When I bought my bike last September, I didn't think I would ride it too much. Because of that, I decided to get a pretty good bike, but not one with high end stuff on it. I ended up with a Canondale Trail SL4 29er, which has a good frame, but the rest of it is kind of low-end -- Shimano Alivio/Acera components and a no-name front fork (RST Deuce TNL).
It ended up that I rode almost every day. I found a great route between Palo Alto and San Jose, and would ride the 25 miles home from work 2-5 days per week. I'd ride to the train station every morning, and took it out on the trails almost every weekend. I was putting 50-150 miles per week on the bike and loving it! The downside was that it needed constant maintenance. About every 50 miles of commuting I would need to adjust the derailleurs. Really torqueing on the pedals would impart enough flex in the chainwheels to hear and see the chain rub on the front derailleur. Riding off-road was a harrowing experience, with the shock barely keeping the front tire connected to the trail on rough downhill sections. I had more than a couple white knuckle descents struggling to hold on to the handlebars on faster parts. Still, I wouldn't give up the bike for anything.
After one trail ride where some chain suck led to a bent chainwheel, I looked for alternatives.
I found a full Shimano XT 3x9 speed drivetrain kit at Blue Sky Cycling for a good price. It included a new 11-34 casette (rear gears), rear derailleur, bottom bracket (bearing that supports the cranks), cranks, chainwheels, chain, front derailleur, and shifter pods. This would be a nice upgrade from the parts on the bike, which were 3x8 speed with a 12-32 cassette. The new gears would be better for both fast commutes and for steep climbs.
I also looked at what fork Cannondale put on the highest end Trail SL1 model. Cannondale uses a nonstandard steerer tube (straight 1.5"), so there's a very limited selection available. It ends up Cannondale uses a Rock Shox Recon Gold TK 80mm unit, which I ordered from Bikewagon for $300.
All the parts arrived a few days after ordering -- a good experience from both online retailers. The XT parts are just gorgeous. They have metal where my old components had plastic, and the metal is of a finer quality. The cranks and bottom bracket are super stout, and the chainwheels have a precision that I haven't had on a bike.
It took all my self control to not just dive in and take the bike apart and put the new stuff on. I needed a working bike for a triathlon I was doing that weekend. Friday night, I wasn't sure if I was more excited about the tri or about being able put all the new stuff on the bike afterward!
Replacing the components went without a hitch. I had been reading and watching videos on how to replace and adjust the various parts, and I was ready. Of special note were Sheldon Brown's very well written how-to articles on his site. This YouTube video was helpful for seeing how easy replacing the bike fork was. I also amassed the special tools needed for the job -- a crank puller (for the old cranks), Hollowtech II bottom bracket tool, cassette tool, chain whip, and chain breaker tool.
I got the new components on the bike and adjusted per Sheldon Brown's instructions. The new fork has an air-spring that needed to be adjusted for my weight. A helpful guy at Hyland Bikes down the street helped me find the right inflation pressure for that (about 130psi). He also confirmed the damping setting on the fork, which the old fork didn't have.
After a week of commuting (85 miles) and a trip up and down Mt. Allison, I'm super happy to have done this work on the bike. The bike shifts crisply and flawlessly. There is absolutely no flex in the cranks, and no wobble in the chainrings. The front fork is plush where the old one was jarring. While I haven't set any records on the commute yet, I took more than 10% off my best time up Mt. Allison with the new setup. The descent from Mt. Allison was drama free, almost like someone cleared all the rocks off the trail. Not once did I think my hands were going to come off the handlebars. Sweet!
The XT components are more than a pound lighter than the stuff it replaced. The shock is also more than a pound lighter than the one that came on the bike. All in all this cut almost 10% off of the weight of the bike. I can feel it accelerating or picking up the bike to lift the onto the CalTrain.
The money I put into the bike is roughly equivalent to just purchasing the high-end Trail SL1 new. The front shock is the same, but the XT components on my bike are better quality than those on the SL1. The experience from doing all the work myself has its own value. Now I know what all those little screws do on the shifting mechanisms, and can keep the bike in super shape now.
So for anyone with a Trail SL4, know that these upgrades are not only possible, but pretty easy to do yourself!
ps, I also trued my wheels this week after watching this excellent video.