Depends, you want a narrow or wider rim?

Mine is trimmed at the edge for a 30mm rim, and at the hub for a powertap hub. Total weight with aluminum fasteners is 460g (roughly 1lb.). Trimmed for a deeper rim like an Alpes it'd be slightly lighter.

Can anybody show me any test data that (using a low Crr tire/tube combo) a wider rim/wider tire combo is actually "faster" than an appropriately chosen narrow rim/narrow tire combo?

---

http://bikeblather.blogspot.com/

What about durablility? Both wheels are pretty equal as far as I can see or atleast within my racing. A couple seconds is close enough for me Ill just go ride more. Which one will last the longest?

Ive seen data that suggests there is no difference.

Can you share that data or tell us where to find it?

Im pretty sure I remember reading it at BTR.
Ill try and have a look for it later today and see what I can find.

Did you ever find this data?

While we wait on data, I'm wondering if there is even any theoretical reason to think this matters. HED clearly seems to be moving all their products to the wider rim. Is this solely a marketing thing (set their wheels apart from the comp)? Even if it isn't any more aero HED seems to be saying that it is a much more comfortable ride so even if the aero-ness is a wash the added comfort (they say) is the advantage. Any evidence (not anectdotal) to back these claims up?

OK ... you asked for anecdotal. Here goes:

I don't think anyone at HED ever said the C2 rim was more aero. They may contend that it works well with the torroidal rim bulge, but I don't think I've read "more aero" anywhere in anything from HED. Maybe I'm just not remembering.

The idea of a wider rim is supposed to be less rolling resistance and more "adhesion" for cornering. Since the adhesion thing has little relevance in TTs and triathlons, lets focus on the rolling resistance claim. Here I think the argument is based on the shape of the contact patch where the tire meets the road. In a skinnier tire, the contact patch is longer and more narrow ... more contact with the surface IN THE PLANE OF MOTION or in the line of motion. But with a wider tire, the contact patch is wider and less long. Less contact with the ground in the plane or line of motion.

Add to this that they encourage running only 80 to 100 psi on these wheels. Not because it's all they can handle, but because they believe it's optimal for both rolling resistance and adhesion ... following the line of thinking that the more the tire conforms to the road surface, the more your energy is put toward forward motion rather than toward bouncing around on the road surface.

I believe the above is a fair synthesis of what I've read about the concepts behind the C2 rims.

I recently acquired a HED Jet 90 C2 front wheel and a standard width Jet disc. (Couldn't do the C2 on the rear because of tight clearances between my P3C chainstays.) I've done three races since ... won all three and set new PRs in two of them (the third I raced in driving rain and wind). The PRs were by significant amounts ... 3 minutes for a HIM relay bike split and a full minute in a 40k TT. But I also have a new 3T Funda fork. So there are other variables. The two PRs came on courses that had quite a bit of rough pavement where running 100 psi was quite a comfortable change from what I've normally done. As others have pointed out when I've talked about this in other threads ... maybe it was just running a more appropriate PSI. Maybe it was the fork. Maybe it was a combination of all the new elements. Whatever it was, the new HED wheels have been part of some really nice results I've just had. I'm not missing my old race wheels at all and most people would consider my old race wheels to have been among the very very best.

One more anecdotal thing. Search on Hed Jet C2 and read all the posts you can find where people talk about having ridden it and raced on it. I recall reading one post where there was a complaint about build quality (a concern I don't share), but I can't recall a negative comment from anyone who has actually ridden it and raced it.

I can do anecdotal and experienctial. Just don't confuse me with data and "facts." Too many times, the data has flaws and the facts, over time, turn out not to be facts.

Thanks man. I was actually asking for evidence that was NOT anecdotal but that is cool. I've read your posts before and I haven't heard a bad thing from anyone here on the new C2's or their new disc. The reason I said not anecdotal is that I think human nature tends to influence our judgement when we get anything new and supposedly better. We need to justify that purchase to ourselves. Not that I doubt your experience with their ride quality especially since it kind of makes common sense that the wider tire with less inflation would be more comfortable. I'm just wondering if there is anyway to quantify it scientifically.

This is only the first day of my taper and I'm already losing it. The next 10 days are going to be rough. ;-)

Ha. I here you. I'm curious if you have done any big hills with the C2 90 in windy conditions (I guess this is more of a question about deep rimmed front wheels and not so much about the C2 90) for my races. It was my first experience with a deep front wheel. I was on completely flat courses on both rides so far with very little wind. A few gust caught my attention but again it was minor wind on a flat course. I was thinking that going 35+ mph on a downhill with a crosswind might be tricky. Or when you are going that fast does the crosswind no effect you much?

I do the TT series at the Lowes motor speedway and the final night this year there was a pretty stiff crosswind coming down the back stretch (which is slightly downhill and usually a spot where it's easy for me to be going 31-32 mph). There's a concrete barrier along that stretch and there's one place where it breaks for an access road. Passing that break on each lap was VERY interesting because the wind was coming through there like a wind tunnel. It caught me off guard the first time around and was unnerving. Once I knew to expect it, I had no problems. That was a very windy night overall and, with the oval track and all the breaks between grandstands, it could come at you from just about any direction. I didn't find the 90 to be any more or less difficult than other front wheels I've raced in similar conditions. It takes a little getting used to, but you just have to remember that speed is your friend.

Cool. I'm pretty sold on the deep front after trying the FP 80. I had the fastest bike split in my group for the first time ever today. It was a smaller race and thus a smaller group but my avg mph was almost 2 mph faster than any other race I've done in the last few months. Now part of that is just being stronger and fresher. Bu my last race was 2 weeks ago so I'm probably not that much stronger tho I'm definitely fresher. Plus this course was flat and that helped me a lot. But I would still guess that the deep fron added close to another mph for me. It sure felt fast and feeling fast is fun.

Here is a link to the thread and test I was thinking of.
http://biketechreview.com/...lit=rim+width#p21891

On the face of it, it shows the tires mounted to a C2 to have a slightly lower crr than a narrower rim, but the spread is about what the estimate of repeatability is.

But, like others have said, it doesnt take into account the comfort factor.

I thought that tire in combination with the C2 rim was supposed to create a more aero combination. The traditional combo of the two creates the"lightbulb" effect with a tire where the sidewalls are usually wider than the rim, but on the C2 the tire sidewalls end up transitioning to the rim more smoothly.

Maybe that transition only has to do with sidewall flex and rolling resistance. But I thought there was a positive aerodynamic effect to this as well? Maybe Andy from Hed or someone else in the know can speak to this.

Personally, I'm looking into it more from the comfort perspective. If over the course of the ride, it's less jarring to the body and lets you stay in the aero position for longer, that's the biggest plus there could be.

Yeah, I think it is a combination of the factors.

I emailed HED and was told that on the old, narrow Jet, than a 19/20mm tire is more aero than a 23mm tire, but that a 23mm tire will be faster for athletes that aren't super light due to rolling resistance.

the c2 rims allow you to get that better rolling resistance and as much, or close, aeroness.

---

---

Kat Hunter reports on the San Dimas Stage Race from inside the GC winning team
Aeroweenie.com -Compendium of Aero Data and Knowledge
Freelance sports & outdoors writer Kathryn Hunter

I thought that tire in combination with the C2 rim was supposed to create a more aero combination. The traditional combo of the two creates the"lightbulb" effect with a tire where the sidewalls are usually wider than the rim, but on the C2 the tire sidewalls end up transitioning to the rim more smoothly.

Now that you mention it, I do recall reading/hearing that before. I guess I mentally discounted that after the discussion I had with HED when I bought the wheels. First, they told me to run 700x23 tires on the C2. But the Jet Disc I bought was not C2. I asked them if I should run a 700x20 on that for best aerodynamics and they said it wouldn't really make any difference. Then, when I mounted a 700x23 Pro Race 3 on the front C2, it still had a bit of the lightbulb thing going on. So I guess I have a question about how sincerely they hold to the their belief in the tire/rim interface thing. I've since mounted a 700x21 RXL Pro. I haven't ridden/raced it yet, but it looks pretty awesome ... a straight edge touching the side of the tire rests dead flat on the braking surface. Don't know if this is the way to go. If it compromises the comfort benefit I had with the 700x23s without a discernable speed benefit, then I'll go back. Of course, the 700x21 RXL Pro on the 19mm wide Jet Disc rim looks like a much better match.

I'm not sure non-anecdotal evidence is possible? I've never seen an objective measure of comfort. Maybe the shock delivered through the seat post could be measure somehow on a bumpy roller, but that's not the same as "comfort."

My anecdotal evidence is that C2's inflated to 90 are extremely comfortable and cushy. Of course any clincher inflated to 90 is more comfortable, but the C2 claim is that the increased sidewall support and volume allow this without sacrificing rolling resistance or increasing risk of a pinch flat. I have no objective data for any of that, except to say that I've been very happy with mine, and haven't had any pinch flats.

ZIPP: Your choice of Zipps announces to the world that you're on a mission to be the best. You accept no compromises, and cost is no object. You've been training 30 hours per week all year, and you're asking that your wheels match that commitment ...

I'd say this is a pretty accurate account of my expectations when I bought my Zipps. I've bagged them for HEDs and been happier ever since. Has nothing to do with herd mentality or even budget. It has everything to do with performance/results and I've had results so far on the HEDs that were never matched on any combination of the various Zipps I've owned over the last three years. The fact that they're the equivalent of Dunkin' Donuts coffee versus Starbucks is just a nice little extra ... (that would be an extra $1,000 in my pocket).

No ditching the aero helmet here.

 
Getting dangerously close to pulling the trigger on a Jet C290 front and Jet disc. I was just speaking with Tom at Bikesports and he was saying that all the 2008 Zipp stuff is now on sale for 20-30% off. It made me think twice about the C290 but I like the idea of the wider rim. Apparently Zipp realizes the merit of this approach as their new model lineup will be copying HED in this regard. Unfortunately I still don't see the point of paying a premium for Zipp when HED offers such a good product. But if you are in the market for some Zipp's give Tom a call.