Clonk from the rear

[alan_sh]

My wifes EST-520 has developed a clonk from the rear where the chainwheel is. It seems to be when she presses hard(ish) on the pedals, the lower part of the derailleur gears (the bit that moves back and forwards as you change gear) moves forwards slightly and then there's a clonk as something releases and it all goes back into place (I was watching her as we were out riding today).

Has anyone any idea what it could be? It started about 5 miles into a ride just after we'd stopped for a drink of water.

I'm new to this game, so I have no idea what all the little screws do at the back (and of course, there's no manual).

Cheers for any advice

Alan

 

[steve_sordy]

It sounds like the shifting needs adjusting. The derailleur moves the chain to not quite the correct position and under light pressure the chain sits there. Once pressure is applied, things flex and "clonk" the chain drops into a lower gear. It won't do it in every gear, usually one of the middle ones.

There is loads of stuff on YouTube on how to set up your shifting. ParkTools stuff is good.

If the bike is new, has it had its first service? This usually fixes shifting issues that are caused by the outer gear cables settling in to their guides with the effect that the inner cable behaves as though it is longer. So when you shift, the mech doesn't move as far as it should.

 

[alan_sh]

It could be that, but the gearing doesn't change. Yes, it's now booked in for a service and checkup on Thursday.

I'll look up on adjusting the gears. Thanks for the hint.

Alan

 

[NULevo]

I had a noise from the gears for weeks, I checked and re torqued every bolt, checked the cranks, chain and everything I could see. Then I took the rear wheel off and dropped it from about 12 inches and heard the noise. Turns out the cogs on the cassette had worked loose, could't believe it when I took the wheel to my LBS and he tightened up the cassette in under a minute. It's not unusual apparently and when I was out on the bike today it was like a new bike.

The cassette can be checked by holding the large and and small cogs and turning in opposite directions. Any movement at all and they need to be tightened.

Good luck on Thursday, hope its something simple

 

[Zimmerframe]

Lots of other weird little things to check ..

There's what's called "narrow and wide" . If you look at your "chainring" that's the one at the front. The teeth alternate in size .. one is narrow, one wide. Make sure he chain is sitting narrow wide correctly with it's outer and inner links. Some derailleurs (the "jockey wheels") are also like this - so check that too.

Also check for tight chain links. One could be tight and not moving round freely.

Ideally, you want to lift the back of the bike. With the power off, move the pedal and watch. If you don't have a bike stand, a "peasant" stand - ie, hook the nose of the seat over something, so the rear wheel is off the floor. Or lift it with a strap over a beam or something and again under the nose of the seat .. or saddle if we're being correct ..

 

[highpeakrider]

If it’s not gears and it has an E8000 motor whip the cranks off and grease the splines and torque them back up again.

 

[alan_sh]

It has a Brose motor, I think.

 

[alan_sh]

Lots of other weird little things to check ..

There's what's called "narrow and wide" . If you look at your "chainring" that's the one at the front. The teeth alternate in size .. one is narrow, one wide. Make sure he chain is sitting narrow wide correctly with it's outer and inner links. Some derailleurs (the "jockey wheels") are also like this - so check that too.

Also check for tight chain links. One could be tight and not moving round freely.

Ideally, you want to lift the back of the bike. With the power off, move the pedal and watch. If you don't have a bike stand, a "peasant" stand - ie, hook the nose of the seat over something, so the rear wheel is off the floor. Or lift it with a strap over a beam or something and again under the nose of the seat .. or saddle if we're being correct ..

I'll have a check tomorrow - thanks. I do have a bike lift. I doubt the chain has moved on the front sprocket - as I said, it was working until we stopped for a rest. After we started again, wifey was up and down the gears (went the wrong way and got confused) and it started after that - so it could well be just a cable stretch - or possibly the rear canister internal gears (the ones that allow freewheeling) have broken - but it sounds OK when freewheeling so I am doubting that.

Alan

 

[slippery pete]

Could well be the pawls in the freewheel or a pawl spring. These are known to break. Usually there are two, three or four of them. If one breaks, the others still engage but the whole thing is more unevenly loaded and can clonk asit comes under load.

 

[alan_sh]

Pete, that is exactly what it sounds like. I'll pass the message on.

 

[alan_sh]

OK - took it in. The culprit? A bent chain link. It got replaced and all is well.

I wasn't aware they were that sensitive

 

[slippery pete]

Good result. Reading back, the clue was there...

wifey was up and down the gears (went the wrong way and got confused) and it started after that