Rear hub conversion. gears / freehub issues.

[scofield]

Recently converted a bike with a rear hub kit. Used it a fair bit already but never got round to sorting the gears out as I don't have a clue. I've just been using 2 or 3 gears and the motor does most of the work, I just don't want to be ghost pedalling at 15MPH all the time.

I did have a go at setting up the gears, it's a 7 speed freewheel that came with the kit and I'm unable to use the highest gear even with washers on the inside of the dropouts, there isn't quite enough clearance for the chain between the smallest cog and the frame.
I don't know what the best solution is for this. With the current 2 washers on the inside of the dropouts, it is already a snug fit. It pushes the dropouts apart slightly, so I'm not sure adding another washer would be a good idea? Or just go down to a 6 speed freewheel so the lower stack height will allow the clearance? I think we're talking a couple of mils of clearance needed here.

 

[Scruffydroid]

Add another washer, the steel chainstay can definitely handle it.

Reindex the gears after adjusting the end stops.

 

[scofield]

Add another washer, the steel chainstay can definitely handle it.

Reindex the gears after adjusting the end stops.

It's an aluminium frame though, i'm not sure how tolerant it is if the chainstay were flexed further apart. As I say, it already is a fairly tight fit as it is.

 

[Nealh]

One can spread an ali frame by quite a bit 20mm is doable over a few days by using blocks and wedged to spread them so 1- 2mm should be no issue for another washer.

 

[Scruffydroid]

I spread my aluminium stays apart using a tyre iron to wedge my hub motor in with the additional washers. No issues at all ...

 

[scofield]

I hope so, my doubts only arise from what i've read elsewhere that say it's likely to cause cracks.

 

[Tony1951]

If you can get a six seed freewheel in, I'm not sure why you want to persist in spreading the alu frame. The presence of the hub motor makes a lareg number of gears somewhat redundant.

Why take the risk? We know what happens to aluminium frames when over stretched. This is true whether or not some of us have got away with it in the past. Ask any aeronautical engineer wether it is a good idea to bend alu frames. Aluminium structures that have been over stretched have a habit of catastrophic failure. That's a fact.

 

[Nealh]

A bike and aeronautics are chalk and cheese, the latter suffering from compression issues and much greater speed and stress. I would be more concerned with CF bike giving way under me then a 1 - 5mm gentle stretching of rear ali bike stay's.

 

[scofield]

The washers in place are about 3mm thick each and it slots in with a little persuasion. I think an extra 1mm on the chain side would be enough. If simply using an m14 shim washer would fix it without needing lots of force, that would be much easier and cheaper!

 

[Scruffydroid]

If your brake disk is correctly aligned on the left side, don't add any washers to that side.

 

[scofield]

I just stuck a 0.8mm washer on the chain side and that just about did the trick. The bikes been making a racket and I thought it was probably to do with the drivetrain, but now I believe it's the spokes as it's only under load. Onto the next problem...

 

[Scruffydroid]

I just stuck a 0.8mm washer on the chain side and that just about did the trick. The bikes been making a racket and I thought it was probably to do with the drivetrain, but now I believe it's the spokes as it's only under load. Onto the next problem...

I'm not sure I understand how the spokes make a noise? Can you post a video clip from before you initiate the wheel turning up to the sound becoming evident?

 

[Nealh]

Incorrect or loosely tensioned spokes can creak.

 

[Scruffydroid]

Incorrect or loosely tensioned spokes can creak.

I didn't think of the creak too early in the morning.