Drivetrain and tire clearances are a critical clearance area on any fatbike frame. With wider rims, 80 or 100mm, becoming the norm for fatbike usage, drivetrain clearances are becoming tight. To gain clearance between the chain and tire when in the front small chainring and the largest rear cog there is a simple modification any Mukluk rider can make. If you are finding that your chain rubs the tire when in the 22T chainring and 32T rear cog this modification will help you get additional clearance between the tire and chain. Additionally, this modification eliminates the two smallest rear cogs that I find rarely get used on my fatbike.
For this modification you'll need a Surly Spacer Kit and all of the proper tools to remove and install the cassette, along with the tools necessary to re-assemble and re-adjust the drivetrain.
The list of tools includes:
Here is a quick list of steps:
When complete you'll end up with a rear cassette mounted on the freehub body that looks like this:
With the cassette moved out 2.5mm you'll gain precious clearance at the tire that looks like this:
A 2.5mm spacer behind the cassette translates to more clearance where the chain passes by the tire when in a 22T chainring and 32T rear cog.
This modification was made using the stock X.7 rear derailleur. Different derailleurs may yield different results. For example, on my Mukluk I have run an X.9 rear derailleur. The rear plate on the X9 derailleur is aluminum instead of steel, like the X.7. In order to execute this same modification I needed to change the limit screws to a longer M4 x .7mm bolt. I have not found a rear SRAM derailleur that effectively allows for a 5mm spacer behind the cassette to provide more chain/tire clearance without modification. Both the X.7 and X.9 required modification to the derailleur itself for the upper limit screw to allow for proper adjustability.
If any of this doesn't make sense to you, we strongly recommend that you take your bike in to your local bike shop and have them help you with the modification. They can help you get it sorted and back out on the trail in no time.
This post filed under topics: Mukluk
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I've had a lot of good luck and made a series of choices to be working for the brand and in the bike industry. In 2007 I signed up for the TransIowa just to see if I could complete it. I completed it and discovered a few things about myself in the process. Adventure cycling has been in my blood ever since.