Praxis crank binding

[Binhill1]

Really struggle to get these cranks off the Levo . They crack open maybe quarter a turn or less then bind up for a couple turns before you can feel them getting loose. Always been like this since i got the bike . Had to use mash hammer on hex to loosen .When i tighten it it just stops dead no feel to it if you know what i mean. They were put on 6 weeks ago in shop so cant confirm torque but as i say always been torture to get off. Just wondering if this is normal. Might be easier with a muckle ratchet or tommybar ????

 

[NULevo]

Really struggle to get these cranks off the Levo . They crack open maybe quarter a turn or less then bind up for a couple turns before you can feel them getting loose. Always been like this since i got the bike . Had to use mash hammer on hex to loosen .When i tighten it it just stops dead no feel to it if you know what i mean. They were put on 6 weeks ago in shop so cant confirm torque but as i say always been torture to get off. Just wondering if this is normal. Might be easier with a muckle ratchet or tommybar ????

Mine are exactly the same, and always have been. They have thread lock on from the original build at the shop, which might be a cause of the binding. I always assumed they were meant to be like that.

 

[Binhill1]

Mine are exactly the same, and always have been. They have thread lock on from the original build at the shop, which might be a cause of the binding. I always assumed they were meant to be like that.

You would think the threadlock would be gone by now though . As you say maybe meant to be . Thanks. If were wrong we will be told thats the good thing about this forum. Think i may change the bolts the non drive side is getting rounded.

 

[NULevo]

My non drive side is the only one that I've removed, probably 5-6 times in 2 years. The threadlock is still there and seams to work its way into the tread, even though I've never added any myself.

 

[Binhill1]

My non drive side is the only one that I've removed, probably 5-6 times in 2 years. The threadlock is still there and seams to work its way into the tread, even though I've never added any myself.

View attachment 79925

Looks very clean to me . Yes ive only had other side off once for sending motor away it came of easier. Non drive side maybe a dozen times to clean mud or to take battery to motor cable off to dry it out.

 

[Mikerb]

I can think of no reason to use threadlock on a self extracting crank and a few reasons not to!

The syndrome explained above of the bolt loosening slightly then binding is evidence of no lube between the bolt and the extracter head and/or corrosion build up on the bolt threads. The bolt loosens slightly until it comes up against the face of the extractor......then there is a lot of friction especially if dirt/water has got in there.

The crank is held on by being pushed onto splines that have a very slight taper but then a ramp at the end of the spline. The correct torque ensures the crank is pushed hard against that ramp ( which if you like a cts as a reversed spring washer) but applied torque will be incorrect if there is friction to overcome on the splines. So the spines and the crank should be thoroughly cleaned and then should be lightly greased, the inside face of the bolt should be greased and the inner face of the exractor also smeared with a little grease. The crank is open to the elements so the light smear of grease also helps to protect against corrosion. Normal crank torque is anything from 40 to 54nm..........that is the calculated torque to achieve maximum thread friction and needs to be exact.

 

[Binhill1]

I can think of no reason to use threadlock on a self extracting crank and a few reasons not to!

The syndrome explained above of the bolt loosening slightly then binding is evidence of no lube between the bolt and the extracter head and/or corrosion build up on the bolt threads. The bolt loosens slightly until it comes up against the face of the extractor......then there is a lot of friction especially if dirt/water has got in there.

The crank is held on by being pushed onto splines that have a very slight taper but then a ramp at the end of the spline. The correct torque ensures the crank is pushed hard against that ramp ( which if you like a cts as a reversed spring washer) but applied torque will be incorrect if there is friction to overcome on the splines. So the spines and the crank should be thoroughly cleaned and then should be lightly greased, the inside face of the bolt should be greased and the inner face of the exractor also smeared with a little grease. The crank is open to the elements so the light smear of grease also helps to protect against corrosion. Normal crank torque is anything from 40 to 54nm..........that is the calculated torque to achieve maximum thread friction and needs to be exact.

Yes i dont see any signs of threadlock on mine and i just put bit of grease on bolt. As i said it goes on ok but stops dead, motor only 5 weeks old so bolts and crank will be more likely the issue . I need to borrow bigger torque wrench just to make sure torque is ok.