Ask Nick: Di2 on the cobbles, road/’cross conversion and stem fitting

Editor’s Note: VeloNews tech editor Nick Legan is a former ProTour mechanic who most recently wrenched for Team RadioShack at the 2010 Tour de France and elsewhere. His column appears here every Thursday. You can submit questions to Nick at asknick@competitorgroup.com, and be sure to check out Nick’s previous columns.

Q.Nick,
I was curious why Cancellara and Radioshack chose to run Dura Ace 7900 as opposed to Di2 at the cobbled classics. Do you know why? Is the Domane not set up for electronic shifting or perhaps weather was a concern?

— Brian

A. Brian,
The Domane is both Di2 and mechanical ready and Radioshack is not alone, actually. I spoke with several team mechanics about the decision to use mechanical groups.

They do it because the 7900 mechanical shifters require more input to shift. Over the cobbles, many riders were experiencing accidental shifts. The Di2 shifters are too sensitive for some riders. Others had no issue. It may be the way different riders hold the lever or an issue for larger-handed riders. But that’s why.

Q.Nick,
I know that this is about six months early, but I am very excited about the possibility of racing cyclocross for the first time this fall. I have difficulty though, as I am a college student, so funds are a bit short. I do, however, have a 2009 Madone 4.5 that I splurged for in high school and love more than any other possession. I cannot afford to shell out for even the cheapest ’cross bike, so I thought I may try to convert this into one. The biggest questions I have are about the durability of the carbon frame under such conditions and the clearance for knobby tires in the frame. Overall, is there a way to take a high-performance (at least in my mind) road bike and turn it into a ’cross bike?

– Luke

A. Luke,
I hate to be the bearer of bad news, but I don’t think your Madone will serve you well as a cyclocross bike. It isn’t the durability of the frame that’s an issue in my mind, rather the lack of tire clearance.

The largest tire you’ll be able to run is a 28mm road tire and that won’t leave much room for mud (not that a smooth tire would perform well in those conditions to begin with). Additionally, even if you ran smaller tires, the brakes on your bike aren’t really designed for muddy conditions.

I was once a poor student athlete too. Any chance you can borrow a bike for the season? How about using a mountain bike? They are allowed at most cyclocross races as long as the bike doesn’t have bar ends mounted.

That’s the approach I, and many, took when first dabbling in cyclocross. Ask around; someone is bound to have an extra bike around. Get the thing cleaned up and tuned before you use it and then cleaned and tuned again before you return it (as a thank you!). Wishing you all the best. Cyclocross is a blast and your excitement is well founded.

Q.Nick,
I have a couple sets of wheels that are used in the professional peloton. One set are Easton EC90 Aero tubulars and the others are Mavic Cosmic Carbone SLR clinchers. I love both sets of wheels and both are bulletproof… but not waterproof!

I’ve raced both sets in the rain and find that when I go to clean my bike afterwards, they both have water sloshing around in the rims. I know that on the Mavics water gets in where the carbon spokes enter the rim (there’s a pretty large gap in the carbon fairing) but because they are clinchers it’s easy enough to remove the tires and vigorously shake the water out.

But with the Eastons, because they are tubular and the nipples are internal, it’s a real pain in the butt. How do the pros deal with this?! During a race there’s no drainage so you end up taking on water in the worst possible location — the rims! I can’t imagine pros wanting to race with extra water weight in their wheels. Do they drill extra small drainage ports into the rims? Thanks for your help.

– Donald Brew

A. Donald,
That is a problem. And you’re not alone is experiencing it. When I was a team mechanic I did indeed drill extra holes in wheels (with the permission of the wheel manufacturer). But I’m certain that if you did it yourself you would void any warranty on your wheels. That doesn’t mean you shouldn’t do it, but bear that in mind.

I also found that drilling the holes didn’t really help drain the wheels during a race. It helped after the fact when I needed to empty them. So racing in the rain means racing with water in your rims. It’s a bummer, but I’ve yet to see a good way to avoid it happening.

Another way to look at it is that few of us race back-to-back days in the rain. If you thought that were going to be a distinct possibility I would advise you to use the Mavic wheels. If it’s wet out, the aluminum braking surface on your Mavics can be a huge advantage. You can also dry them out more quickly. Alternatively, use one pair the first day, the other the second day. Not sure I helped much with your problem, but that’s all I’ve got. Maybe some commenters have ideas?

Q.Nick,
What effect does stem length have on a bike’s handling characteristics? I have heard that it is better to put a longer stem on a bike that’s a little bit too small for you than to put a shorter stem on one that’s a little too big (talking about road bikes, here). Why is this the case? How much leeway do you have?

– Jesse

A. Jesse,
That’s actually a fairly complex series of questions you’ve just asked. Ideally, you find a frame that fits you properly, instead of riding a frame that’s too big or too small. That said, geometry differences from one manufacturer to another mean that a given rider will use shorter or longer stems when changing bikes.

As far as handling, changing stem length will affect steering, but only a little bit compared to different trail numbers and wheelbases. Personally, I think that bottom bracket height has more to do with how a bike handles than most people realize. But I digress.

If you put a longer stem on a bike (everything else remaining the same), steering will slow down a little. Think of a tiller on a boat. The longer the lever, the more movement is required at the end of the lever to turn the tiller (or fork steerer in this case). To be more exact, steering will require more input.

But in reality the change isn’t too noticeable, not nearly as much as the change to your position. You’re much more likely to notice some soreness in your shoulders or back than you are in how your bike descends. (If you make gross changes, going from, say, a 10cm to a 14cm stem, you would notice it. But again, that’s not all that realistic.)

As soon as I say that though, think about this. If you put a longer stem on a bike, but then also move the saddle forward, handling could change because your weight distribution over your wheels has shifted forward. This could “speed” up your bike’s handling.

There is a suggested range of stem lengths for a given size bike that many bike fitters use as a guideline. Roughly, if a 54cm or 56cm frame fits you, anything from a 10cm to 12cm stem will give the best handling. Using something shorter will make the bike nervous. (This is especially true because short stems are usually run very high, putting a lot of weight on the rear of the bike and un-weighting the front wheel. Horror stories abound of front-end shimmy after a bike fit that feels great on the trainer.) The size range is usually proportional to the size of the frame. It’s not uncommon for 62cm riders to use 13cm or 14cm stems. Conversely a 48cm frame often fits best with a 9cm stem.

Recently in my column I wrote that riders should stop looking to pros for bike fit cues. And this is a good place to repeat that as I think the advice you’re receiving is based on pro rider worship instead of sound bike fitting thought.

Many pros are riding 13cm and 14cm stems. The reason they do it is because head tubes are getting taller. They must use these long stems to maintain reach while achieving their preferred drop.

But in the process, they are introducing a long, flexible stem into the equation. Riders often complain about a bike being too flexible, but then happily slap on a huge stem and never seem to think about the impact of it.

Jesse, I could go on, but I think instead I would advise you to find a bike fitter with a lot of experience. Being efficient and comfortable on your bike is more important that looking like a pro (not that I’m saying you are).