mountain bike gear I have a 20 speed mountain bike with a twist grip gear shifter and my gears are not working right?
When i am in gear 2-5 after pedaling awhile especially when i am standing my gears automatically shift down to 2-6 and then after awhile they will shift to 2-7… im not sure why it is doing this if you no please tell me what it is and if you can how to fix it…im really excellent with bikes so i shouldn’t have to bring it into a shop… thanks

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