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Technical Q&A with Lennard Zinn – Murky water, nasty roads

Dear Lennard,I have an ’04 Specialized S-Works E5 frame. I’ve noticed after a ridein the rain when I tip the bike up some pretty murky water runs out thechain stays near the rear wheel. Last night I was changing my bottom bracket(the new Dura-Ace 10-speed, if that matters) and it made a nice little pondon my garage floor. Since water and probably some nasty road salt, gritand grime are getting into my frame, do I need to strip it down on occasionand flush it out with some clean water?MattDear Matt,Yes, that is a very good idea. Also, a drain hole in the bottom bracketshell is a good idea – or

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By Lennard Zinn

Dear Lennard,
I have an ’04 Specialized S-Works E5 frame. I’ve noticed after a ridein the rain when I tip the bike up some pretty murky water runs out thechain stays near the rear wheel. Last night I was changing my bottom bracket(the new Dura-Ace 10-speed, if that matters) and it made a nice little pondon my garage floor. Since water and probably some nasty road salt, gritand grime are getting into my frame, do I need to strip it down on occasionand flush it out with some clean water?
MattDear Matt,
Yes, that is a very good idea. Also, a drain hole in the bottom bracketshell is a good idea – or use a screw with a hole in it to hold on yourcable guide under the shell. And with steel frames, I think it is criticalto remove the seatpost and turn it upside down after a long ride in therain (or on the rooftop driving through rain). After it’s dry, squirt someWeigle’sFrame Saver  or at least WD-40 in there, grease the seatpost,and re-install it.I have seen so many frames rotten from the inside out, and it is sucha shame, because it is so easily avoidable. I have seen beautiful steelframes only a few years old with the only flaw being a few spots of bubblingpaint, only to discover the paint is bubbling because of rust coming throughthe seat tube. Direct the sandblaster at the seat tube, and it turns intoSwiss cheese. Or cracked chainstays sometimes turn out to have crackedbecause they are paper thin from being rusted away on the inside yet lookedfine on the outside until they cracked.
LennardCompact advantages?
Dear Lennard,
I checked past Q&A but did not see this question. What is the benefitof compact cranks? Is there a real advantage, or is this just a marketingtool to get more sales?
FrankDear Frank,
We actually did discuss this a couple of years ago after Tyler Hamiltongot fourth in the Tour with a broken collarbone while riding an FSA compact34-50 crankset. Sure, it makes sense, especially for the rider who wantsmore gearing but does not want to suffer the indignity of riding with atriple. Or for someone who wants lower gears but does not want to get newderailleurs as is required to switch to a triple. If a 50 X 12 top gearis enough for you, then a 34 X 27 can get you up a pretty darn steep hill,and the Q-Factor (space between the feet) and weight or the same or lessthan a double.Shifting in the front is not ideal, but Campy’s new compact front derailleurshould improve that. Otherwise, I think you have to use a Deda Dog Fangor Third Eye Chain Watcher to keep the chain from dropping off to the inside.
LennardPSI too high?
Dear Lennard,
I’ve been reading some of Zipp’s comments on tire pressure and rollingresistance attached below. When you really sit down and talk to them abouttire pressure they’re recommending pressures of 100-120psi (sometimes less)depending on the tire, casing, and environment. I am including commentsfrom Josh at Zipp on this topic. One thing I quickly noticed was theabsence of weight in his recommendations. A larger rider running 120 psicompared to a lighter individual (say 30 pounds difference) would exhibita larger contact patch (resistance or traction however you look at it)due to weight so I’m really not jiving on his basic psi recommendations.Leaving road conditions out (rain, etc.) what are your thoughts on tirepressure? The common theme of tubulars is the advantage of both weightand tire pressure. The ability to run pressures of 180-200 psi. I knowfor myself I feel faster (have never tried to test this with rollouts oranything) when running pressures of 140-160 psi (clincher) and 180-200psi (tubular). I’ve ridden a number of tires and prefer the ride of higherpsi tires such as Vittorias, Vredestein and Tufos.Do you know of any numbers or tests that prove these thoughts on tirepressure? I’ve had a number of lengthy conversations with Biomechanistsinterms of rolling resistance (friction) and don’t know how a general recommendationon lower pressures can be faster especially not taking weight into account.It goes against everything I’ve read about rolling friction. It’s prettyeasy to point out that the average pro in the peloton only weighs about150 lbs., so of course it’s common sense that they wouldn’t need to runsimilar pressures as you or I, but 100-120 psi seems a bit low when you’retalking tire pressure for the most efficient rolling resistances.I’ve also been reading your blurbs about tubulars, Tufo and their clinchertubulars. Taking Zipp’s tire pressure recommendations in mind where doyou stand in regards to Tufo and their clincher tubies and other high pressuretires?
TomDear Tom,
I agree with Josh, and yes, there are lots of test numbers to backit up. It is the same reason a suspension bike (or car) is faster overrough ground – less mass must be accelerated when bumps are encountered,thus saving energy and reducing momentum loss. Every little bump that getsabsorbed into your tire (another reason that supple, handmade casings rollfaster than stiffer, low-thread-count casings) is a bump that does notlift the entire weight of you and the bike.You feel fast on a rock-hard tire for a similar reason that people likethe feel of stiff brakes (V-brakes with the levers set on low leverage).The brake feels good and stiff because you are doing more of the work.If you increase the leverage, the brake feels spongy, because the extramechanical advantage allows a modest pull to squish the pads.When you ride a tire at 170psi, the bike feels really lively and fast.That is because you are being bounced all over the place by the surfaceroughness of the road. However, every time you are bounced, energy youapplied to the pedals to get you up to speed is lost. Also, you have lesscontrol of the bike, so it feels like it is going faster, even though itisn’t. Ever notice how driving down the highway at 75mph in an old Jeepfeels crazy fast, and you can cruise smoothly along at 100mph in a niceSaab or BMW and feel like you are going maybe 60mph unless you are lookingat stationary objects passing by?There is simply no question about it; rolling resistance tests conductedwith bicycle tires rolling over surfaces akin to normal road surfaces alwaysindicate the lowest rolling resistance at pressures a lot closer to 100psithan to 170psi! Years ago, for example, I saw results like this at theContinental tire factory. I was told of similar results at a number ofother tire factories I have visited.
Lennard


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.