Your mountain bike stem is what connects your handlebars to the top of your fork.
Chances are you’ve never thought about your stem, or you’ve wanted to replace it but didn’t know the right size.
Changing the stem length on your bike can dramatically alter your ride. Today, we will look at how stem length affects your riding and what size you should consider.
Mountain Bike Stems Explained
A mountain bike stem attaches to the top part of your fork, the steerer tube, that sticks through your frame and then connects to your handlebars.
It is a vital part of your cockpit.
Stems come in a variety of lengths ranging anywhere from 35mm up to 100+ mm. This measurement refers to the distance between your fork and your handlebars. It is measured from the center of your top cap to the center of your handlebars.
They also come in different clamp diameters, with 31.8mm and 35mm being the most common size. This diameter refers to how wide the clamp is that attaches to your handlebars. For your stem to fit properly, you need to match the clamp diameter with the width of your handlebar.
(When was the last time you replaced your grips? Check out these 8 different grips and freshen up your bike.)
How Short and Long Stems Affect Your Ride
The length of your stem affects how far away your handlebars are from the center or your fork. This affects your riding position and ultimately your weight distribution between for front and rear wheel.
Long Stems
A long stem (50+ mm) pushes your handlebars further away from your fork and over the front wheel. This brings your weight further forward on your bike, weighting the front wheel, making it easier to go up steep climbs but reducing stability at high speeds and descending.
Long stems are typically seen on cross-country mountain bikes and road bikes. They are great for pedaling long distances and climbing hills.
Short Stems
A shorter stem (< 40mm) will bring your handlebars closer to your fork. This will keep your weight behind or even with the front wheel. These stems put you in a neutral position and make it easier to go downhill. Shorter stems are ideal for trail riding, aggressive enduro riding, and downhill riding.
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What Stem Size Do You Need?
A quick disclaimer. I am a bike nerd, and these are all my personal opinions.
Keep in mind that when you buy a bike, the engineers choose the stem it comes with. It’s what they think works best with the bike. Furthermore, everyone has different bodies. What works for you might not work for your buddy. It takes some trial and error to find out what’s right.
Trail Bikes
The typical mountain biker should use a 40mm stem. This is the best size for trail riding.
This length will put you in a neutral position on the bike that is good for both climbing and descending.
Don’t just take my word for it though, Jesse Melamed, a pro Enduro World Series racer, mentioned on this episode of The Downtime Podcast (32:35 minutes in) that he believes everyone should use a 40mm stem.
I recommend the Race Face Turbine R, Chromag HiFi V2, and the Industry Nine A35 stem for this discipline. They all come in various colors, so you’re bound to find one that fits your style.
Enduro Mountain Bikes
On an enduro mountain bike, use either a 35mm or 40mm stem.
This is typically the size that comes stock on most enduro bikes.
You’ll notice this is very similar to my trail riding recommendation. However, since enduro bikes typically have a longer reach, you can use a shorter stem.
This shorter stem will keep you behind the front wheel when you are inevitably descending rowdy terrain on your enduro bruiser.
I recommend the Spank Spoon, Race Face Atlas, and the Chromag BZA stems for enduro riding.
Cross-Country Mountain Bikes
On a cross-country mountain bike, use a stem between 50mm and 100mm.
This will pull your weight onto the front wheel. It’ll put you in a very aggressive stance that is great for climbing and reducing wind drag.
However, you will feel like your weight is over the front wheel when going downhill. If you don’t like this feeling go to a shorter stem, but if you’re all about the speed, stay with that extra length.
For cross country stems, I recommend the Specialized Comp Multi, ProTaper ATAC, Ritchey WCS Carbon Matrix C220 stems.
The Bike Fitter
While a small part of your bike, the stem plays a large role in how your bike fits.
Too short, and you’ll find yourself off the back wheel, pushing your front wheel in corners. Too long, and you’ll be hesitant to bomb those steep descents.
This is where a bike fitter comes in.
If you want to get the most out of your bike, I recommend you go to a bike fitter. You’ll find these professionals at your local shop. They’ll help you adjust your bike so it fits you perfectly.
But whether you head to a bike fitter or do it yourself, start thinking critically about your stem. Is it the right size for you and your discipline of riding?
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