Near the end of March of this year, a friend of mine and I were talking about life, bikes and racing. The day before, he had completed a really long, gruelling race on a cold drizzly day with gusty winds. He had worked hard to ensure that his designated leader was there in the finale, but his leader had stomach problems on one of the late climbs and eventually finished over 6 minutes down. He soldiered-on himself and finished 1:40 down...tough day at the office. Our conversation then turned to a favourite topic – wheels and tubulars.
Given the conditions before the start of that race, I was very surprised to hear that he had selected deep carbon wheels. Not just any deep wheels, mind you, but Hed 9 rims built-up on Dura-Ace hubs – both front and rear. Given the rain and the wind, not to mention one of the hairiest switchback descents on the calendar, I would have thought that a shallower wheel (or even a wheel with an alloy braking surface) might have been better. No, he said, they were fine, but then admitted that a shallower rim might have been preferable on the front, due to the switchbacks. That conversation really tweaked my interest in super-deep wheels. Since that day, he talked me into trying some out for myself.
The first question was ‘which wheel’. I have lots of 40ish mm-deep wheels of different types (Ambrosio X-Carbos, Mavic Cosmic Carbones, Lightweights, ADAs, etc.) I had always found that even rims of that depth to feel ‘squirrely’ in the wind. On his Team, it is a real mixed bag of wheels. Some of the guys ride Shimano DA 50 wheels, some Hed 4's, etc., so I was thinking of something like that. No, I was assured, don’t worry. The super-deep wheels would be fine. I relented and went with the Hed 9 on the rear, but given the fact that I was 9 or 10 kilos lighter than him, I chickened-out and went with the Hed 6 on the front.
The Hed 6/9 Rims
The wheels feature a hollow-core, all-carbon, tubular rim and braking surface design having a conventional steel spoke hole and nipple array at the trailing edge of the rim. The rims are called ‘Stinger’ by the manufacturer and offered as tubular-only. The manufacturer states that the rim is comprised of three different types of carbon and weave and that, combined with the manufacturer’s new lay-up schedule, results in a wheel that is 15% stiffer laterally, 10% more impact-resistant and 25g lighter than its previous Stinger offering. The rim has a cosmetic 3 or 4K twill weave on the exterior surface. The finish appears decent, if a bit ‘orange-peeled’ in the application of the final shot of clear. As an aside, the factory wheels have a very showy ‘Hed Stinger’ logo in red and silver that might ‘clash’ with the finish of many bikes. Unfortunately, the manufacturer has elected to put the decals under a clear coat, so removing the decals from the stock rims is likely not easy.
The final clear coat gave a bit of a matte look to the rims, which may or may not appeal to you, depending on the finish of your frameset. Given that the vast majority of the carbon used on road bikes (including components) appear to have shiny finishes, you may want to ‘polish’ the rims. You do not need to re-shoot the clear, though, just polish the rim with a series of progressively finer wet sandpaper. I did this myself and it turned-out quite nicely.
Of course, having been a 40ish mm rim guy for so many years, the first thing you notice about the rims is the massive depth. The Hed 9 is so deep, the Hed 6 looks positively shallow in comparison. You’ve heard the old adage: ‘looks fast standing still’? That’s the Hed 9. The Hed 6 alone, in comparison to a conventional 46mm-deep carbon wheel, looks very fast, too.
The second thing that is very noticeable is the shape of the rim itself. The profile of the rim walls is described by the manufacturer as a ‘toroid’, i.e., having an annular shape when viewed head-on from the leading edge. Basically, the rim shape differs from a ‘deep-V’ rim in this way: at some point during its course toward the trailing edge of the rim, the rim becomes wider than the leading edge. The toroidal shape is more evident on the Hed 9 rim than the 6. This ‘toroidal’ shape is the shape protected (formerly protected?) by a patent held jointly by Hed and Zipp. It is to this toroidal shaping that the manufacturer attributes its claim of the world’s fastest wheel.
The rim side walls comprising the toroidal shape appear to be very thin. Perhaps it is just that I am used to foam-filled rims, but I was very surprised at the amount of lateral movement of the rim walls that I could get by just squeezing them in with my fingers, especially on the Hed 9 rim.
The rim bed is also quite unusual, being both very deep and very wide. The manufacturer calls its rim bed design ‘C2’. Upon putting the wheel into the dropouts, the first thing you will notice is that, even with the brake calliper releases in the fully-open position, the wheel will not fit. This could be a problem for wheel swaps mid-race. As well as seating the tire into the rim very deeply, the rim necessitates some special tire considerations as it is also very wide.
The manufacturer specifies the use of a 23mm section tubular for the best aerodynamic effect. Notwithstanding the advice of the manufacturer, , I was advised by another Team also using these rims that a 23mm tire is not satisfactory for use on the rear wheel, as it is prone to pinch-flats due to the unusually high rim walls. That Team strongly recommended the use of a 25mm tire. Since I did not have any 25mm FMB or Dugasts on hand, I used a Continental Competition 25mm. I do not believe that this tire is commercially available, so rear tire availability may also be an issue with these rims (and if you take the advice of that Team over that of the manufacturer). With respect to the valve stems, I discovered to my dismay that I did not have a Vittoria extender (i.e., a valve core replacement extender) long enough for the Hed 9 rim (or a combination that did not make it stick-out so far that it looked stupid). I ended-up using a Zipp ‘sleeve-style’ extender that I had lying around. I put a very small dab of tubular glue on the upper thread of the valve to make sure that it does not vibrate closed and crossed my fingers.
As another aside, the Competition 25 tire had a new (to me) time of ‘mesh’ base tape (as opposed to the standard Conti twill base tape). I still have a lot of old Phonak and T-Mobile Conti Competitions in inventory, so I don’t know if this is just a ‘Team’ thing, but that base tape took a lot more glue to get a decent layer on it, especially because you need to put the glue so close to the edge of the base tape due to the rim bed depth.
The depth of the C2 rim bed also requires extra care and attention in the application of glue, as the very deep sides need several more passes than a typical rim to obtain complete and even coverage. I would recommend just using your finger wrapped in plastic film to ensure a good, even layer for each coat. Due to the depth of the rim, you need to also need apply the glue almost completely to the edge of the base tape.
Another potential downside of the very deep rim bed for some may be the physical installation of tires. If you have had difficulty mounting tires on a conventional rim in the past, I would recommend practising on the clean C2 rim first, to avoid a big mess.
The Hed rim valve holes were neither over or undersized and seemed to fit the Zipp extenders very snugly. There was no need to ‘force’ the stems into the rim, nor does the stem rattle around in the hole, even on very rough pavement. The valve hole was wide enough at the rim bed so as not to require ‘counter-sinking’ to avoid a tire-hop spot at the valve stem.
As compared to regular 22mm Continental Competition tires, the 25mm tire was a bit difficult to mount on a box-section rim to pre-stretch it (it took me about 10 minutes to get it on, but nothing like as tough as FMB or Dugast silks). Because of the relative difficulty that I had mounting it on a stretching rim and the depth of the C2 rim bed, I left it stretching for a week or so with 10 BAR in it. When it came time to mounting it, I had no problems. The tire went on simply and cleanly in about 30 seconds. Specifically, the very deep rim bed and the very high sidewalls were no impediment to the installation of the tire.
On the front, I had been given some new Continental GP4000s tires, which I had never seen before. They appear to be a Continental Competition carcass with a GP4000s tread on them. I had glued-up a set of Hed 6s for a friend and thought that they went on so nicely that I thought I would try them myself. I used a matching Zipp ‘sleeve-style’ extender. They went on very easily, too.
One thing that I noticed was that the C2 rim bed seemed to be easier to obtain a well-centred tire than a ‘conventional’ rim. This was not just an ‘optical illusion’ caused by the rim side walls coming higher up the tire sidewall either, as I never look at the sidewall to determine whether or not the tire is straight. Both the GP4000S and the Competition 25 tires seemed to require far less ‘fiddling-around’ to get them perfectly straight and centred than on a conventional rim bed.
Other Wheel Stuff
The wheelset was pre-laced to the stock Hed hubs, which appeared to be a high-end alloy set produced by some Asian jobber...nice, but certainly nothing special. The hubs are finished in gloss black with a silver-etched ‘Hed’ logo, the only identifying marks on the wheels. The freehub is a generic, alloy Shimano-compatible version. The spoke pattern itself is very conventional and utilises Sapim CX-Rays laced radially in the front, radial on the non-drive rear side and cross-two on the rear drive side (which I believe to be a ‘property’ built wheel, as another aside).
Since gluing-up the wheels, I have been testing them almost exclusively. To keep things as consistent as possible, I have been running them on one frame only. The set-up is:
• Bert’s 2009 Scott Addict SL
• Pressure: 100/110 psi (front/rear)
• Shimano 7900
• DA 7900 SRM with DA 7900 rings
• Corima cork pads
• Dura-Ace 11-25 cassette
• Shimano Dura-Ace skewers
Not being a TT rider, I have never owned a set of really deep wheels before. The very first thing that I noticed was the sound of the wheels. Even at 35kph cruising speeds, the wheels produce the most amazing ‘whooshing’ sound. Because the sound is very rhythmic, I would guess that the reason is the rider’s legs moving back and forth in front of the rear rim. When you start really riding and the pace goes over 40kmph, the sound is quite loud. If the wind conditions were calm, people who I was riding-up on the road would hear the wheels and look over their shoulder to see what was coming!
The next thing that one notices, is how light the wheels ‘feel’ in comparison to the expectation from simply handling them. Almost unbelievably, in my excitement I forgot to weigh them! Part of the light road ‘feel’ is no doubt due to the aerodynamics of the wheel, but they do feel similar to the other, much lighter, carbon wheels in my collection.
Among the ‘testing’ that I have been doing involves riding one of my interval courses. The course includes a short but steep climb that requires about 2 minutes to complete at a pace sustainable only for 7-9 laps. At its steepest section, the climb requires about 520 watts for me to keep on-top of 39x25 while seated. The back side includes a descent that ends in a sharp, reverse-camber corner on rough pavement. In my opinion, that type of course has everything that is needed to test a real-world, road racing wheelset at the outer limits of its handling characteristics.
As I had mentioned, the wheels feel very light at the pedals. While climbing, there was very little difference in pedal feel between the clearly heavier Heds and my Lightweights or ADAs, which surprised me. That has to be just an aerodynamic effect. Notwithstanding that the manufacturer claims that the wheels are more likely to ‘stall’ at under 30kmph, even climbing at 20kmph felt faster than conventional wheels, which would be in-keeping with a review of the available literature.
One of the other effects that I noticed is that the rear wheel seems to have a fair bit of flexibility. At first, I thought that it might have been related to the fat tire, however, at the steepest part of climbs the wheel was clearly flexing enough that the rear speed sensor magnet would tick the sensor as it went by. I played-around with the spacing, but I could not move the sensor far enough from the magnet to work reliably and still not hit the magnet any time I went over 400ish watts. As an aside, I was using a Weight Weenies-approved small, rare earth magnet glued to the side of the wheel. I solved this problem by simply gluing on a larger (½”x⅛”) rare earth magnet.
I am around 59kg, so I am probably not the best guy to speak to regarding wheel flex while sprinting, but I did put 1,200 watts through them without hitting the brake pads. During a recently-televised stage race, I noted that a very accomplished sprinter would undo the quick-release of the rear wheel on the run-up to winning the sprints. I imagine that was because his 1,580 watts (after 200km!) did result in the wheel rubbing the pads. I guess that there may be a double-edged sword to the flexibility of the wheels, though, because they do not feel like bone-shakers, rather, they had the nice, smooth feel of a box-section alloy rim.
We have a lot of frost heave here, which results in washboard pavement and corners covered in potholes. The Heds carved as nicely through those types of turns as any alloy wheel. Now, I don’t put all of the benefit of the ride characteristics of the wheel down to the rim, as I am sure the low-count steel spoke design deserves some of the credit. On the balance of the descents, the wheels also held their own. They felt sure and confident riding fast over rough pavement. The real test of any carbon wheel on the descent, though, has to be the effectiveness of the carbon braking surface.
The Hed wheels utilise a conventional carbon braking surface (as opposed to a Zipp-like coated surface or an ADA Kevlar surface). The combination of Corima cork pads, the Shimano 7900 callipers and levers and the Hed braking surface resulted in the confidence to late-brake into a sharp, bumpy, reverse camber corner commencing 25m from the base of a descent very close to my braking point for conventional alloy wheels. After 7 or 8 laps in 36°C, the braking was just as good at the end as at the beginning. The real test will come the week after next, as I will be heading up to the mountains for a block. I will have to post an update on how the wheels stand-up to a long mountain descent.
The thing that I had been most-concerned about with these wheels was the effect of the wind. I am pretty light and am blessed by living in the foothills of the Rocky Mountains. We are very well known for howling winds that come up out of the south and west. It is not uncommon to have 30 knot winds here. In the past, I have found my 46mm wheels to be ok in the wind, but I have found myself changing wheel sets before a ride in the past because I knew I would have problems with controlling the bike. So far, the most I have had is a blustery day with winds out of the south south west gusting 13-19 knots. I am definitely not comfortable on 46mm wheels in a 19 knot wind. I was not looking forward to riding these wheels in the wind, but I had to see how they were.
The performance of the wheels in the wind was the single biggest surprise that these wheels had to offer. For some reason, the 60mm front wheel seemed much more controllable than the 46mm wheel. In ‘regular’ wind (8-10 knots), I completely forgot I was riding an aero wheelset. I only talk about the front wheel because I could not tell any difference between the 90mm wheel and the 46mm wheel in the wind. I have to think that this is another aerodynamic effect. I feel so comfortable with the 60mm front that I am going to get a 90mm front wheel to see if I can ride that, too. For their performance in the wind alone, I would recommend these wheels to anyone.
Well, there you have it. I feel strongly enough about these wheels to have spent a bit of time recounting my experience. I don’t get into any debate about Hed vs. Zipp or deep-V vs. toroidal rims, but these rims certainly seem to do what the manufacturer says they will do.
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Last edited by Geoff on Fri Aug 13, 2010 1:07 am, edited 1 time in total.