Question for bike mechanics

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 Yanis Nayu 11 Dec 2018

My winter bike has got a problem whereby the drive train slips slightly under load on a fairly regular basis. I can hear it and feel it through the pedals. Doesn’t matter what gear I’m in. I’ve had a new chain, cassette and big ring but hasn’t solved it. I wondered if it was the bottom bracket bearing, but that’s not so old I don’t think - maybe done 2000 miles. It seems to me like tension builds and then releases. It’s weird. Anyone got any ideas?

Thanks in advance.

 

 Timmd 11 Dec 2018
In reply to Yanis Nayu:

Since you're replaced the rest of the drive train, the only thing which comes to mind is the freehub which the cassette goes on. 

It strikes me that the bottom bracket probably wouldn't cause that because it's just a 'spinning round thing' as it were.

Post edited at 20:23
OP Yanis Nayu 11 Dec 2018
In reply to Timmd:

Mmm, that’s a thought. 

 elsewhere 11 Dec 2018
In reply to Yanis Nayu:

I know the following makes no sense but...

...give it a bit of time for chain to bed into cassette, although both new it seemed to improve things on my bike.

OP Yanis Nayu 11 Dec 2018
In reply to elsewhere:

I’ve done at least 600 miles on it now, so I don’t think that’s going to happen. 

 balmybaldwin 11 Dec 2018
In reply to Yanis Nayu:

Free hub is worth a look but also:

I would have a very close look at the chain and look for a stiff link (sometimes done by not quite getting the pin in the right position when breaking/joining a new chain) check the movement of each link by hand, you might find one that's not engaging properly on the cassette or the jockey wheels.

Also look at the rear dérailleur and jockey wheels themselves... under load you may be getting movement that is causing the chain to half climb onto the next sprocket, or if bushings are loose allow chain to come off jockey wheel.

Are you certain you have the right width chain on? (i.e. you haven't got an 11 speed chain on a 8 speed cassette or v/v)?

Could also be indexing problems or sluggish (dirty/old/bent) gear cables, but I would presume you've had all that checked if you've changed the ring, chain and cassette already) and you'd probably recognise it at chain climbing/jumping

If you can, mount a go pro looking at the rear end of the chainset when it's happening to help diagnose

 

Post edited at 20:55
 Lord_ash2000 11 Dec 2018
In reply to Yanis Nayu:

Freehub would be my guess based on what you've said. Does it happen more if you really put some power through the pedels? It'll only get worse as time goes on. It basically works like a ratchet with little spring loaded bars which will spin freely one way but lock in against teeth which spun the other way. It's either worn out or possibly the springs which engage the locking mechanism have got clogged up with grime and don't always fully engage.

Post edited at 21:02
 joeruckus 11 Dec 2018
In reply to Timmd:

Might the new chain be too long? Did you take out the right number of links so that it was the same length as the old one?

A chain can stretch even in 500 miles depending on your riding conditions (and the quality of the chain), so it might be worth checking for chain elongation.

Chains can skip like this if there's a stiff link – this can happen with new as well as old chains. Stiff links can be visible by turning the crank slowly – a stiff link won't bend properly and might deflect the jockey wheels when it passes through them (so you might hear the rear derailleur 'flick' occasionally as you cycle along in a gear if that's the case). 

If the rear derailleur is misadjusted or bent it can cause the chain to skip by lining up the chain between gears. Check that it shifts equally in both directions and that the chain can be pedalled backwards without catching. 

A loose jockey wheel on the derailleur can cause the chain to skip by letting it move too far laterally. Similarly, if the derailleur pivots are worn it can get loose enough to move around causing the chain to skip.

 elsewhere 11 Dec 2018
In reply to balmybaldwin:

> I would have a very close look at the chain and look for a stiff link 

this, even on a brand new chain.

> Also look at the rear dérailleur and jockey wheels themselves... 

and this.

Bent gear hanger?

 abr1966 11 Dec 2018
In reply to Yanis Nayu:

My money is on the rear mech based on most other things being replaced and doesn't sound consistent enough for a freehub to me....jockey wheel issues?!....hard to identify from riding and if you put the bike on a stand it won't happen as not under load when you spin the cranks by hand...

Let us know if you get anywhere with a fix!

 Timmd 12 Dec 2018
In reply to abr1966:

I guess the right order to approach things in would be to check the chain first for stiff links, and then make sure the indexing and rear mech are fine, and then check the freehub last. 

In my experience problems with rear mechs seem to amount of resistance happening due to the chain getting caught up somehow, rather than in slippage as such. 

Edit: Unless it's misalignment related slippage I guess, but it being across all gears seems slightly unusual for that.

Post edited at 03:35
In reply to Yanis Nayu:

Probably of no help being as you mentioned a new chain but mine did this when the chain had a twist in it.  

This was on my 8 week old bike it was fixed at its first service . Think I'd got it caught and twisted slightly after the chain had come off and jammed.  

 

OP Yanis Nayu 12 Dec 2018
In reply to Yanis Nayu:

Thanks to everyone for the replies. I’ll check what I can. I don’t think it’ll be the chain because fitting the new one didn’t make a difference - it was their before and after. It was done by a bike mechanic and I don’t think it will be the wrong length. Easy thing to check though. 

The other symptom that I forgot to mention is that pedalling backwards is very stiff. Not jumpy, just more resistance than you’d expect. I wonder if that would point to an issue with the jockey wheels?

Thanks again!

 Fruitbat 12 Dec 2018
In reply to Yanis Nayu:

The first thing that came to mind (having worked on a good few bikes) when you described this symptom is a new chain not matching a worn chainring. You say the big chainring was changed - is the slippage occuring when you are in the big ring or just when in the middle and inner (assuming 3 rings).

It seems as if you had this problem before the work was done as you say that changing the parts 'hasn't solved it'. Did someone else do the work and, if so, why did they say why they only changed the big ring (same question to you if it was you that did it).

It's often the middle ring that's worn as many people use that the most, sometimes to the extent of never using other rings. Maybe you only use the outer ring so that's why it was changed, in which case I can only suggest, as others have, that a stiff link is worth looking for.

Edit: seen you posted as I was writing this and have answered some of my q's. Would suggest taking it back to the mechanic if you are not happy. Don't know about pedalling backwards being stiff is this with you sitting on the bike (i.e. pedalling with your feet) or just spinning the cranks backwards by hand?

One of those cases in which it would be better to see the bike; hard to diagnose on a forum but keep us all informed of what happens.

 

Post edited at 08:12
In reply to Yanis Nayu:

I would go for the free hub, not expensive and relatively easy to change out.

 Timmd 12 Dec 2018
In reply to Yanis Nayu:

> The other symptom that I forgot to mention is that pedalling backwards is very stiff. Not jumpy, just more resistance than you’d expect. I wonder if that would point to an issue with the jockey wheels?

> Thanks again!

You could split the chain at the quick link and remove it to see how freely the jockey wheels turn pretty easily, but if it was jockey wheel related I'd expect there to be resistance in both directions.  

I guess since freehubs wear out eventually, buying a new one and replacing it if you can do that would either solve the problem or rule that out as the cause, and you'd have it to hand (or your old one) for when the time comes to swap them again due to wear. 

 

Post edited at 17:46
 krikoman 12 Dec 2018
In reply to Yanis Nayu:

Can you tell whether it's slipping at the front or the rear?

OP Yanis Nayu 12 Dec 2018
In reply to Yanis Nayu:

I had a look earlier - the chain seemed fine, but there’s a lot of lateral play in the jockey wheels. I checked my race bike and they’re rock solid. I can’t help thinking this could cause issues with the chain line. 

 Timmd 12 Dec 2018
In reply to Yanis Nayu:

Some mechs do have lateral play apparently in the jockey wheels apparently, but it might not apply to your's. You could be right hopefully.

Post edited at 19:08
OP Yanis Nayu 12 Dec 2018
In reply to Timmd:

I’ve tightened one - the Allen bolt was loose.  Didn’t seem to be able to tighten the other much but the play has reduced. See what happens tomorrow night! I might just buy some new ones - seem simple to replace and the teeth are probably worn anyway.

Thanks again everyone. 

 

OP Yanis Nayu 13 Dec 2018
In reply to Yanis Nayu:

Didn’t work. Will investigate the free hub next. 

 webbo 13 Dec 2018
In reply to Yanis Nayu:

Have you got another back wheel. If so swop the cassette on to that and see if you still have the problem. If not it’s the freewheel.

 

Post edited at 19:50
OP Yanis Nayu 13 Dec 2018
In reply to webbo:

I have, but they’re carbon and have no tyres, so I’d need to swap the tyres and the brake pads, so not a 5 min job. Needs must though...

 webbo 13 Dec 2018
In reply to Yanis Nayu:

just to test it you are not really going to use the back brake as the best way to test it will be going up hill, not down one.

 

In reply to Yanis Nayu:

Hi, what hub have you got? If it is sticky back-pedalling then it sounds like the free-hub. Many are fairly easy to service. I pulled a Hope hub apart the other day and 2 pawl springs had broken and it was totally gummed up. It works perfectly now. 

OP Yanis Nayu 13 Dec 2018
In reply to blackmountainbiker:

It’s a Mavic Ksyrium wheel - presume it’s their free hub. 

In reply to Yanis Nayu:

The freehand bodies for those are pretty easy and cheap, £30ish I would guess, to get hold of. I think they have little coil springs on the pawns which can break or deform, as can all springs on freehub pawls. It is easy to imagine them not pushing the pawls out quickly enough causing a slip and also them dragging causing a sticky back pedal feeling.

 afx22 14 Dec 2018
In reply to Yanis Nayu:

Lots of good info above but I'd add that chain / cassette compatibility could be an issue.  I've seen people fit an 8 speed chain to a 10 speed cassette.

However it's more likely to be one of the issues already raised.

OP Yanis Nayu 17 Dec 2018
In reply to Yanis Nayu:

Just changed the cassette and tyre onto a carbon wheel. Only went through two tubes getting the bastard tyre on the bastard rim. Took it for a spin - same problem. <insert lying on the floor in the foetal position crying emoji>

 abr1966 17 Dec 2018
In reply to Yanis Nayu:

There is only one solution:

N=+1 

Gone for good 17 Dec 2018
In reply to Yanis Nayu:

Your local bike shop is your friend in circumstances such as these.

If you go to Halfords you will get a discount if you can show membership of British Cycling (via a discount code)! My limited experience of using Halfords has been positive.

 krikoman 17 Dec 2018
In reply to blackmountainbiker:

> The freehand bodies for those are pretty easy and cheap, £30ish I would guess, to get hold of. I think they have little coil springs on the pawns which can break or deform, as can all springs on freehub pawls. It is easy to imagine them not pushing the pawls out quickly enough causing a slip and also them dragging causing a sticky back pedal feeling.


I'd second this, I once filled mine which heavy grease (because it was very noise) it quietened it down massively, but in the cold the grease thickened up and the pawls stopped springing back as quickly as they should, result; slipping.

Cleaned everything out packed with light grease and got the best of both worlds.

OP Yanis Nayu 17 Dec 2018
In reply to abr1966:

> There is only one solution:

> N=+1 

I’m broke. And if I was going for another bike I’d get a TT one. 

OP Yanis Nayu 17 Dec 2018
In reply to Gone for good:

I spent £100 with the LBS on my race bike to solve a creak that’s still there, and I’ve spent £120 on parts and labour to solve this problem with a mobile bike mechanic and I’ve still got the problem. I don’t have a lot of faith...

Gone for good 17 Dec 2018
In reply to Yanis Nayu:

I feel for you. The Velotech bike shop in Stratford is owned by one of the guys in the local cycle club. I vaguely remember you being not too far from Stratford. If so I can recommend their services if you are considering spending more money to solve the problem.  They are very good.

OP Yanis Nayu 17 Dec 2018
In reply to Gone for good:

Ah, I never think of them. I crashed my bike in a race with the guy that owns it (not that it was either of our faults). I think I’ll give them a go. I’ve put the old wheel back on. Bloody fingers are sore!


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