TBT Surly Moonlander Build Part 5 – Bottom Bracket and Cranks

Posted by TBT Crew on Mar 3, 2012 in Bike Maintenance, Blog, Fat Bike, TBT Surly Moonlander Build | 0 comments

I put a lot of time and thought into what cranks and bottom bracket to use on my Surly Moonlander. The first limiting factor when selecting a set of cranks for a Snow Bike is one that supports a 100mm bottom bracket. There are a few manufactures that make 100mm bottom brackets they include Truvativ, e*thirteen, FSA, Phil Wood, and Surly. I really took a close look at Truvativ’s Hussefelt line of cranks. They come in a couple of colors and the Truvativ’s Howitzer BB and Hussefelt cranks are stock on the Surly Pugsley kit bike. I also loved e*thirteen’s line of cranks and their manufacturing quality is excellent. But as I started to price different options they all started to be close to or exceed the price of the Surly Mr. Whirly cranks set. So I decided do go with the Surly cranks, and I am glad I did.

The Surly Mr. Whirly cranks can be ordered specifically for the Moonlander frame (that is what I did). The Mr. Whirly cranks for the Moonlander come with all the spacers necessary to have the included bottom bracket fit perfectly with the frame. The included bottom bracket Surly uses also has outboard bearings which is a design I love. Another reason I am glad I went with the Mr. Whirly cranks are the available spiders that allow you to customize the cranks for use with many different chainrings. The final reason I am glad I went with the Mr. Whirly’s if the fit! You can tell the frame and the cranks were designed to fit together (see picture below).

I went with a 18t cog on my Shimano Alfine 11 speed hub and a 34t chainring on the cranks to achieve Shimano’s recommended 1.9 gear ratio. On line you will find many people using nonstandard gear ratios with Alfine hubs. I figured the 1.9 ratio is a good starting point, and my legs are pretty strong from putting on many miles biking a year so this should not be a problem. Here is a link to Sheldon Browns gear ratio calculator, a very helpful tool!

I also put on a clear chainstay protector to keep that Space Boat Black paint job looking it’s best.

Install went flawless except for my wrench slipping on the PTO dust cover (which gouged it). Luckily Surly has replacement parts for it that only cost a few bucks.

So the final build for my Cranks are:

Surly Mr. Whirly Cranks

Surly Moolander Bottom Bracket

Surly Mr Whirly Spider, 58/104mm BCD

e*thirteen 104 BCD 34t Guidering chainring (for single speed or 1×9 drivetrains, helps keep the chain on)

Surly bashguard

Lizard Skin Chainstay protector

UPDATE: Surly has gone to after market ENDURO® bottom bracket bearings. These are a major upgrade to the cranks. Surly currently uses Shimano Holowtech II style bottom bracket bearings. So there are many options out there for replacement. You just cant use the inner sleeve that comes with them unless they are made for a 100mm bottom bracket. Note: The original Surly bearings never used an inner sleeve.

Here are pictures of the build: