50, and
26" tall x 11.5 wide for 16" rim.
which is something like a 295-40.
Old 12-10-2006, 01:50 PM
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Is it possible to mount 295/50/16s on the stock rear 16x8 Iroc rims? In the tire's description, it says that it is safe to mount it to anywhere from 8-10 inches. Hmm... I am looking to put those on the rear and 215/50/16s on the front. Thanks.
Old 12-11-2006, 07:35 AM
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with all these wider tires...do you need to increase backspacing? add spacers? i've seen pictures of the old transam races and the road cars there have really fat rear tires! they look very cool!
Old 12-11-2006, 08:22 AM
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Maybe this link will help......
http://www.1010tires.com/TireSizeCalculator.asp
Old 12-11-2006, 09:37 PM
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blast from the past.. wow.

moving to (now) proper forum..
Old 12-11-2006, 09:39 PM
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Originally Posted by deadbird
blast from the past.. wow.

moving to (now) proper forum..
That's good, though. It means people are searching instead of asking the same thing over and over and over....
Thank You crazyrinningiroc! And
Welcome to TGO!
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