Read our full test review of the Funn Crossfire stem

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DMR Defy 35

A rare short stem with a low stack height

Weight: 174g | Colours: Black, silver | Lengths: 35mm | Rating: 9/10

Pro: Super secure. Raises your front end whilst having low stack height. Good price.

Con: Typically robust weight. Square edge aesthetic may not suit some bikes.

The Defy stem is designed to be perfect match (aesthetically speaking) to DMR’s own Wingbar but has a few features that make it a very attractive package for any cockpit combination.

Twin face plate clamps use a Top-Close clamp design where you tighten both top bolts until they touch the stem body before tightening the lower bolts, ensuring simple, safe and effective bar installation. The two-piece design does make things slightly fiddlier in installation (there are two face plates to keep an eye rather than one) but once installed they do look really cool and very modern.

The 6061 aluminium Defy has a shape that trims down the steerer clamp stack height to create one of lowest on the market. At just 28mm this makes the Defy perfect if you want to play a little more with stem/bar height (and thus you bike’s effective reach distance)  or have a fork with a less than ideal steerer length. We had to add more spacers to take up the excess steerer.

One of the best – and pretty unique – aspects of the Defy stem is that it’s a stubby 35mm length stem that also packs in a bit of rise (at least 5mm), which is really handy if you want to raise your bar height without resorting to stem spacers or a new handlebar.

Sure, this stem is not going to win any weight weenie competitions but it’s crisply made, stiff as heck, offers a rare bit of rise for a dinky stem and, always importantly, has plenty of style whilst doing so.

Read our full test review of the DMR Defy 35 stem

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Deity Copperhead

Great low-stack option

Weight: 142g | Colours: Eight | Lengths: 35 or 50mm | Rating: 9/10

Pros: Great attention to detail

Cons: On the expensive side

What does “low-stack” mean you ask? It’s how much vertical space the stem takes up around your fork steerer. If a stem has low-stack height it can be a lifesaver in situations where the fork steerer has been trimmed down and there isn’t much real estate to fit a stem on there. In this regard it’s similar to the DMR Defy stem (above) but without the rise.

Although the Copperhead is CNC’d from 6061 T6 aluminium and not cold-forged (which tends to be the construction method that results int he stiffest stems) it is nevertheless still impressively stiff. We attribute this stiffness to the relatively broad face plate with its 55mm width.

Although the price is not exactly budget basement, there is a level of quality and thought gone into the Copperhead stem that is well worth the money. For example, the bolts have deep-set recesses for Allen keys and this really does help prevent the bolts being rounded or otherwise damaged by ropey multi-tools or inattentive and rushed mechanic-ing (we’ve all been there).

Read our full test review of the Deity Copperhead

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Burgtec Enduro MK3

Available in ‘Goldilocks’ 42.5mm length

Weight: 155g | Colours: Nine | Lengths: 35, 42.5 and 50mm | Rating: 8/10

Pros: Unique length offering

Cons: Split front clamps are fiddly to install

Taking our reviewer’s hat off, there really isn’t anything to complain about with the latest Burgtec Enduro stem. Yes, the two piece front clamp design is fiddly but, for heaven’s sake, how often do you actually install/remove a stem in the real world? It’s totally live-with-able. And there will be some riders who like the resulting window for their handlebar decals to be displayed through.

For this, their third version of their Enduro stem, Burgtec have switched to a cold-forging construction method. This has really upped the stiffness quotient of the stem compared to the previous Enduro MK2 stem. The bar clamping width has also been increased. So too has the steerer clamp depth, which has resulted in a greater stack height so this may no longer be a viable option for riders with cut-short fork steerers.

Perhaps the main USP of the Burgtec Enduro MK3 is that is available in a 42.5mm length. It may sound daft and all rather Princess-and-the-pea but a couple of mm here on there with stems can certainly be felt by experienced riders. So if you’ve tried 40mm and 45mm stems and not quite gelled with them, here’s the (42.5mm length) stem for you!

Read our full test review of the Burgtec Enduro MK3

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Renthal Apex

Available in 31mm length

Weight: 110g | Colours: Black & gold | Lengths: 31, 33, 30, 40, 50, 60, 70, 80 and 90mm | Rating: 8/10

Pros: All of the lengths

Cons: Not the absolute stiffest

We think you either love the look of Renthal stuff or you really don’t. And that is going to be pretty much the be all and end all for a lot of people. For those bothering to read this, we’re going to assume that you like the Renthal gold and black externally-ribbed aesthetic, so what is the stem like out on the trails?

As with previous Renthal stem designs, it benefits to take your time and do things properly when installing. The twin face plates are 240° wrap-around affairs so take care to side-slide them on to the bar clamp area to avoid scratching the bar or ending up with a cockeyed alignment. It’s also a really good idea to use a torque wrench to ensure the bolts are done up just-so.

There are two other things to note about the Renthal Apex. Firstly, it does offer a bit of rise (approximately 6°), which is a welcome and all-too-rare feature on sub-50mm long stems. Secondly, as with their handlebars, their is tiny but noticeable flex apparent when really heaving on it. Now then, whether this is actually a bad thing is up for debate. If you’re currently feeling like your 35mm standard front end is overly harsh, it’s well worth going down the Renthal route.

Read our full test review of the Renthal Apex

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Hope AM FR

Typically no-nonsense

Weight: 133g | Colours: Red, orange, blue, purple, gun smoke, black | Lengths: 35 and 50mm | Rating: 8/10

Pros: Hope’s signature CNC aesthetic

Cons: A bit flexier than some

Cutting straight to the chase, the pinstripe and crisp CNC vibe is either your thang or it isn’t. Truth be told, even if it is your thang, it may just simply not suit your bike. The swoopy, candy colour, gloss finish of certain carbon frames doesn’t lend itself to being paired with a bit of lasered alloy.

For those of you lucky enough to have taste and a bike that does fit the bill, you’ll be served well by the Hope AM FR stem. Much like their fellow Brit brand Renthal, the Hope stem is not the absolute stiffest option out there if that’s what you prize in front end feel. Super stiffness though, as we’ve already stated, is perhaps not a feeling to have anyway.

The use of stainless steel bolts is a nice touch. As is the modern use of a zero-gap faceplate design. It all lends the AM FR stem the typical Hope vibe that will simply float a lot of people’s boats. Fair enough.

Read our full test review of the Hope AM FR

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How we tested the best mountain bike stems

With plenty of stems to evaluate, we initially spread them between a mix of test bikes and trusted testers to put the early miles in and assess long-term durability. The testing process was topped off with a final round of back-to-back analysis on our test track.

The stems were tested on a Giant Reign with a 800mm Spank Spike Vibrocore handlebar and an aluminium Renthal Fatbar, also at 800mm, to generate maximum leverage an torsional forces. The first track blended man-made g-out berms with technical, twisty, rock gardens that demanded plenty of body language to stabilise the bike.

All bolts were greased as necessary, and tightened to the recommended torque settings using a torque wrench.

What to look for with the best mountain bike stems

A mountain bike stem connects the handlebars to the fork steerer. They come in different lengths and different rises, allowing you to tune your cockpit position Modern stems are typically under 70mm in length, with 40mm and 50mm being the most popular measurements. Generally there are twin bolts to clamp around the steerer tube, and four bolts at the face plate to attach the handlebar.

First job is to work out what stems will actually fit on to your bike. You’ll need to know your fork’s 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 or vernier calipers 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. You’ll also need to check the handlebar diameter. This will either be 31.8mm or 35mm on modern mountain bikes. Make sure you measure the area at the clamp, not the ends at the grips.

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.

Length

30mm is about as short as you can go on a standard stem. There are some newer designs 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.

Bolts

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.

Stack height

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.

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

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.

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