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Technical Q&A with Lennard Zinn – Time to replace?

  • By VeloNews.com
  • Published Jun. 3, 2008
  • Updated Sep. 28, 2010 at 4:48 PM EDT

By Lennard Zinn

Lennard Zinn

Photo:

Mix-and-match
Dear Lennard,
At one time I read in your column that you can change Campy 9-speed ergo shifters to 10-speed. Is this true and what are the details?
Guido

Dear Guido,
Yes, it is true except for the first year of 9-speed Ergo Power shifters (Record with aluminum levers). You simply replace the 9-speed index gear inside with a 10-speed one. It is obviously too complex to go into the details here.

All of the details are in “Zinn and the Art of Road Bike Maintenance,” as well as in “Zinn’s Cycling Primer: Maintenance Tips and Skill Building for Cyclists.”
Lennard

When to replace?
Dear Lennard,
I have two Shimano 10-speedd groups: Dura-Ace and Ultegra. I’ve put about 3000 miles on both groups (I ride my Ultegra bike a lot more in crits and early season training), but I’ve noticed, aside from the shifting, that my pedal stroke seems “easier” and more supple with Dura-Ace.

So, I have a few questions for you:

1) What’s the average lifespan of Dura-Ace and Ultegra bottom brackets? Do I need a new Ultegra bottom bracket?
2) Is there any easy way to determine when they’re about to go (other than mileage)?
3) With the old spindled bottom brackets you could rotate the bearings by hand and “feel” the drag/crunch/friction indicative of a need for a new bottom bracket. Now, it’s a guess based on “ease” of spinning the cranks, and that can be dependent upon bearing load?
4) Do you know the bearing-loading values for Dura-Ace and Ultegra bottom brackets (would I use a torque wrench for that)?
5) Have you heard of or had experience with the bearing overhaul kit, which I believe is made by Phil Wood?
Mark

Dear Mark,
I’ll answer your questions in order:

1) It really depends on usage. In spring classics on pro teamsriders compete in horrendous weather on awful roads. When you combine that with mechanics using high-pressure sprayers to clean them, a bottom bracket may only last about two weeks. For most people, well over a year.
2) No.
3)Yep, you got it.
4) You turn the adjuster to create as little as possible bearing preload while eliminating lateral crank movement. That is the downside of Shimano original integrated cranks relative to Truvativ GXP; the consumer side-loads the bearings, and even if they do it right, it’s still a side load in a bearing not designed for it.
5) I have one and like it. I also have the Enduro tool, which is similar and works similarly, except it uses a threaded bolt to push the bearings in and out. It’s great. I wrote about its use in the current print issue of VeloNews regarding upgrading steel bearings with ceramic bearings. You can press out the old bearings and press new ones into the external bearing cups. There is a similar tool for BB30 cranks.
Lennard

Regarding rolling resistance of clinchers v. tubulars discussed in a prior column:
Dear Lennard,
I suggest you look at biketechreview.com. The range of the Coefficient of Rolling Resistance (Crr) for tires in the test, performed on a PVC drum, are similar to the range of Crr for clinchers and tubulars in the Chester Kyle study, published in Bicycling, May 1985. The Kyle study was done on smooth asphalt and low speed trike.

It is obvious that the steel drum used in the Tour magazine study magnifies the differences between tires, the question is how much. Tubulars do not perform well on a steel drum because of the small contact area and the resultant squirming or glue compression. The difference on the road is minimal. In a test done by Triathlon magazine (September 2006), the same six sewups, eight clinchers were tested on both a concrete indoor track and a steel drum. After adjusting for tire load and speed, the range of variability (defined in watts) for the six sewups on the drum was 2.24 times higher (my calculation) than on concrete. For clinchers the range of variability was 1.76 times.

Bottom Line: “Rolling resistance is very close on smooth road surfaces between clinchers and tubulars. Individual tires of either group may have better or worse rolling resistance”.
Terry

Regarding power calculations:
Dear Lennard,
I “borrowed” this approach from Ron Cutler’s Etape du Tour site :

Power (Watts) = 2 x Weight(lb) x Speed(mph) x Gradient (as a fraction)

For example, suppose you and your bike weigh a combined total of 200 pounds and you want to climb a 7.5-percent gradient at 5mph.

So in our example we get:

2 x 200(lb) x 5(mph) x 0.075(gradient) = 150 (Watts)

This formula will only work for low speeds less than 10mph when rolling resistance and wind resistance are small. Also bear in mind that you need to consider a power level that is sustainable for over an hour.

It’s a really simple approach and easy to use and, although that factor of ’2′ seems improbable, I’ve worked through the math, and it’s plenty close enough.

Ron has lots of calculations of the power needed to maintain a given speed on the various climbs in the stage used for the Etape; he’s a real enthusiast.
Stan

Regarding orthotic construction from a previous column, I received some feedback about different approaches:
Dear Lennard,
I am a podiatrist and the pedorthotist’s response to proper casting technique for custom orthotics is off-base.

Semi-weight-bearing casting defeats the purpose of creating a properly supportive device. It’s difficult to be consistent between patients when utilizing this technique and one should simply use a heat moldable device if this approach is to be used. Yes, the foot compresses and the “arch” lowers and if done properly a non-weight-bearing casting simulating weight bearing by slight loading of the foot in its “neutral” position is the correct way to cast a patient.

Instructions can be given for “posting” of the devices if additional correction is needed. The foam impressions are a quick and easy way to cast but simply does not capture the true simulated semi-weight-bearing that is needed. Also, full-length devices may be appropriate, but if room is needed in the toe box area, a 3/4 cut top cover can be applied to the device without sacrificing any support supplied by the orthotic.
S.C. Murphy
DPM

Dear Lennard,
Thanks for addressing the orthotic question. I enjoyed the article and comments by Russel Bollig.

No doubt he has the experience and athletes to stand behind what he says. Because I’m a cyclist and a health provider, I can appreciate the value of orthotics in a cycling shoe. You might say it’s the reason I’m still training and racing.

I would, however, like to add a couple comments. I’ve been making cycling orthotics for a few years now using a neutral, non-weight-bearing cast, which has benefits worthy of mention. In my experience it’s not so much about the arch as much as it is a combination of addressing the forefoot/rearfoot relationship, as well as the arch.

The craftsmanship you mentioned required to modify a positive cast’s arch to address soft-tissue displacement really isn’t a difficult task for an experienced tech, as it involves much less guesswork. I don’t have any issues with this step, especially because there are so many benefits to a non-weight-bearing cast.

Because the forefoot/rearfoot is better captured with non-weight-bearing casts, it’s much easier to post the forefoot accordingly for the patient’s needs. Proper forefoot alignment is what in my experience really makes the difference in proper knee alignment while pedaling, also the basis for Paul Swift’s BigMeat wedges.

For a more complete article, please read a recent article I wrote.
Dr. Rich Cimadoro


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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