dmone9x

Hi,

I bought a second-hand bike recently (apparently not ridden much, a Ridgeback Comet) but there is an issue with the gears, or at least I think there is, because I haven't ridden a bike since I was a child and am not what normal is.

The issue is, when I change up a gear the pedals will always jerk forwards as the gear changes. I only use the top four gears and this is quite disconcerting when going at speed on a busy road.

I got the rear wheel off the ground and had a look at the bike.

I can see that when I change up a gear, the chain comes off the rear cog until the chain is still hooked on the old gear at the top of the cog, and then drops onto the higher gear, and its then that the pedals jerk forwards.

Appreciate any help for a beginner.

Thanks.

Zef

It is hard to say what could be causing your problem as many factors can cause problems with shifting gears. However, it does sound like your chain/gears may be worn. Here are a couple of recommendations:

1. Measure your chain with an a 12inch ruler...two rivets of the chain should line up with the zero and 12inch marks. If the rivets do not line up then your chain is considered worn and should be replaced.

2. If you have a worn chain and are replacing it, the standard recommendation is to replace the gears at the same time as well.

3. If you do not think this is the problem, buy a repair manual or find some websites and do some reading on tuning your drivetrain, then do some troubleshooting/experimentation to fix the problem.

4. If all else fails or if you don't want to bother with the research then take your bike to a shop and have them evaluate it.

-j

dmone9x

Thanks.

The thing is, I've tried 4, but they seemed a bit clueless (new shop). They said it "seems ok". I would expect them to either say it is fine or it isn't, didn't inspire much confidence.

So it isn't normal then?

Should the upshift be quite smooth in terms of the pedal movement? And not be a banging noise from the chain dropping onto the higher gear?

Yellowbeard

Since you say you're a beginner, are you easing up on the pedals when you shift? It's normal for an upshift (to a smaller cog) to sort of "clunk" into position if you're putting pressure on the pedals, especially if there's a large-ish gap between the two cogs. My 5 speed does it, and so does my 20 speed road bike, within reason.

Do you ride any other bikes for comparison? Next time you ride, try shifting without any pressure on the pedals. If the chain slips into the higher gear smoothly under no pressure then it sounds perfectly normal. The crank shouldn't jerk forward so much that it causes problems, but honestly it sounds like you're just shifting under power and aren't used to the feel of shifting.

dmone9x

Thanks for your help both.

Next time I ride I will see how smooth it is when I pedal lightly as I change.

Are more expensive gear systems better than cheaper ones in this kind of area (smoothness and accuracy of gear changing) or are they pretty similar?

I think ultimately I need to change the gears about a bit anyway, because I only use the top 4 gears. I assume it would be better if the most used gears were in the middle of the range?

FBinNY 

You've exactly described what happens on upshifts. There'll be a bit of slack created in the top loop as the transition zone comes over the top of the cassette and the pedals will slip forward a bit.

Most riders don't notice it because they lighten the pedal load a bit during shifts, and have come to expect it and so tune it out as a normal part of the shift process. Better systems also do this, but to a slightly lesser degree because the transition zone is better managed by means of shift gates and phasing of the sprockets.