Jumpy gears with friction changers

[Andrew_Culture]

I've had jumpy gears plenty of times before with indexed gears and always managed to fettle them until they stopped jumping, but I've now got jumpy gears on my tourer, and that has friction changers!

I never use the small cog at the front and the only cogs I use on the rear cassette are the smallest four (usually just the smallest two). The gears seem to grind and jump when under pressure, like when I'm struggling up a hill, which is a horrible time to have ones gears jump! At first I put this down to me needing practice with friction changers, but I've had the bike well over a year now and the problem appears to be getting worse.

I clean and oil the chain and cogs at least once a fortnight (more when there has been a lot of rain). As far as I can tell the chain doesn't appear to be worn.

Buh? Gah? Dah? Duh?

 

[PpPete]

Sticky cables would be my bet.

 

[Andrew_Culture]

I hadn't even thought of that! I shall now research how to get some lube into my cables.

 

[Scilly Suffolk]

Do you mean the chain jumps out of gear or slips, but stays in gear? If the former, then I'd go with cables, if the latter then I'd think chain/cassette wear.

How are you measuring the chain wear? What do the teeth on your sprockets and chain rings look like?

Being as you use so few gears and this happens under stress, is another reason to think this is due to wear: the smaller the sprocket, the greater the wear (fewer teeth to share work).

You should look at your gearing and fit a cassette and chain rings that enable you to do most of your cycling in the middle range: it will be kinder on both your drivetrain and your knees.

 

[sidevalve]

If you mean slippng on the cogs then yes it's chain / sprocket wear. I f you mean slipping back into [or trying to] another gear I would suggest the friction on the shifters needs adjusting. Sounds like the whole change system would benefit from a good strip / clean / cable lube and adjust up. Easy enough, just take a bit of time to get it right.

 

[Globalti]

Invest in a simple chain wear checker like this:

Check the chain and replace if it's worn, along with cassette and front sprockets if the teeth are hooked.

Then buy a decent quality cable cutter like this:

Buy some gear cable outer and two new inners and treat your bike to a new set, you will be amazed at the deterioration that you have come to accept as normal.

 

[I like Skol]

I remember down tube friction shifters from my yoof! They were far less sensitive to cable problems and I seem to remember getting every change spot on, just a tap, tap, tap on the shifter to change through the gears a I raced away from the lights. I would be surprised if this is a cable problem, from the OP's description sounds like the smallest sprockets are hammered and in need of replacement. As has been suggested already, now might be a good time to look at gear ratios and choose a cassette and front chain ring more suited to the riders style. Doing most of your riding in just 2 gears isn't right unless you live somewhere very flat and don't stop/start much.

 

[deptfordmarmoset]

Could a slightly twisted dérailleur hanger be causing the dérailleur to buckle slightly under stress? (Just putting in this possibility to see what more mechanical-minded cyclists think.)

 

[I like Skol]

Could a slightly twisted dérailleur hanger be causing the dérailleur to buckle slightly under stress? (Just putting in this possibility to see what more mechanical-minded cyclists think.)

The derailleur is not under stress at any time, even when cranking hard up a hill. The derailleur side of the transmission is not under tension except for the spring action of the derailleur itself which remains constant.

 

[deptfordmarmoset]

The derailleur is not under stress at any time, even when cranking hard up a hill. The derailleur side of the transmission is not under tension except for the spring action of the derailleur itself which remains constant.

Hmm, good point. Oh well, at least that's one possibility to discount.

 

[Andrew_Culture]

Wow, loads of responses!

The chain appears to be jumping (or grinding) off the cogs and then almost always changes gear, usually up. After changing gear there is no 'tck tck tck' sound that would indicate that the friction shifter needs to be adjusted to ensure the chain is perfectly on the cog.

I've been checking the chain for wear visually, so will invest in a chain-wear checker when I can afford to.

The bike is quite old and was bought in 'reconditioned' state from my local bike doctor, and I 'think' he replaced the cables as a part of the general tidying up he did. I'll go and try and take some photos of the rear mech.

 

[Andrew_Culture]

I'm not sure if these photos help or not! The bike has had a bit of a soaking this week so is due a very deep clean this weekend.

 

[tyred]

Have a good look at where the cables pass over (or under, depending on the design) the bottom bracket.

What sometimes happens is that frame flex combined with sticky cables at this point can cause the un-intentional upshifts.

 

[Pauluk]

Andrew, there is a good video on youtube (not got time to search just yet) that shows you how to lube your cables without disconnecting them. Goes something like select a gear, then change gear with the selector but don't move the pedals. Cable goes slack and you can then remove the outers from the fixings and slide the outers all the way along the cable. Then just put lube on your fingers and run it along the cable. refit the outers in position and change the gear selector back and the cable re-tensions.

I tried this and it works really well on my indexed gears.

edited:

View: http://www.youtube.com/watch?v=2q1iecATY1o&feature=related

 

[HovR]

I had this problem a while back. The frequency of the jumping lessened severely when I lubed and cleaned out the cables, and the issue completely disappeared when I changed the cables and rear derailleur for new ones.