Measuring to Determine the Right Size Shock to Use on a Trailer

Updated 05/29/2025 | Published 03/17/2016

Question:

Please advise which Lippert shocks I need. My trailer measures 11.5inch from bracket to bracket parked unladen. Thank you.

asked by: Charlie

Expert Reply:

If you are looking to add shocks then measure using the following procedure: Compress the shock all the way (A) then mark the inner leg where the outer leg stops. Then release compression and measure the stroke (how far the shock moves) (B). Then measure the half way point of the stroke (C). Then you measure the shock length with it compressed to the half way point (Fig. 4A). The measurement cannot exceed the fully extended or compressed lengths.

Add 2 inches to that last measurement. Make a measurement perpendicular to the shock mounting lip on the tie plate that is the same distance and make a mark on the I-beam parallel to the shock mounting lip on the tie plate. The shock should be up to a 45 degree angle but no more as shown in the picture for the Lippert kits.

If you are replacing a shock then the shocks you have may have a part number on them. If not let me know the diameter of the trailer axle and/or its capacity.

expert reply by: Michael H

click to enlarge

Ron B.

5/26/2025

Hi Michael, I have a boat trailer and 16ft boat that weighs 1500lbs total. The single axle is rated 2000lb and leaf springs are rated 750lb each. The boat weighs about 750lbs with 275lb Mercury motor. I would like to add shocks to the trailer, but don't know what capacity shock (Lippert #283271). I would have to fabricate mounts. The problem is going over road impressions causing a loud thump or thud. I thought shocks would alleviate the noise. What is your suggestion? Regards, Ron Beck

Jameson C.

5/27/2025

@RonB The shock you mentioned is for 3,500 lb axles so it would have too stiff of dampening to work well on a trailer as light as yours. Is the thud from bottom out the suspension? If we know what the sound is maybe we can come up with a different solution.

Ron B.

5/28/2025

@JamesonC When going over an impression in the asphalt road (where two sections of paved asphalt meet and eventually form a wide crack 1/2"-1") the thud appears after the tire comes out of the road impression. Mind boggling. Been fighting this for years. The tires are Carlisle 145R12C grade D 65psi.