CROSSISCOMING so it's time to start thinking about our thriving local Southern Oregon CX Race scene.
This year for something a little bit different (AKA making life harder for myself!) I thought it would be fun to race single speed... of all the different forms of bike racing i've done over the years i've never raced single speed so here goes.. i'm thinking, i'm good at running, I can push a big gear when I need to.. what could possibly go wrong?!
First up I need a bike and don't want to splash out on a single speed specific rig (just yet), so in true cyclo-cross fashion i'm looking to re-use what i've already got in my garage with a few new parts where needed.
The chassis for this conversion is my trusty Canyon Inflite AL frame, an alloy disc CX / winter road frame with carbon fork that i've had since 2013. This is a solid, super reliable frame & fork that over the years has been pressed into service in numerous guises, and despite a few bumps and scratches is still going strong...
So here we are with it's 5th new lease of life and first up solving the issue of single speed compatibility on a non single speed frame.
There are a few options to consider for the conversion:
1- Easiest is to run a chain tensioner like the Paul Melvin with a single speed conversion kit for the existing rear wheel (Mavic Crossmax 29er with a Shimano Freehub). This is the cheapest in terms of new parts needed, and the most straightforward to achieve when it comes to chain line and ease of switching cassette sprockets to find the right gearing.
2 - Build a new rear wheel around the White Industries Eccentric ENO disc hub. This is my preferred option as it avoids any potential issues with dropping chains etc when using a tensioner.. and lets face it, it just looks a little more PRO as a single speed set up.
But the big question here is whether the chainline on the bike with the existing ROTOR 3D crankset i'm running is close enough to the 45mm that our friends at White Industries recommend for use with this hub. Assuming the chain line checks out my plan is to re-build the rear wheel from an old pair of carbon 29er XC (non-Boost) wheels that have been gathering dust since everything moved to Boost.
The other option would be to build a completely new set of wheels around the Knight Composites TLA 35 rims, but given a single speed wheel is no good for anything else the rest of the year I decided this was a little excessive and i'll stick to re-using my old gear!
There are of course other options for a single speed conversion that use some form of eccentric bottom bracket. Either a PF30 eccentric BB or a Phil Centric English threaded BB. But with the BB92 pressfit on the Canyon neither of those are an option as there is nothing available to fit it. Using a 30mm crank like the ROTOR 3D also rules out any Chris King bottom bracket so i'm sticking with Enduro BB86/92 4130 / 41mm bearings which are pressed directly into the frame.
Checking the chainline.
I marked the center of the seat tube with a sharpie after measuring it with a pair of calipers, looks a little funky given the tapered / asymmetric seat tube, but the line is pretty much in the center.
Fit existing ROTOR cranks with new 38T CX round chainring.
Measure distance from the chainring to the mark on center line of the seat tube.
Although its not very clear from the pictures the chainline is very close to the 45mm recommended by White, sure there's a pretty decent margin of error on the measurement (maybe 2 or 3mm) but it's close enough to give me confidence that this will work.
If I need it there is some adjustment on the chainring either by mounting it to the inside of the crank (like an inner ring) plus using spacers between the BB and chainring to space it out more, or alternatively by using a 0.5mm cassette spacer to move the freewheel out slightly.
Stay tuned for the next installment where I check everything fits together on the frame and the chainline works before having my old rear wheel re-built around the White Industries hub.
If you're thinking of your own conversion for CX season or have any other product related questions contact us and we'd love to help you out!