Bull Busters

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.

Cru­cial setup

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)...

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