Gear Jump Problem

[Jonjay]

While I was out today, about half way in to my ride the gears suddenly started jumping down the cassette on down shifts. Had been completely fine then all of a sudden just started.
pretty much fine going up, but when shifting down it jumps all the way to the smallest cog with a single click of the shifter. The shifter kind of feels like it’s clicking multiple times.

I tried adjusting barrels at the shifter and mech but made no difference. anyone have any suggestions?

the shifters and mech are Microshift. On Triban Rc120

cheers

 

[Big John]

I'd start with the shifter. If it were me I'd remove the cable from the rear mech. Hold the cable in your left hand while clicking the gears up the gears. You should feel the cable being pulled with each click. Then come down the gears. Normally you'd feel the cable being released with every click but if it replicates what happened on your ride then the shifters at fault. If that's the case then either try and fettle the shifter or seek a replacement one. Keep us posted. If it's not the shifter we can have another think. To me it doesn't sound like the rear mech but I have been known to be wrong 😉

 

[Jonjay]

Cheers I’ll have a look in a bit and try that. sounds like a good plan.

 

[Ajax Bay]

It's the shifter. Besides John's advice, a good old squirt of GT85 in the shifter's orifices never does any harm.

 

[Jonjay]

Assuming it is the shifter, what’s the cause? Is it fixable?
cheers

 

[Ajax Bay]

Have you already done what John and I have suggested? What was the outcome? Model of Microshift and speed of drive train?

 

[Jonjay]

I have and you were right it seems to be the shifter. When pulling the cable and down shifting it just jumps to the end of the range.

not sure on model of micro shift. It’s just basic as it’s an entry level bike. It’s 8 speed.
cheers

 

[Ajax Bay]

If you can't get it to click up and down, then it's replacement time I'm afraid. Even the Shimano STIs eventually expire (ime). Lots of little bits and ratchets inside.
If you don't care about matching then you'll find used 8sp Claris set of STIs for not much. Or old Sora ST-3300. Compatible with your rear mech.

 

[Jonjay]

It’s weird it clicks up fine. Just jumps down.

the shifters aren’t old either. Only a few months and never been out in the rain.

 

[Big John]

If spraying GT85 inside the shifter doesn't get a result then take a gander at it to see if there's anything obvious i.e. a bit that looks like it's missing a bit, etc. I've found when it comes down to the intricate parts in shifters I really haven't got an engineer's mind. I've taken things apart only to end up throwing the parts in the bin because I can't put it back together again. STIs are renowned for being user unfriendly but any shifter is pretty clever when you get inside it. I'd line up a replacement now if I were you 😉

 

[Jonjay]

Sorry, got another (probably stupid) question.
I’ve taken the bar tape off ready to replace the shifter. I tried degreasing inside the mechanism in case it was clogged up, but that’s done no good.

So the question. Can I detach cables at the shifter end or do I need to disconnect the front brake and rear mech cables and feed out? Of the latter, can I reuse them cables as they only have about 250 miles of use.

cheers again.

 

[C R]

Sorry, got another (probably stupid) question.
I’ve taken the bar tape off ready to replace the shifter. I tried degreasing inside the mechanism in case it was clogged up, but that’s done no good.

So the question. Can I detach cables at the shifter end or do I need to disconnect the front brake and rear mech cables and feed out? Of the latter, can I reuse them cables as they only have about 250 miles of use.

cheers again.

With such low mileage, is the bike new? If it is, that would be a warranty claim, wouldn't it?

 

[Jonjay]

I’m waiting to hear back from decathlon. But the replacement shifter is under £30 on their website so might be lesss hassle just to replace it myself

 

[C R]

I’m waiting to hear back from decathlon. But the replacement shifter is under £30 on their website so might be lesss hassle just to replace it myself

Being within the warranty period I would make them deal with it. You may be voiding the warranty altogether by doing this yourself.

 

[Jonjay]

That’s a good point. Hadn’t thought about that