By Lennard Zinn

Better, for sure, but how much better?
Better, for sure, but how much better?

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Dear Lennard,
I was doing some light maintenance recently and playing with a few wheels. Out of curiosity, I wanted to compare “spin” time for a set of loose bearing wheels vs. another set having sealed bearings. The former were Campy Daytona hubs laced to Open Pros (never been overhauled since being built in 2000). The latter were Rolf Prima Elans with very low mileage. The loose bearing wheels kept spinning for some time after the sealed bearing wheels stopped. All things being equal, does this seem right? Also, does the “spin test” have much meaning when the wheel is not carrying a load?
Chris

Dear Chris,
You are experiencing what many a rider has groused about upon making the transition from loose bearings to cartridge bearings. Mainly I think you are feeling the seal drag, and, as you say, it is not under load. I think in actual riding conditions the difference is very small, but certainly, it is a real difference.

Technical Q&A with Lennard Zinn: The width difference between Shimano and FSA K-Force Light bottom brackets.
Technical Q&A with Lennard Zinn: The width difference between Shimano and FSA K-Force Light bottom brackets.

Photo: Lennard Zinn

I’ve never done a really accurate measurement of hub bearing drag, but we did do some tests on bottom bracket drag many years ago when Bike Testing Inc. was here in Boulder and making its shop available to VeloNews. With a load on the bearings, the differences were lower than spinning in the hand indicated, but the drag was definitely higher on cartridge-bearing bottom brackets with integrated spindles and external bearings than loose-bearing old-school square-taper bottom brackets.

On the other hand, gunk could get in those bearings more easily, although overhaul was easy.
Lennard

Dear Lennard,
It’s winter and I need to glue some tires for the coming season. My workshop is in my basement, which is a steady 50-52 degrees F. My question is: will the coldish temp have any adverse effect on the characteristics of the glue or should I just go for it? Is it okay to let the first few layers on the wheels and tires dry in these temps?
Adam

Dear Adam,
At the very least, it will take far longer for the glue to dry. The gluing job may not be weaker in the long run, but in the short run, yes. Can’t you bring it upstairs to dry after you put a layer of glue on?
Lennard

Follow-up from last week’s column:

Dear Lennard,
Your response to Dale’s question about reduced air resistance at high altitudes prompted a further question. In particular, you mentioned that track records have been set at high altitude. As a flatlander who has ridden a few times in the mountains of Colorado, my experience
suggests that the reduced oxygen availability at high altitudes more than offsets the benefit of reduced air resistance in producing speed.

I know this factor can be at least partly overcome through acclimatization, but can it really result in higher average speeds? I imagine the answer partly depends on the terrain, so let’s assume a
flat course. I am interested in evidence from historical performances and a back-of-the-envelope physics/physiology analysis.
Matt

Dear Matt,
There is certainly a break point in elevation above which individual cycling performance drops off, just as there is an elevation above which humans cannot sustainably live. I can’t remember what that level is, but there are no human settlements that have endured for the long term above it. (It’s certainly way higher than altitudes at which cycling records have been set; according to this abstract, the highest permanent settlement currently is a village in Peru at 5100 meter, or about 16,700 feet).

Similarly, there are different altitudes for different sports above which performance will always be reduced. In cycling events of a single individual against a clock, however, that altitude limit for improved performance is probably higher than for any other sport save alpine skiing, snowboarding, and the various competitions involving sleds. The higher the speed of the athlete, the more important wind drag becomes. In cycling on flat ground, unlike gravity-assisted sports, it is of course critical that the athlete also be able to breathe well enough to fuel his or her muscles in an endurance event.

Cycling hour records on the track have been set on outdoor tracks in Mexico City (2,240 meters, or 7,349 feet) and in Colorado Springs (about 6,000 feet.)

You usually won’t see Colorado Springs on the hour record lists because it was a woman — Jeannie Longo — who set it there.

Miguel Indurain attempted the hour record in Bogotá, Colombia (2,546 meters, or 8,355 feet) in 1995, and at the time one reason given for him falling short of Tony Rominger’s mark was that the altitude was simply too high. Although the aerodynamic drag was very low, there was insufficient air pressure for him to breathe effectively enough to go faster than he had when he had previously set the record in Bordeaux in 1994.

It should be noted that most of the recent hour records among males have been set on indoor velodromes near sea level; the lower altitude is a disadvantage but the lack of wind and predictability of conditions indoors is a benefit.

Obviously, swimming records will always be set at low altitudes due to the absence of aerodynamic drag as a factor; fueling the muscles with oxygen will always trump any small amount of wind drag of the arms above the water. On the other hand, speed skating records fell like rain in the 2002 Winter Olympics in Salt Lake City (4,327 feet). That sport requires breathing just as much as cycling does, but it also incorporates speeds high enough that there is a benefit to going up in elevation.

In endurance running, marathon records are always set at low altitude. In high-speed running, however, some sprinting records have been set at altitude; the combination of lower air drag and the fact that it’s an anaerobic event combine to produce higher speeds despite the fact that few top-notch events are held at altitude.
Lennard

Follow-up from King Cycle Group regarding my comment on bottom bracket compatibility:

You can use FSA K-Force Light road cranks in a Chris King bottom bracket, but it must be an MTB version:

Here is what I’ve experienced with our bottom brackets and the FSA K-Force light cranks.
We produce two different versions of our bottom bracket based on Shimano specifications. While they do use the same bearing with a 7mm width, they use two different width cups, with the mountain version being narrower. As stated by Dae from FSA the Shimano standard road bottom bracket is too wide to accommodate the spindle length of the FSA K-Force Light cranks set. Since our road bottom bracket is built around the Shimano design, it will also be too wide. With that being said, our mountain-specific bottom bracket uses cups that are each 1mm narrower than the road design. So based on these pictures from FSA as well as the installations that I have completed the FSA K-Force Light cranks can be installed with our mountain bottom bracket in place of the road specific unit on a 68mm bottom bracket shell.

Some caveats: some of our early mountain specific bottom brackets shipped with inner center sleeves that do not have an o-ring groove to accommodate an installation on a 68mm bb shell (since almost all Shimano mountain cranks sets have a spindle length that requires the cups to be installed with the proper spacers to mimic a 72mm bottom bracket shell and an E-type derailleur or chain guide). In that case the large o-ring on the sleeve will have to be removed and care will need to taken to be sure the sleeve installs concentrically or it will need to be swapped out for the new version which has multiple o-ring positions. Additionally, extra care should be taken in the chasing and facing of the bottom bracket shell to be sure that it meets the size specifications of the crank manufacturer.

On a side note, our bottom bracket bearing is an angular load bearing that does require preload to operate properly so the wave washer or rubber washer that is supplied with the crank set should be used and as the bearings break in the included Mylar spacers may need to be added to maintain proper preload.
Gabe Cabatic
Tech Warranty
King Cycle Group

Feedback on my recent column on tall cyclists:

Dear Lennard,
I am the same size as Steve (6’5″, 200+lbs.) and although it is not easy to find a good fit, someone our size does not necessarily require a custom. In fact, I have done very well over the years with stock frames and components. I recently decided to go back to carbon after riding an Eddy Merckx Team SC scandium (i.e. aluminum alloy) frame, which fit me very well. As you say, I found that most carbon bikes are available in very limited sizes. The solution for me was a 64cm Trek Madone 5.5. This size was new for 2008 and is engineered for bigger riders. It is by far the best fit I have ever had, and it is a monocoque carbon frame. Specialized offers a similar sized carbon frame in the Roubaix Expert model. Riders much larger than Steve and I probably need to be fitted for a Zinn or something, but there are viable options out there for guys as big as us.
Marco



Technical writer Lennard Zinn is a frame builder (www.zinncycles.com), a former U.S. national team rider and author of numerous books on bikes and bike maintenance including the pair of successful maintenance guides “Zinn and the Art of Mountain Bike Maintenance” – now available also on DVD, and “Zinn and the Art of Road Bike Maintenance,” as well as “Zinn and the Art of Triathlon Bikes” and “Zinn’s Cycling Primer: Maintenance Tips and Skill Building for Cyclists.”

Zinn’s regular column is devoted to addressing readers’ technical questions about bikes, their care and feeding and how we as riders can use them as comfortably and efficiently as possible. Readers can send brief technical questions directly to Zinn. Zinn’s column appears here each Tuesday.

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