20" rear wheel build question

[guerney]

I'm a little miffed at the dearth of rims available in the UK for my bike and 1.75" tyres. I would love to be able to use 406 36H rims, they're much easier to find. Suitable 28H wheels and rims are increasingly hard to source. If it was possible for me to build my own wheels with 32H or 36H rims, it'd future-proof my bike. There seem to be many 406 20" BMX rims out there.

My question is, can I combine this Shimano 130mm hub:

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Or this:

Shimano Sora FH-RS300 Sora Freehub 130mm Q/R, 8/9/10-speed, 36 hole, black £19.99

Buy Shimano Sora FH-RS300 Sora Freehub 130mm Q/R, 8/9/10-speed, 36 hole, black today for £19.99 at Singletrack Bikes

www.singletrackbikes.co.uk

...and a 32H or 36H rim, for use on my Dahon Helios P8?

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If so:

1. How would I work out what spoke size to use?

2. Would I need to replace my Sram 8 speed rear cassette with a Shimano? If so, would a Shimano rear cassette be compatible with my Sram X8 mech?

 

[Nealh]

No reason those hubs can't be used.
Spokes , one has to use a spoke calc. The spoke calc does all the work once the info is input, one needs to know rim erd and the hub spoke hole flange dia etc etc.

Sram and shimano 8 spd cassettes use the same spline specs so one fits the other, x8 mech will work with any 8 spd cassette used. The only time one can't mix components is the gear changers and derailleurs, Sram actuation ratio is 1:1 and shimano is 2:1. .

 

[guerney]

Thank you @Nealh - that's very useful information. There are a few double walled 20" 32H and 36H rims on AliExpress of dubious looking quality. Dahon do make some very nicely engineered thick and stable rims, unfortunately they're too narrow for 1.75" tyres.

The only time one can't mix components is the gear changers and derailleurs, Sram actuation ratio is 1:1 and shimano is 2:1. .

Aha! That explains why this isn't compatible:

Shimano Claris Rear Derailleur Mech SS

2400 Claris derailleurs feature an advanced light action for low-friction shifting up or down the block

foldingbike.biz

Luckily despite the years, my X8 is still ok, but if it needed replacing and I had to use the above, it's good to know I'd also require a compatible Shimano shifter.

 

[Nealh]

There are some sram shifters that use 2:1 actuation for compatibilty with shimano shifting bur generally most stick with one brand or the other.

 

[guerney]

That's very useful information - I'd only replace the X8 with a Shimano, if I couldn't source another X8. I have zero brand loyalty, and don't mind progressively creating a Frankenstein's monster bike, if it works.