Rebuilding your shocks

This article was from a 4x4 Truck website, but the rebuild process is the same nevertheless:

There are a number of reasons for rebuilding a shock absorber. Some include maintenance after a race, pre-running, loss of oil or a notable decrease in dampening. Sometimes the only way to find out what’s really going on with your shock is by taking it apart.

 CAUTION: Many shock absorbers are under high pressure, so use caution when disassembling or seek professional help.
We had a set of Bilstein 7100 Series shock absorbers sitting around that had seen a great deal of abuse, a few thousand miles and tons of off-road action. They were not holding nitrogen and even leaking oil. It was time to rebuild our shocks, so we contacted Bilstein Shock Absorbers in Poway, CA. 

Bilstein 7100 Series Off-Road shocks are one of the hottest shocks on the market for buggies, pre-runners, trucks, Jeeps and some race applications. The 7100 Series features self-adjusting deflecting disc valving, 2" diameter shock body, high-flow piston, custom valving, schrader valve and dividing piston.









THE SHOCK REBUILD

We made a call to Bilstein Shock Absorbers and were instructed to send in our shocks for an evaluation. We later got a call from Ramon in the Tech Dept. He informed us that the shocks would need new rods, seals and heim-joints because the old ones were pretty beat up.

After our discussion with Ramon, we planned a trip to the Bilstein facility near San Diego, CA. We wanted to get a behind the scenes look at their shock facility and how Bilstein 7100 Series Shocks are built. 

Once at Bilstein, we worked with 7100 Series off-road shock tech Eloi. He gave us a run down of what we would be doing to fix up our shocks to make them dirt worthy.
Bilstein off-road shocks, like the 7100 Series, can be rebuilt in your garage with minimal tools. They were designed for racing, so they are serviceable out in the field. All the rebuild parts can be purchased directly from Bilstein Shock Absorbers. They even have a step-by-step 7100 Series shock rebuild guide on their website that makes this job approachable for you DIYs.
To successfully do a shock rebuild on your Bilstein 7100s, you will need some special parts and tools. Here is the list recommended for doing a shock rebuild:

• B4-KT0-Y019A00 – rebuild kit
• 193434 – 7100 series disassembly tool
• 194570 – rod guide installation needle
• 194131 – gallon of oil

Other tools needed for a rebuild:

• Pick set
• 2 flat head screwdrivers
• Vice

Following is an overview of what is involved in putting a Bilstein 7100 Series shock absorber together.

All shocks are fully disassembled, inspected and cleaned before being rebuilt.

A good honing is done on every shock rebuild to make sure the piston traveling up and down the tube gets a good surface to work with. 

A combination of different width and thickness shims make up the valving in the shock’s valve stack. These stacks work in conjunction with the hydraulic piston that controls the up/down movement of the shaft. These are typically not replaced during a rebuild, unless you to change the valving.

 Shock Piston Assembly exploded view

 High quality heim-joints are pressed into all Bilstein off-road racing shocks. For a rebuild, they are only replaced if needed.

 Bilstein uses high-grade steel braided lines between the shock body and the reservoir. These are only replaced if needed during a rebuild.

 The Bilstein 7100 Series is charged up to 250psi using pure Nitrogen, not air or helium—funny guy.

Q&A WITH BILSTEIN’S OFF-ROAD MAN

We were able to do a little Q&A with Shane Casad, a key player in Bilstein’s Off-Road Dept. Shane is a busy man, but you’re certain to catch him at off-road events and on the trails since he is an avid off-roader.

Off-Road.com: So how often should a Bilstein 7100 Series shock be re-built (Application: Race, pre-runner, 4x4 recreational)?

Shane: If shocks are reaching an excess of 250 degrees, like during a race, they need to be rebuilt often … like after every race. If they are running constantly at less than 200 degrees, like a rally type application, they should be rebuilt once a season.

For the average recreational user, you shouldn’t need to rebuild them unless you notice they are leaking.
Recreational users should be sure to check the pressure
every year to see if there are any leaking seals.


A rebuilt shock is then tested on the Roehrig dyno before leaving Bilstein. The shock must be within spec.

Off-Road.com: What are the benefits of having your Bilstein 7100 Series shocks re-built at Bilstein vs. your buddy’s garage?

Shane: Bilstein replaces everything (all seals, all oil) and dyno tests them to make sure that they are operating at spec. Dyno testing also ensures consistent performance between sets of shocks.

Off-Road.com: Do I also need special Bilstein oil for my shocks, or can I use any hydraulic oil?

Shane: Bilstein oil is recommended to maintain the valving performance as it was designed.

Off-Road.com: If Ijust want to get my shocks re-built at Bilstein, how can I get this done?

Shane: Download the “Repair Order Instruction Sheet” from the website to fill out and send in with the shocks.

Off-Road.com: Anything else you would like to add?
Shane: If you are rebuilding yourself, make sure to release the gas pressure prior to taking the shocks apart. Check the condition of the piston rod, because any nicks or other damage will tear seals. Be sure to inspect the heim joints to see if they need replacing. You also will need nitrogen, which can be purchased from welding supply companies. Poly Performance and Rubicon Express also sell convenient fill kits.
There you have it folks. Whatever you do, don’t shoot your eye out. Make sure to release the nitrogen before you crack open a shock. Better yet, why don’t you just leave it to the pros. We did, and they worked out great on our project Ford F350. The choice is yours.

The benefit to sending them into Bilstein is that they have all the parts necessary to do a complete rebuild. They also have a shock dyno that is used for testing them before they come back to you. The rebound/compression is measured on every shock.

For more information on Bilstein Shocks Absorbers or rebuilding your Bilstein shocks, please visit http://www.bilsteinus.com/services.php

 

Bilstein Shock Absorbers
http://www.bilstein.com

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