Fear of Tigers – Please Don’t Leave

http://www.deezer.com/listen-6464427 Voilà qui donne une énergie incroyable pour affronter une nouvelle journée…avec plein d’images de ride en tête.

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Proto Fox 40

Proto Fox 40
l’info vtt du jour (29 May 2012) : Proto Fox 40…

Inauguration de l’Apple Store des Quatre Temps MàJ

Ne pas craquer!

Inauguration de l’Apple Store des Quatre Temps [MàJ]
C’est ce matin qu’ouvre le 11e Apple Store de France, dans le grand centre commercial des Quatre Temps à la Défense. L’inauguration est à 9h et les premiers clients et curieux sont déjà là, ainsi que les 1000 tee-shirts rangés sous les tables et sans oublier le café offert par les voisins.

Schwalbe 2013 mountain bike

Schwalbe 2013 mountain bike products

Schwalbe restake their claim in the 650B market

The blue graphics denote a tyre in schwalbe's development programme, this was a 650b hans dampf:

A 650b Schwalbe Hans Dampf

Danny Hart’s World Championship-winning tyre supplier have also recoded their product designations. For 2013, Active (A) Line tyres will all offer at least 50tpi and Kevlar guards. Performance (P) Line MTB tyres will all have dual rubber compounds. Evolution (E) Line rubber will continue to offer the highest grade materials and latest technology. Tyre walls will show square icon boxes for each feature, with the tyre line letter first and the diameter shown in bold characters elsewhere.

Almost all of the products in Schwalbe’s MTB range will be available in 29in. The brand’s own rolling resistance tests, conducted over different terrains and obstacles, showed the 29ers to roll 5-6 percent faster. They also topped the table for feelings of safety, ride experience and security for the 50 riders involved, compared to 26in wheels.

Schwalbe offered 650B tyres four years ago and removed them from the catalogue last year, after limited uptake. They’re now back and available in Racing Ralph, Rocket Ron, Nobby Nic, Hans Dampf and Rapid Rob patterns and several widths.

The Rocket Ron has undergone some changes, with tougher shoulder blocks to limit tyre squirm and a reconfigured centre block that’s claimed to reduce rolling resistance by about 15 percent. Each tread block has a siped surface to increase grip, and a new sidewall finish improves sealing to make it tubeless-ready.

The Hans Dampf enduro tyre has evolved, with a Super Gravity (SG) version now on offer that claims to be as strong as a downhill tyre but as light as a freeride. It has a Snake Skin sidewall to resist cuts. Already ridden in prototype form in the World Cup downhills this season, we were assured that its weight will be 995g. Compared to a 1200-1300g downhill tyre with six carcass layers, the SG tyre has fewer layers. The sidewall stiffness fits between that of downhill and enduro tyres but with a more flexible tread than downhill rubber would usually offer.

A new rubber compound also sits between those used for downhill and cross-country to offer the proposed performance. The reinforced Kevlar bead and Snake Skin protection should help resilience, and in tubeless configuration could save about 800g over a downhill tyre and tube setup. That just happens to be where it can make the most difference

1×11 > 2×10 > 3×9?

SRAM XX1 prototype spotted – this one goes to 11

We’d long heard rumblings of a new 11-speed mountain bike group coming from SRAM. We expected it to be an updated XX with a wider range that more closely replicated a conventional triple. Instead, SRAM have developed a progressive, dedicated, single-ring 11-speed group called XX1. The company hope it will change mainstream thinking in terms of mountain bike drivetrains.

We happened to score an in-depth look at the prototype during our recent visit to SRAM’s European headquarters, where we got a lengthy sit-down with drivetrain product manager Chris Hilton. We also got to pedal the bits around a little, too.

What is the XX1?

SRAM aren’t pitching XX1 as having 11 speeds. Instead, they’re describing it as a 1x drivetrain that just happens to have 11 cogs out back. The heart of the XX1 concept is its ultra-wide, 10-42T cassette, which provides a generous 420 percent range. That still falls short of the XX’s rough 470 percent but it’s a big improvement over current 1×10 drivetrains that many riders already run. In essence, the XX1 cassette adds a gear on either end of a current XX cassette while retaining reasonable jumps in between.

“We’re not trying to start an 11-speed war,” Hilton says. “A 1×11 war? Fine, but a 2×11 war isn’t beneficial to anybody.”

SRAM also don’t intend for the XX1 to replace current 2×10 groups. Instead, they’re aiming it at trail and enduro riders who are often already strong enough to power a single-ring drivetrain. The target group often also place a major emphasis on chain retention and impact protection with dedicated guides and bashguards.

Nonetheless, SRAM are fully expecting a smaller faction of forward-thinking cross-country riders to jump on board as well. As well as being simpler and more secure than the XX, the XX1 is also lighter. Target production groups are 200-300g relative to the ultra-light XX.

“Almost all of that is from omission, not from anything getting lighter,” Hilton tells BikeRadar. So there shouldn’t be any drop in overall durability, either.

Final pricing is still to be determined but SRAM plan to launch the XX1 later this summer.

New cassette, new freehub body

The XX1 cassette construction is very similar to that of XX, mostly machined from a single block of steel to form a hollow, domed structure. That dome is then capped with an aluminum innermost cog – in this case, one that’s much more dished than the one on XX. This also transfers all the drive torque to the splined freehub body. Instead of having the smallest cog as a separate bit, XX1’s 10-tooth cog is now integrated into the rest of the steel structure.

Squeezing on a 10-tooth cog required some doing, as it’s too small in diameter to fit on a conventional freehub body. So, SRAM created a new ‘XD’ driver body that’s essentially a slight modification of what’s currently in use. The end where a conventional lockring would normally thread into is lopped off. And almost all the splines on the outside of the body are shaved smooth to leave a mostly bare cylinder.

A Delrin-lined aluminum locking ‘tube’ replaces the conventional lockring. The ‘tube’ snaps into the inside of the 10-tooth cog but is otherwise free to rotate. Threads at the inner edge then match up to new threads added just outboard of the remaining freehub body splines. The Delrin lining is sized to provide a light press-fit on the freehub cylinder. When it’s all secured, the locking tube keeps everything firmly concentric on the freehub body, with no chance of cogs digging into its surface. It’s not very different to how a non-driveside SRAM GXP crank arm attaches to a bottom bracket spindle.

Because all the freehub body modifications are restricted to the exterior, an XD body can be adapted to current hub designs with no changes to things like axles, bearings and spoke flange spacings.

The xx1 cassette fits onto a modified xd cassette body:

The XX1 cassette fits onto a modified XD cassette body

For now, wheels will be available from SRAM and DT Swiss only. Hub spacing will remain unchanged at 135mm or 142mm. Licenses to other makes are under discussion, but given the prevalence of DT Swiss drivers in other companies’ wheels that should open things up to the likes of Specialized, Reynolds, Enve Composites right away.

XX1’s 11-speed cog spacing will be unique to the group, however, and isn’t shared with 11-speed offerings from Shimano (more on that soon) or Campagnolo. Of course, there’s a dedicated 11-speed chain as well, with a slightly narrower external width. Inner plate spacing and roller width are unchanged from SRAM’s 10-speed chains, though. So wear supposedly isn’t adversely affected.

Straight P derailleurs

The XX1’s rear derailleur will signal a radical departure from current designs. With a conventional slant parallelogram the derailleur body simultaneously moves the cage in and out as well as up and down. But the XX1 will use a so-called “straight P” layout where the body only moves along the horizontal plane. It’s an idea Hilton admits has been floating around within SRAM for the past eight years but is only now seeing the light of day with the rise of 1x drivetrains.

Hilton acknowledges that a straight parallelogram is counterintuitive. One would assume that the derailleur body should follow the contours of the cassette, but the XX1 cassette’s extreme gear range and tighter cog spacing necessitated a change in thinking.

“Originally, the first prototype of this was built for a downhill bike,” Hilton says. “We built it because when bikes hit bumps, the derailleur absorbs the shock of that chain. So you hit a bump today and you’ve got your chain mass and your derailleur mass. It can actually activate the parallelogram and cause ghost shifting. If you add a clutch to that and you’ve really significantly stopped that force, you’ve actually added to the potential for ghost shifting. We’ve compensated for that [in current Type 2 rear derailleurs] by not decreasing our spring tension in derailleurs.”

Because XX1 doesn’t rely on a slant parallelogram to control chain gap, the upper pulley is now hugely offset from the lower derailleur body knuckle. As the chain shifts across the range, more or less chain is wrapped around the cassette, pulling the cage fore and aft and the upper pulley up and down.

XX1 will only be offered with a single 10-42T cassette ratio, so that upper pulley pivot offset could be precisely calculated to keep chain gap consistent across the entire range.

“The chain gap is exactly the same in every single cog no matter what cog you’re in, even if you were to change the cassette, because it’s driven by the amount of free chain length,” explains Hilton.

The XX1’s “straight P” design also means it will only work with a single-ring crank. Likewise, suspension designs with lots of chainstay growth could be problematic.

Other details include an integrated cable pulley at the rear of the derailleur, just like on Avid’s long-defunct Rollamajig. This decreases cable friction. We expect production units to be built with cold-forged parallelogram plates and a carbon-fiber pulley cage.

The 1×11 concept doesn’t require a huge re-engineering of shifters. Therefore, XX1 models will essentially be the same as current trigger and Grip Shift offerings, albeit with different badging, an extra click and specific internal spacing.

No chainguide?

XX1 was conceived as a single-ring drivetrain, allowing engineers to rethink the chainrings as well. Conventional 2x or 3x chainrings are designed with elaborately shaped teeth to improve shift performance. But this also affects ability to retain the chain on bumpy terrain.

“As we make chainrings shift faster and smoother, we’re taking material away, making them more expensive, limiting their lifespan and potentially affecting chain retention capability,” says Hilton. “There’s no question that making a chain shift makes a chain fall off.”

As a result, XX1’s chainring teeth are unusually tall and quite squared-off, similar to those found on dedicated singlespeed rings. However, they’re also built with alternating tooth thicknesses that are syncronized with the gaps in the chain – slightly narrower to fit between inner chain plates, and wider to take advantage of the extra space between outer chain plates.

Combined with XX1’s improved chainline, Hilton claims this improves chain retention to the point that you won’t need any sort of guide in most applications, while also slowing down wear and reducing drivetrain noise. Hilton admits that aggressive trail and enduro riders might still choose to run some sort of minimal upper guide, if only for peace of mind.

“I like to say that chain retention is sort of like birth control – there are various levels of safety,” he quipped. “You could choose to use a full-on X0 DH guide with bash protection and a lower roller in addition to this whole system. But that would be like abstinence.

The xx1 drivetrain fits in well with the 'new school' of trail bike kit, which includes wide bars and short stems :

The XX1 drivetrain fits in well with the ‘new school’ of trail bike kit, which includes wide bars and short stems

The synchronized design of the chainring teeth will limit the XX1’s chainring choices to even numbers. But the overall range is admirably broad – all the way from 28-38T. That variation will require a dedicated bolt circle diameter, but the spider will be shaped so that users won’t have to remove the cranks to swap rings. The production crank will feature hollow carbon-fiber arms and be offered in both narrow and wide stance widths (we’re guessing 156mm and 166mm, as for current XX cranks).

1×11 drivetrains: the bonuses

Why go to all this trouble just to eliminate a chainring, though? Don’t current 2×10 systems already work well enough? That all depends on who you ask.

It’s true that modern two-ring drivetrains work well. But they still can’t match the security of single-ring setups, which are increasingly finding favor in the mainstream marketplace, especially with more aggressive riders. If you need proof of that, just note the explosion of two-ring chainguide models in recent years.

Moreover, single-ring drivetrains are simpler and lighter, as well as less confusing to newer riders. Hilton doesn’t refute the idea of eventually bringing the 1×11 concept to much lower price points. And XX1’s gearing range sounds generous enough to be useful for a wide swathe of riders.

“As long as you choose your range properly, this type of system is applicable to a majority of people,” Hilton says. “It’s not intended to replace 2×10. Some people need a bigger range, and that’s fine – we still have 2×10. But if you’re Ross Schnell or various other people, this is a radically improved 1×10.”

Hilton also points to the difficulties an OEM company can face in terms of getting front derailleurs to play nicely with the huge range of rear suspension designs.

“Front derailleurs are limiting because there are so many choices,” Hilton says. “It’s limiting because of where you can move the wheel to, where the suspension pivots are placed, where the cable routing comes from – all those things are limitations to a drivetrain. Front derailleurs are one of the most expensive engineering and tooling costs on a bicycle, yet it’s the first place manufacturers go to cut money.”

So why not use a 2×11 setup? Combined with that 10-42T cassette, such a drivetrain could easily replicate the full range of a traditional triple but with the advantages of a double.

“2×11 is certainly feasible – it’s not impossible,” Hilton says, though he also adds that the cassette’s added width presents problems with chainline if more than one chainring is used. “11-speed is a by-product of wanting to make a wider-range cassette without funky steps in there. We want to sell it as a 1x drivetrain solution that just happens to have 11 gears. The eleventh gear becomes problematic because the overall spacing is now wider.”

Could the XX1 concept be further expanded with a revamped HammerSchmidt or high-performance, internally geared setup, though? Hilton doesn’t rule out that possibility but says it’s not imminent.

Either way, XX1 sounds awfully appealing on paper. And after a brief test ride inside SRAM’s Schweinfurt facility, in Germany, it certainly seems to work. We’ve been promised parts for testing in the near future so we’ll know for sure soon.

J-2

Affaires préparées. 2 jours de course pourraient se résumer à ça?

Étonnant, moi qui ai toujours besoin d’un semi-remorque pour me déplacer sur un événement. Train dans 7h, Nice dans 14h…

J-4

Voilà, le bike est prêt, dans son sac…La tension monte. Le montage dans le détail se trouve ici.

10,9Kg de pur bonheur pour le XC Longue distance