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| *Vultures Knob>>>Mountain Bike |
Why do my mountain bike gears keep changing automatically? I have a Trek 4500.? |
When I go uphill, sometimes the gears change when I don't even shift. It makes a loud sound like it is breaking the teeth off the gears. It's a new bike... Could be a couple of reasons... 1) If you get your bike dirty regularly, the cable may be sticking; 2) The derailleur hanger may be out of alignment (assuming it is the rear derailleur that changes) or loose; 3) The frame dropouts may be out of alignment; 4) The derailleur may be bent; 5) The chain may be bent or have a stiff link In any case, take it back to your dealer and have them look at it. Source(s): 27 years in the industry Your derailleurs are not adjusted properly. Under high loads, such as climbing, will show any misalignment. Under light loading this might only show up as slow shifting. Being a new bike this is not uncommon as the cables stretch and break-in. Take it back to the bike shop and have them re-adjust the cables, also have them check the entire bike as the first 10 hrs of use things will wear in and loosen up. its a derailer issue, probably cable tension. The rear derailuer most likely needs adjusting. New bikes generally has to have to derailuer slightly adjusted due to the new cable being stretch after a few hundred miles or less. If it new take to the place you bought and have them adust it. If not look at where the cable goes into the derailuer. The adjustment is there. Try turning a half turn to the left and see if that helps. It shoudn't take a whole lot of adjustment correct the shifting problem. This is free advice so if it don't work you don't get any money back. Did you fall? If you did and your bike landed on the side of the deraillieur then your bike could have a bent hanger. This often causes ghost shifting and is usually easy to fix or the hanger can be replaced. The part is around twenty bucks, but hopefully your trusty bike mechanic can bend it out for you. I could also be what the other folks said, adjustments of the cables, crud in the chain, too loose a chain, usung gears improperly. |
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