mechanical-advice

Q & A

Shift Levers

5-Speed Shift Levers

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Hi,

We have an older bike that uses Shimano SIS TY15-A shifters. They have become brittle with age and the right one has broken.

Would the Falcon 5-Speed Thumbshifters 71250 be suitable as replacements please? Or would the Sunrace Friction Thumbshifters 1079 be better?
 
Regards,
Warren

 

Hi Warren,

Either would be OK. As long as the old system was 5-speed. The advantage of friction shifters is they're compatible with anything and tolerant of worn/sticking cables.

Cheers,
Mark.

A Rare Winter Gear Problem: Intermittently Missing Shifts on Shimano Road STI Levers

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We had a case in the shop recently of a bike that would sometimes refuse to upshift from the small to the large chainring. It was addressed first by tweaking the normal front derailleur adjustments. Twice. But, the bike returned, the problem was still there.


To change from the small to the big chainring with Shimano Road STI levers, you push the brake lever inwards (sideways). To change from the big to the small ring, you push a smaller lever (that nestles behind the brake lever) inwards. In a normal upshift, when the brake lever pivots in, the smaller lever behind it pivots in with it. If, though, you push the small lever a bit ahead of the big (brake) lever, then the shifter is being instructed to downshift and upshift at the same time, and it won’t shift.


I came up with the theory that, as a result of wearing warm winter gloves, the customer was sometimes inadvertently letting a finger slip behind the brake lever to pre-emptively push the smaller release lever to effectively abort the shift. I put my theory to the customer (Hi Roger!) who was, let us say, doubtful. Nevertheless, he allowed there was a slim chance that it made sense so off he rode home, pushing higher on the lever (with his fingers angled a little further forward) for front upshifts. We got a call an hour or two later from him – the gears were shifting perfectly.

A Common Winter Gear Problem: Non-Functioning Shift Levers

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Have your gear levers seemingly given up the ghost? You’re stuck in the big sprocket at the back, or the big chainring at the front? Or you can shift to some of your gears but can’t get to the rest? You can shift gear if you move the lever extremely slowly, but not at a normal pace? Or you’ve pulled that bike out from where it’s been under the house for a couple of years and the levers don't work any more?


Modern indexed shift levers have some fairly intricate internals including small pawls (small bits that push another part by engaging in grooves or valleys in that other part, as in a freewheel) that carry out their task with the assistance of very small springs. The shifters are lubed at the time of manufacture, and, generally, never again. The problem that arises in time is not a lack of lubrication, but that the original factory lube thickens to the point that it slows or prevents the movement of these light springs and pawls.


The proper (very proper) fix for this is to remove the cable from the shifter, remove the covers also, and disassemble the shift mechanism from the handlebar bracket (or brake lever) and to degrease it thoroughly, rinse it well, dry it well, then re-lube and reassemble.


However, the easy (and about 95% successful) fix is to spray a good thin lube (we use Tri-Flow) into the shifter from wherever you can manage. The port for cable installation is usually the easiest, and will often have a plastic plug about 8mm across that unscrews to allow access for the cable. Sometimes a plastic cover can be easily removed to allow better access. Not fixed yet? If you have access to a compressor, blow the new lube back out with an air gun. Then repeat the lube and air-blast a few more times.

Still not right? I had a lever today that was pretty stubborn so I removed one of the plastic covers and turned the bike upside down so I could see well into the lever. I identified the sticking pawl and with a small screwdriver moved it back and forth gently for a bit to loosen the factory grease. Then, lubed and air blasted (with good aim now) and worked the lever for a while until it worked as well as the day it was made.


The beauty of the easy fix is that if the problem isn’t perfectly fixed, the way to improve it over time is simply to spray another dose of lube into the lever each couple of weeks, using the bike in the meantime. Easy!