Why can't my bike switch to the next chainring?

kernel_kate

My mountain bike is a Dynamo Gauntlet with Shinamo twisters. I showed my bike to a kid, and he twisted the left grip forward. When I attempted to fix it, it got stuck, but when I slowed, it fell back onto the smallest ring. When I attempt to switch the ring, it won't switch, and instead will make a grinding-ish sound. I tried using AI, and it recommended I 'resync' the bike. I tried that, but yet , nothing happened. It's weird.. and I don't know...

Originally asked by GL1TCH0UT on Stack Exchange (bicycles) (CC BY-SA 4.0).

uphilltech

Great question — answering as the UphillTech team:

Shimano brand twist shifters/grip shifters are known for being cheap and nasty garbage. Shimano have always had "budget" parts like tourney for getting people onto a bike, but theres always been a higher grade of part which works the same but better. If your shifter just moves without positive detents then it may have failed internally. There isn't a good Shimano twist shifter. They're all crap. So it wasn't till I was given a bike with a sram shifter that I learned they CAN be good. The best (relatively) cheap upgrade for your bike might be some trigger shifters, with the same number of positions as your bike has gears (ie the left hand shifter for the front should have 3 positions,...

Full answer by Criggie: https://bicycles.stackexchange.com/a/100556 (CC BY-SA 4.0).

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