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Brompton rim wear and rim compatibility

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drossall:
I reckon that my 2012 Brompton must have single-wall rims. There are channel wear indicators, but they don't really help because they don't seem to wear down so that the channel disappears - instead, the channel just sits proud of the wearing rim. (I've seen that on my Mercian too with - obviously - another brand of rim.) So they look not unlike the ones in this Cyclechat post, except that mine are worn around the indicator channels.

So I'm trying to work out whether they need replacing. Brompton say around 0.5mm I believe, but I think that must be for double-wall rims. My Iwanson gauge says 1.0mm for the back. Haven't measured the front yet (will shortly), but you'd expect it to be less.

Second question - Brompton's documentation (PDF) says that different rims are needed for my rear 3-speed hub and my front SON dynohub. Anyone got any idea why? They are roughly the same size and shape. In fact, I've got some Ryde Andra rims put by that seem to be recommended for both, but I'm just trying to understand the background.

Pickled Onion:
For the second question, the rims for the hub gear hubs have angled spoke holes as they are built 2 cross and there's not much distance between the hub and the rim. The fronts wheels are specified 1 cross for dynamo hubs so don't need the angled spoke holes.

Your link for the Ryde Andra doesn't work, but if it's the one for angled spoke holes you'd probably want to build the front 2-cross (and frankly that's what I'd do, rather than using the standard Brompton front rim).

drossall:
Link now fixed. Made a typo and didn't check it afterwards - mea culpa.

Curiously, the Andra rims are recommended (by SJS) for both hubs, but specifically not for radial spoking. I wonder whether they have the same idea as you?

Gattopardo:
Ryan from SJS has moved on just to do bromptons now.  Might be worth while to speak to him about front hub upgrades.

drossall:
Thanks. SJS themselves weren't that helpful about advising on spoke lengths, given that it's them that sold the Andra rims. From my own calculations, looks like I need custom lengths!

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