The Zipp rim weighs a lot, even for a clincher (if memory serves it's over 550g per rim). You're basically adding almost 50% more mass then the snappiest climbing clincher rims, so taking that against the general consensus that a light rim is what makes a wheelset climbing friendly, and that's where my suggestion is coming from.
Perhaps more importantly though, I would caution against descending on heavy rims and carbon clincher brake tracks in general. There's loads of information on this site about the latter (from pulsing to complete blowouts), and I believe that trying to address the braking problem was likely the main reason Zipp made their brake tracks so thick/heavy... but from a control standpoint, these are going to want to hold speed and a straight line much more then the lighter wheelsets that people would normally consider for climbing.
If you know every corner and slope on every ride, then that's not too big an issue, as you can plan around it... though you might still need to brake earlier then friends and take things more conservatively. Howerver, if you ride 'unknown' descents, this will definitely up the pucker-factor.
If climbing is that important to you, get another wheelset and save these for TT's.
js wrote:Perhaps more importantly though, I would caution against descending on heavy rims and carbon clincher brake tracks in general.
If your climbing results in you making long and/or technical descents then stay away from carbon clinchers and carbon braking surfaces in general. The performance increase while climbing is not worth the risk on descents, even more so in the wet.
Amazing the number of people who turn up to ride mountainous European cyclo-sportives with their high performance carbon wheels and then wonder why they get problems.
Wet conditions are always different; carbon just can't match alu. Again, Zipp did well with the Firecrest, but it's still is a factor to consider.
Long and steep descents; my view is that you have to know yourself. If you're a Clydesdale and tend to go for the brakes often and long; carbon clinchers may not be for you. Carbon tubulars are fine. I don't run latex inner tubes on any clincher when sustained, heavy braking may be required. Another factor on descents is crosswind handling; Zipp claims the center of pressure on the Firecrest is ~located on the steering axis, making it stable. While I can't confirm the mechanism, my 81mm 808 front wheel does feel stable; although it clearly is affected by crosswind, the reaction is 'docile'. At least docile enough for this 65kg rider to use it in TT's with winds exceeding 45kmh.
The Firecrests are designed for aerodynamics, and remaining aerodynamic even with wider (i.e. 23mm) tires. Aero trumps weight in all but the steeper climbs. Considering the nature of this forum, you have to consider the weight. You can save half a kilo* spending the same money on a true climbers wheelset.
*assuming the 404 FC clincher
I love you guys. Seriously.
js wrote:They'll go 'round, but I think the answer would be that there are much, much better climbing wheelsets out there.
The Zipp rim weighs a lot, even for a clincher (if memory serves it's over 550g per rim). You're basically adding almost 50% more mass then the snappiest climbing clincher rims, so taking that against the general consensus that a light rim is what makes a wheelset climbing friendly, and that's where my suggestion is coming from..
Total weight is the only thing that matters - I can't believe there are people still promoting the fallacy that a lighter rim "spins up" or "climbs faster". An extra 300g or so makes no difference if the weight of bike plus rider is around 70kg or more. You are talking 0.4%! For all riding except stuff over 9%, aero matters more. Even then, the small increase in weight of an aero clincher rim over a "climbing wheelset" means bugger-all.
alexroseinnes wrote:An extra 300g or so makes no difference
What a horrible thing to say!
I appreciate that people have a difference of opinion here, and that's why I phrased things as I did ("so taking that against the general consensus that a light rim is what makes a wheelset climbing friendly..."). However, if you get a wheel spinning quickly in your hands and then try to change it's direction, you'll see that there is quite a bit of force resisting against a straight movement, which is more noticeable the heavier the rim. We're also seeing inertia assesments more and more often in wheel shootouts, as it seems a very quantifiable measure of performance.
If you don't think it matters that much or don't want to put any stock in it, that's totally okay with me. I respect that the numbers don't seem like a big deal against the total equation. But when I take a saddle pack off my bike, it feel lighter as I flick it back & forth, whether that's while climbing, sprinting or leaning it over through twisting descents... which is one of my favourite experiences in cycling. The weight of my saddle pack? - about 300g. Not a big difference against the total system (and not even a rotating weight), but it is noticeable enough that I only have it on when I'm working.
If you have to go clincher, a decent all round wheelset that looks the part would be the Mavic SLR with black rim.
Stiff, Light, Aero - Pick Three!!
Momo wrote:I am interested in the new Firecrest design from Zipp and was curious if anyone had experience using them for climbing. Living in AZ. I ride Mt. Lemmon with an average grade of 5% and a few other routes that range from 12 to 14%. I'm building up an SL3 and wanted an all around wheelset that can do it all.
Do you want a good all round wheel set or a good climbing wheel set?
As others have said, the 404 carbon clincher is not the ideal climbing wheel. However, given your preference for an all-around wheel I would say it could suit your needs quite well.
Regarding some of the points raised in the previous thread, the mass difference between the Enve 45s and the 404s is not as large as stated (actually over 25% less than stated), even going by claimed mass much less actual mass of test parts I've received. Regardless, inertial effects are much less significant than many believe, as they're only of relevance when accelerating (either in the axis of rider travel or when steering). I think we're all beyond examining micro-accelerations, and unless you're pulling Contador-esque multiple attacks in short order, inertia is highly overrated as far as critical performance metrics are concerned. Magazines love to include measurements of inertia as it's easily and inexpensively measured. This, however, does not imply its significance for many riding situations, and note that a 25% increase in a small number is a very small number (just taking an example from the previous thread purely at face value).
Addressing the issue of overall mass separately, our models have shown that a savings of 1 Watt via aerodynamic improvement equates to saving roughly 340 grams of mass for a rider on an 8% grade. This can also be verified via analyticcyling for anyone so inclined, or perhaps djconnel will interject. Regardless, this 340 gram savings resolves out to an actual resistance on the order of 30 grams in the direction of rider travel; obviously, this resolves to different values depending on the incline.
This is a difficult discussion that we've had with several of our pro riders...on some of the long stages in grand tours having multiple cols, they always want to ride 202s (see Carlos Sastre, Alberto Contador). However, if you look at the entirety of the stage, typically including long descents and stretches on the flats, their overall wattage savings would actually be higher with something like a 303 or even a 404. However, they invariably select the lighter wheel going either for just reduced mass in general or ensuring that inertia is as low as possible for that critical attack coming out of a switchback.
This overall savings with the deeper, heavier wheel occurs because aerodynamic savings will remain constant with velocity and no rider position and are generally of a much greater magnitude, even at lower velocities and generally higher effective yaw angles seen by most riders that aren't doping. The Hyperon was mentioned as a possible candidate but is somehow even less aerodynamic than a Ksyrium (I don't know, but the numbers don't lie), more than offsetting its lower mass relative to the 404. The plot below depicts drag force in grams (sorry djconnel) as a function of effective yaw angle. The same Vittoria 20mm Corsa Evo-Cx tire is used on each wheel, 4 runs each. Unfortunately, our database software doesn't display error bars but typical run-to-run variation is inside of 5-10 grams across the yaw range. Test velocity is 50 km/hr, which is obviously far in excess of most riders' typical climbing velocity but easily scaled to whatever speed you like. Standard conditions and pressure.
These drag savings, even on the lower end of likely effective yaw angles, are an order of magnitude higher than the losses associated with the added mass of the 404 carbon clincher. The savings are reduced approximately 35% (and this varies depending on effective yaw angle) if you look at something like a Lightweight.
Most climbs I've done have a descent associated with them as well, and this is where the 404 carbon clincher will really shine. Over the past three years we've done extensive studies on refining stability in side force in terms of magnitudes of the side force itself, shedding vortices and the frequency thereof as it relates to the natural frequency of the rider/bike system, and the reversal of yaw torque. Much of this is covered in some of the CFD results that have been independently presented independently and is available in various places throughout the web; I believe some of the AIAA info is freely viewed but don't have time to dig for it just now. There's a brief description of some of the outcomes of these stuides in a mini-doumentary on our youtube channel that should shed some light on these issues for anyone that's interested: http://www.youtube.com/user/zippspeed
Lastly, our resin system used in the carbon clinchers was specifically developed with our supplier, as our lab and field testing revealed problems with several existing products that have been documented here and elsewhere on the internet. As we finalized an entirely new process of fabricating and molding rims and settled upon the resin system, we found that the glass transition temperature of our resin system is a minimum of 100〫Fahrenheit higher than any product currently on the market, and we did extensive work with our FLIR infrared camera to evaluate iterations of surface treatments and pad materials to ensure that we were dissipating heat as rapidly as possible. To date, we have yet to experience a field failure due to heat; that said, we're continuing to refine the process, material usage, and pad compounds to see if we can remove some mass from the rims, and in tandem we are refining the field and lab testing to ensure that any reductions don't adversely affect performance or durability for the end user. As many here know, engineering is about compromises, and in our case we elected to design for robustness; while we knew we were perhaps erring on the side of caution with our final production product and it is slightly heavier than competitive product of a similar depth, its durability thus far speaks for itself.
I hope that addresses some of the questions you had, Momo. If not, feel free to PM me as that is the best way to ensure a quick response.
EDITED for clarity and typos.
With the completion of my build nearing and budget, I would like to get wheelset that will suit a variety of riding situations. I appreciate all the great insights on wheels.
Great forum and thanks again!!
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