Hello guys,

I own a Trek 1.2 with a triple chainset, and the front shifter has recently been giving me nightmares.

Unless I set tension to the absolute minimum from the barrel adjuster, it won't shift down at all. When on the middle ring, the derailleur is rubbing the chain towards the bike, and the limit screws don't seem to make any difference.

And, starting yesterday, the lever won't come back into position when shifting up, meaning that I have to push it by hand. Also, moving it requires a lot of force compared to the rear shifter, with witch I have never had any problems.

So, I was looking for some advice related to adjustment. It is steadily getting worse and worse. I would like to fix it myself and avoid going to the local bike shop - the prices in Central London are way beyond my student budget.



joemmo [1132 posts] 3 years ago

it sounds like there's a couple of problems; cable friction and cable adjustment.

First thing you need to do is replace the cables. You could try just doing the inner cable but you're best off doing the outer cable as well. If they are Sora levers then the cable should be external so you shouldn't have to unwrap the bar tape to get to it.

Before adjusting the cable, check that the front mech is straight - outside plate should be parallel to the chainring - that it isn't bent and that the outer cage is the correct height above the teeth of the largest chainring - about 2-3mm is ok.

Put a bit of lube on the pivots as well and check the mech itself moves freely up and down. If you get salt and grit into the pivots (happens this time of year) then it can quickly corrode and jam up the mechanism. If this is the case then try taking the mech off and soaking it in some oil then giving it a good workout by hand to try and free up the movement. If it's still stiff then replace it (2nd hand is fine)

Once that is done you need to adjust the cable tension & mech travel correctly. With the chain on the smallest ring at front and largest at back, adjust the limit screws so the derailleur cage is just clear of the chain - it only needs to be a mm or so, enough so it doesn't rub under pressure.

Next, you need to pull the cable tight and clamp it so there is no slack that needs to be taken up when the lever is pushed to change up. Once this is done. change to the large ring, small sprocket and adjust the limit screws so the outer cage just clears the chain.

If that doesn't do it then the only other culprit I can think of is the lever though they generally just fail rather than degrade slowly. You could try giving it a squirt of oil, clean and a light greasing to the ratchet mechanism, if you can get to it in a sora lever. If the lever is knackered then things get a bit more expensive unfortunately.
good luck