Factory Five Technical Alert

Shock Absorber Breakage Report and Summary

Background:

We have recently received reports from customers that detail breakage of their Bilstein brand shock absorbers.  As soon as we began receiving these reports we started working on understanding what was happening.  The actual number of cases reported to us have been small (less than one half of one percent) however the consequences of failure of this part can be serious and we have been working as quickly as possible to investigate these reports fully and understand their causes so we can communicate accurately to you, our customer, and let you know what to do.

We have worked with Bilstein, and Bilstein Germany, and have studied returned parts from three customers.  We have also looked at older shock suppliers (Pro-Shocks, QA1, and Carrera) and historic reports.  As of March 29, 2006, we are confident that we have determined the probable causes and have developed a good plan of action.  We are posting this letter on our website and sending hard copies via first class mail to affected customers.

Summary: 

While some of the reports we have received involve issues unrelated to breakage, normal wear and tear (shocks are a wear part and will go bad over time) does diminish a shock absorber performance.  The primary concern is any report of breakage.  Based on examination of returned parts we feel that the shock failures involve three specific factors. 

1.      Some cases were due to improperly seated springs and spring hats. One way this could occur is when jacking the car and lowering it without having the spring hats zip-tied to the springs

2.      The second cause of failures were due to interference with a rigid part, resulting in binding and side loads placed on the shock that the part was not designed to withstand. 

3.      The third cause of failures involves a small number of 1⅞” diameter 450lb and 500lb springs that were manufactured using a thicker wire diameter which reduced the amount of available spring travel.  These springs are usable in all but two applications.  Using these springs on the Independent Rear Suspension could potentially bottom out the suspension prematurely and improperly.  We have only seen one case in which this has happened.  There is also potential for this to occur in the front suspension if a tall spacer is placed between the spring hat and jam nut when either of the thicker wire 1⅞” springs are used in combination with first generation FFR control arms or some aftermarket control arms.  If you think that you have this front suspension combination or, an Independent Rear Suspension kit from FFR between January 2004 and March 2006 please follow the attached shock inspection procedure to determine if you have the larger wire diameter springs.

Bilstein engineers feel that there could also be a chance that the interface between the jam nut and the spring hat could be re-enforced to prevent any potential side loads. Our engineers do not fully agree with this but the solution of adding a grade 8, ⁷/₁₆” washer prevents the chance of this from being a contributing factor. We are forwarding these parts to all affected customers. The size and specification of the washers are included in the attached procedure if you would rather not wait for us to mail them to you.

Here is what you must do:

Step 1:             Stop driving your car.

Step 2:             Inspect your suspension and parts for damage, signs of wear, or interference.  Verify that you have assembled your suspension parts correctly and you do not have a mismatched combination of parts. The engineers at FFR have written and attached a detailed inspection procedure for you to follow.

Step 3:             If damage is found with any shock, spring hat, threaded sleeve or spring seat, it must be replaced. If a mismatched combination of parts is found, the correct parts must be installed. Contact Factory Five immediately for assistance.

Step 4:             If you have any questions whatsoever or if parts of this letter are not clear, please contact Factory Five Racing and ask for an engineer.  We will be happy to go thru this with you in person or over the phone.

A Note from David Smith, Factory Five Racing President:

This is a serious problem that deserves serious attention, but I want all of you to keep something in mind. All our guys drive Factory Fives. Many of the people that I love the very most in the world drive and race our chassis kits. There are remarkablely tough and safe cars. Since 1995, we have shipped over 12,000 shock Absorbers and delivered over 5,000 Factory Five kits.  We have tens of thousands of racing miles in competitive, wheel-to-wheel racing events, and collectively millions of miles experience with FFR customers. We have steadfastly committed ourselves to building the strongest and safest parts and your safety is our first and most important job. The number of variables involved in building your own car is mind boggling but I can promise you there is no company anywhere today that cares more about safety and our customers than the amazing crew here at Factory Five. Check your cars, drive safely, and know you can always count on us here.

• Click here for procedure.