You heard it here first, disc brakes are awesome for cyclocross. OK, maybe not FIRST, but I've been pushing for disc since about 2008, but the frame and fork selection was lacking. Currently components are catching on, but now they're behind the frames. With many manufacturers rolling out brand new carbon CX frames this year to add to their current aluminum setups, and component manufacturers flashing a glimpse here and there of hydraulic setups, we know this is the way of the future.
For my first full-fledged attempt at disc CX I went with the
Felt F65x. Why? It's the best thing that's readily available without going custom. The frame is very similar to the F55x, so I know it'll handle well. The geometry is dialed for me, so much so that my Independent Fabrication Cross Jester is based on the stock 57cm Felt cross bikes.
There's a lot going on with this build, so I'm going to take this in multiple entries. First, let's cover the bike, we'll cover the pros and cons of the build next, and later cover the performance advantages and disadvantages.
The F65x isn't the lightest bike I've ever owned, but with alloy clinchers, disc brakes, alloy cockpit, a Quarq, 2012 SRAM Red, bottle cage, computer mount, and set up tubeless this bike still came in under 19lbs. I assume a carbon equivalent with some light race wheels will come in around 17lbs, give or take.
The stock bike comes with a SRAM Apex/Rival build, Felt CX3R wheels, Avid BB5 brakes, and a nice SRAM S300 BB30 crankset. The rear is spaced at 135mm, exactly what I think will be the de facto spacing. The build is solid, and probably better than I would expect for a $1750 bike with such a nice frame.
The stock fork is a super-beefy Felt UHC model which offering some really great stiffness and a better than average ride quality. Off-road the bike tracks very well, though when overgeared and sprinting on the road I am able to make the rotors rub the pads occasionally. At some point down the road, I'll be giving the
ENVE Disc CX fork a try.
Off the bat I clearly made a number of changes. The 2012 SRAM Red is probably one of the first things many people will notice. I'm smitten with it, but you can
read my review on it here. The addition of a Quarq was of course necessary since I'm numbers-driven, but it's a swap from my other bike anyway. Seatpost became a Thomson because I just flat out trust their work. The stem is currently a Zipp Service Course SL until a Thomson Elite X2 comes in, and the bars are Zipp SLC2 Short and Shallow which have been with me for 3 years and on countless bikes.
I kept the stock BB5 brakes on board, primarily because I forgot to bring the BB7's in when building the bike. So far, the performance has been extraordinary.
Now let's talk about the wheel swap. I wanted to keep this build "reasonable", other than the Quarq and Red of course. I wanted to come up with a wheelset that can be put onto the stock bike and shed a nice chunk of weight, provide a huge performance benefit, and offer the best tubeless compatibility. I've been using
Stan's wheels since I started in mountain biking and have loved them ever since. This year I managed to ruin a few sets of rims, but I'm chalking it up to bad luck. From 2005-2011 I used either the 355 or Crest rim from Stan's with nary an issue. In 2012 I ruined 5 total rims. Bad luck or bad product? I don't know, but since that bad streak I'm back to pure gold with them.
Here's the beauty of the
stock Crest wheelset: for $530 you get a 1575g claimed (we've measured them to be far lower, but never higher) wheelset which shaves a full pound from the stock Felt CX3R wheelset. The Crest internal rim width is 21mm vs the stock wheels roughly 17mm width, which means much better grip from your tires. If you aren't familiar with why wide rims are better,
check here. The final HUGE bonus? Tubeless compatibility.
I'll cover the swap more in an upcoming post, but there is one positive that's coming close to being a negative: the wide rims have turned my Clement Crusade PDX 33 tires into a 37c monster! The grip is out of this world from a knobby 37c CX tire, but clearance is an issue. The fork is fine, tons of room. The rear seatstays are begging a 40c tire, but the clearance around the chainstays is tight with a tire this big.
The driveside chainstay on the F65x with the 33c tires and Crest rims is about 5-7mm or so. Clearance on the non-driveside chainstay is about 4mm or so. I'm fine with the clearance on the driveside until it gets really nasty, but it's close on the non-driveside. Of course, the bike comes stock with 32c tires on standard-width rims and offers ample clearance. It's not until you really push into a tire that's measuring over 37mm that clearance is even something to look at.
There are a couple of solutions to this:
1. Ride away. I gave the bike a few hard corners and a number of over-geared road sprints and never got the tire to rub. The photos make it look slightly worse than it is, but so far it's been fine.
2. Run a 32c tire. There are plenty out there, but the PDX is a favorite of mine.
3. Stan's probably has the best solution, the Iron Cross wheelset. Coming in about a mm more narrow, I think that'll offer the breathing room to make me feel just fine about running this wheel/tire combo on this frame. Plus, the name Iron Cross is just so damned good, you know!?
Tubeless setup with the Clement PDX, though not necessarily endorsed by Clement, was a breeze. Literally, mount one side of the tire, toss some sealant in, mount the other side, inflate. It was as fast as installing a tire with a tube. Now you can run lower pressure without worrying about a pinch-flat, get better traction, and severely reduce the likelihood of a flat.
There you have it. Disc CX is here and it's awesome. Review on the performance from the brakes and the wheels are coming soon. Until then, act now and get a disc CX bike. Before you know it manufacturers will have tons of wheel options for tubeless and tubular, the brake options will be plenty, and you'll wonder why we didn't make the transition sooner.....damn you UCI!
