gear slipping

rikmellors

i've got a cannondale synapse, its 105 groupset but i have a slight annoyance in that normally the gear change is very smooth but going up and down the gears between the 2nd and 3rd cog i have to perform half a click of the gears skip 3rd completely, its worse coming up the block than down but does the jump in both direction. is this a cable adjustment issue? any advice greatly accepted.

smidsy

If all other gear changes are fine the cable tension must be OK so that means its more likely a worn cog in the cassette. Is it on the one you tend to be in most by any chance?

keef66

Cable could be starting to fray inside the shifter?

Release the cable clamp at the rear mech then peer inside the shifter while pulling the brake lever. Push the cable so the end with the nipple pops out of the side of the shifter. Any sign of kinks or fraying, replace the cable.

Ouija

If it works in all other gear except one or two it's usually a sign of cable binding. If you've got a derailleur with a big loop of cable coming off the frame and into the back of the derailleur then it's usually this part that causes dodgy shifting as the combination of a sharp curve and road dirt/rust tends to build up in it so that the amount of cable moved at the shifter end of the bike doesn't transfer fully to the derailleur. Often, only after you've pressed the up or down shifter twice does the cable 'unstick' and move, like a tectonic plate, and then jumps two cogs instead of one.

Replacing the loop with a new one and a new inner cable (preferably low friction Teflon/PTFE) will fix this. The alternative is to convert the derailleur into a direct pull design (no, or minimal loop) with something like the Avid rollermajig or Rose bikes WCW Easy Roller.

rikmellors

thanks ouija, i know its not wear (if it is i'm gonna be hacked off) the bike has only done 400km. i got it in august and did not get chance to get a lot of miles in it before winter. i'm now on my old road ace on the turbo trainer. I've had a look at the cable and you are right its a big loop. its only seen water a couple of times so i've taken the cable off and lightly greased the section in the loop then fitteb back and adjusted. the gear change seems seamless between 2nd and 3rd just like all the other gears. i thought it was the cassete cog sizing as this is where the biggest jump takes place into what i lovingly call my hill climbing gears. the cassete runs 11-28 but 1st and 2nd have a larger jump than all the rest. since i dont like hills particularly (i'm still way too big for them) i tend to run 4,5,6,7 mostly whilst riding the flat so dont do that gear change too often. thanks for the advice and i will have a look for the pully element, its quite a neat idea.