Chain falls down cassette whilst back pedalling.

slowbike

Odd one this - hopefully someone else as come across it and fixed it before.

Set - 8 speed Sora.
Chain - kmc x8-93 new in July

First manifested when she was starting off - being a left foot starter (ala track riders) she tilted the bike to the right then spun the crank round backwards - the chain then ran down through the gears - causing an issue as she's now not in a gear that's set!

Thinking the chain is too long I took a link out - that hadn't resolved and up on the stand today I applied hand pressure to the dérailleur to give the chain more tension and it still ran down the cassette whilst back pedalling! So I think that means another link out wont fix it .....

Now I can't think what to do next .... Perhaps the chain doesn't fit properly - it's only done 100 or so miles. The cassette is only 500 miles old.

Any suggestions?

halfround

Could be a dirty or dry chain, a stiff link or gummed up pulley. I would clean and lube chain, check all links are free and take pulleys out to clean and lube.

nicklouse

Don't back pedal.

Simple.

cycleclinic

Why are you backpedalling the drive train is not meant to work that way. Chains can derail when back pedalling. Do do it!

slowbike

halfround wrote:

Could be a dirty or dry chain, a stiff link or gummed up pulley. I would clean and lube chain, check all links are free and take pulleys out to clean and lube.

I'll have a go- but it's pretty clean already.

slowbike

thecycleclinic wrote:

Why are you backpedalling the drive train is not meant to work that way. Chains can derail when back pedalling. Do do it!

How do you get the pedal from the bottom back up to the start position then? I've always done it, so has pretty much every cyclist I've seen...
Right now her only way of starting is to scoot along until she's got enough speed to sit on the saddle and pedal ... Not really helpful...

I've checked on my 105 equipped bike and it doesn't do it ....

dee4life2005

My ultegra drivetrain does this from time to time, on the front cog if i back pedal - but i only do it a max of half a revolution when stationary to bring my clipped in foot to top of pedal arc for max power when moving off. Depending on gear combo the chain will seem to partially derail but the gear is still engaged and works.

Did accidentally back pedal when moving bike out of the house one day and the chain was sucked up the front cog and jammed between the small ring and bottom bracket (triple chainsets). It was so well jammed i had to take the cranks off!!! Not the best starts to a ride that...

jezzpalmer

Unless the chainline is pretty straight, it will try to become straight when you back-pedal as there's no derailleur to guide it.

desweller

I've never had a bike that I couldn't backpedal, as long as the shifter had not been changed while the bike was stationary. Nicklouse and tcc are wimping out ;-).

Stiff links/dry chain, loose or bent derailleur hanger or the gaps between the sprockets are full of shyte. They'd be my first ports of call.

cycleclinic

Were are not wimpig out. Backpedalling sometimes work for a short while but not for long. Generally back pedal when not is a cross chaining. If you cross chain and back pedal the chain will try derail and it only take a slightly misadjusted stop/slight bent hanger for it derail of the cassette.

Still don't back pedal and there is no issue. bakckpedalling half a turn to the the pedal in the start position is not really backpeddelling.

slowbike

thecycleclinic wrote:

Still don't back pedal and there is no issue. bakckpedalling half a turn to the the pedal in the start position is not really backpeddelling.

No - but that's when it's occuring ...

I've had another look at it and there's a little offset from the middle (more from the outer) chainring (it's a triple) to the 1st or 2nd cog on the cassette - couple that with the leaning the bike to the right seems to exacerbate the condition. She'll have to learn to start off on the right foot!

CiB

Couple of thoughts. Does it happen in all gears? I lube my chain by pedalling backwards with one hand whilst squirting the lube with the other - it has to be in a middle gear and the bike upright or the chain falls down the cassette and stops spinning freely. Pedalling backwards allows the chain to find its natural path, so start with it where it wants to be if back-pedalling is the only way.

Getting on & started doesn't need to involve back-pedalling - I find it easier to slide onto the seat and clip into whichever pedal is nearest to the top of the stroke after TDC, then get going. If you prefer to clip into a pedal at the bottom of the stroke, it doesn't take much to lift the rear wheel and spin it forwards rather than backwards to position it.

slowbike

most gears yup - I guess it probably doesn't in the granny ring ...

standover height is compromised so she's not lifting the back of the bike ...

I did suggest she "MTFU" ... but she put me back in my place

CiB

Slowbike wrote:

standover height is compromised so she's not lifting the back of the bike ...

Do you mean that she can't lift it when standing astride it? I envisaged doing it before clambering aboard tbh, but I see what you're getting at more clearly now.

Best way would be to get into the routine of clipping into the highest pedal, if that's possible.

Edit to add - alternatively, do the back pedal, then rock the bike forward with the front brake on to unweight the rear wheel still with one foot on the ground and pedal forward to unwind the chain misalignment. Sounds convoluted, takes 2 seconds in reality.