Lowering yellow bump stops

[clifcotim]

After searching this out here these are called auxilliary springs by GM and are an integral part of the suspension as far as ride. Has anyone tried to install some flat spacers between the yellow springs and the frame to bring it back down to the lower arm after a torsion bar raise? If so did you see any problem or reason not to do it?

[clifcotim]

C'mon guys surely someone has tried to do this? It looks like all you have to do is extend the bolt and add flat spacers to bring the spring back down to pre-raising condition. Mine looks like it needs to come down about 1/2". Any comments appreciated.

[DA BIG ONE]

Originally posted by clifcotim:
C'mon guys surely someone has tried to do this? It looks like all you have to do is extend the bolt and add flat spacers to bring the spring back down to pre-raising condition. Mine looks like it needs to come down about 1/2". Any comments appreciated.

Let me give it a try!
When cranking torson bars past recommended setting
you not only change height, but rate too which in return effects ride quality, so I would say the bumpstops may no longer be up to the task they were designed for.
IFS has a problem when it is fully compressed, usually bent tie rods, it is doubtful that this would be an issue a street driven truck when torson bars are cranked up.
AirRide makes a longer heavy duty bumpstop for the front GM IFS 4wd that is a 3 stage unit to handle plow blades/heavy winches and the like, so it should be up to the task of preventing full suspension compression/failure off road "stiff as hell".

[LJ]

Call me an idiot, but I just don't get what a couple pieces of rubber should have to do with a suspension which should be "heavy duty" (2005 Duramax Silverado 2500HD). I mean, come on... why should they be in contact all the time???

If the bars are let all the way down to where they are in contact, then there's less opportunity for the suspension to settle under a heavier load. THAT'S WHAT SPRINGS (or torison bars) ARE FOR!!

Not only that, but on mine (before I raised the bars) it was fine as long as the pavement was smooth- but when you hit a bump, instead of the wheel going up, the whole truck went up! There was no room for the wheel & control arms to compress (go up).

And the worst part is that when the whole truck went up, the shocks were so weak that as the truck was levitated they allowed the wheel to shoot back down on the other side of the bump and bounce on the pavement- making "Like A Rock" to mean something else other than the solid feeling you should get from a vehicle of this price class.

Sorry for venting, but I'm upset. Is it possible that this deal with the "bump stops" being an "integral part of the suspension" is nothing more than trying to cover up the shortcomings of a shoddy suspension scheme?

Larry Jones

[Jim Brzozowski]

I cranked mine up just a little to level it out across the truck and it rides smoother now. There is about 1"clearance to the bump OOPS auxillary springs. Kennedy can sell you a set of Bilstein shocks that will help a lot.

[Pewter Max]

I just replaced both of mine , I happened to look up under mine a few days ago and the one on the left was completely broken away and the right one had a chunk missing .
I called my local dealer and they ordered me a pair @ $25. each .
Once I got them off I was amazed that they are made of some kind of stiff foam and covered with a thin skin of Vinyl ??
My suspension was down on the "Bumpers", That's what the package they come in calls them .
I raised the front end up just enough to clear the "Bumpers and I can tell the difference in the ride quality - "Smoother".
I looked under the front of my friends 03 GMC and his "Bumpers" are "Squashed" too , we will crank his up next week .
I can't see where these will be a long lasting part - kinda like the Infamous Wiper Circuit Boards that GM has sold Tons of .
But still the best truck i've ever owned !!!

[DA BIG ONE]

Did a little research, found that those bumpers are supposed to reduce bending/failure of tie rods on full compresson/extension of suspension in IFS 4wd trucks. Some years are worst than others.

This design flaw gave way to aftermarket fixes like: http://bulletproofsteering.com/gmifstierod.html

[ 07-31-2005, 02:05 AM: Message edited by: DA BIG ONE ]

[JoeyD]

The rubber bumpers are there to give the suspension a progressive rate. Torsion bars are constant rate unlike leafs and coils which are progressive.
Cranking the bars does nothing but move the suspension to a different neutral setting reducing down travel and causing the crap ride and faster ball joint/ tie rod wear.

[DA BIG ONE]

Originally posted by Joey D:
The rubber bumpers are there to give the suspension a progressive rate. Torsion bars are constant rate unlike leafs and coils which are progressive.
Cranking the bars does nothing but move the suspension to a different neutral setting reducing down travel and causing the crap ride and faster ball joint/ tie rod wear.

This information will go far in better understanding this GM IFS, for me at least, I had no idea that a torsion bar rate does not change with height.

So, the AirLift bumpers are the upgrade for increasing rate/height if need be.

I suspect that GM maybe using a version of the AirLift bumper in its newer IFS trucks. AirLift bumper for GM IFS measures 2 7/8" high x 3 3/32" wide, and has three progressive sections.

[LJ]

Joey, I hear what you're saying, but think this through- torison bars are progressive, just like springs. As they flex, it takes more weight to make them flex more. No matter at which height they are set, when you increase the weight in the truck, they settle down under load and the truck rides lower. When you hit a bump, they flex. When you raise them by cranking them up, you simply change the points at which this all happens.

Now, to the real point. What in heavens name is GM doing trying to make a plastic part absorb the strain from either overloading or a severe bump?? Give me a break- that is the job of the T-bar, the shocks, and maybe a bumper to protect it all from too much travel- but not some plastic part to "gradually increase the resistance as weight is applied" or some other justification.

GM should quit trying to make trucks ride like cars. Make them trucks!! Trucks ride stiffer than cars almost by definition. This junk about using rubber cushions is crazy. And while I'm on the subject, why don't they put some real shocks on these things!! The stock ones are junk. My truck cost a few dollars short of $50,000- and it has junk for shocks.

Sorry for the rant. I am just incredulous that my 2500HD Duramax 4WD has to use little plastic pieces for it to ride gently. What is this world coming to.....

LJ

[oyazi]

I first noticed this bump stop being an active component when I purchased my first new truck ~ an '84 Toyota 4WD. It was good, but not in keeping w/my mindset/view how the world should be. So when I lifted it 2.5", I didn't get the extended bumpstops and noticed that the frontend to be jauncy.

I first noticed this on the DMAX in 01 at the dealer and had everyone come out and see it bottomed out. We rationalized, reasoned etc. one guess at the time was that it was intentionally set that way for shipping/transporting from the factory. The term used back then was the Sierra/Silverado 'slope'. In time it became apparent that it wasn't intented as a passive bumpstop but an active suspension part ~ GM just followed the Japanese. So, personally, along w/turning a new century, getting closer to social security, I simply added this to the list of changes to accept ~ and move along.

[LJ]

Oyazi, I relate to the new century, moving on, and all that. Please don't hear me saying I can't change. I only think the suspension scheme stinks when part of the weight of the vehicle is suspended on two plastic parts that cost a quarter each, and have to be replaced after some heavy use....

After much thought on the subject, I think it may be cheaper for GM to use two 25 cent priced pieces of plastic to mask a bad ride than having to add the price of superior shocks to the cost of a new truck. Call me cynical if you wish...

To ask that a truck ride along on compressed plastic parts instead of having the suspension freedom to flex with the terrain is a stretch in any suspension scheme. That assumes that the truck will normally always be used on pavement. With some of us, that's not the case.

Without a doubt, there may be something to the idea of having the truck lowered for transportation. It just stands to reason that it would give it more room on the car carrier.

As to the comparison to the Toyota, what was the GVW on it? I suspect it was roughly half of my 2500HD Duramax's almost 5 tons (9,900lb). Surely that has to make a difference in how you scheme out the suspension.

LJ