Derailleur and crank problems

ol4eyes

New Member
Location
Skelmersdale
Previously, after an upgrade to cassette I could smoothly change gear. Just recently though, when I try to get into the smallest cog (rear) the chain wants to jump into the big cog on the front. I've tried re-indexing the gears, releasing the cable etc, even then it still wants to jump onto the big front cog!????
 

mjr

Comfy armchair to one person & a plank to the next
How many gears front and back? What derailleurs? Small-small isn't always supported and it's often not efficient when it is. Big front and third or fourth smallest at the back should be a similar ratio and more efficient anyway.

If I recall correctly, what you might find is the front low limit screw is too low for small- small but setting it so might make bottom gear more difficult to select.
 
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Ajax Bay

Veteran
Location
East Devon
Don't think you'll solve this by limit screw adjustment. In the OP's scenario the chain is on the small ring and when they drop to the smallest sprocket the angle of the chain brings it into contact with the large chain ring, or at least its 'pick up pins' (no influence from the FD). This can happen if the chainline has not been selected/designed with care. @mjr has asked for details but not sure that will change my suggestion.
 

fossyant

Ride It Like You Stole It!
Location
South Manchester
The OP's reference to the "big cog" on the front doesn't give any clue as to whether it's a double or triple chainwheel. If the latter, then I wouldn't class middle-to-small as cross-chaining.
Depends, on my old MTB it would try and shift due to the shifting ramps. Same applies though, too extreme an angle will cause shifting, especially 'up' to a bigger chain ring.
 
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