MYTH: DO QUICKSHIFTERS KNACKER GEARBOXES? Once the preserve of the racing elite, quickshifters are now standard kit on many new road bikes. But do these race-derived gizmos come with a hidden cost?
A quickshifter allows the rider to change up the gearbox without needing to pull in the clutch, keeping the throttle pinned the whole time. Most quickshifters sense the rider’s toe pressure on the gear lever, then, at the appropriate moment send a signal to cut the engine’s power for the exact length of time required to unload the gearbox and allow the selected gear to engage. Mechanical sympathy The time needed for most bike gearboxes to disengage one gear and engage the next is around 1/30th to 1/10th of a second. Just a fraction of the time it takes a rider to pull the clutch, roll the throttle, release the clutch, etc. etc. By cutting the engine’s power for only as long as required, quickshifter equipped bikes are able to stay on the power for longer and gain an acceleration advantage. However, compared to using the clutch, a quickshifter gear change can be quite an unsympathetic procedure for a gearbox.
All gearboxes need a specific amount of time to execute a gear change, not only that, each gear will need its own specific time interval. Crucially, quickshifters must be calibrated to the gearbox and ideally to the gear that’s about to be selected: If engine power isn’t cut for long enough during a shift, the gear will either fail to fully engage and ‘bounce’ out, or miss entirely.
If engine power is cut for too long, the whole drive train will be subject to excessive loading as the engine slows the bike down, then chimes back in again. The consequence in the first instance is worn or chipped gear dogs and selector fork/drum damage.
The second scenario leads to increased wear throughout the whole driveline – clutch, gearbox, final drive etc.
Time to kill
Factory fitted systems are already calibrated to the bike’s gearbox and adjustment, where offered, should only provide enough range to allow for fine tuning. Aftermarket systems need to offer a wider adjustment range of engine ‘kill’ times though and this is where problems can arise. Ideally, bolt-on quickshifters should be model specific, or have pre-established, model specific proven kill times that can be used as a safe starting point during set up.
Engine kill times should be specific to each gear, to achieve this quickshifter systems need to monitor which gear the ’box has selected. As lower gear ratios are invariably spaced wider apart than higher ratios, kill times should be longer for shifts up through the lower gears.
Also, the shift from first to second passes through neutral and this extra selector travel will need to be accounted for in the quickshifter’s set up.
It is crucial to ensure a quickshifter is set up correctly. But without any ballpark default settings, the process of calibrating a quickshifter probably isn’t the best thing you can do to a gearbox. Although done sympathetically, finding optimal engine kill times shouldn’t inflict appreciable damage to a ’box. Once smooth shift settings have been found, using a quickshifter shouldn’t pose a significant health hazard to a gearbox or any part of a bike’s drive train. A poorly set up quickshifter however, will most certainly cause gearbox issues down the line.
In the end, gearboxes can be damaged by poor shifting regardless of how the gear change is facilitated, be it by a quickshifter, momentary rolling off the throttle or by declutching. If the gearbox isn’t properly unloaded for enough time to accomplish the shift, or if the gear lever receives too much or too little force, dog, dog ring or selector mechanisms can sustain damage.
Once you’ve tried one, you’ll struggle to live without the awesomeness of a quickshifter.
Dodgy dogs will cause missed gears and potential pain.
This trick Nova gearbox will assure you of gear changing nirvana.
All the gear(s)...