Had a slightly scary problem on the way to work this morning. Riding along happy as Larry when my bike suddenly slipped gears. It continued to do this all the way to work randomly changing gear. Any clues as to where to start looking for possible causes?
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gears slipping?
(16 posts)- Started 11 years ago by Zenfrozt
- Latest reply from Zenfrozt
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Posted 11 years ago #
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Dérailleur rather than hub presumably?
Slipping in more than one gear?
Under pressure?
Posted 11 years ago # -
It worries me that I actually have two things to suggest (1) is your chain stretched? (2) there's a little screw that you can tweak (Chdot showed me how) that adjusts the gears.
I have even helped someone else with this. Her problem was reverse of yours - she'd bought a cheap bike and it wouldn't change gears. With my handy multitool I was able to sort it. Quite empowering really (haven't to,d you'll about it before because I thought you'd be terrified by idea of me offering anyone advice -much less help- with bike mechanics.)
Posted 11 years ago # -
"thought you'd be terrified by idea of me offering anyone advice"
A little knowledge is a dangerous thing...
" (2) there's a little screw that you can tweak (Chdot showed me how) that adjusts the gears."
The little screw(s) stops the rear mech going into the spokes (or having the chain stuck between top gear and the frame).
Or do you mean the knurled knob where the outer cable meets the mech?
Posted 11 years ago # -
I dont know, but it made the gears work.
I'll let you sort zenfrozt!
Posted 11 years ago # -
[written by lionfish! - forgot it was still logged in as minimoth]
I'm probably as SRD's level of bike-fixing-skill.
Yeah, I must say I still find it's trial-and-error adjusting stuff, but it seems to me that the best thing to mess with is the knob on the cable. I've found I've only had to mess with the limiting screws when getting new cogs*/chain.
Zen: If it happens more when you apply pressure (the most fun is when starting at a junction and you put loads of pressure on the pedal for it to give way below you) then it's probably the chain's stretched and cog-teeth are worn. I was told the easiest way to see if a chain's stretched is if you can lift some slack around the cogs (you can also measure them - no idea how to do that). The teeth show up worn if they become a bit 'shark-fin' like (so one side is sloped more than the other on each side of each tooth - if that makes sense?). I'm sure someone on here can translate that into bike-speak, but that's the non-expert's thoughts :)
*what are they called? A "set"? mech?..?
Posted 11 years ago # -
Almost certainly the case that you need your chain renewed.
A bike shop will recommend that you change the rear cassette as well. This may not be necessary if you are prepared to put up with another week of gear slip till the new chain settles in. But it's probably worth it.
Posted 11 years ago # -
"*what are they called"
Depends who you ask.
Block is common name for a cluster that screws on, cassette for one that pushes on to a freehub.
Cogset isn't a word I'd use, but this explains it all
Posted 11 years ago # -
I think it's the gears at the back.I haven't seen the front gears change without me telling them to.
My chain could maybe use some lubrication but this felt like a bigger issue.Posted 11 years ago # -
Bit of oil might be a good idea.
Stops the squeaks and reduces wear.
May be too late - chain might need replacing.
BUT a few clicks of turning (probably anti-clockwise) of the knurled knob may sort the unwanted gear change problem.
Follow cable all the way from gear changer to mech.
Some changer also have a knurled bit so you can adjust the cable while you are riding.
Posted 11 years ago # -
Ok so partially successful. Fiddling with the derailer I've managed to solve the random gear change problem but no amount of my faffing appears to be able to get the bike down into 1St gear. I'm stuck starting in second.
Posted 11 years ago # -
Better than not.
If you have someone to help you, get them to hold back wheel off ground (lift by saddle or rack).
Move lever to lowest gear, turn pedals, then gently push rear mech towards wheel.
If it moves easily and chain goes onto biggest cog (at back) it means you need to turn knurled knob again.
If it doesn't, it's time to unscrew one of the small screws - a quarter of a turn at a time.
The one with L next to it.
Posted 11 years ago # -
I've just ended up replacing the derailleur, cassette, chain and gear cable on my tourer that has seen a whole winter of commuting. Same problem. I worked my way from cheapest (cable) to most expensive (cassette and chain) to solve the same problem.
A combination of chain stretch, cog wear and gumming up / spring losing tension on the derailleur. Each of these components has been on the bike for 5-6 years so I think they've done their time. Feels like a new bike.
Posted 11 years ago # -
Have you tried a local bike shop? Or get someone with a chain wear indicator, around a fiver.
I have two commuter bikes (Dawes Galaxy & Cotic >X<, for winter and summer commuting) and have ended up replacing the chain and cassette annually. I do ride around 200km a week though! (gosh seems like a lot when I add it up). I have had my Cotic for nearly 2 year now and the slow rear change down is becoming a pain so I think I'll be changing the rear derailleur soon also. I don't bother with top of the range stuff, just a Shimano 9 speed chain £10 and a Shimano HG 50 9 speed cassette £15.
Posted 11 years ago # -
I've had chains last less than 500km (mountain bike, constantly abused, battered and covered in mud) to well over 3000km (town bike, full mudguards, very well maintained) so there's definitely an incentive there to keep on top of cleaning and lubrication. The clip on chain cleaners like this get plenty of hate from some people, but I find them a godsend given just how regularly I clean/lube my drivetrains:
No, it won't be as good as taking the chain off and doing it 'properly' but it is much better than letting crud build up on there. For the most thorough clean, I would suggest first placing your tongue in your cheek, and then following the venerable advice of the great Sheldon Brown: http://sheldonbrown.com/chainclean.html
I have also come to the conclusion that 8 speed is superior to 9 for commuting. 8 speed chains and sprockets are notably wider than 9 speed and this translates directly into better lifespan and I really don't miss that one gear.
As DaveC says, just get the low end Shimano or SRAM chains and cassettes. I've gotten thousands of km out of bottom-of-the-barrel freewheels so there's not much point in spending £50 on a cassette when a £10 one lasts the same time.
Posted 11 years ago # -
Problems solved. Thanks to fellow marshals at pop for their aid.
Posted 11 years ago #
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