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Tech letters for November 21, 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.
Send your emails to Cyclingnews' tech desk
DIY bike building
Aerodynamics
Tyre pressure
Rim sidewall thickness
Mavic bladed spokes
MTB pedals for Paris-Roubaix?
American Classic wheels
Shimano XTR
Chain scrapes on a Quantum
Computers
Crank length
Creaking Mavic Ksyriums
Bike choices
Pearl Izumi Channel
Shimano BB compatibility
Sloping frames
Washing waterproof garments
DIY bike building
From: Vincent Geluwie
I just bought a new frame and all components I want to fit on it. I want to try to build it up myself. Placing seatpost, brakes, bars etc is easy, but what about placing the bottom bracket and fitting the cranks to it. My frame also has an integrated headset, can I fit the top part of the headset myself? Do I need to go to a bike shop for this or can I do it myself with the proper equipment (and what equipment do I need)?
Vincent, I suggest you browse Park Tool 's website for information on tools and techniques. Yes, you will need special tools for fitting the bottom bracket and headset to the frame, though sliding the top of the headset down the steerer is trivial.
Aerodynamics
From: Brian D. Stephenson
I occasionally read in race accounts that a rider from a rival team is sent to "sit" on someone who is making a break. The implication is that by hanging on said rider's wheel, he will cause him to be slower and reduce the gap he might otherwise have been able to establish. I can appreciate that two or more riders pulling through are going to be faster over a distance than a solo rider, but it does not seem right that just towing a rider creates additional drag compared to going solo.
In NASCAR racing (much different Rayleigh Number, admittedly), having a car on your rear bumper lessens the drag for the lead car by reducing some of its airflow separation and turbulence, thus both go faster. Has it been demonstrated scientifically that a trailing rider actually creates more drag for a lead rider? Or is it really a psychological tactic to demoralize the guy making the break?
Tyre pressure
From: Peter Bolton
What sort of pressure should you run in good criterium tyres on smooth, flat puncture free surfaces. Weight of rider 65kg.
110-120 psi seems to be a common range.
Rim sidewall thickness
From: Simon Phillips
Like most cyclists my good components eventually end up on a winter bike etc, I have got a home made tool (made from a spoke) for checking the thickness of clincher rims (the braking surface to the inside of the rim) but would like some advise on what is considered a reasonable minimum of material.
I've always liked a simple technique suggested originally by Chris Juden of the UK's Cyclists' Touring Club, and that is to perform a 'proof test' by inflating your tyres to twice their usual pressure. This increases the side load on the rim and will crack them if they are getting dangerously thin.
Mavic bladed spokes
From: Tim McDonald
I have Mavic Cosmic Elite wheels and have noticed that the spokes like to twist around, thus eliminating any aero advantages that they may afford. What is the best way to alleviate this problem?
MTB pedals for Paris-Roubaix?
From: Chad Stone
I've been curious as to why riders such as Stefan Wesseman don't switch over to a MTB shoe/pedal combos for Paris-Roubaix. I know broken cleats have been an ongoing issue with him and I would imagine for other riders as well. Fred Rodriguez suffered from the same problem this year as well. Is there some sort of a UCI rule mandating which type of pedals one can use in road racing or is it rider preference?
There's certainly no UCI rule about pedals that I am aware of. I think the issue is that riders tend to be very particular about shoe and pedal setup and aren't willing to change systems for just one race.
American Classic wheels
From: Jim Kuhn
American Classic wheels - has anyone had problems with keeping them from going out of true? Is there a trick I am missing?
Shimano XTR
From: Glenn Ray
I was wondering if I could use the new XTR shift/brake levers with the old 2002 rear/front derailleur, and if I bought the new XTR wheelset with its new rotor would it work with my 2002 XT brake set?
According to our Shimano font of all knowledge G-Matt, the 2003 shifters will work fine with 2002 derailleurs (though obviously the shift action will work differently from Rapid Rise) and the heels will slot straight into your XT disk brake calipers.
Chain scrapes on a Quantum
From: Gerrit Hermans
Wolfgang, I had a similar problem with my 2000 Quantum Race. In my case it wasn't the chain but the cog-set scratching slightly the paint of the frame after changing from 9-speed to 10-speed. Klein explained my frame wasn't 10 speed compatible and sent me a new one in exchange. So - I would call them.
Computers #1
From: Andrew Pagett
I have a Campagnolo Ergobrain. I have found it invaluable in my training work. The integration into the ErgoPowers is excellent. No need to "shift" position from the hoods to look at different data, simply push the little button on the ErgoPower.
Being extremely sad knowing just about everything you need to whilst in motion is excellent, Cadence, Speed, Trip Information, Gear Development ... more than any saddo could desire!
For training the "cadence" warning and the interval settings on the Ergo 10 are invaluable.
One thing, for some reason it claims you have to have Pro-Fit pedals for the cadence magnet. This is rubbish works fine in my Looks, nice and tidy, no nasty cable tie on the crank to hold the cadence magnet.
Computers #2
From: Dave Abernathy
I have the Campy 10 speed computer and love it; never had one bit of trouble. It sits on a mount centred just ahead of your stem and I like that position vice having a computer on the bar to the left or right of the stem... anal-retentive I suppose. The self-learning feature is great - it learns what cogset you have rather than you having to program it. The display is nice and readable with almost any bit of information you could want; cadence, etc and an interval timer to boot. If you can get past the price then why not put a Campy computer on your Campy bike? I use Avocet 45TT on two other bikes and like them as well. The only problem I've had with Avocet is it seems as if the cadence function stops when it rains then returns when it dries out. I do like them, though, and they cost less than half of what the Campy does.
Computers #3
From: Brian L Fancher
The problem with the Shimano and Campy computers, with their virtual cadence, is that the cadence readout is based on speed and gearing, not on actually pushing the pedals 'round. On the other hand, you can get some awesome cadence readouts if you gear down to, say, 42/19 and coast downhill at 40+mph! If you really want cadence, stick to Cateye/Vetta/Sigma/Specialized/Etc....
Computers #4
From: Steve Rempel
The Planet Bike Protégé 8.0 and 9.0 are unlike any other cyclometers I've used, giving one speed, distance, time, max speed, and average all at once, in a relatively small, buttonless package, with numbers large enough to satisfy even these far-sighted old eyes. The 9.0 also shows temperature. I can't image going back to an "ordinary" cyclometer. This is a great example of "out-of-the-box" thinking.
Computers #5
From: Ryan McCormick
Cateye computers are very reliable and most are very easy to use. I have had limited time on an OS computer but I thought it was a very quality computer. Since you already have Campy on your bike you could also consider using the ErgoBrain in either the 9 or 10 speed version, whichever applies to your bike. I am currently using one and I am very pleased with it. The large screen is easy to read, using the cadence wire is optional, and it lights up red when you are out after dark. Though it is not easy to set up the first time, if you follow the instructions it is not hard. Good luck with your computer choice.
Computers #6
From: Luke Harvey-Palmer
Have tried many computers - Cateye, Sigma, Avocet, Vetta, Campagnolo. 18 months ago, I bought a Campag outfit, and promised myself the Ergobrain 10 to finish things off. At the time had to send order to the UK (reside in Aust) for the Ergobrain 10. This computer has been fantastic. For fear of sounding 'slack' I cannot do without the gear function, nor the ergo function (change functions via ergo levers). Like everything, there are negatives - tricky to set up, difficult to access 'every' function (there are plenty), and not cheap. But in all, absolutely the best bike computer I have used. Buy the Ergobrain!
Computers #7
From: Bob Olson
I've got an ErgoBrain 10, which I like, but there are a few annoyances for such an expensive computer: - You cannot enter accumulated mileage on the odometer, such as when you install the unit or need to change the battery, - It frequently indicated the incorrect chainring, showing "53" when I'm in the "39," - The spoke magnet is huge and heavy!
Computers #8
From: Jonnie Walker
If you want a good all-round computer, go for the Cateye Astrale It has all the regular functions, along with cadence (real cadence, unlike the campy, or Shimano ones you have to reset every time you change cassettes, as with the.). I have ridden these computers through everything imaginable. It is the only one that I have had that has withstood rain, snow, and mud. The other bonus is it is way cheaper than any of the high end ones. You could use three of them for the same price as any of the OS versions.
Crank length
From: Aki Sato
In response to Richard Rule's crank length letter:
If you are 6'2", 35.5" inseam, there is little reason for you not to buy 180's. Long cranks give you extra leverage and allows your muscles to exert power over a greater range of motion. If you're limited in training time, don't have the aerobic capacity of a pro, and just want to enjoy 1-3 hour rides, then I think longer crank arms are great.
I'm only 5'7" with a 29" (barely) inseam. I ride a 49-50 cm seat tube frame. I have decent speed/power, terrible aerobic capacity. Conventional wisdom would put me on 170's or shorter. By working for a couple months to overcome the tendency to push, I eliminated the one significant drawback of the longer cranks. With limited training, I found a dramatic increase in performance after switching to 175's. I first learned of long crank usage when Renault Elf put their riders on long cranks. Marc Madiot, riding a 55 cm frame, used 180mm cranks with success. I "re-discovered" the theory last winter when I rode a mountain bike with 175s and found myself riding as fast on it as my road bike. I made the switch soon after that.
Some precautions. Long cranks force your feet to make bigger circles and increase the distance your various leg parts travel for each revolution. Your knees go higher, drop farther, your foot extends forward more, your Achilles is stretched a little bit more. Long legs minimize a lot of those effects. Long cranks require adaptation time, which, if skipped, give rise to some "long crank arm" myths like the inability to spin and losing efficiency. Since the cranks drop further, you'll hit them (or your pedals) more often on rocks and such.
If you allow yourself time to adapt to the new cranks, you'll be able to spin fine. Switching off season helps - you can focus on regaining pedal speed instead of keeping up with your riding friends. After my November 2001 swap, my comfortable cadence dropped to just over 70 rpm's. However, my performance increased significantly due to increased leverage/power. By March 2002, my comfortable cadence was back at 100+ rpm's. To measure cadence, buy a simple cyclometer with cadence. Mine cost less than US$60 (and it has heavy duty wires for mountain bikes). You can also count rpm's for 6 seconds and multiply by 10, but this is less accurate and immediate. To see where you ride comfortably, simply ride without paying attention to your exact cadence. I find that my cadence climbs 5-10 rpms if I ignore it. You'll find that your cadence returns to a consistent range each time you do this on a given day or week.
As pointed out in other letters, "pedaling efficiency" has more to do with having a good form and discipline rather than crank length. If you can maintain form comfortably at 100-120 rpm's, whatever the crank length, you'll be able to maintain it at lower rpm's.
Losing efficiency in specific situations is a different matter. Long cranks don't help sometimes, particularly at very low cadences. On very steep climbs at low rpm's, they seem to lose efficiency (this is my personal observation). I attribute the efficiency loss to a combination of a longer "dead spot" in the pedal stroke as well as a higher output "power stroke". Long cranks also accentuate the difference between your lowest and highest output for each revolution. This causes the pedal to "stall" in the dead spots. When pedaling at a reasonable speed (70-80+ rpm's), the dead spot issue is moot. In fact, you'll find that you have significant more power on slight and moderate uphills - you'll be able to shift up a gear or two. Your flat land cruising speed will increase as well, as much as 10%. Your top speed will decrease for a given gear due to the larger pedaling arc - you'll find yourself using bigger gears when sprinting.
If you do decide to get the longer cranks, don't forget to adjust your position on the bike. Your position is determined by the amount your cranks point forward (for seat fore-aft) and down (for seat height). Check your seat height (lower for longer cranks), seat setback (this may not be necessary because lowering your seat will move it forward), stem height and length (lower and longer, usually). If you install 5 mm longer cranks, you'll need to move your seat forward about 5 mm and down about 5 mm. Remember to first maintain the seat-pedal relationship and then worry about the seat-bar relationship. Don't adjust your seat position to fix an incorrect stem or bar - this compromises your seat-pedal position. Instead, you should fix it by changing your stem or bar. In the case of 5 mm longer cranks, your stem will need to drop 5 mm and extend 5 mm.
Creaking Mavic Ksyriums
From: Todd Holland
I had a creak in my Mavic Heliums that gave me fits. Checked and re-checked spoke tension, trued and stress-relieved, lubed the nipples, lubed the heads, adjusted the hub bearings, cleaned and re-tightened the cassette. But the creak persisted. It was the hard yellow plastic Michelin rim strip! This thing had developed a crack at the valve hole, and the edges would click over each other as the tire rolled around (and eventually chafed a split in the tube).
Bike choices #1
From: Ian Loxton
Sorry Jim but I have to disagree.
I was new to cycling and bought a Bianchi all aluminium frame and fork set up around two years ago. 3 months ago upgraded to a Pinarello with carbon Meta fork, and I can certainly feel a difference, especially when it comes to jarring wrists / elbows etc. The carbon fork is much nicer to ride. I am used to feeling for differences in various machines, as I raced motorcycles for numerous years. I find I am cornering with greater speed and receiving better feedback in terms of knowing what my front tyre is doing (technical descending is my 'thing' I guess!)
But this has been a revelation and a long from way from 'the end of story'.
Bike choices #2
From: Laurence Arnold
Interesting to see the discussion about new bike choices and people advocating steel as a good material for road bikes. Having bought a steel framed Pegoretti last year I can confirm what a wonder material it is. Despite my feeble legs and lungs I have outclimbed many an alu/carbon rear end bike. The bike is fast, when required, smooth and precise. If you fitted wheels to yourself, that would be the best description of the ride feel.
If you're after a fantastic riding bike, then check out Pegoretti. The bikes are custom made, so get measured up for the perfect fit. The steel Marcelo has huge chainstays for great power transfer that makes the thing respond to every bit of effort from your legs. All that, plus it's a bike you can ride all day due to its comfort.
Remember "steel is real".
Pearl Izumi Channel #1
From: Jeff Thomas
I'm from Seattle, so a waterproof jacket matters on my commute. A year ago I bought, if not this model, its immediate predecessor. Same screaming yellow, same cool (and watertight) zipper, same cuffs, same no-pockets, no-vents approach. My only real complaint (lack of pockets is easily worked around) is the lack of vents. Given that you really heat up in this jacket, even in the winter (the material might draw sweat away, but "breathable" apparently doesn't extend to heat transfer), I would've happily paid more for vents, say, under the arms, where leakage isn't an issue. As it is, I find myself preferring my old Gore-Tex, not-specially-for-biking jacket unless it's really pouring.
Pearl Izumi Channel #2
From: Christophe Noel
I'm the General Manager for Sockeye Cycle Company in Haines, Alaska. We are the largest bicycle touring company in Alaska with a full time staff of more than 18 full time bicycle guides. Everyday, our guides reported to work wearing their uniform which was the same Pearl Izumi Channel Jacket you reviewed. For those not in the know, Haines, Alaska is nestled in the heart of the world's largest temperate rain forest. We tested the Channel Jacket daily, and in the most impressive rain storms imaginable. After a hundred days in the Channel Jacket we all agreed unanimously that the water proof qualities of the jacket were impressive but not always 100% dry. The cuffs which proved really comfortable did cause moisture to collect at the wrists after a while. As for breathability, the jacket didn't quite meet our expectations. It took a minimal rainy day with a minor amount of activity to get the inside of the jacket feeling a bit 'muggy,' and moist. All 18 of our guides used technical garments under their Channel Jackets to help boost the overall performance of the fabric. On behalf of 18 bike guides who used the Pearl Izumi Channel Jacket everyday for five months in the rain forests of Alaska, I give the Channel Jacket a 6 point score out of 10. Too much money... not enough performance.
Pearl Izumi Channel #3
From: Noel Llopis
I have some questions regarding John Stevenson's review of the Pearl Izumi Channel jacket. I wonder if you could email me back or add that information to the review if you think it would be useful to other readers.
My first question is about breathability. Just about every water-proof jacket does a good job of keeping the water out, even a garbage bag will do. The question is how well does it let sweat evaporate. I tend to sweat quite profusely, and I've never seen a water-proof jacket that keeps up with my rate of sweat, and gets totally soaked from the inside in minutes. How well does the Channel jacket hold up under strenuous exercise?
The second question is about durability. I believe that Goretex fabrics need to be treated regularly or they lose their breathing abilities. The review mentions that the breathable layer is sandwiched between two other layers, so does that mean it requires no maintenance?
The Channel's fabric seems to me to perform much like Gore-Tex in terms of its breathability, which means it's adequate for moderate efforts in dry conditions, but you do get sweaty if it's humid. If 'it works fine when it's dry' sounds silly, well, my main use for a waterproof is as a windshield in cold conditions - riding on the road in serious rain round here is tantamount to suicide, such is the astounding incompetence of the average Sydney motorist at the slightest hint of moisture.
I suspect it's not possible to make a completely waterproof fabric that's breathable enough to cope with the sweat output of a cyclist working hard, and if you need very high breathability, then a microfibre fabric like Pertex can be a better solution, even though it's not anything like as waterproof as PTFE membrane fabrics.
Nevertheless, I agree with Jeff's point about vents - they certainly wouldn't hurt.
To Noel's final point: The Channel's fabric and Gore-Tex are similar in that they have a membrane sandwiched between layers of cloth. Gore-Tex doesn't need to be treated to keep it waterproof - the membrane takes care of that - but the outer fabric layer usually has a water-repellent treatment that helps water bead and run off, and this may need to be renewed after a few washes. See Brendan Moylan's letter below for more on this.
Shimano BB compatibility #1
From: Jerry Teague
I can confirm that the Ultegra BB will fit Dura-Ace cranks - my mechanic buddies at Sigma Sport prefer to fit Ultegra where they can as it is easier to fit and maintain.
Shimano BB compatibility #2
From: Brian L Fancher
There are those, like me, who would quibble with your use of the term "upgrade." While technically true, supported by marginally better bearings, there are problems with the DA BB that you don't want. My experience (both first person and witnessing fellow riders) shows that it requires readjustment within 200-400 miles of the last adjustment. The pros, with their dedicated mechanics, can afford this kind of attention. Unless you plan on spending $$ having it adjusted weekly at your LBS, or can do so in your home workshop, either of which is a more or less expensive pain in the backside, I'd stick with the Ultegra. I prefer riding my bike to having it constantly in the shop. I spec'd an Ultegra bb on my newest titanium/carbon fiber/DA/Reynolds/ wonderbike for exactly this reason. For my $$, stick with the Ultegra. No dramas!
Sloping frames #1
From: Aki Sato
For a frame, fit is everything (well, after you decide what "style" of frame/ride you want, i.e. titanium, aluminum, carbon, etc.) I am 5'7", 29" inseam (short legs). I've always ridden frames which are too short in length because I can't straddle a taller than 51 cm frame. Even with a 51 cm frame, I can't use those old world "aero" posts (a la Campy) because the "aero" section would still be in the frame at my correct seat height. My ideal frame "style" is an aluminum frame with super short chainstays (my preference for sprinting). To fit, my frame needs to have a 50 cm seat tube and a 55 cm top tube. When I saw the spec's for the Giant TCR frame (size Medium), they matched my ideal specs. So I bought one. My seat post is at a standard height, I have a low 130mm stem (no spacers, 73 degree), and the bike fits me perfectly. I love the way the bike fits and it rides and handles great. No more toe clip (well, now shoe) overlap, no 140mm or 145mm stem that's still too short, and finally I have a normal headtube angle (and it handles better than the funky 70 degree ones on smaller frames).
If there is any flexibility in the "frame", it's in the fork. I have the stock 1" carbon steerer fork. The standard is 1 1/8" now, and even so, Giant is changing their fork - their fork blades are thicker for 2003. Apparently the ONCE team riders rode non-stock forks on their race bikes in 2002.
Finally a note on flexible seatposts and frame stiffness. Rider "un-suppleness" will cause all sorts of flex up top, whether it manifests itself as seatpost flex, rear suspension flex, bar/stem flex, even tire squishing. If the bottom bracket is a little more rigid on one frame than another, the frame will brace itself better against a rider's downstroke (and face it, that's when the most flex occurs). Now whether that power pushes the rider sideways on the saddle or the pedals down, that's a different question. But the stiffer bottom bracket will transfer more of the correctly-applied power to the chain and rear hub. It won't help smooth out a rough rider.
Sloping frames #2
From: Steve Cruickshank
Let's please dispel the idea that a compact frame lowers the Cg by any appreciable amount, as stated by James Whiteside. I agree that the compact design may lower the Cg of the frame itself by a few mm's, but the rider and their position is what really determines the Cg of the bike/rider system. Since the rider is in the same position, the Cg of the overall system will be essentially the same.
Washing waterproof garments #1
From: Brendan Moylan
Gore-Tex (and similar) clothing is usually treated with a "durable" water repellent (frequently referred to as "DWR") which encourages water to bead on the surface of the garment. The DWR is one of the first things to go - you will note that the fabric begins to absorb water - because wear and dirt/grease compromises the ability of the DWR to deal with water. WL Gore encourages you to tumble dry and/or iron the garment. As I understand it, this "refreshes" the DWR. The other thing to note is that Gore-Tex is a membrane which is sandwiched between the outer layer of the garment and the inner lining: when the DWR breaks down and the outer fabric begins to absorb water, the garment will feel clammy but if you feel the area no moisture actually gets through - the real effect is to make the garment heavier (and it doesn't look as good with big wet blotches, usually on high wear areas like cuffs, shoulder panels), although only marginally so.
I am not convinced Gore-Tex is such a great fabric for cycling - I have a Gore-Tex jacket which I wear if it really pours, but I find it just doesn't breathe fast enough so you end up with that boil in a bag feeling. I also have an Assos Prosline rain shell (which, according to my girlfriend, looks as though its made from condom latex) which breathes much better than Gore-Tex but is not as water resistant - although I would not want to crash in the Assos, its pretty thin and looks like it would tear pretty much instantly: the Gore Tex would be a little more robust.
I am interested to see whether manufacturers of cycling clothing jump on the soft shell bandwagon (e.g., Patagonia's Regulator series; Polartec Power Shield fabric), if they haven't done so already.
Washing waterproof garments #2
From: Steve Rempel
Interestingly, the manufacturers of my latest, non-laminate rain jacket recommend drying the jacket on a low heat setting to renew the waterproofing. That makes some sense to me - the idea of heating up the coating to make it more uniform, as it was when it was first applied. This clearly would not apply to laminated fabrics.
