Index Categories: 
    Wheel Aerodynamics – Wind tunnel testing vs. real world performance
Carbon Construction – Comfort of riding carbon rims

From:
spot Aug 4, 2006, 9:50 AM 

Question:
Realistic comfort improvement of carbon wheels?
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/VCLCViscoElasticConstrainedLayerControl/tabid/109/Default.aspx

Index Categories: 
    Wheel Aerodynamics – Wind tunnel testing vs. real world performance
    Wheel Selection – Which wheels for which use/course
Index Categories: 
    Carbon Construction – Comfort of riding carbon rims
    Carbon Construction – Impact strength of carbon rims

From:
GearGrinder  Feb 23, 2006, 4:24 PM

Question:
Aero wheels… some more comfortable than others?
 
What are some of the more comfortable options for and aero wheel (50mm+) over IM distances. I'm looking for a front wheel that is both aero but not so stiff that it will kick my ass for 7 hours. We know some wheels are stiffer than others, and are often marketed as such, so what have you guys found in terms of comfort?

HED Jet - Hed says they're great for long rides and all day comfort.

HED Stinger - stiffer than jets? Hed says super stiff.

HED trispoke - stiffest?

Zipp 404's, 808's

I'm looking for real world opinions, not just wheel company propoganda.

Josh:
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/VCLCViscoElasticConstrainedLayerControl/tabid/109/Default.aspx