From a data point of view, the braking of carbon rims is very specific to the manufacturer, so you will generally be best to do what they recommend. Our silica ceramic surface is actually slightly more agressive than aluminum when dry and about 96% as effective when wet when using the specific Zipp pad. Many rims like those from Corima, Campagnolo and many of the Taiwanese rims have a pure carbon surface at the brake track and you will need to use a cork pad so as not to damage the rim.

The cork pads are soft and have a low coefficient of friction, but will not damage the all carbon surface. For more aggressive braking a stock Shimano or Campy pad can work, but these contain abrasives such as aluminum oxide which can damage a pure carbon surface (aluminum oxide is the stuff they make sand paper from). Campy and Shimano pads will not damage a Zipp rim as our surface is very hard, but the Campy pads specifically are so agressive that they generate excessive heat and can melt, leaving melted brake pad on the rim, which is almost worse than wearing the rim out as the melted pad material can cause brake pulsation and can be very hard to remove.

Our pad is thermally conductive for lower temperatures, and will not melt, so it is very safe for any carbon rim, and works well on aluminum rims. Our pads also will not abrade your aluminum rims making them last longer, but for most any other carbon rim you are really safest to use cork which is completely non-abrasive, but really doesn't work well at all on aluminum rims.

Each manufacturer uses a different brake surface so you will find different solutions to each. Corima for instance uses a pure carbon surface with no brake surfacing, so only cork can be used as any other material will abrade through the carbon, especially when most stock brake pads contain aluminum oxide (sandpaper grit). The Cyclingnews.com guys seemed to have great results using Swisstop yellow pads on the Reynolds wheels, and I notice lots of the Pro guys that Reynolds sponsors using those same pads as well as cork. They also tell me our pads work well on Reynolds rims, but I haven't tested this in our lab so I'm not sure.

On our rims, the Swisstops look and work great, but our rim is considerably lighter at the perimeter than the Reynolds and when Phonak originally started using our wheels they had been using Swisstop and found that the yellow pads would melt onto the rims during high speed decents, very similar to what a Campagnolo pad will do (lighter rims get hotter with same energy input). So we still recommend either the Zipp pad or cork for Zipp rims. Cork pads are always safe because they are completely nonabrasive and do not generate heat due to their low coefficient of friction (they also don't stop so great, but that is the tradeoff). The Zipp pad contains highly thermally conductive carbon fibers to make is function as a heat sink and transfer heat into the brake caliper.

Overall, I would consult the manufacturer before using any pad as I know that some companies will not warranty use with some pads.

No special pads needed for your 404 clinchers, but we do recommend the Zipp pads as stock Campy and Shimano pads contain aluminum oxide, this is the same stuff they make sandpaper from and will both increase heat at the rim surface during braking as well as shorten rim life by effectively sanding the rim every time you use the brakes. The Zipp pads will both reduce temperatures and increase rim life on any rim, be it carbon or aluminum.

The short answer is they disipate heat better and don’t have any abrasives to shorten rim life. The long answere is we worked a deal with the fiber supplier for a company called Hitco, who makes the carbon/carbon rotors for F1 cars. The base fiber for an F1 brake rotor is a highly graphitized (nearly 3 times stiffer than PAN based 'medium modulus carbon') carbon material called mesophase PITCH carbon fiber, it is also very expensive (~$400/lb for the virgin material used in the brake rotors), but when they stack their plies, and cut them into discs, they have all these corners left over. We buy the off-cut corners (for less than $400/lb) and have them chopped into a specific length and then added to the resin during the pad molding. The upside of mesophase PITCH carbon is that it is very light, and has very high thermal conductivity (copper is roughly 400 w/mK and this material is over 900 w/mK!!!), so whereas a basic brake pad will have thermal conductivity on the order of 2 W/mK, the Zipp pad with 20% PITCH material has thermal conductivity of 20-25 W/mK.

This is also why we don't recommend using carbon pad holders with our rims or pads...the pads can conduct heat very well, but a carbon pad holder doesn't allow the pad to transfer the heat into the caliper. The best pad holders are Campy or Shimano as they have the wheel insertion fins on the bottom, that in our case now serve as cooling fins. If we had to buy virgin PITCH carbon material for these brake pads they would costs nearly $100 per pair at retail, so it is only through our former auto racing business and contacts that this product is even possible. No doubt that the pad can be improved (and we're working on it) but at this point these are the most highly researched and designed brake pads anybody has ever manufactured and unfortunately most people think that they are just the normal KoolStop black pads since we can't add any cool colors to them or anything as the carbon material makes them very black (normal black brake pads simply use carbon black powder for their color).

A resounding no. You have to understand the economics of a disc wheel. A tubular disc is very expensive as we have to essentially make a superlight carbon rim and then construct that into a disc. With the clincher disc we have to do the same thing with an aluminum clincher rim which is cheaper than a carbon rim, but then it has to be constructed into a disc as well, so the costs really aren't all that different.

The development costs aren't really that different either as you are assuming that the tubular development was fast and easy, it wasn't. Since the cost of the development of the dimpled composite process is attached to the tubular disc, the clincher disc could use considerable resources and wind tunnel time in development before getting close to the cost of the tubular disc development. All in all it took us some 2 years to develop and refine this clincher disc concept into something that worked as well as it does, but then again it took us nearly 3 years to determine the most effective dimple pattern, dimple shape, dimple depth, etc. then determine how to actually do the dimpled composite molding, and lastly how to construct the tooling since nobody had ever done it before, plus we filed patents for all of this which is very expensive.

The thing I don't see here is how or why anybody would think I have some vested interest in selling tubulars to everybody... we sell clinchers and tubulars for the same price because the manufactured costs are very similar (tubies have more carbon in them, so more labor in the layup process as well as more expensive materials, the clinchers use less carbon but the aluminum hoop does have to be completely prepped for bonding and post machined, both processes which add considerable labor cost so it is really a wash), so a wheelset is a wheelset as far as that goes, I'm just here relating some things I've seen and experienced in this business that may help some folks out instead of just confusing them with marketing gobledygook that some sales guy came up with.

More information on our exclusive co-molded carbon/aluminum clincher technology:
M2CM (Multi-Material Co-Molding) http://www.zipp.com/technologies/composite/m2cm.php

Are wheels like Zipps more comfortable to ride than your standard bomb proof training wheels, like the Ritchey's that came with my P2K? I keep hearing that its not the frame material, its more the wheels that impact comfort on bumps, so are all carbon, tubular wheels more comfortable than standard training hoops? I've been thinking about replacing my P2K with something all carbon in order to find something that is a little more compliant over rough roads (like my R2.5), but then I started wondering if maybe just getting a nice set of wheels might be better/cheaper.

Josh: The blanket statement that carbon is more comfortable than other materials is certainly a misnomer, but one of our rim patents on shape specifically covers using the rim shape to design and control vertical compliance within the rim. Essentially, the shape uses the sidewalls of the rim as vertically oriented leaf springs. Testing has shown this to reduce peak impact loads by roughly 12% compared to an aluminum rim (there is a beautiful graph of this on our website). Interesting feature of this is that the deeper the rim the more compliance you have, so the 303 is about 9% more comfortable, 404 is 12% more comfortable and 808 is about 15% more compliant.

Ultimately this provides a seat of the pants improvement in comfort that is equivalent of roughly 10 psi reduction in tire pressure, and adds more compliance (roughly 0.8mm in the 808) to the bike rider system than any frame we have ever tested.

This is the basis of our VCLC technology, where we are using interlaminar viscoelastic films to add damping to the rim system, as the basic carbon laminate has very little inherent damping properties (despite everybody justifying that new carbon rear triangle or fork to their wife by the superior damping of carbon... generally not true). Many bike manufacturers have been successful in making carbon comfortable using elaborate geometries, but remember that most rims are just V shaped, which is essentially a triangle, so you are using the stiffest material available and constructing it into the stiffest shape possible (in the vertical plane, this shape is actually quite a bit less stiff in bending than our shape), such that most carbon wheels actually show considerably higher vibration transmission than aluminum wheels.

Here’s a litle more infor on VCLC from our tech pages:
VCLC (Visco-Elastic Constrained Layer Control) http://www.zipp.com/technologies/composite/vclc.php

Since you really don’t want any company propaganda I'll spare all of you the PDF's of our catalog pages, but one of our key claims in our bulging rim shape patent covers vibration absorption and comfort. The two keys are rim shape and damping properties. Everybody wants to talk about how much damping properties carbon has, but the reality is that carbon fiber is generally excellent at attenuating vibration, hence ultra-high end audio companies are now using carbon in speaker cones due to the lack of damping, so the damping really has to come from either resin additives or interlaminar inserts.

The other key is that to have effective damping you have to have some compliance so you have to have a geometry that allows for some compliance, and our patent covers that geometry. So with our bulging rim shape a rim like the 404 tubular will have about 0.5mm compression between the tire bed and spoke bed of the rim with a 100 lb.in impact force. That 0.5mm isn't much, but is enough that combined with our interlaminar viscoelastic inserts it reduces the load transmitted to the hub by about 11% over a 30mm deep aluminum rim, it also allows the spoke tension to remain more consistent as the bottom spokes are not as detensioned during the impact.

Now, of course, you still want stiff wheels, so in our case, a 404 rim has similar vertical compliance as an older box section tubular rim built into a 28 hole wheel, and is considerably more compliant than a 30mm deep aluminum rim, while being laterally stiffer than either (the real benefit of carbon is stiffening one direction over another). Other manufacturers are limited to making rims that are more V or U shaped because of our patents, so by geometric limitations, these rims are very nearly rigid in vertical compression, and will get stiffer with increasing depth, the exception here are fairing type wheels like Hed Jet where the fairing is essentially nonstructural.

We have some killer video of various wheels on our bump tester, which is a machine with a big drum that has a pretty large bump on it. This machine is designed to test wheels to failure, and it is great at shredding spokes, hubs and rims, but we also use it to analyze frequency response of various wheels. Some wheels vibrate so badly that the entire machine looks out of focus and makes unbelievable noise, while some other rims run very quietly and without much drama. It was actually this phenomenon that started our cooperation with 3M Advance Polymers to work on our viscoelastic constrained layer technology. Hopefully we'll have this on our site in the next few months, but the answer to your question is an emphatic: Yes! Though it may be subtle in general riding, there are differences that are noticeable and important between wheels.

For more information on our VCLC technology, click here: VCLC (Visco-Elastic Constrained Layer Control)
http://www.zipp.com/technologies/composite/vclc.php

Since I'm biased on the sujbect I won't comment on whether our wheel are 'worth' it or not, but I'll provide some insight as to our costs.

The biggest cost factors in our wheels that nobody else has are related to two factors: 1. continual evolution and 2. US manufacturing and materials.

We are the only company with a continual evolution policy towards our wheels and rims, meaning that we continually research and then change rims or hub or whatever as quikcly as possible. The 404 for instance has now seen 5 shape evolutions and the addition of dimples in 6 years. This is unheard of in the industry where the other popular TT wheels have remained essentially unchanged for as many as 15 years. In 2000 our 404 was competitive with the Hed3 from 0-5 degrees in the wind tunnel and uncompetitive everywhere else.

The next year we evolved the shape to be slightly faster than the H3 from 0-8 degrees, but removed about 60 grams of weight. By 2005, the new dimpled shaped rims are significantly faster than an H3 from 0-22 degrees of yaw in the wind tunnel and lighter still. The problem here is that continued wind tunnel time and evolution of the rim shapes means that we can only ammortize tooling over 1 or maybe 2 years before we update to new tools. The evolution of dimples alone added about $40,000 to the cost of a rim tool, compared to a rim tool in China which will run about $1800 US, but I guarantee that as soon as we have a better 404, we'll be in production on it.

The same can be said for spokes, we were the first company to work with Sapim in Belgium and adopt the CX-Ray spoke, this is the world’s most expensive spoke at about $2.50 each, but is the most aero spoke we've ever seen in testing and, due to a special heat treatment, has more than double the fatigue life. People said we were nuts to use spokes this expensive, but two years later Campagnolo and Reynolds both went to the same spoke, thus rasing their wheel prices as well. Hubs are another example, we design and make our own hubs specifically for each wheel. This allows us to custom tailor the angle of each spoke hole to the depth of rim, and design the hubs into the wheel as a system instead of just buying off the shelf hubs.

We also use the industry's most expensive Swiss bearings, these are more than 2.5 times rounder than any bearing available elsewhere, and are rounder even than the ceramic bearings most companies are selling, but that comes at a price, we pay slightly more for the 6 cartridge bearings in a hubset than we could buy a completely assembled hubset from JoyTech in Taiwan. This is basically because precision and tolerance of parts comes at an exponential cost, so that you can buy 25 millionths balls by the kilo, 10 millionths balls are a few cents each, and the 1 millionths ceramic balls in the Z wheels cost about $6 per ball, so you are paying ever more for smaller and smaller gains, and this is true for an entire wheelset. Every last detail of a Zipp wheel is pushed to the limits of existing technology in terms of aerodynamics, strength, weight, stiffness and durability, but each incremental gain comes at a cost.

The other cost driver is US manufacturing and materials. We are dedicated to manufacturing in the US as we feel that we can evolve faster, and if engineering is 20 ft away from manufacturing we are better able to not only evolve the product, but solve problems when they arise. With Chinese or Taiwanese manufacturing it is very difficult to evolve the product since engineering and design are disconnected from production, not to mention if there are problems with a product you can be stuck waiting weeks for your shipment of parts from Asia to get it fixed where we can now just fix it ourselves very quickly. Being in Speedway, IN most of our people come from auto racing composites and make in 1 hour what a Taiwanese makes in a day or a chinese make in a week, labor cost is high, but our people have a high degree of expertise and most of them have been working with composite materials for years so you definitely get what you pay for.

Other than Trek, we are now the only carbon rim/wheel manufacturers in the US right now, so we face an uphill battle on costs, but I think that the quality and speed of evolution are well worth it. We also machine all of our hub parts in the US as we can use higher precision machinery and have more control over tolerancing and fits than is possible currently in Asia. This has allowed us to innovate new processes that would not have previously been possible, like using wire EDM to cut ratchet rings and pawls that are more than 2 times harder and more wear resistant than other technologies can produce, but at the same time more than 10 times more dimensionally accurate. The result is a hubset with a 180 gram rear and 82 gram front hub that spins with about 1 watt less energy input at 30mph than an other hub currently available and as much as 2-3 watts less than some. For many 1 watt is no big deal, but if you're Dave Zabriskie 1 watt was all it took to beat Lance in the Tour prologue last year, so in some instances it can be a very big deal (he also had ceramic bearings which can save another 0.5-0.8 watts).

But that brings up another key point, we do no specials, so a wheel for you or for Peter Reid or CSC or whatever, will be picked from the same production, off of the same hook and shipped without discrimination. Many of the pros use Z series stuff, which is more expensive still, but when a shipment goes to CSC for example, the wheels are simply pulled from inventory if we have it, or put into boxes as the wheels are finished and shipped right along side wheels for your local bike shop, there is no cherry picking or special manufacturing for those guys, as we feel that every single wheel should be pro-level.

Lastly, there is some cost in our event support, but we feel that this is very critical to our business model. We have people working tech support and supporting our product at every single US based Ironman event and many if not most of the other large regional Triathlons such as Wildflower and others, these same guys also work neutral support during these races so it is a pretty grueling schedule they keep. There is a definite cost to have two employess on the road dedicated to servicing racers and athletes as well as visiting bike shops, doing tech clinics and so on, but this keeps us connected to the market and so is very important.

For more information on Rim Shape and the aerodynamic “sweet spot” see our engineering white paper on rim shape: Rim Shape: (PDF)

For more information on hubs check out these two engineering white papers: A Note on Hubs

A Note on Bearing Technology

I think most of the pricing pricing debate you see among riders is largely the result of people comparing apples to oranges. The Hed Jet is simply an aluminum wheel with a carbon fairing bonded to the aluminum rim to add an aero component to the wheel. This is a very inexpensive way of making an aero wheel and has been used by numerous manufacturers to build an aero wheel at a very low cost. The Jet is simply a price point aero wheel and if you are going to make a comparison, you need to compare it to the FlashPoint wheels from Zipp, which at the same price point offer a better hub, DT spokes, and a fully structural carbon rim with welded aluminum hoop utilizing two of the patents also used in Zipp wheels. I think that when you put the Jet up against the FP wheels, the FP wheels are the clear choice, but that can be debated.

A more fair comparison would be between the Zipps and Stingers, although the Stinger uses the same hub as the Jet, which is not quite as nice as the hubset used in FlashPoint. The Zipp wheels use a hub which is made in the USA and to a level of precision higher even than Chris King, and actually costs slightly more than the King hubs due to the ABEC5/grade10 swiss bearings, these bearings alone cost more than a good hubset made in Asia and are higher grade than most ceramic bearing upgrades that people are offering. Combined with the Sapim CS-ray spoke, the world's most expensive and most fatigue resistant spoke, and the lightest handmade rims available and you end up with a very expensive wheelset. Every component is manufactured entirely in the USA from US materials except for the spokes from Belgium and Bearings from Switzerland, we use absolutely no Chinese labor or components, in fact two of the carbon fiber grades we use are considered 'defense critical' and only available in the US. This does make for a higher cost, but allows us to innovate continually and revise and improve much faster than using overseas manufacturing. For example, we made more than 10 laminate revisions this year as we found new materials, or new layup concepts, we can continually improve and innovate as our engineers are located 20 feet from the production floor, compared to working in Asia where you innovate only every 3-5 years.

In the last 5 years we have seen 4 rim shape revisions to the 404, the development of the 808, 5 generations of 303, the creation of dimpled composite technology (and with it the tooling manufacturing technology necessary to manufacture this), the first use of ceramic bearings in the bicycle industry in 2001. And we were the first company to push for the development and then adopt butted/bladed spokes plus numerous others inovations resulting in more than a dozen patents issued and pending. The hubs are another example, we made over 20 improvements to the hub in 2006 alone including the bicycle industry's first use of wire EDM for manufacturing of the drive components making the highest precision hardened components ever to be used on a bicycle in components that are rated at 60-62 Rockwell C with precision greater than 0.000002"...3 years ago this was technology so expensive is was only being used for surgical implants and missile guidance hardware manufacturing… but the result is that the rear is now only 176 grams and the front 80 grams and roll with the lowest rolling friction of any hub ever made, and in their stock form beat out every currently available ceramic hub upgrade.

So in defending our price point I think that you have to realize that we are doing something completely different from anybody else. We are creating, designing, and manufacturing our own product from scratch in our own facility, with an eye on absolute refinement, highest possible precision and greatest efficiency… and not focusing on hitting some specific price point where we say we want to make the fastest possible wheel for X dollars… that is what FlashPoint is for, with Zipp we go as hard as possible to create and develop technologies to be the best available without a primary consideration on cost, so when you buy Zipp you know that what you are paying for is the absolute height of technology available at the time you spend your money and nothing less.

There’s a few different tech articles on our website that go into more detail on some of these topics: Rim Shape:

(PDF)

A Note on Hubs (PDF)

A Note on Bearing Technology (PDF)

There are a million reasons that the prices have gone up, not the least of which are carbon shortages due to the aerospace boom and wage rates in this country added to skyrocketing insurance and other costs. Plus, our factory is located in Speedway, IN, surrounded by a half dozen autoracing composite shops, so all of our people are incredibly experienced, and are paid very well in order to keep them from moving accross the street to another job, the quality is worth it, but the cost is a multiple of what it would be elsewhere in the US. Here are some other factors:

The costs of raw carbon and aluminum materials are darn near spiraling out of control right now, with carbon nearly increasing 50% and aluminum practically doubling since last year, plus lead times nearly tripling for both materials, put us in a position where we have to pay significantly more for a material that we have to better forecast the usage of, and order and wait for months to receive. The result is the carrying of 2-3 times the inventory, of something that is already more expensive, and it snowballs from there. And while we have worked hard to cut our delivery times to dealers we’re still shooting to cut them even further. But our raw material vendors are pushing lead times further, so this means much higher internal costs for us. Also, we only utilize US made raw materials which are already between 50 and 100% more costly than their foreign counterparts, so these increases have really hit our company quite hard.

The only imported parts we do use are spokes and bearings, both of which are the most expensive in the industry by far. The CX-Ray spokes are nearly 4 times the cost of the next most expensive spoke, and our bearings cost between 8 and 12 times the industry average, meaning that a single bearing cartridge costs more than the 6 cartridges used in a traditional hubset, so when the dollar falls another 20% against the Euro, it really hits our company hard.

The bigger factor is development and tooling. Many people look at the dimples and say 'that added how much cost!?!' but it isn't that simple. We expect our products to be the highest technology, finest manufactured products in the world bar none, and to acheive that we continually develop and tweak the designs using wind tunnel testing, lab testing, pro racing, etc. From a business growth standpoint, our goal from 2000-2005 was to build a hands-down, no-doubt-about-it (in the customers mind, not just the tunnel) answer to the 3-spoke wheel. It’s hard as an analytical engineer to understand why, but peple view the 3 or 4 spoke wheels (now 15-year old designs in some cases) as super high technology – the appearance just seems tso racical, even if the results against the latest designes aren’t.

By 2001 we had developed the 404 to be nearly equal aerodynamically to these wheels. Each of the next few years saw new rim shapes and continued testing and now we have a 404 which is nearly 0.1lb less drag between 0 and 20 degrees of yaw over the venerable old trispoke, and makes roughly 1/2 the side force in a cross wind for better handling. The improvements with time are rather phenomenal, but take unbelievable time, money and resources to acheive (and then we went and developed the 808 to beat that…call us obsesive). In 4 years, we had spent a fortune, but realized our goal, and had developed a product that was really gaining an amazing following. The 303 and 404 each had 4 major rim shape revisions in the last 4 years, meaning that the entire company has retooled 4 times before this year, whereas many companies have designs which have remained the same for more than 10 years, which is a very excellent way to help manage costs, but is not the intent of our company.

The true story of the dimpled rims is not so much in the concept of the dimples themselves (which took a few dozen prototypes and some 50 hours of wind tunnel time), but in the tooling required to actually make the product. It took us 2 years to develop the dimpled disc tooling, and that is relatively simple as the disc is flat. It has taken us another 2 years to dimple rim tooling, and the actual processing is done by an aerospace tooling firm at prices which would truly shock you, but the result is something very radical and effective.

At the same time we’ve developed the dimples, we’ve also created the world's lightest crankset, added the 808 wheelset to the line, added an entire line of bars and stems, developed the most technologically advanced traditionally flanged hubset available and changed the face of track racing with the highest tech track hubset ever produced, all of which comes at considerable design and manufacturing costs.

Lastly, with the exception of the bars and stems, all our other product, wheels and hubs, are made in the USA, making us the only wheel company manufacturing it's own hubsets right here. This often overlooked part of the wheel has proven to be the lightest, most reliable, and smoothest spinning hub on the market, machined from only US made Alcoa materials (and certified materials at that) and machined to tolerances never before used in cycling components. The result when combined with the ultra-precision swiss bearings is a set of hubs which can save 1-2 watts of energy over any other hub available, and that single component has undergone more than 40 revisions in the last 12 months to make it smoother, lighter, etc. (not to mention a warranty/complaint rate nearly 40 times less than our previous Swiss made hubs)

In the end, there is more material cost and labor in a wheelset than in most frames, so in a way, they are still a relative bargain. I know that our company's philosophy and products won't appeal to everybody, but for us, the goal is to continually reinvent the medium, and push the product to places never before imagined. We have a pretty good history of this with the industry's first 3 spoke composite wheel, the Zipp 2001 frame, and now aerodynamically textured surfaces, which are already being used in clothing, frames, and elsewhere. I think that we have been successful in our desire to innovate, and hope that even if you don't purchase our products, that you will understand and respect our mission in the industry.

I think the mention of how well the products hold resale value is telling of not only the quality and durability of the products themselves, but also of how advanced the technologies are for their time, with 10 year old wheelsets still competitive in weight and aerodynamics to many currently available products today, if you download the technical white papers from our internet site, you will see that the thing we are most proud of is the dramatic improvements we've made not over our competitors, but over ourselves these last 4 years.

I’ll try to answer all three questions:

1) The increased impact strength is just for the tubular rims, the clincher rims are already nearly bullet proof and are quite popular with the 29" mtn bike which more than proves their durability. The 2007 tubular rims see about a dozen layup and material refinements which increase the strength with no weight penalty over the 2006 version.

Here’s a note on our Clincher Co-molding if you are curious: M2CM (Multi-Material Co-Molding) http://www.zipp.com/technologies/composite/m2cm.php

2) The zero stars for the 606 for training was a catalog mistake, it should have been 2 stars. We only recommend training on your aero wheels if you are training with power. Since most people train by speed or on group rides, training with your aero wheels just makes you ride less hard and burn fewer calories than training on std wheels, so we discourage training on any aero wheels unless you are training exclusively by power.

3) All of our rims are designed around a 21mm tire. When working in the wind tunnel or on the computer you have to choose a tire width to design around and we pick 21 as it is a nice blend of aerodynamics and low rolling resistance, plus it is a widely available size. We were the first company to really do this as previously all aero wheels were designed around 18 or 19mm tires, which I feel are just too narrow, two flat prone, and must be run at too high a pressure to prevent pinch flats that they ride harshly. You will see that most aero wheels see as much as a 20% decrease in efficiency when used with a 21 over a 19mm tire, whereas all of our stuff was designed around a 21mm tire to begin with and in most cases the Zipp with 21mm tire is faster than any other wheel with a 19mm tire. In testing done by Tour Magazine in Germany 4 of the top 5 wheels are Zipps including the top 3.

If these are clinchers the most important thing to check is the brake sidewall thickness. The sidewalls will wear away over time due to brake forces and a sort of sandpaper effect where the brake shoes either contain grit to make braking more aggressive (the two most likely options both have a mild abrasives in their pads, Kool Stop or Zipp pads do not) or the pads can trap dirt and grit from the environment causing this to happen. If you mountain bike much, you may have split a rim from over ridding it, where you just sand through the sidewall and the thing pops open one day with a big circumferential split around the rim, this can happen on road rims as well, but requires less material removal because the tire pressures are much higher, and consequently tends to fail much more violently than in the mtn. bike scenario.

The key thing to know would be what is the manufacturers initial rim width spec, and their minimum rim width spec. (if they have one) Most rims now have followed the new European standards and contain a groove or small hole in the rim sidewall that either wears away or shows through when the rim sidewall reached minimum thickness. Typically, the extra material in a rim to allow for wear is 0.010-0.015" (0.25-0.4mm) per side, so if your rim is more than 0.5mm thinner than when it was new, it's probably time to retire it, and if it is more than 0.8mm thinner than new, you should toss it (or get better health insurance).

This is still an issue on tubulars, but not nearly to the same effect due to the way the tire loads the rim.

Just a note on that cyclingnew.com article quoted. The reality is that since CSC is the only team where every rider gets full carbon wheels for every racing day of the year, they will break more carbon wheels than other teams, where the domestiques get heavy beater wheels and the whole team gets special Classics only wheels. Having said that, the team consistently tells us that they break fewer wheels overall than other teams, but far more carbon wheels as everybody else uses their carbon wheels so sparingly...

Breakages come generally from crashing and from the guys running to and from the team cars when they are completely unsighted by the cars and other riders, run off of the road, crashed, and generally otherwise abused. Remember, these guys are racing at 50 kph for 200 km at a time on roads that we would generaly consider to be nearly unridable. Also we discussed, but they failed to mention that the breakages are not simply broken and unridable wheels, but simply cracks in the rims. Of the 8 rims broken at Flanders, 4 of them were broken in crashes and 6 of the wheels were finished on an only discovered to be broken afterwards as the failures were simply cracks in the perimeter of the rim. Believe it or not the team was quite thrilled as most teams use their aluminum wheels for the one event and discard them aftarwards as they are generally bent, hopelessly out of true, stress-fractured and everything else you can imagine.

The mis-statement here is that the wheels will NOT eventually break until you hit something, crash them, or whatever. There is no fatigue type issues here with the wheels, so they only break when impacted or cracked due to some extreme stress. If you are just riding them and training on them and never crash or impact them sufficiently to break them, then they will not break due to fatigue.

For more information on how the consruction of Zipp’s rims click here: What Are Composites? http://www.zipp.com/technologies/composite/article_what_are_composites.php

M2CM (Multi-Material Co-Molding) http://www.zipp.com/technologies/composite/m2cm.php

VCLC (Visco-Elastic Constrained Layer Control) http://www.zipp.com/technologies/composite/vclc.php

The root problem with certifying carbon components is that there are infinitely more ways to screw up a part than just using cheap fabric, or a poor grade of yarn, or a bad resin system. This is one of the reasons that the aerospace industry has taken 15 years to print MIL-17 handbook, and now that it is out, we're still arguing about it. The reality is that poor layup technique, misalignment of unidirectional fibers, fabric wrinkles, or poor compaction could all lead to parts which are significantly weaker than design, much more so than using even the lowest grades of fiber. With otherwise perfect processing and technique you can find incremental improvements through using more exotic fibers, but the reality is that a part made with MR50 fiber (~$65 per pound) containing a wrinkle will likely be weaker than the same part made with T300 (~$15 per pound) containing no wrinkles. This is why aerospace has been so slow to really do large production with these materials. It takes longer to make the parts, and then every part has to be inspected 100% before shipping to ensure no errors were made, and when errors are made the entire part has to be scrapped and cannot be re-worked, unlike many metalic parts which can reworked in numerous ways to bring them back into spec, or re-heat treated, etc.

Furthermore, full design testing and validation cannot guarantee that future parts will be manufactured properly, so as an example with our handlebars and stems we have passed the most stringent testing at EFBe laboratories in Germany for fatigue and strength both, but the lab can only verify parts they actually test as every part is considered to be different. So we can validate the design, and through strict controls can control the production of the parts, but it's not so simple as with aluminum or steel forgings where you can test one piece from a heat treat lot and certify the batch as each part is made individually, and even though that's easy there is very little of this actually done in the cycling industry. This is similar to testing a weld, you can verify the skill of a welder, but that's not to say that he won't drink too much coffee and make a crap weld once in a while, or to say that some other issue like contamination can't creep into the process and comprimise the design. So you can validate a batch of tubing for example, but you still need to inspect every weld 100% to validate an individual frame as any given weld could have had an overheat or contamination issue which would not be present in 100% of the welds.

Lastly, with many parts and designs, there will exist no good non-destructive testing regime, so the only way to determine how strong a part will be is to actually break it... obviously this can't be done 100% or we wouldn't have anything to sell. So the next best thing is to batch parts by individual employee and material lot and perform statistical testing of 2-3 parts per 100 to ensure that the employee is producing consistent parts, again, this method cannot pick out a single bad part, but can pick out a process or individual that has strayed from design intent of the production. This is another reason that it is hard to be in the carbon business, if one person breaks one part, they are all over the internet talking about what garbage the part and the company and the engineers are, but the reality is that 99% of the time is is a very minute manufacturing glitch which led to a part failure and nothing more. Not that there aren't bad designs out there, there are, but even those are generally heavily overbuilt to satisfy some basic strength requirements, so your part may be heavy due to poor design, but it generally won't break because of it.

And bunnyman is right, 70/30 is about as high carbon content as you can reasonably acheive, as carbon content increases past this parts will actually get weaker as you will have resin starved areas within the part which act as failure zones. 50/50 is about he limit going the other direction, where you just lose too much stiffness and strength and are too resin rich to be producing a high performance product. And for the record, we use 5 grades of carbon specifically placed for strength, stiffness, impact toughness, hole reinforcement, and brake friction, so we no longer state what we use in the wheels, but the lowest strength/stiffness of all these would be equivalent to T800H/S from Toray and 1 of these materials used considered 'defense critical' and not available as a raw material outside of US borders.

For more information on Carbon construction check out the engineering white papers in our tech section:

What Are Composites? http://www.zipp.com/technologies/composite/article_what_are_composites.php

Woven Carbon vs. Unidirectional http://www.zipp.com/technologies/composite/woven.php

We have never recommended training on ANY aerowheel for the simple reason that many, if not most, people train by speed. Switching to aerowheels and training at the same speed for your event reduces your power output by up to 60 watts, and will also result in fewer calories burned, neither of which is desirable from a training standpoint. If you are training with power, then it doesn't make a difference, but you need to be aware that you are shooting for power number goals and not speed goals – otherwise you get home after riding 3 hours at 22.5 or whatever and wonder why your power downloads look so low.

As far as durability, our clincher rims are second to none in terms of strength, stiffness, and durabilty, which has earned them a bit of a cult phenomon status on 29" mtn bikes (something we highly don't recommend using our rims for!) http://forums.mtbr.com/showthread.php?t=29788 , as well as a stock 303 clincher holding the all time record for impact drum testing at the DT test laboratory in Switzerland, so if you want to train on them you will have no problems, but you must be aware of the potential pitfalls of training by speed only when using aero stuff. Since you are training and racing with power, I would recommend our 808PT option, the 808 only gives up 4 seconds per 40k to a disc wheel (according to Tour Magazine wind tunnel testing September 2005 as well as our own data) and is ultra durable, as well as available in clincher.

For more information on how Zipp rims are built – and what makes them so strong – check out the related engineering white papers in our tech section:

M2CM (Multi-Material Co-Molding) http://www.zipp.com/technologies/composite/m2cm.php

VCLC (Visco-Elastic Constrained Layer Control) http://www.zipp.com/technologies/composite/vclc.php

No need for the Pave in the clincher as the carbon body acts as a leaf spring under the aluminum hoop allowing the hoop to absorb significantly higher shock loads than a standard aluminum rim. This is why you will see Mike Curiak and other ultra-distance mountain bikers using standard 505 rims on 29" mtn bikes. They have found that the rims last much longer than even standard mountain rims while providing improved ride quality (as well as killer mud shedding capacity). And no, we will not warranty the rims when used like this, but as for any conceivable road/pave/cyclocross usage, the clincher 303/404 wheels are some of the strongest ever produced.

Pictures at: http://forum.slowtwitch.com/gforum.cgi?post=771857;search_string=joshatzipp;guest=10630024#771857

Here's the race palmares from the set of 404's shown in the photos according to Mike: When I first received them I laced them up to Hugi 240 rim-brake hubs with stout (DT Competition) spokes, then I rode the $#!& out of them that season. A smattering of the events they were used for that year: 2002 142-mile Kokopelli Trail Race--1st place 2002 360-mile Grand Loop race--DNF 2002 24 Hour World Championships--2nd place, singlespeed After that long summer of riding, guiding, and racing, tickled with their performance but tired of rim brakes, I relaced the 404 rims with DT Swiss 240s disc-brake hubs, SuperComp spokes, and fitted them onto a new frame for the next season. Highlights from that year included: 2003 Kokopelli Trail Race--1st place, course record 2003 Grand Loop--1st place, course record 2003 2500-mile Great Divide Race--DNF 2003 24 Hour World Championships--2nd place, singlespeed In all the training and racing miles I rarely needed to true or tension the wheels, so I concluded that they were as-yet overbuilt. Following that season I again relaced the same set of 404 rims, this time using very light (DT Swiss Revolution) spokes. Then I installed them onto a new frame and went racing. 2004 Kokopelli Trail Race--1st place, course record 2004 2500-mile Great Divide Race--1st place, course record 2004 Sweet Roll 200 race--DNF

For the record that's 10,400 offroad miles. We now have the rear in our factory and the front hangs at the DTSwiss headquarters in Colorado.

Here’s a little more information on our Co-molding technlogy: M2CM (Multi-Material Co-Molding) http://www.zipp.com/technologies/composite/m2cm.php