THIS WEEK IN PRO CYCLING
Sea Otter Tech Report: That's a wrap
Rather than sitting on their hands after a couple of years of furious product development, SRAM engineers have been hard at work coming up with more new stuff for road, mountain and triathlon bikes.
Avid Elixir
Paul Kantor and his team at Avid seem to have come up with something completely unique inside the master cylinder of the new Elixir disc brake. And he was improving on a pretty good and successful system, namely the Juicy and Code, which have won a lot of downhill races under the likes of current world champion Sam Hill and Steve Peat, to name just a few.
“I loved the Code; I didn’t think it could be improved on until I tried the Elixir!” said Hill. Peat added, “It’s slightly less powerful than the Code, but it has better modulation and plenty of power, so I can go faster with it.”
How does it get better “deep stroke modulation” (which Kantor says “is fun to say”)? A disc brake master cylinder, be it for a bike, a car, or a motorcycle, always has a piston running down a cylindrical bore — that’s why it’s called a cylinder. A reservoir of fluid is located above the cylinder, and small metering holes allow fluid to flow by gravity down through the holes and into the cylinder ahead of the piston. Once the lever or pedal is depressed, the master-cylinder piston moves past the metering holes and seals off the system, building pressure and pushing the slave-cylinder pistons.
However, since the fit of the piston’s seal inside of the master cylinder bore must be so tight, there is friction opposing the piston from the instant of initial lever pull, and the seal is constantly being worn by sliding past the edges of the metering holes. The former results in less precise lever feel, since overcoming friction detracts from the sensitivity it offers the fingers. The latter results in higher wear rate, decreased service life and reduced power as the seal wears.
Kantor’s innovation, which SRAM has patented beyond merely the bike industry, as it appears that it has never been used in any motor-powered application, is called “Taberbore Technology.” As the name suggests, the bore of the master cylinder (no longer an accurate moniker) is not cylindrical, it is tapered, at least at the beginning of its bore. There are also no metering holes letting fluid into the cylinder; fluid from the integrated reservoir is free to surround the piston from all sides until the lever is pulled beyond the point where the pads contact the rotor.
As the piston moves inward, instead of encountering friction along the cylinder walls as it approaches the metering holes before it can build any pressure, the piston is free to move through the conically tapered section with very low friction, as the walls are not contacting the piston seal. Instead of passing holes (which are no longer needed, since fluid is free to fill in front of the piston without them) and then building pressure, it builds pressure as soon as it passes the conical section and enters the cylindrical section, where the piston seal now fits snugly. This, combined with a new lever pivot location, results in more controllable initial power, since a lighter touch is required, making modulation is easier.
“It’s super easy to make a powerful brake,” says Kantor. “The black art is making it ridable.”
The Elixir R has more power than the Juicy, thanks to bigger pistons – almost as big as those of the Code — and a stiffer two-piece caliper. Nonetheless, the brake is 20 grams lighter than the Juicy 7. A big knurled dial allows easy tool-free reach adjustment while riding, and pad replacement is far easier, now that the pads load from the top.
RockShox Reba and Revelation
The Reba has gained some travel while becoming a bit stiffer, staying a bit smoother longer, and remaining as light (in 26-inch) or becoming lighter (in 29-inch).
Where the Reba used to top out at 100mm of travel, which the SID has moved up to, the 2009 Reba stops at 120mm. The weight savings come in with the “Power Bulges” stiffening the area around the bushings in the middle of the lower legs, hollow bottoms of the lower legs, a hollow crown, post-mount brake tabs, and a new superlight Maxle quick-release 20mm through-axle.
The new Maxle is a full 50 grams lighter than its predecessor, thanks to an aluminum skewer, thinner body and cutaway lever, yet has a more ergonomic feel to the lever with nearly the same stiffness. The 120mm 29er models are only available with the new Maxle Lite, as it is so much stiffer than a standard 9mm axle with quick-release system that RockShox will only sell such a long fork for such a big wheel that way. But the new Reba 29 at 120mm and with the 20mm Maxle Lite is the same weight (about 4 pounds) as the current Reba 29 with 80-100mm of travel and a QR. Travel is still adjustable with a replaceable spacer system.
In trying to more closely mimic the performance of a coil spring with a lightweight air spring, RockShox has improved both the main spring seals and the negative spring system. To move toward the low breakaway friction of a heavier coil spring without its weight, RockShox placed the same type of foam wipers adjacent the air seals on the pistons as it has done on the tops of the outer legs. As on the outer legs, the foam ring stays saturated with oil and keeps the piston seals lubricated better for lower friction. To more closely approximate the linear spring rate of a coil spring, RockShox has added through holes under the negative-spring piston and has allowed it to float. These features prevent the negative spring from building back pressure behind it as the fork moves up and down and allow it to maintain a more constant pressure.
The Revelation keeps the same lower legs, but its travel will go up to 140mm. It also is available with the Maxle Lite 20X110mm QR axle. Disc mounts continue to be International Standard.
Hollow cranks and BSS
Truvativ is bringing its OCT (Open-Core Technology) hollow, 3D-forged crankarms to cross-country, trail and all-mountain cranks. OCT has been available in the Holzfeller downhill cranks and on the road in SRAM Rival). This cuts weight, increases stiffness and strength and maintains the GXP external bearing standard. The new gray matte anodized finish reveals the details of the profiling in the chainrings. For bling, Greg Herbold got a purple mirror-anodized pair with green chainrings and wore the left one around his neck on a gold chain.
In the BSS (bars, stems, seatpost) category, new Noir carbon bars match Noir carbon cranks and have steel mesh under the clamp. The BooBar (named for BlackBox product manager Jeremy Boobar) downhill bar answers rider requests for more length and at 780mm is Truvativ’s longest bar ever. The Holzfeller gets a flat-bar option, and the Hussefelt bar now comes in an optional white powder coat. Hozfeller and Hussefelt stems and pedals also get new colors.
Garmin
The Edge 705 GPS bike computer not only improves on the Edge 305 with a bigger screen and color, but it also offers full-color base maps with the roads numbered. It accepts microSD memory cards, or, better yet, it can communicate wirelessly with another 705 and share route maps.
Pedro’s
Pedro’s offered free bike-washing stations supplied with biodegradable Green Fizz cleaner. The combination of an environmentally friendly formulation, high dilution and (probably) a lack of life in the Laguna Seca ponds prevented dead fish from floating up despite hundreds of riders washing their bikes nearby.
Calfee
Craig Calfee has taken bamboo technology yet another step with a full bamboo tandem wrapped at the joints with hemp fiber. Calfee is training framebuilders in Ghana to build heavy-duty transport bikes using bamboo.
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