Our round-up of the best mountain bike stems in both 31.8mm and 35mm clamp sizes
Mountain bike stems are an important factor when it comes to the control of your mountain bike, but which one should you choose?
It is possible to measure differences in weight between models of stem, and if you’re really in tune with your bike, there are subtle differences in stiffness to evaluate. It’s not easy, but keep all the components the same, and ride the same trail over and over again with different stems, and the nuances begin to become apparent.
Equally, get up close and it becomes obvious which stems are really well thought-out and have the best combination of construction, material choice, geometry and even the fasteners — something that’s important on a component that needs to handle big forces.
Know your mountain bike stems
First job is to work out what stems will actually fit on to your bike. You’ll need to know your forks steerer size and handlebar diameter.
Your fork steerer is almost certainly going to be the usual 1-1/8th” diameter (the other option is 1.5in but it’s very rare these days). Use a tape measure to measure the diameter of your headset top cap and you’ll instantly see if it’s not for a 1-1/8th” fork steerer fork.
Handlebar and stem clamp diameter
Handlebar diameter is a bit less straightforward. Modern era mountain bikes will either have the more-common 31.8mm diameter handlebars or the newer 35mm diameter handlebars. Older bikes may still be sporting skinny 25.4mm diameter handlebars. Again you can use a tape measure to quickly assess what diameter your bike has. You need to get the same stem clamp diameter as your handlebar diameter ie. 31.8mm clamp stem for a 31.8mm diameter handlebar.
4mm and 5mm Allen bolts are most common on mtb stems, with the heavier, larger-diameter bolts typically enabling higher torques and subsequent clamping forces. Cheaper bolts round off more easily, and anodised bolts can lose colour. Stainless steel or titanium bolts maintain looks and are more resistant to corrosion.
The vertical real estate the stem demands on the steerer tube. It can be an issue if your fork steerer is too short, and can also relate to the handlebar height achievable and overall stiffness of the stem.
30mm is about as short as you can go on a standard stem. There are some newer designs – such as Pacenti PDent – that enable even shorter stems but they require specially designed handlebars. Stubby stems are something we’re big advocates of here, since reducing the distance the bar extends beyond the steerer will sharpen the steering response, provided your bike is roomy enough. We recommend fitting the shortest stem you can get away with but bear in mind that some older bikes with short top tubes may end up with cramped reach and compromised bike control, in which case we wouldn’t go shorter than 50mm and we’d also think about fitting wider handlebars as a means of widening your reach and improving balance, control and comfort.
Zero gap fastening
More and more stems are now featuring a zero-gap bar clamp design, whereby one pair of clamp bolts fasten fully, and the remaining bolts tighten to lock the bar in place. The design prevents uneven tensioning and reduces the number of bolts you need to fix to a precise torque setting, making set-up easier.
Rise is the difference in height between the clamps. Most stems are zero-rise, which means if you flip them over they don’t change the bar height. However, a six-degree rise stem allows you to effect a plus or minus six-degree change in bar height by simply turning the stem upside down.
CNC v Forged
Stems are either 3D forged or CNC machined from an aluminium billet (basically a chunk of metal). Forging sees aluminium squeezed under immense pressures into (close to) the stem’s final shape. The technique compresses the material around high stress areas, and it’s argued produces a stiffer product with a better-aligned, denser grain structure. The initial forging cost is expensive and the finish is sometimes less angular, although you do see stems that are forged initially and then tidied up on a CNC machine.
mbr reviews of the best mountain bike stems
All of the following stems are the best mountain bike stems which scored at least 9/10 in our test. Here’s a complete list of all the mountain bike stems we’ve tested.
Syntace Megaforce 2
This impressively stiff stem is 3D-forged, CNC machined and shot-peened. The process goes some way to explain its relatively high price tag. It’s not just stiff, it’s also crisply finished and even has titanium bolts with oversized M6 heads. The stack height is modest and the 6° rise can be flipped if you need a lower bar height. Comes with a 10year warranty too. Impressive is the word.
Truvativ stuff comes from the house of SRAM so its modest price tag is not indicative of lower quality, it’s a mark of bulk manufacturing overheads. Despite its Descendant moniker and its chunky aesthetic, this stem is not overly burly or ungainly. It’s as stiff as anything else here and although the white areas get a bit stained if you’re not careful, the black bolts stay black and corrosion-free. It’s just a bit heavier than some other, flexier, stems out there.
KS are much better known for their excellent dropper seatposts but recently they’ve branched out into cockpit components with handlebars and stems. The glossy finish and sheeny ti bolts give this stem a look and feel of premium goods but thankfully the price tag doesn’t follow suit. The wraparound rear clamp designs will please your kneecaps. One niggle: not very many length options currently.
Race Face Ride
If you’re after a top performing, no-fuss stem then look no further! The Race Face Ride really does fit the bill for a stem perfect for general trail duties. And at under £25 it’s a total steal!
The Crossfire cannot be faulted in performance. Very little flex could be perceived during riding even when hauling on the bars. Setting up was simple and despite running all the bolts dry (sorry!) and riding it in desert conditions it never developed a creak. There are plenty of colours to choose from and it has a style suited to any bike. There are slightly lighter stems out there but the Crossfire is hard to beat on every other factor.
Pacenti PDent system
In terms of pure function, the PDent bar/stem combo is stiff and comfortable with an overall quality that’s reflected in the top-end price. It doesn’t suit shorter bikes with steeper head angles, but on modern trail bikes with slacker geometry, it ultimately requires less effort to control the bike, particularly in the tight stuff.
The best mountain bike stems: verdict
All five of these chosen stems are worthy of your money.
Our favourite, money-no-object, stem for 31.8mm bars is the Syntace Megaforce 2, the main issue might be tracking one down. The same goes for the rare but excellent KS Ether.
The three stems from more mainstream brands are the logical all-round choice: the sorted Funn Crossfire, the solid Truvativ Descendant and the bargain Race Face Ride.
If you want a whole new cockpit for a modern long-reach bike then the Pacenti PDent system really is excellent.