Wednesday, January 10, 2007

Equipment - Deep Carbon Rims

One of the things I've been obsessing about are the wheels I use when I both train and race. I've always thought of the wheels as a mental "race or train" equipment change. Almost everyone had a set of "special" wheels when I raced. At first they were simply lighter wheels, maybe with a lower spoke count. But as the very expensive aero wheels came into vogue, many racers have significantly more aero wheels set aside for racing.

The problem with saving the aero wheels for just races is that you end up with a bike that handles significantly different on race day. Aero wheels present a much taller profile to crosswinds, creating a rudder-like effect.

In the rear that's no problem - the rear "rudder" stabilizes a bike and makes it much easier to hold in line. I've done some road races with very fast descents with a deep profile rear wheel and a normal box section front wheel. My highest recorded speed (calculated through rpms and gear) occurred with such a setup when I sprinted at the top of the big hill in the Fitchburg road race stage and tucked, disregarding the marshals' warnings to slow down. When I slowed and started pedaling, I spun up to 160 rpms before I realized I should coast a bit more. At that time I was going about 64 mph. The aero rear wheel made the bike feel incredibly secure and I never had a moment of fear or doubt in that descent.

On the other hand an aero front wheel wants to flop around. It makes the bike handle so differently that it forces a rider to actually steer the bike as opposed to simply leaning it a bit. Since the front wheel is more significant aerodynamically than the rear, a racer will want to use an aero front wheel if they own one. I'd skip the aero front wheel for any super crazy descents in gusty conditions but around here, and in California, I can't think of any crazy descents like that.

My favorite wheels are currently the Reynolds DV46Ts, 46 mm tall carbon tubular rimmed wheels. They are very light, reasonably aero, and laterally quite stiff.

However they are all carbon, including the brake surfaces, and ideally I'd be using carbon specific brake pads when using the wheels.

Of course the problem is when I train because I normally train on aluminum rimmed wheels. Those regular brake pads get loaded up with bits of aluminum and dirt, fine on an aluminum rim but not that great for a carbon rim - the bits of stuff embedded in the pad wears out the rim sidewalls. So I need carbon specific pads when using the DV46s. This means I have to change pads out each time I race.

This isn't ideal.

I went through a lot of thinking and experimenting with power things (the PowerTap and then the SRM) and wheels. I decided that if I were to train with power, I'd want to be able to race with power too. I couldn't afford to set up too many wheels with PowerTap hubs though, and some wheels like the TriSpokes simply aren't PT compatible. Combined with a desire to significantly stiffen up the frame, this led to the purchase of one SystemSix SRM equiped bike (it has the BB30 bottom bracket shell and Cannondale's rightly earned reputation for making very efficient frames).

This didn't solve my aluminum training rims versus carbon training rims though. So I sold off a few sets of aluminum rimmed wheels, including the beautiful Fulcrum Ones that came on the bike, and bought a set of kindly used Reynolds DV46Cs. The "C" stands for clincher.

Since both the DV46Ts and DV46Cs are made by the same company, and they share generationally similar hubs (they've since moved to DT hubs from the Chris King ones), the wheels should swap spots with no problems. With similar profile rims the clinchers should handle just like the tubulars as far as wind and general behavior is concerned. And of course they both require brake pads specifically designed for carbon rimmed wheels. I'll be able to keep the carbon specific pads on all the time and not worry about changing them out each time I race.

I'll be using the wheels probably tomorrow for the first time, or maybe this weekend, indoors for now. Maybe in a week or two I'll be on the road with them. I know I need to ride them a few times before I go to California so I have three weeks to experiment with them.

As an aside I took the opportunity to weigh the wheels using my new Christmas gift scale accurate to 0.1 grams (this accompanied the bike scale so I have both). The wheels included a rim strip alternative, little rubber plugs that close up each spoke access hole. I didn't remove them but the wheels (no skewers) weighed almost exactly 660 g for the front and 865 g for the rear. Nice and light (albeit not the lightest) and it still has a deep rim profile.

Even though the wheels came with virtually new Continental tires, I also bought a bunch of Michelin Krylion tires, 700x23. I replaced the Contis because, frankly, I'm not impressed with them. And I really like the Michelins, at least the durable ones. I'm tired of flatting on training rides and I'd really like to move to a slightly nicer tire compared to the super reliable but very heavy Schwable Blizzards (wire bead tires). I rode with my friend and former teammate during my San Diego training camp who had Krylion-like Michelins and on a day that I got two flats (a sort of record) he got none. I flatted on a different day and of course he did not. So Krylions it was.

I'll be mounting these tires up, installing some appropriate cassette (11-25), and using them both on the road and on the trainer to get used to them. And, when I fly off to San Diego for my 2008 training camp, I'll be packing a set of carbon clincher wheels.

Then we'll see how my training goes!

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