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Unread 01-08-2011, 04:08 PM   #1
chmo
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Prothane progressive coil spring inserts write up

progressive bumpstops or "poor man's speed bumps"

(EDIT: 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 : http://www.jeepforum.com/forum/f9/pr...l#post14416663 )

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.

needed_01.jpg


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)

needed_02.jpg


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.

Front:
front.jpg


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...
Rear:
rear.jpg

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) :
dune_tj_03.jpg

mine is the one in the middle (midnight blue)
in the background MOUNTAINS of nice sugar sand ... sand surfers paradise

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Unread 01-08-2011, 04:28 PM   #2
Jerry Bransford
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Nice idea and a very nice writeup. And that sure is a lot of sand, totally different the type of deserts I wheel in. Heck dunes like that would kinda scare me, I'd be afraid of who's coming at me from the blind side of one of them. We have a similar area full of huge sand dunes fairly close to me called Glamis and there are lots of serious accidents out there from wheelers and motorcyclists running into each other virtually every weekend during the cooler wheeling season.
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Unread 01-08-2011, 04:49 PM   #3
chmo
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yup ... scary ... high altitudes and steep angles with low traction ... but not too risky (except driving mistakes in off camber situations and on steep slip faces )

Last edited by chmo; 01-10-2011 at 01:06 AM.. Reason: offtopic somehow
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Unread 02-05-2011, 03:31 PM   #4
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Nice writeup! A few questions:

Quote:
Originally Posted by chmo View Post
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 (only upper cover needed)
1. I assume the "piece of metal tube" is pretty short? It seems like if it were more than an inch it would interfere with compression (see max compression question below). Have you had any problems with it working loose as the foam expands and contracts?

Quote:
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
2. I'm not clear what you mean here - are you saying they compress up to 70%? I.E. 3.5" compresses down to 1", so the inserts are equivalent to a 1" bump stop extension?

Quote:
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.

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...
Rear:
Attachment 178253
3. How did you zip tie the A/C pipe insulation to stay in place? How is this holding up?
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Unread 03-24-2011, 06:19 PM   #5
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any more info you can give us on this Chmo? i'd also like to hear the questions above answered. i have been looking into doing these on my rig as well.
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Unread 03-26-2011, 05:51 AM   #6
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Quote:
Originally Posted by Sarge_ View Post
Nice writeup! A few questions:



1. I assume the "piece of metal tube" is pretty short? It seems like if it were more than an inch it would interfere with compression (see max compression question below). Have you had any problems with it working loose as the foam expands and contracts?



2. I'm not clear what you mean here - are you saying they compress up to 70%? I.E. 3.5" compresses down to 1", so the inserts are equivalent to a 1" bump stop extension?



3. How did you zip tie the A/C pipe insulation to stay in place? How is this holding up?
re1.) Yes the welded on piece is in my case about an inch long ... just to be on the safe side keeping enough distance to the pad under full compression.

re2.) no NOT 70 % compression ... 60-70 % of original size after compression means 30-40% compression (if you do not remove material by drilling holes) so : 3 rings=3.5" ... compress down to 2-2.5" size ... I HAVE 1.5" equivalent because I removed the UPPER jounce bumpers PLUS JOUNCE BUMPER CAPS and put the acos rubber end bump stops which I had lying around. So the top is basically the BS tower plus a bit compressed rubber.

re3.) initially I put a long enough zip tie INSIDE the A/C pipe insulation and pulled just enough to close the ring ... cut the rest off. it might leave a small gap where the pipe is cut ... depending on your "creativity" when cutting the pipe and the softness of the foam pipe ... not critical. And the latest foam pipes are holding up well !!! (before I did the write up I had some very soft stuff (got torn) which I replaced with the stuff you see in the pics ... and thats OK!)

and sorry for the late reply ... i missed the "auto notification" mail somehow
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Unread 03-26-2011, 06:14 AM   #7
chmo
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latest findings after like 10 trips with them :

the front: Great !!! exactly working like they supposed to ...

the rear: some "fine tuning" of the foam pipe was (and still is) necessary ... first the foam pipes were being pushed up by the spring passes under decompression in such a way that the inserts were misaligned. Then after tightening the upper foam pipes up a bit (with external zip ties) I find my inserts always up side down ... the metal cap is resting on the spring pad.
Fix : the 3 rings are 3.5" long ... short enough to be able to perform a full turn inside the springs ... maybe making them 3.5 rings long and adding just ONE more foam pipe will do the trick.
And it has something to do with the weight of cap ... the inserts are now heavy headed. So another fix would be to make the lower part heavier to keep them from rotating. Still fiddling around!!

BUT I NEVER BOTTOMED OUT MY REAR again. No clunks from the TB hitting the gas tank skid and no TB relocation bracket hitting the tub any more
No hard bum stops and NO abrupt "rebounds" anymore ...

I have a spare 10" insert ... just for the case I destroy my rear inserts before figuring out a more stable "floating" installation.

One more thing : make sure the metal pipe piece fits REAL snug into the opening of the inserts ... maybe some additional layer of tape to make them thicker!? Epoxy was useless after pushing the setup hard ... and one of the caps got lost (of course I had a spare one )
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Unread 03-26-2011, 07:15 AM   #8
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Thanks for the update! I've been debating between these or terra flex speed bumps. Since these look real easy to instal, I may just give these a try in the front and see how I like them if they're cheap enough. I def need to do something in the rear eventually since I have the same issue with the tb bracket smacking the tub. Thanks again for the write up!
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Unread 03-26-2011, 07:26 AM   #9
chmo
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One set (2 inserts with 8 rings each) :
http://www.jegs.com/i/Prothane/311/19-1705/10002/-1
$ 63.99 ships on monday

was enough for me ...

Just to have spare and to justify the shipping to the UAE I ordered TWO sets

(and you are welcome )
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Unread 03-26-2011, 07:38 AM   #10
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Definitely worth a try at that price! thanks chmo!
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Unread 03-27-2011, 01:51 PM   #11
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I still dont get how you get them in the rear springs. did you have to bend the spring to make the side coil gap wider???
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Unread 03-27-2011, 02:13 PM   #12
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i was thinking about how to stabilize the insert in the rear. it seems the best approach would be to forget the cap on top but instead flip the whole insert/cap assembly upside down and weld the cap to the lower coil bucket. essentially you'll have the insert impaled on a stick and glued on. lol
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Unread 03-27-2011, 04:18 PM   #13
chmo
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Quote:
Originally Posted by TJdualsport View Post
I still dont get how you get them in the rear springs. did you have to bend the spring to make the side coil gap wider???
was not necessary.
with the spring unmounted lying on the ground I squeezed the coil inserts of course without any foam pipe zip tie art between the passes ring side by ring side.
some grease on the inserts and some elbow grease and strong thumbs helped a lot

The prothane coil spring inserts are quite flexible!!! (softer than many hard rubber bump stops)
If you drop the uncut 10" insert vertically on the floor you will be surprised how high it will rebound
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Unread 03-27-2011, 04:24 PM   #14
chmo
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Quote:
Originally Posted by mxtrails View Post
i was thinking about how to stabilize the insert in the rear. it seems the best approach would be to forget the cap on top but instead flip the whole insert/cap assembly upside down and weld the cap to the lower coil bucket. essentially you'll have the insert impaled on a stick and glued on. lol
yup ... one guy on NAXJA welded the piece of tube directly to the pad, another guy drilled the pad and fixed the cap with a screw to the pad ...

but I seriously doubt, that the insert will stay on that 1" tube even if glued.
the impact from the upper tower will loosen any glue ... and the inserts are flexible.

the floating install really makes sense!
only the tilting/tumbling problem and the opening problem have to be solved.
will do some experiments and post results ... but right now I am busy breaking my new 4.88 gears in
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Unread 04-04-2011, 05:08 PM   #15
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just got my set of prothanes from jegs today does anyone know how/where the jeepspeed guys drill these to give them more travel/softer hit?
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