The Crank Diaries

The process of converting my current commuter into a fixed gear has been a bit slow, but it certainly hasn't been non-existent.  Since the cog I need turns out to be really difficult to come by (read: out of stock everywhere always), I decided to start by tackling a problem that affects any type of bike I ride - crank length.

I love box.

Now, I've heard many schools of thought regarding crank length and how it affects your gain ratio and knees, I've looked at countless formulas regarding your femur to crank arm length ratio, and I've taken who knows how many measurements that I've multiplied by the pantome color closest to my bike frame, etc.  Here's the deal: 165mm cranks are the most comfortable for me to ride.  I can do 170mm on a road bike, but anything higher than that feels a bit wonky to me.  One might say that's because the longer crank is upping my gain ratio and I'm not used to spinning that way, but I honestly feel anything larger than 170 is a bit of a stretch for me.

As soon as I hopped on the Trek District I felt completely off kilter - my legs were behaving wrong, the seat felt too high, something was off.  It basically felt like I had just taken too much cough syrup and was trying to ride the bike to The Magical Land of Robotussin.  Lo and behold, it had 175mm cranks, which took a long while and a lot of tweaking of seat and handlebars to get used to.  When I decided to keep the bike, I opted to drop to 165mm; it's my crank size and it's better for riding fixed anyway due to pedal strike and RPM. For the record, all of my bikes are 165mm, with the exception of my 167.5mm road bike.

I was hoping to put a track crank on this bike, but interestingly enough Gates only makes their belt rings in mountain and road BCD, so a track crank was out of the question.  I instead opted for a Sugino RD, which would not only work with the belt ring but maintain my existing chainline with my current bottom bracket - 47.5.  

My chainline calculations were correct, and the crank looks much better than the stock one.

Wait for it...wait for it...

That's my favorite part.

After a few test rides the chainline and chainring bolts were holding up fine, and I can definitely feel a difference on these cranks.  I had to readjust everything so that my legs were moving the correct amount, and it feel like a brand new bike.

The only problem is, the shorter lengths lowered the gain ratio, and I'm spinning out of the rear cog quite a bit.  The next step will be to install a temporary Surly Fixxer and the elusive always-out-of-stock-cog, once I can find it, which I will use while a proper rear wheel is being built.  The new cog will up my ratio...so I'm excited. 


Crank length is one of those grey areas for me, and everyone seems to have mixed feelings on it.  I think my ideal length is technically somewhere around 167.5, but I like my 165s. 

I'm also doing a few aesthetic upgrades at the moment.

It was my name long before Gangnam Style.

No, I'm not completely vain - I have a legitimate reason for adding decals like this...but that will be in another post.