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Mavic Rim Size Help!

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Mavic Rim Size Help!

Old 04-19-10, 12:59 PM
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jammmers
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Mavic Rim Size Help!

Hey All,

So I'm thinking about purchasing a pair of Mavic rims online but the seller is unsure the extra rim size.

I am looking for a 27" rim (not 700c). He measured the outside diameter and it came to 25". I know that a 27" rim doesn't refer to the diameter (from Sheldon Brown's website).

Can anyone shed any light on this for me?

Thanks

Last edited by lotek; 04-19-10 at 01:33 PM. Reason: fixed it for ya!
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Old 04-19-10, 01:17 PM
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Meant to say "Mavic" not "Mafac", my bad.
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Old 04-19-10, 01:22 PM
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27', or 630mm bead seat diameter rims would probably have (I'm guessing here) around a 636mm or so outside diameter, which would = right about 25".

A 700c rim, 622 BSD, would need walls/hooks that are ~7mm high to come to the same o-o diameter. At (my guess again) 628mm+, that's closer to 24 3/4".

The question now is, how accurate can the seller measure?

I think I have a 27" at home I can measure, but that will be later this evening.
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Old 04-19-10, 01:23 PM
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Thats a tough way to measure a rim if the seller doesn't really know what they're doing. a 27" rim is a Bead Seat Diameter of 630mm and a 700c is 622mm, so only a 8mm margin of error.

Simply measuring the outside diameter isn't gonna give you an accurate picture of the size because different rims have different sidewall constructions and will vary in diameter. The accurate measurement that you want to get is the ETRTO/ Bead Seat Diameter.

Here's a link to instructions to measure a rim...if your seller can follow directions well enough this might help https://sheldonbrown.com/rim-sizing.html
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Old 04-19-10, 01:41 PM
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I can think of two solutions:

1. Ask the seller to put a tire on the rim and see how it fits. Don't trust him to do any more measurements.

2. If this doesn't work out, or if he's unwilling/unable, find another seller. You need someone more knowledgeable, so you don't buy the wrong thing.
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Old 04-19-10, 01:53 PM
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Originally Posted by Ex Pres View Post
27', or 630mm bead seat diameter rims would probably have (I'm guessing here) around a 636mm or so outside diameter, which would = right about 25".

A 700c rim, 622 BSD, would need walls/hooks that are ~7mm high to come to the same o-o diameter. At (my guess again) 628mm+, that's closer to 24 3/4".

The question now is, how accurate can the seller measure?

I think I have a 27" at home I can measure, but that will be later this evening.
I completely agree Ex Pres. I have a 700c rim in front of me right now and its outer diameter (not BSD) measures 630mm or 24.75". However, I know its BSD is 622mm, so about 4mm per end for the brake wall.

If you could measure your 27" rim, that would be very helpful! Thanks!
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Old 04-19-10, 02:01 PM
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Good point noglider. Just sent him a message, we'll see what happens. Most likely going to have to find another seller.
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Old 04-19-10, 09:41 PM
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It's the dreaded sample size of 1, but my 27" measures just over 25" outside to outside. Still not sure that's enough to take a flyer on these, unless they're cheap enough to recoup your cost.
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Old 04-19-10, 09:45 PM
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Did Mavic ever make 27" rims?
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