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On modern racecars, shocks run at very low main piston speeds. In addition, they are forced to have very little travel in order to keep the car’s aerodynamic changes to a minimum. The result of this short stroke is only a small volume of oil is displaced during the stroke cycle. A shock absorber is a dynamic device. It only works when it is moving. As a result, the most important characteristic of a racing shock is precise control over this small volume of oil moving at low speed.



How to deal with this problem?

Most racing shock designs utilize a relatively small diameter piston rod and a needle valve for controlling oil flow. ProTac uses a large piston rod in order to deliver maximum fluid displacement at small suspension travels.

Although the needle valve is a simple and effective mechanism, it has it’s problems. The major disadvantage of this system is extreme sensitivity to manufacturing tolerances, temperature variations (oil viscosity) and it is VERY easily damaged. Any of these can cause variation in damping force between shocks as well as making adjustments ineffective. Regular performance checks are necessary on needle valve shocks to ensure properly matched sets. You can wind up spending more time on the shock dyno than on the track.


ProTrac's solution

ProTrac believes that accuracy, consistency and repeatability are the most important design requirements. Therefore, ProTrac has designed an advanced and very accurate adjustment mechanism for rebound and compression control.

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BMW E-36 McPherson Strut and rear damper with special designed bracket






ProTrac’s advantages

Because the large piston rod displaces a large amount of oil, ProTrac’s rebound and compression mechanisms work more efficiently.

Instead of needle valves, ProTrac uses porting for rebound adjustment. Performance depends on the precision of the ports. ProTrac’s ports that have been very precisely drilled on a CNC milling machine to ensure that their position and diameter are within the very fine tolerances necessary for total repeatability. The accuracy and repeatability of CNC-milling also assures that all shocks in a set have exactly the same characteristics.

On the compression side, ProTrac loads the blow-off valve with Belleville springs because of their proven accuracy and consistency. The blow-off valve is matched to the large oil displacement caused by the large piston rod diameter and responds to the smallest movement of the suspension. The system can be precisely tuned to your specifications and requirements.

More neat stuff on ProTrac Shocks

Another advantage to ProTrac shocks is the use of the gas pressure in the remote reservoir as an adjustable medium. In combination with the large oil displacement, the gas pressure assists in supporting the chassis without increasing the spring rate.

This feature of ProTrac shocks allows the suspension engineer to use gas pressure as a setup instrument and saves valuable track time.

The ProTrac shock is built as a modular shock, so all of our shocks share the same high performance features and the shock lengths and damping characteristics can be modified according to your individual needs and specifications. Because ProTrac uses long-life seals and shock oil especially developed for endurance racing, our shocks require very little maintenance.



Rietdekkerstraat 3, 5405 AX  UDEN, The Netherlands
Phone:  +31 413 259 100  Fax:  +31 413 259 770    Email: info@protrac.nl

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