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ACOS PROs (“thump/crunch” sound?)

A

austinXJ

NAXJA Forum User
Location
Austin Texas
I recently had installed a set of ACOS PRO hydraulic bump stops on a 2001 Jeep XJ. Minimal lift setting – total lift about 2.25 inches with OME springs in back. Austin Jeep Masters did the work.

The issue is a distinctive “thump/crunch” sound when the ACOS shock/bump stops strike the base plates. Is this sound normal?!

I have searched the NAXJA forums and this issue/question has not been presented.

Many thanks for any information provided.
 
Air bumps on metal are noisy. Especially if you have a decent amount of pressure with not a whole lot of free travel before the bump. You'll be on them a lot in that case.

When I put mine together I used a block of UHMW-PE to keep the noise & friction down. It works, but you can still feel the bump engage.

n24800499_33134868_1675.jpg
 
Thanks for the note! The sound *really* transmits through the XJ’s unibody.

Is adding a or puck of UHMW-PE or equivalent worth the effort to help reduce “thump/crunch” sound when the ACOS shock/bump stops strike the base plates? Anyway to add/secure the puck without removing the springs - or will the puck of UHMW-PE stay in place when slid between the spring to rest on the stike plates?

Many thanks again for sharing your experience.
 
austinXJ said:
Thanks for the note! The sound *really* transmits through the XJ’s unibody.

Is adding a or puck of UHMW-PE or equivalent worth the effort to help reduce “thump/crunch” sound when the ACOS shock/bump stops strike the base plates? Anyway to add/secure the puck without removing the springs - or will the puck of UHMW-PE stay in place when slid between the spring to rest on the stike plates?

Many thanks again for sharing your experience.
Click to expand...
you will have to pull the springs and secure it using a nut and bolt. dont leave it loose in there
 
You don't want a bolt head poking up - that eliminates the entire point.

I doubt you have as much room as I did, but here's how I secured the UHMW blocks:

n24800499_33128532_8751.jpg


Drilled and tapped a hole halfway through the block and threaded a stud in place.

It definitely quiets them down a lot, but I dunno how easily you'd be able to implement it on your setup.
 
vetteboy said:
You don't want a bolt head poking up - that eliminates the entire point.

I doubt you have as much room as I did, but here's how I secured the UHMW blocks:

n24800499_33128532_8751.jpg


Drilled and tapped a hole halfway through the block and threaded a stud in place.

It definitely quiets them down a lot, but I dunno how easily you'd be able to implement it on your setup.
Click to expand...
that is pretty smooth. i was thinking more of a counter sunk hole or some thing but that is much cleaner
 
crazyjim said:
Use 2 or 3" RE bump pads, they're like $40 or so.
Click to expand...
i run the standard acos and i made an adjustable lower with a 1/2 inch threaded bolt and a 1/4 inch thick 3 inch round pad it works good but i am not metal to metal. i may switch over to that though once i figure out the ride and height i want here is my current set up works good so far
6401801b.jpg

nothing fancy
 
If sound is a big concern you could do vetteboy's idea but add a rubber gasket below the UHMW pucks. The rubber and UHMW setup would probably be about the quietest it could get.
 
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