# stretched tires...does it lower overall diameter of the wheel???



## turbott920 (Nov 13, 2007)

ok, I have a little debate going with a guy and he says no matter how much you stretch a tire the tire will always maintain it's original *overall* diameter. I say, for instance, if you have a 215/35/19 on a 19x9.5 and a 215/35/19 on a 19x7.5 there will be a slight difference between the two in overall diameter due to the stretching. Anyone chime in with your thoughts.


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## Travy (Jan 13, 2004)

*Re: stretched tires...does it lower overall diameter of the wheel??? (turbott920)*


_Quote, originally posted by *turbott920* »_Anyone chime in with your thoughts.

Go back to the TT forum and continute your argument with Calvin in that thread


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## shimmy2244 (Nov 20, 2006)

*Re: stretched tires...does it lower overall diameter of the wheel??? (turbott920)*

IB4TL
Why are you even debating this with someone? What does common sense tell you? That should be enough to just "leave it alone."


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## ocdpvw (Jul 19, 2005)

*Re: stretched tires...does it lower overall diameter of the wheel??? (shimmy2244)*

your answer is yes


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## Bazmcc (Jan 11, 2005)

*Re: stretched tires...does it lower overall diameter of the wheel??? (ocdpvw)*


_Quote, originally posted by *ocdpvw* »_your answer is yes









x2 http://****************.com/smile/emthup.gif 
to even it out you put a taller sidewall on the wider rim.


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## tmvw (Jan 14, 2008)

*Re: stretched tires...does it lower overall diameter of the wheel??? (Bazmcc)*


_Quote, originally posted by *turbott920* »_
I realize the actual sidewall size is still going to be the same (the tire doesn't magically change what size it is from stretching it) but the rolling diameter (what the whole topic is about) would be different. the profile would be lower.


no, the rolling diameter would NOT change either. it's really not as hard as you make it out to be. now i do not know the exact equation to calculate rolling diameter by hand, but if i did, i would show you. use that link i showed you... 24.9" rolling diameter on a 215.35.19 wheel, will still be 24.9, on a 8" or a 10" wheel. 
like i said, it will APPEAR/LOOK/SEEM different, but math does NOT lie

stretching does NOT lower it's profile. as i said, i wish i had the exact equation on how you calculate rolling diameter by hand... that would be the easiest way to show you how math does not lie lol
a 215/35/19 tire is STILL 24.9 inches rolling diameter, regardless of what width of wheel it is mounted on.

*are you really trying to argue how something LOOKS versus a mathematics reason?*
here's the link that shows you how to calculate rolling diameter:

http://www.tirerack.com/tires/...width
"To figure the outside diameter of a tire, take the sidewall height and multiply by 2,(remember that the diameter is made up of 2 sidewalls, the one above the wheel, and the one below the wheel) and add the diameter of the wheel to get your answer."
"Width x Aspect Ratio = Section Height
Section Height x 2 = Combined Section Height
Combined Section Height + Wheel Diameter = Tire Diameter
Example: 185/60R14 85H or 185/60HR14
185mm x .60=111mm
111mm x 2=222mm
222mm + 355.6mm(14")= 577.6mm or 22.74" "

found a basis to my claim:
"The width of a tire mounted on a narrow rim would be "narrower" than if the same tire was mounted on a wide rim. NOTE: because the overall diameter of a steel belted radial is determined by the steel belts, there is little, if any, change to the overall diameter of the tire due to differences in rim width."
http://www.tirerack.com/tires/...width


_Modified by tmvw at 9:57 AM 5-27-2008_


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## ocdpvw (Jul 19, 2005)

*Re: stretched tires...does it lower overall diameter of the wheel??? (ocdpvw)*

thats why i always stick to 225/*45*/17 when everyone says to run 40 series. also even in the fronts i run 205/45/17 on 8.5 to help with the over all diameter. its still off by 5mph, but closer then what 40 series would be.


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## tmvw (Jan 14, 2008)

*Re: stretched tires...does it lower overall diameter of the wheel??? (ocdpvw)*

found a basis to my claim:
"The width of a tire mounted on a narrow rim would be "narrower" than if the same tire was mounted on a wide rim. *NOTE: because the overall diameter of a steel belted radial is determined by the steel belts, there is little, if any, change to the overall diameter of the tire due to differences in rim width.*"
http://www.tirerack.com/tires/...width


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## JDriver1.8t (May 20, 2005)

*Re: stretched tires...does it lower overall diameter of the wheel??? (tmvw)*

Math also says that a sidewall that is vertical will have a large vertical component than a sidewall that is at 30 degrees stretched in.


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## tmvw (Jan 14, 2008)

*Re: stretched tires...does it lower overall diameter of the wheel??? (JDriver1.8t)*


_Quote, originally posted by *JDriver1.8t* »_Math also says that a sidewall that is vertical will have a large vertical component than a sidewall that is at 30 degrees stretched in.


_Quote, originally posted by *tmvw* »_found a basis to my claim:
"The width of a tire mounted on a narrow rim would be "narrower" than if the same tire was mounted on a wide rim. *NOTE: because the overall diameter of a steel belted radial is determined by the steel belts, there is little, if any, change to the overall diameter of the tire due to differences in rim width.*"


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## JDriver1.8t (May 20, 2005)

*Re: stretched tires...does it lower overall diameter of the wheel??? (tmvw)*

So the sidewall gets taller? There *has* to be an affect from stretching. Also, manufacturers don't account for stretching beyond thier recommendations, which most people who stretch do.
Basic math governing triangles says that there will be less of a vertical component as the ange of stretch increases.


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## tmvw (Jan 14, 2008)

*Re: stretched tires...does it lower overall diameter of the wheel??? (JDriver1.8t)*


_Quote, originally posted by *JDriver1.8t* »_So the sidewall gets taller? There *has* to be an affect from stretching. Also, manufacturers don't account for stretching beyond thier recommendations, which most people who stretch do.
Basic math governing triangles says that there will be less of a vertical component as the ange of stretch increases.

fully aware of geometry...
no, the sidewall and overall rolling diameter does NOT change (very little to none) as proved by that link and info.
and manufactures have those specified widths to be on the safe side of the tire's ability to properly seat the bead with the wheel, not because the sidewall changes angles. and it also lists examples of OEM fitments that go +/- that 'range.'
that link i posted also says:
"Because tires have flexible sidewalls, a single tire size will fit on a variety of rim widths. A tire's rim width range identifies the narrowest to the widest rim widths that the tire is designed to fit."


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## turbott920 (Nov 13, 2007)

*Re: stretched tires...does it lower overall diameter of the wheel??? (tmvw)*


_Quote, originally posted by *tmvw* »_
and did you not see what i made bold?
"NOTE: because the overall diameter of a steel belted radial is determined by the steel belts, *there is little, if any*, change to the overall diameter of the tire *due to differences in rim width*."
the tire's overall diameter has little to no variance in measurement when mounting on different size widths because it is a predetermined measurement from the steel belts .....









_Modified by tmvw at 9:31 AM 5-27-2008_

lol this quote is from tire rack...of course if you stay within the allowed wheel widths the manufactuerer makes the tire for there will be little to no variance in diameter size but we are talking a stretch outside the normal scope of the tire. so if tire rack says there will possibly be little difference with a recommended wheel what do you think will happen when you go past that??? more change in diameter. DING DING!!!
this is perfect


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## tmvw (Jan 14, 2008)

*Re: stretched tires...does it lower overall diameter of the wheel??? (turbott920)*

i will re-iterate. the wheel widths recommended by the tire manufacturers are for the ability of the tire to seat the bead correctly at said width, not a whole lot to do with sidewall angles...
edit: i'm done, either way. no use in us arguing over this non sense stuff. i have provided more than enough math reasoning http://****************.com/smile/emthup.gif 


_Modified by tmvw at 12:47 PM 5-27-2008_


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## JDriver1.8t (May 20, 2005)

*Re: stretched tires...does it lower overall diameter of the wheel??? (tmvw)*


_Quote, originally posted by *tmvw* »_i will re-iterate. the wheel widths recommended by the tire manufacturers are for the ability of the tire to seat the bead correctly at said width, not a whole lot to do with sidewall angles...
edit: i'm done, either way. no use in us arguing over this non sense stuff. i have provided more than enough math reasoning http://****************.com/smile/emthup.gif 

_Modified by tmvw at 12:47 PM 5-27-2008_

All you have provided is a single link quoting a website, and basic calculation of outer diameter. You have provided ZERO math reasoning. Though the angle image did prove stretch makes a difference.


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## zeroluxxx (Sep 6, 2005)

*Re: stretched tires...does it lower overall diameter of the wheel??? (tmvw)*

note: i'm not a tire expert, so i'm not claiming it's one way or another for certain, because, i just plain dont know, i'm only stating my opinion. and i think it's fair to say no one else currently arguing this can defiantly answer this either. bottom line, were enthusiasts, not experts.
with that said, i understand where calvin is coming from, and to be honest, i dont think it relies as heavily on math as we think. i think it has to do more with the construction of a tire. we all know there are steel reinforcing belts that are sandwiched into the tire (along with more rubber and various other materials to provide strength). so, for the tires outside diameter to dramatically change, this would require the steel belts (and all of the other reinforcing elemets) to either expand, or contract a noticeable amount. something that i don't see happening. 
i understand that the belts are flexible to absorb road impacts, duh, but there is an obvious difference between flex and expansion/contraction. for example, its like comparing a gold bracelet to a rubber band. the bracelet will deform/flex, but the actual overall diameter (if constrained, say, around a wheel) will not change. where as, the rubber band will both flex, and expand/contract because of it's construction.
what i'm getting at is a tire is built for strength (steel belts), and while it will flex/deform, the actual outer tread area is not going to expand/contract because the steel belts aren't gonna stretch/shorten.
as mentioned earlier, the sidewall is used to make up the difference between different wheel widths. when a tire is on a proper sized wheel, the sidewall is normally bowed out, meaning, there is an obvious surplus of material. stretching the tire uses this surplus material to make up the additional distance to the bead on the wider wheel. dont you think the softer, pliable sidewall will conform and change shape and size before the reinforced, multi-ply, steel laden tread face will? i can't see how varying the sidewall angle would make a length of steel belt shrink (or numerous belts for that matter). if your diameter is getting smaller, you have to do something with the material that comprises that diameter, correct? if it can't shrink, as steel doesn't, how will it change? same thing if we were arguing tire expansion. the rigid steel in the belts would have to expand to allow this. this is why i say it has more to do with tire construction then math.
so, IMO, i have to agree that there is little to no change in the actual diameter once stretched. and as i mentioned before, unless we can get an actual tire engineer/expert to chime in on this little discussion, we're _all_ just speculating.


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## gehr (Jan 28, 2004)

*Re: stretched tires...does it lower overall diameter of the wheel??? (zeroluxxx)*

Winning an argument on the vortex is like winning a gold medal at the special Olympics, in either cases you're still a retard!


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## zeroluxxx (Sep 6, 2005)

*Re: stretched tires...does it lower overall diameter of the wheel??? (gehr)*


_Quote, originally posted by *gehr* »_Winning an argument on the vortex is like winning a gold medal at the special Olympics, in either cases you're still a retard!









name calling? that's mature (especially coming from a 40 year old).


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## gehr (Jan 28, 2004)

*Re: stretched tires...does it lower overall diameter of the wheel??? (zeroluxxx)*

It's was a general comment..........but what ever works for you!








When did I turn 40?!???!


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## zeroluxxx (Sep 6, 2005)

*FV-QR*

ah, well, to be fair, i did round up a bit.


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