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All-New Diamondback Serios Triathlon Bike Proves Thinner Isn’t Always Faster

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2015-diamondback-serios-tt-triathlon-bike

Teased just before all the top triathletes headed to Kona for Ironman World Championships, the new Diamondback Serios slipped some very interesting frame shapes in and out of focus with a short video. Now, we’ve got a very in-focus look at one of the sharpest looking tri bikes in recent memory and some Q&A with DB’s product manager to make sense of it all.

The story is they started with thinner and thinner tubes, thinking a more waif-like structure would slice through the air quicker and easier. What they found was some cross sections could be wider and provide better aerodynamics. And wider was better when it came to the range of riders it could fit, too. The project is a collaboration between Diamondback, HED Cycling and Kevin Quan Studios. The result is a wild looking TT/Triathlon bike that’s UCI legal and fits pros and age groupers both short and tall.

Here’s how they did it…

2015-diamondback-serios-tt-triathlon-bike

Each of the partners brought their expertise to the table, which included Optum Pro Cycling Team rider feedback on the bike’s handling. HED’s engineers talked aerodynamics and bike fit, which is why you’ll see their wheels and cockpit used throughout the range. Quan’s design experience translated that data into a frame that not only looks good, but works from riders as short as 5’4″ and as tall as 6’5″, which happens to be the spread of Optum’s team riders.

2015-diamondback-serios-tt-triathlon-bike

As predicted, the stem and steerer design is heavily integrated into the frame, delivering smooth airflow across the front and all the through the frame. Senior Product Manager Michaal Brown explains the design:

“The headtube is the biggest beneficiary of increasing width. Making the headtube wider allows for the integrated stem to best package the shift and brake cables. There is no aerodynamic penalty because we then taper this wider headtube along the total length of the top tube. In effect, the top tube is simply the tail end of a very long headtube airfoil.

“Additionally, the wider headtube also allows us to package a tapered fork (1.375″ lower bearing) for increased front-end stiffness. This in turn means sharper handling and better stability on descents.”

The integrated design doesn’t sacrifice adjustability. The spacers are designed with the same air foil shape as the head tube and provide a smooth transition for any air passing over them. They work in the same way as any headset spacer, but they’re keyed and also function as the headset bearing cover. Bikes will ship with a set of 4 spacers (2x10mm and 2x15mm) and a steerer tube long enough to accommodate the full spacer stack. Once your properly fit to the bike, cut the steerer to the right length. Bikes will ship with a size-appropriate stem, but three lengths (95/105/115 mm) will be available for sale aftermarket.

2015-diamondback-serios-tt-triathlon-bike

But there’s more to the story of wider tubes:

“The wider sections are intrinsically more aerodynamic,” says Brown. “The drawback to reducing bicycle tubes to flat and narrow sections is that they will result in flow separation and higher drag in even the slightest of cross winds.

“In aerodynamics, there is a classic case called a Flat Plate scenario. Flat plates are not as aerodynamic as tear drop shaped airfoils in cross winds. So the question becomes when do bicycle sections begin to behave as flat plates and not airfoils? Diamondback has invested a lot of time and money into answering that question.”

For a bike that seemingly has so much aero tech designed into it, a fully exposed front brake seems out of place, but that, too, was intentional.

“There have been questions regarding the exposed front brake,” explains Brown. “We came to this decision after much internal debate. From past wind tunnel testing we have observed that exposed brakes contribute no additional drag than integrated brakes or even a fork with no brakes at all! It was Steve Hed that gave us the final piece of the puzzle when he observed that flow around the wheel at the fork crown was in fact reversed due to the direction of spin. We concluded that turbulence caused by the spinning front wheel in effect masks the presence of an exposed front brake.
With that being the case, we specified a Shimano direct mount brake which had demonstrated superior performance to both conventional center mount brakes and integrated v-brake alternatives.”

Regardless of which spec level you choose, you’re getting all the same design, tech and layup – all three share the same exact frameset.

Diamondback.com

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17 Comments
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fourthandvine
fourthandvine
8 years ago

WHY. SO. SERIOS.

Sorry.

wheelz
wheelz
8 years ago

Looks pretty darn nice.

Ham-planet
Ham-planet
8 years ago

Girlfriend in a coma, I know, I know…

Neilthemeal
Neilthemeal
8 years ago

I think this bike is awesome. The wider is faster thing is a little misleading if you look at the data, wider is faster in a big crosswind. If you look at data from mavic and trek on yaw, then 15 degrees is not necessarily the best area of optimization but the serios is still competitive at low yaw and the price and specs are really good. Not to mention the lack of unnecessary integration is nice if you do your own wrenching. I still don’t know why I like this bike so much but I do.

One final thought is it would be nice if their data had a lot more detail. It’s hard to believe its accuracy without a little more detail.

Pablo
Pablo
8 years ago

“Here’s how they did it…”

They gave their money to Bicycling & such reviewers, got nice reviews, people bought the bikes and now they can afford to try to be fancy.

Bikes look cool.

Terry
Terry
8 years ago

looks nice. i like the paint job in the first pic.

greg
greg
8 years ago

A solid effort by a company that doesn’t exactly come to mind when one mentions “triathlon”. Maybe times will change a little.

Nathan
Nathan
8 years ago

I don’t get companies that make garbage for department stores then try to make high end bikes under the same name. Dorel gets away with it by keeping the names separate. Raleigh is reasonably reputable, Diamondback is garbage. Why mix them? My crystal ball says this is a waste of resources.

silverlining
silverlining
8 years ago

The tease before Kona seems to be the most obvious answer as to why DB made a tri bike. Tri folks are a different kind of bike snob. They buy $10k bikes, but the name on it isnt as important as the hype that claims X minutes faster due to X shape. Quintana Roo and Guru to name just two brands a roadie might sneer at but tri folks appreciate. Also, given how so many road bikes are just carbon copies from each other, a new tri bike would set them apart. How they dragged HED in to it though is a head scratcher.

mudrock
mudrock
8 years ago

I guess the answer to some of the above snark, is that Diamondback will cover all segments of the market and not care what .1% of the buying public has to say about it. They’ve designed some nice bikes. And the payback for Steve Hed is obvious.

wheelz
wheelz
8 years ago

Diamondback has already begun restoring their name by sponsoring some professional and top-end amateur athletes. Where I live, the best amateur road team has Diamondback frames and the feedback has been that they are great bike. As long as they continue to produce innovative and well-executed products, word-of-mouth will help restore their name. I think this TT bike _looks_ killer and I would love to demo one personally. I’ve never ridden any Diamondback before, but if their were a dealer in town, this would change.

JBikes
JBikes
8 years ago

I think its kinda funny to see all these companies aero optimize the heck out of their bikes, but systematically eliminate 650c wheels from existence.

Slow Joe Crow
Slow Joe Crow
8 years ago

Another consideration for DB getting into the TT/Tri market is to give their road teams a sponsor correct TT bike. This year the DB sponsored pros were using relabeled LaPierre frames since they are also part of Acell along with Raleigh, Redline, Ghost and Koga.
Which leads to to the distinct possibility that brand snobs will be able to buy the same frame under a different nameplate in the future since that spreads out the development costs.

alistair
alistair
8 years ago

@wheelz the best amateur road team in your town is on diamond backs and theres not a dealer there? thats odd. go to performance bike.

Dude
Dude
8 years ago

Argh misleading aerodynamic talk! Thinner profiles are faster if you’re comparing the same shapes. Flat plate vs teardrop is a red herring. I’d expect interactions such as tire and brake with the frame, and also stiffness/weight ratios to put a lower bound on thinness.

wheel-addict
wheel-addict
8 years ago

@alistair, I agree that it is odd and a bit of a waste. Still, it was seeing the bikes in person and hearing good feedback from people riding them that has got me interested in Diamondback again.

fib
fib
8 years ago

Wow. “Something that could be the biggest upset in the cycling history”… Sorry DiamondBack, but such bold – and stupid – statement isn’t going to sell more bikes. It’s just laughable: change your PR team!

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