new cassette, new chain, chain slips when NOT under strain

[Cyclist33]

sounds like your derraileur is out of line, you need to set the limit screws up correctly.

it would be more likely the barrel adjuster that needed adjusting. the limit screws as far as i can tell, er, limit the inner and outer planes of the derailleur but dont affect the mid range very much.

it sounds like a classic indexing issue to me. the chain wont actually be slipping,it just feels like it is. its actually trying to derail to another cog because its slightly out of line with the one its on. but notnfar enough over to actually shift. have you got a turbo trainer? its an ideal way to lodge your bike in the riding position while you see to the gears!

stu

 

[SatNavSaysStraightOn]

Apologies for the delay but a combination of a really bad week & poor health has meant that I have not managed to look at the bike until today. (so far Wednesday, 1/2 of Thursday and this morning have all been cancelled due to my health)...

I am certain now with the bike on the turbo trainer that this is an indexing issue. I can physically see the chain trying to come off the ring (terminology?) it is on for a moment and then going back to where it should be. It does it for 3 or 4 teeth or so, then returns. I also think there is some 'play' in the rear derailuer because it seems very slightly out of vertical but I can move it side to side (so horizontally away from the wheel) and there is a couple of mm play - don't know if that is normal or just normal wear & tear.

 

[fossyant]

Play in the mech won't cause the skipping, unless it's really loose. Couple of turns with the indexing screw should have the gears sweet.

 

[SatNavSaysStraightOn]

Play in the mech won't cause the skipping, unless it's really loose. Couple of turns with the indexing screw should have the gears sweet.

good to know about play in the mech... just a few mm and not enough to foul spokes.

had to play with both front & rear derailuers. both needed more movement to allow on both screws! front derailuer was catching on the chain and when that was dealt with stopped allowing the inner chain ring, so had to adjust other screw to get that over. rear was also a mess... larger cog needed multiple turns of the relevent screw to get it to stop slipping and stay put which promptly messed up the smallest cog... ahhhh hate derailers.... might still have to take it into a shop - making a racket but does now work and should get me through the weekend...
thanks all.

 

[fossyant]

Hmm shouldn't be making a racket. Have you checked that the jockey wheels aren't touching the rear cassette ? If they are rather close, you need to turn in the b screw - this is the screw on it's own at the rear top of the mech that faces backwards. This adjusts how close the jockey's sit. Screw clockwise to push away from cassette sprockets.

 

[SatNavSaysStraightOn]

tis now on its tightest (screwed all the way clockwise) position and quite a bit quieter. thank you.

 

[SatNavSaysStraightOn]

Ok back from a quick test ride, bike is much quieter out riding it... gears are not slipping and seem fine all except occasionally (OK 10 out of 30 attempts) moving front derailer, from middle chainring to inner chainring. but not sure this is a derailuer adjustment issue because I have noticed that when this happens, the lever marker on the sti's is not moving and I am wondering if it is something else? bike is clean at the moment (unusual I know but...)

 

[Cyclist33]

that sounds like you have the lower limit screw quite tight but also the barrel adjuster set so the derailleur cage is by default, quite far out, this would mean that youve limited the movement of the mech so that it cant get to the small chainring.

you seem to be working out how to do this indexing thing, i find im often making small adjustmnts on the fly. if youre ever in warrington, drop by and stick your bike in my turbo trainer and we can have a look...

stu