Warning: Eibach PRO-TRUCK Sport Strut

[Ac3]

Hi all,

 

This is a friendly warning regarding Eibach's PRO-TRUCK Sport Shock for the 2019+ Silverado 1500's (Part #: E60-23-032-01-10). In short, it increases suspension travel by ~3" which binds the upper ball joint.

 

I had previously used Eibach's PRO-TRUCK line of shocks on a 2016 Colorado as a Bilstein 5100 alternative when looking to get rid of the stock rake. Eibach's product gains lift the same way as Bilstein by using an adjustable c-clip to increasing pre-load with the benefit of firmer valving. While Eibach's installation instructions are lacking compared to Bilstein, the Eibach struts performed well and I didn't have any issues .

 

Today, I finished installing the Eibach onto my 2024, Silverado LT, Z71 which was straight forward. However, I've come to conclude the product could be dangerous by increasing travel by ~3", exceeding the safe angle of the upper ball joint at full extension. My findings were:

• The maximum extension of the stock Rancho strut was 19 5/8". This was measured from the lower mounting bracket to the bottom of the threads on the strut shaft as this is where the upper mount sits - first photo/ #9669
• The maximum extension of the Eibach strut was 22 5/8" when measured in the same manner - second photo/ 9675.
• For a comparison between the stock Rancho and Eibach strut, look at third photo/ 9669.

 

I've gathered from posts such as this one and this one, increasing the travel length more that 2" puts the upper ball joint past it's maximum angle. Eibach's design of increasing travel by 3" is the equivalent of installing a 3" spacer onto of the stock Rancho strut, stressing the stock upper ball joint at full extension. Nowhere on Eibach's product page or instructions does it indicate this product needs aftermarket upper control arms to be safe or that the travel length was increased by 3" over stock.

 

In light of this, I've ordered the Bilstein 5100 to replace the Eibach's (PN: 24-293297). The data sheet shows the strut has a full extension length of 21.65". Since I do not have the strut yet, I do not know if this measurement includes the threads on the shaft or if this is to base where the upper mount sits. Regardless, this means Bilstein's strut is either the same length as the stock Ranch strut or, introduces 2" of suspension travel which falls within the ability of the stock UCA's.

 

By no means do I claim to be an expert as I am new to the T1XX platform, but these principles were well documented when I owned a GMT360 and GMT 31XX. 'In strut' lifts are considered safe since you do not increase the maximum extension of the strut, meaning you do not increase the maximum angle of the upper ball joint. 'In strut' lifts increase the preload to gain lift. 'Outside strut' lifts are easier to install but become dangerous at a point since it will increase the maximum extension to a point where the upper ball joint becomes the downward limiting factor. After repeated instances of this, the upper ball joint can fail by sheering or popping out of the socket.

 

I welcome any and all questions, comments, or feedback as I learn the T1XX platform.

 

Kind regards,

Ac3 (Ace)

 

 

 

Edited July 8, 2024 by Ac3

[GETGONE]

Why not just get aftermarket upper control arms? They are a known weak point. Apparently enough so that with the introduction of the ZR2 they changed the upper control arms on them and the same part number is used on the Trail Bosses. Any lift beyond the 2" stock height should include new upper arms with corrected ball joint angles.

[Ac3]

Great point.

 

In my personal experience, I find aftermarket bushing don't last as long in comparison to the sealed OEM's. My use case is mild - my vehicle is 80% pavement with the other 20% being my father's farm or forest service roads. Rarely am I doing serious off-roading and when so, rarely at speed.

 

The Bilstein 5100's came in today and the travel is only a 2" longer compared to the stock Ranchos, 1" shorter than the Eibachs. Based on the historical OEM Trail Boss UCA PN and the general online concessions, I should be okay with this setup.

 

Cheers,

Ac3 (Ace)

[asilverblazer]

On 7/7/2024 at 8:27 PM, Ac3 said:

...Eibach's product gains lift the same way as Bilstein by using an adjustable c-clip to increasing pre-load...

...'In strut' lifts are considered safe since you do not increase the maximum extension of the strut, meaning you do not increase the maximum angle of the upper ball joint. 'In strut' lifts increase the preload to gain lift. 'Outside strut' lifts are easier to install but become dangerous at a point since it will increase the maximum extension to a point where the upper ball joint becomes the downward limiting factor. After repeated instances of this, the upper ball joint can fail by sheering or popping out of the socket.

None of these lift styles increase or change the amount of "pre-load" on the springs. You can verify this by measuring the height of the spring with and without the lift installed, assuming you reuse the same spring.

 

There are only two ways with these lifts to increase spring pre-load:

One, you put so much "lift" into the system that the strut assembly and/or spacers pushes the upper control arm so far down that it is forced against the droop limit stop at all times. 

 

Two, a poorly engineered strut, where the strut piston is not long enough or able to extend out enough to make up for the higher spring perch location via the c-clips. 

 

These styles of lift work by moving the two strut mounting points further away from each other, via spacers at the top of the assembly or bottom, what you seem to refer to as 'outside strut' lifts. The 'inside strut' lifts are doing the exact same thing by moving the bottom spring perch up and down on the lower strut shaft.

 

Regardless, your warning about upper control arms and ball joints is well merited.

Edited July 10, 2024 by asilverblazer