Tech Features

This is a photo of the author behind the wheel of his Sand Cars Unlimited buggy in the Glamis dunes. Fast slides, big wheelies, G-outs, and long jumps were all part of a typical day’s fun in the sand and, after five hard seasons and a lot of trips, the King shocks needed to be rebuilt. This article is a brief overview of the process.

King Shock Rebuild

A basic look at what’s involved with rebuilding a bypass shock
By Mike Lyon | February 24, 2014

Photos by Mike Lyon


The shocks on your sand car are a key component in the suspension system. When they’re working properly they allow you to fly through rough terrain without rattling your teeth loose. After five hard seasons on our King bypass shocks, they were long overdue for a rebuild! We decided to have them professionally rebuilt by Dustin Dumas, owner of AG Sand Cars in El Cajon, California. Dustin has several years of experience building off-road race cars, sand vehicles, and rebuilding all types of coil-over and bypass shocks.
ABOVE, is the main shock shaft assembly as it looked after being removed from the shock body.
Dustin has been racing and playing in the off-road world for most of his life. In the late 1990s he worked with the crew at Jimco Racing, and during that time learned the inner workings of shocks from John Marking of Fox Racing Shox. In 2001, Dustin opened his own shop, AG Sand Cars, where be fabricates, repairs, and maintains sand cars and off-road racing vehicles. We have taken many cars to him for welding repairs, custom fabrication, and new sheet metal components. His work is always high quality and his prices are very fair. He has performed numerous shock rebuilds and suspension tunings, which gives him the experience needed to setup an off-road car’s suspension to optimal conditions.
This is the compression valving stack as it appeared after being removed from the contaminated oil and unfastened from the shock shaft. The valve stack needs to remain in order if they will be reused, and it is recommended that you consult with an experienced shock tuner before changing valves on your shocks.
We followed along as Dustin performed the rebuild and learned that it’s not as complicated as you may think. However, this is a job that should only be performed by someone with the proper knowledge. This article and the photos are merely intended to show an overview of the maintenance procedure. Technical data should also be referenced from the shock manufacturer before performing this service on your own.
Here's a look at the cleaned shock piston showing the holes that the oil moves through as the shock cycles. King offers several different styles of shock pistons.
With that being said, the first step is to release the nitrogen from the reservoir on the bypass shock. The reservoir has an independent floating piston with an O-ring around the circumference to keep the nitrogen and shock oil separate from each other. In our case, the O-ring was damaged enough to allow oil into the top half of the reservoir. When Dustin released the pressure from the Schrader valve, he was greeted with a nice shower of shock oil!
This is another view of the shock piston, which shows the valve stack, spacer and the teflon coated wear band. After all the parts were both cleaned and closely inspected, it was determined that we would replace the O-rings, seals and wear band.
After the nitrogen has been released, the next step is to remove the end cap on the lower main shock body and slide the shaft with the shim stacks and seals out of the shock body. Now the internal parts need to be removed from the shaft. On the end of the shock shaft is a nut that holds everything onto the shaft. Below the nut is a small spacer, the rebound shim stack, the main shock body piston, the compression shim stack, a tall spacer (the one that makes King shocks “click”), an internal end cap, another spacer, and finally the end cap and seal that screws into the shock body.
This is another photo showing the shock components as they were being disassembled. Internally, the shock is comprised of several different parts which must be kept in order as it’s being serviced.
With the internal shaft components removed it’s time to closely inspect each component for any damage. The chrome shaft must also be inspected for chips in the coating. If any are found, it will need to be replaced or re-coated. After inspection, the three seals on the internal end cap must be replaced, as well as the seal in the external end cap. Now is also the time to measure your shim stacks and make any changes depending on you and your car’s needs. With the main shock body rebuilt and reassembled, the reservoir needs to be removed to replace three o-rings and then reinstall the reservoir.
It’s a good idea to lay everything out as shown, above. The parts are labeled for your reference, which is helpful should you need to order new parts from a sales technician. The last thing you want to do is call something by its wrong name.
With the reservoir reinstalled, it’s time for fresh shock oil. Place the shock upside down in a vice and pour oil into the shock body. Slide the shock shaft with its installed components in and out of the shock body to ensure oil is pushed throughout the bypass tubes. This should be done slowly to not make a huge mess, as well as not create bubbles in the fresh oil. Top off the shock with oil until it’s full and tighten the end cap onto the shock body.
After everything had been serviced and reassembled, the shock shaft was put into a vice and held in place until the shock body was ready for it to be installed.
As stated earlier, this procedure is pretty straightforward, but would be better left to the professionals, such as Dustin. Someone with experience knows what to look for, and they’ll ensure that everything is in perfect working order. The cost for this service was right around $75 per shock, which included Dustin’s time, new seals, and shock oil. We felt it was well worth the cost since our shocks were not working anywhere near their peak performance.
Prior to reinstalling the reservoir, we replaced all of the O-rings, which includes the one you see for the lower reservoir cap, as well as the one that goes around the circumference of the independent floating piston inside the reservoir.
After the rebuild Dustin weighed the car and made a few minor adjustments to the coil carriers to even-out the weight balance. Once we hit the dunes again we immediately noticed a difference in ride quality. After we made a few minor adjustments to the bypass shocks, the car was handling the whoops and G-outs with ease!
After the reservoir was replaced, Dustin Dumas filled the shock with new oil, and then slid the shaft with its installed components in and out of the shock body to ensure that oil was pushed throughout the bypass tubes. It was then topped off with oil and everything was tightened up.
After the shocks were installed back on the car, Dustin weighed the car with his scales and made a few adjustments to the coil carriers to even-out the weight balance. All this work made a huge difference.

 A Few More "Tech" Stories...

King Shock Rebuild
Cylinder Sleeves - Saving Engine Blocks
Installing CV Boot Clamps
Engine Coolant

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When Brett Sanderson shows up to Dumont or the sand drags, he brings a double threat in the form of these two drag bikes. Wait until you see the details and workmanship on these beautiful ATVs. Nice!

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