650c Project Bike - 2

This is part two of our 650c Project Bike – if you missed part one, it is located HERE.

So far, we’ve covered the overall concept, the fit details, and some of the component choices. This article will round out the rest of what you need to know, along with my impressions after several weeks of riding this crazy small-wheeled bike.

Build Process

As-expected with such a simple bike, the build process was smooth overall. One thing’s for sure – Serotta knows how to pack a frame:

The most challenging part was figuring out my handlebar situation, as we discussed in part one. Stack the pads? Flip the stem? I had almost a full day of fiddling, changing, bolting, and photographing, until I finally reached my desired setup.

Of course, that also includes cutting the steerer tube. When setting up any bike with a new-to-me aerobar (regardless of wheel size), I usually end up cutting the steerer tube twice. Once it’s cut, you can’t go back.

I also had to chop a bit off of the Vuka Alumina extensions:

Overall, I quite like the Zipp bars. The arm pads are outstanding, and the Service Course CX bar tape is my all-time favorite. I do wish they offered the base bar in more than one width (they offer road bars in four widths), but the clip-on is about as adjustable as they come. Note that all of the adjustability means that you WILL spend more time setting it up. If you change one thing, it usually affects something else. After much trial and error, I ended up with my arm pads in this position:

There is a compromise with the arm pad adjustment. The wider you place the pads, the more they must angle up. In the photo below, the left pad is in the third position, and the right pad is in the fourth position. I wanted my pads wider than position three, but didn’t like the high angle of position four. Instead, I moved the clip-ons out wider and angled the extensions towards each other. The older Vuka Clip had a flat base beneath the arm pad carriers, and did not suffer this problem (they weren’t as adjustable overall, however).

For brake levers, I used the oh-so-awesome Shimano Dura Ace carbon levers. These things improve the feel of a weak caliper – and when paired with the Dura Ace 9000 calipers, they make for a dreamy downhill experience.

Serotta offers the ability to customize your fork rake. Given my desire to match my 700c geometry bike as close as possible, I opted for a 40mm rake. The front-center was already a touch longer than the 700c bike, and a longer rake would have required a slacker head tube angle – resulting in an even longer front-center.

I chose Cane Creek’s simple 40-series headset for steering duties. In the past, I’ve been a big fan of their S-3 model. The 40.EC34 is the modern equivalent for 1 1/8” steerer tubes. The bearings slip right in and out, so replacement is super easy.

As we showed in Part 1, I opted for a third set of bottle cage bosses on the down tube. The weight penalty is nil, and it’s nice to have the option for carrying extra fluid (I usually have a camera and/or lights parked between my aerobars). I went with the Sampson EZ Cage because they work well and perfectly match the bike’s old-school look:

Clearance is tight between the third cage and my big ol’ 56-tooth chainring:

One thing that really excited me was tire choice. Bontrager advertises a 25mm version of their 650c Race Lite Hard Case tire, and sent some along for our project. I wanted something tough, and am a fan of larger tires. I’m not aware of anyone else that makes a 25mm wide tire in 650c diameter.

Unfortunately, my party got pooped when I measured the tires with a caliper. At 100psi, they measured 23.3mm on the 15mm internal-width Mavic Open Pro rim. They're still nice tires and have yet to flat; the compromise is that I run about 10psi higher than I would if they measured 25mm.

Ride Impressions

Now that I’ve spent time on both 650 and 700c – with the same fit coordinates, saddle, crank length, and so on – what’s the deal? Can I tell a difference? Is one faster than the other?

My first impression was, ‘It rides like a bike.’ It works. I’m not someone who is short and needs 650c wheels to achieve my fit coordinates, so that part of the equation is out. In terms of the wheels themselves, they feel quite similar to 700c. It’s impossible to say whether some of the difference I feel is due to the wheel size, or the small geometry changes – such as a slightly longer front-center, and a wheelbase that isn’t identical to my 700c bike.

I will say this: I like the way the bike handles. I actually like it more than my usual 700c bike. I just cannot say with absolute certainty which features and attributes caused this. I can, however, take some educated guesses:

-Down extended descents, the bike feels very stable. For now, I’m chalking this up to the longer front-center and slightly longer trail measurement than my 700c bike. It also seems to ‘pivot’ nicely while taking corners; my take is that this is due to the bike’s lower center of gravity – due to the smaller wheels (the axles are 25mm closer to the ground than a 700c bike). Once you commit to a turn, the bike holds its line very well.

-Acceleration. While I did not do any controlled tests, the bike seems to accelerate quickly – with near-equal gearing compared to the 700c ‘control’ bike. I’m chalking this to 1) potential placebo effect and 2) the no-argument fact that 650c wheels are always going to be lighter than a comparable 700c wheel. There’s just less wheel.

-Climbing. Similar to above. One thing is for sure – this bike is lighter than my 700c bike. The wheels, tires, and tubes are all lighter. The other part (and this is cheating) is that the frame uses thinner-walled tubes and is a little lighter than my 700c bike. Perhaps coincidentally or perhaps due to fitness, I set my best-ever time up our local ‘test hill’ on this bike, which takes about 10 minutes and is a steady 3-4% grade. That was also with the shallow and non-aero training wheels.

-Crosswind. This is one area that 650 is going to win every time. This is also something that is not part of the mountain bike 26-inch vs 29-inch debate. 650c wheels have less surface area than 700c, resulting in a super-stable front end on the bike. There’s this race called Kona, which has historically been dominated by women riding 650c (or smaller) wheels – and I think it’s no coincidence. On windy days, this bike is noticeably less affected by crosswind than my ‘normal’ ride.

Does this mean I’m going to switch all of my stuff over to 650c? Am I through with 700c? Far from it. A big factor is that my job is this, and I have to test a lot of 700c gear.

I would strongly consider moving to 650c for my personal bike if I could get two things: 1) A real 25-27mm training tire, and 2) more chainring options. The best part of 650c, in my opinion, is that it makes travel easier. Everything is smaller and lighter.

Some of our readers suggested that we go back to ‘funny bikes’ with a 650c front wheel and 700c rear wheel. That would certainly remove the issue of not enough gear choices. Some say that its properties of aerodynamics and stability would trump dual-650c wheel bikes. Who knows – maybe that’s the future. I’m tempted to try it for fun, but the realities of racing and travel are prohibitive – carrying two spare tubes, getting spare parts, etc.

What do you think? Do the benefits of 650c sound appealing to you (light weight, crosswind stability, handling, bike fit)? Are there any die-hards out there who refuse to give up their 650c steeds?

One thing’s for sure, I’m going to enjoy the heck out of the one I’ve got for the rest of the season.

Full Specifications:

Frame: Serotta Legend titanium, custom geometry
Fork: Serotta carbon
Shifters: Shimano Dura Ace 7900 bar-end
Rear derailleur: Shimano Ultegra 6700 short cage
Front derailleur: Shimano Ultegra 6700 braze-on with FSA 34.9mm clamp adapter and Rotor 6mm/4mm angled shim
Chain: Rotor SL101-Ti 10-speed
Cassette: Shimano Ultegra 6700 11-28 10-speed (training)
Cranks: Rotor 3D TT/Aero 130BCD, 165mm with 56/42 TT Q-Rings
Bottom Bracket: Rotor BB1, English threaded
Pedals: Shimano Ultegra
Brake calipers: Shimano Dura Ace 9000
Brake levers: Shimano Dura Ace
Base bar: Zipp Vuka Alumina, 40cm C-T-C
Aerobars: Zipp Vuka Alumina, ski tip extensions and 10mm risers
Bar tape: Zipp Service Course CX, white
Stem: Zipp Service Course SL, 6-degree, 100mm length
Seatpost: Zipp Service Course SL, 27.2mm, zero setback
Headset: Cane Creek 40.EC34
Headset spacers: Wheels Manufacturing alloy
Saddle: ISM Attack
Bottle cages: Sampson EZ cage

Training wheels:
Mavic Open Pro 650c rims, 32-hole
DT Aerolite spokes, black
DT brass spoke nipples
Powertap 32-hole front hub
Powertap 32-hole G3 rear hub
Velox cloth rim tape
Bontrager Race Lite Hard Case 650x25c tires (23.3mm measured)

Race wheels:
Hed Jet 60 (650c)
Hed C2 650c rim tape
Schwalbe Ultremo ZX 650x23c tires (24.0mm measured)

All images © Greg Kopecky / slowtwitch.com