Common crank arm problems: how to solve them

After purchasing my new mountain bike in February of 2016 (upgrading my original bike from 2005) I started having problems with the crank arms on a much more expensive bike.

This got me researching about crank arm problems to see if my bike was a dud or if it was a common problem.

What are the typical crank arm problems? The most common problems are noise caused by the crank arms and the crank arms working themselves loose. Some of the crazy problems are caused by installing cheap pedals, installing pedals incorrectly or crashing hard enough to bend your crank arms.

First, let’s start off with some basic education for the beginners out there. The crank arms are part of the crankset which is the main connection between the rider and the bike.

There is a non-drive side crank arm and then the drive side which consists of the crank arm, chainrings (1-3 depending on the type of bike), spider, and spindle.

The spindle works like an axle that cycles through the bottom bracket which is in the frame of the bike.

As there are many components it may seem daunting to fix and there is no shame in taking your ride to your local bike shop (LBS) to have them tackle it for you.

If you are ready to take a look at the tools you will need to tackle these common problems, check them out here.

Common Crank Arm Problems

While researching a fix for my main problem I came across multiple forum posts where users were having similar problems so I decided to write this post in an effort to pass along what I learned.

Crank arm works loose.

One of the most common crank arm problems is that the non-drive crank arm can work itself loose.

If you are familiar with the old phrase “righty tighty lefty loosey” or “Time is always tight” then you know what I am getting at here.

When you are tightening bolts (or crank arms) you are doing so in a clockwise direction.

When you are pedaling your bike you are the drive side is turning in a clockwise direction whereas the non-drive side is turning in a counter-clockwise direction.

This motion naturally could be expected to cause some problems here.

It’s a unique situation as it doesn’t happen often but when chatting with my LBS at the time he mentioned seeing more than you would think.

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Noisy Cranks

My initial problem was another one of the most common problems in mountain biking which is simply noise coming from the crank arms.

Not long after getting the new bike we were out on the trail and I noticed a weird noise on the downstroke of the non-drive pedal.

One of the first trails we rode was quite muddy and our mud is basically clay.

The next time we got out it was on the dryer side and I hadn’t really cleaned the bike that well before we got out there.

The pedal was a little loose and clay had worked itself between the crank and the bottom bracket.

The fix was a thorough cleaning and a proper torquing of the crank arm. Now, this is one of my must check pre-ride items to ensure it doesn’t happen on the next ride.

It’s not really detrimental to the ride, just more annoying than anything especially after spending a good chunk on the bike.

If you still experience noise after good cleaning and tightening of the crank arm then you might have an issue with the bottom bracket instead.

If you are in need of some tools a nice option is the Bikehand Bike Bicycle Repair Tool Kit with Torque Wrench found on Amazon.

Crazy Crank Arm Problems

Buyer beware!!! As things go there is a general change in schools of thought from time to time.

When I first got into riding back in 05 there was a bit of a movement going away from flats and moving towards riding clip-less pedals as they gave riders extra confidence and helped with the climbs as you were able to take advantage of both the up and down stroke on the pedals.

So I decided to change over to a pair of flats like my buddies and went with one of the least expensive options at least at first to try and see if I would want to ride that way long term.

The item came in, I took off the old pedals, carefully aligned and inserted the new pedals in the crank arms. I made sure everything was tight and ready to go before going for a ride.

All seemed well until my third ride with the new pedals. The night before I was practicing hucking as I discussed in a previous post where I was hucking off a culvert in my front yard.

A couple of landings were on the hard side and there was one crash during this process.

During my final practice ride before our trip out to Brevard, NC for one of our Mountain bike and camping excursions I noticed a weird sensation.

After finishing up the 3-mile loop of one of the local trails I started having problems and looked down at the pedal on the non-drive side of the bike.

Somehow the pedal became loose and almost completely stripped out the threads on the crank arm. I got really lucky that I work near a local bike shop and they were awesome.

The interim solution to my problem was a simple heli-coil that the LBS mechanic was able to get into the crank and I have been riding this way for over a year now without any additional problems.

So I guess its turned into more a permanent option for now anyway. If you are mechanically inclined and have the time to do it you can grab a heli-coil kit from Amazon.

Initial discussion with most local bike shops was to purchase a new crankset because of the nature of my original cranks as they were a Specialized crankset.

No matter which shop I went to we would have to order a new crank arm which wouldn’t be in till after our trip was over.

It was a stressful moment as the getaway weekend was coming up faster than I would be able to return the part.

Another Crazy crank arm problem is when they get torn up pretty bad because of a crash. I’ve seen it happen on another bike and heard from others that had the same problem.

The more and more you get into shredding the trails, the more chances there are for you to try some tougher stuff.

Jumps get bigger, drops get more insane and you get more comfortable on the bike.

That’s when this usually happens. Pushing the bike to its limit as well as the riders and next thing you know a crash with a busted up bike.

The key is to ensure that the fall that bent the crank arm didn’t cause any additional problems.

I would be able to get a new crankset in and inserted but the price of new ones that matched my setup was between the $400-750 range.

Need to replace a crank arm? Here is how to determine what to buy

If you run into a crazy or even a nagging common crank arm problem, there are several things you can do. They all depend on your disposable income though.

It could be that you simply need to grab the right tools and do some maintenance.

Research your bike and crankset to find out just how much torque is needed on the crank arms.

You want to ensure that you get them tightened enough but don’t want to go crazy and tighten them down until you just can’t turn the ratchet anymore.

This could put too much pressure on your bottom bracket and that could be terminal costing you more than just a crank arm.

There are many ways to try and determine this information, the easiest of which should be to just search for the manual for your bike.

Specialized has an online version that you can simply download. Once downloaded go to Appendix D which contains all of their fastener torque specifications.

If your old cranks felt good then you are going to want to look for new ones that are the same size. To measure, simply go from the center of both holes on the crank itself; The hole for the crankset attachment and the hole for the pedal itself.

If you are needing a change then there is more to think about which I will explain in a future post.

Different Crank arm brands

When it comes to cranks you have several things to think about while you try to determine which to choose. The options are Brand, material, sizing, gearing, and cost.

Brands

There is no shortage of brands for cranksets and crank arms. For example, if you go to Jenson USA they have 22 different brands listed in the filters section.

The most recognizable names being Cane Creek, Race Face, Shimano, SRAM, and Surly.

In my case, the Specialized Fuse Expert came with Specialized’s own Stout XC Pro crankset that can only be purchased via the local bike shop that is also a local retailer for the brand.

This made my problem even tougher to fix in the amount of time I had.

Materials

Crank arms come in all kinds of materials; aluminum alloy, titanium, carbon fiber, Chromoly steel. The most expensive of these will be the carbon fiber ones.

Sizing

Most of the brands come with the same sizing and the key here it so gets your measurement correct. If your bike has its original components then you could simply look up the specs in your paperwork on the bike or lookup your bike on the brand’s website.

Gearing

If you end up needing or wanting to get a whole new crankset then you will need to think about gearing. The easiest thing to do is go with your same gearing setup whether it is a 1x, 2x, or 3x.

If you are currently running a different setup there is more to think about before changing from a 1x to a 3x or vise Versa.

Cost

This is the easiest and hardest part of choosing what to purchase. Initial thoughts are usually what would be easiest on the wallet but as you get more into the sport you are always looking to get more out of your components.