Bafang spokes breaking

[MaxMachin]

Hello.

I've been reading about other peoples issues with spokes breaking and it seems like I'm not the only one!

I have a rear wheel motor,700x32c tire with 36 spokes (2.6mm section?). I bought it whole from bms batterys.
The battery is on the back too so a fair load on the back and probably 18miles/day on tarmak with potholes!

I wondered if in the first place the tire should be a mountain bike tire (need to change mudguard) and if on the whole I should use a double suspension mountain bike in stead of my Specialized Globe Daly!

So after about 2 and a half months of riding 2 spokes broke at the hub end. I had them replaced with 2.3mm section spokes (for motorbikes according to the bike shop). 2 weeks later another 2 spokes break!

I'm now wondering if I should replace all the spokes, the rim, change the tire to a thicker one ot just start again from scrach with a mountain bike!

In any case the weel needs repairing and Ifound a couple of threads pointing to catsnapper's spokes and others... I will have to replace them all but any thoughts on the tire or rim replacement would be good.

Cheers

Max

 

[KTM Bike Industries UK]

just google red bull rampage crash to see what spokes can cope with, if they are good quality and well built.

you don't need a new bike, you just need some good quality spokes, and possibly / probably a better rim.

Any bike shop that are selling you "motor bike spokes" doesn't deserve you're business.

 

[trex]

welcome to the forum Max. Lots of members have had problems with spokes breaking on their rear wheel hub motor, you are not alone.
You only need to replace broken ones but you will need to master the black art of wheel truing, that's the only way to get rid of the problem.
Spokes break when compressed, when the motor wheel hits a bump or pothole. The only way to keep them is not to let them lose their tension, check regularly and tighten loose ones.

 

[Deleted member 4366]

It seems occasionally our Chinese friends can't control the specification of the wire they use for making the spokes, and then they start suffering fatigue. Once four have broken, you can be sure that the rest will succumb to the same fate sooner or later. The only solution is to rebuild the wheel properly with good quality spokes. Then, it'll last a life-time. You don't need thicker spokes. In a 700c wheel even 14g spokes will work.

If you have a Chinese wheel with cheap spokes, it doesn't mean that they'll break. Most don't, but some do. It's the luck of the draw whether you get the bad steel when its quality is not guaranteed.

 

[trex]

I think the problem with Chinese spokes is not so much in the quality of the spokes as in not doing the wheel truing properly. Few factories have automatic spoking machines - unless you true the wheel yourself, there is no guarantee that the tension is correct. Spokes that have low tension will loosen and break.
I used to set my 2.3mm stainless steel spokes on 8-Fun SWX rear motor to 1000N without a single broken spoke before moving to crank drive. If you have 8-Fun BPM motor, you should increase spoke tension to 1200N. 1000N is 27 on the Parktool TM-1 deflection scale.

 

[Kudoscycles]

Checking and adjusting spoke tension is a maintenance issue,more so on electric bikes-normally heavier riders,the extra torque loading of the motor and additional weight of bike.
I currently have a customer who has ridden his bike for over 12 months,never checked or adjusted the spokes(in fact never checked and adjusted anything!),he has taken it into a bike shop for repair of one broken spoke,they told him that all the spokes need checking on front and rear wheels-he has told them just to replace the broken spoke,he will be back!
So many think they can ride these bikes without any maintenance at all.
KudosDave

 

[trex]

broken spokes is an issue only for rear hub motors because the motors' rotational inertia inflates the forces applied to the spokes when you brake hard or when you hit a bump. Front hub motors don't suffer as much because the motor is mounted on suspension forks. Crank drives never suffer from this problem.

 

[Deleted member 4366]

Crank drives never suffer from this problem.

Apart from 28 spoke Kalkhoffs (if there's any left).

 

[mike killay]

broken spokes is an issue only for rear hub motors because the motors' rotational inertia inflates the forces applied to the spokes when you brake hard or when you hit a bump. Front hub motors don't suffer as much because the motor is mounted on suspension forks. Crank drives never suffer from this problem.

Er, yes they do, my Tonaro crank driver broke a rear spoke.

 

[MaxMachin]

Well looks like I'm going to be rebuilding my first wheel

Ive just talked to http://www.tillercycles.co.uk/ and he said that the chinese bafang motors are known to him... Basically he said that the quality of the spokes is bad and that they often have problems.

I asked about the rim and he said that if it is double lined? it is ok and if it is eyelited then even better. I'm pretty sure it is double.
I agree that cheking spoke tension regularly would probably help no end to solve the issue and I have to say that I didn't do it in the first 2months of riding when the first 2 spokes went but when i got them replaced they should have been all tensioned correctly (and i think they were by a trusted shop) so to have 2 more go 2 weeks later would point back at the quality.

 

[trex]

spokes get loosened with vibrations from the motor. Some people use linseed oil or blue loctite to reduce the effect of vibrations but you still have to check them regularly. Invest in a £2 spoke key!

 

[Deleted member 4366]

When Saneagle put his new Q100 motor in his bike after his Q128 started breaking spokes, he checked and tensioned all the spokes. then he applied a drop of superglue to each nipple (on the wheel of course).

We were out riding a few days ago and I could hear that characteristic spoke noise coming from his bike, so, when we stopped at the pub, I got my spoke key out and started to check them. Every spoke was loose, but I couldn't turn any of the nipples because of the glue. None have broken yet! I wonder how long it will last, and i also wonder how they came loose without the nipples turning.

 

[trex]

i also wonder how they came loose without the nipples turning.

the holes on the hub shell are worn?

 

[flecc]

i also wonder how they came loose without the nipples turning.

Or thread stretch possibly?

 

[grldtnr]

Or thread stretch possibly?

talking as a cyclist who suffered spoke breakages, the only surefire way to deal with this is to have hand built wheels.

machine built wheels just don't cut it.

 

[flecc]

talking as a cyclist who suffered spoke breakages, the only surefire way to deal with this is to have hand built wheels.

machine built wheels just don't cut it.

Fully agree, most of the trouble is the poor build quality of so many manufacturer's wheels. Machine builds can produce wheels that are true but often with very uneven spoke tensions.

The spokes themselves are rarely an important factor, I've used 14 gauge low cost spokes on hub-motor, heavily dished, 20" rear wheels with no subsequent trouble whatsoever, despite very high load applications and heavy towing duties.

 

[KirstinS]

talking as a cyclist who suffered spoke breakages, the only surefire way to deal with this is to have hand built wheels.

machine built wheels just don't cut it.

This

Never had any issues with my handbuilt wheels (by OnOne in Sheffield )

And several on my Chinese hub (front one at that)

 

[mike killay]

Fully agree, most of the trouble is the poor build quality of so many manufacturer's wheels. Machine builds can produce wheels that are true but often with very uneven spoke tensions.

The spokes themselves are rarely an important factor, I've used 14 gauge low cost spokes on hub-motor, heavily dished, 20" rear wheels with no subsequent trouble whatsoever, despite very high load applications and heavy towing duties.

Is this the real trouble then?
Spokes unevenly tensioned.
Would just evening up the tensions work?

 

[flecc]

Is this the real trouble then?
Spokes unevenly tensioned.
Would just evening up the tensions work?

It often can, but often difficult if with badly unbalanced tensions. That can mean slackening all the spokes right off and starting again from scratch. Trying to juggle with two or three spokes at a time to get it right is rarely successful on a badly built wheel.

 

[MaxMachin]

Hello.

Update on this.
I got 36 of 2.3mm Sapim Leader spokes form Graham http://www.tillercycles.co.uk/ Very good service and fast delivery and good quality. Very nicely threaded and so on.
I had them fitted as I decided that the "dark art" of trueing wheels may have to wait till I have more space, time and tools.
Collected the bike yesterday morning and did my usual commute (18 miles) by the time I got home last night the wheel was all over the place again. 3 spokes totally loose and others too tight and so on.
Drop the bike off this morning and was told that the wheel was built well, that possibly the rim isn't strong enough (chinese), my riding was too harsh, too much wait on the back or all of these together.

I'm thinking about changing the rim now as if it is basically too flexible this would make the spokes come loose and as soon as one is loose the rest will follow.

Thoughts?