Will Mountain Bike Pedals Fit Road Bike Cranks Arms? We Find Out!

Looking to change up the feel of your road bike? Changing the pedals from clipless (standard on most road bikes) to a hybrid or even flat style, as one might expect on a mountain bike, could be just the change you need. But will mountain bike pedals fit road bike cranks arms?

Whether mountain bikes or road bikes, all modern adult bicycles come with a standard 9/16” thread pedal and crank arm. Due to the standardization, you can easily swap mountain bike pedals for your clipless road bike pedals. Mountain bike pedals will fit road bike crank arms.

Let’s dive a bit deeper into the marriage between the pedal and crank arm for your mountain or road bike. I’ll share my trick to double-check the thread count and measure to make sure the pedal will work before I try threading it in (I don’t want to cross-thread and wreck the parts). By the end of this article, you’ll also have some tips to make your life a whole lot easier when you’re changing out pedals on either your mountain bike or road bike.

Will Mountain Bike Pedals Fit Road Bike Crank Arms And Vice Versa?

As I mentioned, the pedal standard size is 9/16-20 thread. It is the universal standard, so all new bikes in Europe, North America, and elsewhere should be adhering to this size. The standardization is included in both the mountain bike and road bike worlds, as well as most other bicycle types as well, save for very small and cheap children’s bikes that often use the ½” threaded pedals instead. You can tell the difference because side to side the ½” is smaller. A 9/16” pedal will not work in a ½” pedal crank arm. But unless you are riding a bike with 10” wheels, you aren’t likely to face this issue.

If you want to see a bunch of universal pedals, take a look at my article showcasing some of my favorite 9/16” pedals for mountain biking.

What Does 9/16-20 Mean?

Okay, so maybe I’ve glazed over something that I know that you might not. If you already know, then just skip ahead, but for those of you who don’t, let’s talk about what 9/16-20 means.

First, the pedal threads into the crank arm, so we want to know what diameter that threaded ‘bolt’ on the pedal is. It is where the 9/16” comes into play. 9/16” is the diameter of the threaded portion of the pedal shaft. Subsequently, it is also the diameter of the threaded hole in the crank arm.

If we know its diameter, that should be enough, right? Wrong. We need to know one more thing – how big are each thread in the threaded section.

You must have seen the difference between a wood screw and a machine bolt in your life. If you recall, a screw has very wide threads meant to grasp the material it is passing into. On the other hand, a bolt has finer threads, meant to marry with a nut (or threaded hole, such as in the case of the crank arm). And we also know that there are two forms of measurement used in the world – Imperial and Metric.

Now, we know that the pedal uses imperial because of the 9/16” diameter. However, we need to know the thread size next because many sizes are possible, even within Imperial measurements.

The number following the dash tells us the size of the thread. As it is referred to, the thread count is the number of threads per one imperial inch. In this case, the thread count is 20. Therefore, there are 20 threads per inch along the length of the threaded pedal. Now we know that one thread is 0.05” wide.

You’re probably thinking, how on Earth am I going to measure 0.05” to confirm the thread size? Don’t worry; it’s universal for bike pedals, so you don’t have to. If you want to confirm the size yourself, then all you need to do is measure one inch and count the number of threads within that measurement. That’s it – thread count.

3 Tips to Swapping Pedals

You might think that swapping pedals is a piece of cake. Then again, you might have tried it and found it exceedingly difficult at first. Many would-be pedal swappers run into a very simple problem when attempting to change pedals – physics!

Remember that the crank arm spins around. Trying to use a wrench to rotate a pedal loose can be quite the hassle if you don’t have your physics in order. To help you, here are a few tips I have that helped me become a pedal-swapping expert.

1. Don’t Stretch Your Chain
2. Get A Real Pedal Wrench
3. Use The Triangle

Don’t Stretch Your Chain

Never try to block the movement of your crank arm by using the chain or any other means. I’ve seen riders try to change out a pedal and wind up snapping their chain because they didn’t use a simple trick with geometry (don’t worry, I’m going to share). If you do the repair right, you’ll never need to worry about the crankset rotating. In fact, you might even use it to your advantage (see my pedal threading tip below).

Get A Real Pedal Wrench

So if there is one thing you should have that is good and strong and of proper length, it’s a decent pedal wrench. Sure, you can use a normal wrench, but there are often issues with a normal wrench thickness, jamming between pedal and crank arm before the pedal is fully tight. That’s why a thin yet strong pedal wrench is a worthwhile investment.

Use The Triangle

Image courtesy of Shutterstock, modified by Farm 6 Media.

Referring to physics earlier (most cringe at the word), I referred to a particular geometry that makes changing pedals easier than one might think – the triangle.

When many try to change pedals for the first, second, or even a third time, many will struggle with the rotating crank assembly and try to find ways to lock it in place. It is a futile and unneeded act. All you need to do is create a triangle. Let me explain.

Let’s say you are trying to take off the right-hand pedal.

1. You need to put your bike up on your Bikehand Repair Stand, or if you have a kickstand, you can even do this with the bike on the floor.
2. Align the right-hand crank arm, so it is horizontal and pointing forward.
3. Set up your pedal wrench so it is on the boxed part of the pedal shaft but above it, pointing the handle back and upwards at about a 30-degree angle. The crank arm at horizontal, and the pedal wrench coming up and back off the pedal shaft forms two sides of our triangle.
4. The third side of our triangle is the direction of the force you will apply to loosen the pedal. By following the line of the triangle with your direction of force and using a pedal wrench that is longer than the crank arm length and the job now becomes much more straightforward. Merely steady the pedal in one hand and apply force to the end of the pedal wrench, in the direction of the last side of the triangle, as mentioned. You will find this technique superior to all others for not affecting the chain and not requiring to secure the rotating crankset.

To tighten a pedal, after threading in by hand to ensure no cross-threading, merely reverse the triangle, so the crank arm is pointing backward instead of forwards. Again use the triangle with the pedal wrench above and the direction of force downward.

Pedal Threading Tip: Start your pedal threading in by hand. Get at least a full turn-in, so you know the thread is meshing nicely. Next, place your pedal wrench on the squared part of the pedal shaft and, holding the wrench, backpedal the crankset. This movement will continue to thread in the pedal into the crankset until tighter, so you can use the triangle technique to torque the final bit of tightness.

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