Crank length is one of the most underrated fit variables on a mountain bike. The trend toward shorter cranks. 165mm and even 160mm. is driven by real on-trail benefits including better ground clearance, more comfortable hip mechanics, and improved bike handling on technical terrain. This guide explains the key lengths and pairs each with a top crankset recommendation.
| Crank Length | Best For | Recommended Crank | Price |
|---|---|---|---|
| 165mm | Technical terrain, tight hips, short riders | Shimano XT FC-M8100 165mm | ~$165 |
| 170mm | Most riders, versatile trail riding | SRAM GX Eagle DUB 170mm | ~$130 |
| 172.5mm | Traditional XC and climbing geometry | Shimano XTR FC-M9100 172.5mm | ~$300 |
| 175mm | Tall riders, enduro, gravity | Race Face Aeffect R 175mm | ~$110 |
| 160mm | Maximum clearance, aggressive terrain | Shimano SLX FC-M7100 160mm | ~$90 |
165mm - Best for Technical Terrain and Hip Clearance
The 165mm crank is becoming the default recommendation for modern trail and enduro bikes with low bottom bracket heights. The shorter radius keeps your feet further from the ground at the bottom of the pedal stroke, reducing strikes on rocks and roots. It also places the knee in a more open position at the top of the stroke, which most riders find more comfortable over long rides. The Shimano XT FC-M8100 in 165mm is the benchmark pick for this length. it combines the stiffness and precision of the XT line with the ground clearance benefits of the shorter arm.
Search for Shimano XT FC-M8100 165mm Crankset on Amazon
170mm - The Universal Standard for Most MTB Riders
170mm has been the mountain bike standard for decades and remains the most available option across all crank brands and price points. It suits riders from about 5’6” to 6’2” for general trail riding. The SRAM GX Eagle DUB in 170mm is the most popular single crank in this roundup’s length category for good reason: it is widely available, stiff, light enough for trail use, and Eagle-compatible for 12-speed systems. If you are building your first quality MTB drivetrain and are of average height with no known fit issues, 170mm is the safe and well-supported starting point.
Search for SRAM GX Eagle DUB 170mm Crankset MTB on Amazon
172.5mm - Traditional XC and Climbing-Focused Geometry
172.5mm is the traditional XC crank length that provides slightly more leverage per pedal stroke in theory, though most riders cannot detect the difference on trail. It is the best choice for tall riders on traditional XC frames with higher bottom bracket heights where ground clearance is less of a concern. The Shimano XTR FC-M9100 in 172.5mm is the race-level choice for XC competitors who want the full weight and stiffness benefits of Shimano’s flagship mountain bike group at this arm length.
Search for Shimano XTR FC-M9100 172.5mm Crankset on Amazon
175mm - Best for Tall Riders and Enduro
175mm suits taller riders. generally above 6’1”. and enduro or gravity riders who prioritize leverage in low-speed technical situations over high-cadence pedaling efficiency. The Race Face Aeffect R in 175mm is the enduro-specific recommendation: built to take rock strikes and impact damage, with a wide stance that improves lateral stiffness under the kinds of loading that happen on enduro stages. It is heavier than XC-focused options but the durability reflects that design intent.
Search for Race Face Aeffect R 175mm Mountain Bike Crank on Amazon
160mm - Maximum Ground Clearance for Aggressive Terrain
160mm is the shortest mainstream MTB crank length and is gaining adoption on enduro bikes with very low bottom brackets and on e-bikes where motor housing reduces ground clearance. The Shimano SLX FC-M7100 in 160mm delivers the ground clearance benefits without sacrificing the SLX’s well-regarded stiffness and drivetrain integration. This length is especially useful on bikes that run 29-inch wheels with aggressive geometry, where the combination of large wheels and low BB already pushes pedal clearance to its limits.
Search for Shimano SLX FC-M7100 160mm Crankset MTB on Amazon
What to Look For When Choosing MTB Crank Length
Start by identifying your bike’s bottom bracket height. lower BB bikes benefit most from shorter cranks. Then assess whether you have experienced hip impingement at the top of the pedal stroke (a sign that shorter cranks may help) or frequent pedal strikes (another indicator for shorter arms). Your inseam length is a rough guide: under 30 inches lean toward 160mm to 165mm, 30 to 33 inches use 165mm to 170mm, above 33 inches consider 170mm to 175mm. Switching crank length is one of the most impactful ergonomic changes you can make for under $200, and many riders find it worth the experiment.
Final Thoughts
The move toward shorter cranks on modern MTB geometry is well-supported by rider feedback and biomechanics research. Most riders on current trail or enduro geometry will benefit from trying 165mm. 170mm remains the universal safe choice. Tall riders and traditional XC racers have good reasons to stick with 172.5mm or 175mm. Whatever length you choose, pairing it with a quality crankset from this list ensures that the crank itself is not the limiting factor in your drivetrain’s performance.
Frequently asked questions
Does shorter crank length actually make a difference on MTB?+
Yes, and the effect is measurable. Shorter cranks reduce the radius of your pedal circle, which raises the effective bottom bracket height and reduces the chance of pedal strikes on rocks and roots. Many riders also report less hip impingement and more comfortable cadence with 165mm versus 170mm. The power difference on trail climbs and sprints is small enough that most riders cannot feel it in practice.
What is the best crank length for a 5'10" mountain biker?+
For a rider at 5'10", both 170mm and 172.5mm are appropriate choices. The traditional formula links crank length to leg length, but modern MTB fitting places more emphasis on riding style and ground clearance preference. Many riders at 5'10" are switching to 165mm for the handling and clearance benefits with no perceivable loss in climbing or sprint performance. Either 165mm or 170mm will serve you well.
Can I switch crank length without changing my bottom bracket?+
In most cases, yes. Crank length is a property of the crank arm, not the bottom bracket. If you stay within the same crank brand and model series, you can often swap to a different arm length using the same spindle and BB. Verify that the new arm length is available for your specific crank model and that the spindle interface matches before purchasing. Some models share spindles across the full length range; others have model-specific spindles.