danhoro
Regular
I've recently acquired a Planet X RT-58 alloy with Sram Apex groupset. From the start I've found that it's not very smooth when shifting up to the bigger chainring. Sometimes it catches straight away, but around 50-60% of the time it takes what feels like 1/8 (maybe a bit more) of a turn of the crankshaft before the chain properly catches on the bigger ring. In the meantime, I get an unpleasant scraping noise as the chain is pushed up against the ring. Once it shifts up I don't have any issues with the chain rubbing the derailleur cage.
I've tried tightening the cable tension, which doesn't seem to have improved things. I assume it won't be an issue with the limit screws, so I haven't played with those. It looks like the derailleur is an appropriate height above the large chainring - about 2mm at the smallest distance.
I had a couple of theories. Maybe there is some flex in the bottom bracket meaning that it's harder to shift up when pedalling down on the right pedal. Also, the chainring has a number of smaller teeth, so maybe it doesn't properly catch until one of those rotates around. I don't know how likely either of these are?
I did wonder if it was just an idiosyncrasy of the mechanism, but I found this video of someone setting up the same derailleur and they get it running much more smoothly without a problem:
View: https://www.youtube.com/watch?v=HVI8q6GLLFw
Any advice much appreciated!
I've tried tightening the cable tension, which doesn't seem to have improved things. I assume it won't be an issue with the limit screws, so I haven't played with those. It looks like the derailleur is an appropriate height above the large chainring - about 2mm at the smallest distance.
I had a couple of theories. Maybe there is some flex in the bottom bracket meaning that it's harder to shift up when pedalling down on the right pedal. Also, the chainring has a number of smaller teeth, so maybe it doesn't properly catch until one of those rotates around. I don't know how likely either of these are?
I did wonder if it was just an idiosyncrasy of the mechanism, but I found this video of someone setting up the same derailleur and they get it running much more smoothly without a problem:
View: https://www.youtube.com/watch?v=HVI8q6GLLFw
Any advice much appreciated!