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Tech letters for December 7, 2002
Edited by John Stevenson
Confounded by carbon fiber? Need to sound off about superlight stuff? Tech letters is the forum for your gear-related questions and opinions.
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Compact Frames
Touring options
Aerodynamics
American Classic Wheels
Computers
Crank length
DIY bike building
Front derailleur problem
K-2 Cross Bike
Mavic Bladed Spokes
Pearl Izumi Channel
PowerTap
Scicon Aerocomfort
Shimano BB compatibility
Tyre pressure
Compact Frames
From: Henry Pena
I need information on sizing a compact frame. Can you help?
Touring options
From: Bob Tomsic
After a successful supported bicycle crossing of Canada this past summer, which I completed on my racing bike, I am planning an unsupported bicycle crossing of Australia next year from Perth to Sydney. I would like some advice on what type of bike setup I should use. One option for me is to use my 6 year old Specialized Stumpjumper. I can't attach any racks to it so I would have to use a trailer like a B.O.B.. I would swap the knobbies for slicks, and probably replace the shocks with a rigid fork.
My other option is to buy a touring bike and get front and rear panniers. This is obviously a more expensive option, and if I can I would like to avoid it. What is the better setup and what are the advantages and disadvantages of each? How reliable are trailers for the long haul?
Many touring bikes on the market right now are made of aluminium. However, Trek continues to make a steel frame for their 520 bike. What is a better frame material for touring? If it is steel, why do so many companies use aluminium?
Aerodynamics #1
From: Stuart Press
Unlike NASCAR, cyclists do not ride close enough or at high enough speeds to get the effective improvement in combined aerodynamics. "Sitting" on a rider from another team is both psychological and tactical. If the pulling rider works hard to get away from the main group, the rider sitting on will most likely be able to either break away later on or out sprint the pulling rider for the stage or race. The "sitter-on" doesn't physically cause the pulling rider to go any slower. However, if the "sitter-on" were to take even very occasional, short pulls, it affords the other rider some recovery, and the two can go significantly faster. In a stage race, a good tactic is to have a lesser rider from your team, but who is still higher on GC than other breakaway riders, "sit-on." That way, the other rider would know they still had no chance of taking the lead unless they could drop the "sitter-on." Hope that explains it. -Stuart Press Los Angeles, CA
Aerodynamics #2
From: Johan Kejler
I read somewhere that if you have someone on your wheel, you too enjoy a little bit of decrease in air resistance. But that's not really the point here, this is a question of racing tactics when you want the bunch to stay together. The reason you get in a break and don't "do your share" is that you want to decrease the other rider's/riders' incentive to work. If he alone makes the break stay away all the way to the finish, he wont have much of a chance in the sprint. His best counter move would be to ease back a little to be able to make another move to drop you. Not easy, but who says it should be?
Aerodynamics #3
From: Jack
I hope I am interpreting Brian's questions correctly. When a rider is sent from a rival team to "sit" on the wheel of a breakaway rider, it really is not an issue of aerodynamics. I think that one rider behind another rider does not reduce the front rider's drag coefficient significantly, to the degree that it would be measurable.
It's simply team tactics - numerical and psychological. A solo breakaway rider has a 100% chance in the sprint, while two riders in a breakaway each have 50% chance in the sprint. So, a rival team can send a rider to chase a solo breakaway just based on reducing the other team's chances of winning.
Moreover, the breakaway rider would not be so foolish to do all of the work in front and allow the drafting opponent to win. The drafting rider gains such a huge advantage (conserving anywhere from 30% to 50% of energy) that he is almost assured to arrive at the finish line much fresher. Sure, truly dominant riders (like Laurent Jalabert in his heyday) would be able to attack, have a guy on his wheel the whole way, and still win the sprint.
But, for the most part, when rival teams send riders to chase down breakaways, they are doing so in order to optimize their own chances for victory. It is a way of "neutralizing" the breakaway through team tactics.
Aerodynamics #4
From: Dave Palese
"Sitting on" a break has nothing to do, to the best of knowledge, anything to do with physically impairing the lead rider's progress.
This tactic is often called "covering the breaks". You want your team to be present in the break but not actually contribute to it's progress. Often this is done because this particular break going away at this time does not support a team strategy for race. The covering rider is there just to keep any eye on things.
Aerodynamics #5
From: Michael Snyder
Perhaps the effect of "sitting" on a rider's wheel who is attempting a breakaway has less to do with aerodynamic effects and more to do with winning tactics. The rider attempting a breakaway is usually attempting such a move in hopes of victory (though his move could have other motives relating to team tactics). Now imagine the effect of a fellow competitor "sitting" on this rider's wheel. The breaking rider now has one of three options: 1) to drop this "sitting" rider, assuming he has the power to do so. A hill would be helpful in this situation as it would reduce the speed of the riders thereby lessening the aerodynamic benefit for the "sitting" rider. 2) to effectively tow the "sitting" rider to the finish line where he would most likely find himself sapped of strength from pulling throughout the break leaving his opponent, who has not worked during the break, free to cruise past for a heart-rending victory. or, 3) give up his effort to breakaway knowing the likely outcome should he continue (see #2). Number 3 is the effect the "sitting" rider is likely aiming for and the likely choice for the breaking rider. In the end it is the aerodynamic effect offered by the breaking rider that can doom his efforts should another rider make the tactical decision to "sit" on his wheel.
Aerodynamics #6
From: Ryan Narzisi
I think this tactic has less to do with strategy and more to do with psychology. If someone makes a break and another goes along for the ride without providing assistance, then the break will not succeed, except in the most rare of circumstances.
A lone rider, if he goes in the beginning of the race, can get a big time gap, 20+ minutes sometimes, on the peloton. However, going it alone is more physically and mentally exhausting than riding in the peloton and he is usually reeled in by the end of the race. (Look at escape specialist, Jacky Durand, who claims that nine out of 10 of his breaks ultimately prove unsuccessful.) Now when you add another rider, who is not aiding in the escape, there is no incentive for the initiating rider to continue with the break. Why? He knows that the tag along will attack at 2 or 3 kilometers to go, and still being relatively fresh, will likely blow him away. Why would a rider work in a break all day when he knows that he will end up in second?
Of course this tactic is geared towards one day races, in a stage race a team needs to be more proactive in chasing down the breaks, as finishing second in a stage race but getting five minutes on the leader or the overall leader jersey is pretty good. Look at Dekker's escape in the 2001 Tour, which very easily could have changed the character of the race entirely if Kivilev had been a better climber that year.
Aerodynamics #7
From: Russ Williams
Regarding Brian D. Stephenson's question on Aerodynamics. Brian, you have it right at the end of your question. It is a psychological tactic to let the lead rider in the break know that he has not gotten fully away from the rest of the peloton. Also to have a rider sit on your wheel for several miles only to be fresher at the finish is not something I want to think about while I am in a break. But by putting a rider in to mark the break, that is what that guy's team is forcing me to do for the entire break. Cycling is both a physical and mental race and if I am forced in a race to think about that guy from the other team in the back who is just sucking my wheel, then I already lost the mental aspect of the race. It does not hurt me aerodynamically to have him there, but it does help him to stay behind me, leaving him fresher at the finish.
Also in today's modern world of cycling with the race radio systems you see at the professional level, it is a huge advantage to have that rider in the break. They can report everything back to the D.S. about what is going on up the road to the team. They can report everything from road conditions to the health of the others in the break. If a team has a rider sitting on a break who notices that the guy driving the break is beginning to tire, they tell the team and the team can attack the break and bring it back to the group.
So the answer to your question is that it is more psychological than anything else, but has the added advantage of keeping communication amongst team members in a race, but has little to do with aerodynamics.
American Classic Wheels
From: Charles Manantan
American Classics (and others) don't usually have many problems going out of true on their own (They are on a lot of bikes for a team that I see frequently. Unless, due to Am Classic offering several super light options, you have gone astray from their guidelines and chosen a pair not suited for your weight, you shouldn't have any difficulties with the wheels, as they are pre stressed and built using very common parts from DT etc...
If it is a recurring problem, just give them a call ( get the number off the web site and ask for Michael). Am Classic does an unreal job with customer service, and will either suggest a solution, or get you the right equipment.
Computers #1
From: Glen Journeay
I installed a Shimano computer on our tandem once we realized it was dangerous (if not impossible) for the captain to keep trying to look back and figure out what gear we're riding. The stoker, our ten year old daughter, wasn't all that interested in looking either. We had assumed that the virtual cadence would be a not so useful doodad when coasting, but learned it's a wonderful way to SELECT the correct gear once you get that tandem bombing down a big hill and you're coasting. (Ten year old stokers seem to like coasting whenever possible.) Just spin the pedals over slowly, and shift until you get the right pedal cadence. This tends to avoid sudden changes in pedal cadence that pops your stoker off her pedals.
Computers #2
From: Bob Sakamato
I agree 100% with the comments of #3 regarding "virtual" cadence. "Virtual" cadence is much like my "imaginary" cadence which is usually much higher than ACTUAL cadence. At the price of the Campy Ergo and Shimano Flight - I don't want to kid myself with faulty data while training.
The Cateye Astrale is accurate, easy to use and reasonably priced (if you can find it on sale it's downright cheap!). Yeah the wires and magnets take away from the clean look of my bike, but actual cadence keeps my training rooted to reality. You have turn the cranks to make it go!
Computers #3
From: Kriss Yunker
On Campy computers the cadence is measured, not calculated.
Crank length #1
From: Bruce Lee
I have been following the crank length debate and wanted to over my point of view.
In my background, having raced road and MTB, I have used a wide variety of lengths and have seen others do the same. In fact, Interloc Racing once came out with a frame called the Stroker, equipped with 225mm Bullseye cranks (This set-up had a higher BB to allow the cranks to have ground clearance).
Climbing with this bike felt like you were on a stair climbing machine! But, it was a handful to try to spin. As a 5'8" rider, I started with 170's, went to 172.5's, raced 180's offroad. Over the last few years, I have settled on 175mm cranks for all of my bikes at this point, road, tandem, MTB, Singlespeed.
My reasoning goes back to college studies that included Motor Learning. An analogy used by the Professor was that of a person swinging a bat with weights before stepping up to the plate. When the weights come off, you "feel" you swing the bat faster, but this only lasts for a swing or two. The point is this: Yes, you do gain when you switch to longer or shorter cranks, depending on your goal. But, the gain only lasts to the point at which your body adapts. This can be a relatively short time period. I suggest that one should consider going with a crank length that fits your style of riding and stick with it.
Crank length #2
From: Mark Kerlin
You can argue all day long that the longer cranks don't slow acceleration, but physics doesn't bear this out. Shorter cranks will always yield quicker acceleration and greater control during pack riding. Obviously, a longer lever can yield more power. The efficiency question is like a bike fit I think, if you're properly sized to your cranks, you'll be more efficient. I just switched from 170s to 172.5s and I definitely have more torque and sustained power. I'm inclined to eventually use 175s or more, at 6 ft tall, though, I still prefer shortish cranks, and this is a matter of personal preference to some extent. I'll leave you with a question. Explain why track sprinters almost all use 165s? Clearance is an issue, but a shorter lever takes less energy to turn when accelerating. I agree with you though, that for a novice rider, longer cranks are not a bad choice to improve strength.
Crank length #3
From: Martin Mullin
I inadvertently ended up with a set of 172.5 cranks for my new 57cm Litespeed after riding 175s on my old bike. I'm 182 cm and have no idea what my inseam is, but it's probably average for my height. I hate climbing with the 172.5s. Previously I held my own fairly well when attacking on climbs as I could get out of the saddle and use the leverage to power the 175s in a moderate to small gear. Now, with the 172.5s, I find that when I get out of the saddle I'm either stuck spinning too-small a gear and getting no power, or pushing too big a gear. The balance between leverage and cadence just isn't right for me. Fortunately, it is crit season here in Canberra, and that is where the shorter cranks are better. Last crit season I would live in fear of the dreaded scrape of pedal on every corner. So far this season I am yet to hear a scrape. Come winter and the return of the dreaded Condor Creek climb, I'll be swapping back to 175s.
DIY bike building #1
From: Derk Drukker
I recommend you have the bottom bracket and headset installed by a professional: 1) you don't have to buy tools you never use 2) you have the most tricky part done by someone who will be responsible for any damage that could be caused by installing these parts.
DIY bike building #2
From: Charles Manantan
Applause for wanting to start building it yourself, but go to your local shop (and bring free beer) and ask the guys if they would let you come in and do it "with" them, or if they would allow you to watch them build a few. And don't just pay attention to Head set and BB! If you have, as yet, not run and capped cables, mounted and aligned brakes etc you should see it all first! Something so small as over tightening a stem bolt (easy to do these days) is critical worth paying attention to.
It's nice to "be able" say I built my own Bike! It's terrible to "have" to admit it a second time (while laying on the ground holding a part that came off!)
DIY bike building #3
From: Russ Williams
Vincent, you may want to let your local shop "chase and face" your bottom bracket shell as well as setting the headset race on your fork's steerer tube if it is not already installed. Most of building a bike from scratch is pretty easy but for those two things you need expensive tools that most consumers' home repair kit just does not have. Also I am assuming your wheels are already built, but you may want to have the shop check that they are dished properly to your frame. Sometimes wheels dished to the truing stand are out of dish in the frame, since you ride the frame and not the stand I think you can see where the problem lies.
After you get all that set up, just make sure you grease the right places like the seat tube for your post and your threads for pedals and such, as well as cutting shift and brake housing to the correct lengths and de-burring the housing to reduce the friction so all runs smooth.
If your technical skills of working on your own bike are pretty good, building it yourself is not a bad idea, but if you have not worked much on it you really ought to consider letting the pros at the shop do it. It's what they do for a living and you are putting your new ride into a pro's hands to do what they do best. The other side of that coin is that you are the one riding it and are more likely to be extra careful on your own bike.
You can always build it yourself and then pay the shop like 5 to 10 bucks to look it over for you if you are in doubt. Good luck and have fun!
DIY bike building #4
From: Pete Lester
You will want to have a qualified professional chase the threads in your bottom bracket and rear derailleur mount. This removes over spray and make sure that the threads are perfect for your install. The old schoolers will refer to this as "chasing and facing" because the bottom bracket and head tube often need to be "faced". this is a process that assures the two faces of both frame components are perfectly aligned with each other. Also If your new frame is steel, take the time to treat the inner tube walls to prevent corrosion which will lead to an early failure of your frame. I learned this the hard way in Belgium this summer when my chain stays failed due to rust that occurred inside of the tubes.
Anyhow, good luck. Make friends with the wrench who you have do the work you feel uncomfortable with and then have him/her teach you how to build your own wheels. That is a real test and you'll come away with some great knowledge and increased confidence in your abilities.
Front derailleur problem
From: Adrian Carter
After weeks of haggling, I scored a great deal on a Shimano Dura-Ace crankset and bottom bracket. The problem is, my Mongoose 5.3 aluminum bike had a 46 tooth large chainring. To add to my misery, my front derailleur is not a braze-on. It has a welded opening that allows you to lower or raise thee derailleur. My problem is, the added piece can't raise the derailleur any higher, and I can't afford to buy another bike. I CAN ride the bike by removing the front derailleur and tying up the cable. But for hill-riding purposes, I NEED the smaller chainring (53-39).
What can I do?
K-2 Cross Bike
From: Jim Cushing-Murray
I say use an XTR front derailleur. I'm riding a Morati with a TA triple crank. Since I use it both for touring and cross (I have also done road races too), I have a 51,42,32. This set up works great. I never use the 51 in cross but it makes a great chain guard and the 32 comes in handy.
Mavic Bladed Spokes
From: Charles Manantan
This usually happens when truing the wheels, as some manufacturers use a bit of lock tight on the spoke when building and it holds the spoke in place as you true the wheel. I have seen a few shops use several different "special" tools to hold the spoke in line while truing them.
Just be sure the spoke is free to turn inside the nipple before truing and make sure what ever is holding the spoke in place doesn't damage it.
Pearl Izumi Channel
From: Michael Gallagher
I don't have the Pearl Izumi jacket but after many years of cycling, hiking and backpacking I have given up trying to find the perfect waterproof/breathable jacket. Waterproof they may be, but breathable is another question. I find that with anything beyond mild exercise the perspiration produced is too much for any jacket to handle and I end up as wet as I would if I weren't wearing it. Now I tend to wear a shell layer that's billed as water-resistant, that breathes well and will keep rain out long enough to get home from a ride or finish a hike without me ending up totally soaked.
Good products I've tried are the windstopper jerseys - Assos Prosline is one - expensive but awesome, or the Windbloc or Windstopper fleeces you can buy in outdoor stores. Better to be comfortable and damp, than uncomfortable and damp (it works for me in Seattle).
PowerTap #1
From: Sean Jones
I used a PowerTap hub in 1999-2000 and it was a great purchase, but when I used the hub outside water would get inside the hub. I eventually sold the hub because I live in a humid and moist climate and the hub would act up when I rode outside. I would love to purchase another PowerTap because of the ease of use and it's accuracy. I was wondering if Graber has done anything to address the issues of leakage in the hub.
PowerTap #2
From: Bill Mirbach
I had one of the first PowerTaps, so my point of view isn't entirely up to date. I liked reading power, but found the problems with the device were too frustrating. I bought an SRM and I wouldn't go back. Problems with PowerTap:
Interference - still a problem with today's units, I'm told. I would lose a lot of data; it would cut out for minutes at a time without explanation.
Leakage - water would get into hub. Short, inconsistent battery life.
Limited number of intervals. Nine's not enough.
Clunky interface - at least compared with SRM.
I never bothered with the software.
PowerTap #3
From: Scott Grimshaw
I used the PowerTap for a period of 6 months, back in 2000. I thought it was a well built instrument, but I became annoyed when, as your reviewer noted, it would cut out periodically. I too mounted the receiver as close to the hub as possible, put conductive paste on the units' electrical contacts assuming that it was breaking contact with the bar mount, and had new batteries. I didn't carry a cell phone then. None of these solutions worked. It still cut out randomly.
I switched to an SRM power meter in September 2001 and have experienced ZERO problems. Sure the heart rate jumps around a little when you go under power lines, but that seems to be the case with all wireless heart monitors. I can now concentrate on riding.
The price of the SRM is still a barrier to entry for most people. Perhaps competition in the future will get this unit below $US1000. In any case, the SRM is the unit to get if you want reliability and durability.
PowerTap #4
From: Uby Woods
Another problem with interference with the PowerTap is never have a polar cadence sensor on your bike at the same time as the PowerTap as you will get about 1 second of reading in every 10 seconds. My PowerTap got a trip back to the states just so they could tell me that there was nothing wrong with it. It wasn't until I got it back that I started to play around with taking off different sensors until it worked, and work perfectly it does now.
PowerTap #5
From: Carl Paton
Hi guys, just thought I would give you some feedback on the PowerTap hub in terms of comparison with the SRM system. I work as a senior physiologist at the Waikato Institute of Technology in New Zealand, provide physiological support for N.Z. national squad riders and am currently completing my Ph.D. on physiological monitoring of cyclists.
I have used the PowerTap in conjunction with both the SRM crank system and the Kingcycle system to monitor cyclists over the last couple of years. I have found the PowerTap to give very similar average power measures to a properly calibrated SRM system in both 60 second and five minute efforts. The PowerTap does seem to have a few problems in dealing with fast accelerations (maybe due to its relatively low sampling rates) but that would not bother most people. All PowerTaps I have tested seem to suffer from data loss at some point, with no real explanation as to why, they do seem to eat through batteries rather quickly though, so change them regularly.
I have also heard of problems with water proofness, so don't tend to take mine out in the rain. Overall though a good product which offers huge advantages over heart rate monitors, I certainly encourage the riders I coach to get into power monitoring ASAP and the PT is the cheapest, most reliable of the devices I have tested (no I don't have any affiliations with the company if that's what anyone is thinking). You cannot beat an SRM if you can afford one but this is the next best thing. Just one last thing, I think you will find that the PT has now dropped in price ($699 US) and comes bundled with the software at that price so its an even better buy.
PowerTap #6
From: Robert Chung
Jeff wrote: "Having not had a chance to do a comparative test with other power devices, I can't personally comment on the PowerTap's accuracy compared to those
There's a head-to-head-to-head comparison of power meter consistency (though not accuracy) at http://mywebpage.netscape.com/rechung/wattage
And I think the 460w average for Alpe d'Huez is exaggerated. I think it should be more in the 415ish range.
Scicon Aerocomfort #1
From: Larry Theobald
When evaluating a bicycle travel bag, one must consider what is most important.
Protection? Ease of use? Light weight?
Another thing to consider is where the case will be used. In the US of A I've witnessed bike cases/bags/boxes falling out of the cargo hold of the airplane onto the tarmac, while in Europe I've seen pro-quality bicycles checked as baggage without ANY packing---and seen them retrieved at baggage claim without a scratch.
We've been using BikePro USA's "RaceCase" for over 10 years, both for our own machines and those of our tour clients who have the option of purchasing one through us.
They offer excellent protection but DO require removal of pedals, handlebar/stem and seat/post in addition to removing the wheels.
I took a good look at the Sci-con at the recent Interbike show since it's made in Italy and promised the ease of just taking the wheels of and mounting the bike in the bag.
After examining the bag (and the bike packed inside) I thought padded wheel bags should be included. The example at Interbike had a Mapei Colnago packed inside and one could see scratches on the bike where the wheels had made contact with the frame.
Padding around the perimeter was thin at best. I thought they should have sewn the same type of padding used on the sides into the perimeter since impacts there can do just as much damage, especially in the handlebar and rear mech areas.
For a pro or amateur racer who values the quick and easy packing/unpacking of his machine more than protection; or the team mechanic ( I would much prefer packing 10 bikes in Sci-con bags compared to the time it would take with BikePro!) this could be a good travel bag.
IF they improved the perimeter protection and included padded wheel bags... the ease of packing/unpacking might get me to consider switching!
Scicon Aerocomfort #2
From: Lola Bayley
I have to say that these bags are the BEST thing that we have come across. We have had 2 blue bags for approx 2 years. My daughter is about 5'4" tall and when she travels with 2 bikes, one in each bag, she is the only one who doesn't have any problems moving through an airport. She just loops the two bags together in Road Train style grabs her travel bag , which is also on wheels, and off she goes. When it is time to be picked up from the airport we throw one into the boot of the car and the other one into the back seat. She is also small enough to fit into the back seat with it. But when we pick up our son from the Airport with a Qantas Box with 2 bikes in it we have to borrow a Panel Van for it to fit into. If he didn't have to use Qantas boxes life would be so much simpler. But not our choice or his.
Shimano BB compatibility
From: Stephen Hill
I use the Dura-Ace BB with my Ultegra crankset. I had precisely one adjustment problem - the fixed cup was rotating out. This was (and may still be) a common problem that I remember well from 15 years ago, that I cured on this BB the same way: LockTite. The BB has now been in my frame for 1250 miles with no issues. If someone needs to have a BB adjusted more than once, I would suggest that the second adjustment needs to be to a new mechanic. As for do-it-yourself, the Branford Bike website has a tutorial for those who have never touched one. It took me 15 minutes to remove / clean / re-grease / install my BB - not a high cost for the benefits of well-maintained BB.
As to the Ultegra vs Dura-Ace issue, as a mechanical engineer, I like the Dura-Ace design better. Had the problem that I had on my Dura-Ace happened on an Ultegra BB, I would have been purchasing a new BB. As it was, the Dura-Ace, due to its use of needle bearings, suffered no damage whatsoever, despite riding 30 miles on a BB that was coming apart.
Tyre pressure #1
From: Matthew Charles Riggs
I think a lot of it has to do with which kind of tires you are running, tubbies or clincher. With clinchers jumping up in quality in the recent years you can take them up to 130psi with no problems. In American style crits, I run tubular Vittoria TT's at about 130-145 psi and have had no problems. Remember, the higher tire pressure the less resistant.
Tyre pressure #2
From: Charles Manantan
Run the tire pressure that is on the tire. (They can vary by a large amount)
Running it within the range that the manufacturer specifies is wise as they have tested the tire to go beyond the limits listed, but only by a bit. As you are not too heavy and indicated you are on an even surface, you can run it to the max pressure indicated, which will reduce rolling resistance. If you feel your traction isn't good, lower the pressure till it is.
And tell us all where you ride that is "Puncture Free"!
Tyre pressure #3
From: William Lim
110 to 120 is a good range to start with, but be sure to stay in the manufacturers recommended range. Tyre pressure depends on many factors; wheels, bike and rider. At 65 kilos, you are on the light side, you might want to keep on the lower range. The more psi means the less tyre contact and quick handling. Plus, if you have aero rims, higher pressure will make the ride very stiff and rough riding.
