Shimano 21 Speed bikes are excellent mountain bikes, with a variety of speeds and gears. The rear and cogs on these bikes are the basis of the speed levels of this bike, but to make the gears work, a proper adjustment with the derailleur cable is required. Each gear of the bike relies heavily on the derailleur provided by the Shimano bicycle.


If you don’t want to waste money on adjusting the gears to your desired speed, you can simply follow these steps and do it on your own with the help of a 5-millimetter Allen wrench, and a needle nose plier.


  1. Adjust the rear derailleur first by using the wrench to loosen the anchor bolts. Ensure your bolt is loosened to proceed with the next step.


  1. Pull the cable of the bike through the anchor, until it is tight.


  1. Now, tighten the anchor bolt.


  1. Adjust the front derailleur by changing the front gears of the bike, and bring them to the lowest gear. To do this, shift the largest rear cog, and then move on the the smallest front chain ring. This will make the chain be in the inner gear combination.


  1. Next, adjust the front derailleur the same way you adjusted the rear ones.


  1. Use the needle nose plier to pull an end of the cable tight, and then tighten the anchor bolt.