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Old 04-16-2013, 07:22 PM   #1
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Adjusting bumpstops w/ pics

4.75" lift and 315/75R16 on Moab rims, no spacers.

Pulled the springs, disconnected sway bar and put wheel back on. With frame sitting on jack stand I jacked the axle up into the wheel well looking for contact.


In the above picture you can see the tire first contacts the rear portion of the fender and inner wheel well.

I plan to add 3.5" of bump stop. What you don't see is I added .75" spacer when I put the spring back in. This will leave me with ~5.5" of space for coil bind, questions I have are:
1. Does anyone know coil bind length for a rough country 4" lift spring?
2. Does this type of jounce bumper completely crush? Should I add less than 3.5"?
3. Should I add all bump stop to jounce bumper or split between bottom and top? Worried a 3.5" extension on jounce bumper will break since the contact is not straight on.
4. If I replace my jounce bumpers with these urethane daystar ones, what amount of crush should I consider? 50%?

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Old 04-16-2013, 07:26 PM   #2
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Those won't crush. You don't want them. The way the Zone kit I have did it is add a spacer above the cups, retaining the stock cup and jounce. I have heard to add to the bottom, but never really saw how. UnlimitedLJ is a good one to ask about this, maybe shoot him a PM with a link over here.

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Old 04-17-2013, 06:35 AM   #3
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Originally Posted by GoldenSahara00 View Post
Those won't crush. You don't want them. The way the Zone kit I have did it is add a spacer above the cups, retaining the stock cup and jounce. I have heard to add to the bottom, but never really saw how. UnlimitedLJ is a good one to ask about this, maybe shoot him a PM with a link over here.
Too add to the bottom you drill and tap the lower spring perch and bolt the extension down through the center.
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Old 04-17-2013, 08:02 AM   #4
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Make your own extensions. Drill, drill bit, a couple bolts for as long as you need it, a few washers, a couple nuts, and some hockey pucks. Works great.
Just gotta get creative.
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Old 04-17-2013, 08:12 AM   #5
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Quote:
Originally Posted by HobieSailor View Post
I plan to add 3.5" of bump stop. What you don't see is I added .75" spacer when I put the spring back in. This will leave me with ~5.5" of space for coil bind, questions I have are:
also notice your shocks are fully compressed at this point due to the mount relocators. your tire clearance is the last of your worries. right now, you do need 3.5" bumpstop extension to keep the shocks from bottoming out and keep the shock mounts from ripping off.

Quote:
Originally Posted by HobieSailor View Post
1. Does anyone know coil bind length for a rough country 4" lift spring?
I doubt it. You'd have to figure that out yourself most likely. That means putting the spring into a press and compressing it completely. IMHO, not worth the effort unless you do have a shop press easily accessible. Just assume it's fine as long as you're not using spacers, and you run the currently required 3.5" bumpstop extension.
Quote:
Originally Posted by HobieSailor View Post
2. Does this type of jounce bumper completely crush? Should I add less than 3.5"?
the stock one will, the hard poly jounce bumper you posted a picture of is a whole different ball game you don't want to play.

Quote:
Originally Posted by HobieSailor View Post
3. Should I add all bump stop to jounce bumper or split between bottom and top? Worried a 3.5" extension on jounce bumper will break since the contact is not straight on.
for that much bumpstop extension, add it to the bottom and the top. you'll need to check full bump again to ensure bumpstop alignment.

you may also want to check out Currie's rear bumpstop setup, which replaces the stock stuff, and incorporates spring retainers. it's a PITA to setup, but once it's done it's pretty nice.

Quote:
Originally Posted by HobieSailor View Post
4. If I replace my jounce bumpers with these urethane daystar ones, what amount of crush should I consider? 50%?
don't do that. here's why- stock microcellular poly jounce bumper vs hard poly jounce bumper.

additionally, while you're pushing the axle around, make sure to check full bump (both sides fully compressed) and watch track bar vs frame clearance and diff vs gas tank clearance. you may consider trimming the wheelwell for tire clearance. you may also find the only way to get this to work is to pull the axle forward a bit with adjustable upper and lower control arms. you want the bumpstops centered at full bump, with the extension installed

btw, good work so far.
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Old 04-17-2013, 07:03 PM   #6
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Originally Posted by UnlimitedLJ04 View Post
also notice your shocks are fully compressed at this point due to the mount relocators. your tire clearance is the last of your worries. right now, you do need 3.5" bumpstop extension to keep the shocks from bottoming out and keep the shock mounts from ripping off.
I didn't mention it in my post but before I checked for tire clearance I did check the shock alone. I came up with the same 3.5" extension, being figuring the shock's external jounce bumper could crush about 25%.


Quote:
Originally Posted by UnlimitedLJ04 View Post
you may also want to check out Currie's rear bumpstop setup, which replaces the stock stuff, and incorporates spring retainers. it's a PITA to setup, but once it's done it's pretty nice.
I ordered some PA nylon round body lift blocks, I'll be piecing something together that is similar to the currie setup but without the spring retainer.


Quote:
Originally Posted by UnlimitedLJ04 View Post
I've done some urethane bushing kits before and knew it was pretty hard stuff. Good info in that thread, thanks.



Lastly, when I go to add the +4" of bumpstop to the front should it all be on the lower pad? As it is now the upper cup gets pretty hung up on the spring.

Thanks
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Old 04-17-2013, 07:20 PM   #7
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Originally Posted by HobieSailor View Post
Lastly, when I go to add the +4" of bumpstop to the front should it all be on the lower pad? As it is now the upper cup gets pretty hung up on the spring.
correct, add it all to the lower end. otherwise it sounds like you got it figured out for the most part. Also, if you can find the proper large OD grade 8 thick fender washer w/ the proper bolt ID, you can use that as a spring retainer if proper positioned in the rear...i think they have them on McMaster-Carr. When I redo my rear shock mounts & bumpstop extensions, I'll probably do that myself.
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Old 04-17-2013, 07:22 PM   #8
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Lastly, when I go to add the +4" of bumpstop to the front should it all be on the lower pad? As it is now the upper cup gets pretty hung up on the spring.
Yes.

Whoops, too slow.
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Old 04-17-2013, 07:38 PM   #9
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Originally Posted by UnlimitedLJ04 View Post

correct, add it all to the lower end. otherwise it sounds like you got it figured out for the most part. Also, if you can find the proper large OD grade 8 thick fender washer w/ the proper bolt ID, you can use that as a spring retainer if proper positioned in the rear...i think they have them on McMaster-Carr. When I redo my rear shock mounts & bumpstop extensions, I'll probably do that myself.
Cool, thanks. I also though about using a large washer to mimic the currie setup but didn't think spring retention was much of a problem in the rear, at least not with stock sway bar always connected.
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Old 04-17-2013, 07:43 PM   #10
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Cool, thanks. I also though about using a large washer to mimic the currie setup but didn't think spring retention was much of a problem in the rear, at least not with stock sway bar always connected.
the sway bar will not limit downtravel, as long as you install the required longer links in the rear for a lift. the shocks length will be the limiting factor, unless you have limit straps.

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