Tire manufactures are lying about sizes! - TCCoA Forums
 
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post #1 of 29 (permalink) Old 07-06-2007, 04:48 PM Thread Starter
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Tire manufactures are lying about sizes!

Be wary of sizes touted by manufacturers! I have dealing with new tire problems
( http://forums.tccoa.com/showthread.php?t=101621 ). I used to have Goodyear Eagle HP 235-55-16. So I went to buy replacements (Goodyear eagle GT-HR 235-60-16). These were 1.5 inches narrower than the old eagle HPs. I took the Goodyears back to discount tire for several reasons (they sucked) and exchanged the for Kumho Ecsta ASX in the 235-60-16. These Kumhos are .25 inches narrower than the 4 year old 225-60-16s on my girlfriends car! I think over the last year or so, tire manufactures started lying about the true tire size to save material.
It is odd that both Goodyear and Kumho market a 235-60-16 and say the tread is 9.0 inches wide, but according to my tape measure they are really 7.8 inches wide and on a four year old 225-60-16 the tread is 8.2 inches wide. Has anyone else noticed this?

Last edited by W.Cup; 07-06-2007 at 04:56 PM.
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post #2 of 29 (permalink) Old 07-06-2007, 05:03 PM
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Wow! No, I haven't noticed. Thanks for bringing this to my attention. I'll be sure to look closely at my next set of tires.
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post #3 of 29 (permalink) Old 07-06-2007, 07:54 PM
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Section width, not tread width is how they are sized.

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post #4 of 29 (permalink) Old 07-06-2007, 08:07 PM Thread Starter
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Quote:
Originally Posted by Bangster View Post
Section width, not tread width is how they are sized.

Yes I know that. All I know is tires have gotten smaller for some reason. How many people would actually go and measure their tires to make sure they are getting what they are supposed too, probably very few. Most people would never notice if 5 or so mm was missing.
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post #5 of 29 (permalink) Old 07-06-2007, 08:31 PM
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most will have the rim size the section width is for, and tread width

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post #6 of 29 (permalink) Old 07-10-2007, 10:59 PM
 
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tire sizes

I posted (somewhere ) about the same issues, but mostly about the overall advertised height of tires. The tire specs (235/60/16) are supposed to represent set numbers, but dont! That tire is supposed to stand 27.10 in tall (diameter) and have a circumference of 85.14". Bet if you measure the actual roll, it will be less by a good percentage --I have!

My 32/11.50/15 Bronco tires only measure (reverse math) as 31" tall. Dont recall exactly, but the 235/60/16 BFG's on the wifes GranMarq are actually shorter as well.

I have come to the conclusion that a tire Mfg uses the figures to target a tire size they wish to market, for certain applications, and has nothing to do with actual measurements.

True, the width figure is for the widest part of the tire, not necessarily the tread. I expect thats way off as well. One part of a tire that will not expand or contract (to any measureable degree) is the length of the tread belt (circumference/revolutions per mile). You turn that sucker one revolution, and it will go the tread length forward or slide.
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post #7 of 29 (permalink) Old 07-11-2007, 05:14 AM
 
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Originally Posted by yardbird View Post
The tire specs (235/60/16) are supposed to represent set numbers, but dont! That tire is supposed to stand 27.10 in tall (diameter) and have a circumference of 85.14". Bet if you measure the actual roll, it will be less by a good percentage --I have!

One part of a tire that will not expand or contract (to any measureable degree) is the length of the tread belt (circumference/revolutions per mile). You turn that sucker one revolution, and it will go the tread length forward or slide.
I have a brand new unmounted Falken Zies ZE512 sitting here. The best I could tell with my tape measure is that it's 85" around it's circumference (take or give an 8th of an inch). It doesn't seem like it's a "good percentage" off from the 85.14" circumference it should be... how much did you wanna bet it's a "good percentage" off? What is a good percentage anyway? .25%, .5%, 1% 2%?
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post #8 of 29 (permalink) Old 07-11-2007, 06:54 AM
 
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tyres

I will try to clarify a little for you Southpaw Fast Ed made an observation you might want to make note of that different Mfg's can be different in each size, I agree. If Falkens are "true to size" then that is worth making note--. A tape measure may get you close, but put that sucker on a rim, of suggested size, air it up to suggested pressure, then roll it one full revolution on the ground and measure. That is the circumference your instruments will see. I made no statement that some tires could not be on spec.

There are numerous witnesses posts that say some tires dont measure up, including mine. For one, BFG traction TA 235/60/16's do not. Bridgestone APT 32/11.50/15 and also 31/10.50/15 tire do not measure up. The BS (naw, Bridgestone) tires are off by ~ 1" which is abt 10%---thats a good persentage. My opinion is that 5 % might be considered a "good percentage" also. Depending which way it is off, those "good percentages" could get you a ticket if you dont correct!

The OEM 225/60/16 on the Sup Cpes measures as (by my math) 8.86" sect width, 26.63" diameter (tall), and 83.66" circumference (per each revolution). The better looking tire, the 235/60/16 is 9.75"/27.10"/85.14" for the specs. Thats (my math again) ~ 10 % difference. Thats also a good percentage. The seemingly popular size of 245/50/16 measures 9.25"/25.65/80.57". That is way shorter than the oem, 10% the wrong way, or 235's. Since no one asks for my money to buy them, and I respect the opinions of others, I am perfectly happy for anyone who buys a tire of their choice.

Point is, be informed when you buy tires. Be sure you are buying what the specs state, and what you need for your car.
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post #9 of 29 (permalink) Old 07-11-2007, 07:34 AM
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that's not unusual, goodyear's agricultural tires traditionally run smaller than anybody elses
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post #10 of 29 (permalink) Old 07-19-2007, 02:00 PM
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The un-mounted diameter, tire width, and overall circumfrance of a tire is going to differ from the mounted diameter, tire width, and overall circumfrance.

Your going by the manufacturers specs on their un mounted tires and trying to compare that to a tire thats been mounted on a spectrum of different wheels, thats just silly.
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post #11 of 29 (permalink) Old 07-19-2007, 03:01 PM
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the section width is with it mounted on a specified rim width, the widest point of the tire, which isn't the tread. Measuring a tire unmounted, that's just silly (just continuing the theme).

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post #12 of 29 (permalink) Old 07-19-2007, 03:07 PM
 
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Originally Posted by yardbird View Post
I made no statement that some tires could not be on spec.
Nor did i make a statement that all tires are IN spec based on my observations of the 2 matching tires i have on hand.

Since you stated "Bet if you measure the actual roll, it will be less by a good percentage --I have!" I did ask how much you wanted to bet, since i have 2 umounted tires sitting here that will shortly be mounted on rims. I also asked what you consider to be a "good percentage" off. How many percent is that since you seem to want to bet on it?
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post #13 of 29 (permalink) Old 07-19-2007, 09:32 PM
 
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%'s

What are you doing southpaw, trying to pick the flys**T out of the pepper?

Whatever the measurement of your tires turns out to be compared to the actual specifications by the Mfg. I nor anyone else has been inaccurate. I accounted that some will, some wont. My BFG's and Bridgestone's dont, your Falken's apparently do. I believe I said that was worthy of note that Falkens are apparently true to the specs. The fact still remains, BFG & Bridgestone (at least some of them) are not, so I have said nothing that is not true----at least about tires Did you notice what I said at the very last of my post? In short and dumbed down, "Be an imformed consumer".

5% is a good percentage to me. Depending on what your reference is, maybe more, maybe less. Its an individual thing and it can be whatever you wish-----frankly Scarlet I dont give a damn!!

The only thing I would "bet" on is that tires differ--but then several others said the same thing. You seem to be hung up on the "betting" thing. I intended it only as a figure of speach, used many times, by many people. Actually, the discussion here was about tires that did not measure out to the specs indicated. Since yours may have, why the hell are you in this discussion?

PearlbirdSC-- I have to disagree with you on the circumference changing when mounted. Now dont take offense as some would, I mean no disrespect to you. I simply disagree. The tread, because of the woven design will not streach or shrink to any appreciable degree. It will fold etc, but I Bet (catch that one southpaw?) it will not change length. In my opinion
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post #14 of 29 (permalink) Old 07-19-2007, 09:56 PM
 
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Originally Posted by yardbird View Post
What are you doing southpaw, trying to pick the flys**T out of the pepper?[/B]
I don't know what your going off about but it's plain silly. I didn't say anything other then that the tires i have sitting here seem to measure up without being mounted, and that i'll measure them again when mounted.

Your the who seems confident enough most tires are mis-sized that your challenging people to measure their tires and you'll bet on it that they don't measure up to the specs. I'm not interested in arguing with you. btw i could really care less if they are off by a few mm. I'm not that anal retentive to make a big stink about it like some of you are. Other aspects of a tires performance are much more important to me then it being exactly the size specified.

I NEVER SAID ANYONE'S MEASURMENTS WERE INACCURATE. I don't know where the heck you get that from!? Your the one talking sh*t like "Bet if you measure the actual roll, it will be less by a good percentage --I have!" That comment was about 235/60/16's in general, not any particular brand you've measured.

I say ok let me try that and you start harping on me like i said your full of sh*t. I didn't say anything about your measurements or conclusions. I simply took you up on YOUR bet that if I measure my tires they'll likely be off from the specs. The only reason i even bothered is the tires are sitting right here in my bedroom and my Stanley tape measure is clipped to my desk. Your allegations along with those of the original poster intrigued me so i measured the damned things like you challenged people to do. excuuuuse me!

Quote:
The only thing I would "bet" on is that tires differ--but then several others said the same thing. You seem to be hung up on the "betting" thing. I intended it only as a figure of speach, used many times, by many people. Actually, the discussion here was about tires that did not measure out to the specs indicated. Since yours may have, why the hell are you in this discussion?
Actually no, that's not what you said you would bet on. You said you'll bet that if we measure our 235/60/16 tires they'll be out of spec too. you seemed rather confident about that, confident enough that you would wager on it.

You've found tires you've measured to be out of spec. You've encouraged others to measure their tires too, but when i do and they seem to match the published specs i should just shut up and go away? I suddenly have no business posting in this thread anymore? wtf? If mis-spec'd tires are a legitimate issue is it not helpful to know what brands ARE in spec too??? I would think that would be as useful to know as well.

I don't see how the fact that my falkens seem promising somehow discredits your observations about altogether different brands of tire either? That seems to be your conclusion and that's not what i said... I never called BS on anyone elses measurements and observations. I just took up your challenge because i was curious about my tires. Having bothered to measure them why wouldn't i comment on what i observed?

Anyway i'm waiting on a rim i ordered to arrive and when it does, and the tires mounted up and inflated, i'll take some measurements and report the results. Not because i want to call BS on anyone but because i'm interested in what the measure. Before i put it on the car i'll be able to roll it as well as lay on its side and lay a straight edge across the face of it so i can accurately measure the section width too.

Last edited by Southpaw; 07-19-2007 at 11:32 PM.
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post #15 of 29 (permalink) Old 07-26-2007, 01:22 PM
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[QUOTE=W.Cup;1001436]Yes I know that. All I know is tires have gotten smaller for some reason.

cheaper rubber. Not to mention the way the tires are cast.
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post #16 of 29 (permalink) Old 07-26-2007, 01:43 PM
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Quote:
Originally Posted by yardbird View Post
PearlbirdSC-- I have to disagree with you on the circumference changing when mounted. Now dont take offense as some would, I mean no disrespect to you. I simply disagree. The tread, because of the woven design will not streach or shrink to any appreciable degree. It will fold etc, but I Bet (catch that one southpaw?) it will not change length. In my opinion
Circumference will change based on pressure.

One thing I have often wondered about: Does a tire with a load on it have the same revolutions per mile as a tire with no load?

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post #17 of 29 (permalink) Old 07-26-2007, 09:52 PM
 
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tire pressure

Still disagree
Increase or decrease of tire pressure does not streach or shrink the length of the tread. Very small amounts maybe, but not much. When pressure is decreased, the amount of tread on the ground lengthens but the circumference doest change (much).

Yes to the load question, same revs per mile. (again, my opinion). In order for the revs per mile to change, the circumference must change. For that to occur, the tread must streach or shrink (lengthwise). Anyway, this is what a respectable disagreement should look like--- This is almost as much fun as arguing with my brother about the water hose in the hot sun and the pressure generated!

Southpaw--
Still picking flys*** I see. So far, you have not challenged any issues I raised replying to the subject of this thread. Some tires are not entirely accurate, even others agree. Your Falkens seem to be-----great! Your contribution was to challenge me about "bet" "percentage", both arbitrary figures of speech. BTW, do you know what the meaning of "is" is? Send your answer to a past president---.
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post #18 of 29 (permalink) Old 07-26-2007, 10:17 PM
 
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Your a funny guy... You measure a couple of specific brands of tires and conclude they're out of spec size wise. Based on those results you extrapolate that it's common for tires to be out of spec. Your confident enough about that to challenge others to measure their rubber too and to use your figure of speech "you'll bet on it" that they will be out of spec too (i.e. your confident about it - i know it's a figure of speech and what it means thank you). Well i measured my Falkens (as you suggested) and they don't seem to be out of spec.

I say as much and you tell me that in-spec tires have nothing to do with the topic and i should just keep it to myself... not to mention you assumed i'm challenging the credibility of your and the OP's tire measurements, which i didn't. I haven't said anything about any brand/model of tires except my own. I'm not sure why you would think that???

Just get over it.

Last edited by Southpaw; 07-26-2007 at 10:47 PM.
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post #19 of 29 (permalink) Old 07-27-2007, 06:29 AM
 
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yep

I notice you didnt reference any of the other posters who seem to have noticed what I have about tire measurements. At least one of them seems to be very knowledgeable about lots of things, including tires. Dont understand your position on the subject---so far you have not proven anything I (we) have said thats wrong. The whole scientific basis for your conclusions seems to be based on one brand of tire "Falken", which is not contradictrary to what we are saying. BTW, your havnt mentioned any measurements on the tires presently on the rims---!

I am confident enough about my observations to suggest others who have questions to measure also. I doubt the others want to read this meaningless trash, so I am going to leave it with you, sport. Maybe you can get a few more to add to that post count. Meanwhile the facts still remain---!
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post #20 of 29 (permalink) Old 07-27-2007, 07:17 AM
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Quote:
Originally Posted by yardbird View Post
Still disagree
Increase or decrease of tire pressure does not stretch or shrink the length of the tread. Very small amounts maybe, but not much.
Not to argue (just presenting my opinions), but I think we will agree that if you put 20 lbs in a tire vs. 40 lbs in a tire the middle section of the tread will have a larger overall diameter. If it didn't it wouldn't wear out the center of the tire when you have too much pressure.

For discussion's sake, let’s say it is 1/4" larger diameter, and the diameter (as measured down the center of the tread) with 20 lbs of air is 30 inches. So you have 30” vs. 30.25” diameters. Circumference differences would be 94.25” vs. 95.03; or 762.25 revolutions per mile vs. 666.74 revolutions per mile. That is a 12.5% difference. And that is only with a 1/4" overall diameter difference.

Small diameter changes have huge changed on circumference.

Something else to think about: Where exactly is the manufacture measuring when they say “tread width”? Is it the tread that would touch the ground, or is it from where the tread pattern starts on the tire (i.e. usually a little ways down the sidewall)?

I’m just saying that I don’t think they are lying, but what is more likely is that what we are measuring as compared to what the manufacture is measuring are two different things.

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post #21 of 29 (permalink) Old 07-27-2007, 09:21 AM
 
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pressure

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I understand your point. Why dont you actually measure roll-out of one revolution at different pressures? I havnt done that, so I could stand corrected. My measurements for all tires are ~ 35psi. I would expect some difference, but not very much.

The first # is supposed to be the widest part of the tire, usually the "belly" of the tire, measured in mm. The second is the aspect ratio in % of the width to the side wall height. Last is the rim size. My main concern is to the circumference of the tire, thats what fills wheelwells and speedometers---Oh yea! width is important too.

Hope this didnt double post, Not sure what this thing just did!
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post #22 of 29 (permalink) Old 07-27-2007, 09:54 AM
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Are you going by the numbers listed on the tire, or the numbers listed by the manufacturer in their specifications (like you can get on tirerack)?

For example:

Bridgestone Dueler D683 HL: 31 x 10.5 x 15
Section width (measured on 7.5” rim): 10.9”
Tread width: 8.1”
Overall diameter: 30.5”
Revolutions per mile: 683

Firestone Destination M/T: 31 x 10.5 x 15
Section width (measured on 8.5” rim): 10.5”
Tread width: 8.3”
Overall diameter: 31”
Revolutions per mile: 672

Those are the "official numbers" to my knowledge.

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post #23 of 29 (permalink) Old 07-27-2007, 11:50 AM
 
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truck sizes

I have 32X11:50X15 bridgestone dualer APT presently (~40K miles). Previously I had the same tire in 31X10:50X15 for ~55K. I dont recall the actual #'s on the 31's. Never actually measured total width, except for the tread which was not widest part. I do recall that they were appx 1 in. short on diameter. (using reverse math by circumference) The 32's are also a full 1" short. Havnt measured width or tread, but can do that soon--. Speedo clocks (best estimate) 2-3% slower. Rims are ford truck 7.5" rims. Those #'s seem to be actual not like auto tires. With 40K any measurements will be less now. Except for diameter, I have not run the numbers to compare against mfg's other figures.

I did recalibrate the PSOM on the speedo module, for the 32's, and the revs per mi. were different from the mfg (good percentage) I dont recall the figures, but I can pull up the calculation from the PSOM to see what I actually measured.

I would be interested to see the difference with pressures. I suspect (I would bet figuratively) that some variation exists. Why dont you measure and post! I am too lazy lately to do it.
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post #24 of 29 (permalink) Old 07-27-2007, 12:56 PM
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I think everyone calls the difference in Tire size and specs is tolerance. Althought what I have been readinghere, it seems like unacceptable tolerance. Tires sitting on top of each other in a stack would cause the bottomtire from the stack to be deformed, and would take some time to return to its size, Even inflated, it may not return without some time for it to return to its correct shape.

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post #25 of 29 (permalink) Old 08-13-2007, 09:45 PM
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This is from the Hoosier racing website

In our printed product catalog and on our website tire specifications you will see two columns of information regarding rim dimensions. In most cases, the "measured rim" and the "recommended rim" will be the same. However in the case of DOT tires, the information may appear contradictory.

The reason for the differences lies in the Department of Transportation requirements for publishing tire dimensions on any tire that carries a DOT certification. Each tire size has a specific rim that must be used when taking measurements for tire comparison. This is intended to allow consumers a consistent way to compare tire sizes between brands.


I have a pair of Goodyears and a pair of Kuhmos on the car, same size, but the tread width is smaller on the Kuhmos for sure. Funny thing, the Kuhmos have traction the Goodyears only dream of.

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post #26 of 29 (permalink) Old 08-18-2007, 12:53 PM
 
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Tire measurements

94 Daily Driven----

Finally got off my tail and did a few "scientific" measurements---(driveway, cheap ruler, cheap tire guage ). I havnt run all the #'s for speed difference, ---first thing "next" Monday!

93 EB Bronco/351/E4OD. 32X1150X15 Bridgestone Dueler APT on 7.5 std ford rims.
"C" rated, 2535#@50 psi
tread 9 1/2 "
(didnt measure widest belly of the tire, appears to add 2" total)
Appx mileage 30K . Did not measure tread depth. 17/32 new (i think!)

4960# total wt. ~ 1/4 tank gas, no driver, no load.
2580# Front axle 52%
2380# Rear axle 48%

Weights on truck scales, Orlando, fl 4/4/95 (gross/tare receipt)

50 psi 95.5" measured roll 30.40 dia.
40 psi 95.375" " 30.36 "
30 psi 95.125" " 30.28 "
20 psi 94.875" " 30.20 "
10 psi 94.375" " 30.04 "

All partial inches were converted from 1/8 " figures

My figures are certainly not scientific, but do represent pressure affect on tire circumference. Whether or not these figures are significant or of importance is strictly a personal thing. Noticeable belly and "rolling of tread edges at ~15 psi. Anyone running any speed at lower than 20 psi may be in deep stuff quickly!

Also, "radius" cannot be applied for this measurement (as in "loaded radius") be cause "radius" only applies to a perfect circle. Anything with one flat side cannot be a circle!!

Anyway, just FYI and not a "flame" to anyone
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post #27 of 29 (permalink) Old 08-23-2007, 04:56 PM
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Quote:
Originally Posted by yardbird View Post
I understand your point. Why dont you actually measure roll-out of one revolution at different pressures? I havnt done that, so I could stand corrected. My measurements for all tires are ~ 35psi. I would expect some difference, but not very much.
Pressure will change the circumference. At lower pressure, the weight of the car will deform the tire more, making it less round and while driving will effectively lower the circumference.

Tread width is not going to change based on mounting or pressure since 98% of tires have very clear tread blocks. Section width can change by half an inch or more based on mounting.




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You drive "like a man possessed"... by a woman!
GreenBird is offline  
post #28 of 29 (permalink) Old 08-23-2007, 08:27 PM
 
Join Date: Oct 2002
Posts: 221
tyres

My figures that I measured on my 32X1150X15 bridgestones, only change the circumference by ~.988 % from 50 psi to 10 psi. The % figure will pretty well hold true for most figures (MPH , Revs per mile etc.) The MPH figure, for 100 mph, for example, will mean that actual 100 is 98.8 at 10 psi----at least thats my math (feel free to correct if not accurate). I speculated that in an earlier post on this thread. Whether or not it is significant is another personal thing.

Now what I would like to see is someone measure the circumference of an unmounted tire, then measure when mounted on spec rim at spec pressure!
yardbird is offline  
post #29 of 29 (permalink) Old 09-26-2007, 12:29 PM
 
Join Date: Oct 2002
Posts: 221
tire sizes--mfgs measurements

I just had to put new tires on the house Frau's merc 03 marq. A 2X4 kicked up by a truck caught the LF right on the sidewall and put a nice hole in it. Instant flat and bead pulled into rim--thank goodness she was not going very fast! It was about ready for tires anyway.

Took off 235X60X16 Bridgestone TA's, Put back Michelin "Weatherwise II's" 225X60X16's. Just measured 1 full roll at ~32 psi. I dont know where the Mfg gets the published specs from, but it "aint" from the math that I know to show the various specs (circumference, diameter, width etc.) I wont go into the math, most everyone knows how the figures are supposed to work. It may not be important to some, but it is to me----you know, the informed consumer thing! I would really like to know what their explanation is, but it is obvious that their "diameter" and "revolutions per mile" do not match-----using my math anyway.

My measurements for 1 full roll were-- 80.875 inches. (1/8 inches converted to decimal). That measurement, using conventional math, equates to a 205X60X16!!
The diameter should be 26.63", but is actually only ~25.69". Thats 1 full inch shorter than what most would think they should be. The Michelin website shows 789 revs per mile for this tire. That is in line with what the conventional math shows for the 205X60X16 tire. Michelin specs show the correct diameter for the tire using the figures I use. My math for the 225 tires show 757 revs per mile, which is about 5% off. To me that is a "significant" percentage----.

My point is that many have already noticed that posted mfg tire sizes are not accurate for most of us. If you need 26.63 inches (or 27 ) of tire to fill a wheel well, then do not buy a 225X60X16! It is a consumer awareness and personal preference thing
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