A spring is a simple thing: It temporarily stores energy and releases that energy as soon as the load starts to decrease again. However, if you want to use that spring in mud and dust, year in year out and you expect it to work as smooth as on day one, it isn’t so easy anymore. Oh, and it should also be lightweight, super supple but supportive for aggressive riding? It’s definitely time for some precision engineering. Check out how the F 535 ONE s LINE-AIR and COIL PAIR systems came to be.


There are many needs a spring system has to meet. The spring of a mountain bike fork has to be super supple in the beginning stroke. A low break away force is necessary to make sure your front wheel is always connected to the ground, offering traction and absorbing the little vibrations which would make you tired. In the middle of the stroke the spring has to support you. The so called midstroke support makes sure the fork doesn’t sink in its travel. If this were to happen, your center of weight would move towards to bar and the risk of going over the bar increases. For the big hits the fork has to offer a proper bottom out control. The end progression ensures that the force needed to compress increases at the end of the travel, making sure you don’t bottom out. The spring system also has to be low weight, easy to adjust to the rider’s weight and to his riding style.


What we call Frankensteins are essentially prototypes of spring systems, built so they work as intended but can be installed into existing forks both from DT Swiss and competitors. The idea is to get a feeling for a system in a chassis that we are very familiar with and then put that system into the 535 platforms competing forks.

Frankenstein Nr. 1
Two positive air chambers placed in line. A low pressure one takes care of the small stuff, while the high pressure one provides support and bottom out resistance.

Frankenstein Nr. 2
A COIL PAIR system for plushness is paired to a positive air chamber and a coil negative spring system.

Frankenstein Nr. 3
Essentially the prototype for the F 535 ONE’s spring technology: A COIL PAIR system matched to an  positive-air-negative-air spring system.

You don’t build three Frankensteins without a reason. And our reason was the idea of making a spring system that outperforms anything else available for all mountain bikes.


After extensive testing of the three Frankenstein systems, most testers (internal and external, pro and Joe average riders) voted for one system: The positive and negative air chambers Frankenstein in conjunction with the traction enhancing mini, positive coil spring unit. Out of the three tested options, it felt the best in all riding situations promising to be the easiest in handling (and the most durable). And it worked well together with our existing air volume adjustment system APT, giving every rider on every fork the full range of progression adjustment

A small coil spring works with the air spring in the first 30 mm of travel. Due to the zero breakaway force (1) of the coil spring, it compresses before the air spring piston even starts to move. The COILPAIR produces real coil sensitivity in a lightweight spring system ensuring small bump sensitivity.

The large volume of positive and negative air chambers are key to the linear spring curve (2), which is also responsible for the mid stroke support. An air bypass auto balances the air spring system of the F 535 ONE fork.

APT gives every rider the full tuning range for the air spring progression (3). By adding APT spacers, the forks gets more progressive at the end of the travel, made for strong riders with an aggressive riding style. By removing APT spacers, the spring curve is linear over the entire stroke.

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