Bike Repair – Smooth Shifting

SRAM shifter on a bike

Imprecise shifting and a chain that wanders up and down the cassette of its own accord can really spoil your ride. The good news is that the solution takes seconds.

When your gears are mis-shifting then it’s almost certainly time to take a look at your gear indexing – the relationship between one click of the shifting lever and the distance moved by the front or rear mech. A correctly adjusted set-up will mean your chain can pass smoothly from one cog to another.

Not knowing what bike you have, here are the three most common adjustments associated with gear systems from Campagnolo, Shimano and SRAM. One common mistake when it comes to adjusting indexing is taking a screwdriver to the two limit-screws in an attempt to rectify a noisy or mis-shifting chain. These screws are present only to limit the mechs from shifting the chain too far. They should only be adjusted when you’ve replaced a worn cassette or rear mech or you’ve fitted new cranks, for example.

The first thing to do is to make sure your cables, mechs and chain are in good, serviceable condition because this can adversely affect the way they operate; it’s no use trying to adjust something that is worn beyond adjustability. If you’re having trouble shifting up and down, chances are you’ll need to clean your gear cables or fit new ones. A new chain, and possibly a new cassette and/or chainrings might well be on the cards too.

Also ensure that there’s no play in your bottom bracket bearings because wear here will skew the adjustments you’re about to make to your gears. If you have an old tapered bottom bracket on your bike, now is the time to make sure the crank arms are tight on the axle. If you have this type of crank and bottom bracket, tighten the crank end bolts to 26Nm with a torque wrench. If you don’t have a torque wrench make sure the bolts are tight using the appropriate Allen key or 14mm hexagonal socket.

If the cable adjuster on the rear gear mech is already screwed halfway out, then make adjustments only to the frame-mounted adjuster or one that’s in-line with the cables.

SRAM Double Tap

Slow to larger cog

SRAM can shift up to three cogs at a time, but uses a single lever to perform both up and down shifts. If the chain is slow to shift to a larger cog, unscrew the aluminium adjuster on the back of the mech (anticlockwise) a quarter of a turn until the chain shifts smoothly. Due to the leverage ratio SRAM uses on its shifters, start with quarter turns on the cable adjuster before fine-tuning with eighth turns.

Slow to smaller cog

Press the right hand lever up to, but not beyond, the first click and observe whether the shift to the next smallest cog is smooth and silent. If it isn’t, you need to screw the rear mech cable adjuster inwards (clockwise) until the chain shifts smoothly and quickly. Here you are reducing cable length to allow the mech to stay more towards the smaller cog and respond faster per click.

Front gear solution

The left hand lever operating the front mech works in much the same way as the right one, but you might experience a slow shift from the small to the larger chainring. If so, unscrew the in-line or downtube-mounted cable adjuster (turn it anticlockwise) an eighth of a turn at a time until it shifts smoothly at the end of the full extent of the lever movement.

Shimano

Low to larger cog

If the shift is slow or the chain doesn’t shift at all, go to the adjuster mounted at the top of the downtube or, if you prefer, the cable adjuster on the rear mech. Unscrew it (anticlockwise when working from the top) an eighth of a turn at a time until you are satisfied that the chain shifts quietly and smoothly. This will add cable length, making the mech more responsive to each click.

Slow to smaller cog

As you might expect, this is the opposite of slow shifts to larger cogs so this time you will need to screw in the adjuster – turning it clockwise – an eighth of a turn at a time (most Shimano adjusters have indents marking an eighth that you can feel as you turn) until you’re happy with the improvement.

This will remove a little cable length, so the mech will move further towards the next smaller sprocket to allow the chain to shift cleanly onto it.

Front gear solution

With the chain on the small chainring, press the left hand STI lever inwards to the full extent of its travel and observe whether the shift from the small to the large chainring is at all hesitant. If it is, unscrew the cable adjuster (anticlockwise) until the front mech carries the chain smoothly and quietly to the larger chainring. This adds length to the cable, making the mech move further towards the large chainring, pushing the chain onto it quickly and smoothly.

Campagnolo

Slow to larger cog

If the chain is slow to shift, use the adjuster at the top of the down-tube or on the rear mech and unscrew it (anticlockwise) an eighth of a turn at a time to increase cable length. Campag rear mech cable adjusters don’t have indents when you turn them so you can get finer adjustments, and they use a simple spring to stop them vibrating loose.

Slow to small cog

If your chain is slow to shift to a smaller cog, or you’ve adjusted the rear mech to improve shifting to the next largest cog and subsequently found this has made the shift to a smaller cog slower than it was before, screw the adjuster inwards (turn it clockwise) a little at a time until the shifting is crisp and smooth again. If it will only set up well in one direction, then it’s time for new cables.

Front gear solution

If the chain is slow to shift to the large chainring, or to the next largest on a triple chainset, unscrew (turn anticlockwise) the cable adjuster at the top of the down-tube until the chain shifts smoothly towards the end of the shift lever travel. As with slow shifts to larger cogs on the cassette, this adds cable length, making the mech move a little faster per shifter click.

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