Technical Q&A with Lennard Zinn: More crank mail

Technical Q&A with Lennard Zinn: More crank mail

Technical Q&A with Lennard Zinn: More crank mail

By Lennard Zinn
VeloNews technical writer
This report filed December 2, 2003

More compact issues
Dear Lennard;
In response to your Q&A about compact cranks - I know that Stronglight makes chainrings in a 130mm bolt pattern that will fit Shimano cranks in sizes down to 38T. Do you know of any companies that make rings in the 34-36T range in a 130mm size? As much as I would like to save money and just buy new rings, swapping out my inner ring from a 39 to a 38 isn't enough to justify a change. If I want an inner ring smaller than 38, is my only option to change the whole crankset? I'm already at 12-27 in the back.
Barry

Dear Barry;
You cannot fit any smaller than a 38T on a 130mm BCD crank. Measure the diameters; you'll understand. The bolts would be higher than the teeth.
Lennard

The joy of small rings
Dear Lennard;
A comment about the article on the FSA chain ring sizes (50/34). I live in Sonoma County CA where many roads are steep - 12 percent or greater. I have been riding a Ritchey 'Swiss cross' crank 48/34 with a 28/12 cassette for six years. It is great. I don't have to carry an extra ring or worry about an extra shift. It is prefect except when you have a huge tail wind.

I will look into this other crank as well. I know I am nobody to quote, but if you do any kind of steep climbing this double ring setup is the way to go.
Paul

Dear Lennard;
Just saw your Q&A regarding small chainrings on cranks. I am a 50-year retired mechanical engineer, career spent racing motor vehicles, 800 mile a month road cyclist. I've been testing the FSA crank for a couple months over hill-and-dale in California's wine country, and used for the Mt. Diablo Challenge race. I have 34, 36, & 38 inner rings, FSA 50, with TA 52, and 54.

I have used every conceivable ring combination with excellent results, no problems, using Cycle Dynamics cogs from 11 to 28 in various combinations and a Campy 26/29 pair for the toughest training climb in the county, a hill I never made the summit of with 39/29, never made it past mile marker 3.2 of 5.0!
Tom

A question of conversions
Dear Lennard;
In last week's column, you discuss the advantages of converting back to two chainrings. I also am considering this change, but have been advised by bike shop techies that "many" parts would have to be changed. I'm wondering if they are really just interested in selling me more stuff. What is the proper way to convert from triple rings to double rings, assuming I want to save money by reusing as many parts as possible?

I currently run Shimano 105 triple (9-speed STI). I'd like to simply remove the "Granny" ring, and swap the derailleurs with older two-ring gear from my winter bike (RX-100 7spd downtube). Would this provide the performance advantages you're talking about in terms of shifting ease? Would it be at all compatible? What other components would need to be changed to make this system work?
Thomas

Dear Thomas;
It should work, given that Shimano has not changed the cable pull per shift for the rear derailleur. However, the fact that the rear derailleur cage on a 7-speed is so much wider makes the likelihood of snagging it on a spoke much greater. Make sure that inner limit screw is adjusted right! You could also have some lost performance due to chain slop within the cage. The front derailleur cage is also a bit wider, but that will be less likely to cause you problems. You can try it, though, and upgrade one part at a time to get the performance you are looking for.
Lennard

Big, small or medium, how fast to pedal?
Dear Lennard;
As I read your 50/34 debate I keeping wondering with respect to the differing chainring sizes, what is the effect on leg speed (and power) in maintaining a given speed? Is it correct to assume that no matter what gearing you use the power to hold a given speed is the same and the only thing that varies is the amount leg speed (RPM) required to attain it?

What does this mean to the cyclist to ride faster/farther?
Jim

Dear Jim;
Yes, maintaining the same speed with a lower gear does mean a higher leg speed. And as long as the speed is the same for the same rider and bike under the same conditions, then the power is the same. (To be completely accurate, there will be slight power differences due to differences in bearing and chain friction at different RPMs as well as variation with RPM in internal resistance in the rider's muscles and joints. These effects are so small that they can usually be ignored, however.)

As the power is the same, the peak forces are lower at higher RPM, since less work needs to be done on each pedal stroke to maintain the same power.

This is the concept behind Armstrong's use of high cadences; lower peak loads should result in less muscle fatigue. On the other hand, physiology studies virtually always show that the cardiovascular demands are higher at higher RPM (i.e., the heart rate goes up). Furthermore, a rider with big, heavy legs may actually have to produce more power to maintain the same speed at high RPM in order to keep them spinning around so fast. So there is a tradeoff, and this explains why all of the other top cyclists have not adopted Armstrong's cadence.
Lennard

Off-road float
Dear Lennard;
My question has to do with my quest to find the perfect free float mountain bike pedal. On my road bike I ride Speedplays and my knees love every minute of the non-centering free float. My mountain bike is a different story. I currently ride a pair of Time ATACs. The amount of float is fine, but they seem to want to center the cleat. It's time to get a new pair of mountain bike pedals and I was wondering how I can find out which ones have truly free float. The manufacturer literature always says how much float their pedals have (I don't need very much really), but nowhere do I see it stated whether the float is centering or free. The only ones I know of that claim to have free float are the Speedplay Frogs, but I have heard nothing but bad things about their set, durability, etc.
Izaak

Dear Izaak;
In my own experience, Shimano's float on the M959 pedal is not centering although it has a smaller float range than the Frogs. Time ATACs and Crank Brothers Eggbeaters and Candys do center the foot. Over time, as the cleats wear, however, this becomes less pronounced.
Lennard

Shutting up my squeaky pedals
Dear Lennard;
Any suggestions on the best lube to quiet down a pair of Shimano 959's.

They were awesome until they got soaked last year. I've been hitting them with silicone spray, which lasts for a few rides wet or dry, but whatever was on them when they were new lasted for months until they got wet.
Steve

Dear Steve;
I thought I would go to Shimano on this one:
Dear Steve and Lennard;
In regards to the binding mechanism of the PD-M959, the fluorine is impregnated into the metal as opposed to being a basic coating. This ensures the claws will maintain their performance for the service life of the pedals. Having spent hundreds of hours on these pedals in all types of conditions, I don't believe the noise is being caused by lack of fluorine.

Most likely, there is a maintenance issue that needs to be addressed or the cleat has worn and needs replacement. Cleat replacement is signaled by a loose interface with a clicking noise (typically in the negative stroke of the pedaling revolution).

Pedals are one of the most overlooked components when it comes to maintenance. The 959, due to its minimalist design for shedding mud, has a highly exposed tension mechanism that needs to be lubricated regularly by applying a drop of lube to each spring (four per pedal). Also, the 959 has a completely serviceable axle assembly that is easily removed by using a 17mm open ended wrench. This will allow application of fresh grease and adjustment to the cone and ball assembly. Lastly, check the interface of the rubber sole of the shoe and the face of the pedal. Much like a shoe on the floor of a basketball court, the sole of the shoe can rub on a smooth spot on the pedal and create noise. Using a cotton swab, conservatively dab grease to these points of contact to eliminate any squeaking.
Jason W. Leith
Bicycle Components Division
SHIMANO AMERICAN CORPORATION

VeloNews technical writer Lennard Zinn is a frame builder (www.zinncycles.com), a former U.S. national team rider and author of several books on bikes and bike maintenance including the pair of successful maintenance guides " Zinn & the Art of Mountain Bike Maintenance" and "Zinn & the Art of Road Bike Maintenance."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.