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Technical Q&A with Lennard Zinn - Same ratio, different result?

Published: Apr. 6, 2004
Technical Q&A with Lennard Zinn - Same ratio, different result?
Technical Q&A with Lennard Zinn - Same ratio, different result?

Dear Lennard,
For the sake of example, let’s say you are in 39/17 and switch to 53/23 (or whatever the equivalent ratio is). Assuming the gear size is the same, is the 53/23 more efficient because the chain is on a larger tooth cog?When compared, does the rider have more leverage on generating rotation of the rear wheel when using the larger ring? Also, does the 53T chainring reduce leverage that the crank arm exerts on the chain and thus the back wheel?
Trey

From Wayne Stetina at Shimano
An interesting question to be sure. Basically at the heart of the debateabout any potential advantages for Pitch 10 track components as well.
My understanding, after speaking with numerous engineers and trackracers over the years:The simple answer to Trey's questions is no, but there are still minordifferences...1. The power transfer to the rear wheel should be identical, subject to below points.
2. The Chain force (pressure) on the individual teeth is higher for 39x14 vs. 53x19, or whatever. So Chain & Sprocket wear is increased. (Probably does not apply to Pitch 10?)
3. The larger diameter theoretically turns more efficiently – better for Pursuiters, Points race, Hour record. Might even be measurable for 11/12, compared to 14/15?
4. The smaller diameter accelerates faster due to less mass – better for Sprinters.Okajima just advised me that 14-tooth and smaller rear cogs decrease chain efficiency significantly for track bikes, although the difference is still minimal when compared to rear derailleur pulley drag and cross chain alignment efficiency issues for derailleur bikes.
Wayne Stetina
Shimano AmericanFrom Dave Anthony at FSA
No. It's an equivalent ratio. For a roll-out equivalent ratio, with a bigger chainring, there is less leverage on the front chainwheel from the crankarm, but more leverage on the rear wheel from rear cog. If you want more leverage on the rear wheel, you need to change to a lower gear ratio or use longer cranks for the same gear ratio.Anecdotally, I seem to recall that track sprinters prefer (for a given ratio) to use smaller chainwheels and cogs as the whole drivetrain (including the shorter chain) is lighter and easier to accelerate; acceleration being paramount to the sprint event. At the other end of the spectrum, pursuiters who ride at constant speed for a longer time prefer larger chainwheels and cogs, as there is less friction, as the chain links do not rotate so much around the larger cogs. This is why you might see a pursuiter choose a 52/14 instead of an equivalent 41/11.
Dave Anthony
Full Speed Ahead

The tool for finding the right crank length
Dear Lennard,
I work at a bike shop. I was wondering if there was a tool to givecustomers an idea what crank length was proper for them other than the0.21,0.216 methods available? I have heard of, but not seen, such a devicethat makes it possible to move the pedal to different locations withoutremoving the crankarms.
Bruce

Dear Bruce,
I can’t imagine anything that would allow you to do this without removingthe customer’s crank. You could put on an adjustable crank, though, andchange lengths without removing it.Perhaps you mean this type of crank in this photo of a Tiemeyer size cycle with various holes for the pedals, which I believe goes from 165mm to 185mm. Also, Racer Mate has a “VariCrank” which goes 165-185mm by rotating a cam at its center. There are a number of telescoping adjustable cranks on the market up to 185mm, and even to 220mm. Any of them will be expensive, but worth it if your shop does a lot of this type of experimentation.
Thanks,
Lennard

Technical Q&A with Lennard Zinn - Same ratio, different result?
Technical Q&A with Lennard Zinn - Same ratio, different result?

What are those Swiss guys up to?
Dear Lennard,
I have a few questions regarding DT Swiss:What is the difference between 240s Road Hub and Hugi 240 Road Hub? I’ve looked all over the website but cannot determine differences beyond marginal weight differences and different labels.Do you have any thoughts or feedback on either of these hubs?Do you have any thoughts on the DT Swiss rims - Road 1.1?
Michael

Dear Michael,
The new 240s replaces the Hügi 240 (which was in production from2000 to 2003). The 240s is essentially a Hügi 240 platform and mostof the parts are interchangeable between the two models. However, the 240shas an accumulation of refinements and upgrades over the last few years,plus some new attributes for 2004 as well. What’s new is; stainless steelbearings, new coated drive ratchets, contact free double seal systems,and corrosion resistant internals. The new seal system lowers rolling resistance.

Regarding the RR 1.1 road rim: All DT rims are made in-house and utilizea welding process called SBWT (strength boost welding technology). Thesidewalls are symmetrically machined, and have brake wear indicators (tinyindents) along the sidewall surface. The rim profile is designed to increasetorsion resistance. Eyelets are stainless steel, overall height is 21.2mm,width is 19.3mm, and weight is 415g. Hole drilling is available in 28,32, and 36.
Lennard

Regarding chains
Lennard:
I enjoyed reading your tech report and subsequent reader comments onchain wear and maintenance. However, I was surprised to see that most readershad already given up on extending the life of a new chain and were moreconcerned about how to use an already worn chain without wearing out other,more expensive parts like cogsets. Only one reader came up with what Iwould consider the right response: "bottom line is, clean and lube yourchain." As you noted in your report, the cost of narrow, precision chainsis continually on the rise. It seems obvious to me that if you have tochoose between the cost of a bottle of degreaser and a bottle of bike lube,and the cost of a chain, you'd go for the degreaser and lube every time.And the benefits of a bottle of good, bike-specific degreaser and lubricantaren't limited to extending the life of components. They also include aquieter ride, less friction while pedaling, and smoother shifting.

Of course, many riders are already doing this, but not doing it enoughto head off wear before it happens. Riders are always telling me how farthey have gone between reapplications of lube, and even seem quite proudof their accomplishment. Most will wait until the chain squeaks, a habitthat manifests itself in your reader comments. Unfortunately, by the timetheir chain starts talking to these riders, it's saying, "too late." Irreversiblewear has already occurred. The formula for maximizing drivetrain life isa simple one: lubricate after every wet ride, clean (and lube) after everydirty ride, and lube at least every 100 miles when riding in "optimum conditions."

So what's keeping more riders from following this formula, and increasingthe life of their chain, cogs, and chain rings, by what our research hasshown to be a factor of 5 or more? It's simple: you don't feel like cleaningand lubing a chain when you're hurrying out the door for a ride, and yousure as hell don't feel like doing it when you get back from a ride andare trying to decide if you should take a shower, eat Twinkies, or takea nap. It seems like there's never time to take a minute to maintain yourchain, no matter how much it'll save you.

Lennard, over the years bicycle lubricant companies like Finish Line,White Lightning, and others have pushed the envelope on bicycle lubricationtechnology. We are keeping up with component technology advances whilealso trying to address the real world needs of time-strapped riders. Thereare now fortified dry lubes, synthetic wet lubes, self-cleaning wax lubes,all-condition lubes, chain cleaners, chain grunge brushes and more. Cleaningfluids are also evolving, and while citrus and non-citrus biodegradablefluids dominate, Finish Line is pioneering a new cleaning category called"dry cleaning." It's based on our new cleaner, Speed Clean, that's so effectiveand evaporates so quickly that you can use it without water rinsing andwithout having to wait for it to dry before lubing your chain. It's findingfavor with owners of disc brake-equipped bikes, but it is also a greatalternative for anyone who wants to quickly clean their drivetrain andget back on their bike.

Thanks for the opportunity to respond to your readers. You have a greatforum which is highly respected by those of us in the industry.
Hank Krause
Founder / President
Finish Line Technologies, Inc.


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.

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