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Old 05-11-11, 05:48 PM   #1
peterarev
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Need to know rim sizing numbers

Hello everyone,

This is my first post. Glad to be here.

I have an electric Golden Motor (from China) on my front wheel that came pre-spoked on a high performance aluminum alloy "Deep V" type rim (not the brand name, just the type of rim) with the following sizing information: 26 X 1.5 X 36H. I cracked and dented the rim when I hit a curb and need to replace it with the proper same size so I can reuse the spokes. I need to know what the sizing numbers mean. The 26 is obvious, and the 36H would seem to be the height of the rim (in mm?) which would matter for the proper spoke fit. Am I on target so far?

I'm confused about the 1.5, though, because the rim is about 1-3/8" wide and I can't think of any metric measurement that would equal that width. Some measurement systems have a tire bead seat specification to be sure the tire will fit properly in the rim. Is this what the 1.5 refers to?

All this is to say that I don't need to replace the rim with exactly the high performance rim that I have now. As long as a standard 26" mountain bike or balloon tire fits securely on the rim, I'll be happy.
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Old 05-11-11, 08:47 PM   #2
mrrabbit 
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First off ditch that cheap ass crap Star Circle made rim from China - often labelled Vigour, etc...

Even if you hadn't had an accident, you eventually would have cracked the spokes holes...

Plus the spoke often provided with these wheels are cheapy-ass spokes with a "y" or a "heart-like" symbol on the heads - often in galvanized steel.

Get a 26 x 1.50 Chukker from Velocity - get new 2.3 or single-butted 2.3/2.0 spokes in stainless steel and have a competent wheel builder re-build your wheel for you.

=8-)

The wheels on most e-bikes from China were designed to fail...period.

=8-)
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Old 05-11-11, 10:48 PM   #3
Jeff Wills
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26 x 1.5 is the approximate tire size, 36 is probably the number of spokes. The bead seat diameter is 559 (millimeters), but what you need to know is the ERD: (from Sheldon Brown)
Effective Rim Diameter. This is the rim diameter measured at the nipple seats in the spoke holes, plus the thickness of the two nipple heads. The E.R.D. is needed for calculating the correct spoke length.

The only way to find this on your rim is to measure it. Then you'll have to shop for a rim with the same ERD.
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Old 05-12-11, 12:37 AM   #4
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While many wheelbuilders utilize diameter + thickness of the spokes heads, i.e., measure to the top of the nipple heads - remember the key word is "effective". I.e., if the number used works without any functional issues - then that's the particular wheelbuilder's ERD for a given rim.

My ERD's for example all aim for the screwdriver flat of the nipple. And I note that when providing ERDs so folks can decide if mine will work for them as well. Mavic does the same for standard profile nipples.

So it's really better to say: "Effective Rim Diameter. This is usually rim diameter..."

This way you are not implying there is one standard or one way for measuring ERD.

=8-)
__________________
4000+ wheels built since 1984...

Disclaimer:

1. I do not claim to be an expert in bicycle mechanics despite my experience.
2. I like anyone will comment in other areas.
3. I do not own the preexisting concepts of DISH and ERD.
4. I will provide information as I always have to others that I believe will help them protect themselves from unscrupulous mechanics.
5. My all time favorite book is:

Kahane, Howard. Logic and Contemporary Rhetoric: The Use of Reason in Everyday Life
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