Laurie Greenland’s Trek Session 9.9 650b prototype

WHO IS LAURIE GREENLAND?

Seventeen-year-old Laurie, from Bristol, is the newest signing to the Trek World Racing factory team. Turn to p91 for the full lowdown on this rising talent.

WHY IS THIS A SUPER BIKE?

- Manufactured in-house in the USA, this full-carbon downhill bike is one of the lightest on the race circuit.

- Designed from the ground up to maximise the benefits of the mid-sized 650b wheels and give the Trek World Racing riders an edge on today’s faster World Cup tracks.

- Factory tuned Fox fork and prototype RAD rear shock complement race winning pedigree of the new frame.

WORLD’S FIRST FULL-CARBON 650B DOWNHILL BIKE

The Trek Session is arguably the fastest downhill bike of modern times, with three World Cup series wins and one World Championship title to its name. Never ones to rest on their laurels, Trek have created a new prototype for their team riders that’s not only been designed around faster rolling 650b wheels but also has a full-carbon frame that, unusually, isn’t manufactured in the Far East but is instead made in-house at their factory in Madison, Wisconsin.

Going bigger to go faster

Until as little as a year ago, downhill racing was all about 26in wheels, with only a few brands openly experimenting with 650b wheeled alloy test mules or rejigging frames to accept the larger wheel size. That’s all changed now, with all the major fork, wheel and tyre manufacturers getting on board with the new standard and bike companies proving keen to give their team riders the latest perceived performance advantage.

And the advantages of the ‘new’ wheel size are plain and simple – “650b is important for downhill bikes because it’s a faster wheel size,” says Trek’s Director of Suspension Frame Technology, Dylan Howes. “The wheels roll faster and grip better [than 26in wheels], and the difference in acceleration is so small that it’s erased by the gains in speed, rollover and traction. They also lower the BB height relative to the wheel axle, giving the rider more stability and more of that ‘in the bike’ feel, but still maintaining a good BB-to-ground height, so you don’t get the pedal strikes that can come with a very low BB height.”

In late 2013, the design team responsible for the Session line began the process of developing a 650b prototype and testing it against the 26in bike. This comparative testing was important for Trek, who were initially less than receptive to the in-between size, having long been advocates of 26 and 29in wheels for different types of rider. The data backed up the benefits of the ‘new’ size though, and as the 650b parts shortfall began to be addressed, things got serious.

Prototype bikes were handed over to the Trek World Racing riders ahead of the 2014 season, and they recognised the benefits of the bigger wheels from the offset. “I feel the biggest difference on fast, rough terrain like that at Fort William, where they allow me to carry more speed,” says factory rider Laurie Greenland. “But it’s not until you’re hitting the jumps, where you’d normally have to pedal hard to clear them, that you really notice the increased speed.”

Under the hood

The new bike isn’t just about 650b wheels though, and the frame hasn’t just been tweaked to take the new wheel size. It’s now full-carbon – previous Sessions had alloy chainstays – and the mainframe and swingarm have been redesigned from the ground up, not only to harness the advantage of the larger wheels, but also to deliver an amazing strength-to-weight ratio.

Trek have taken great care with the carbon lay-up process, seeking to maximise lateral stiffness yet build in enough vertical give that the ride doesn’t become harsh. They’ve also reduced material depth in non-stressed areas while adding extra carbon where it’s needed. This has left team bikes like Laurie’s comfortably under the 15.5kg (34lb) mark.

What also stands out about the new Session is that it’s made on American soil – unusual for any carbon bike, and a first for a carbon DH bike. Dylan says this has many advantages, not least of which is the quick turnaround times: “Making the moulds and developing the lay-ups in-house has a tremendous benefit in the amount of time it takes. We can make a frame with one lay-up, test it and go right back to the next lay-up iteration or change. This is much quicker than sending frames back and forth.”

GETTING LONGER

It’s not just the wheels that are bigger on this prototype – the chainstays are 5mm longer than on an equivalent sized 26in wheeled frame and the top tube is around 10mm longer to help improve stability at speed.

ROUGH WITH THE SMOOTH

Trek’s ABP (Active Braking Pivot) system is a rider favourite. The concentric rear axle pivot lets the bike track the ground well even under heavy braking, helping the rider to maintain traction and speed.

TWEAKED SUSPENSION

The suspension kinematics have been revised to deliver a more progressive feel while maintaining the excellent pedalling that the Session is known for.

GRAM COUNTING

Trek’s designers have increased the amount of material used in areas prone to stress and removed it where it isn’t needed to minimise weight.

MILITARY GRADE

The materials used in the carbon lay-up are controlled by the US Government due to their military grading, which means they can’t be exported.

GETTING RAD

As a factory Fox rider, Laurie’s bike is equipped with the latest RAD (Racing Application Development) rear shock and a matching custom tuned Fox 40 Float fork up front.

DEVIL’S IN THE DETAIL

Integrated into the frame during the moulding process are neat and tidy recesses for zipties to help keep the cables and brake lines from getting tangled and messing up such a great-looking frame.

CARBON FOOTPRINT

Unlike other brands experimenting with alloy 650b DH bikes, Trek decided last year that a bespoke carbon mainframe with a matching rocker link, seatstays and chainstays was the only way to go.

FRAME: Trek Session 9.9 Carbon

FORK: Fox 40 Air Kashima, 20mm thru axle, 203mm travel

REAR SHOCK: Fox VAN RC4

REAR DERAILLEUR: Shimano Saint, Shadow Plus

SHIFTERS: Shimano Saint, 10 speed

CHAINSET: Shimano Saint

CHAINRINGS: 36T

CASSETTE: Shimano Ultegra 11-25, 10 speed

CHAIN: Shimano XTR

CHAIN GUIDE: MRP G3

BRAKESET: Shimano Saint

HANDLEBARS: Bontrager Rhythm Pro Carbon Riser, 31.8mm, 15mm rise