Gears slipping

kirving

Whenever I'm in a gear ratio where both the front and back are smaller cogs, and I put strong pressure on the pedals to accelerate, the chain just intermittently slips on the back cogs. When I'm in a gear ratio where the front and rear are on large cogs, this doesn't happen.

Something needs to be replaced, but I'm not sure if the problem is with the rear derailur spring being worn out, or the gears themselves being worn. I could leave it in to be repaired, although I'd actually rather replace the rear derailur myself if that was the problem.


Anybody have a similar experience, and what was the solution? Or the most common cause of such a problem?

Mucco

In theory, you're not supposed to use the small front and back at the same time, though in practice, it's only using the big front and back at the same time that's damaging.

This sounds like the chain and cassette are worn out. Change the chain, and see if it still slips, if so, change the cassette.

M

Fabio

I'd change botht he chain and the cassette if I were you. At least then yo'd be guaranteed no slippage from either.

uberwolf

in general, if you've left the chain so long that you're experiencing slipping, you will need to replace both chain and cogs.

Frequent replacement of chain will prolong cog lifetime.

kirving

Fair enough, new cogs and cassette so.....Should set me back about 70 euro....:rolleyes:

uberwolf

you mightn't need the front cogs replaced, but don't forget your chain!

cunnins4

I posted the same thing about 6 months ago and replaced chain, cassette and rear mech. Didn't really fix the small & small skipping thing. Then I bought a full Ultegra road bike and there was a notice attached to the derailler stating not to use that configuration of gears as it puts strain on the chain. If you use your middle ring up front and a middle cog at the back you'll get a similar gearing but keep the chain straight and it shouldn't skip. Also, adjusting the tension on the cable (using the little screw on the derailler cable at the rear of the mechanism) helped fine tune any other skipping cogs. Hope that helps.

uberwolf

cunnins4 wrote: »

I posted the same thing about 6 months ago and replaced chain, cassette and rear mech. Didn't really fix the small & small skipping thing. Then I bought a full Ultegra road bike and there was a notice attached to the derailler stating not to use that configuration of gears as it puts strain on the chain. If you use your middle ring up front and a middle cog at the back you'll get a similar gearing but keep the chain straight and it shouldn't skip. Also, adjusting the tension on the cable (using the little screw on the derailler cable at the rear of the mechanism) helped fine tune any other skipping cogs. Hope that helps.

OP this advice is option 1, to be followed before reaching into your wallet!

doozerie

There are a few possibilities here, some of which are already covered by previous posts:

1. Your chain is too long (i.e. too many links) and therefore too slack which might leave it prone to slipping. This is usually very obvious though as the chain will sag when there is no pressure on the pedal. The fix is to remove a few links. Probably not likely to be this though as you'd probably have noticed the chain sag earlier.
Unfortunately, you can get the same problem when the chain is severely worn and then the only fix is to replace the chain (and possibly the cogs too).

2. The spring on the mechanism holding the jockey wheels on the rear mech might be worn. Similiar effect to above, but again doesn't always result in slipping gears. With some rear mechs you can open up the body to adjust the spring tension, with others you just have to replace it. I would say the likelihood of this being the problem is small, typically.

3. The chain and/or cogs are badly worn. You'll need to replace the chain and typically the rear cogs too (if you just replace the chain, and the rear cogs are very worn, your new chain won't work very well, i.e. it too might slip, and wear on it will be accelerated). Perhaps your front chainring(s) is also worn and may need to be replaced but they should wear out far more slowly than the rear cogs.

The simplest way to figure out if things are worn is:

Chain: You can get a specific (simple) tool to measure the distance between a pair of links to see if the distance is now too great (i.e. the chain is worn beyond safe use). Alternatively a measuring tape will tell you the distance but you'd then need to know what the maximum value is (which you might be able to find out via a web search, for example). Otherwise, with the chain around your least worn front chainring, use your fingers to push the chain "into" the chainring grooves at 12 o'clock and 6 o'clock positions (both at the same time) on the chainring - the chain will push out from the front of the chainring leaving a gap. The size of the gap is a measure of how worn the chain is. You'll need to have an idea what size the gap would be for a new chain in order to make a meaningful judgement here.

Rear cogs: Look at the profile of the teeth. Compare the most used ring with the least used ring to get a measure of how worn the worst of the cogs are. Worn cogs tend to develop sharp teeth with shallow dips between the teeth, which leads to the chain slipping.

Chainwheels: Same method as for rear cogs.

CountryWise

Had the same problem a month ago, got the chain replaced.

However the new chain didnt take to the slightly worn cassette too well so it was a new casette too.

Chain and Cassette fitted €55

kirving

Thanks for that doozerie, I'll have a look at it now. Ive had the bike for almost 5 years, and although I take care of it well, Im guessing that the chain is severly worn at this stage.

doozerie

No problem. There is some useful info here, complete with example photos of wear and indications of what actual measurement indicates a worn chain:

http://www.sheldonbrown.com/chains.html

As a rule of thumb, replace the rear cogs when replacing the chain. If your cogs can be taken apart, then you might get away with replacing only the most worn rings, but except for kit at the top end of the range it is often just as cheap to replace the whole set of rear cogs. The cost of replacing the lot can sting a bit, but 5 years out of a chain+cogs is good value for money if you are using the bike regularly.

billyk

if its 5 years old and regularly used replace the block,chain and chainset.
easy way of checking the chain is lifting the chain with your finger from 3 o clock on the chainwheel and if the chain comes up more than 5mm its worn, to check the chainwheel just feel the teeth, compare the least used ring against the most used ring, the teeth get sharper the more they wear, checking your block is similar to the chainwheel just compare the gears you use most against the ones you use least and if there noticably sharper its worn. its common for all to be worn on a bike this old and regularly used

doozerie

billyk wrote:

if its 5 years old and regularly used replace the block,chain and chainset.

I wouldn't automatically assume that the chainset needs to be replaced. It really depends on the quality of the chainset, how you ride the bike, etc. I have been using the same Campagnolo front chainrings for over 12 years now, and the smaller ring now looks ready to replace (the big ring is only slightly worn) - I have clocked up a lot of miles on that bike too. I have lost count of the number of times I have had to replace the chain+cogs on that bike. In the same period of time I have replaced the Shimano middle chainring on my mountain bike several times (and the large chainring about once). Those particular Campag rings are just very, very, hard wearing (and probably give my chains a harder time as a result).

I wouldn't have believed that I'd get so much use out of one chainring, but the thing just seems to be made of granite. I wouldn't expect to get the same value for money again though, but having said that I also wouldn't assume that 5 years is all that you could expect of any chainring.