Suspension systems on bicycles are becoming increasingly popular. Simply because, according to figures from the two-wheeler industry association, more and more people are buying pedelecs, springs and dampers ensure a more comfortable ride in the saddle for many people. Because e-bikes are rarely delivered without a suspension fork.
But such constructions not only make cycling more comfortable, they also make them safer. Because: The suspension has the task of keeping the tire on the ground as much as possible. "This shortens the braking distance, ensures more driving stability in curves and helps to avoid falls," says Arne Bischoff from the press service bicycle (pd-f).
Another reason why the complex technology is installed is mainly on sporty bikes: They improve the driving dynamics, which mountain bikers in particular welcome. Here the down-to-earthness is required. "Because with the tires on the ground, technically difficult passages can be mastered more safely and smoothly, the collateral effect is comfort," says Bischoff. The opposite is true for city and trekking bikes. “For most everyday cyclists, comfort is the number one reason they choose suspension,” says Bischoff.
Weight-optimized racing bikes ride without complex suspension systems, simply because they are too heavy. They are also hardly necessary on smooth asphalt.
There are attempts to make it a little more comfortable for racing cyclists too: Seat stays, seat tubes, seat posts and handlebars are designed in such a way that they "flex" more, i.e. twist under load. "Carbon as a material is particularly suitable for this," says Arne Bischoff.
More complex suspensions also have a kinetic energy damping component. Its task is to regulate the speed of the compression and rebound movement in order to prevent energy-sapping rocking movements while riding, says Ulf Hoffmann, an experienced cyclist and author. If a suspension were to release the energy absorbed during compression without braking, the bicycle would tend to leapfrog.
"The trick with bike suspension is to separate the sprung mass from the unsprung mass," says Hoffmann. Wheels and spring elements should “swallow up” impacts from the ground as far as possible and not allow them to penetrate to the driver – a technological challenge, since the unsprung mass on the bike makes up a higher proportion of the vehicle – unlike cars with their comparatively small wheels, says Hoffmann.
In order to catch potholes and the like as sensitively as possible, both the spring hardness and the damper should be adjustable. You should stay away from cheap suspension forks, advises Hoffmann: "It's better to use rigid forks and wider tires."
The tire should not be forgotten as the bicycle component that is the first to react to impacts. Wider tires that are ridden with less air pressure expand the intended use, mainly on gravel bikes, without the need for expensive suspension systems - "provided the wider tires fit through the frame and fork," says Bischoff. With city bikes, balloon tires can provide sufficient comfort instead of more technology.
The three most important suspension components on the bike at a glance.
The most common suspension element on a bicycle is a suspension fork. Suspension forks are now a matter of course on mountain bikes. Trekking or city bikes as well as gravel bikes are often equipped with them. While suspension forks with steel springs used to be common, today air suspension forks with an oil damper are standard.
Telescopic forks, which are built from standpipes and dip tubes, are common. If you drive over an obstacle, the standpipe slides over the immersion tube. The spring deflection describes how far this happens. While this is between 80 and 100 millimeters on trekking bikes, the fork tubes on downhill and freeride mountain bikes are pushed into each other by up to 180 or even 200 millimeters, says Ulf Hoffmann.
Suspension forks are also a good sales element as a comfort feature. "That's why many cheap models are installed that have maximum cushioning but not dampening and are therefore not worth the money," says Hoffmann. It is better to rely on models where the fork can be adjusted to the rider's weight and riding style - both the speed of compression (compression) and rebound (rebound). "Good suspension forks can also be blocked, ideally by remote control from the handlebars."
One of the disadvantages of suspension forks is that they require maintenance. "Most fork manufacturers prescribe maintenance after 50 to 100 operating hours," says Hoffmann. Cost in a specialist workshop or from the manufacturer: around 100 euros. According to Arne Bischoff, only experienced hobby mechanics could do this "fork service" themselves and thus save costs.
Tip: Hoffmann recommends turning the bike upside down from time to time to extend the service life of a suspension fork, because the oil then gets to the upper seals and foam rings. However, you have to be careful when hydraulic brakes are on board. These can pull air, which is why it is best to put them on with a rubber band. Regularly wiping the fork tube with a soft cloth with a drop of suspension fork oil on it will also prevent wear.
The technically correct term for frame dampers is spring strut. According to pd-f, the components on the frame that promote comfort and traction are only colloquially called frame dampers.
Shock absorbers are primarily found on mountain bikes and “high-priced e-bikes,” says Bischoff. In principle, a suspension fork is also installed. These full-suspension bikes are referred to as fullys (“full suspension bikes”) in the mountain bike sector. "The rule of thumb is: The rougher the surface and the faster the ride, the more suspension travel is required."
As a rule, oil-air suspension is installed; steel springs, which are more robust but cannot be adjusted in terms of spring hardness, are less common. Typical spring travel for everyday bikes and mountain bikes for moderate off-road use and cross-country mountain biking is 70 to 120 millimeters. Constructions in downhill sports give way by up to 200 millimetres.
According to Bischoff, the aim of rear suspension is that the rear wheel can follow the ground and return to its original position in a controlled manner after the compression or rebound movement.
In other words, here, too, the unsprung mass has to have the best possible grip in order to maintain traction: “Away from asphalt, rear suspension is often even more efficient than a rigid construction, because drive and braking forces do not literally dissipate in the air while the rear wheel jumps .”
In bicycle technology, there are a number of variants of how this principle is implemented - from single-joint rear structures to more maintenance-intensive, but also more finely adjustable multi-joint rear structures, of which four-bar rear structures are the most common. "The engineers use a lot of imagination to optimize the joint and lever systems," says Hoffmann.
Elastomers are mostly only used for the suspension of the rear triangle on special bicycles, such as folding bikes - small, yielding plastic parts that require little maintenance and are inexpensive, but the spring hardness cannot be adjusted. But they can be easily exchanged and adjusted to the weight of the driver. "They don't offer the performance of a shock absorber by a long shot," says Bischoff.
However, they can sometimes also be found on gravel bikes, where heavy and visually striking suspension elements are often just as little in demand as long suspension travel, since these types of bikes are built for rather easy terrain. The small wheels of child trailers are partly sprung with elastomers.
Tip: You should check the air pressure of the damper every month. Author Hoffmann advises wiping pistons with a cloth after every ride through dirt and mud. The joints should be greased regularly according to the instructions.
"One should also pay attention to changes in driving behavior." As soon as squeaking noises occur, the damper is difficult to move or oil is leaking somewhere, it's time to visit the workshop. Frame dampers can be protected with special neoprene covers.
Suspension seat posts are an alternative to suspension rear wheels for leisure use. "They are purely a comfort feature and do not change the driving dynamics at all," says Bischoff. But they increase comfort - which is why they are mostly found on city and trekking bikes, sometimes also touring bikes, but rarely in the sports sector.
Two types are widespread: the telescopic and the parallelogram seat post. Leaf spring seat posts for racing bikes play a secondary role.
According to Bischoff, the first variant is somewhat more difficult. The seat post moves up and down as an extension of the seat tube. "Telescopic spring supports operate with a steel spring whose preload can be adjusted." Spring deflections between 20 and 50 millimeters are possible.
Parallelogram seat posts are more robust, lighter, more expensive and rely on elastomers. "The greater the suspension travel, the more important it is to be able to adjust the suspension to the weight," says Bischoff. With both solutions, the seating position is slightly changed when the spring deflects.
"But that's more of a theoretical nature" and doesn't bother you when cycling in everyday life, even if the differences are geometric, says Bischoff. "It is important in all constructions that the seat post and the rider's weight are compatible."
Tip: According to the author Hoffmann, one advantage of suspension seat posts is that they can be easily retrofitted. "But you should make sure that the support fits the diameter of the seat tube."
Under no circumstances should you retrofit a suspension seat post if the rear end already has suspension. "The two systems are virtually in competition with each other and together can lead to dangerous situations."
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