Scott Bicycles has unveiled what is likely the lightest full carbon production mountain bike frame, the 2011 Scale 899.
Weighing in at a claimed maximum of 899 grams, the new bike took what they learned from their original Scale (which came in at 970g) and not only made it lighter, but refined the geometry, layout and feel of the bike, too.
First off, the geometry. The 899 has a 20mm longer top tube, a 5mm taller headtube and a 10mm lower bottom bracket height. The headtube is now tapered to 1.5″ at the bottom, so it’ll run the latest lightweight forks, too. On this model, the new tapered Rockshox World Cup SID XX handles front suspension.
UPDATED! 6/30/10 – cutaway photos, full model specs and pricing at bottom. Check the 949 29er here.
Check out more specs, details and photos after the break…
The top of the line model gets full XX, from brakes to drivetrain, but not the fork shown here. Ritchey WCS supplies the post, but not the bar and stem shown. The Cateye computer was just on there for display and does not come with the bike. Full specs for the 899 model at bottom of post.
The main way Scott dropped weight on the new 899 is by moving from tube-to-tube construction on the old model to increased use of their IMP (Integrated Molding Process) construction technique. As you can see in the image above, it removes a lot of excess material. In the headtube area shown, this new design is said to shave 15g and increase stiffness by 10%.
The result is a shapely tapered headtube.
The downtube remains very wide all the way from the headtube to the BB30 bottom bracket. Several changes in the bottom bracket area further improved stiffness and performance while dropping weight. First, the seat tube flares out, which improved stress resistance in Scott’s FEA testing and allowed them to use less material with the wider design. Next, they removed the alloy threaded inserts and used press fit bearings, keeping the frame all carbon. Lastly, the wide downtube reduced frame stresses better than the narrower tube on the prior model.
All together, these three changes dropped 30g while increasing stiffness by 15%.
At the top of the seat tube, they used this trick seat bolt design to replace the clamp. Even the lightest collars/bolts are about 16g, and this design is 5g, saving them 11g.
UPDATE: This trick little seat clamp is only used on the top-level HMX Net carbon frames, so not all Scale carbon mountain bikes will get it, and none of the 29er models. It requires a little extra attention in the form of carbon grease and a torque wrench to use it properly.
In the rear of the 899, Scott used a new Tubular Structure design with carbon dropouts. The “Tubular” part refers to the one piece “tube” that makes up the seatstays, dropout and chainstays.Â The brakes are moved to the inside of the rear triangle to take the braking forces off the seatstay. Why?
Because the seatstays on the 899 are oval shaped, wider than they are tall, and designed to flex to provide a little compliance while remaining laterally stiff. Scott wanted to remove braking forces from the seatstays so they wouldn’t interfere with their ability to soak up trail vibes.
With a 200kg load on the seatpost (and when you hit a bump, you’re putting far more than that amount on your bike, even if you’re a lightweight), Scott measures rear axle deformation (ie. vertical movement) at 4.66mm, which is about 1mm more than the prior Scale. The Tubular Structure assembly is also 25g lighter and 10% more laterally rigid, according to Scott.
Further weight was removed via the direct mount brake system in the rear, and by going to internal cable routing, they removed all the alloy guides, screws and parts that added up to about 47g. The plastic cable guide on the bottom bracket’s exterior and four bottle cage bolts only contribute 11g for a savings of 36g from previous Scale.
The bike shown here was for demo purposes and not built to actual spec. The actual production Scale 899 will be spec’d with DT Swixx XCR 100 carbon fork, DT Swiss hubs and carbon rims, Selle Italia saddle and Scott Pilot SL handlebar and stem. All other spec is as shown, except the tires will be Furious Freds, not Rocket Rons.
MSRP TBD, and there will be three models using this top of the line frame with Scott’s new HMX Net carbon fiber, called the Scale 899, Scale Premium (with 2011 XTR) and Scale RC. Below that, there’s the Scale 10, 20 and 30 that get the HMF Net carbon fiber which is slightly heavier and less stiff (just slightly). Lastly, there will be a Scale 70 with a lightweight alloy frame.
Want more? The 29er version is called the 949. Guess what it weighs?
Scott showed us some internal cutaways to illustrate how they shaved weight from the old Scale to get it down to a max 899g.Â Here’s the old bottom bracket (left) with aluminum threaded insert versus the new one (right) made for press fit bottom brackets. Notice, too the wider, thinner seat tube section. The wider tube lets them use thinner construction while still making it stiffer and stronger.
Another view showing the cross section of the downtubes.
The new headtube (left) with IMP molding construction forms the entire front triangle (excluding the seat tube) as one piece, eliminating a lot of excess material. The old tube-to-tube version is on the right. The discrepancy in headtube height shown here is more a matter of different size frames being represented rather than actual changes from old to new.
This is an external comparison of the new (left) and old (right) dropout areas. The old version had aluminum sections for the dropout and brake mount bonded to the frame, adding weight. The section on left is one tube with molded in direct brake mounts and full carbon dropouts.
Another comparison showing the insides of the new one and outside of the old one.
And here’s both sides of the new dropout/stays section. Click any of the pics above to see it in better detail.
MODELS, SPECS AND PRICING
Shown above are three of the models below the 899 that’ll be coming to the U.S. market, high to low from right to left. The red/white/black is aluminum, the other two are carbon.
Specs and pricing coming soon…