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I want to keep my old Alex A-Class rear hub which is 24 hole. The only problem is I can't find any spec for the hub. If I attempt to measure the centre-flange left and right and the flange radius with a tape will it be asking for trouble?
The only other thing I can think of is finding another rim with the exact same measurements. Rim depth, is it measured over the total external profile? And ERD is that the inner diameter?
Old Alex A430 (not same as new version) thought about fitting Halo AeroRage rims as they look very close.
EDIT; i.e a low profile rim would have a greater ERD?
it doesnt have to be exactly right. as long as the spokes dont stick into the rim, and have enough thread to hold onto in the nipples, should be fine....?
It's quite easy to measure a hub. How? It's all in the Wheelpro book. 🙂
just measure the hub. you have to get it quite wrong to end up with the wrong spokes (but don't quote me!)
if you're not confident just get an experienced wheel builder (LBS?) to measure it too - to overcheck your dims.
Bit of a start here:
[url= http://www.wheelpro.co.uk/spokecalc/ ]Wheelpro measuring how to page[/url]
Give or take a mm or so on the hub dims wont make very much difference. IIRC it takes something like 10mm difference on flange diam to make a spoke size difference. My old bikeshop boss used to glance at the hub and guess the lengths, he was right 90% of the time. The remaining 10% of the time I gave him the wheel to de-lace and re-lace 🙂
Cheers for the pointers.
Getting a rim as close in spec to the old one seems the best idea.
It's a lot easier thanvernier calipers and spreadsheets:
1. Measure the spokes you have just now (1 each side).
2. Buy new rims
3. Meeasure the difference in the ERD (line them up and see whether the ferrules in the new rime are further in/out to the old)
4. Add/subtract from the original spoke length from 3 above.
5. Build new wheel with confidence.
Just to be clear. Do you currently have a complete wheel? If so, as you say, just try and get a rim with the same nipple bed diameter.
Failing that, measure the existing spokes and for each 2mm difference in the dia of the rim, knock a mm off (well really a bit less but unless you're talking about a really big difference in the dia, it'll be fine)
Yes got the complete wheel. Just struggling to find that many 24 hole rims. As I say I'm hoping the Halo Aero rage will be a direct fit.