The facts about the Trail Racer 29 running fork
Weight: 1100 g (pre-series, 990 g planned)
Geometry: 487 mm height (distance from thru axle to fork crown), 45 mm offset
Spring travel60 mm; three spring stiffnesses available (50-75 kg, 70-95 kg and 90-110 kg)
Price: 990 euros, www.laufforks.com
In Iceland, people live somewhat isolated from the rest of the world. You can afford to think outside the box. Prosthesis developer Benedikt Skulason thought the same thing. The idea came to Skulason during his work: "We work a lot with composite materials. And as an enthusiastic biker, I realised that these materials are hardly ever used in the bike industry." Skulason quit his job and founded Lauf with the aim of designing a lightweight, efficient fork. The Trail Racer 29 is the result of development work on prosthetic legs and feet. At just under a kilo, it lies exactly between the 1600 grams of a 29er suspension fork (e.g. SID) and the 600 grams of a carbon rigid fork.
The only one without bearings and pivot points
Extravagant design, simple principle: the Trail Racer 29 (TR29 for short) is basically a rigid fork in which the wheel is floatingly suspended via leaf springs. This makes it the only "suspension fork" in the world without any moving parts, bearings or pivot points. This is made possible by the patent-pending construction of fibreglass leaf springs (six on each side), on which the front wheel is suspended via two solid carbon dropouts with a 15 mm thru axle. As a result, the unsprung mass of the system remains record-breakingly low at 255 grams.
The fibreglass leaf springs, which originate from military applications, would be elastic far beyond the deformation limited by the bump stops. Even after years of use, designer Benedikt Skulason promises that there will be no signs of fatigue. As the springs are firmly embedded in the carbon dropouts and fork legs, you have to decide on a weight class before buying. The Lauf TR29 comes with a choice of three predetermined spring rates: for 50-75 kg, 70-95 kg or 90-110 kg. The TR29 gains its torsional stiffness from the special embedding of the wide leaf springs in the carbon fibre construction and the 15 mm thru axle. The 60 mm suspension travel doesn't sound like much. However, as there are no frictional losses in the system and the suspension is extremely sensitive at the beginning and very progressive as it progresses, as is usual with leaf springs, the overall impression is that it feels like more.
Anyone who experienced the beginnings of MTB suspension in the 80s will remember the - fortunately short - phase of undamped suspension with a shudder. However, the short suspension travel of the TR29 is designed in such a way that the lack of damping does not (yet) come into play. Despite all the extravagance, the Lauf TR29 fits any 29er that accepts a tapered steerer tube. The brake mounts are kept in the classic PM standard, and the glued-on guide points ensure clean cable routing. Because the 487 mm barrel fork is similar in height to an 80 mm telescopic suspension fork, you pay for the change from a 100 mm suspension fork with slightly steeper angles and a one centimetre lower bottom bracket. Eight standard colours are available. The question of whether it is better to call it a suspension fork or a rigid fork - or "both", as the fork's inventor says - is answered in the practical test.
The technology of the Lauf Trail Racer 29
- Full carbon construction with glued-in fibreglass leaf springs
- Tapered steerer tube
- Post-mount brake mount
- Axle system: 15 mm thru axle
A look back: crazy fork ideas from the past
The idea of suspension without damping is not new. There were already curious fork developments in the nineties:
Advantages and disadvantages of the Lauf parallelogram fork
+ Very sensitive to vibrations and minor impacts
+ 100% maintenance-free
+ Very light (for a suspension fork)
+ Very inconspicuous when pedalling
- More rigid than suspension fork
- Limited control in rough terrain (lack of damping)
- Slight tendency to bob when pedalling out of round
Interview with Benedikt Skulason, running CEO & designer
BIKE: The Trail Racer 29 is a very unconventional suspension fork concept. How did you come up with it?
Benedikt Skulason: The idea came to me during my work as a prosthesis developer, where I have a lot to do with durable but flexible composite materials. As an enthusiastic biker, I realised that these materials have hardly ever been used in the bike industry. My aim was to build a simpler, lighter and more (energy) efficient suspension fork. My first approach was a leaf spring system that flexes in one desired direction but is very stiff in all other directions.
By current standards, the 60 mm travel is very little - even for CC racing.
We are seeing more and more CC racers switching from 80-120 mm suspension forks to rigid forks - so we knew there was a gap in the market. In a CC or marathon race, you need very sensitive suspension to be fast. The running fork doesn't need a lockout as it doesn't absorb any energy. You never have to choose between suspension and efficiency - with the TR29 you always have both at the same time.
Would it be possible to design longer suspension travel with your undamped concept?
You can't have more travel without damping - the energy you put in during compression would act like a spring without damping. However, if you choose a firm suspension - as on the TR29 - the rebound energy is always at a controllable level.
Flex in bicycle components is often associated with fatigue. What do you think?
If you get the design right, composites can withstand an incredibly high number of loads. Just think of a prosthetic leg that goes through a load cycle with every step. In comparison, occasional use on a CC bike is almost negligible.
In its current form, the TR29 is a high-end product for ambitious CC riders. Do you see any other applications for your concept?
For sure. In addition to CC racing, we also see a large market for everyday use and hybrid bikes. The main advantage here is that our design is maintenance-free - with no bearings, seals or parts moving against each other.
Practical test: Running fork in the driving report
Firstly, the good news: with no adjustment or maintenance required, the Trail Racer is always a case of "get on and ride". In this respect, the TR29 is superior to any suspension fork. In terms of handling, it is absolutely inconspicuous - why not, the central geometry data is identical to normal MTB forks. When pedalling aggressively, you don't feel the suspension at all, and the minimal bobbing tendency when pedalling out of round hardly bothers you. On forest tracks, cobblestones, surfaces on which normal suspension forks respond too sluggishly, the TR29 inspires with enormous sensitivity - most comparable to riding a fatbike or with low air pressure, only with much more feedback from the ground and without the high inertia. The fork is made for such terrain. However, when the going gets tougher, over root passages or steps, it is above all the riding technique that determines how long you retain control. In any case, you can't just surf over them in a relaxed manner - the lack of damping makes the front end jump very quickly. Only with a lot of body tension, pressure on the front and a very active riding style (as with a rigid fork) can it be ridden quite well through rough terrain. In practice, the last third of the spartan 60 mm remains as bottom-out protection.
Conclusion on the Trail Racer 29 running fork
No doubt about it, the Lauf Trail Racer 29 was one of the eye-catchers at Eurobike. Conceptually coherent, the TR29 treads the middle ground between modern suspension forks and rigid forks in almost all respects (weight, suspension travel and price). In the practical test, the TR29 proved to be a comfortable option for suspension purists, as its riding behaviour is noticeably closer to that of a rigid fork than a real suspension fork. For forest roads, gravel tracks, moderate trails and smooth CC/marathon routes, the TR29 is a real alternative to a rigid fork. If you are also looking for control on rough terrain, it is better to stick with a suspension fork.
