Ask Nick: Endurance bike design, wheel balancing and more
In a previous column, you stated, “Personally, I think that bottom bracket height has more to do with how a bike handles than most people realize.” Can you expand on this?
While I have considered this when buying a mountain bike, I have never thought about it when buying a road bike. I guess I just trusted the manufacturer to have it right.
Bottom bracket height is one of the most overlooked items on a frame’s geometry chart. But it alone doesn’t determine how well a bike rides. It’s difficult to discuss frame geometry as what’s best for your needs won’t necessarily work for me, or even you later in life! But here are a few thoughts.
When I worked at Pro Peloton, we sold Serotta bikes (though the shop no longer does). Customers always raved about the way those bikes handled, especially on long descents here in Colorado. Instead of being nervous, the titanium and steel bikes that I was assembling were wonderfully predictable and still flickable and lively. I’m sure that other framebuilders were doing similar thing with their frames, but Serotta’s custom geometry for our customers was eye opening for me.
Many of those confidence-inspiring Serottas had bottom brackets that were a centimeter or so lower than equivalent race bikes. This lowered the rider’s center of gravity a tad and gave the rider a feeling of being in the bike instead of on the bike.
Race bikes have their bottom brackets positioned to help avoid pedal strikes while cornering. This isn’t as much of a concern for many of us. A lower bottom bracket helps make a bike more stable. Many endurance bikes have lower bottom brackets and I personally love how many of them handle compared to their racing cousins.
The way a bike handles has a lot to do with rider weight distribution. And that’s something that I feel many bike fitters are ignoring. I see a lot of cyclists riding around with tiny stubs for stems fitted well above their saddle. There is nothing wrong with having your handlebar in that position, but if you’re riding a bike that isn’t designed for it, you’re likely to have handling issues (think downhill speed wobble). What works in a stationary trainer doesn’t always work out on the road.
Brands including Specialized, with its Roubaix, created (marketed) the endurance bike segment with such positions in mind, but Specialized wasn’t the first to build a bike with a taller head tube and longer wheelbase to better accommodate non-racer cycling positions.
Much like the inventor of the mountain bike, I’m sure it’s debatable. But turning again to my personal history, I first saw taller head tubes on the Serottas I was building. (Again, not giving Serotta credit for being the first, just the first that I saw).
While I don’t yet need a taller head tube on my personal bikes, as an advocate for cycling, I applaud their adoption by so many manufacturers. Endurance bikes make cycling more approachable, more comfortable and ultimately, more fun!
Many members of the cycling media only point to head tubes when describing “endurance” bicycles. But the wonder of these bikes is not simply a longer frame dimension at the front of the bike! Most of them have lower bottom brackets (which also helps increase stack to the bar) and longer wheelbases, which keep a bike’s handling predictable, even with higher handlebars.
I’ve heard a lot of talk about wide tires and tire pressure as of late. Could you recommend a few tire gauges?
— Adam Kohn
I am a fan of tire pressures higher than zero, much like all cyclists. Experimenting with different pressures is all about consistency, though. It isn’t really about absolute accuracy. While I’ve certainly used tire gauges (more for off-road applications), on a day-to-day basis, I just always use the same floor pump. It gives consistent, if not perfectly accurate readings.
When I want to get more scientific, I use Accu-Gage’s high pressure gauge for road tires (they also make a Low Pressure gauge for pressures up to 30psi). I also have one of Michelin’s digital gauges and like it a lot. It’s compatible with Schrader and Presta valves and reads in psi, bar and kg/cm. I also use it on my motorcycle.
If a person had a limited budget and wanted to have the best combination of “weight & aero performance” for a set of wheels, would it make sense to buy a lightweight, small-rim-depth rear wheel and an aero-depth (e.g., 45mm or 50mm Zipp 303 or 404) front wheel?
I believe that having an aero wheel at the front would provide more aero benefit than one at the rear, although handling in stiff crosswinds would be impacted. A small-rim-depth, lightweight rear wheel would benefit on climbs when speeds slow and gradients increase. I’ve not ever seen this setup, so I’m probably missing something, but I thought I’d ask.
I ride a lot (>5000mi last year), and ride with the 20-22 mph lead groups at the 60-100-mile charity rally rides, but I know very little about the mechanical aspects of the sport. I just try to do my best with what I read and hear. Currently I ride a 64cm Specialized Roubaix Expert with Mavic Ksyrium Elite wheels (yes, I’m tall, 6’7” but not too heavy, 215-220lbs) but if there’s any chance of gaining a real mechanical advantage/improvement without breaking the bank, I’d be very interested.
I often advised riders to use exactly the wheel setup you describe when I was a mechanic. Danny Pate used to use a deeper wheel on the front and a shallower one on the rear to save weight. It makes perfect sense to put the most aerodynamic wheel where it will do the most good, on the front. And in the pro ranks, using the shallower rear wheel can keep a race bike at the UCI weight limit if the team’s aero wheels are chunky.
In Europe you’ll often see riders using the opposite combination. In my opinion, that’s because of two things. 1. Crosswinds, and 2. It looks cool (a.k.a. bad decision-making). The first makes sense. Crosswinds can be serious and staying safe is always a priority. The second is more prevalent than you may think.
Not all decisions in the pro peloton are made based on anything scientific or methodical. As an example, many pros run their stems slammed down on the headsets, but not because that’s what’s best for them, but because it looks cool. Peer pressure is a very real thing.
Back to your question, I think that’s a great idea. Try borrowing the aero front wheels of some of your friends for a ride. Make sure to install the appropriate brake pads and give them a go. See what you’re comfortable with on a windy day and what you can afford. Then make your decision based on that.
I recently had a discussion with a partner of mine, who is an avid motorcyclist, regarding wheels and he asked if I ever balanced my bicycle wheels. I told him that I have not and in fact never thought to do so. I asked around on my team and nobody balances their wheels. I know in cycling, tires and cassettes are changed more often than on a motorcycle and these will affect balancing and thus many don’t bother. However, after some thought I think it would be of some benefit to balance bicycle wheels, especially those deeper dish carbon wheels that may have a larger unbalance [sic] due to the longer stem. Do the pros ever balance their wheels? Do you know of an advantage to doing so? If so, how do you usually go about doing the balancing?
— Chad Billings
Your partner raises a good point. You wouldn’t think of driving a car or riding a motorcycle without balancing the wheels. There are reasons why it’s more important to do so on those motorized vehicles though, namely speed.
Both cars and motorcycles travel faster than the average cyclist. The number of wheel revolutions is very high and imbalance leads to shakes, shimmies and other vibrations.
Because the speeds of a racing cyclist are so much lower, we tend to focus on absolute minimum attainable wheel weight, instead of perfectly balanced wheels. But I do know of at least one professional rider who balanced his race wheels. He found them much more predictable when descending and didn’t mind the minimal extra weight. His mechanic attached small pieces of lead to the spoke, next to the nipple, to balance them. Adding only a very little bit of extra material in the right places led to a wheel that would spin for an extremely long time in a truing stand.
The only downside was that the mechanic had to rebalance the wheel each time a new tire was installed. But it doesn’t take long to do. I’ve experimented with the thin lead strips used by fisherman. They’re easy to wrap around a spoke and crimp to keep them in place. But in truth, I rarely bother.