Zipp Z3 wheels in strong winds
Yesterday’s rainstorm with high winds gave way to a gloriously fresh and bright sunny day, with strong winds whipping the trees around and rapidly drying the roads. Not wanting to squander the opportunity for a dry-road ride in late December, I hopped on my Trek SSLX with the Zipp Z3 tubular wheelset and headed out into fierce headwinds. My exhilaration was apparently not shared by most cyclists, who must have stayed home for tamer pursuits. Road conditions ranged from constant small debris to chunks of wood, to a surface stripped bare of even the finest grit—rather fun as a change of pace.
The winds were strong enough to reduce my speed on a downhill stretch from its normal 27mph to a snail’s-pace 9.6mph while pedaling at a steady 300+ watts (according to my Ergomo power meter). Now, that’s a headwind!
The wind was nearly straight on (which made for a really fun return), but at times side gusts whipped into me. With winter clothing, and winter’s additional Personal Energy Storage Tissue, that makes about a 192 lb rider.
Windy gusts and Z3 wheelset behaviorThe Z3 wheelset behaved with aplomb, even when hit from the side by a few fierce gusts. As I wouldn’t really want to ride in any stronger winds, I’d say the Z3 wheelset, with its moderately “aero” rims is just fine even under winds strong enough to slow the average rider to 5-6mph. Riders weighing less than 150 pounds should probably consider pay strict attention however.
The Z3’s also showed exemplary behavior straight into the wind, with excellent stability and tracking.
The most comfortable winter jersey ever
I’ve tried a great variety of clothing for winter riding (“winter” here in the San Francisco Bay Area means anything from 30° F to 70°F). To date, I’ve had the best results layering a Merino wool IbexWear full-zip Shak top over a summer-weight jersey (a snug-fitting one, such as those made by Castelli), followed by a windbreaker or vest or jacket as temperatures dictated. The tight fit in the base layer is important to wick moisture away and to eliminate that clammy feeling caused by damp, loose fabric contacting the skin. The Shak jersey offers the perfect blend of wind-resistance and breathability—and it’s comfortable too. And it’s wool, so it keeps you as warm as can be reasonably expected, even when you’ve perspired heavily.
The Shak jersey gets my absolute highest rating, being one of the most comfortable and most useful tops I’ve ever owned, not just for cycling, but everyday wear, hiking, etc. I haven’t yet been able to persuade IbexWear to add cycling-style pockets—otherwise it would stand out as a first-rate cycling jersey all by itself. It still baffles me why companies that cater to hikers and climbers don’t understand the merits of pockets as found on cycling jerseys—I often wear a cycling jersey while hiking just for that reason.
As much as I love the base layer/Shak combination, I decided to try the Castelli Fortuna Themal Jersey. Wow! This jersey has a soft inner layer which is very pleasant on the skin, with a snug but comfortable fit. While the fabric is relatively thin, it offers the warmth of a double layer, with superb wicking and breathability. It’s not as warm as the base layer/Shak combination, but it’s perfect for the 52° - 62° temperature range, and a lightweight sleeveless vest extends that down to 46° or so. For colder temps, throw the Shak over it, and you’re comfy.
A lean and lightly-built friend of mine tells me his $300 wheelset is due to arrive anyday. He’s right—there are “good” wheelsets for that price, but I’ve never ridden any that work well for me, even at 3-4X the price (more on that below). He says:
Yeah, that's a problem with the lightweight wheels. Partly because the thin rim is flexy, partly because the skinny spokes are flexy.
Yup. And thin clincher rims also offer the intriguing possibility of having the tire blow off. No fun—I still have the scars (though my personal scrape was from Bontrager carbon fiber clincher rims, both now replaced by Bontrager, perhaps defective).
But for lightweight (< 140 pounds) or less powerful riders, there are more choices. A 190 pound rider like me (180 + clothing, water, etc) is 35% heavier than a 140 pound rider. So a wheelset will be under considerably less force with the lighter rider (which can lead to conflicting opinions about a wheelset). Finally, a few miles/kilometers per hour can also change the load on a wheel significantly (the component of velocity orthogonal to the wheel).
For example, I still have two sets of Bontrager Race X Lite aluminum wheels, which retail for around $1250 a set (one set came on my first road bike, and the other I bought used at a good price). But they handle so poorly that I don’t ride them any more—on a high speed turn, I’ll miss the apex by a foot or two, whereas the Zipp Z3 wheels hit the apex every time, with much less mental attention required. (My wheels are 2-3 years old now, perhaps the current models are improved).
The amount of mental attention required to execute a precise turn at higher speeds (20+ mph) is not to be underestimated, especially when fatigued, or there’s a pothole that appears out of nowhere! Missing an apex (turn in, apex, track out) can mean crossing the center line by a foot or two, a potentially fatal mistake. I’ll stick with a wheelset with no surprises, and skew the odds in my favor.
For two years, I didn’t realize that the reason I felt nervous on fast downhill turns was not due to lack of skill, but rather a too-flexible wheelset that threw me off my line. Accordingly, I always had to brake more than I wanted before entering the turn. This insight into the handling of wheelsets was realized only after I tried the Shimano scandium wheelset (WH-7801-SL), which is very stiff, offering superb handling on corners, but great discomfort on rough pavement.
Precise handling is largely derived from high lateral stiffness, or how much the wheel flexes and deforms under load when turning. Rim, spokes, hub and tire pressure all come into play, but if a wheel flexes, it’s not going to go where the rider intended. Air is cheap, so the tire pressure problem is easily rectified. On the other hand, a stiff tire and/or too high a pressure can cause a bounce or skip effect. This is one reason why high quality tubular tires, with their ultra-flexible casing and round profile, handle so well. The only clincher tire that I’ve ridden that can approach the tubular tires I’m now riding is the 130-140 gram Veloflex Record clincher, with a 350 thread-per-inch casing. As a bonus, tubular tires offer noticeably better comfort over rough pavement, even at somewhat higher pressures.
What makes a good wheel?
“Good” is more complex than something simply well made and reasonably durable. (And price is an orthogonal factor that muddies objective assessment, so consider it separately). Here is how I rank the factors in a “good” wheel:
- top-notch handling; high lateral stiffness with minimal mental effort required to execute precise high-speed turns—“intuitive” handling;
- comfort on rough pavement; comfort at the 100+ mile mark;
- light weight, especially the rim, rewarding acceleration;
- highest quality bearings that require little or no servicing for a long period of time, and with minimal drag (like the superlative ZIPP ceramic bearings in the Z3 wheelset);
- excellent aerodynamics for the chosen goal.
Few wheelsets can meet all of these criteria. The Zipp Z3 wheelset meets all of them (and no, I don’t work for Zipp, or get discounts, etc).
As an example, Shimano makes a scandium wheelset, the WH-7801-SL. I rode them for a few weeks, and found the handling to be first rate. Sprinting response was excellent. But they were extremely uncomfortable on rough pavement. Finally, they caused severe fork chatter under even modest braking on downhill grades (two bikes and two different tires). That’ll wake you up fast when it happens! Were those “good” wheels? Not for me.
Some people don’t “get it”: the pleasure of riding a responsive, light bike is worth paying for (and so is a pizza). There are a lot of stupid ways to spend money, but spending it on something you truly enjoy and that improves your mental and physical well-being is not one of them (provided you actually ride it).
Don’t judge value by the amount of glitzy crap you take home from the mall, or what other people think; judge it by how happy you are with your expenditure a year later. Some people never figure that out, so they’ll always spend no more than $300 on a mediocre wheelset (or even a whole bike!), then never use it because it’s heavy, slow, and unresponsive!
Always have dessert first, because tomorrow you might be hit by a bus. And if necessary, eat beans and rice for 6 months so that you can afford the bike or wheelset you’ve dreamed of. (Or whatever else turns you on).
Zipp Z3 wheelset and Veloflex Servizio Corse tires—impressions
I took my first ride on a new ZIPP Z3 wheelset today, with Veloflex Servizio Corse tires, glued-on expertly by Alan at Palo Alto Bicycles. It was Jeff at Palo Alto Bicycles who first introduced me to the incredible performance of the Z3 wheelset—thank you Jeff for understanding what I was after...see On Cycling above.
I had been riding Veloflex Criterium tires on my first Z3 wheelset since July 2006. Even as I took the first few pedal strokes, I noted the quickened responsiveness of the Z3/Servizio Corse combination as compared with the Z3/Criterium combination. Wow!
Later during the ride, I also observed a difference in the way the wheels handled; abrupt steering input causes the Trek SSLX to veer more quickly than with the Z3/Criterium combination. This is both a blessing and a liability; it is less stable (by about 15%, see further on), but it also means the handling is quicker. I prefer the quicker handling, which forces an improvement in one’s bike-handling skills, but is quite rewarding on twisty turns, or even veering around a stone.
Veloflex quotes 3,000km for the Criterium tubular (rear). My experience belies this; I wore a flat area well into my rear (tire) by about 1500km. It was nearly ready to be replaced when it was punctured, so I estimate a real life of no more than 2000km, unless you like riding on threads. Interestingly, the puncture sucked about 60psi out in a few seconds, but then I rode another 10 miles with the remaining 60psi. Go figure. By comparison, the front tire still looks nearly new; I’d estimate 4X the wear of the rear.
Wear factors: I’m optimistically 180 pounds (sans cycling gear), I do a lot of climbing, and I’m a fairly powerful rider (threshold 340 watts). So all those factors will wear tires more rapidly.
I wore out a Veloflex Record clincher rear tire in about 700 miles. Really wore it out; the tire developed a “thump” during a ride and the rubber started to pull apart. Since Veloflex only quotes 1000km (600 miles), I got my money’s worth. Great tire by the way—rides like a tubular.
Some people buy $3000 or $5000 or $7000 bikes and then complain about tire wear—c’mon! It’s $0.50 to $1.50 per mile (depreciation, gas, insurance, etc) here in California to drive a car. Get real—how many miles do you really ride each year? Ride the tires you really like riding. Replace them when they wear out. Ride your bike a few times instead of driving and you’ve just paid for a new set of tires for your bike.
A lot of manufacturers cheat on quoted tire weights. Maybe they weigh 100 samples, then choose the lightest one...! Of course, there is usually some tire-to-tire variation, which might depend on the batch.
Veloflex quotes 250 grams for the tubular Criterium, and 210 grams for the Servizio Corse. Don’t believe it—actual weights can be 10-20 grams higher. (Unfortunately, I neglected to weigh the Servizio Corse tires, so I can’t quote an actual weight for them).
I have a scientific scale good to 0.1 gram (and a higher capacity one good to 0.5 gram). A Veloflex Record tubular straight from the factory weighed in at 189 grams, versus a claimed weight of 180 grams.
A pre-glued spare Criterium tubular weighed in at 286 grams—sorry Veloflex, there isn’t 36 grams of glue on that tire! Gravity is actually a bit weaker in Italy than in California, but that accounts for only a tiny fraction of a gram.
Two Veloflex Record clincher tires weighed in at 138 grams each, versus a claimed weight of 130 grams. It seems that the real weight is about 5% higher than the quoted weight, at least for Veloflex.
Two Zipp tubular tires weighed in at 250.4 grams, and 271.8 grams. Same model tire, same order, double-checked—that’s an 8.5% variation.
Do these grams actually matter? Yes, these grams count for more than anything else on your bike. See below.
Does 70 grams of rotating weight matter?
With a rim weight of about 260 grams (unverified), the Zipp Z3 wheelset is exceptionally light in terms of rotating mass at the outer edge of the wheel, the most important area by far.
Remember that Kinetic Energy = 1/2*m*v^2 , so the kinetic energy in the wheel/tire required increases as the square of the velocity, in this case the velocity of the rim and tire. You, the rider, have to put that energy into the system (and battle friction as well). Because the tire also travels at a higher velocity than the rim, there is a higher energy cost for a gram in the tire vs a gram in the rim—and the contribution of the hub and most of the spokes is negligible. So reducing tire weight has a slight advantage over reducing rim weight.
I weighed my new set of Zipp Z3 wheelset upon arrival using a scientific scale accurate to 0.5 gram. Weights do not include skewers or tires, but do include the valve extenders in the little plastic baggies, still attached, as shipped straight from the factory:
front: 507 grams
rear: 611 grams
total: 1118 grams
On my first Z3 wheelset, I mounted Veloflex Criterium tires. These are quoted at 250 grams, but I weighed a pre-glued spare at 286 grams, so I estimate the actual weight is 280 grams. Since the tire is located even beyond the rim, its contribution is more than double that of the rim itself both because of its mass (280g vs 260g) and its velocity (faster than the rim, then squared). It’s unclear if the “rim” includes the aero portion; if so, then the rotating “weight” of the rim is even less than 260g. Or maybe it’s 300 grams—but it doesn’t matter much for the conclusions here.
On my 2nd Z3 wheelset (having made a solid commitment to riding tubulars, I wanted a 2nd choice of tires, plus backup), I mounted Veloflex Servizio Corse tires, quoted at 210 grams, or 70 grams lighter (per tire) than the Criteriums. Veloflex also makes the Record, quoted at 180 grams.
Simple calculation
Weight in the tire is more important than weight in the wheel, since the tire travels at a higher velocity, which is squared to determine the force required for acceleration. An approximation reveals that tire weight is at least 5% more important than rim weight (see details below the table). Call this “velocity weight”. (The actual difference will likely be more, since the rim weight is not all concentrated at its outer edge).
Weights below are realistic estimates of the actual tire weight, including glue (for tubulars). Actual figures might vary tire-by-tire; the conclusions remain the same.
| Rim Weight | Tire weight with 6g glue |
Tire “Velocity Weight” | Total “Velocity Weight” | |
| Criterium | 260 | 286 | 300 | 560 (+13%) |
| Servizio Corse | 260 | 226 | 237 | 497 |
The center-to-rim distance measured as 12.5 inches (diameter 25 inches). The tire was measured as 3/4" high. If the velocity of the outer edge of the rim is 100 (arbitrary units), then the velocity squared 3/8" inch from the rim is 103, and at the outer edge of the tire it’s 109. The weight distribution is an unknown, so we’ll use 5% as a rough measure of the increase in velocity squared for the tire, as compared with the rim. In other words, tire weight should be multiplied by about 5% to be “velocity equivalent” to weight in the rim.
The figures say there is only about a 13% difference between the two tires. It feels like more, but try wearing a backpack that’s “only” 13% of your body weight and you will find 13% a bit onerous to carry.
Follow-up on water bottle incident
I’ve received some new information on the thrown water bottle incident in Portola Valley, in which a pedestrian was injured:
- A vehicle was in front of the cycling pack, deliberately driving all the way over to the right—against the guardrail in an act of intimidation. The bicyclist had enough and threw the water bottle. It bounced off the roof, smacking into the pedestrian.
- The rider who threw the bottle was not an Alto Velo rider, and it was not an Alto Velo ride. But two of the riders who stopped to help were Alto Velo riders.
- Some of the Alto Velo riders are concerned that the good work of their group is going to be overlooked, and that the incident might effect funding by a major sponsor.
So it appears that the cyclist who threw the bottle quite probably was the victim of intimidation by a motorist with a deadly weapon (the vehicle). Given the number of recent “accidental” cyclist deaths caused by motorists in this area, the cyclist’s reaction hardly seems surprising. Such acts ought to be felonies, subject to serious punishment. That last sentence was a test—if you agreed with it and thought I was referring to the cyclist, you need your head and (morals) examined.
Nancy Baglietto’s letter to the Almanac, which railed against all cyclists, has not only impugned the wrong people, but they might well suffer consequences for it. She should be doubly ashamed of her bigoted and ignorant words, and if she has any personal integrity, should immediately take steps to apologize to cyclists in general (with a follow-up letter), as well as contacting Alto Velo to ensure that they aren’t unfairly treated for the actions of an unrelated cyclist.
Our laws don’t allow people to cry “fire!” in a crowded theatre. They don’t allow people to aim even a fake gun at someone and pretend they’re going to shoot them. They don’t allow death threats even by email! What would you do if someone capable of killing you in an instant decided to physically remind you of that fact? I’ve experienced close calls while cycling which almost certainly were intentional (though impossible to prove)—and it’s a chilling reminder of the callous attitudes of some individuals.
Perhaps non-cyclists can somehow overcome their cognitive dissonance on the foregoing, and insist that intimidation with a vehicle is somehow different than with a gun—such people are dangerous and complicit.
And the authorities are once again up to their usual laissez-faire sloppiness in ascertaining the real criminal behavior in such incidents (comments based on personal experience). Why was the driver of the vehicle not tracked down for questioning and treated like the criminal s/he is?
As a Portola Valley resident and avid cyclist, I’d like to respond to Nancy Baglietto’s letter in the Dec 6 Country Almanac.
First, I’m sorry to hear to that Mrs Baglietto was injured by the thrown water bottle. The responsible party was irresponsible.
From Mrs Baglietto’s ow
Pedestrian injured by thrown water bottle—a response
As a Portola Valley resident and avid cyclist, I’d like to respond to Nancy Baglietto’s letter in the Dec 6 Country Almanac.
First, I’m sorry to hear to that Mrs Baglietto was injured by the thrown water bottle. The responsible party was irresponsible.
From Mrs Baglietto’s own description it is clear that her injury was an accident—-no different in essence than any other accident on our roads, many of them far more severe. Mrs Baglietto seems to think that because it was caused by a cyclist it is particularly galling--as if injuries caused by a cyclist were any different than those due to a motorist. Her painful experience pales in comparison to the all-too-frequent *deaths* of cyclists on local roads by motorists wielding deadly weapons (vehicles).
One should ask whether a single individual’s actions are sufficient justification for slandering a broad group of people. Mrs Baglietto chose to use the plural in describing cyclists as “marauders”, who are “hostile”, “inconsiderate” and “negligent”. Characterizing an entire group that way goes beyond speech suitable for public discourse, to a self-indulgent form of hate speech which should be offensive to any fair-minded person. Unlike our neighboring city, Portola Valley has largely been spared such blatant bigotry.
Mrs. Baglietto, you owe me (and the cycling community) an apology. I am not responsible for your injuries, and I am courteous, cautious and considerate of pedestrians, equestrians, motorists and fellow cyclists. My water bottle is for drinking, and I almost never ride in a group.
I have had a number of negative experiences with vehicles while cycling. I've been hit, I've been cut off where a closer call would have been fatal, and many other simply annoying things. Neighbors do it to me. Physicians do it to me. Soccer moms in Suburbans on cell phones do it to me. I refer to *specific* incidents. But I don't castigate physicians, neighbors, soccer moms or Suburban drivers as a group--individuals are responsible for their actions.
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