Slipping gears- help please!

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colin54
Posts: 2529
Joined: 24 Sep 2013, 4:34pm

Re: Slipping gears- help please!

Post by colin54 »

Paulatic wrote: 30 Jul 2021, 6:14pm If you don’t know what the original number of links were then loop the chain over the biggest ring and biggest sprocket. Not going through the derailleur and then add two links.
You'l find a nice picture illustrating this in Jdsk's Sheldon Brown link up-thread, which I've often used as a reminder myself. If you also read the section marked 'Cables' towards the end you will read a description in the first paragraph describing the cable issue I described in my first post.
I think if you are changing to a lower gear ( bigger cog against the rear derailleur spring) the force exerted at the gear-lever will pull the cable the correct amount, whereas when changing to a higher gear(smaller cog) the spring in the derailleur itself is pulling the cable, any excessive drag in the cable will cause your symptoms. Here's the link again.
Good Luck

https://sheldonbrown.com/derailer-adjustment.html
Nu-Fogey
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cycleruk
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Joined: 17 Jan 2009, 9:30pm
Location: Lancashire

Re: Slipping gears- help please!

Post by cycleruk »

After Colin54 cable suggestion and with the bike doing so many miles I would think it's possible the freehub pawls are worn or sticking.
A new chain and cassette is very unlikely to slip and as you have replaced the chainwheel as well I would be looking elsewhere for the problem.
Any chance you can try another wheel or borrow one ?
New cable would be the cheapest first then think about the freehub.
You'll never know if you don't try it.
rph112233
Posts: 12
Joined: 30 Jul 2021, 4:35pm

Re: Slipping gears- help please!

Post by rph112233 »

Hi, I just took four links out of the chain, using the biggest cog to biggest cog plus 3 links method, and I'm afraid the problem is exactly the same. Should have mentioned previously, all cables inner and outer, are relatively new and feel like they are smooth and operating correctly.

Frankly, I have had enough of this damn bike and have reached the end of my patience with it.

I'll take the cassette off again and have a look at the freehub when I have calmed down a bit, which could be never I am so damn sick of this bike.

Thanks for all your help.
Jdsk
Posts: 24636
Joined: 5 Mar 2019, 5:42pm

Re: Slipping gears- help please!

Post by Jdsk »

Do you want someone else to have a look?

Where are you?

Jonathan
rph112233
Posts: 12
Joined: 30 Jul 2021, 4:35pm

Re: Slipping gears- help please!

Post by rph112233 »

Hi, I'm in east London, but I'm afraid I am broke now. The pandemic destroyed my business and buying all the parts has wiped me out for the foreseeable future. Thanks.
rph112233
Posts: 12
Joined: 30 Jul 2021, 4:35pm

Re: Slipping gears- help please!

Post by rph112233 »

I just took the bike to see Lawrence at Probike in Hackney Wick who rebuilt my rear wheel last year using the govt. £50 voucher scheme, and he reckons the derailleur hanger is bent.

I replaced this just a year ago, but I guess it's possible it has taken a knock since then. I took it off and reseated it a couple of times recently, but with no improvements, so I'll get a new one and see how it goes.

Thanks for all your help.
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cycleruk
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Joined: 17 Jan 2009, 9:30pm
Location: Lancashire

Re: Slipping gears- help please!

Post by cycleruk »

You could try a DIY on the hanger. I have done it before just using an adjustable spanner adjusted to fit the thickness.
If it's an alloy hanger then there is a chance it will possibly break so go easy.
The hanger should be set so that the derailleur is vertical when viewed from the rear and inline horizontaly when viewed from above
Various Utube vid's showing how-to :-
https://www.youtube.com/results?search_ ... ier+hanger
You'll never know if you don't try it.
rph112233
Posts: 12
Joined: 30 Jul 2021, 4:35pm

Re: Slipping gears- help please!

Post by rph112233 »

Thanks, I just cycled down to Decathlon and bought a new hanger and fitted it outside the store, during torrential rain.

Cycled back, still skips, from 5th gear and up, though possibly less, the jury is still out. I will set the derailleur up again before concluding whether the problem is solved or not as it is now running very roughly.

At this rate, I'll end up getting a new bike only to find it has the exact same problem!
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fausto99
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Joined: 19 Sep 2011, 10:06am
Location: NW Kent

Re: Slipping gears- help please!

Post by fausto99 »

rph112233 wrote: 31 Jul 2021, 1:38pm I just took the bike to ... Probike in Hackney Wick ... and he reckons the derailleur hanger is bent.
You can bend the old one back. If it's aluminium it will break eventually but if it's steel you can bend and re-bend many times until you get it right.

Cross posted - if a new hanger still doesn't work it's the frame that's bent. Same difference - you can bend the frame/hanger combo using the alignment procedure in the YT link in the cycleruk post above
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fausto99
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Joined: 19 Sep 2011, 10:06am
Location: NW Kent

Re: Slipping gears- help please!

Post by fausto99 »

rph112233 wrote: 31 Jul 2021, 3:54pm Thanks, I just cycled down to Decathlon and bought a new hanger and fitted it outside the store, during torrential rain...At this rate, I'll end up getting a new bike only to find it has the exact same problem!
"the trouble with Fred is, he's too 'aisty, an' you never gets nowhere if you're too 'aisty" Bernard Cribbins - "Right Said Fred" :lol: :lol: :lol:
Megasaur123
Posts: 3
Joined: 5 Aug 2021, 12:11pm

Re: Slipping gears- help please!

Post by Megasaur123 »

:shock: OK, check frame alignment, rear hangar, need to see bike in the flesh. Freehub body has two bearings, 6803. If they are shot, freehub body will flex significantly. If bearing seat close to wheel bearings in freehub body is pitted, you can't replace the bearing as 6803 bearing will not pass through seat. You need to check frame alignment, rear hanger, have you adjusted L,H screws correctly.
I can't tell you what is wrong without looking at the bike.
Are you using correct shifters with rear mech?

:shock:
rph112233
Posts: 12
Joined: 30 Jul 2021, 4:35pm

Re: Slipping gears- help please!

Post by rph112233 »

Ok, maybe a silly question, but not something that has been covered yet.

Sorry for my absence, I had to walk away (literally) from my bike as it was dong my head, as well as my wallet, in.

When fitting the new chainwheel, I noticed that it would rub tightly up against the frame. Which got me thinking about the bottom bracket.

Is it possible that the bottom bracket width is too narrow? The BB seems to extend further on the non-drive side than it does on the drive side too.

I struggled to get the bottom bracket out on the drive side, but shifted it outwards by a mm or so, where it remains. However, this did allow me to fit the new chainwheel, albeit with the same slipping issues.

If a bottom bracket was fitted that was too narrow, that would seem to be a potentially obvious cause of gears slipping on the smaller rear cogs? The chainset would be Xmm to the left, causing issues on the smaller rear cogs? The BB was replaced by a bike shop some time ago.

Does this make any sense? I know how to measure the bike for the cartridge size for the BB, but what about the width for a replacement, how do I measure that, if the old BB is too short?
esasjl
Posts: 55
Joined: 18 Feb 2021, 9:02pm

Re: Slipping gears- help please!

Post by esasjl »

This is likely a daft response, but are the chain and cassette matched, e.g., both 8-speed? If the chain is too narrow it may slip, especially on small sprockets?
slowster
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Joined: 7 Jul 2017, 10:37am

Re: Slipping gears- help please!

Post by slowster »

By 'chainwheel' I presume you actually mean a complete chainset (cranks with chainrings fitted). What width bottom bracket is needed should be in the product specification for the chainset, e.g. on the manufacturer's website.
rph112233 wrote: 8 Aug 2021, 12:42pm I struggled to get the bottom bracket out on the drive side, but shifted it outwards by a mm or so, where it remains. However, this did allow me to fit the new chainwheel, albeit with the same slipping issues.
It is not clear to me what you have done or how, but it does not sound good. Cartridge bottom brackets are generally not designed to be 'adjusted' like that (there are a few exceptions, but they are expensive, very uncommon and very unlikely to have been fitted to your bike).

If you are able to post photographs of your bike and the relevant parts, with side on and overhead shots, people will probably be better able to advise you.
rph112233
Posts: 12
Joined: 30 Jul 2021, 4:35pm

Re: Slipping gears- help please!

Post by rph112233 »

UPDATE: Problem solved

My last train of thought on the slipping gears problem turned out to be correct.

A few years ago when I was using the bike for commuting the bottom bracket broke so I took it to a bike shop to get it fixed quickly.

Unaware to me at the time, the bottom bracket they fitted was too narrow, aligning the front crank chain line too far to the left, making it skip on the smaller rear cogs.

Putting a new chain on it earlier this summer exacerbated the problem by removing the tolerances of worn equipment that allowed it to work, albeit not perfectly, previously. This was followed by a new cassette, new rear derailleur, derailleur hanger and front chainring. These all made the problem worse than ever.

When fitting the new chainring, I noticed that the bottom bracket was very narrow and the chainring was right up against the frame, so after bodging it to work for a bit so I could get about, I bought the correct width bottom bracket as dictated by the chainring specs.

After an absolute nightmare getting the old bottom bracket off, which completely mangled the awful bb tool I bought from Halfords (for which they gave me a full refund), I fitted the new 122.5mm bb, put on a new derailleur cable, and after a bit of tweaking to set it up, I am pleased to report that after a ten mile ride, it all seems to be working well.

Anyway, I think the moral of this story is be careful listening to advice from bike shops. Not only did a bike shop cause all the hassle in the first place by fitting the wrong part, they then needlessly advised me to replace the chainring. I won't name the bike shop as I know it has changed owners since I had the BB fitted by them.

Thanks for all you help, sorry for the long rambling finale but I figured I should update you!

Now, if I can get the hole in my kayak repaired, I finally have a chance to get out and enjoy the summer!
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