This black aluminum left crank arm is 172.5 mm in length, with a hollowtech II spindle interface. The left crank arm is used to position the arm up against the bearings in the frame. Tightening the end cap on the left side pulls the crank onto the spindle and up against these bearings. The left arm pinch bolts are then tightened to secure the crank and maintain the adjustment. There are a few things that can go wrong with a left crank, including the threads for the pedal getting stripped or damaged causing the pedal to come undone easily. The mating hole for the bottom bracket can get damaged so that it is no longer a good fit. This can cause a creaking sound on the power part of the stroke. The arm crank can crack, which can be a result of retightening too many times and the mating hole wearing down. The crank arm can bend due to impact or an accident (this is rare because crank arms are very strong).
For this repair you will need a hex wrench for the pinch bolts, flat screwdriver to lift the stop plate, a mallet for installing the arm, torque wrench for tightening the pinch bolts. You may also require lubrication for the spindles and the end cap.
To remove the crank arm, you will first need to remove the pinch bolts on the left crank. Then loosen and remove the cap on the left arm, pull the left arm off the spindle by hand (sometimes you may be required to lightly tap with a soft mallet), then pull the stop plate off the arm, and finally, remove the crank by pulling to the right and taking it off the bike.
Installation starts by greasing the surfaces of the spindle where it engages with the bearings. Install the spindle through the right side of the bearings and out the left. Sometimes a mallet is needed to gently tap the arm into place. Grease the splines of the spindles. Install the left arm 180 degrees from the right arm. Push the stop plate down over the pinch bolt and ensure that it is fully engaged into the spindle. Grease the threads of the crank cap and thread into the spindle. Tighten the cap in gently. If you over tighten the cap this will push the arms into the bearings, which can cause side-loading, resulting in premature wear of the bearings. Tighten the pinch bolts, alternating between them to make sure they are fully and evenly tightened (this is very important). Tighten to the recommended manufacturer's torque, which is often specified on the crank arm. Tighten one side until it clicks, and then do the same for the opposite side. If the adjustment is too loose, you will notice a side-to-side motion of the spindle in the bearings.
Left Hand Crank Arm Unit 172.5 Y1W898070
OEM part for: Shimano Bicycles
Part Number: Y1W898070
Leaves our warehouse within 7 - 12 business days
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- Classification: Part
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Compatibility
This Left Hand Crank Arm Unit 172.5 will fit the following 1 machine. Confirm this part works with your model, and view the detailed model diagrams and repair help we have to offer.
Shimano Bicycles
This item works with the following types of products:
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