Bafang inner lock ring spanner - open jaw

[JayDG]

I clearly didn't tighten the Bafang inner lock ring sufficiently when I did DH's bike, so needed to sort that just now.

I've managed to bodge tightening it, but an open-jawed spanner would be useful for the future. I've heard folk on here mention them, but my Google-fu is failing me.

Can anyone point me to a suitable open-jawed spanner available in the UK please?

(I have a ring spanner, but that necessitates removing the crank - which wouldn't be an issue except that my crank puller is currently an integral part of the old crank, and is taking some releasing!)

 

[peter.c]

The open jaw i had flexed when tapped with the rubber mallet the inner nut has to be retightened after initial use the washer has to bite into the frame,[ that's why it has a raised side] if this does not solve the problem fit/make an anti turn bracket

 

[JayDG]

The open jaw i had flexed when tapped with the rubber mallet the inner nut has to be retightened after initial use the washer has to bite into the frame,[ that's why it has a raised side] if this does not solve the problem fit/make an anti turn bracket

Where did you get your openjaw?

 

[peter.c]

Ebay but made out of butter steel waste of money if space is tight a pin punch and a hammer on the 1st nut a shimano hollow tech bb spanner will fit the outer nut and loctite

 

[JayDG]

Ebay but made out of butter steel waste of money if space is tight a pin punch and a hammer on the 1st nut a shimano hollow tech bb spanner will fit the outer nut and loctite

Ha, ok, thanks. Got the open spanner for the outer nut. Will try that method on the inner one if needed!

 

[Nicholas Hammond]

The ring spanner will fit over the crank arm with the pedal removed, there is no need to remove the crank

 

[Deleted member 16246]

I bought a converted Specialised bike with a Bafang 250 watt motor and within a hundred miles the motor was flopping about. I contacted the builder who knew I had some tools and knew how to use them and he advised that I could either bring it back and he would re-tighten the nut, or I could take a punch and bray the beggar with a hammer to tighten it. This I did and it has not come loose since. in about another three hundred miles. The large steel ring with slots cut out of it is hard stuff and can take that kind of treatment without harm. The aluminium lock ring which goes over the top, much less so. You can still use the method,but it will be marred a bit.

The other thing to watch on a newish conversion is the tightness of the crank bolts. You REALLY don't want those coming loose as they will rapidly be destroyed as the aluminium wears on the bottom bracket fittings.

 

[Raboa]

This might work:

HCW-5 Bottom Bracket Wrench — Cup-and-Cone Lockring

A double-ended wrench for notched lockrings commonly found on adjustable cup-and-cone bottom brackets.

www.parktool.com

 

[Deleted member 16246]

This might work:

HCW-5 Bottom Bracket Wrench — Cup-and-Cone Lockring

A double-ended wrench for notched lockrings commonly found on adjustable cup-and-cone bottom brackets.

www.parktool.com

It MIGHT work, but those pegs are not the right shape to get really good engagement in the square sided slots of the main lock ring which is the one which needs to be really tight. I think (from memory) it needs to be tightened to about 50 NM.

Since the correct spanner is readily available, the right size and right profile, I'd be going for that one, and as someone said elsewhere, if you take off the pedal, you can slot the pegged ring spanner over the crank and don't have to remove the crank arm, which can be a pain.

The dealer who built my bike says he has made hundreds of conversions over a couple of years and that nut coming loose is a very common issue. In fact, he has had torque arms made which fit the Bafang motors and then fasten to the chain stay to prevent the forces unwinding it, for use mainly in high power motors such as 500w and 750 watt motors which he sells most of. I doubt my brutal method would have worked on a motor with three times the torque of my BS01 250 watt motor. At peak power even mine is drawing a bit more than 500 watts.

This is an example from an EU supplier:

https://fasterbikes.eu/en/accessories/tools/

 

[Fordulike]

Where did you get your openjaw?

I tried one of those open jaw spanners when I first fitted my kit. The trouble is, with the version I got anyway, is that it's too thick where the jaw joins the handle. This meant it could only be used it certain positions to tighten the lockring. A right pain in the arse.

Nowadays, I use one of the full double ended spanners, and just remove the pedal and slip it over the crank arm, when I want to retighten or do maintenance.