Too long piston rod in the shock absorber?

[linuslarsson]

Hi,

I´m about to replace front suspension spring and shock absorber on my Berlingo Family 1.6 year 2004. When I compare the new shock absorber with the old one the piston rod in the new absorber is 3 centimeters longer. Everything is exactly the same except for the piston rod length. I have talked with Citroen and also other repair shops but no one can give me an answer of how long the shock absorber should be. The old one is approx 35,5 cm and the new one is approx 38,5 cm. 

I have two questions that I´m hoping you could help me with.

#1: Is it possible that I have the correct part even though the piston rod is longer?
#2: What difference would it make if I mount the longer shock absorber? I´m thinking the car ride height possibly would increase after passing a bump and the shock absorber gets the full length. Or am I wrong here? Maybe the shock absorber never fully extend even after a big bump?

[oilyrag]

The only time the shock extends fully is when the tyre is off of the ground, but there is resistance in the wishbone assembly that would stop it doing so. Ride height will not change as that is governed by the spring, not the shock absorber - I can't see any issue in using the shock you have.
If you aren't planning rallying with the wheels off of the ground for long periods it will be fine!

[linuslarsson]

The only time the shock extends fully is when the tyre is off of the ground, but there is resistance in the wishbone assembly that would stop it doing so. Ride height will not change as that is governed by the spring,  not the shock absorber - I can't see any issue in using the shock you have.
If you aren't planning rallying with the wheels off of the ground for long periods it will be fine!

Thank you for your answer! I will mount the new parts tomorrow and also try to continue to keep the wheels on the ground in the future 

[jj9]

What about when the shocker is compressed though, it won't have as much travel before it bottoms out.


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[oilyrag]

The piston rod never goes fully into the shock body as the spring, bump stop & mount take up a proportion of its length? The strut rod itself doesn't bottom out under spring compression, it is the bump stop/spring resistance/coil binding that controls this.
As a test, with the new shock standing upright it is possible to steadily push the rod into the shock well beyond where it could normally get to if the spring were completely compressed under load, showing that there is 'clearance' between the rod and the bottom of the strut itself when the unit is assembled and in situ.
(Always keep the shock upright when pulling the rod in/out.)

[jj9]

The piston rod never goes fully into the shock body as the spring, bump stop & mount take up a proportion of its length? The strut rod itself doesn't bottom out under spring compression, it is the bump stop/spring resistance/coil binding that controls this.

I appreciate that, but as the rod will be 30mm further into the body of the shocker it will have 30mm less compression travel, this could be an issue as it could bottom out.

As a test, with the new shock standing upright it is possible to steadily push the rod into the shock well beyond where it could normally get to if the spring were completely compressed under load, showing that there is 'clearance' between the rod and the bottom of the strut itself when the unit is assembled and in situ.
(Always keep the shock upright when pulling the rod in/out.)

Yes, that would would be a wise check, but it's a lot easier said than done, realistically you can only estimate how far the rod goes into the shocker when the spring is completely compressed.

Although the shocker may be fine, I think I would want double check that it is the correct shocker for the vehicle.


Look up your vehicle and find the Citroen part number of the shocker and cross reference the part.

https://www.catcar.info/citroen/?lang=en



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