LCA bump stops

CO-Stark · September 19, 2019

Hi all,
I search and found some mentions of the bump stops but not what I'm wondering about. Has anyone changed out the factory lower control arm bump stops for something lower profile? Hoping for a little more up travel, even with the BDS conversion (new upper and lower arms) there's just not much travel and those bump stops stick down almost 3" from the mount, seems like a 1 1/2" or even 2" bump would still do the job but give the shocks more room to do their job...

Thoughts?

davester · September 20, 2019

Are you referring to the yellow part in this picture (yours maybe a different shape and/or color)?

If so, that is not a bump stop, but rather a "jounce", and it is part of the front suspension.

CO-Stark · September 20, 2019

6 hours ago, davester said:

Are you referring to the yellow part in this picture (yours maybe a different shape and/or color)?

If so, that is not a bump stop, but rather a "jounce", and it is part of the front suspension.

Yeah that's what I'm looking at, mine is cylindrical with a sort of dome that contacts the arm. Didn't realize it's 'part of the suspension', just looks like a rubber stop. So then the question is why is it so dang close to the lower control arm? Mine has a little more space than that picture after having my coilover conversion done, but there's still barely any travel before that would start to kick in. Why isn't there be more room for the spring (coil or torsion) and shock to do their job?

I'm on this kick because I changed some parts on my little commuter truck and doubled the suspension travel and it rides like a dream, so now I'm on the hunt for more travel on the big pig. See any problems with replacing this with something lower profile if it will still absorb a little (not just "stop")?

davester · September 20, 2019

Actually, I don't know about those, just about the torsion bar suspension setup. Yours might be a bump stop, or a combination of jounce/bump stop.

You'd need to at least make sure the rest of the bits of the suspension can also most that extra couple of inches.

CO-Stark · September 20, 2019

2 hours ago, davester said:

Actually, I don't know about those, just about the torsion bar suspension setup. Yours might be a bump stop, or a combination of jounce/bump stop.

You'd need to at least make sure the rest of the bits of the suspension can also most that extra couple of inches.

Can't imagine they wouldn't, the coilover kit is a 2-3" lift and it's set at 3", so I have a bare minimum 1" it would be able to travel. I had the torsion bars stock and the lower arm was almost resting on those before the lift...just don't understand why it would be designed that way leaving so little travel.

davester · September 21, 2019

Well, the travel is sufficient for the vast majority of these trucks. It's likely GM engineers put a decent amount of effort into designing it to function well for their customers. Just hacking off a bit to allow the a-arms to travel more can cause problems with other parts, such as shocks, u-joints, cv-joints, tires, tie rod joints.

newdude · September 21, 2019

21 hours ago, CO-Stark said:

Yeah that's what I'm looking at, mine is cylindrical with a sort of dome that contacts the arm. Didn't realize it's 'part of the suspension', just looks like a rubber stop. So then the question is why is it so dang close to the lower control arm? Mine has a little more space than that picture after having my coilover conversion done, but there's still barely any travel before that would start to kick in. Why isn't there be more room for the spring (coil or torsion) and shock to do their job?

I'm on this kick because I changed some parts on my little commuter truck and doubled the suspension travel and it rides like a dream, so now I'm on the hunt for more travel on the big pig. See any problems with replacing this with something lower profile if it will still absorb a little (not just "stop")?

Coilovers will have more travel than torsion bar that's why the jounce bumper is where it sits.

I assume that having gone to coilover, you no longer have the torsion bars in there?

Do the BDS coilovers have a jounce bumper in them? On the 1/2 ton Chevy trucks, the OEM struts have the jounce bumper integral to the strut. Sits right under the bottom of the strut mount. No bumper on the frame to the lower A arm.

Edited September 21, 2019 by newdude

newdude · September 21, 2019

16 hours ago, CO-Stark said:

Can't imagine they wouldn't, the coilover kit is a 2-3" lift and it's set at 3", so I have a bare minimum 1" it would be able to travel. I had the torsion bars stock and the lower arm was almost resting on those before the lift...just don't understand why it would be designed that way leaving so little travel.

This was from a GMT-800/900 but gives a good visual.

https://www.youtube.com/watch?v=mf1bhVI7bL4

CO-Stark · September 21, 2019

7 hours ago, newdude said:

Coilovers will have more travel than torsion bar that's why the jounce bumper is where it sits.

I assume that having gone to coilover, you no longer have the torsion bars in there?

Do the BDS coilovers have a jounce bumper in them? On the 1/2 ton Chevy trucks, the OEM struts have the jounce bumper integral to the strut. Sits right under the bottom of the strut mount. No bumper on the frame to the lower A arm.

Correct no torsion bars, and like I said above, theres easily another inch it all can travel because before they adjust the coilovrs up 1" I was sitting that much closer to the 'jounce'.

7 hours ago, newdude said:

This was from a GMT-800/900 but gives a good visual.

https://www.youtube.com/watch?v=mf1bhVI7bL4

Thanks for that, in that video the jounce looks to give much more than I thought, wonder if mine are the same, in which case they don't limit travel as much as they slow it down til it hits limit, if that makes sense. Thank you.

MNorby · September 21, 2019

I'd be half inclined to remove it and remove your springs from the COs and check travel, clearances, and motions with it at bump. If all seems fine figure where full bump should be and trim it to just a touch longer than that to account for compression.

CO-Stark · September 22, 2019

17 hours ago, MNorby said:

I'd be half inclined to remove it and remove your springs from the COs and check travel, clearances, and motions with it at bump. If all seems fine figure where full bump should be and trim it to just a touch longer than that to account for compression.

Yeah that would be ideal, don't know if I have the time for it tho...and the impression I get is those coils are sprung pretty hard in there so I'm not too sure about pulling them out in the garage... I may just see if I can get these off and then look for a generic jounce/stop that's about an inch shorter. We'll see.