Left Crank Arm Keeps Coming Loose- What Might Go Wrong?

Bike owners often face multiple issues with their bikes and it’s a regular scenario. Almost everyone, from bike owners to skilled mechanics, seeks guidance on how to fix when the bike crank arm loose.

However, it doesn’t necessitate a professional touch every time. Few problems can be solved by yourself. 

So, how can you fix it when your left crank arm keeps coming loose?

Firstly, check the crank arms if they are properly in place. The crank arm becomes loose because they are wired out. Broken or loosen nuts might be a reason behind this. Lastly, destruction of the bearing causes the situation as well. Troubleshooting & replacing the crank arm can solve the situation.

Did you like the overview? Superb! Then let’s dive into the full troubleshooting segment and solve it now. Sit back tight and hop on!

Troubleshooting Bike Left Arm Loosening

While riding the bike, the crank arms & pedals are put to the highest stress. As a result, a bike crank arm loose would be a typical issue now and then. If you don’t fix it in time your right or left crank arm will keep falling off.

Let’s find out the reason why the crank arm keeps coming loose along with their solutions-

Issue 1: Arm Is Wired Out

You can start checking if the left crank arm is wired out or not. If your bike has spindle bottom brackets, there might be a chance that the spindle will become wired out and the arm will become loose. 

Solution: Repairing the Left Crank Arm

Crank Arm repair and maintenance are critical for preventing losses. You may, however, rely on specialists for this.

However, you might just save the cost of doing it yourself. It’s also enjoyable to maintain your cherished bike on your own.

Make sure the left wobbly crank arm is exactly 180 degrees from the right one. The bolt should then be threaded appropriately. 

Don’t forget to oil the bolt before installing it. As a result, the bolt will not corrode and will remain tight. You can use the Eco Sheep Lube to oil the bolt. It will repel moisture, dirt and grim from the bolt.

Furthermore, this reduces friction between the bolt and the threads. As a result, the likelihood of threads breaking decreases. The process is similar for the right crank arm keeps coming loose too.

This is how to fix the wobbly crank arm.

Issue 2: Is There Any Broken Or Loosen Nuts

The second most commonly seen is in the square taper base brackets; a loosened bolt and fractured treads are connected. Generally, bottom brackets don’t last long. The bolts are hard steel, whereas the crank is soft aluminum. So, the crankshaft bolt keeps coming loose and scrapes against the threads.

The thread is damaged because aluminum is much more flexible than steel. As a result, the bolt becomes loose, and the cycle continues indefinitely.

Solution: Tighten The Nuts

Simply inspect your bike before each ride, tighten any loose bolts, and then ride.

To do that, obtain a pair of Hex Keys and determine which size will fit the bolt.

Anyway, once you’ve found the right tools, secure that arm bolt but just don’t overtighten it.

The Crank Wrench, on the other hand, is interoperable both with nut type and screw type bolts. It should be a perfect fit for the bike arm bolt.

But if you couldn’t repair it anyhow, then you will have to replace it. 

Here’s our recommendation for Hex Keys.

Issue 3: Destruction of The Bearing

 If the bearing mechanism inside the arm is destroyed, the arm skips when paddling. 

As a result, the left pedal arm keeps coming loose.

Solution: Replacing

Unless the bottom bracket gets completely wired out on the threads or spindle, replacement is the only option left. You have to replace it with a new one in this case.

Bottom brackets are available in a variety of styles and sizes. Give it your best shot including doing your research to choose one that is appropriate for your bike. To remove the old bottom bracket, you would need to identify bottom bracket first.

Before you begin, remove the crank arm using a crank wrench. I personally use the following crank wrenches.

You may occasionally observe the thread and spindle if they are in good shape. However, there seems to be a dangling crank arm.

It might happen as a result of a faulty bearing inside of the bottom bracket. You don’t have to replace the entire bottom bracket in that instance. Instead, replace the Bearing System.

We hope following these guidelines you will be able to fix your left crank arm. Even when the bmx crank arm keeps coming loose or the mtb crank arm keeps coming loose, the troubleshooting process will be the same. But still, if you find difficulties repairing or replacing this, you should ask for professional help.

It is preferable to avoid the loosened crank arm than to repair it after it has broken. So you can go for this troubleshooting process.

Grease should be used when setting up a new crank arm for this purpose. Carbon Seatpost grease is very useful for this task. Also, before each ride, inspect and fix your bike.

You can use the following grease in this case.

Crank Arm attachment methods come in a variety of styles. According to the system, you’ll need to have Crank Wrenches or Hex Key.

Before you head out for a ride, make sure your bike is in good working order. Unless the arm nut is far too loose, tighten it and continue.

So these are the possible reasons why your left crank keeps coming loose. Now you know that you will not have to go through a lot of troubles to solve the problem and exercising bike crank arm loose multiple times will make you skilled in this task. You can fix it on your own. 

However, if you can’t find a solution then change the whole crankset. In that case, you can check some of the best crankset.

FAQs

Why would crank bolts easily tear on the left edge?

Crank bolts easily tear on the left edge because of “precession”. This is easier to happen loose than the right. Many crank bolts usually are right-hand threaded on both ends. However, this happens while tightening the bolt on the right-hand side.

How do you repair a crank which won’t turn off?

To repair a crank which won’t turn off, try some form of thread lock solution among the bottom bracket & the crank arm. This is also for ISIS as well as other designs where the driving side crank glides on to a splined pipe wrench.

Why is my crankshaft clinging to the crank arm?

Crankset clinging to the crank arm can be due to movement between both the crank arm as well as the shaft. That shouldn’t be the case, since the two should be so securely joined that there is no room for movement.

What is the function of a crank arm crankset?

The function of a crank arm crankset is quite simple. This contains a square taper crankset with a nut that holds the crank in place.

Wrapping Up

I hope you no longer have any problem regarding the left crank arm keeps coming loose. You can seek professional help if you need it. Don’t forget to share your experience with our solution methods.

Keep the buzz going! See you next time.

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