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My son's bike is stuck on 7. When we try to shift down to 1, there are no clicks. It just shoots right back to 7. This is a dial/twist/grip shifter, not a trigger shifter. I do not think it has anything to do with the derailleur, but want to confirm.

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    From my work reconditioning used bikes for charity, I know that twist shifters are just about the least reliable part of a bike. They have several failure modes, but the most common is for the detent spring (a little strip of oddly bent metal) inside to bend or dislocate. Sometimes the spring just falls out. – Daniel R Hicks Jun 22 '15 at 1:57
  • Indeed, you should buy a new shifter. – Batman Jun 22 '15 at 2:31
  • That's funny. Many of the winter riders up here still swear by grip shift. The thought or belief being that since they are hand powered both ways, they have a higher reliability rating in the severe cold. – Deleted User Jun 22 '15 at 16:05
  • @ChrisinAK - When they work they work. When they stop working (which is frequent) they're trash. – Daniel R Hicks Jun 22 '15 at 16:35
  • It's probably like anything else. I know a few guys with the high end SRAM sets that have finished the Iditarod Trail Invitational multiple times. Including a couple of record runs. – Deleted User Jun 22 '15 at 16:42
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Without the shifter's resistance, the rear derailleur pulls towards the smallest cog (highest gear). This would also happen, e.g., when the shift cable snaps. (Rarer 'inverse' derailleurs would pull towards the largest cog.) To test the rear derailleur, pull the shift cable with your hand while turning the crank; if the derailleur moves and pushes the chain towards the biggest cog, it means the derailleur is ok.

If the (indexed) shifter doesn't click anymore, or if the internal catch doesn't seem to withstand the pull of the derailleur, it's most probably time to overhaul or replace the shifter.

It may simply be that old grease in the shifter has hardened up over time, so that the catch mechanism is stuck. This should be mendable if you open a cap of the shifter casing until a hole is revealed (used for threading in the cable), and spray in a generous amount of a light lubricant that will solve and flush out the sticky grease. WD40 is known to work quickly in such a job, but others also work well and may have better lubricating properties than WD40.

If lubricating doesn't help, it's possible that some internal part is worn out or broken and needs to be replaced. If spare parts are not readily available, it's a case for complete replacement.

  • Twist shifters don't contain grease that can harden and make things stick. – Daniel R Hicks Jun 22 '15 at 11:15

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