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Old 03-26-2012, 09:34 PM   #1
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Goodyear Duratracs on Mamba MR-1s (Black)

I just installed this wheel / tire combo on my mechanically stock 2010 Unlimited. The tires (265/70-17 C - white lettering facing in) are nearly as quiet as the SR-As and I really like the look. These rims look similar to painted stockers, but push the tires out so that they are approximately flush with the outside edge of the fender. Center caps come only in chrome, but I painted them to match the wheels. There is no increase or decrease in diameter with this tire size. Pics attached.
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Old 03-26-2012, 09:40 PM   #2
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Looks good. Always liked those wheels...except their price tag. Just curious; what was your reasoning for not going up in tire size?

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Old 03-26-2012, 09:41 PM   #3
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Actuaully there is a difference in diameter. You went from 32.059" tires to 30.606".
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Old 03-26-2012, 09:52 PM   #4
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Actuaully there is a difference in diameter. You went from 32.059" tires to 30.606".
Tire rack says 31.7 for my Duratrac -- 657 RPM versus 660 for the stocker. Maybe their info is incorrect.
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Old 03-26-2012, 10:01 PM   #5
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Looks good. Always liked those wheels...except their price tag. Just curious; what was your reasoning for not going up in tire size?
Two reasons - one practical and one silly. I spend 98% of my miles are on the street and I wanted the look and extra snow and sand grip while minimizing the hit to street handling and mileage. Secondly, I wanted to keep using my Jeep anti-theft tire cover.
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Old 03-26-2012, 10:14 PM   #6
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Originally Posted by irideducs View Post
Tire rack says 31.7 for my Duratrac -- 657 RPM versus 660 for the stocker. Maybe their info is incorrect.
Yeah, the math works out to 32.059 vs 31.606, so Tirerack is pretty close.
265 * 70% = 185.5mm
185.5 * 0.0393700787 (inches per mm) = 7.303
7.303 * 2 (sidewall above rim, and below rim) = 14.606
14.606 + 17 (rim diameter) = 31.606
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Old 03-26-2012, 11:03 PM   #7
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love the look of that tread. looks great on your great looking jeep!
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Old 03-27-2012, 06:15 AM   #8
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Love those tires! But their diameter IS different from stock and your speedo will be off a tiny amount - 1 or 2mph maybe. I'm more concerned about the ECU tranny remaps for different diameter tires. I guess it shouldn't be too bad with such a small change but it will be off. These will be the ones I get if I do get duratracs. It's too bad they don't make them in stock wrangler sizes...

There is no rubbing with these I assume and no spacers required for the stock wheels?
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Old 03-27-2012, 06:29 AM   #9
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I like them. Looks good.
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Old 03-27-2012, 06:46 AM   #10
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Love those tires! But their diameter IS different from stock and your speedo will be off a tiny amount - 1 or 2mph maybe. I'm more concerned about the ECU tranny remaps for different diameter tires. I guess it shouldn't be too bad with such a small change but it will be off. These will be the ones I get if I do get duratracs. It's too bad they don't make them in stock wrangler sizes...

There is no rubbing with these I assume and no spacers required for the stock wheels?
The math says that there is a 1.4" difference in circumference for - coincidentally - a 1.4% difference in revolutions per mile (Duratracs calculate smaller). However, the tire specs show a much smaller difference as I mentioned above, and actually show the Duratracs to be just a tad larger. I picked this size because it was as close to stock as I could find per the specs.

I haven't had a chance to check the speedo yet, but the tires look very similar when standing side-by-side. I get the math, but don't understand the discrepancy with the specs. Is there anyone with more knowledge of tire industry practice that can explain? I have an Aeroforce Scangauge installed, so I can change the tire size in the computer as necessary.

The Mambas have less backspace than the stock rims, so no rubbing worries, and I have to imagine that you can get away with this size tire on the stock rims too - I believe they are only 1" wider. No direct experience with this, however.
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Old 03-27-2012, 07:10 AM   #11
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The tire industry is just like the shoe industry, just because it says it's the same size doesn't mean anything at all. If you look at on-road race tires they are always much wider than their advertised metric size (275s will measure out to 300mm or more)
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Old 03-27-2012, 07:25 AM   #12
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Looks good! Are they a matte finish? (little hard to tell from my phone) I want to paint my center caps too, wonder if I can do it with out removing them...
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Old 03-27-2012, 08:07 AM   #13
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Looks good! Are they a matte finish? (little hard to tell from my phone) I want to paint my center caps too, wonder if I can do it with out removing them...
I would have preferred matte, but they are more of a satin or semi-gloss. I took my center caps out for painting.
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Old 03-27-2012, 08:15 AM   #14
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I'll be interested to see if you notice a speedo difference. I've been contemplating going with the 265 DTs on my stock Moabs (mainly because I want the Goodyears), as I'm not interested in going larger and then dealing with rubbing or a lift or spacers.

There is a thread on another forum here that talks about these tires on stock wheels and have very little, if any real-world difference in size. I don't know if the Mambas are wider than the stock wheels, though.

I've "roughly" measured my stock, unused SR-A spare to not quite 32", but of course that's not 100% accurate.

Does anyone have an accurate way to get a real-world tire measurement? Does it matter if the tire sits with vehicle weight, or should we take unladen, properly inflated measurements on new tires? I just don't know what's right.

I expect, much like clothes or shoes, just because they spec out to a certain measurement, doesn't mean they end up that way.

Thanks.

Oh yeah... looks great.
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Old 03-27-2012, 08:17 AM   #15
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Quote:
Originally Posted by irideducs View Post
Tire rack says 31.7 for my Duratrac -- 657 RPM versus 660 for the stocker. Maybe their info is incorrect.

Duratracs 657 revs per mile=30.7 inch overall diameter.
Rubicon 17" stock rubber 650 revs per mile=31 inch overall diameter.
Sahara 18" stock rubber 653 revs per mile=30.9 inches overall diameter.

I find that the revs per mile figure is closer to the real rolling diameter.

2012 Wrangler spec sheet.

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Does anyone have an accurate way to get a real-world tire measurement?
I use a drop of liquid soap on the tire, back up the truck, measure between the two spots in my driveway, and divide by 3.14. My Dueler AT's are 31.09" based on 649 revs per mile, and measure 31.11", actual measurement using the soap.


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Old 03-27-2012, 08:20 AM   #16
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Quote:
Originally Posted by irideducs

I would have preferred matte, but they are more of a satin or semi-gloss. I took my center caps out for painting.
Did you scuff them up before you painted them? And what did you paint them with?
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Old 03-27-2012, 08:24 AM   #17
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Quote:
Originally Posted by irideducs View Post
The math says that there is a 1.4" difference in circumference for..
Actually, I get the math to work out to only .4" difference. See my earlier posts above. Am I doing the math wrong?

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Does anyone have an accurate way to get a real-world tire measurement? Does it matter if the tire sits with vehicle weight, or should we take unladen, properly inflated measurements on new tires? I just don't know what's right.
General consensus is to measure the tire mounted on the vehicle, inflated to the PSI that you want to run, and with the weight of the vehicle on it. Then measure to the shoulder to the ground, not the top of the tread to the ground. This is the process used when setting tire size via the ProCal or other tuner/programmer.
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Old 03-27-2012, 08:36 AM   #18
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Originally Posted by DrDanimalSize View Post
The tire industry is just like the shoe industry, just because it says it's the same size doesn't mean anything at all. If you look at on-road race tires they are always much wider than their advertised metric size (275s will measure out to 300mm or more)
I get that, but it is harder to understand how the detailed specs can quote a diameter and a RPM that do not correlate to each other. In this case, Goodyear's specs say that my new Duratrac is smaller in diameter that the stock SR-A, but does fewer RPM. Strange. I wonder if the more detailed specs are effected by tread depth. For instance, is diameter measured to the bottom of the tread? This might explain the oddity in comparing specs for these two tires.
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Old 03-27-2012, 08:37 AM   #19
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Actually, I get the math to work out to only .4" difference. See my earlier posts above. Am I doing the math wrong?

Your math is good.

You're doing diameter, he's talking circumference


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Old 03-27-2012, 08:41 AM   #20
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[QUOTE=4fit;2187128]Actually, I get the math to work out to only .4" difference. See my earlier posts above. Am I doing the math wrong? [QUOTE=4fit;2187128]

We are both right -- you are talking diameter and I am talking circumference.
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Old 03-27-2012, 08:41 AM   #21
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Actually, I get the math to work out to only .4" difference. See my earlier posts above. Am I doing the math wrong?
We are both right -- you are talking diameter and I am talking circumference.
Ah yeah. Overlooked that. d'oh!
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Old 03-27-2012, 10:00 AM   #22
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Did you scuff them up before you painted them? And what did you paint them with?
I scuffed them a little and used Duplicolor self-etching primer before painting with Duplicolor DE1635 - Black semi-gloss engine paint. All of the local shops where out of Krylon Fusion in Semi-gloss black and I already had a can of the other stuff on hand.

It's a perfect match - we will see if it lasts on the plastic.
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Old 03-27-2012, 11:59 AM   #23
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Originally Posted by irideducs

I scuffed them a little and used Duplicolor self-etching primer before painting with Duplicolor DE1635 - Black semi-gloss engine paint. All of the local shops where out of Krylon Fusion in Semi-gloss black and I already had a can of the other stuff on hand.

It's a perfect match - we will see if it lasts on the plastic.
Sweet. Thanks for the info.
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Old 03-27-2012, 09:52 PM   #24
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I get that, but it is harder to understand how the detailed specs can quote a diameter and a RPM that do not correlate to each other. In this case, Goodyear's specs say that my new Duratrac is smaller in diameter that the stock SR-A, but does fewer RPM. Strange. I wonder if the more detailed specs are effected by tread depth. For instance, is diameter measured to the bottom of the tread? This might explain the oddity in comparing specs for these two tires.
I received a precise answer to my question from the Chief Technology Officer of a major supplier of tire manufacturing test and measurement equipment. The tire diameter spec is calculated on an unloaded basis, so the math from the sidewall dimensions translates very closely to spec for diameter to the low point of the tread. RPM, on the other hand, is calculated under load and is influenced by the depth of the lugs. This is why the diameter of the stock SR-A is larger than the 265/70-17 Duratrac, but the Duratrac rolls very slightly larger at 657 RPM versus 660 RPM (bigger lugs on the Duratrac).

Bottom line -- this Duratrac and the stock tires are very, very close in specs under load and on the road (less than 0.5% different), so there is no need to worry about the speedo.
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Old 03-27-2012, 10:23 PM   #25
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With the 265's you lost 10mm or a little less then half an inch in height.
.......and that is what keeps me from buying them. Looks good though.
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Old 03-27-2012, 10:54 PM   #26
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With the 265's you lost 10mm or a little less then half an inch in height.
.......and that is what keeps me from buying them. Looks good though.
See my post above -- true by the pure math of a 265/70 versus a 255/75, but apparently not true on the car under load. Rolling diameter of the Duratrac is actually a smidge larger than the SR-A.
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Old 05-08-2012, 12:12 PM   #27
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I received a precise answer to my question from the Chief Technology Officer of a major supplier of tire manufacturing test and measurement equipment. The tire diameter spec is calculated on an unloaded basis, so the math from the sidewall dimensions translates very closely to spec for diameter to the low point of the tread. RPM, on the other hand, is calculated under load and is influenced by the depth of the lugs. This is why the diameter of the stock SR-A is larger than the 265/70-17 Duratrac, but the Duratrac rolls very slightly larger at 657 RPM versus 660 RPM (bigger lugs on the Duratrac).

Bottom line -- this Duratrac and the stock tires are very, very close in specs under load and on the road (less than 0.5% different), so there is no need to worry about the speedo.
If I understand this (and it's possible that I don't), you're saying that the 31.7" (DT) vs 32.1" (SRA) diameter measurement is based around the lowest point of the tread, right? So, if one ran both the DuraTrac and SRA to no tread, the diameters would be different.

However, because the depth of the DuraTrac tread is more than that of the SRA (18/32" vs. 12/32"), the actual rolling diameter of the DuraTrac is larger, thus creating the difference in the RPMs.

So, wouldn't we be more concerned with RPMs when buying tires and not diameter?

Further, wouldn't this measurement difference be a moot point, as the rolling diameter of a tire will then ultimately change as it wears out? Wouldn't this render the speedometer and odometer only as a reasonable estimate over the life of the vehicle?

If my assumptions are correct, this would put the bulk of the "smaller" DuraTrac's tread life within the acceptable tolerances built in to the calibration of the speedometer/odometer systems. Only when brand new and almost bald would the DT be out of spec.

Am I missing something?

Thanks.
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Old 05-08-2012, 01:25 PM   #28
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Thanks for the pics. I have the same wheels coming for mine with the duratracs 285/70/17. I ordered the wheels kinda blind, so the pics really put me at ease. Thanks again!
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Old 05-08-2012, 02:06 PM   #29
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So, wouldn't we be more concerned with RPMs when buying tires and not diameter?

Further, wouldn't this measurement difference be a moot point, as the rolling diameter of a tire will then ultimately change as it wears out? Wouldn't this render the speedometer and odometer only as a reasonable estimate over the life of the vehicle?

If my assumptions are correct, this would put the bulk of the "smaller" DuraTrac's tread life within the acceptable tolerances built in to the calibration of the speedometer/odometer systems. Only when brand new and almost bald would the DT be out of spec.

Am I missing something?

Thanks.
I think you understand it correctly -- clearly RPM is the only spec that directly correlates to speedo accuracy (if that is what you are primarily concerned with). When comparing two different tires, tread depth and sidewall profile (at a given wheel width and psi) affect the relationship between RPM and spec'd / unloaded diameter. The later is much easier to talk about, however, which is why everyone talks about their 33's or 35's.

If you do the math to figure out the tire diameter that equates to 657 RPM, the answer is actually about 30.7", or about an inch less than the specified diameter of my Duratrac. For comparison, the SR-As 660 RPM spec equates to about 30.5" or over 1.5" less than the spec. Again, it is the tread depth difference and loaded profile that accounts for the difference.

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