Race Face 160mm:
Race Face recently released their Turbine crankset in 160mm, which are probably sufficient for most riders. It's both the cheapest and easiest way to do to a shorter crank. The cranks are $180-200 new:
If your stock crankset is a 24mm spindle you'll also need need to buy the 30mm spider lock ring (part #1347006) from Rocky Mountain ($40-50), along with a press fit BB92 30mm bottom bracket. The Race Face Double Row Cinch 30mm is my recommendation at $85:
In addition, if your stock crankset is 24mm, you'll need the Race Face 149.5mm spindle kit:
North Shore Billet 145mm, 155mm:
If you want to go shorter than 160mm, the easiest solution, though the most expensive, are the Powerplay cranks from North Shore Billet in 145mm and 155mm lengths for $535:
They're a direct upgrade. If your stock crankset is a 24mm spindle you'll also need need to buy the 30mm spider lock ring (part #1347006) from Rocky Mountain ($40-50), along with a press fit BB92 30mm bottom bracket. The Race Face Doubel Row Cinch 30mm is my recommendation at $85:
https://www.raceface.com/products/bb92-double-row-cinch-30mm
Race Face Atlas 155mm:
A less expensive, but more difficult alternative is re-drilling Race Face 175mm Atlas crank arms to a 155mm. This can be done because the Atlas cranks aren't hollow, and the back side ribs don't extend very far, leaving a lot of aluminum around the new pedal hole. New Atlas cranks can be had new for $180, but can be found used for about $100:
https://www.raceface.com/products/bb92-double-row-cinch-30mm
https://www.raceface.com/products/bb92-double-row-cinch-30mm
Like before, if your stock crankset is a 24mm spindle you'll also need need to buy the 30mm spider lock ring (part #1347006) from Rocky Mountain ($40-50), along with a press fit BB92 30mm bottom bracket. The Race Face Doubel Row Cinch 30mm is my recommendation at $85:
The Atlas cranks will also need the 151.5mm RD151DH spindle, if it doesn't already come with the crank arms:
Although the cranks can be run like this, I recommend added Race Face crank boots to make it look better for the nominal cost of $12:
https://www.amazon.com/dp/B00JNAK4OU
https://www.amazon.com/dp/B00JNAK4OU
You'll need the following tools:
- Mill or drill press
- 1/2" drill bit
- 9/16-20 tap - left and right hand
- 13/16" end mill
- Dremel or angle grinder
You need to mark and center punch the location of the new hole on the back of the crankarms, 20mm up from the existing holes.
Then they need to be drilled with a 1/2" bit. This can be done using a drill press or a mill. It is not recommended to try and do it free hand. I found it easiest to fixture the crank arm upside down, though there are multiple way to accomplish this.
After drilling the new hole, flip the crank arm over and use an end mill to flatten the area around the new pedal hole to give a flat surface for the pedal to seat against. I used a 13/16" end mill. Since this is a drilling operation and not a milling operation, a drill press should be safe to use.
The new holes now need to be tapped. A set of 9/16-20 taps on Amazon are less than $30. Make sure to use plenty of tapping oil and make sure to use the left tape on the left arm and right tap on the right arm.
Once the holes are tapped the extra crank arm length can be cut off. I prefer to use a vertical belt sander to give the end of the crank arm a nice rounded shape, similar to stock. Note, part of the original pedal hole will still remain at the end of the crank arm.
I think it's pretty evident that unless you already have some of the tools needed (and some experience using them), it's probably cheaper to go with the North Shore Billet cranks.
Additional information can be found in this thread on EMTB Forums:
https://www.emtbforums.com/threads/shortening-your-cranks.29059/
https://www.emtbforums.com/threads/shortening-your-cranks.29059/
