I'm restoring an old Myatta 1000 and want to use a brake lever shifter that I have. It is a 10 speed shifter and I have a 7 gear cassette. Can i use this?
No, you can't. Indexed shifting requires all the components to be precisely matched. The shifters, derailleurs, chain and cassette all need to be compatible.
You didn't say why you want to replace your shifter. If the one you have works, then just leave it alone. Otherwise, you have the following options:
- Fix it.
- Replace it with a shifter that's compatible with the rest of your drivetrain (without knowing more about your bike, I don't know what that would be).
- Replace the whole drivetrain (shifters, chain, derailleurs, cassette, possibly front chainrings).
The brake lever has to be matched to the cable pull of the brake (short pull/long pull); V-brakes need different cable pull than caliper brakes, for example. Else, you'll have not enough power to stop or you'll lock up the wheel instantly.
The number of speeds on the shifter needs to match the number of speeds on the cassette (*). The shifter also has to be compatible with the derailleur.
Also, note that road and mountain shift+brake levers have different clamp diameters since the handlebars have different diameters, so you need to use road shifters+brake levers on a road bar, and mountain shifters+brake levers on a flat bar.
(*) There are a few special cases where you can violate this. 7 speed cassette with 10 speed shifter is not one of them.
In this case (assuming Miyata 1000; a drop bar road bike), I'd suggest finding a compatible brake lever (which will be easy), and using friction shifters (downtube/bar end). Or find a 7 speed indexed shifter which is compatible with the derailleur at hand (if the rear derailleur is Shimano, theres now a 7 speed brifter in the Tourney range, as well as one made by microshift; you can easily find 7 speed compatible index/friction switchable downtube or bar end shifters for Shimano as well).
It obviously depends on what you plan to do with your bike, but provided you're willing to get your hands dirty the answer is a definite Yes.
I have been riding my modified Tdf-100 (9-speed SORA with 7speed MTB cassette) for 10.000+ km, and I'd feel pretty confident saying that with a little bit of patience and careful indexing you'll have a perfectly functional bike, although maybe not competition worthy due to slightly sub-optimal shifting reliability and braking power. That said, as most of the other answers point out, you have to make sure of the following key points before you even start:
- You can fit the lever shifters to your bar (duh..)
- You can brake effectively with the available pull: from a quick image search it seems that Miyata1000s do mount cantilever brakes, which require a relatively long pull distance. You should first of all true your wheel (I haven't had time to watch the whole thing with audio but the guy seems to be using a method I personally found to be very effective). You may then proceed to adjust the cable tension by shortening the cantilever "beam" so that your brake pads rest as close as possible to the wheel, in order to reduce the required pull to a minimum. You should then be able to clamp the rim hard even with a relatively short pull lever.
You will then have to work around the mismatched lever/cassette indexing. There are two main aspects to consider:
- Lever Pull Reach: easily solved by careful tuning of the limit screws. Were your cassette larger than the lever range you'd be in trouble, but this is not your case.
- Indexing Step: chances are the sprockets on your 7speed cassette will be farther apart than they'd be on the 10speed your lever was designed for. This means that in theory you can only index ONE chain position to be perfectly aligned with a lever click and all the others will be working slightly out of alignment.
It is important to clean and lubricate the entire drivetrain, as you'll be striving to adhere to the First Law: Ye Shall Make No Sound as you make your adjustments.
Proceed as follows:
- Set your limit screws with no cable on (push and pull the derailleur by hand) so that both limit positions are about 1mm wide of the corresponding sprockets (i.e. left of the large one and right of the small one).
- Put the lever in hardest gear thus releasing all cable, pre-tension it and clamp it into the derailleur.
- If you can index your gears normally from here then RIGHT ON, skip the rest of this boring answer, sit back and enjoy this blissful moment of the-universe-sorting-itself-out-for-your-happiness. Otherwise..
- Index your preferred chain position: you can choose the perfect chain line (or maybe the sprocket you think you'll be riding on the most?). The more different the spacing is from the lever clicks, the more important that you choose a mid-range sprocket as your indexing centre, so as to minimise the maximum misalignment your jockey arm will have to endure. Click the lever into the desired position, and adjust the cable tensioner (or have a friend hold the derailleur in position as you unclamp the cable to make small adjustments) until the "indexing centre sprocket" turns smoothly and silently. Proceed to make small adjustments until you can smoothly shift up to softest, down to hardest, and back to your centre sprocket.
By trial and error you should be able to get to the stage where the centre sprocket and the closest four work smoothly with minimum racketing. The deviation between clicks and sprockets for the highest and lowest gear might be large enough for them to require TWO clicks (or a full lever swing) to get to, hence the need to allow a little extra slack on the maximum limiting screw (so that you may reach the click with the lever, then let the derailleur settle in position by clicking down once).
Extra trick: If and only if you're really not satisfied with the results of the above procedure, you can index your centre sprocket (Step 3) one click up, and have a "ghost gear" click below the hardest to release enough cable to reach the smallest sprocket. The low limit screw should then be as tight to the perfectly aligned position as you can get it. This will allow you a bit more room for manoeuvre but can get quite complicated since you won't be able to rely on the small-sprocket=cable-fully-extended equation.
It may all be a bit awkward at first if you're used to perfectly indexed gears but I take if you were that picky you wouldn't even be asking this in the first place. You'll get to know your ride and the way it shifts, and the half-pull and two-up-one-down will become second nature soon enough.
I hope this makes sense, I may have assumed prior knowledge in an attempt to keep it linear. Please comment if you need clarifications. Enjoy the hacking!