Moving cassette

high tower

Hi just a quick question, been setting up front and rear gears and have noticed that at a certain point in a crank rotation the chain seems to skuff the front meck making it difficult to get the correct alignment, but on the same gear later on in the revolution there is no skuff.

I have the bike on a bike stand so have spun the crank as fast as I can and if I look straight down at the cassette I can clearly see the cassette moving from side to side but obviously enough to knock the chain out of alignment.

The wheel look true as well.

Any ideas or suggestions would be great.

lc1981

Could there be a spacer behind the cassette that is missing? What cassette and wheels do you have?

wishitwasallflat

The cassette should not move - is the lock ring done up tight? If it is do you have all the correct spacers fitted? If yes - are you sure its the cassette moving and not the wheel - is the QR tight enough and is the wheel properly in the dropouts?

If its the front mech that its touching is the chainset properly fitted to the BB - is there any play is the chainset moving perhaps? Is the front mech moving?

PS - Best place for this type of question is on the Workshop forum - loads of really knowlegable and helpful people answer questions on there all the time (not chancers like me who fancy they know a bit )

desweller

I'm a bit confused. You say the chain is fouling the front derailleur? So you should be checking your chainrings and front mech, not the cassette.

high tower

Thanks for the suggestions. Will try them in the morning. The rings and crank look ok with no visual movement and no signs of play. The only play I could find was in the cassette. Thinking along the lines of if the cassette has play then this would effect the chain line intermittently through the pedal stroke possibly causing the rubbing on the front mech. The rubbing on the mech only occurs through a quarter of a full crank turn.

desweller

If the contact occurs in the same place on the crank revolution, rather than the wheel revolution, then there is a problem around the crankshaft/chainring area.

high tower

Thanks. That's what I thought but couldn't see anything. Will work out something in the morning to be able to check the crank/chain rings are true. Will post the result as may help someon else in the future.

smoggysteve

Check your wheel as not become buckled. A loosened spoke will effect the alignment on the hub and make it look wobbly also. After seeing this many times it is rarely the cassette or the freehub. Spoke tension is the closest single point of failure on a wheel and first place you should look.

desweller

high tower wrote:

Thanks. That's what I thought but couldn't see anything. Will work out something in the morning to be able to check the crank/chain rings are true. Will post the result as may help someon else in the future.

If you flip the bike onto bars and saddle, you can drop the chain off the chainrings around the bottom bracket and spin the cranks without driving the chain. It's usually pretty easy to see if you have runout with the bike upside-down anyway as you can get your head right over the problem area.

nicklouse

so if you get the wheel up to some speed and then hold the cranks you can see some movement in the cassette?

or the cassette is lose on the hub?