Smaller flared handlebars, shifters knocked in, skin suits instead of typical jerseys, and 3D-printed aero bike-computer mounts. For professional cyclists, the devil is in the detail when it comes to extracting every millisecond of aerodynamic advantage.
One of the most common traits we see in a professional’s bike setup is slamming the stem.
Slammed stems are something I’m often asked about in my work as a professional bike fitter, and have also experimented with in my setups as a competitive ultra-endurance cyclist.
Many cycling enthusiasts see the professionals slamming stems and assume it’s a straightforward speed hack. If Jonas Vingegaard and co. are doing it, then surely it’s a good idea?
You might reconsider after reading this article! We’ll be covering:
- What Is A Slammed Stem?
- How Do You Slam A Stem?
- What Are The Advantages Of Slamming The Stem?
- What Are The Disadvantages Of Slamming The Stem?
- Should You Slam Your Bike Stem?
- Robbie’s Video Guide: Everything You Need To Know About Slamming the Stem
Let’s dive in!
What Is A Slammed Stem?
A “slammed stem” on a bike refers to the positioning of the bike’s handlebar stem, which connects the handlebars to the fork’s steerer tube.
When the stem is “slammed,” it means that it is positioned as low as possible on the steerer tube without any spacers underneath it.
This results in the handlebars being positioned lower, giving the rider a more aerodynamic and aggressive riding position.
Slamming the stem is a common practice in road cycling and some types of competitive cycling, as it can help reduce wind resistance and change the bike’s handling characteristics.
Slammed stems are sometimes paired with a downward-angled stem to lower the handlebars even further. This makes an incredibly aggressive position for the rider, making them very aerodynamic.
How Do You Slam A Stem?
Slamming a stem is easy to do yourself. All you’ll need is a set of Allen keys and a torque wrench.
However, we strongly recommend leaving any cutting down until later to make sure you’re happy with the slammed stem position.
Step #1. Remove The Stem
Unscrew the bolt on the top cap (the small disc at the top of the steerer tube). Remove the top cap and place it safely to one side.
Next, unscrew the bolts securing the stem to the steerer tube. You don’t need to unscrew them all the way, just until the stem is loose enough to slide upwards off the steerer tube. The handlebars will come with it.
Finally, remove any additional spacers that were below the stem.
Step #2. Flip the Stem (Optional)
If your stem was angled upwards and you want to flip it for an even lower handlebar position, you can do so now.
Remove the stem faceplate bolts which secure the handlebars to the stem. Turn the stem upside down, then reattach the handlebars with the faceplate, paying attention to the recommended torque.
Take care to tighten each bolt a small amount at a time. Stem faceplate bolts have been known to shear under uneven loads, resulting in a potentially serious crash.
Step #3. Re-install Stem, Spacers, And Top Cap
Now, slide the stem back onto the fork’s steerer tube, but don’t tighten the bolts securing it yet. Assuming you’re not planning on cutting the steerer tube at this point, you’ll then need to re-install the spacers above the spacer.
Finally, re-install the top cap, and tighten it up appropriately. If the headset indicates a torque range, follow it.
If not, a quick way of gauging appropriate top cap tightness is to hold the front brake on and gently rocking the bike back and forth. If it feels a little clunky, there’s play in the head tube, and the top cap needs to be slightly tighter.
Be cautious not to over-tighten, however. If you’re having to put much force into the Allen key to turn the bolt, the chances are it’s too tight already.
Step #4. Align And Tighten Stem
Finally, straighten the stem so that the handlebars are aligned correctly with the front wheel, and then tighten the bolts on the rear of the stem back up to the correct torque using the torque wrench.
You now have a slammed stem!
Should I Cut Down The Steerer Tube?
Some people choose not to re-install the spacers above the stem and cut the fork’s steerer tube down to size instead.
A tall pile of spacers above the stem certainly looks goofy, and there’s an argument that it could pose a hazard in a crash.
However, once you cut the steerer tube, there’s no way of un-cutting it.
We’d suggest going for a test ride somewhere safe (an indoor turbo trainer would be best of all) where you’re very unlikely to be involved in a crash to test how the slammed stem feels first, before doing anything drastic.
What Are The Advantages Of Slamming The Stem?
There are undeniably a lot of advantages to a slammed stem. Professional cyclists are no fools – they’d only ride like this if there was a good reason for it.
Improved Aerodynamics
Lower handlebars force the cyclist into a lower position on the bike, reducing their frontal surface area.
This is by far the biggest reason why professional cyclists slam their stems.
You might think this would only make a small amount of difference, but scientific studies have shown that at professional speeds, aerodynamic drag can represent as much as 90% of the resistance slowing them down.
Even relatively small efficiency increases can be enough to smash some personal bests and get you to the cafe quicker than your cycling mates!
Improved Handling At Speed
Slamming a bike stem lowers your center of gravity and moves it further forwards, especially when riding with your hands in the drops. This can make the bike’s handling feel more stable.
This can make descending much easier, and it also can really help reduce speed wobbles from crossing winds or passing lorries and cars.
When you see professionals descending, they are always in the drops because it is safer, faster, easier to control the bike, and gives them more leverage on the brakes.
Looks Awesome
There’s no denying that a bike with a slammed stem looks cool.
It’s aggressive, it’s sporty, and when parked up at a cafe, it looks like a professional is inside having a coffee. If you want your bike to look sweet on Instagram, a slammed stem goes a long way.
What Are The Disadvantages Of Slamming The Stem?
So the advantages of a slammed stem sound amazing, don’t they?
Well, before you get the tools out and slam that stem, it’s important to understand the disadvantages too.
Say Goodbye To Comfort
You can say goodbye to comfort when it comes to slamming your stem.
Although the position is incredibly effective for aerodynamics, it’s not the same story for your back. For any ride longer than 45 minutes, there’s a very strong chance you’ll be in a lot of discomfort by the end.
If you’re wondering how professional cyclists get away with that position for longer rides, it is because it is heavily trained and they are very flexible. For a cyclist who trains a few times a week, it’s very difficult to make the adaptation to the body.
With amateur cyclists I have provided bike fittings for who previously favored slamming the stem, I’ve observed them riding with their hands on the brake hoods or handlebar tops more often than the drops, simply because it’s too uncomfortable for them to get so low.
Over time, this actually means that the slammed stem is giving them a higher average riding position on average, reversing any of the benefits of slamming the stem in the first place.
Potential Loss In Power
Although you gain speed through aerodynamics, I have seen cyclists I have worked with experience a reduction in power output after slamming the stem.
This is because it changes the bike’s fit, and suddenly, the body is out of alignment for pedaling.
The hips are tighter, the glutes are stretched, the core has to work harder, and the quads are more compressed.
This change doesn’t always give you more power, but it can take it away and put extra stress on the muscles where you don’t need it, reducing pedaling efficiency and potentially causing injury.
Reduced Breathing Capacity
A slammed stem may make you quicker and slice through the wind better, but it can affect breathing negatively.
Being in such an aggressive position can constrict the chest and restricts breathing.
If you can’t get oxygen to the muscles, then they are not able to work as they should. This leads to another loss in power, and it can spike the heart rate higher, making it feel even worse to ride.
Twitchy Handling
The handling can improve with a slammed stem by lowering your body weight to the ground, but that doesn’t always work how you want it to.
Every cyclist is different, and what feels responsive to one rider may feel very twitchy to another.
On longer endurance rides, you wouldn’t want twitchy handling on all the corners. You need it to be a little slower and more controlled.
For a professional, the extra responsiveness could be advantageous while racing, but for a day-to-day cyclist, it can be counterproductive.
Should You Slam Your Bike Stem?
As an experienced cyclist and bike fitter who has experimented extensively with slamming a stem, I personally would not recommend a slammed stem to the vast majority or riders.
The key exception would be for professional riders capable of holding the position for extended periods without increased risk of injury or performance losses, or for very short criterium races.
There’s a chance a slammed stem will give you some extra speed through aerodynamics. However, for the majority of cyclists, this advantage is not enough to compensate for the vast range of drawbacks.
Expect a loss of comfort and potentially twitchy handling. You’ll compromise your bike fit, and it can take away your power.
Think hard about what you want to achieve from your cycling experience before slamming that stem!
Robbie’s Video Guide: Everything You Need To Know About Slamming the Stem
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