This is Bianchi’s first proper year designing 650b bikes. From a first glance at the Ethanol's geometry tables, it’s as if the maker hasn’t really adjusted anything to allow for the larger wheels.
Frame and equipment: gorgeous foundations
The head angle is 71 degrees and the seat angle is 73.5 degrees – numbers you find on 26in cross-country bikes. The bottom bracket height is racer boy-low, however, which means a BB drop (how low the crank axle lies below the wheel axles) of 50mm.
The frame has obviously been tweaked from Bianchi’s previous 26in-wheeled carbon hardtails to accommodate the larger wheel, but it hasn’t changed drastically. The maker clearly wants to stick with its tried and true racy geometry.
The bottom bracket sits low, which helps the 650b machine handle differently to a 26in bike
The tapered head tube is nicely short for maximum stiffness. Bianchi’s considerable experience with carbon road frames reveals itself here: the flowing lines somehow making the head tube/down tube/top tube junction an exquisite exercise in elegance, even as it creates great strength.
The plain round seat tube is almost a letdown aesthetically when you compare it with the sculpted arrangements running alongside it. It’s surprising that Bianchi doesn’t spec a direct-mount front mech – the cheap Acera is a traditional band-clamp design.
The BSA bottom bracket shell is thrillingly huge and contains an FSA MegaExo Integrated bottom bracket, while the twin-ring (39/27T) cranks are FSA Comet Compact 386 MegaExos.
The down tube is a real piece of work, and a great example of what can be done with carbon. It flows out of the head tube, becomes square then morphs to a more voluminous trapezoid – until it reaches the underside, and pretty much fills the whole width of the bottom bracket shell. It looks (and rides) extremely stiff in this area, yet the frame weighs just 1370g. It would take some special work to make a frame as stiff and light as this out of any other material.
The flattened top tube and dipped-tipped seatstays give the appearance of softening the ride, but it’s hard to tell if it’s just that – an appearance. They give the frame a lovely aesthetic, at least, which is never a bad thing.
The more significant aspect is that the ample standover leaves a lengthy amount of seatpost sticking above the frame, and said post is a skinny 27.2mm. This is where a genuine amount of welcome comfort emanates from.
Skinny seatpost helps provide some comfort when aboard the stiff carbon-framed Ethanol
The finishing kit has clearly been chosen to meet the price, which is entirely acceptable. You can always upgrade stuff in the shop if you have the cash, and while the RockShox 30 Gold TK Solo Air 120mm fork is a little flexy – especially on this super-stiff frame – it performs decently enough when run hard and with lots of rebound damping.
Ride and handling: small is beautiful
During the test, a common query was why anyone would want a racy hardtail that wasn’t a 29er. Big wheels are generally faster for the riding this bike is suited to – what’s the point of a 650b carbon hardtail?
It took a couple of rides for it to dawn on us. This isn’t just a race bike; it’s a lovely hardtail. Don’t be fooled by its roadie brand and too-long stem. It’s versatile.
The generous BB drop – more than a 26in wheel can accomodate – makes the Ethanol handle differently to a 26er. You feel very ‘inside’ the bike. Even though the ride is still on the twitchy side for riders used to slacker (68 degree or less) head angles, our testers felt secure and confident on steep and technical trails we pointed them down. (Some did, however, swap the 100mm stem for a more modern, trail-friendly 70mm.)
Despite claims that it’s less racy than Bianchi’s other hardtails, the Ethanol is still a very stiff frame. Its fat down tube and deep chainstays combine to make a mighty fine platform for ragging the thing around under shaven-legged power.
Tapered head tube is nice and short to aid frame stiffness
The slight but noticeable increase in traction and buzz-soaking that comes with 650b wheels is welcome on short blast rides and extended days out on the trails. We didn’t particularly get along with the Hutchinson Cobra 2.1in tyres during our wintery test period, mainly because the semi-slick-middle tread was sketchy under damp braking. They’re well worth keeping for drier times, however.
All in all, this is a fast and responsive bike that reminds us what it’s like to ride a smaller-than-29in wheel on a carbon hardtail.
Gone is the seductive steamrollering and carving-cruising attitude of big hoops: the 650b Ethanol is much more of an involved and close-up experience. Some would say it's sketchier and slower – it almost certainly is – but it sure is brilliant fun.
We rather like that Bianchi places emphasis on offering a truly great frame and leaving it to you to replace and upgrade parts as you go. The prime candidates are its agricultural Shimano M445 brakes and chunky wheels, but with a stiff, light and undeniably stylish frame at its heart, the Ethanol is a bike worth keeping, riding and upgrading for years.
