165mm’s make you spin faster, but with less power because of reduced leverage, 170mm’s slower but more power. This is mostly effective in road racing. But for DH racing/riding where higher cadence isn’t crucial, it mostly comes down to what feels nice for you, and what will give you the most ground clearance.

Disadvantage: higher effective gear. -shorter crank has less leverage, so lower torque output (feel like you are on a 0.5 gear higher). This means at the end of the low gear range, where you can’t shift down anymore, that gear can feel harder.

‘The research evidence is clear: crank length makes no difference to power on the road – track is slightly different – unless you go as short as 80mm or as long as 320mm. And as a bike fitter and physiotherapist, I’ve never had a reason to go bigger.

As a general rule crank length should increase with femur length. Being 186cm tall I think that 165mm will be too short for generating power. No doubt it will give 5mm more clearance but will be way too short for efficient power generation.

Hence for a given gear ratio, the 165mm will be harder to turn compared with the 170mm. (Think of pushing a door open closer to its hinge, compared to a point further from the hinge) But you may clear more roots and rocks. If the reduced leverage is noticable, I would imagine you will simply change gear to compensate.

The longer 170mm cranks will allow you to put more power into each stroke but the end result is that you legs won’t move as fast. measure the ones you have now, and ask if you wand to beat your legs faster or put more power to the ground.

165mm for DH for sure. Anything to avoid clipping a pedal on a low BB DH bike. As a general rule crank length should increase with femur length. Being 186cm tall I think that 165mm will be too short for generating power.

Moving to a shorter crank can improve: Comfort: A shorter crank length reduces range of motion at the knee (extension and flexion), hips, and low back. Aerodynamics: Going to a shorter crank will allow you to ride at a lower back angle which minimizes frontal surface area improving aerodynamics.

From the evidence above, it seems that crank length has little effect on your maximal power or your maximal aerobic capacity. So, if you’re currently on 175mm cranks, it could be worth looking into something shorter, like 170mm. If you’re a shorter rider, then something as low as 165mm could be a decent investment.

Longer cranks give more leverage and the ability to pedal a bigger gear given everything else being equal. Same applies to cranks on a bicycle. This becomes especially useful in hill climbing, when we are pushing slower revolutions and of course more difficult to push a gear climbing.

When viewed from this perspective, a bicycle crank is considered a lever, and hence, any increase in the length of the cranks has the potential to provide the rider with extra leverage. Then, longer cranks allow a rider to develop more speed than shorter cranks, even when the difference is as little as 2mm.

Crank length is measured from the centre of the bottom bracket axle to the centre of the pedal axle. If you’re not sure what length the cranks on your bike are, the quickest way of finding out is typically to just look at the backside of your cranks, just below the pedal axle.

Back in the day it was thought that longer cranks were better, because they increased the pedalling leverage, thus enabling you to create more power. However, several studies have shown that even dramatic crank length differences have only a small effect on how much power you can produce.

Namely, the general view is that shorter cranks allow you to spin and accelerate quicker but at the cost of high torque or power. In contrast, longer cranks take more time to turn over and force a lower pedaling rate, but are able to produce higher torques.

As you’ll know from using a crowbar or a wheelbarrow, the longer the lever, the greater the load that can be lifted; so a longer lever arm allows a rider to create more torque than a rider with similar leg strength, but a shorter lever arm. But there’s more to going faster than driving a big gear.

Whereas now 170 is ‘short’ 172.5mm is ‘normal’ and 175 mm cranks are very common. Still though, the difference between 170 mm and 175mm is less than 3% and leg lengths of bike riders vary by far more than that.

But you can really feel the difference. The 165s span up very quickly, so quick aceleration, whereas the 180s had lots of torque and leverage. My inside leg’s 32″ and 180 was really too long , but useful for singlespeed.

Adjusting your saddle height alters your body position in relation to your frame, and depending on the adjustment made, will open or close your hip angle. When done correctly, changing crank lengths can impact comfort, aerodynamics, clearance, and performance. Most cranksets are available in 160 mm, 165 mm, 170 mm, and 175 mm options.