Nexus 8 still slipping

[vandjq]

In May after a long discussion in this forum I claimed on the warranty for my Nexus 8 hub. In July the shop I bought it from fitted new internals to the wheel. But when I tried to fit the wheel to the bike I was unable to tighten the axle nuts. I thought this was caused by damage to the frame drop-outs when the axle slipped, so I claimed on the Cube 6-year frame warranty. But the shop rang me up and said that although the frame was damaged, that was not the reason I was unable to tighten the nuts. They said it was caused by the (new) axle being too long, so it was impossible to tighten the nuts because they could not mate with the non-turn washers. So as well as a new frame I needed yet another new set of internals.

On Saturday I took delivery of the bike with a new frame and internal gears. I am able to tighten the axle nuts to 35 foot-pounds, so presumably the axle is the correct length. But I am not able to align the yellow marks on the cassette joint properly. They will line up from gear 1-4, but going from 5-4 they are out by more than the width of the mark. This has me baffled because before claiming on the warranty I had replaced the shifter and cable and followed Brucey's instructions on grease/oil and the marks lined up perfectly in both directions. As far as I can tell, the shop just transferred everything from the old frame to the new one, and there was no reason to dismantle anything. This bike has never worked properly for the last two years and has been at the shop for 8 of the last 12 months. I have completely lost confidence in their ability to fix it and would be most obliged for any advice from the forum.

[Brucey]

almost certainly your cable is no good.

cheers

[vandjq]

Brucey - this was the third new cable, which came fitted to a brand new shifter, waterproof boot and metal ferrule from SJS cycles:




It was carefully assembled according to your instructions re Teflon grease/oil. I used the special tool to make sure the cable was the correct length.
And it was only used once on the road. What could possible be wrong with it?

[Brucey]

it doesn't mean that it is properly lubricated, in well prepped housing and installed without kinks though. The other thing to look for is that the reaction arm on the cassette joint is not moving around.

Finally I would say that there are some other things that might no be quite right; for example

- if the NTW tabs are not a snug fit in the dropouts then the axle may still move around in service. This can be bad in its own right and can also cause gear selection issues because the reaction arm on the cassette joint can be pulled around by the cable as the hubs moves.

- if the axle is not installed stress-free, (i.e. it is flexed in bending all the time) the shifting inside the hub can be impeded. If the belt tension is too high and/or the hub bearings are not correctly adjusted this can happen.

cheers

[vandjq]

Brucey - thanks for that.

Would it be wise to replace the cable and housing, which only costs £12 with a new shifter from SJS?

Although the NTWs are made of steel, should I replace them anyway as they may have been worn by the movement of the axle?

Although the new frame can be used with a belt I am using a chain, which is too tight. The new frame has an eccentric bottom bracket clamped with two Allen bolts. But there is only one hole which passes through each side of the bracket. How do I move it?

How do I ensure that the hub bearings are properly adjusted? I'm a bit nervous about opening up the hub.

[Brucey]

Brucey - thanks for that.

Would it be wise to replace the cable and housing, which only costs £12 with a new shifter from SJS?

Although the NTWs are made of steel, should I replace them anyway as they may have been worn by the movement of the axle?

Although the new frame can be used with a belt I am using a chain, which is too tight. The new frame has an eccentric bottom bracket clamped with two Allen bolts. But there is only one hole which passes through each side of the bracket. How do I move it?

How do I ensure that the hub bearings are properly adjusted? I'm a bit nervous about opening up the hub.

if the cable is working badly it either means that it is not good enough or it is installed badly.

NTWs wear, so replace them. However they still may not fit the frame properly.

The owner's manual ought to have instructions for adjusting the BB. The method varies with the design.

The hub bearings should be neither slack nor tight. It isn't difficult to adjust/check the bearings but if you have not done it before this is not the hub to try first.

If the chain is very tight this won't do any good whatsoever; depending on how tight it is, it may even break something.

cheers

[vandjq]

Brucey - the Cube manual is a generic one printed in 2015 and does not mention BB adjustment. The BB is called a Thun Zumba but their website does not appear to have any manuals or instructions.

[Brucey]

the eccentric is nothing to do with who made the BB bearings; it is a cube thing not a thun thing.

cheers

[vandjq]

Well I can't find out how to move the bottom bracket to adjust the chain. But as there is just a hole from one side to the other I reckon I could slacken the clamp then pass a thin bar such as an Allen key through it then push/pull it backward and forwards?

[Brucey]

that sounds reasonable (and often using something like a big allen key as a lever between the BB spindle and whatever you put in the hole would be the thing to do) but without seeing it, it is impossible to be sure. BTW when building up a new frame, it is a really good idea to remove an accentric and to grease it thoroughly, so that you have a fighting chance of moving it later on.

cheers

[zenitb]

Well I can't find out how to move the bottom bracket to adjust the chain. But as there is just a hole from one side to the other I reckon I could slacken the clamp then pass a thin bar such as an Allen key through it then push/pull it backward and forwards?

vandjq..I have a 2018 Cube Travel Pro ..is that the model you have? (The 2017 model had a chain. Or maybe you have the Cube Hyde which is the same bike sans mudguards, lights and rack?)

Anyway I adjusted my eccentric bottom bracket (EBB) in roughly the way you describe. My Cube's EBB is an open shell design held together at the bottom by clamp bolts (as you seem to describe - different to the more traditional "closed" EBB shell I have on my tandem). I loosened the pinch bolts and then jammed a screwdriver through the hole you describe and just wrenched the EBB around with it to adjust. However my cube is belt drive (not chain drive) and I had to take the rear wheel out temporarily because I could not move the EBB accurately against the tension of the belt. Once the tension of the belt had gone the EBB moved easily in the shell. I used a pencil mark accross the EBB and its shell and used a process of trial and error to get the right position for the EBB..relative to the pencil mark on the shell..removing and reinstalling the rear wheel several times (in the case of belt drive i had to use a Gates phone app to check belt tension each time - mega tedious..chain tension can just be checked manually)

I have ordered a Park Tools EBB pin tool now which I can hopefully use next time...but the "jam a screwdriver in and tug" method does work..you just need some patience moving the EBB shell to the exact right place.

Incidentally the "open" EBB shell design used by Cube looks vulnerable to corrosion given the big gap in the EBB shell that is left underneath the bike..right in the path of front wheel spray...especially given its supposed to be a low maintenance bike!!

(Brucey's comment on greasing EBB noted..next time!! )

[vandjq]

zenitb - My Travel Pro is the 2016 model, which came with a chain. Unfortunately I had a lot of bother with it and the shop replaced it with the same frame as yours. I am curious about the tool that you have ordered as I had one from Park Tools which had two pins, like this one:



Which I used to adjust the BB in my old frame. That will not work on my new BB, but I would like to get one that will in order to avoid messing around with screwdrivers, Allen keys etc.

Thank you for your input. Is your IGH reliable?

[vandjq]

Well, I replaced the cable and shifter for the fourth time, and the axle nuts and the non-turn washers. But I still have a problem. I have not been out on the road since I got my new frame and hub for fear of damaging something. But in the workshop when I turn the shifter from 1-4 to check the alignment of the yellow marks, then turn back from 4-1, the yellow marks stay lined up and the cable does not move. I used the merest smear of Teflon grease and some cycle oil to lubricate the cable. Could it be the only thing I have not replaced, i.e. the cassette joint?

[Brucey]

there is a basic problem with the shift mechanism in the hub or with the cassette joint or the cable. You can diagnose these things one at a time by

a) disconnecting the cable and moving the cassette joint by hand; does it spring back at you?

b) removing the wheel and trying the same thing. If it moves OK once the wheel is out, something is binding when the wheel is installed.

c) remove the cassette joint and sprocket. Is there something out of whack?

A final comment is that fixing bikes is not like fixing computers; a list of instructions is all very well but if you are not looking for the right thing it is easy to miss something important and to end up with a system that doesn't work. You ought to have all new parts and yet you have a system that doesn't work. Almost certainly you have overlooked something and you may continue to overlook that thing no matter how many times you look at it.

In this situation the best thing you could do is seek some help from someone who knows about these hubs and/or fixing bikes. There may be a co-operative cycle workshop near you, they may be able to help.

cheers

[zenitb]

zenitb - My Travel Pro is the 2016 model, which came with a chain. Unfortunately I had a lot of bother with it and the shop replaced it with the same frame as yours. I am curious about the tool that you have ordered as I had one from Park Tools which had two pins, like this one:



Which I used to adjust the BB in my old frame. That will not work on my new BB, but I would like to get one that will in order to avoid messing around with screwdrivers, Allen keys etc.

Thank you for your input. Is your IGH reliable?

I think I will answer the reliability question with some pictures. Put it this way - I think you got the best deal with the chain model vandjq !!! (to be fair the hub gear itself has been fine for me - and is working well now - its just the rear sprocket and belt that went )

(Ironically I originally ordered the chain version of the bike but Tredz ran out of bikes after taking the order .. this was complicated by the fact it was on the cycle to work scheme .. long story.. but I ended up with the 2018 belt drive model by default. Putting the belt issue (which now appears to be fixed) aside I am loving the actual bike.. I cycle it daily to work or to the station if I am working in London and its great in the winter weather. I have added a mudflap at the front and raised the bars/added bar ends.)

By the way you are right about the ebb tool.. there only seems to be one hole so the two prong tool is not going to work. As discussed above I put a long thin screwdriver in the EBB hole (..er.. and maybe out through the hole at the other side as well .. memory failing now) and yanked it around with that..not elegant and you cant help thinking there must be a better way ...

I could check the "red dot" position on my bike if it helps ? I have not checked it since Berkshire Bikes fixed the belt but the gears have been changing fine..and I use pretty much the whole range daily..