Chain "jumping"?

cunnins4

Hi guys, my chain keeps jumping if i'm in a high gear and if i try to push hard at all. It happens when i'm on the 6th/7th/8th ring on the rear cassette and with any of the front 3. It used to only happen when on the second at the front with 7 or 8 at the back. It's pretty annoying.

Any help is appreciated.

BTW, if my explanation of the gears is confusing, i mean when i'm in 6th/7th/8th/14th/15th/16th/22nd/23rd/24th etc.... if that's any clearer.

cheers.

Bunnyhopper

How long has the chain been on the bike? Might it be that it has just stretched enough to become problematic? Also, if the cassette has done quite a bit of mileage then it might be worn too.

Morgan

What do you mean by "jumping"? Is the chain moving between cogs at the back or sliding over the teeth of a cog?

cunnins4

I guess I've had the bike for 18months now, with the same chain on it. It's a rigid Hardrock XC, and yes, it has done quite a few miles as i used it to train and race in my first triathlon in September. I'd say a total of 3500 miles or more all in.

It's hard to tell whether it's going between cogs, or the chain is slipping over teeth because i have to be giving it a bit of force when it does, so when i look down, the bike jolts, and i tend to miss seeing what happens. It's really hard to see because it happens so quick.

I should probably just bring it to cycleways, but I really don't have the cash to pay for repairs at the moment, so if it's a DIY job, i'd prefer that solution.

It seems to be getting worse by the day!

cyclopath2001

Another possibility is a stiff chain link.

Usually only happens after a new chain is fitted and the chain is closed incorrectly. Make sure each link is turning freely. If not, you'd need to use a chain rivet tool to loosen the link.

Civilian_Target

Sounds to me just like your deraileurs need adjusting to be honest...

Mucco

It could be that your rear mech needs adjusting, but it sounds more like a knackered chain and cassette. It's in the small cogs when it happens?
Chains stretch over time, and if they're not replaced, they wear out the cassette because they don't match exactly anymore. Try sticking a new chain on and see what happens - it'll probably get worse, so a new cassette could well be needed too.

M

Alkers

cunnins4 wrote:

Hi guys, my chain keeps jumping if i'm in a high gear and if i try to push hard at all. It happens when i'm on the 6th/7th/8th ring on the rear cassette and with any of the front 3. It used to only happen when on the second at the front with 7 or 8 at the back. It's pretty annoying.

Any help is appreciated.

BTW, if my explanation of the gears is confusing, i mean when i'm in 6th/7th/8th/14th/15th/16th/22nd/23rd/24th etc.... if that's any clearer.

cheers.

You should only be using the 6th 7th and 8th rings with the big ring on the front in the first place. It stretches your chain if you are in the small ring on the front and the small ring at the back. If you need 8th for example go in the middle ring on the front and the 4th ring on the back.

cunnins4

Simona1986 wrote:

You should only be using the 6th 7th and 8th rings with the big ring on the front in the first place. It stretches your chain if you are in the small ring on the front and the small ring at the back. If you need 8th for example go in the middle ring on the front and the 4th ring on the back.

I never use the small ring on the front, ever. And rarely use the middle one. I tend to stick to the big ring 80% of the time. I was just saying that it's not unique to the big ring, it occurs on the small cogs regardless of what ring i'm on at the front.

I'll try adjusting the derailler. Hopefully it'll come good. I always hate doing that though, cos it can take ages to get it right. Another question - the adjuster on the derailler - the one that the cable goes through, and you can twist it - what does that do with relation to the derailler? The bike took a knock shortly after i got it and that broke, so i can't adjust it anymore. It never affected the shifting, so i just left it as is.

cyclopath2001

cunnins4 wrote:

Another question - the adjuster on the derailler - the one that the cable goes through, and you can twist it - what does that do with relation to the derailler? The bike took a knock shortly after i got it and that broke, so i can't adjust it anymore. It never affected the shifting, so i just left it as is.

It controls cable tension. So if your control cable has stretched or moved (with wear), your gears' click-stops may be a bit off. So, your jumping could be caused by the derailleur not centering the chain on the rear sprockets (cogs) as you change gear.

You may be able to tweak that out by adjusting the cable tension by opening the cable-securing bolt and pulling the cable, but it's easier if the tension adjustment thumb-screw is working.

There should be two screws on the derailleur. These adjust the limit of inside and outside travel, leave them alone unless the chain is going too far in or out on the extreme sprockets, or if it's not resting correctly on them.

roadmanmad

If the chain has done 3500 miles, it may be worn.

The sprockets on the back are also probably worn.

Replacing all may be needed.

dannybrowne123

i would say hub is shot. happened to a friend recently.

Take the wheel off and swap w/ a friends or something.

if the hub is indeed goosed you'll need a new one and to have the rim re-laced. about 70 quid in cycle ways.

kona

unless youve really really good rims why the hell would you want to rebuild a wheel, and pay e70??, youd get a brand new deore hub with a decent rim and spokes for around e50.
try replacing the gear cable, if that fails, replace the chain and cassette.