Shortening struts
Last Updated on July 22, 2024 by Mutiara
When lowering springs are not an option, coilover suspension seems the only logical choice. To avoid spending extra money on coilover suspension, there is another way to lower a car which costs about $ 50. The basic idea is to shorten the strut housing and rod 2″-3″ so that it doesn’t bottom out when the springs are cut 3-4 coils. The following is a guide to help demonstrate one example that was performed to the struts on a VW MK1 Jetta.
The strut insert was cut apart so that the internal pieces could be shortened.
Tapping the end of the rod will push the valve out of the bottom of the tube. Allowing removal of the rod for modification by getting it turned on a lathe in a machine shop. In this example the rod was shortened by 2 in.
Here are the rods after they were shortened 2 in. To keep the machine shop bill cheaper, the die was run by yourself to create the 14 mm x 1.5 threads.
Now its time to shorten the rest of the strut pieces. A pipe cutter can be used to make a clean cut on the tube.
After the tube has been shortened, the shortened rod should be reinserted and the valve should be gently tapped back on the end of the tube.
Now the shock housing must be shortened 2 in and welded over the shock tube rod and valve. Welding struts should be done with caution to avoid overheating.
While the shock housing was apart, a .25 in hole was drilled near the top to allow the strut to be refilled with oil. A good alternative to shock oil is to use some fork oil as seen in the following pictures, obtained from a local motorcycle shop. The oil used has to be designed for shock else it will foam during operation. In this case thicker oil was used so that the ride will be stiffer on the slammed MK1 VW Jetta, hopefully to prevent it from bottoming out. The housing was filled with a syringe and the shock cycled several times to bleed any of the excess air.
Once the shock is bled, hold the shock up-right with the rod fully extended, and fill the housing one last time. Keeping the shock up-right, compress the rod and purge all of the excess oil. Now fully extend the shock once again, and plug the fill hole. This procedure is critical to proper shock operation, it needs to have a certain amount of air for fluid transfer. To plug the hole, a small patch can be carefully welded over it.
The last step is to shorten the strut housing to mach the 2 in shorter strut inserts(shocks).
Now that the struts have been shortened the car will go 2 in lower before bottoming out, and have a unsprung height 4″ closer to the ground (and the cut springs will not be loose between the strut and strut hat). In the previous example, the springs were cut 3.5 coils for a conservative slammed ride.
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Pictures and information courtesy of Franz ([email protected]).
