Monday, July 13, 2009

How to Repair STI

Shimano's mysterious STI shifters often frustrate mechanics attempting to repair them. Put away your conventional tools. The answer is acupuncture.

6 comments:

Ham said...

Confucius say: "Never tly acupuncture on bloken tyre"

William Seville said...

Please, say some more!

I'm a campy brifter user, primarily because I know how to repair them when they do break. I can fix most things, but shimano brifters are in the too-scary box. (Rumour suggests one needs five hands)

Seriously, some de-mystification is in order, if you can deliver it

cafiend said...

I wish I could. While I have managed some minor repairs inside Shimano MTB shifters, the brain cases of the road units have proven impossible to crack.

Most commonly, failures occur in road or mountain STI shifters because the lubricating grease turns to "earwax." The stiffened grease impedes the ratchet pawls.

Less commonly, springs in the mechanism fatigue and break. One might harvest a replacement spring from a donor shifter. Installing it is like repairing a watch.

Since road shifters resist disassembly, your only hope at the early symptoms of earwax is to shoot them full of a spray lube to flush out the congealing grease. PG2000 has worked well. You might then want to follow up with something like Boeshield, to leave a more lasting lubricant.

Late in life, Shimano brifters get wobbly, especially if they've been torqued hard by a vigorous rider. At that point they're just finished, as Shimano intended. Then you get to find out whether the Big S still supports the product. Best of luck there.

Steve A said...

Why didn't I see this post before I fixed my STI? Now I'll have to see if I can't find some of that PG2000.

Tim said...

I've just bought a Shogun Samurai with RSX100 brifters that only shifted up. It's an 8 x 2 set up. This morning I pulled the hoods back and squirted them full of WD40 and rode to the bus stop as usual. I hopped off the bus and onto the bike, and found that I can now shift up and down on the 8 speed cassette with the right hand brifter. I've added more WD40 to the left hand brifter and will leave it overnight, hoping for success with the front derailleur tomorrow. Thanks for the tip! I realise that WD40 is not a long term lubricant, so I will try to gdet some lithium grease into the works later, but I'm still very wary about dismantling these babies.

cafiend said...

Aieeee!!Tim! Ixnay on the lithium grease! If anything use a light lube like Boeshield or a similarly flowing product to avoid the problem of congealed grease in the future.

RSX is one road brifter you can sometimes actually get a peek inside. This makes it easier to target problem areas. Pick and poke very carefully at the plastic covering the brains of it. When you pull the brake lever that part is exposed. You may find a loose bit you can pry up slightly. Or sometimes that covering is already broken. Don't break it if it isn't already, but you can use the "skull fracture" for access if it already is.