The fat aluminium tubes are a constrast to the skinny items seen elsewhere in the test, but this rigid Cannondale uses them to create one of the most old-school - and lightest - rides here.
Long stretch
The Trail SL has a racey, stretched out feel, with a 624mm top tube (Large frame) combined with a long 100mm stem and a layback seatpost. The big 1.5in steerer is undoubtedly stiff, but it makes finding alternative stems harder, while the narrow 700mm bars don't give you much leverage anyway. The huge, 20mm conical spacer underneath means the front is very high, even with the seven-degree rise stem flipped. Add a road bike-like 71-degree head angle and the result is a bike that likes to be steered while upright rather more than when leant over.
At 10.5kg (23.2lb) it's extremelylight - its claimed frame weight, at around 1600g, is a pound less than the Shand's steel one for instance, and the Cannondale's 444mm chainstays and tight 1111mm wheelbase keep it very agile and poppy on tight trails.
What's more of a surprise is how comfy it is, despite the choice of material and those skinny 2.1in Racing Ralph tyres. The predictable claims of 'vertical compliance' for those heavily-kinked seatstays are hard to refute, though the bike's low weight/ inertia help it stay skippy rather than hammer-like. Some testers found Cannondale's Stage 3 seat too hard and angular, however.
Stiff fork feel
Push on down a rough descent and the Fatty 29 rigid fork and big headtube feel relatively stiff, but the QR axles don't. The bike is ready to go Stan's ZTR Rapid rims won't play well with high-volume 2.4" + rubber, but there's good clearance in the frame and fork for bigger tyres.
Not that higher volume rubber will help with pedalling. If you're the kind of rider that thinks life is pain and mountain biking is suffering, this is your design. Measurements with Strava reveal that the 20T rear/33T front gearing is good between 4-12mph and wrong for everything else.
Against the other bikes, this singlespeed is slow on faster, smoother trails and roads as you're soon forced to coast, while it's not just the gradient that kills you on climbs when you're forced to stand.
A bolted seat collar is awkward to adjust come the descents, and while the composite-bodied Magura MT2s lack power, they work well on this light, momentum-focused bike. The other kit is basic: the Truvativ cranks are square taper with solid arms, while the Formula rear cog (sitting on a Formula hub) is simple stamped steel.
Summary
The Trail SL 29 is an acquired taste, even if you only acquire a taste for heart attacks. Don't be fooled by that sub-24lb weight. The Cannondale is a low-maintenance, low-spec bike that will challenge your abilities, both through its uncompromising lack of gearing and racey handling.
Attention mounts
The Cannondale has rack mounts at the rear if you’re planning on riding it far, so it’s easy to strap several pairs of fresh legs on for when yours explode. It also has two sets of bottle mounts so you can hydrate with liquid morphine once you run out of legs.
You fat fork
The Fatty rigid fork saves a lot of weight and fits well with the bike’s character, but it’s suspension-corrected anyway, which means that should you want to switch to a fork with moving parts, you won’t ruin the intended angles. The Trail SL frame can take 100mm of bounce.
The Kinks
The notable dogleg where the seatstays meet the dropouts is there to allow them to flex vertically, in which direction the tubes are slim. Making them oval, rather than simply thin and round, keeps lateral stiffness high. It works. The Trail SL 29 could be brutal, but it isn’t.
Ex-spline yourself
The Trail SL 29 features a square-taper bottom bracket, where the non-driveside arm presses onto a solid, square-section steel pin. Most mountain bikes use much bigger circular axles cut with splines, onto which the matching arm slots: hollow axles and bigger interfaces are far stronger and stiffer. Does it matter? For years almost all bicycles used square tapers – many general-use bikes still do – but mountain bikes in particular need more. Shimano kicked things off with its Octalink (eight splines), but prevented anyone else making compatible parts. Several other companies subsequently grouped together on a 10-spline version anyone could use, and splined cranks are now almost universal. In 2015, square tapers are purely cost-saving measures.
FRAME 6061 aluminium
FORK Cannondale Fatty Rigid 29
WHEELS Formula DC20 hubs, Stan’s ZTR Rapid rims
TYRES Schwalbe Racing Ralph Performance, 2.1in
BRAKES Magura MT2
SIZES S, M, L (tested), XL, XXL
WEIGHT 10.5kg (23.2lb)