A Square Peg in a Round Hole

A few weeks ago, we posted a drawing on our Facebook page of a new carbon rim we were about to begin testing. It's 38mm deep, but instead of the 21mm width of our current RFSCs, it's wider at 23mm - same as our FSW 23s. It's from the same supplier who makes all our RFSW and RFSC carbon rims, so we had no reservations about the quality. Really, we just wanted to get them on a scale, build them up and begin racing them a bit to get a sense of their feel.

The first of those three steps though proved to be a fatass stumbling block. We knew the wider rims would be heavier - how could they not be? But we were expecting maybe 20g of extra weight per rim, which is easily justified by the added width. Yeah you'd have a slightly heavier wheel, but they'd still come in at 410g per rim, which is incredibly light given the 38s' stiffness (increased with the added width), and still builds up into a wheelset a shade over 1400g. 20g extra per rim is easily justified by the added stiffness and road feel from wider rims. It's a no-brainer, even for guys like me and Dave, who deliberate incessantly over the product portfolio.

Only when I got them on the scale they weren't 20g heavier. They were 80g heavier. Per rim. They came in at 470g. I realize that's still lighter than the 500g Zipp 303 Firecrest Clinchers, but it's 80g of rotating weight heavier than our current 38s - all for an extra 2mm of width. Dave and I reeled, steadied ourselves, then huddled up. Here's the gist of what we concluded:

  • 470g is a lot of weight for a rim that is not an aero depth. Lots of brands will call rims between 27mm and 45mm "semi-aero". That's like being semi-pregnant, and Dave throws the BS flag on it. At 38mm deep, we don't claim that our RFSC rims are aero, semi-aero, mock-aero or aeroesque. The advantage of the extra depth is principally that it builds into a stiffer rim that requires fewer spokes than alloy, and is incredibly light. Add an extra 80g and you've still got a stiff rim with fewer spokes, but you've given up the light weight. 
  • So what if Zipp 303s are still heavier? My hat is off to Zipp. They have done a remarkable turn of work convincing people that whatever shape they're marketing this year is the most slippery rim design ever possible, and even at shallow depths and slow speeds, the aero benefits nevertheless remain readily apparent. Their story is aero aero aero, which makes it easy to obscure the actual rim weight (which they don't publish on their site, though Wheelbuilder does on theirs). Because of their aero focus, Zipp doesn't have to sell based on weight. The racers who are our customers, however, obsess over weight. I can't fault them - as a racer myself who is particularly parsimonious with his power, weight is a principal consideration of all my product decisions as well.
  • So this is how fudge is made, huh? Our current RFSC 38s weigh in around 1370g almost without fail. With 160g more of rim weight, we'd be at 1530g, which is heavier than our RFSC 58s. One way to get that weight down would be to slice out some spokes, but you'll have more luck trying to convince Dave to just sit in for 95% of the race and save himself for the sprint. The only other way to bring the published weight down is to fudge it. It's certainly not an uncommon practice, particularly when you want to hit a psychological target with weight, like 1498g, when you're really 1527g. Publishing a wheelset weight that is under-represented by 20g - 50g certainly boosts sales. Say it's plus or minus 1%-3% and maybe everyone won't notice that they're inthe +3% category, right? We know our customers put their wheels on the scale as soon as they get them, and we know they email us the numbers. We have no interest in selling a wheel that disappoints a customer as soon as he takes it out of the box. Weights vary, but our published weight is our average weight for a wheelset, not the actual weight of the lightest rim in the batch paired with the lightest hub, with spokes cut down by 1mm each to shave a couple more grams.
  • How much wider is 2mm? Our current RFSC 38s (and 50s, and 58s, and 85s) are 21mm wide. That's already 2mm wider than the 19mm average width of road rims. So whatever benefits 23s afford, we're already halfway there with our RFSCs. 80g for 4mm of extra width would be a tougher decision. But our RFSCs already ride awesome. 2mm more width would be nice to have, but it's at a trade off we can't countenance.
  • I'd race FSW 23s over porked-out 38s. Dave and I both feel this way and ultimately that's what it came down to. Less rotating weight simply feels faster. You jump more quickly and feel more nimble, which ultimately translates into increased confidence when it matters. Would 1480g FSW 23s actually be faster than 1530g RFSC 38s? You got me. But in my mind they would feel faster, and what happens in your brain on game day usually has a bigger impact on your race than what happens in your legs.
  • It's not about how much we sell, but what best meets our market's needs. The appeal of 23mm wide rims is so strong right now, we'd probably hit the jackpot with wider RFSC 38s, even at 160g heavier than our current 38s. But we don't think they're a good solution for racers, and we don't think racers would be the people who would buy them. We're a little different from some other brands that focus on moving as many units as possible. Instead, we create a product line that targets a pretty narrow niche (though at 60,000 USAC licenses per year, it's not that narrow), and work to find more people who belong to that niche. We want to be the best solution for racers, which requires us to be single-minded of purpose. 

We were hoping to introduce the 23mm wide RFSC 38s with the current (May 7th) pre-order, but for all these reasons we're not going to go with them. We just don't see them filling a need for our customers because the compromise they require isn't justified by the benefits the new design affords. They're a square peg. If they were lighter (or if they get lighter - these were some of the first demos made available by our supplier) we'll absolutely reconsider.

And it's not like there's anything wrong with our RFSC 38s just the way they are. We still think they're plenty really friggin sweet. 

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so your marketing spin is try to call out somebody else's marketing spin as hocus pocus and base your finding purely on opinion and not any type of factual data, whereas zipp does. Oh and btw, under specs on all wheels including the 303 is their weight, first thing you see in BOLD RED LETTERS. I'd rather spend the extra money for the confidence in their r&d department than how YOU feel a wheel performs.


How much would it weigh if they were tubulars ? What if you still use the 21mm wide 38's but have a u shape at the spoke side instead of a pointy shape? That might mean less weight right? But does the U shape really help out with the cross winds? I mean it's only 38 right?But I'm really interested in the 38tubs….


Mavic's Reflex, although not in any way aero, is 21mm wide, and an awesome rim all around. Good tire(tubular)/rim transition, very laterally strong, comfortable and stable. Your RFSC rims sound excellent as they are. A bit of the 'best of both worlds' at 21mm I think.

Jim Guy

Nice inside scoop…and I'm with you, I'd rather use my FSW23s over a heavier pair of 38s…


Fred, your reading comprehension sucks worse than my time trialing, and I've been known to give away 2 minutes over 25K (I totally coulda won with 808s though). One of the reasons we got started was to combat a lot of misconceptions within the cycling industry, as spurious claims and faux features are principally responsible for what we believe is an unwarranted inflation in prices. We hate inaccuracies on cycling websites, and now your misread has gone and put a bunch of them right here on our own. Nick, I appreciate you correcting one of Fred's mis-reads, and for that I'm sending you a November water bottle. Send me your address here:http://www.novemberbicycles.com/contact-us/If anyone else wants to point out where else Fred's interpretation or logic is flawed, I've got more bottles to give away. Cases of them, in fact.

Mike May

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