Shorter Cranks - Are They for You? 14

Short cranks are not all that new, but they have historically been a bit of a specialty item where mountain biking is concerned, mainly relevant in the gravity space. Over the last couple of years however, we’ve been seeing more manufacturers opting to add shorter and shorter options to their line-up, which left us curious as to where this trend might be headed. What are the benefits or disadvantages of shorter cranks? How do shorter cranks fit into different riding disciplines? How short is too short? Those are just some of the questions we wanted real-world answers to, so we hit up Samox to supply us with a selection of cranks and we set about testing. Keep reading to find out how we got on.

Samox Platinum TM-1 Highlights

• Carbon fiber construction
• Crank lengths: 145, 155, 160, 165, 170
• 3-bolt Direct Mount
• Axle: 28.99mm (DUB)
• Q-Factor: 168mm
• Recommended use: Trail/All Mountain/Enduro
• No-questions-asked lifetime warranty
• Weight: 369 grams (crank only, 155mm, verified)
• MSRP: $325.00 USD (ex tax)

Initial Product Impressions

As a brand selling product under its own name, Samox is a new kid on the block, but they’ve been manufacturing cranks in Taiwan for many other well-known brands for 50 years now. In their own catalog, they now have both aluminum and carbon cranks for road and mountain bike applications. For this test, we opted for the Platinum TM-1 crank, a carbon crank which is available in lengths from 145 to 170 mms and is recommended for various riding disciplines up to and including enduro (Samox does have a DH-specific carbon crank as well, if you need something even sturdier).

The cranks look good out of the box, with a relatively low-key appearance that will fit in well on pretty much any bike. The build quality is good, with a smooth uniform finish and well executed machining. The TM-1 relies on a standard 3-bolt interface for the chainring, which means you can run any SRAM ring or compatible – we opted for Samox’s own. In keeping with the SRAM standards, the TM-1 also features a DUB-compatible spindle that measures in at 28.99mm (insert your own DUB joke here).

Installing the TM-1 is straightforward, just make sure to have the correct spacer available for your BB/frame. Tighten the main spindle bolt and take up any slack with the preload ring, just as per usual. During the course of this test, we’ve mounted and removed the cranks a number of times on a number of different bikes, and we have not had them misbehave on us so far. Note that Samox do not supply crank boots or any kind of protective film, so you might want to make that investment to keep the cranks looking fresh for longer (always a good idea to protect carbon components if you can).

Crank Length Research

There has been a lot of research into crank length, and the common consensus is that crank length has little to do with things like power output and efficiency, within a fairly broad band of different crank lengths. Some significant variation is typically observed at the extreme end of the crank length spectrum, like 120mm or 210mm, but in the 145-175 range it seems like power output is fairly consistent (tested on the same rider with different crank lengths). If anything, shorter cranks may be a little less demanding in terms of “metabolic cost”, i.e. the “fuel consumption” of a rider, but it’s scientifically marginal at best.

But Aren’t Shorter Cranks Harder To Pedal?

Not really, no. Yes, you lose some leverage and thus torque in extreme circumstances, but most riders can make up for this by pedaling at a higher cadence using a lower gear. Because the foot actually has to travel a shorter distance as it completes a revolution with the shorter cranks, the resulting power output is the same if you pedal a bit faster with a smaller gear (power = force x velocity). Conversely, a longer crank is more demanding to “spin up”, which can actually make it seem more difficult to get up a steep obstacle for example.

What About My Knees/Back?

Here’s where it gets interesting. Intuitively, we thought that with a shorter crank we’d have to apply more force to the pedals, and thus the potential for knee or lower back pain would increase. Turns out that the opposite might well be true. With a shorter crank, you don’t have to bend your knees and your hips as much at the top of the pedal stroke, which actually decreases the stress on the joints. With a less demanding pedaling motion, you also don’t need to rock your hips quite as much, which can help reduce/avoid lower back pain.

Geometry Considerations

When you run shorter cranks, you need to raise your saddle to compensate (the leg should have the same, ideal extension at the bottom of the pedal stroke with any length crank). If you reduce the crank arm length by a significant amount, you may find that you need a longer dropper post to get back to the same amount of clearance you had before. There are a couple of other, less obvious factors to take into account as well, namely the effect a shorter crank has on your body position on the bike. When you make the crank shorter, you actually raise your body up higher (by virtue of the feet moving closer together when standing on level pedals), and you could also argue that your forward-aft balance may be affected since you theoretically dispose of a less stable base in the direction of travel.

On The Trail

Now to the bit that matters: what were our experiences out on the trail? We’ve had 5 riders participate in the testing for this one, and we thought it would be useful to present each rider’s observations separately. Our goal here isn’t to try to determine the “best” crank length, but rather to describe how different riders reacted to using shorter cranks than usual.

Jason Schroeder – Vital MTB Tech Editor

I've historically run 165mm cranks on my downhill bike and dirt jumper and 170mm cranks on any pedal bike. My logic has always been that shorter cranks keep my feet a little tighter together, and since I'm not pedaling those bikes much, why run longer cranks? That logic was put into question after I tested a few e-bikes with 160/165mm cranks. The ability to ramp up my cadence and keep the rear wheel (and motor) driving power piqued my interest, and I was curious to know how shorter cranks would fare under just my own power. 

I tested 145, 155, and 165mm cranks. 145mm cranks were the point of diminishing returns, while 165mm didn't feel much different than my usual 170mm cranks. 155mm cranks were short enough to produce some cool benefits without sucking to pedal with. 

I'll start with my Goldilocks length, 155mm, to help explain how cranks on either side fell short. The best part about pedaling with the 155's was how much easier it was to hold consistent power throughout my pedal stroke. I ride with flats and tend to 'chop' at the pedals - my downstroke generates the most power, while not much happens during my upstroke until my crank reaches its highest point. The smaller circles my feet made with 155mm cranks allowed me to hold a steady output. My feet felt like they reached the top of my pedal stroke sooner, and there wasn't a lag between strokes. This paid the most dividends through bumpy climbs, where keeping momentum and shoe-to-pedal contact was crucial. The other (unexpected) benefit of the 155’s was how much easier it was to stand up and sprint. Again, since my feet didn't have to travel as far, I could lay down more pedal strokes in a short period of time. I also had fewer issues with my feet floating on my pedals at the top of my pedal stroke while standing. 

Descending with 155mm cranks was rad. I didn't feel like I stood any taller but I loved being more centered over my bike. It reminded me of riding a jet ski or dirt bike, where you can really lean the bike over in turns and steer more with your hips. I also had fewer instances of my legs being in the way when leaning the bike over through tight corners. I'm left foot forward, so right-hand turns have always been tough as it's not natural to pedal forward to drop my left foot and let my right pedal go up. 155mm (and 145mm) cranks helped resolve this issue and I rarely got balled up in awkward sections. 

What I didn't like about 155mm cranks was that I had to pedal at a higher average cadence and ended up riding at a higher average heart rate. This was especially true on flatter sections as it felt like I had to maintain a higher intensity to keep moving and couldn't just spin along. I also noticed a lack of torque in really steep sections. It was enough that I avoided some more direct climbs on my local trails. 

The 145mm cranks had the same positive attributes descending as the 155's, but they weren't noticeably better. They were, however, noticeably worse for pedaling. Even with a smaller 30T chainring, I spent most climbs in my easiest two gears, feverishly spinning to hold the same speed as I would with 170mm cranks. The higher average cadence made it tough to power through technical sections because I was already near the limit of how fast I could comfortably pedal. And having to pedal even faster to muster up some extra watts was tiring. Even more so than the 155’s, flatter moments of trail required a higher cadence to keep moving, which made it hard to recover on climbs. 

Dropping to a 28T chainring or 27.5-inch rear wheel likely would help, but I'm not sure what I would gain by riding the 145mm cranks that the 155's don't already solve. I suppose ground clearance would be the main benefit. I would only ride these cranks if they were on a DH/park bike and I was spending most of my time coasting or if I had shorter legs. 

As for the 165’s, I struggled to notice much difference climbing or descending vs. the 170mm cranks. They felt really similar, so I don't see myself going out and buying a set of 165mm cranks to replace my 170mm. Maybe the next frame-up build I do will have 165’s. The only other reason I could see for going with 165’s is if you struggle with crank strikes and want to gain some ground clearance without drastically changing your pedal stroke (assuming you are currently running 170mm).  

All told, I'm definitely considering 155mm cranks with a smaller chainring (28T) on my enduro bike. The benefits while descending outweigh the drawbacks when pedaling. I don't think I'll go any shorter, and for bikes that I plan to pedal more and want to maximize efficiency with, I'll stick with 170mm cranks.  

Johan Hjord – Vital MTB Tech Editor

I started riding mountain bikes when a crank arm was by default 175mm long. At that time, a size L bike had about 430-440 mm of reach, and a head angle of 65 degrees was really only found in the DH category. Over the years, I started experimenting with slightly shorter cranks, but staying “reasonable” at 165 mm at the shortest. I never really put much thought into going shorter than that, mainly believing that climbing would be too hard and that it wasn’t worth the extra ground clearance. After just a couple of rides on the 155mm version, it became clear that my fears were unfounded, and that I had even unlocked some unforeseen advantages.

The biggest change for me is a feeling of power on the cranks, with the shorter stroke making it much more comfortable to actually push hard on the pedals. Because you don’t have to bend your knees so much, you start the stroke from a much stronger position and the movement feels less strained, even though you may have to produce a bit more force on the pedal in some situations. Somewhat unexpectedly, I also felt like there was less of a cardio toll when climbing. I regularly found myself pushing the same or even slightly faster speeds up my habitual climbs, without feeling any more out of breath (granted, this is not a scientific observation, but my Strava backs it up in regards to time and heartrate data). It is also easier to accelerate, for example when needing to clear an obstacle during a technical climb. The extra ground clearance obviously starts to become significant at this crank length, and I could actually pinpoint a couple of rocks that I could suddenly keep pedaling over where I would usually have to do a ratchet move.

As for the downhill side of the equation, I felt at home from the first ride with the 155 mm cranks. Having your feet closer together (in the fore to aft direction) may geometrically make you stand a bit taller on the bike, but I also felt like it makes it easier to move the bike around with more precision. Think of it like driving a car with a shorter ratio steering rack.

There are some downsides to the shorter crank, notably in extremely steep situations where you are on the limit of how much force and torque you can produce. Personally, this makes up only a very small fraction of my everyday riding, so it’s not an issue for me, but I could see it making life harder for you if this kind of riding is something you do a lot of. You can of course run a smaller chainring to compensate, but pedaling faster might not always be an option in steep, technical climbing scenarios. I didn’t test the 145 mm version, but I’m intrigued by what the other testers said about it and I’ll definitely never say never regarding crank length again. For now, I’m keeping my 155mm cranks on one of my bikes to see what the longer-term effects may be.

Darina Privalko – Test Rider

Darina has only been riding mountain bikes for about three years, and while she is not yet at the full-fledged shredder stage, she had one particularly interesting observation after reducing her crank length: she now finds it easier to drop her heels and get behind the pedals when braking and descending steeper sections. This jives nicely with how other testers observed that the bike feels more reactive and responsive to smaller inputs through the feet.

Mikey Egan - Test Rider

Even though I usually run 165mm cranks, there was a noticeable, positive difference going down to the 155’s. What I liked the most was that my pedal strokes felt consistent throughout their full rotation. I wasn't stomping on the pedals as much as I do with 165’s. It didn't feel like I had less power or torque, but I was climbing a gear easier than I normally would, and spinning a little faster than usual. But I rarely ran out of gears, and I actually liked the higher cadence as it allowed me to spin instead of having to put out high-torque pedal strokes. It was also easier to power through tech sections as my cadence was already above average. Going downhill, I enjoyed how my feet were closer together, which gave me a more solid body position from which to react. I had fewer instances of getting jostled around on the bike. It was also cool to be able to lay down a few quick pedal strokes coming out of corners.

The 145mm cranks required me to spin quite a bit faster, and they were way more tiring on climbs. I definitely ran out of gears with the 30T chainring and could not generate as much power as the 155’s. Even on flat sections, I had to spin above my normal cadence to keep moving at a normal speed. They were definitely better going down than up as they offered that centered, balanced over the bike feeling that I liked about the 155’s. But they were bad enough on the climbs that I would only go as low as 145mm on a DH bike.

Lauren Williams - Test Rider

I really enjoyed the 155mm cranks, as they allowed me to produce consistent power throughout my entire pedal stroke. With the 170mm cranks that came on my bike, I've always felt like there was a lull between my pedal strokes, like I was only getting power when I would push down. The 155’s made it easier to spin and carry momentum through rocks and up ledges that I regularly got hung up on before. The extra clearance was also appreciated during these moments. I did find myself pedaling with more intensity than I usually would. It was hard not to spin at a faster cadence, and even if I wasn't actually going faster, it still felt like I was pushing harder. This made me more out of breath on my local climbs, but not to the point that I wanted to take the cranks off. Since I could push through technical sections that typically gave me issues, I was okay with being a little tired if it meant I could clean entire climbs. Standing and pedaling was also great, as I was able to squeeze in a few more meaningful pedal strokes on descents. And speaking of descents, I had a much easier time popping off jumps and drops with my feet being closer together. I felt like I was in a more powerful stance and could influence my bike more easily. 

The 145mm cranks rode similarly to the 155's, with very marginal differences when it came to clearance, bike maneuverability, and power consistency. Where the pros were nearly the same, the loss of 10mm did come with some cons. I noticed that my heart rate began to spike quicker with the shorter cranks, which was especially noticeable on gradual climbs where I normally don't have to put as much effort in. It felt like I was being forced to charge through each pedal stroke with zero rest for my legs. It was the polar opposite feeling of the "lull" that I experienced with my 170mm cranks. 

When pedaling with the 155mm cranks, my power was carried farther into the pedal stroke, making each spin more fluid. The 145’s left me feeling like I was in an all-out sprint on most ascent. I think the 155’s were a nice sweet spot if you're looking for the benefits of running shorter cranks without feeling like you just left a HIIT class after each climb.

What’s The Bottom Line?

If we had to sum up our collective thoughts in the shortest way possible (pun fully intended), we’d say “never say never”. Many of us have been reluctant to even consider significantly shorter cranks, fully believing that 165 or even 170 is as short as we should go comparing to that old 175 “standard”. Our preconceived ideas definitely took a hit very early on in the testing however, as we all found many advantages to the shorter cranks. While the jury was divided on the actual differences in effort required to pedal shorter cranks, we all found that they provided for a cleaner pedal stroke and a feeling of improved maneuverability on the bike. Beyond the purely physical aspect of better ground clearance, the shorter cranks created a feeling of connectedness and power that is quite intoxicating. Our collective sweet spot landed at 155mm, and some of us are certainly going to keep riding that crank length now.

More information and shorter cranks available at: www.samox.com.

About The Reviewers

Jason Schroeder - Age: 29 // Years Riding MTB: 18 // Height: 6'0" (1.82m) // Weight: 175-pounds (79.3kg)

Inseam: 32.5” (82.55cm)

Usual crank length: 170mm

A once-upon-a-time World Cup downhill racer turned desk jockey, Jason has spent years within the bicycle industry from both sides of the tape. A fan of all-day adventures in the saddle or flowing around a bowl at the skatepark, he doesn't discriminate from any form of two-wheeled riding. A SoCal native who doesn't spend too much time in any single place, you can find Jason camped out in his van most weekends somewhere on the West Coast.

Johan Hjord - Age: 51 // Years Riding MTB: 19 // Weight: 190-pounds (87 kg) // Height: 6'0" (1.84m)

Inseam: 34.25" (87cm)

Usual crank length: 165/170mm

Johan loves bikes, which strangely doesn’t make him any better at riding them. After many years spent practicing falling off cliffs with his snowboard, he took up mountain biking in 2005. Ever since, he’s mostly been riding bikes with too much suspension travel to cover up his many flaws as a rider. His 200-pound body weight coupled with unique skill for poor line choice and clumsy landings make him an expert on durability - if parts survive Johan, they’re pretty much okay for anybody. Johan rides flat pedals with a riding style that he describes as "none" (when in actuality he rips!). Having found most trail features to be not to his liking, Johan uses much of his spare time building his own. Johan’s other accomplishments include surviving this far and helping keep the Vital Media Machine’s stoke dial firmly on 11.

Darina Privalko - Age: 48 // Years Riding MTB: 3 // Weight: 140-lbs (63 kgs) // Height: 5'3" (1.61m)

Inseam: 29.5" (75cm)

Usual crank length: 165mm

Darina discovered mountain biking later in life, but instead of spending any time looking back at what could have been she tackles every adventure on her new two-wheeled friend with unbridled enthusiasm - heels down and eyes up!

Mikey Egan - Age: 20 // Years Riding MTB: 5 // Height: 5'9' (1.75m) // Weight: 170-pounds (72.6kg)

Inseam: 32.8” (83.3cm)

Usual crank length: 165mm

Obsessed with anything with wheels, Mikey has been born and raised in SoCal. You can usually find him at the beach or on top of a mountain. As a young kid, he rode BMX bikes as much as he could. Now a bigger kid, he has grown fond of suffering on his road bike and getting sketchy with friends on his trail bike. He loves to ask questions and tinker with bike setup until it's perfect. 

Lauren Williams - Age: 26 // Years Riding MTB: 6 // Height: 5'5" (165cm) // Weight: 120lbs (54.4kg)

Inseam: 31” (78.7cm)

Usual crank length: 170mm

Originally from Reno, Nevada, Lauren spent her formative years competing in rodeos with her horses across the southwest. After moving to Idaho to attend Boise State University, she was introduced to mountain biking and quickly became consumed by her new found passion. The better part of her college years were spent working at a bike shop and spending debatably too much time around bikes. Nowadays she is based in SoCal, and spends most of her free time having fun on two wheels with her fellow bike lovers.