I have a Trek 850 Mt. Track XL that I bought in 1996. It has 21 speeds. It originally came with grip shifters, but I had a bike shop replace them with Shimano Rapidfire shifters shortly after. The shifters are sort of integrated into the brakes. The model # information on them are Shimano STX-RC. Underneath is labeled ST-MC33. Neither of the shifters work any more. I've tried lubing them to no avail. Can anyone recommend a replacement set of shifters that will fit on this bike? I've attached a couple of photos, but my camera doesn't take very good pictures up close. But maybe it will help someone recognize the model I'm talking about. Any help appreciated.

awrightus, Welcome to the forum.

The shifters will need to be first degreased with something like WD40 or mineral spirits, then lubricated with Tri Flow, LPS2 or similar. If Shimano shifters have not been used for awile the grease hardens, preventing proper ratcheting.

Brad

The lubing I've done thus far is just by squirting it in a little hole in the unit. I've been reluctant to take them apart, thinking there might be some spring in there that I wouldn't be able to re-assemble. There's an allen screw at the bottom of the unit, and it clearly can be taken apart. Would you recommend that I take it apart to degrease? Any gottchas when I take it apart?

Since they don't work now what have you got to lose? The gottcha is losing that tiny little screw. Good luck.

+1

If you're worried about small parts flying off, disassemble inside a large ziplock style bag. My Number 2 son (turning into a good amateur bike mechanic ) picked up a used mountain bike and the STX-RC shifters didn't work, the flushing w/WD40 and relub'g worked... just seems to be a Shimano grease issue that I've had, along with others regarding both road and mountain integrated shifters.

Brad

This is what I did to my Shimano shifter that got stuck: I unscrewed it, but didn't open it completely for fear of losing parts. Instead, I cracked it open enough to fit a WD40 straw through, and squirted a whole lot of the stuff in it. I then let it stay overnight, and the next day it worked perfectly, and hasn't failed again since.

Don't be afraid of taking them apart. The internal guts of the shifter don't actually come apart. The trickiest part that you'll need to reassemble is the gear shift indicator.

Remove the shift cable before trying to take apart the shifters.

I've had good luck with using alcohol to dissolve the old dried out grease.

i usually pop off the cover for the cable(usually missing by this time) and squirt a whole mess of lube inside. also try some upward pressure on the thumb lever. the cheapest options for replacements would the the ef50 ones from shimano. i would try to fix your current ones

Cheapest replacement option I usually use are some Shimano trigger shifters. I get mine at Niagara for $13.

If you cant fix them, you can replace them with any Shimano 3x7 shifters. Plenty of cheap options available.

Took things apart over the weekend and didn't go very well. Got the right shifter apart and squirted a bunch of WD40 in there and let it sit for a while and didn't seem to make a difference. Looking at the guts to this thing, and I'm sure I'm not using the right terms here, but there's sort of a sprocket and then a ratchet that the thumb shifter uses to move the sprocket. That piece isn't even touching the sprocket, it just moves right over it so there's just "full play" when I shift, no parts touching. Maybe I don't really understand how it's supposed to work.

The left shifter was a bit different. The allen screw that I took out to take it apart didn't want to come out. It felt as if it was cross-threaded in there. I ultimately got the screw out and squirted some WD-40 in there, but it won't go back together properly, the screw that is. I'm pretty sure the hold is cross-threaded. Interestingly, I now have two shifts on the left, which is an improvement, but the cover to the shifter won't stay on completely since the screw seems cross-threaded. So, seems like the best option would be to buy a replacement. I'm poking around online for "shimano 3x7 shifters". If anyone has specific recommendations, model #'s, web sites, etc, I'd sure appreciate it. Don't need high end, just functionality.

I use these all the time. Cheap, effective, come complete with cables and housings, $12.60.... They also make a six speed version.

https://www.niagaracycle.com/product_...ducts_id=15889

That's the common failure mode. The little "pawl" gets glued to it's pivot by the dried out grease. You need something stronger than WD40 to dissolve out the old grease. That's why I mentioned alcohol, and bradtx listed mineral spirits. The teeth on the ratchet wheel can also get caked full of enough grease that the pawl might skip over them.

You need to approach the issue like a dentist, cleaning each tooth on the ratchet, and working the pawls back and forth until they move freely. The springs on the pawls are quite weak.

If the guts of a MC33 left shifter are the same as a MC30 shifter, then there's a dried grease failure mode that gives you just two gears. Getting the third (last) gear requires freeing up a stuck pawl.

You don't have many choices. Your situation is compounded by having the brake levers integrated with the shifters. If you can find some separate 3x7 shifters, then you'll need to find some brake levers too. You'll need ones for "canti" brakes, which are themselves getting hard to find. Or you can butcher your wonderful looking STX-RC units and cut off the shifter mounts. As for integrated units, I think your only choice these days is the canti brake version of the Shimano ST-EF50 (EasyFire) shifters. Don't get the V-brake version!

The picture you posted shows a nice condition bike. I think the only thing wrong is that your grease is dried out. (And maybe the cross threaded bolt...)


BTW, if you give up on the STX-RC units, put them up on eBay. Even "broken", they might sell for more than new EF50's.

you can cut off the shifters and keep the old levers. did you try upward pressure while pushing the big thumb lever? i fixed a left one yesterday with the same technique and solvent.