progressive bumpstops or "poor man's speed bumps"
for the full story and all contributions/experiments/mounting options read on ...
for the fast forward to my personal actual mounting hardware and status Revision 2
For our dune bashing here in the UAE I was looking to add some speed bumps to my suspension. During my research I stumbled over a thread on NAXJA where some guys successfully used prothane coil spring inserts to avoid hard bump stopping.
My OME HD springs were still too soft in the rear where going fast through ditches was causing annoying kicks of the rear ...
As I was going to add some bumpstops for my coming 33" tires I decided to give the prothanes a try. I ordered a set of 2 x 10" inserts from jegs to be cut down as needed ... see below.
The prothane instructions were recommending FLOATING (loose) install.
To protect the inserts from the upper BS towers or cups I decided to fabricate some covers ... (4 needed)
A 3" thick washer and a 1.5" piece of metal tube (38mm diam) welded together and sprayed with black barbecue rustproof will do
Just as a precaution I epoxied the snug fitting covers with marine epoxy to the prothanes (only upper cover needed)
My actual 31" do not need BS extensions in the front with my N66 ... but in the rear I need 1.25" BS extension to protect my shocks (N67), tub (TB rel bracket) and spring from over compression (yes I have added 0.4" spacer)
33" tires would need 2" bumpstop extensions to avoid fender contact.
With a 1.25" BL (coming
) 1"-1.5" would be enough.
prothanes compress to 60-70% of original size ... so 3 rings (3.5") would compress to 2-2.5" ... to come down to around 1.5" BS extension I replaced the upper jounce bumper cups with some ACOS hard rubber bump stops I had lying around.
You can cut the PU micro cell foam coil spring inserts with a sharp knife to 3 rings.
For the rear I had to be a bit creative, as floating installation inside the rear springs would leave to much room for the inserts to tilt freely around.
The inserts (3.5" diam.) do NOT slide into the rear springs from top or bottom. So some lube and force and I was able to squeeze the rear inserts between the spring passes ring by ring. (unmounted springs!)
To limit the "degree of freedom" of the inserts I needed to increase the outer diameter with some flexible stuff which would not interfere with the springs.
Some creativity with AC pipe insulation tube (foam rubber) and some zip ties later...
RESULT : AWESOME ... During the Abu Dhabi Desert challenge where our club was taking care of some transportation for the press the rear of my heavy loaded TJ was not kicking anymore and my stuff (water and fuel cans) stayed where it supposed to be
Speeding through the big and small (mean) dunes did not cause any hard bump stopping or TB rel bracket hitting tub or rear TB contacting gas tank skid.
Speeding over flat sandy "sabkhas" (dried mud valleys) was possible with more than 60mph !!!
It was like having "endlessly progressive" coils in the front and rear!
You can "fine tune" the inserts by drilling some holes which will allow them to compress softer (and further) ... I did NOT do it, since I needed the extended bump stop dimensions and the softness was ok for me!
Maybe one more thing : I do not like to jump
like the inspirers on NAXJA ... I cannot afford a breakdown in the middle of the empty quarter desert 50 miles from the next road
... my driving style is more like "melted cheese on toast"
and here was the test area (our favorite wheeling ground)
mine is the one in the middle (midnight blue)
in the background MOUNTAINS of nice sugar sand ... sand surfers paradise