Lower bumpstop travel

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Boduke

Boduke

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72 dart running 6cyl torsion bars with 318.. i have the ride height set at 1-3/4 between the lca and the fram. My rock auto bumpstop is 1-3/8. Leaving me 3/8” of travel.. i may have set the ride height low but i like it where it is. Question.. how much should i cut the rubber bumper ? Or how much space does most everyone run between top of rubber bumper to frame..set for grandma driving to church specs..
thanks

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Depending on what your doing, I’d get lager T bars… Cutting that much rubber off is getting really close the the encased metal of the bump stop.
 
So i just ran outsode and butchered them with hacksaw. I think im prob going back to no lower bumpstops. I ran none for years without issue. Def not correct. Def not adviseable.
 
I use to ride low for a 100K. Miles no rubber left when I restore it 4 years ago. Now it sits higher. It did corner much better though.
 
the shape of the bump stop is part of the suspension geometry. The shape helps slow the collusion between the lower control arm and the body. My car sits with about 1/2 inch between tip of the rubber and the body
 
I cut mine down by about an inch, then I drilled a hole in it to make it a bit more progressive if I did make contact, kind of like this:
1718814787900.png


PRO TIP: put the bump stop in the freezer overnight before attempting to cut it. I used a coping saw to cut it and a regular drill bit. you may have to re-freeze after each step to stiffen it back up.
 
Boduke said:
72 dart running 6cyl torsion bars with 318.. i have the ride height set at 1-3/4 between the lca and the fram. My rock auto bumpstop is 1-3/8. Leaving me 3/8” of travel.. i may have set the ride height low but i like it where it is. Question.. how much should i cut the rubber bumper ? Or how much space does most everyone run between top of rubber bumper to frame..set for grandma driving to church specs..
thanks

View attachment 1716264067

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Good grief.

If you like the ride height where it's at, you have one choice to do this correctly - buy significantly larger torsion bars. You could also buy 2" drop spindles if you insist on keeping the inadequate torsion bars, but you'd just be trading one set of problems for another.

With /6 bars you will need every bit of that bump stop, because you will be constantly using it. Even at factory ride height you'd be using it, and you're much lower than that. Removing the bump stop to gain back travel is a terrible idea in this case, because you still won't have nearly enough travel to keep the LCA from bottoming out on the frame. Running without bump stops is never really a good idea, but with substantially less travel available than what the car will use with those torsion bars it's a really poor decision for this application.
 
72bluNblu said:
Good grief.

If you like the ride height where it's at, you have one choice to do this correctly - buy significantly larger torsion bars. You could also buy 2" drop spindles if you insist on keeping the inadequate torsion bars, but you'd just be trading one set of problems for another.

With /6 bars you will need every bit of that bump stop, because you will be constantly using it. Even at factory ride height you'd be using it, and you're much lower than that. Removing the bump stop to gain back travel is a terrible idea in this case, because you still won't have nearly enough travel to keep the LCA from bottoming out on the frame. Running without bump stops is never really a good idea, but with substantially less travel available than what the car will use with those torsion bars it's a really poor decision for this application.
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I WAS going to say, leave it like is if you like the sound of metal on metal crashing sound....
 
Mopar Tim said:
I WAS going to say, leave it like is if you like the sound of metal on metal crashing sound....
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Yeah exactly.

I run with a little under 1" from frame to bump stop with 1.12" bars and I still occasionally contact the bump stop. Granted I do not use a progressive bump stop like the factory ones, but if you hack the top off a factory bump stop it's not a progressive bump stop anymore and can't be treated like one.

Running /6 bars and no bump stop at all wouldn't work at factory ride height, it'll go metal to metal and destroy the suspension parts.
 
michiganpat said:
I cut mine down by about an inch, then I drilled a hole in it to make it a bit more progressive if I did make contact, kind of like this:
View attachment 1716264532

PRO TIP: put the bump stop in the freezer overnight before attempting to cut it. I used a coping saw to cut it and a regular drill bit. you may have to re-freeze after each step to stiffen it back up.
Click to expand...
edit that, I cut mine down by about a HALF INCH
I have about an inch between the cut bump stop and the Kframe, running .92" bars, but it feels like the suspension is still sitting high

car.jpg
 
michiganpat said:
edit that, I cut mine down by about a HALF INCH
I have about an inch between the cut bump stop and the Kframe, running .92" bars, but it feels like the suspension is still sitting high

View attachment 1716264612
Click to expand...

And yet it's not high enough for that suspension set up.

The factory intended the bump stops to be part of the suspension travel, it's why they're progressive like they are. They progressively add rate to the suspension as the bump stop contacts the frame, slowing the suspension but still allowing it to travel some. Effectively you get a rapidly increasing wheel rate until the bump stop is fully collapsed. That allows the soft wheel rate from the little factory torsion bars without totaling the suspension components or creating a bone jarring ride. It also means most people don't have a good idea of how often their suspension is on the bump stops. If you run factory bars and a lower ride height it's A LOT. And there are handling consequences for doing that.

If you get rid of the progressive part of the bump stop, you have to increase the wheel rate so you're not using the bump stop all the time. Basically it goes from a working part of the suspension to something that just keeps things from going "metal on metal", which is a different suspension philosophy if you will.

Those two different bump stop uses require very different clearance and wheel rates to work properly. If you want to run small factory style torsion bars, you need the progressive bump stops and you need more than 1" of clearance, just like the factory ride height set. If you use non-progressive bump stops, you either need to increase the wheel rate dramatically so you don't need as much suspension travel, or you need to increase the clearance. Either way you need to adjust things until you aren't using the bump stops very often.

A .92" bar is not enough to run that short of a bump stop and clearance. If you want the car lower, you will need larger torsion bars. Setting this up right is a balancing act between the wheel rate and available suspension travel (basically the ride height) and the type of bump stop you're using.
 
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