Index Categories:
Carbon Construction – Impact strength of carbon rims
Tires – Effects of Tire width on aerodynamics
From:
bobcowin Dec 31, 2006, 5:13 PM
Question:
Zipp durability and speed questions.Almost a year after buying my P2C I’m ready to buy a set of race wheels! I am planning on getting a set of Zipp 606 clinchers. But first three questions:
1) According to the 2007 Zipp catalog the rims for 2007 are stronger than last year (“Our ITC carbon lay-up technology is the envy of the cycling industry and we have further upped the ante by increasing damage tolerance of the rims by nearly 50% over the previous design for 2007.”) Would this apply to the tubular wheels only?
I will have to order the wheels, so how will I be able to distinguish the 2007 from older wheels?
2) Also, according to their website they consider the 404 OK for training, getting 3 stars, but not the 606, getting zero stars. Is the 808 rear not at all suitable for training? I don’t plan on training all the time with them, but I believe in training on what you plan to on race on.
3) Zipp sells only 21mm tires (tubular and clinchers) and it seems that it’s the recommended size to use (“21mm width is the optimal blend of aerodynamics, rolling resistance and durability”). I wasn't planning on using Zipp tires, but I'm curious about the 21 mm vs. 23 mm. Any comments from anyone with more experience?
Josh:
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 the basics of our carbon layup process if you are interested:
ICT (Inversion Composite Technology)
http://www.zipp.com/Technology/CompositeTechnologies/ICTInversionCompositeTechnology/tabid/97/Default.aspxAnd here’s a note on our Clincher Co-molding if you are curious:
M2CM (Multi-Material Co-Molding)
http://www.zipp.com/M2CMMultiMaterialCoMolding/tabid/101/Default.aspx
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.
Aero Wheel Comparison Article (Tour Magazine)
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Carbon Construction – Impact strength and durability of carbon rims
From:
Jim Mishler Jan 19, 2005, 1:06 PM
Question:
Wheel lifespan? I'm running a pair of 9 year old Spinergy Rev-X on my Slingshot. I've never had any negative issues with them and they've carried me over lots of miles. But 9 years old is just that. Can you offer any thoughts on whether I can keep going with them or do they need to be replaced?
Josh:
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.
Index Categories:
Carbon Construction – Impact strength and durability of carbon rims
From:
trvfsub2 Nov 6, 2005, 6:01 PM
Question:
Zipp 404, everyday wheel?Would anyone use this as an everyday wheel and race with it? Would solve the problem as I could just get the PT installed and ride and race with one set of wheels.
Any thoughts?? Or say ride it as your long ride and maybe your other interval ride of the week?
It seems like Zipp admitted here it is not best to do too many miles on your Zipps ;
http://www.cyclingnews.com/tech.php?id=tech/2005/reviews/zipp_404Josh:
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/Technology/CompositeTechnologies/WhatAreComposites/tabid/98/Default.aspxICT (Inversion Composite Technology)
http://www.zipp.com/Technology/CompositeTechnologies/ICTInversionCompositeTechnology/tabid/97/Default.aspxM2CM (Multi-Material Co-Molding)
http://www.zipp.com/M2CMMultiMaterialCoMolding/tabid/101/Default.aspxVCLC (Visco-Elastic Constrained Layer Control)
http://www.zipp.com/VCLCViscoElasticConstrainedLayerControl/tabid/109/Default.aspx
Index Categories:
Carbon Construction – Impact strength and durability of carbon rims
From:
Ian MacLean Feb 10, 2005, 8:45 AM
Question:
Time for Carbon to prove itself ?I haven't read ALL the posts regarding carbon lately, just skimmed through them so forgive me if I am repeating somebody. I haven't seen much mention of the lack of consistent, measurable construction with generally accepted principles on how to quantify the carbon. Allow me to explain.
With steel, we have SLX, we have Reynolds 843 etc. With aluminum we have 6000 or 7000 series, we have easton ultralite, we have Deda U2, we have Columbus Starship. For TI there is 3/2.5 and 6/4. We have cold forged, heat treated, seamed or not. Single Butted, Double Butted, etc. These are all Industry standards for the respective tubes, and it's pretty easy to find a wide and agreeable consensus as to what all those things mean to the integrity of the tubes and how they affect ride quality.
We don't have any of that with carbon right now. We have companies that are marketing "carbon" bars and seatposts that are simply aluminum wrapped in a thin layer of carbon. We have carbon that is 90% carbon and 10% epoxy, and we have carbon that is 50-50 and anywhere in between. The problem is, we as consumers and retailers don't really know what is what...yet. And therein lies the problem. A carbon frame that is 50-50 carbon to epoxy/resin is going to have a harsher ride than a good aluminum frame in many cases.
This is what I mean when I talk to people about carbon proving itself. There needs to be industry standards available for consumers and retailers to measure the true worth and value of carbon frames and components. I think we'll see it start to happen in the next couple of years as the smart companies realize that they need to distance themselves from the cheap "barely-carbon" carbon components that are starting to flood the market.
Josh:
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/Technology/CompositeTechnologies/WhatAreComposites/tabid/98/Default.aspx
Woven Carbon vs. Unidirectional
http://www.zipp.com/Technology/CompositeTechnologies/WovenCarbonvsUnidirectional/tabid/99/Default.aspxIndex Categories:
Carbon Construction – Impact strength and durability of carbon rims
From:
JohnA Sep 12, 2005, 8:31 PM
Question:
Pick a rim for my Power TapAfter seeing OT in CA's stellar performance at Big Kahuna (2nd in the 30-34AG) I have decided to sell off my Zipps (very sad to actually type this) and buy a PowerTap for racing and training.
So far I have decided to get a PowerTap SL, 28 spokes, but what rim?
Here's what I'm looking at:
Velocity Aerohead with a CH wheel cover for race day.
Pro: Lighest option, would match my front wheel
Con: Not as strong as the Mavic or Deep V
Mavic CXP33 with a CH wheel cover for race day or no cover for windy days.
Pro: Stiffer than the Aerohead, lighter than the Deep V or the Zipp 404.
Con: No big aero advantage for windy days, but better than the aerohead... Heavy,
Zipp 404 clincher with a wheel cover for race day or no cover for windy/hilly days.
Pro: Stiff, real aero advantage no matter the wind conditions.
Con: Do you really want to train on a Zipp wheel? Really?
What do you guys think? I think I already know the answer...
Josh:
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:
ICT (Inversion Composite Technology)
http://www.zipp.com/Technology/CompositeTechnologies/ICTInversionCompositeTechnology/tabid/97/Default.aspxM2CM (Multi-Material Co-Molding)
http://www.zipp.com/M2CMMultiMaterialCoMolding/tabid/101/Default.aspxVCLC (Visco-Elastic Constrained Layer Control)
http://www.zipp.com/VCLCViscoElasticConstrainedLayerControl/tabid/109/Default.aspx