Fixxing Vertical Drop-Outs - In 4 Steps.
Building a fixed gear bike out of my Giant CFR took a lot of thinking. Mostly, thinking about a new custom steel frame with everything perfect, Campy horizontal drop-outs, clearances, multiple braze-ons for long distance riding, etc. After about 6 months of almost constant thought about the perfect frame whilst riding around on my Giant CFR "fixed" in 39x15 (testing my perceived perfect gear of 42x16) I realised that I was potentially already riding my fixed gear bike. All I had to do was to convert the CFR and check whether this fixed gear riding is all that its cracked up to be...
*** Step 1, get rid of the rear brake calliper.
I never used it anyway. After a major high-side rear skid crash in '01, on the way to hospital (my first helicopter flight) I resolved not to use it ever again. But, I didn't want to cut up my left lever; I need it as I climb on the drops all the time. Also, I want to indicate when I make a centre of road turn, whilst braking. Solution: make both levers activate one calliper. Read Phillip's other story here.
*** Step 2, which wheels?
Well I've had these Spinergy wheels for years. They are built with no dish and are about the stiffest and most aerodynamic things around. Build quality... hmmm. Let's not speak about that. After finding the Surly Fixxer conversion on their web site, I thought use what you have... it'll be the cheapest. But a UK Surly dealer thought that the Fixxer wouldn't fit Spinergy, and in principal they are right.
Surly Fixxer and Spinergy both use the Shimano freehub spline system, but they both have a slight twist on this "standard". Both Surly and Spinergy put much more metal (taller fatter splines) into their sides of the interface than Shimano. The result is that although Fixxer fits Shimano hub body fits Spinergy free hub fits Spinergy hub body fits Shimano free hub, the final Fixxer fixed hub and Spinergy hub body interface doesn't work.
How to fix this? Using a box cutter, scrape and shape the splines on both Fixxer and Spinergy hob body so they are narrower and not so tall. Took me about an hour, as I was careful and feeling my way. It could be done faster if you know how much metal to remove in advance.
Surly provides right bearing, axle and any number of spacers with the Fixxer. For the Spinergy hub I needed to retain the existing QR axle. The hub left bearing is a cartridge type that matches a step in the axle to generate tension for the standard right cup and cone bearing in the freehub. With the fixer, just use their spacer nut which provides the bearing surface for their right side cartridge bearing. To space for 130mm dropouts I used one of their #2 spacers.
The end result is great. The chainline is 41mm from the inside of the thread. I used a DA cog with the shoulder in, which results in a 47mm chain line. Perfectly lined up with the outside of my double DA chain ring. I wish I'd known this before I set it up. I lost a lot of sleepless nights worrying about chainline... perhaps I worry to much.
*** Step 3. What gear?
That's a question that can be answered simply. Every Australian cyclist knows that (Sir) Oppy won the '31 PBP using a 69" fixed gear. So, if I was going to ride the PBP fixed in '07 then it had to be 69" too. So that made it simple... 42x16 it was.
*** Step 4. Chain length?
I used both James Quinlan's ssConvert, and FixMeUp! www.peak.org/~fixin/credits.html to work out that if I use 42x16 then COINCIDENTALLY, my chain should be tight. Well it didn't work out quite right, because of the difficulty of measuring the chainstay length accurately. When I tried the 42 chainring that I ordered, the chain drooped like a laundry line hung with wet washing. A quick test of 42x17 showed me that 43x16 should be my magic number. When the 43 chainring arrived, things were a little tighter I'd hoped, especially when I put on a new 8-speed chain (SRAM PC48). But, with chain tension a very little is often enough. I could see that only fractions of a mm separated me from success. 30min of filing, and testing every 20 or 30 strokes on each dropout, saw it fitting well.
I was careful to remove the same amount of metal from both sides, so that the wheel would still fit straight.
In the worst case, it'll be difficult to take up tension as the chain wears. But if I keep using inexpensive chains then I won't mind regular replacement of this part. Alternatively, I might find that I can keep the axle in the new "back" of the dropout (only 0.5mm back) with my QR tight, and this will fix the tensioning issue. I've no experience. We'll see as things get on.