PROTHANE FRONT BUMPSTOP WRITEUP

Darky said:
No, they will stop your axle.
Click to expand...

Maybe, depending on various factors. But I think it's a mistake to just assume they compress 60% and no further. The more you load them, the more they compress. But it's not one to one -- it's as the name implies, progressive.

But still, not an absolute hard stop. That's what the custom plastic insert is for.
 
WAM174 said:
Maybe, depending on various factors. But I think it's a mistake to just assume they compress 60% and no further. The more you load them, the more they compress. But it's not one to one -- it's as the name implies, progressive.

But still, not an absolute hard stop. That's what the custom plastic insert is for.
Click to expand...

Maybe? Wrong. They do when set up properly.

I air mine out and beat the piss out of my MJ and it takes it very well.
 
Once you compress something to a certain point, it will have no more space to compress. Compress these to the point where they have no more compression, the axle will stop. You can fine tune exactly when that stop will occur with an insert but it's not necessary to stop the axle.
 
Gonna bump this. I've got my xj with 3" and 31s and. Have zero bump stops even the factory ones were gone when I got it. I was thinking of welding a 1/4" round plate to the bottom of the top bump stop tower, (where the factory one bolted in). And then using a peice of 1" or whatever length needed 1.5" tube/pipe to "tune" the prothanes a to a deffenant stopping height.
My question comes it on what size to buy? Do I just measure from the bottom, of the bump stop tower to the spring pad? I see people leave a 2" or so air gap, why?
 
desertjr said:
Gonna bump this. I've got my xj with 3" and 31s and. Have zero bump stops even the factory ones were gone when I got it. I was thinking of welding a 1/4" round plate to the bottom of the top bump stop tower, (where the factory one bolted in). And then using a peice of 1" or whatever length needed 1.5" tube/pipe to "tune" the prothanes a to a deffenant stopping height.
My question comes it on what size to buy? Do I just measure from the bottom, of the bump stop tower to the spring pad? I see people leave a 2" or so air gap, why?
Click to expand...

You do not need to dampen all of the uptravel. Which is why some have a gap. Guessing wear and tear is less when they are not touching all the time during normal driving. I do not have them, thinking about it tho. My bumps are long enough meow, so Im good till they fall apart.
 
Perfect explanation sir. Thanks.

I'm gonna order up a set after I measure tomorrow and work with them. I saw some people drill holes through them to "soften" up the dampening rate..now would those holes be drilled top side (bump tower) or bottom side (spring pad)?
 
just because of how much they compress
 
Just have to to some math. They compress about 40%. So if you look at your remaining shock travel, then figure out how much prothane you need based on how much they compress.
 
WAM174 said:
Maybe, depending on various factors. But I think it's a mistake to just assume they compress 60% and no further. The more you load them, the more they compress. But it's not one to one -- it's as the name implies, progressive.

But still, not an absolute hard stop. That's what the custom plastic insert is for.
Click to expand...

Just wanted to clear up this old post for anyone else looking in here.

They are progressive because the more they compress, the stiffer they get, just like a progressive spring. Basically the bumps are a spring, but with no spring back. As you compress them, they get more dense and hard, meaning they slow down the axle even more than at full length. So eventually, they won't be able to compress anymore and will completely stop the axle. If you don't want to figure out what that point might be, throw a hard stop in the middle like everyone is saying.

Sure if you have a 12k lb truck, you might flatten them or whatever, but we're talking XJ's here.
 
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