Saturday, August 30, 2008

The Frankenstein Bike

I have three geared mountain bikes now. The first a 1998 Bontrager Sport, which I will show later. The second is a 1993 Barracuda A2T that I bought from a friend a couple years back. But this post is about my newest completed project. A 92-92 Yokota Project USA mountain bike. The idea was simple. I had a need for a small framed mountain bike. A friend at work found this frame and offered it to me. It included the crankset. At first I had some strange idea that I would be able to build the bike from spare parts. First I had a 9 speed SRAM derailleur, shifter and cassette I got in trade for the cranks and derailleurs that came off my Peleton.
Also, I have some an NOS Bonty seat, brake levers, a handlebar and a used set of Panaracer tires thar still had some meat on them. Unfortunately I discovered immediately discovered that I really had nothing else that fit; off to the LBS that sells used parts. I planned on using a threaded fork and found a NOS Tange fork at the LBS. They further had a NOS XT cartridge headset, which are really nice BTW. My bike now had a fork.
I also needed a front derailleur and the LBS just gave me one (cool). The LBS also had one of those funky adjustable stems, which seemed to fit the bike. I looked up and saw a couple of wheelsets. The only one that really fit the bill were some old style XTR/Bontrager wheels. The LBS gave another deal ($100) and I had wheels. The LBS also had a set of Tektro V brakes they had taken off a bike when it was upgraded to discs; $15, score! This LBS did not have a seatpost or seatpost collar, so I checked another (Santa Cruz is so cool). I got a seatpost but no collar. Turns out 30.0 is an off size. I finally had to order one off the web.

Problems and Retro-fit

I thought the headtube was 1 1/8, but it turned out to be 1 ¼. I really don’t know how common 1 1/4 was in the early 90’s but there couldn’t have been a lot of them. I ended up needing a 1 1/4 to 1 1/8 reducer to make it fit.

The crank on the bike was a Standard size, meaning the chainrings were 46/36/24. Back in the middle to late 90’s Shimano switched a compact drivetrain, 42/32/22. They have now switched back, so I needed either a very old or a very new front derailleur to be compatible with the Standard. Fortunately my friend at the LBS had a newer front derailleur. Since it had a 26.8 clamp, which won’t fit on most new bikes since the industry has gone to larger seat tubes, he just through it in for no cost. A little more history here. Shimano's idea of a compact drive train meant smaller chainrings and smaller cassettes They reduced the 5 arm triple crank BCD from 110/74 to 94/58 and then to a 4 arm crank BCD of 104/64. The idea was to reduce weight. However as 9 speed cassettes grew to 34 teeth, there was really no point to the compact cranksets and Shimano went back to Standard size chain rings but stayed with the smaller 104/64 BCD.

The Yokota had three sets of cable stops on the right side. They where meant for the rear brake and derailleurs and the bike had a hanger for cantilever brakes. Since I was going to upgrade to V brakes, I had to run a brake cable down the right side. Unfortunately, I ran out of black cable and had to use white, but that’s easily fixed.

And that was about it. The only other issue was it looked like some had just taken a hammer and pounded off the old headset. I ended up filling the divots, masking the headbadge and repainting the headtube. It was more of a hassle than I thought, until I discovered I needed to wait 48 hours between coats. You can see some of the divots if you click on the seat tube photo.

The bike it not as pretty as my other bikes, but it’s very utilitarian. My wife is 502, my son is 9 and about 409, and I have a step-daughter that’s 506. My Bontrager is can also work with someone short in stature, as they were made very small. With all the bike riding we do as a family, I expect this Frankenstein bike will get lots of use.

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