New answers to old questions Everything used to be simpler. In the early years of the mountain bike, there was little need for discussion when it came to geometry. The young off-road bikes were little more than robust copies of road racing bikes. People were cautious and hardly dared to deviate from the established dimensions. A steering angle of 70-71 degrees and a seat angle of 72-73 degrees were the law. There was also little room for manoeuvre with the other dimensions. But this changed dramatically over time. Better suspension, better riding technique, more technically demanding trails and the diversification of mountain bikes according to areas of use - the geometries of the bikes also changed rapidly as a result.
The test evaluation of the three geometry concepts can be found in the link list at the bottom of the article:
- Canfield Bros. Riot
- Ghost SL AMR X LC9
- Nicolai Ion-G13
For a while, people thought they had understood what was important on a modern mountain bike. But then came the 29ers. And suddenly we had to find new answers to old questions. The main aim was to utilise the advantages of large wheels without making the bikes too sluggish. One of the first approaches to improving the often cumbersome handling of the early 29ers was Gary Fisher's G2 geometry. With the help of a larger fork offset (see explanation on the right), the trail was shortened, making the steering more agile - 51 mm fork offset is now a fixed standard for 29er forks. At the same time, developers also focussed on the chainstay length. However, the call for more playfulness, which was to be achieved with shorter rear triangles, brought with it other design necessities: shorter chainstays with sufficient tyre clearance were the birthplace of single-speed drivetrains and wide Boost hubs.
At the same time, modern production techniques with hydroformed aluminium and carbon as a material brought additional freedom for the designers. And the growing enthusiasm for technical trails and high downhill speeds demanded high-performance chassis and slack steering angles. The fast-forward geometry introduced by Mondraker in 2012 and co-developed by downhill legend Fabien Barel was another milestone in modern mountain bike development. Even if the concept - like many innovative ideas before it - initially overshot the mark, it has developed into another lasting trend: Longer top tubes and short stems bring smoothness and safety reserves, but at the same time create very direct handling. This idea is now gaining ground in trail, all-mountain and enduro bikes, and it also seems to be gaining a foothold in the cross-country and marathon sector.
Three archetypes In principle, we now have three archetypal geometry concepts in which the developments of recent years have been incorporated to varying degrees and with different priorities. Our three all-mountain test bikes are representative of these three geometry concepts: with its modern mainstream geometry, the Ghost SL AMR X takes a middle course in all areas and thus remains very versatile. The Geolution concept developed by Nicolai adheres to the motto "length brings safety and speed". Characterised by a very long top tube, chainstays and wheelbase and an extremely slack steering angle. Originally, the Geometron bikes, which were developed with British suspension expert Chris Porter, were only intended as a concept study. However, Kalle Nicolai was so impressed by the riding impressions that he developed a complete series for 2017. Of course, with its extreme geometry, the Ion-G13 is right on the edge of what can still be called suitable for the masses. The Canfield Brothers Riot goes in the opposite direction. With its ultra-compact geometry, it wants to prove how playful a 29er can be, but at the same time uses a slack steering angle to stabilise the steering.
Three bikes, three concepts - but only the interplay of all lengths and angles creates the individual character of a bike. This is because every bike geometry is always a compromise of different, sometimes contradictory riding characteristics. Today, we recognise three major geometry trends, but also a multitude of individual characteristics.
CONCLUSION by Christian Artmann, BIKE tester:
Length matters - an old adage for sailors, but a fairly new realisation in mountain biking. The extreme geometries, such as on the long Nicolai Ion-G13, result in interesting riding characteristics, but also a certain one-sidedness. As the search for the perfect bike is often also the search for the ideal compromise, the majority of bikers will tend towards more moderate geometries.
Mountain bike geometry explained in brief
Reach, stack, wheelbase, chainstay length, steering angle, trail - don't worry! For a rough estimate, it is sufficient to concentrate on a few key values.
1 Reach
The term refers to nothing more than the horizontal distance between the bottom bracket and the head tube axle (measured at the upper bearing shell). It is independent of the seat angle and is therefore primarily a measure of how compact or long a bike is when standing. The top tube length (1a) is also influenced by the seat angle, which is why it indicates how long a bike feels when seated.
2 Steering angle
It largely determines how agile or smoothly a bike steers, how quiet it remains at high speeds and how safely it rides on very steep sections. The slacker the angle, the safer and smoother the bike becomes. Up to a certain point, because then the steering starts to tip. The more aggressive the area of use, the slacker the steering angle (e.g. Cross Country: 69-71° and Enduro: 64-67°).
3 Seat angle
This measurement helps to estimate the weight distribution on the bike. In the age of curved and offset seat tubes, the effective seat angle can rarely be measured directly on the seat tube. It also depends on the extension length of the seat post. Generally speaking, there is currently a trend towards steeper seat angles, which makes climbing easier. It can be varied +/- 0.5° via the saddle position.
4 Chainstay length (also known as rear triangle length)
Short chainstays make the bike more agile and ensure that it is easy to pull onto the rear wheel (e.g. on drops and manuals). However, the centre of gravity quickly shifts too far back on climbs - the bike rears up early. Especially playful bikers and those who ride a lot in the pedalling position benefit from short rear triangles. The additional smoothness and climbing performance when seated due to longer chainstays can in turn be an advantage for touring riders.
5 Wheelbase
The value is influenced by chainstay length, reach, steering angle and fork length. However, as a measure of the subjective size of a bike, it is only really meaningful in direct comparison. The longer the bike, the more stable it is, but also the less manoeuvrable.
6 Bottom bracket height
It determines the ground clearance when pedalling and when leaning. The bottom bracket drop (6a) sets the bottom bracket position in relation to the hub height and is different for each wheel format. It determines how integrated the rider feels in the frame. Both values are measured in the unloaded state and change when the rider sits on the bike.
7 Stack
The stack describes the vertical distance from the bottom bracket to the upper edge of the head tube. However, the effective seating position is also determined by the stem (length and angle), the handlebars and the spacers fitted. The head tube length (7a) also provides information about the height at the front if you know the fork height and the wheel radius.
8 Protrusion height
It is an indication of how much freedom of movement the rider has on the bike. The lower the value, the more space there is between the rider and the bike. BIKE always measures the value in the centre of the top tube.
9 Seat tube length
Formerly the main criterion for frame size, this measurement is becoming less and less important due to modern frame designs and long seat posts.
10 Fork offset
In addition to the steering angle, this value is another variable that influences the trail (11) and therefore the steering behaviour. It depends on the wheel format: approx. 42 mm for 26", 44-46 mm for 27.5" and 46-51 mm for 29ers.
THE GEOMETRIES OF THE 3 TEST BIKES IN COMPARISON
The 29er trail and all-mountain bike category currently offers the greatest variety of different geometry concepts. Despite similar suspension travel, all three mountain bikes have their very own character.
Canfield: compact and playful
PLUS The ultra-short rear triangle and the compact main frame make the 29er exceptionally playful.
PLUS The fairly flat steering angle ensures a smooth ride and provides safety.
PLUS/MINUS The steep, effective seat angle prevents you from rearing up too early on the climbs (due to the short rear end), but also ensures a very compact riding position, which means that the all-round characteristics suffer.
Ghost: Mainstream trail geometry
PLUS The geometry is a successful compromise of all characteristics and ensures a high level of versatility.
PLUS Suitable for almost every type of rider, riding style and terrain.
MINUS Due to the flat real seat angle, the effective riding position depends heavily on the saddle extension.
Nicolai: long and smooth-running
PLUS The geometry, trimmed for maximum smoothness, promotes subjective riding safety in technical, steep terrain and at high speeds.
PLUS The extreme length (reach and wheelbase) makes it very good-natured in the face of riding errors.
PLUS With the steep seat angle and the long rear triangle, you can master even the steepest climbs in a relaxed seated position.
MINUS Bulky in winding terrain due to the long wheelbase.
MINUS Long chainstays and forward weight make it difficult to lift the front wheel.
Stefan Herrmann, BIKE riding technique expert:
"For me, long frames and slack steering angles have almost nothing but advantages, because they provide riding safety and reserves where it counts - at high speeds and in difficult terrain."
Dr Kim Tofaute, bike fitting and ergonomics expert:
"The modern trail geometries provide stability and safety on steep and technical trails. On the other hand, they force the rider into a position that is no longer ergonomically optimal, which can be a disadvantage, especially on longer tours."
Geometry concept: Canfield Bros. Riot
Examples of the small bike forge Canfield Brothers from Bellingham, Washington are very rare on our local trails. The two brothers Chris and Lance build their bikes out of conviction and because they believe they can do things better. They are known as lateral thinkers in the industry. It is therefore not surprising that the Riot has an unconventional geometry. Instead of being long and flat, as the current trend dictates, the Riot has a fairly compact design. The most striking feature of the all-mountain 29er is the ultra-short rear triangle, which measures just 411 millimetres despite the generous suspension travel and 29er tyres - the shortest 29er rear end ever recorded by BIKE, hardtails included. This makes it easy to pull the bike onto the rear wheel or lift the front wheel over obstacles.
In general, the Riot with its compact, upright riding position is an open invitation to play, whether in technical terrain or on flow trails. Even on jumplines, it doesn't look out of place thanks to the moderate wheelbase. At the front, the slack steering angle ensures safety and forgiving handling. Critics of 29ers will be surprised at how atypically manoeuvrable and playful the Riot is. The fact that the front only climbs uphill late is due to the extremely steep seat angle and the seat position, which is thus shifted forwards. The in-house developed rear suspension kinematics work perfectly and harmonise very well with the Fox fork. All in all, the result is a chassis that is as comfortable as it is capable. In Europe, the Canfield Riot is only available as a frame or frame kit for customisation.
Peter Nilges, BIKE Test Manager:
The Riot is so agile and manoeuvrable that you can hardly believe you're sitting on a 29er. In contrast to the long Nicolai, getting used to the short geometry is much easier. Even beginners should be able to cope well with the good rollover behaviour of the large wheels and the easy handling. Very compact for size L.
Technical data Canfield Bros. Riot
available in specialised shops
Price 2399 Euro (frame without shock absorber)
Front / rear suspension travel 152 mm / 141 mm
Material / Sizes Aluminium / S / M / L / XL (48 cm)
Weight o. P. / frame 14.25 kg / 3543 g (without damper)
Fork / damper Fox 36 Talas Factory / Cane Creek Double Barrel Air CS
Cranks / gears Canfield AM / Sram X1, 11 gears
Gear ratio / handlebar width 30; 11-46 / 770 mm
Brake system / Disc Magura MT7 / 180/180 mm
Telescopic support Magura Vyron, 150 mm
Impellers Race Face Turbine R system wheels, Continental Baron 29 x 2.4 tyres
Reach / Stack / BB-Offset 445 / 630 mm / -21 mm
Geometry concept: Ghost SL AMR X LC9
The Ghost is a representative of modern, but by no means extreme trail geometry. Long, slack and progressive, but still fully in what could be described as mainstream. However, the first-class trail performance shows that this doesn't have to be a disadvantage. Confidence-inspiring, intuitive and yet suitable for almost every type of rider and terrain. The riding position strikes a good balance between sportiness and freedom of movement, which puts the rider in an "attack position" that is as safe as it is powerful. The handling is dynamic and unobtrusive in the best sense of the word - with a good portion of smoothness, but still universal. A bike that anyone can get to grips with straight away.
That the Ghost SL AMR X The fact that the LC9 is still more geared towards rough trails is due to the harmonious all-mountain equipment. As a bike that is also designed to be really fun on rough trails, the top-of-the-range LC9 model not only features a capable Fox 36 suspension fork, but also the new Cane Creek DB Coil steel spring damper with the high-traction Climb Switch function for uphill riding, which is exclusive to Ghost for 2017. The wide range of adjustment options on the fork and shock leave plenty of scope for personalised suspension set-up, but also require a little more knowledge when it comes to setup. The bash guard/chain guide, Magic Mary tyres at the front and the very stiff yet lightweight Race Face wheels with a 27 millimetre rim width complete the overall picture of a bike that can really accelerate downhill and still go well uphill. With such high-quality equipment, the price as a specialist dealer bike is absolutely fair.
Ludwig Döhl, BIKE tester:
The word mainstream has a somewhat bland aftertaste, but the Ghost quickly makes it clear that it is anything but boring. Compared to the two extremes, the moderate geometry is almost intuitive to handle. Sit on it, step on the gas and feel good. The potent chassis extends the range of use towards enduro.
Technical data Ghost SL AMR X LC9
available in specialised shops
Price 3599 Euro
Front / rear suspension travel 145 mm / 134 mm
Material / Sizes Carbon/aluminium / S / M / L / XL (48 cm)
Weight o. P. / frame 13.57 kg / 2510 g (without damper)
Fork / damper Fox Float 36 Performance Elite / Cane Creek Double Barrel Inline Coil CS
Cranks / gears Shimano XT / XT, 11 gears
Gear ratio / handlebar width 32; 11-46 / 780 mm
Brake system / Disc Shimano XT / 200/180 mm
Telescopic support Kind Shock Lev Integra, 150 mm
Impellers Race Face ARC 27 system wheels, Schwalbe Magic Mary/Hans Dampf Evo Trailstar 29 x 2.35 tyres
Reach / Stack / BB-Offset 444 / 629 mm / -34 mm
Geometry concept: Nicolai ION-G13
Nicolai's new Geolution line for 2017 is the direct result of last year's Geometron experimental bikes. It is intended to show the previously untapped potential that lies dormant in modern trail geometries. With the typical, almost industrial raw look of straight frame tubes, rough weld seams and all kinds of fine CNC milled parts, the ION-G13 already stands out visually. But the super-long Geolution geometry makes the ION-G13 even more of a frontier runner - even in medium, the four-bar frame is longer than some other bikes in size XL. Thanks to the ultra-short stem and the extremely steep seat angle, the riding position is nevertheless quite unobtrusive. Only the pedalling from above due to the steep seat angle takes a little getting used to on the trail.
On steep trails, the ION-G13 shows what it's made of. Even in extreme situations, the very smooth ride gives you the kind of confidence you would expect from an enduro race bike. The steeper and faster, the better. The long frame makes the bike very insensitive to changes in the rider's weight, but requires active pressure on the front wheel when cornering. Downhill, all feelings of rolling over are simply erased, and uphill you can still crank up in a seated position, where on most other bikes the front wheel has long since risen. However, winding trails with hairpin bends, drops at low speed or manuals present the rider with a technical challenge due to the extreme wheelbase. The rear suspension is quite firm. In the low position, however, the Nicolai overshoots the mark, which is why we favoured the slightly more moderate high position in the test.
Christian Artmann, BIKE tester:
The Nicolai ION-G13 pushes the limits with its geometry and polarises, which is why not everyone will be happy with it. Instead of simply sitting on it, the bike requires a period of familiarisation. After that, however, the Nicolai can be really fun and tempt you to push your limits, as it offers reserves where other bikes are already at the limit.
Technical data Nicolai Ion-G13
Price 5949 Euro
Front / rear suspension travel 140 mm / 132 mm
Material / Sizes Aluminium / S / M / L / XL / XXL (46 cm)
Weight o. P. / frame 13.84 kg / 3419 g (without damper)
Fork / damper Fox 34 Float Factory / Fox Float DPS Factory EVOL
Cranks / gears Hope Spiderless / Sram X1, 11 gears
Gear ratio / handlebar width 30; 10-42 / 780 mm
Brake system / Disc Hope Tech3 E4 / 180/180 mm
Telescopic support Rockshox Reverb Stealth, 150 mm
Impellers Hope Pro4 EVO hubs, WTB KOM-i29 rims, Continental Mountain King Protection 29 x 2.4 tyres
Reach / Stack / BB-Offset 481-488 / 612-617 mm / -24 to -32.5 mm
You can read this article or the entire BIKE 5/2017 issue in the BIKE app (iTunes and Google Play) or buy the issue in the DK shop reorder:
