Chain falling off hub geared bicycle

[tali42]

Hi,

I have an 8 month old Giant N7 Expression which I use for a 2 mile each way commute and occasional longer country rides. The bike came fitted with Shimano Inter-7 rear hub gears.

Within the last month I have had increasing problems with the chain bouncing off the rear sprocket (and more recently the front chainring). Latest instance occured while riding through a level crossing. There is significant slack in the chain, it would move up or down about 3-5cm if you push at it with a finger.

All the info I've found on the Net says you need "horizontal dropouts" for hub gears due to the issue of chain slack, but the bicycle has dropouts angled about 30 degrees forward of the virtical. The Shimano gear/brake manual gives no indication of how to fix this. The generic Giant manual is useless, it actually says that you should take the bike back to the dealer to remove the rear wheel on hub geared bicycles or risk serious mechanical failure (haven't they heard of punctures?).

I've asked at Halfords and a couple of local bike shops, but they seemed bent on selling me a new chain (it is only 8 months old and I would expect chains to last longer on hub gears, compared to derailleurs). If anyone is familiar with how I can take the slack out of the chain on the GIant Expression N7, please tell me. My bike maintenance skills don't go much byound puncture repair! Taking it back to the shop I baught it from would be difficult because I've moved further away.

[rogerzilla]

The dropouts do have sufficient adjustment to remove chain slack. They're angled so that the brake shouldn't need adjusting if rim brakes are fitted.

If loosening the axle nuts and pulling the axle back doesn't work (because you run out of slot), first remove the chain and measure 24 links when the chain is hanging down freely. More than 12 1/16" and you should fit a new chain and tension that. Assuming the chain is OK, it may have been too slack to begin with, in which case you'll have to remove two links (which is actually one full link) to shorten it. This is unlikely.

Note that, unlike fixed gear bikes, the chain shouldn't be drum-tight on a hub-geared bike. There is less risk of an accident when it comes off (on a fixie it can literally twist the rear triangle through 90 degrees if it gets wrapped around the crank) and an over-tight chain can pull hard enough on the sprocket to interfere with gear selection and smooth running.

[thirdcrank]

tali42

Just to expand on what rogerzilla says, there are something like 7 or 8 versions of the Inter-7 hub and as far as I can see, all come with a built in brake (coaster AKA back-pedal or roller - contolled with a lever and cable.) The point being that as well as undoing the wheelnuts to tension the chain, you also have to slacken off the fixing of the brake's reaction arm - the piece of metal which projects forward from the hub and is fastened to the frame with a clip.

The Shimano techdocs site has some instructions:

http://techdocs.shimano.com/techdocs/index.jsp

Click on comfort bike, then Nexus, then look for your hub model. You need the relevant 'si' (= service instructions.) In fact, if you don't know exactly which numbered version of the hub you have, so long as you go for the right number of gears and the correct type of brake, I think any will do. I appreciate you have psoted that the Shimano manual is no help but the techdocs look clear to me. They are written for somebody installing the hub, so you have to work backwards through the instructions to loosen ii and then re-tighten it with once you have pushed the hub backwards in its slots, as explained by rogerzilla. When you are re-tightening, make sure that the wheel is centred in the frame so that there is a similar clearance on either side of the tyre. Then tighten the wheel nuts, making sure that tightening them does not disturb your alignment of the wheel. Finally, re-tighten the fastening of the reaction arm

I'm not clear if you have actually had the bike examined by somebody in a bike shop, because if they have seen it and are advising a new chain, they may be right.

[rogerzilla]

Good point about the hub brake - we have a bike with a Nexus 8-speed and roller brakes, and this has the annoying reaction arm.

Incidentally, chains on hub-geared bikes don't necessarily last longer than on a derailleur bike that's used properly (i.e. not cross-chained all the time). It's the sprocket and chainring that last longer, because (assuming 1/8" chain) they're much thicker to start with and don't need any special cutouts, reduced teeth or ramps.

[tali42]

I thought I'd update on my difficulties in getting this sorted. I expect the advice about moving the reaction arm is correct, but lacking the tools and confidence to adjust this, I took the bike to the LBS for a service with a request to look at the chain dropping issue. All seemed well, until about 30 hours after I got it back from the shop I went to use the back brake and the back wheel locked up completely while the front wheel ended up 90+ degrees to the frame. After I'd gotten over the surprise I did a roadside inspection and found that the reaction arm had come off the frame, the nut and bolt that held it in place were nowhere to be seen. SInce I hadn't touched this stuff since I got it back, I can only assume that the LBS mechanic simply didn't replace the nut, or only finger tightened it, and that the bolt simply rattled loose over the next 30 hours.

Here is a picture of the mess after I'd dragged it home...

Mess after the reaction arm comes loose. :(

The picture doesn't show that the force ripped the cable out of the cable guides on the down tube, ripped the barrel adjuster out of the brake lever, snapped the mounting of the Bazil basket on the front (the front brake cable looped over the mount).

I took it back to the LBS who had it back the next day, but with a wheel that had about 2cm of rattle, a rear brake that didn't quite have the same efficacy it had before and the gear cable still hanging loose due to the broken cable guides. The shop guy said the "cones" had been damaged in some way and that parts had been ordered. 2+ months later I still have a wobbly back wheel and everything else (after one false alarm when the parts turned out to be the wrong ones). And this weekend I've got a flat and couldn't get the wheel out of the frame. The axle on the drum brake side simply wouldn't budge from the dropout, I double checked I'd undone everything (I never had this problem before).

Should I be demanding that the cycle be returned to me as it was before the error, or should I just accept that I'm the victim of an honest mistake and take what I can get? A week of bus commuting should have me in the mood to stamp my foot and demand to speak with the manager. I've been very polite and submissive so far, believing that to do anything else would simply result in the LBS washing their hands of me (I didn't get a receipt for the service, and anyway, they could just say that I must have done something to the bike in the intervening 30hours).

Does anyone know if the little platic cable guides would be the sort of thing a bike shop can get replacements for?

I'd really hoped to post that I got it sorted, but this will have to do for now.

[rogerzilla]

They have to put it right.

[tali42]

Well, it seems that the mechanics at this LBS (Mitchells Cycles, Gloucester) are just incompetent and tricky. It has taken two trips back since then to get it ridable. First time the gears would not shift properly so I had to come back again later (they should have checked the gears were working while they had it in the workshop). He actually asked me to bring the Shimano manual in, thanks to previous posts on this thread, I pointed out that these were available on the Shimano website. Second time, the gears were still a bit off (although the shop bloke would have none of this), but I fiddled with the barrel adjuster and kept riding.

On the weekend, I was going to go for a bit of a ride in the countryside, but decided that I'd better check that the back wheel would actually come off now. It still refused to budge.

So I phoned them up this afternoon to raise this. I was told that the problem was that they'd used an extra nut to hold the drum brake together, and that to get the rear wheel off I'd need to use a screw driver to wedge the frame apart and pull it out. I already have to carry 3 spanners and a 2mm hex rench to get the back wheel out on longer rides, so I suggested that this wasn't a good enough repair, and that the drum brake should be replaced since they'd caused the original issue. He complained that they couldn't do that because they're not a Giant dealer (never mind that the drum brake is Shimano, and I'm sure pretty much any bicycle shop in the developed world can get Shimano parts?).

Towards the end of the phonecall, he was basically denying they'd done anything wrong, and claiming they'd already done me a favour by "fixing" it already and that it was all because the bicycle was badly designed (he might have a point there). Best offer was to return the original money I paid to have it serviced.

And, for the icing on the cake, this evening the chain fell off on the way home from work, leaving me to push the damn thing 3 miles home.

Perhaps I'll have better luck with the next place I take it to, although I shudder to think what the final bill will be. Stagecoach are going to be a few pounds richer, that is for sure.

[MartinC]

This must be really frustrating. I think you've got 3 alternatives:

1. Keep on at Mitchells to fix the problem they've created. May take ages - doesn't sound like they're too competent with the technology.

2. Find another bike shop to fix your problem. Cheltenham may be more productive - phone Cheltenham Cycles, Williams or Roylans. May not work out though - hub gears seem to be a mystery to many shops.

3. Spend the time on the internet and in the shed to find out how to do it yourself. Roller brakes on Shimano hubs are easy to replace if you need to - there should be no need for an 'extra nut'.

I'd suggest 3. Dig out the diagrams and service instructions on the net and have a go. There are many on this forum who have a good grasp of hub gears and will answer questions for you. If you have to get parts then get the part numbers from the net and order them from the LBS. They should have the Madison (Shimano importers in the UK) catalogue and can order from this.

Hope you're sorted soon.

[tali42]

Well, I took it to Roylans in Cheltenham, where I got it from originally (used the train to get it there).

They took one look at the back end and said it was all put together wrong. Sadly, they later told me that the rear dropouts were so mangled that even if they order a new back wheel from GIant (£150) it was doubtful that the rear wheel would stay positioned properly. They said that to get an Aluminium welder to fix the dropouts would cost more than a new bicycle.

I really want to get back in the saddle ASAP, so I bit the bullet and ordered the exact same model from Roylans. The list price is now £475 (I paid £395 less than a year ago), but they sold it to me for £400. The current one seems to have effectively been reduced to little more than scrap metal.

I don't know what I'm going to do about this, but obviously, I'm extremely unhappy. Guess its now more of a fair trading issue than a technical issue, but I think I'll take some pictures when I go to collect the broken one on Saturday and post them here anyway.

It is all just such a stupid waste!

[Nigel]

Take some legal advice, if you are a CTC member, perhaps the helplines would be useful. Otherwise, the local trading standards office might give you some assistance.

From what you've reported, I think you've a claim for damages (cost of new bicycle and some consequentials such as bus fares, refund of their repair charges, etc.) against the shop which buttocked up the repairs. They could have refused to touch the bike because they didn't know what they were doing with that type of mechanism. Instead, from your reports here, they mangled the first repair,that then caused an accident which inflicted some more damage to the rear of bike, then mangled things a bit more in a subsequent repair.

Take lots of photographs and ask Roylans for a written description of the damage and faults on the old one.

Hub gears should be reliable and hassle free if correctly looked after.

- Nigel

[tali42]

Well, I said I'd take some pictures, so here they are. I think the hole in the dropout was probably done during the initial inscident, and I was doomed from the moment they didn't attach the brake arm properly. Mitchels never mentioned this damage to me, and the first I knew of it (being unable to remove the wheel myself) was when Roylans told me. The dropout is also betn outwards, but this does show to well in the pictures. It seems reasonable that it isn't possible to get a wheel to sit properly with this sort of damage. Apparently the hub and brake are all put together wrong, but it isn't obvious to me.