Gear

Technical Q&A with Lennard Zinn: More crank mail

More compact issuesDear Lennard;In response to your Q&Aabout compact cranks - I know that Stronglight makes chainrings ina 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 130mmsize? As much as I would like to save money and just buy new rings, swappingout my inner ring from a 39 to a 38 isn't enough to justify a change. IfI want an inner ring smaller than 38, is my only option to change the wholecrankset? I'm already at 12-27 in the back.BarryDear Barry;You cannot fit any smaller than a 38T on a

By Lennard Zinn

More compact issues
Dear Lennard;
In response to your Q&Aabout compact cranks – I know that Stronglight makes chainrings ina 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 130mmsize? As much as I would like to save money and just buy new rings, swappingout my inner ring from a 39 to a 38 isn’t enough to justify a change. IfI want an inner ring smaller than 38, is my only option to change the wholecrankset? I’m already at 12-27 in the back.
BarryDear Barry;
You cannot fit any smaller than a 38T on a 130mm BCD crank. Measurethe diameters; you’ll understand. The bolts would be higher than the teeth.
LennardThe joy of small rings
Dear Lennard;
A comment about the article on the FSA chain ring sizes (50/34). Ilive 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 cassettefor six years. It is great. I don’t have to carry an extra ring or worryabout 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 theway to go.
PaulDear Lennard;
Just saw your Q&A regarding small chainrings on cranks. I am a50-year retired mechanical engineer, career spent racing motor vehicles,800 mile a month road cyclist. I’ve been testing the FSA crank for a couplemonths over hill-and-dale in California’s wine country, and used for theMt. 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 combinationsand a Campy 26/29 pair for the toughest training climb in the county, ahill I never made the summit of with 39/29, never made it past mile marker3.2 of 5.0!
TomA question of conversions
Dear Lennard;
In last week’s column, you discuss the advantages of converting backto two chainrings. I also am considering this change, but have been advisedby bike shop techies that “many” parts would have to be changed. I’m wonderingif they are really just interested in selling me more stuff. What is theproper way to convert from triple rings to double rings, assuming I wantto save money by reusing as many parts as possible?I currently run Shimano 105 triple (9-speed STI). I’d like to simplyremove the “Granny” ring, and swap the derailleurs with older two-ringgear from my winter bike (RX-100 7spd downtube). Would this provide theperformance advantages you’re talking about in terms of shifting ease?Would it be at all compatible? What other components would need to be changedto make this system work?
ThomasDear Thomas;
It should work, given that Shimano has not changed the cable pull pershift for the rear derailleur. However, the fact that the rear derailleurcage on a 7-speed is so much wider makes the likelihood of snagging iton 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 thecage. The front derailleur cage is also a bit wider, but that will be lesslikely to cause you problems. You can try it, though, and upgrade one partat a time to get the performance you are looking for.
LennardBig, small or medium, how fast to pedal?
Dear Lennard;
As I read your 50/34 debate I keeping wondering with respect to thediffering chainring sizes, what is the effect on leg speed (and power)in maintaining a given speed? Is it correct to assume that no matter whatgearing you use the power to hold a given speed is the same and the onlything that varies is the amount leg speed (RPM) required to attain it?What does this mean to the cyclist to ride faster/farther?
JimDear Jim;
Yes, maintaining the same speed with a lower gear does mean a higherleg speed. And as long as the speed is the same for the same rider andbike under the same conditions, then the power is the same. (To be completelyaccurate, there will be slight power differences due to differences inbearing and chain friction at different RPMs as well as variation withRPM in internal resistance in the rider’s muscles and joints. These effectsare 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 samepower.This is the concept behind Armstrong’s use of high cadences; lower peakloads should result in less muscle fatigue. On the other hand, physiologystudies virtually always show that the cardiovascular demands are higherat higher RPM (i.e., the heart rate goes up). Furthermore, a rider withbig, heavy legs may actually have to produce more power to maintain thesame speed at high RPM in order to keep them spinning around so fast. Sothere is a tradeoff, and this explains why all of the other top cyclistshave not adopted Armstrong’s cadence.
LennardOff-road float
Dear Lennard;
My question has to do with my quest to find the perfect free floatmountain bike pedal. On my road bike I ride Speedplays and my knees loveevery minute of the non-centering free float. My mountain bike is a differentstory. 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 pairof mountain bike pedals and I was wondering how I can find out which oneshave truly free float. The manufacturer literature always says how muchfloat their pedals have (I don’t need very much really), but nowhere doI see it stated whether the float is centering or free. The only ones Iknow of that claim to have free float are the Speedplay Frogs, but I haveheard nothing but bad things about their set, durability, etc.
IzaakDear Izaak;
In my own experience, Shimano’s float on the M959 pedal is not centeringalthough it has a smaller float range than the Frogs. Time ATACs and CrankBrothers Eggbeaters and Candys do center the foot. Over time, as the cleatswear, however, this becomes less pronounced.
LennardShutting 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 hittingthem with silicone spray, which lasts for a few rides wet or dry, but whateverwas on them when they were new lasted for months until they got wet.
SteveDear 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 isimpregnated into the metal as opposed to being a basic coating. This ensuresthe 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 addressedor the cleat has worn and needs replacement. Cleat replacement is signaledby a loose interface with a clicking noise (typically in the negative strokeof 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 exposedtension mechanism that needs to be lubricated regularly by applying a dropof lube to each spring (four per pedal). Also, the 959 has a completelyserviceable axle assembly that is easily removed by using a 17mm open endedwrench. This will allow application of fresh grease and adjustment to thecone and ball assembly. Lastly, check the interface of the rubber soleof the shoe and the face of the pedal. Much like a shoe on the floor ofa basketball court, the sole of the shoe can rub on a smooth spot on thepedal and create noise. Using a cotton swab, conservatively dab greaseto 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.