Help! Bottom bracket nut loosening on Tongsheng TSDZ2

[DarkerSide]

The nut delicately highlighted in red keeps loosening (twice in 150km). This causes the cranks to rock.


I've just greased it again and tightened it up with a large lockring spanner rather than the included tool to try and get more torque on it. Any other thoughts?

Possible factor - I spaced out one of the bolts with a tiny washer (yellow arrow), because tightening it all the way down without the washer was pivoting the black plate behind the main nut away from the bottom bracket frame. I'm sure it's not meant to do that, but I suppose there's an outside chance it's meant to be some kind of spring tension thing to stop the nut loosening under load...

Cheers

Rob

 

[TJS109]

Hi,
Mine did continually, I had to use some form of thread lock to stop it

Tim

 

[u1v1w1]

Same here. Decided to cut the spanner provided with the motor so it can be used while riding. Turns out it's too flimsy. Then decided to grease the bottom bracket shell to reduce the probability of frame damage while putting some blue locktite on locknut threads, but can't seem to undo the locknut now with a taping method. BBT-18 8 notch too probably won't fit there. Looks like castle sockets with 40mm inner diameter aren't available. Just need something good enough to be able to tighten it with 40Nm of torque. The upper plate of anti-rotation bracket seems to be bending slowly while tightening the bolt, so that one also has to be tightened periodically.

 

[Nealh]

The nut delicately highlighted in red keeps loosening (twice in 150km). This causes the cranks to rock.
View attachment 34948

I've just greased it again and tightened it up with a large lockring spanner rather than the included tool to try and get more torque on it. Any other thoughts?

Possible factor - I spaced out one of the bolts with a tiny washer (yellow arrow), because tightening it all the way down without the washer was pivoting the black plate behind the main nut away from the bottom bracket frame. I'm sure it's not meant to do that, but I suppose there's an outside chance it's meant to be some kind of spring tension thing to stop the nut loosening under load...

Cheers

Rob

Use another M33 lock nut so that one tightens against t'other, BBS for instance comes with two.

 

[MontyPAS]

The nut delicately highlighted in red keeps loosening (twice in 150km). This causes the cranks to rock.
View attachment 34948

I've just greased it again and tightened it up with a large lockring spanner rather than the included tool to try and get more torque on it. Any other thoughts?

Possible factor - I spaced out one of the bolts with a tiny washer (yellow arrow), because tightening it all the way down without the washer was pivoting the black plate behind the main nut away from the bottom bracket frame. I'm sure it's not meant to do that, but I suppose there's an outside chance it's meant to be some kind of spring tension thing to stop the nut loosening under load...

Cheers

Rob

Unfortunately it is another of the TS's poor design features. It is supplied with only one M33 nut. It really needs two, or a good measure of blue locktite and hammering on with the wrench!

The anti rotation chainstay clamp / bracket design is bad as well. It is pulling against the rotation of the motor forces. I fitted a TS to an elevated chainstay steel frame, therefore had to put a bracket in front of the motor which pushes against the rotational forces. A much better option and proving to be rock solid.

 

[peter.c]

Unfortunately it is yet another ts niggle, i make up anti turn brackets and gouge marks on the inside of the new washer [the bbs has dimples] use loctite and hit the spanner with a mallet Not a problem if the rear mount is used and tight onto the stays .
But a headache if fitted to a full suspension bike or a fat bike
Its just routine another routine maintance job like checking the lh side pedal crank is tight yes the supplied spanner is made of cheese
Good idea Nealh i have a spare off a bbs will try it [if i ever use a tsdz2 again ]
PS always rest the motor against the frame tube

 

[u1v1w1]

If the supplied spanner is proprietary then using torque wrench as recommended in TSDZ2 manual (40Nm) is impossible.

 

[MontyPAS]

If the supplied spanner is proprietary then using torque wrench as recommended in TSDZ2 manual (40Nm) is impossible.

40nm = two hard wacks on the spanner with a heavy mallet!

 

[Swizz]

I made a new chainstay mount from a tubenut and a setscrew. I was not impressed by the supplied method as the cast ally bit did not like my chainstays & in any case, the elongated slot is just destined to allow movement.

The bottom of mine butts up beneath the driveside chainstay & it uses the supplied elongated washer on top, effectively stopping the torque reaction from the motor and any kickback in the other direction.

I did not assemble the m33 locknut with any Locktite and am just keeping an eye on it coming loose to see whether it works or not.

 

[Nealh]

Buy and fit a Bafang lock nut or another generic type.

4 Pcs M33 x 1.5mm Pitch Slotted Round Nuts GB812 for Hook Spanners | eBay

Description: M33 thread diameter, 1.5mm pitch, carbon steel material. Design with thread inside, 4-slot slotted round nut. Operated with hook spanners (not included here). Used widely for roller bearing, axial shaft, pump valve, etc.

www.ebay.co.uk

 

[u1v1w1]

I made a new chainstay mount from a tubenut and a setscrew. I was not impressed by the supplied method as the cast ally bit did not like my chainstays & in any case, the elongated slot is just destined to allow movement.

The bottom of mine butts up beneath the driveside chainstay & it uses the supplied elongated washer on top, effectively stopping the torque reaction from the motor and any kickback in the other direction.

I did not assemble the m33 locknut with any Locktite and am just keeping an eye on it coming loose to see whether it works or not.

Same here, probably will have to wait until it losens by itself so I can replace it with a generic Bafang one. Will have to postpone the intended greasing of the bottom bracket shell, can't expect to do it right the first time.

 

[u1v1w1]

Use another M33 lock nut so that one tightens against t'other, BBS for instance comes with two.

BBS style locknut comes in 7.5mm thickness, which means that there will be not enough room for two. Will have to resort to nord lock washer which is 5.8mm in thickness according to data sheet. This will make the locknut flush with the outer part of the axle hausing while not leaving any exposed threads (reduced possibility of damage and contamination).

 

[DarkerSide]

My solution has been to carry around a lockring spanner and tighten it whenever it loosens (which has been about every 300km). As some have pointed out, this could be managed with regular maintenance rather than being reactive, but I would inevitably forget one month and be caught out...

The spanner I carry is something like this, which avoids the need to remove the crank arm.

Ice Toolz BB and Headset Lockring Tool | Tredz Bikes

Save 29% - Ice Toolz BB and Headset Lockring Tool £4.95 or available with 0% APR finance on baskets over £99. All Bottom bracket tools are delivered free to the UK mainland*, 365 day returns & Price Match. Buy Now.

www.tredz.co.uk

 

[Nealh]

Although the 7.5mm locknut doesn't fully wind on it will have enough purchase to lock against the first one.

 

[peter.c]

made an anti turn bracket problem solved needs a 33mm hole saw same for tsdz2

 

[u1v1w1]

My solution has been to carry around a lockring spanner and tighten it whenever it loosens (which has been about every 300km). As some have pointed out, this could be managed with regular maintenance rather than being reactive, but I would inevitably forget one month and be caught out...

The spanner I carry is something like this, which avoids the need to remove the crank arm.

Ice Toolz BB and Headset Lockring Tool | Tredz Bikes

Save 29% - Ice Toolz BB and Headset Lockring Tool £4.95 or available with 0% APR finance on baskets over £99. All Bottom bracket tools are delivered free to the UK mainland*, 365 day returns & Price Match. Buy Now.

www.tredz.co.uk

How is it possible to know when does it becomes loose while riding. I guess by the squeaking sound. Doesn't that lead to damaged threads in the bottom bracket shell. Mine have bitten in the motor axle housing while being flattened a bit. The squeaking was detected 7 miles before stopping and figuring out what's wrong.

 

[u1v1w1]

Although the 7.5mm locknut doesn't fully wind on it will have enough purchase to lock against the first one.

According to article below the second nut may prevent only from thread stripping in this case since the first nut should be tightened to 50% of full torque, which means that there will not be sufficient engagement of the threads on the second nut to withstand full torque, as far as I understand.

The Use of Two Nuts to Prevent Self Loosening of Fasteners

 

[u1v1w1]

View attachment 38493

made an anti turn bracket problem solved needs a 33mm hole saw same for tsdz2

I think the original anti-rotation bracket is sufficient enough if the bolts are not overtightened to the point of deformation of upper plate, since it relies in tension, not on compression. The main reason for the need to M33 locknut to be tight is to prevent radial movement which can damage frame. Although your also design might reduce the radial movement to some degree. Not sure yet if I want rivnuts or hose clamps around the frame tubing.

 

[MontyPAS]

How is it possible to know when does it becomes loose while riding. I guess by the squeaking sound. Doesn't that lead to damaged threads in the bottom bracket shell. Mine have bitten in the motor axle housing while being flattened a bit. The squeaking was detected 7 miles before stopping and figuring out what's wrong.

How is it possible to know when does it becomes loose while riding.
You will know by the movement felt in the pedals and the motor unit banging about

Doesn't that lead to damaged threads in the bottom bracket shell.
Why worry about the threads on the BB shell. They are obsolete once you remove the bottom bracket/crank-set and install the motor unit!

 

[MontyPAS]

I think the original anti-rotation bracket is sufficient enough if the bolts are not overtightened to the point of deformation of upper plate, since it relies in tension, not on compression. The main reason for the need to M33 locknut to be tight is to prevent radial movement which can damage frame. Although your also design might reduce the radial movement to some degree. Not sure yet if I want rivnuts or hose clamps around the frame tubing.

I think the original anti-rotation bracket is sufficient.
Its clearly not as the amount of users reporting issues, its a poor design and is supplemented by the tightness of the M33 locknut.

Not sure yet if I want rivnuts or hose clamps around the frame tubing.
Don't see any other way of fixing a properly implemented anti rotation bracket. A braze on fixing would be ideal, but unfortunately frame makers are not making frames for after market fitting of Bafang/TS units?