We first spotted Trek’s prototype 650b downhill bike back in February, and Trek soon confirmed that it will make it into production. Since then, we’ve seen the Trek World Racing downhill team exclusively use the 650b models at the two opening World Cup rounds in Pietermaritzburg, South Africa and then in Cairns, Australia.
Brook MacDonald, a former Junior World Champion, is a Red Bull sponsored athlete who rides for the Trek World Racing team. So far his 2014 season hasn’t gone exactly to plan, but his sheer strength and speed ensures he’s always a threat. And, at the least, his laid-back New Zealander style on and off the bike makes him a consistent crowd favourite.
Trek’s full-floater suspension system
The carbon construction of this frame means this is one polished prototype. With it being far cheaper to produce prototypes in aluminium, it’s likely the production version won’t change much from what the team members are racing on now.
MacDonald’s mechanic, Ely Woody, told BikeRadar the 650b bike is a long way from simply being some different sized wheels in the existing 26” frame. Rather, it’s a complete redesign around the larger hoops in suspension rate, geometry and frame construction.
Just like the 26”version, the prototype Session frame features 210mm of rear wheel travel, matched with a 203mm fork on the front.
Active braking pivot places a pivot point at the rear axle, something that’s used across all Trek’s full-suspension models
Trek continues with its proven ABP DH (Active Braking Pivot), which prevents the suspension from stiffening under braking. Additionally, its ‘Full Floater’ linkage system remains, which allows the rear shock to move from both ends, leading to a more consistent shock leverage ratio and rate. This system also reduces the required movement in the shock’s bushes, helping provide greater small-bump compliance – a small difference that is crucial in the sport of downhill.
Much like Greg Minnaar’s Santa Cruz bike, which we showcased recently, MacDonald’s machine features prototype suspension front and rear in the form of Fox’s Racing Applications Development (RAD) program. The rear shock is something first seen at the 2013 World Championships and has taken the form of something that looks ready for production. A Fox titanium spring is used to reduce weight over a standard steel spring.
On the front is a seemingly stock air-sprung Fox 40 Float RC2 fork, which likely features some internal tricks and, if it’s similar to that on Minnaar’s bike, will be all about achieving ultimate small bump compliance through ultra-slick internal surfaces.
Brook MacDonald switches between pedals depending on conditions – he was clipped in at Cairns with these Crank Brothers Mallet Race DH
The shifting and braking duties are handled by Shimano’s downhill-specific Saint group. To help reduce weight, the rear cassette is a Shimano Dura-Ace 11-23 model with titanium construction. Ensuring the chain stays in place is a lightweight MRP G3 chain guide.
The prototype Bontrager Mud Team Issue
The slick mud of Cairns, Australia, had MacDonald using a new prototype tyre from Bontrager, Trek’s component and accessory brand. This Mud Team Issue model features an extremely open tread pattern and looks to blend aggressive side knobs with a lower profile centre for faster mud clearing and lower rolling resistance. We’re told the team is using Bontrager’s G5 tyre in the dry.
Interestingly, the team were using Bontrager’s trail orientated Duster rims. These offer a far lower weight than a purpose built downhill rim, with Woody explaining that “the Cairns course wasn’t too tough on rims”.
Helping MacDonald in the mud of Cairns was a SDG I-Fly Storm saddle, which features rubber tread over the surface of the saddle to stop any sliding when seated.
To see Brook MacDonald and his bike in action, check this video from Trek World Racing
Complete bike specifications
- Frame: Trek Session 9 650b
- Fork: Fox 40 Float RC2 650b, RAD
- Rear Shock: Fox RAD, Ti spring
- Headset: Cane Creek
- Stem: Funn direct-mount stem
- Handlebar: Funn Fatboy, 800mm width
- Tape: ODI Ruffian MX lock-on
- Front brake: Shimano Saint, 203mm rotor
- Rear brake: Shimano Saint, 203mm rotor
- Brake levers: Shimano Saint
- Chain Guide: MRP G3
- Rear derailleur: Shimano Saint Shadow Plus
- Shift levers: Shimano Saint
- Cassette: Shimano Dura-Ace 11-23T, 10 speed
- Chain: Shimano XTR
- Crankset: Shimano Saint, 36-38T chainring (pending on course)
- Bottom bracket: Shimano press-fit
- Pedals: Crank Brothers Mallet DH Race
- Rims: Bontrager Duster XC – 650b
- Hubs: DT Swiss 240s
- Front tyre: Bontrager Mud Team Issue 2.3” – prototype (Bontrager G5 2.35” in dry)
- Rear tyre: Bontrager Mud Team Issue 2.3” – prototype (Bontrager G5 2.35” in dry)
- Saddle: SDG I-Fly Storm
- Seatpost: SDG I-Beam Carbon
- Rider’s height: 1.69m (5ft 6in)
- Rider’s weight: 85kg (187lb)
- Saddle height from BB, c-t: 600mm
- Tip of saddle to middle of bar: 450mm
- Head tube length: 115mm
- Top tube length (effective): 520mm
- Total bicycle weight: 16.1kg (35.42lb)