Centaur rear shifter problem

tomhammersley

Hello there,

I have a 2008 Centaur groupset. Previously, this was working just fine, I just had to sort out the indexing a few times. It's done about 2200 miles. However, it has now developed a new, strange problem.

If I have the shifter set to the largest sprocket, and press the thumb shifter button once, the rear derailleur jumps straight down to the smallest sprocket without clicking into any of the intermediate gears. The usual and expected behaviour is that one click makes it shift down one sprocket. It is as if the ratchet mechanism isn't working.

I can use the lever to shift back up to the larger sprockets one sprocket at a time - suggesting the ratchet mechanism is still ok. It is only when I use the thumb button to release it that it fails to operate and jumps straight down to the smallest socket. If, when using the thumb button, I use the rotating shift lever to "brace" it, I can then successfully make it drop down one sprocket at a time. Again, using the thumb button alone makes it jump straight down to the smallest in one go.

I've run through the usual gear set up procedures, made sure the cable is installed and seated correctly etc etc to no avail. I have some new inner cables on the way anyway, so I was going to try those.

I've only been using the bike in good weather and on the turbo. It's not been out in any dodgy weather.

It feels as if the ratchet mechanism or thumb lever is not quite working correctly or broken. If so, I'm assuming that's a LBS job or possibly a warranty claim? Has anyone else had and solved this problem, or a similar problem before?

Thanks!

Monty Dog

Firstly, check that that rubber hood is fitted propperly are isn't fouling the internals - likewise, fold back the hood and check for stray bar tape etc. Sounds as though you need to give the internals flush-out - could be dried grease or dirt in there thats stopping the ratchet from engaging. Flush out with a good dose of WD40 and GT85. Unlike STI's there's very little to go wrong internally in an Ergo shifter. If flushing through doesn't work, you may need to consider replacing the G-springs which control the indexing - the ratchet is a solid piece of steel which very rarely goes wrong.
Somebody like Mercian Cycles will sell you the parts of do it for you - cost is about £20.

tomhammersley

Hi Monty

Thanks for the tip. I'll give that a crack and see if that helps. If not, Mercian are only 20 minutes away from me, and about 5 minutes from my sister in law, so I'm sure I'll be over there during the holidays, I'll see if they can help.

Thanks!