I'll add this, I take great pride in the data here that 2 months after we launched Firecrest technology, ENVE got serious about aero, locked in a consultant with some good aero credibility and spent 12 months and a lot of money more or less recreating almost exactly: Firecrest (further Kudos to them for making the rims in the US) Whatever that quote is about mimicry being the sincerest form of flattery holds here...I really hate that we have so quickly been followed by this and numerous others, but it really does speak to how amazing this technology truly is, we use the phrase game-changer a lot, but here it actually fits. Firecrest is the modern equivalent of the P3 wheel cuttout, it's just plain better, and everybody wants a piece, and everybody has to stake their claim to some nuance which makes them different.
Now onto the question at hand:
I am not sure how they intend for us to read the handling graph, and the wheels are not available to test, but the idea that having a shallower rim up front to improve stability has made sense forever, just as it did when we sold a 404 front/808 rear as the 606 wheelset beginning in 2004. The one I'm not sure of is the the plot of 'Steer metric' and how that plot represents more stable performance, but I do have to give credit to them for this work, and for publishing data on this. Since we launched Firecrest, 4 different manufacturers have begun touting 'Stability' as a design feature, and not one has been able to discuss how stability was improved, or what was done to improve it, there are even quite a few products that have 'stability' technologies associated with them today that are no different than they were previously, so at least Enve didn't just put a sticker on the wheel they appear to have put some thought into it.
I know that the papers written by Matt Godo of Intelligent Light have made the rounds here, you can search if needed, we worked in depth with Matt on the design of Firecrest technology, as it was his 2008 paper on wheel CFD that set me thinking about wheel stability in the first place (we have since collaborated with him on a number of papers available online). We ultimately built our own tunnel balance to replicate what we could learn from the CFD and with the Firecrest launch, really launched the idea of stability tuning for wheels...now having said all of that, once we realized we could manipulate the yaw torque, the burden on us was to figure out what was 'best'. We were able to create versions of Firecrest that had positive yaw torque (this is normal, the wheel steers with the wind), negative yaw torque (self correcting) and wheels that were very neutral...now of course, different yaw angles and different wind speeds affect this...one thing we found was that some wheels like our own 1080, the S9 and most all 3 spoke wheels would actually reverse behavior beyond some angles, so you may have positive torque to a point, and then suddenly negative beyond some wind angle...not good. From this we created ridable prototypes, basically the same plastic prototypes we've used for 10 years (just like what Enve is showing) but we developed a technique to make them fully structural...2 years ago we published a great photo of a rider riding the Firecrest prototypes in the tunnel...those aren't just plastic afterall! From that we ultimately decided that the neutral handling wheel was what people liked (as well as creating real world data sets using powermeters, but that's another story) ..and you see it in the Enve data, the 404 really does exhibit nearly identical torque response to a box section rim...and that is a very low torque, which in turn requires very little rider energy to correct. I find it ironic that Rappstar a few weeks ago told somebody that the 808 handles like the old 404 and the new 404 handles like a box section rim...it was one thing for me to agree with him, but even better to hear it from a third party! The final piece of the stability equation that we created relates to the harmonic shedding frequency of air off of the wheel...this was really the last piece of the puzzle and something that we learned our own dimples to be very beneficial for...though that was not their initial intention. This is lightly covered in the mini-documentary on Firecrest posted here:
http://www.youtube.com/user/zippspeed and includes the never before seen footage of the CFD models showing the flow shedding behavior. I don't want to come across as advertising or blatant marketing, but there is some amazing stuff in there that has never before been shown. All in all, one of the coolest aspects of the Firecrest project was the sort of basic science work done with Intelligent Light, that has been published in 4 papers before the AIAA, and really has advanced the general understanding of these affects. I would post the time in the video where the CFD stuff is, but I haven't seen it as I can't stand to see or hear myself...so I welcome anybody posting that info to the thread if you'd like.
Now back to the science, as I said before, when you break ground like this, there is a real burden try and figure out what is beneficial...and then that becomes the conventional wisdom, but at the time we were learning all of this it really wasn't very obvious what should be done or even what could be done to move the center or pressure around. One thing we knew was that certain wheels just didn't handle well, and we learned that they all shared similar characteristics, high positive yaw torque (or positive yaw torque that reversed with increased wind angle) and low shedding frequencies (a few wheels showed high negative yaw torque AND low shedding frequency and that was not good either!). These shedding frequencies could get very near the natural frequency of the bike...some as low as 2 Hz..which is more or less the frequency of speed wobble! We found that the dimples help the air 'round the corner' on the trailing edge of the front half of the rim, but that the dimples in conjunction with the Firecrest shape were a real game-changer in this area, natural frequencies for Firecrest rims are generally between 20 and 40Hz, which is well above the natural frequency of the bike/rider system (in that particular axis..) and the magnitudes of the lateral forces resulting from this shedding (and consequently the torque the forces result in..) are significantly lower than in traditional systems.
Lastly, let's talk drag. Simon Smart is spot on in his assertion that the wheels will behave differently in different forks/frames, and his method of testing with different road frames and TT frames is exactly what we have been advocating and doing for some time. The problem is that if you added 4 more frames, you would have 4 more answers...these frames do not represent bookends, but are simply points along a continuum of the available frames on the market. Once you are fully optimized, the conditions are such that tweaks that make the wheels better in one frame will cost you drag in another. Same for the bike only vs mannequin, vs pedalling mannequin...you end up adding astronomical cost to learn that you ultimately have to pick between 3-4 options that could each be argued to be the best depending on what bike YOU are riding at the time (or want to show in your marketing). My guarantee is that had they tested bike only or using Speedplay's dynamic mannequin, the results would not change and no new product direction would have resulted...we have tried all of that stuff and you just end up adding a LOT of noise and uncertainty to the data and the engineers still have to make some really hard choices over what the the best compromise will be relative to the actual bikes that actual customers are likely to have... and that doesn't even mention the issue of tires, which can be every bit as large as the differences between frames!
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