Which kit? 12 mile range, 20mph, hub motor, city bike

[emjay]

Thanks for a great answer. One more thing: is there an accepted best practice for installing torque arms? I have ordered a pair because my frame is alu.

 

[Deleted member 4366]

They're pretty simple. Stick it on the axle on the disc side, chuck the original tie-bar and make your own to tie it to the disc caliper fixing or any other solid point. You can modify the original tie-bar, but you need a 5% cobalt drill to drill it and an angle grinder to cut it.

 

[emjay]

OK, managed to get a couple of hours to work on the project today but have run into a few snags, looking for some (more!) advice.

I got the cassette and disc onto the new rear wheel without any trouble. Then I found that the hub motor housing was hitting the caliper, so had to add a bunch of washers to space it out. Because of that, I then had to add a bunch of washers between the hub and the dropout. And because of that, I had to add a bunch of washers between the disc and the disc mount to move it back in line with the caliper.

So currently everything is aligned fine and the wheel is sitting happily in the dropouts. I'm not too happy about my rear disc hanging out off a stack of washers, but am ordering some proper disc mount spacers to fix that.

The main problem I have now is that the torque washers supplied with the motor are currently doing absolutely nothing - here's a high resolution pic of the disc side:

The dropouts are relatively shallow, and there's probably enough material that I could start filing them to allow the torque washer to engage. But I'd be a bit worried about removing so much material from a pretty important area of the frame.

I also have torque arms and have cobbled together a bar to attach it to the caliper mount on the disc side:

Now I have the measurements I think I can probably build a more convincing version out of thicker metal, which may avoid the need for the torque nuts altogether.

Any advice?

 

[Deleted member 4366]

You should file your drop-outs deeper and reshape them to the shape of the axle.Put the anti-rotation washer in a strong vice and bash the tab right over until it's approx at right angles.

Your torque arm doesn't look right. Ideally, you want the tie-bar at a right-angle to the arm itself. There's four ways you can put the torque arm on the axle. Try the other three to see which gives the best angle.

The disc spacing doesn't look right either. You've spaced the axle away from the frame, then spaced the disc away from the motor back towards the frame. Surely, one is cancelling the other out. Normally, you have the disc hard up against the motor, then a single washer on the axle to line it up with the caliper.

 

[emjay]

Thanks for the quick reply. I'll take a look at filing the dropouts and modifying the torque washers. Any suggestions on the best tools for filing? I have hand files but would definitely be prepared to try a quicker way

You're absolutely right about the two sets of washers cancelling each other out - the problem is that I need the washers on the axle to prevent the hub housing rubbing against the brake caliper.

 

[Nealh]

Use a Dremmel or similar multi tool but go careful and only take a little out at a time or use a rat tail file. If the washers don't do the job then go up to a larger disc rotor and adapter.

 

[anotherkiwi]

Hand filing aluminium is not a time consuming task. A steady hand and a keen eye are all you need. I hand filed out steel dropouts to fit my motor and it took all of 5 minutes.

 

[Deleted member 4366]

You should be using a 180mm disc.

 

[emjay]

OK, so if I get a mounting adapter and fit a larger rotor, then the caliper will be further away from the hub so I won't need to space it right? Does anyone have a link handy to the kind of adapter I'd need - I had a quick look but all I can find are IS/post adapters, which I don't think is the kind that would work here.

 

[Deleted member 4366]

http://www.ebay.com/itm/180mm-160mm-Caliper-Bicycle-Bike-Disc-Brake-Mount-Adapter-IS-POST-for-Front-Rear-/122651540059?var=&hash=item1c8e99fa5b:m:miBAsE103DhcdwFmQPr741Q

Front IS 203/rear IS 180mm

 

[emjay]

Thanks for the link! So, just to be clear, this part will replace the similarly-shaped part that is currently joining the brake caliper to the frame, right? Will I need to replace the caliper itself?

 

[Nealh]

Calliper remains unchanged.

 

[Deleted member 4366]

It's just a bracket to hold the caliper further out. You already have one, but the one you have holds it at 160mm instead of 180mm. You can achieve the same thing with 10mm of washers beween the caliper and the adaptor, then use longer bolts.

 

[emjay]

Thanks all! New bracket and disc ordered, stay tuned for round two of assembly soon

 

[emjay]

Update: build/ride report here for anyone interested:

http://www.pedelecs.co.uk/forum/threads/q128c-25mph-fast-hybrid-commuter-build-ride-report.29244/