Changing the stem length of a mountain bike changes the centre of gravity on the cycle. And its ride characteristics. A short stem will give you more confidence and sensitivity when descending. The long stem places your body weight forward. Allows a better climbing position for more pedalling power. And helps prevent the front wheel from lifting during steep climbs.
Over the years, mountain bike geometry and design have evolved. Many types of mountain bikes have seen a trend towards shorter and shorter stems.
It is especially evident with trail bikes. An increasing capable and growing segment of mountain biking.
Bikes are more extended and looser. With wider bars and shorter stems – but why is that, and does a longer stem still have a place these days?
What is a wheel stem?
At a basic level, a stem has a simple job: to connect your handlebars to the fork tube and, with it, the rest of the bike.
At one end (closest to the rider if they’re sitting on the bike). The stem has a hole through it from top to bottom with clamping screws that attach it to your bike’s steerer tube. Here, the branch holds the post in place in the headset.
At the other end of the stem is usually a face plate connected to four screws. Two at the top and two at the bottom, that hold the handlebars in place.
Between the stem face plate and the steerer tube. The stem made of aluminium or carbon fibre, although titanium is occasionally used.
Stem length can have a significant effect on the fit and handling of your bike. There is also usually a slight angle between the handlebar clamp and the long axis of the stem. We will explain the meaning of both later.
These are the basics, but as with all bike parts, there are exceptions and complications.
Short Stem vs Long Stem:
Walk into any bike shop, and you’ll find that short stems are now commonplace. With 50mm stems and often below the standard offering on a trail bike.
In some context, in years past, there would have been XC bikes with 80-120mm stems. And downhill bikes with diameters of 40mm and under.
These days trail/enduro bikes have become super capable. They can climb well and still go down some pretty rugged trails quickly.
One of the reasons they have evolved into such capable machines. Which are the combination of wider bars and shorter stems.
It provides excellent stability and control. When descending, thanks to more torque. When turning the bars and a more direct response from the shorter stem.
It is common to find trail bikes ridden with 800mm wide bars and a 30-40mm stem. Due to these favourable characteristics about aggressive trail riding. Descents and elements such as jumps and drops.
Jump back on an older bike with very narrow handlebars and a long stem. And it feels incredibly jerky and a lot less confident on the descents.
Some XC riders have backed away from some stem lengths and tried running wider bars. Yet, most dedicated XC riders are still running noticeably longer stems. Than most casual mountain bikers who are more into the local trail network or bike park.
The main reason is shifting the weight. On the bike slightly forward ensures that the front wheel stays on the trail. When climbing, the rider sits in the perfect position. To maximize their pedalling power.
Of course, this makes a big difference. If you’re primarily interested in riding long trail runs and gruelling climbs.
Yet, for most mountain bikers. Myself included, climbing is very often just a necessary evil to get to the part I enjoy the most, the descent!
So for me and many other mountain bikers. I much prefer to hit the trails with 800mm bars and a 50mm stem. And deal with an imperfect climbing position in favour of the epic fun I know I’ll have once I reach the top of the trail.
50mm is no longer considered a short stem. Maybe I should try the 35mm one for the next upgrade to see how it feels on the bike.
Does it only affect climb vs descent?
Not at all.
But it’s undoubtedly one of the most noticeable bike-handling changes. Since the stem length change.
The shorter stem gives the bike a more responsive feel on the trail. And is suitable for aggressive riding.
When jumping your bike or hitting drops. A shorter stem puts you in a better position to confidently hit those features. (which often have painful consequences if we don’t ride them well).
Should I replace the stem with a shorter one?
If you prefer to drop and hit jumps and run with a stem longer than 50mm. I’d recommend trying something 50mm or less, you’ll love it.
You’ve probably noticed by now that I prefer shorter stems – and that’s true.
But I’m also not one to blindly follow trends and buy the latest bikes every season.
Many riders find a 50mm stem too long and would have switched to a 35 or 40mm stem years ago.
But then I’ve been riding my Bronson since late 2013, shortly after it was first released.
Since then, there have been many years of bike technology. Improvements and many marketing cycles.
I don’t think we need to keep buying every new thing that comes out. (and yes, the bike industry is fantastic at changing the “standards” regularly).
At the end of the day, if we have a capable mountain bike and a love for the sport. That’s enough to get us out there and have a fantastic bike experience.
At first glance, the stem may seem fairly mundane. Albeit necessary part of the bike that connects the fork to the handlebars. But, the branch significantly affects your bike’s geometry and, as a result. Your handling and your riding position.
There’s a lot to consider when replacing or upgrading a stem. From its length and angle to the material. It made from and compatible with your handlebars and stem.
With that in mind, here’s everything you need to know about bike stems. You can also use the links below to go to the relevant section.