Cute Q70 motor for Brompton... which rim?

[DBrown67]

I have a kit I bought from a UK supplier, which is great. But this weekend (after 4000 miles service) the front wheel broke at the brake rim.
I guess it got thin over time after all the service it's given. So this is not a complaint thread.

However, I need to get this fixed ASAP as I use it for my commute. The supplier is currently out of stock of all parts. So I'm looking to get this built up by a local shop.

I did read somewhere that a Sun CR18 16" rim is needed. But the supplier also said a standard Brompton rim would work. The current rim has 36 holes but a Brompton rim has fewer.
Then there is angled and straight holes. It all gets very confusing for a novice.
Having never built a wheel before, I have no idea of what matters most. Can I even use the old spokes? Because I wouldn't know where to go for new ones anyway.

The local bike shop were very accommodating at first, but after my 2nd call to them (to let them know that my ebike supplier was all out of parts) they cooled right down, and now say they only want to do the build if I supply the EXACT same parts as in the original wheel. Well I just can't do that. The rim on the original wheel will not be a Sun rim if that is what is needed.

So I'm needing the advice of esteemed e-bike builders on here who may have had experience of this motor for a Brompton. <^.^>

 

[matthewslack]

I remember quite a long Brompton discussion a while back. If you search brompton in titles only, it might be in that list. I don't have relevant knowledge myself.

 

[saneagle]

Sun 18 is what most people use, but there are some other rims available now if you search. Whatever rim you get, you'll have to measure the motor and rim, then use a spoke calculator to find the length of the spokes you need. You can buy the spokes from Ryan.

Custom Cut Spokes - Spokes From Ryan

Any spoke, any time, any size! We provide custom cut spokes from Sapim and DT Swiss. Free delivery and trade accounts available.

www.spokesfromryan.com

Edd, an easy to use spoke calculator

An easy to use spoke length calculator with a large amount of hubs and rims in its database.

leonard.io

 

[sjpt]

If the old rim is 36 holes the hub motor must be; you will need a new 36 hole rim.

 

[Woosh]

Brompton tyres are 37-349. You need a 36H-349 rim. I sold some spare rims in the last couple of years because nobody has them, now I am left with motors without rims.
I am reordering them now.

 

[DBrown67]

Brompton tyres are 37-349. You need a 36H-349 rim. I sold some spare rims in the last couple of years because nobody has them, now I am left with motors without rims.
I am reordering them now.

Thanks for that. Would this be suitable then?

Sun CR18 16 x 1 3/8 349 ABT Alloy Rim (sjscycles.co.uk)

I will be fitting a new Continental Urban Contact to this as I don't like the wire rim in the Marathon Plus.

Saneagle... as far as the spokes are concerned I'd be leaving that to the shop. But you've shown me they are readily available in any length/size.

Thank you all for your replies

 

[Woosh]

Yes, it should be OK. Spokes: you can reuse the old spokes. If you need a few more, ask Andy.

 

[StuartsProjects]

I bought a motor wheel for a Brompton from a large far East supplier.

The rim fitted to the wheel was most definetly not the rim type I have on all my other Brompton wheels and a Continental Contact Urban tyre would not stay on the rim, although others such as a Marathon plus were OK.

The supplier was just not interested in accepting they had fitted the wrong rim on their wheels but I guess that is one of the many benefits of buying stuff from the far East. If it had been a UK supplier then it would have been straight forward to get redress.

One thing I did find later was that the rim did accept the folding version of the Continental Contact Urban.

 

[Woosh]

That happens often. You have to get them to confirm that you want double wall, 18mm wide, 36 holes, 349. Otherwise, they don't know exactly what you need. 16in for them is 305 rims, 22mm wide.

 

[DBrown67]

I think I'm gonna have a go at this myself. How hard can it be? (LOL) I have the original wheel to make notes from. Number the spokes on each side and ensure they go in the new rim exactly as they are now. Write up a list in advance of what goes where, overlaps etc. Obviously it will need trueing up, but I'm sure a 16" wheel will take less adjustment than a full size wheel? There's more spoke length and therefore more chance to be out at the rim on a full size. At least that's my thinking.

Only issue I could have to stop me getting started is the spoke length. The hub is the same of course, but the there could be a discrepancy in the distance to each corresponding eyelet. None of the current spokes seem broken.

I've ordered the silver coloured version of the same rim I linked above. The holes are offset to the centre at each eyelet but not angled, which is the same as the current rim.

 

[saneagle]

I think I'm gonna have a go at this myself. How hard can it be? (LOL) I have the original wheel to make notes from. Number the spokes on each side and ensure they go in the new rim exactly as they are now. Write up a list in advance of what goes where, overlaps etc. Obviously it will need trueing up, but I'm sure a 16" wheel will take less adjustment than a full size wheel? There's more spoke length and therefore more chance to be out at the rim on a full size. At least that's my thinking.

Only issue I could have to stop me getting started is the spoke length. The hub is the same of course, but the there could be a discrepancy in the distance to each corresponding eyelet. None of the current spokes seem broken.

I've ordered the silver coloured version of the same rim I linked above. The holes are offset to the centre at each eyelet but not angled, which is the same as the current rim.

Look up Sheldon Brown's wheelbuilding guide. It's very easy to follow. You should go for a one-cross pattern with 14g spokes.

 

[Woosh]

His rim needs replacing, the spokes are stainless so easy to re-use. Just undo the nipples and remount as they are onto the new rims. May be worth buying new nipples but there is no need to buy a new set of spokes.
I would use sellotape to hold the old spokes as they are, saving a bit of time. Start with 18 spokes on the same side, screw on the new nipples to about 1mm from the end of the thread. That leaves all the spokes on the other side enough space to be placed inside their holes without you having to bend them. Work with a flat screwdriver as much as possible to avoid leaving marks on the nipples.

 

[DBrown67]

Sun rim arrived from SJS yesterday. Laced it up last night and balanced it (side to side only) this morning. All went OK. Only issue really was that the original spokes were a touch short for this rim. Could have done with 3-4 mm extra. Or longer reach nipples. But I did get all the threads on, before tightening it all up on the forks.

Done a few miles this morning and it's riding much better than it has done recently (lol but ofc it would).
Electric kit is still fine, was never any issue with that.

I did notice that there were some comments in reviews for that Sun rim, where people had experienced difficulty in fitting tyres. I fitted a new Continental Contact Urban and it was a breeze to fit in comparison to previous Marathon Plus. The Marathon + are excellent puncture protection, but the wire rim makes fitting more difficult. I suppose only time will tell if the Conti is as good.

 

[Woosh]

Congrats for a job well done. The old rim has double walls, so needed shorter spokes.