Yukon Bump stop issue?

[ryangt]

Hey folks, i have been feeling like the front end of my 2004 Yukon 4x4 isnt what it used to be, it tracks poorly now (probably just alignment) but ive noticed a nervousness in the front end when hitting bumps on the road, i looked under there today and noticed that the lower control arms rest on the lower bump stops.... is that how it is supposed to be? Seems to me that a bump stop should not be touching the suspension components. Can anyone shed some light on that for me?

 

[Grebbler]

I have heard arguments for both sides. Conventional wisdom treats them like bumpstops and there should be clearance. The other side had a compelling article stating that the bumpers are more like progressive rate Timbren blocks (rubber springs) and factor into the suspension. This argument gains validity as just about everyone, with an unaltered stock suspension in our year range polled, said their trucks were resting on the blocks, also.

I don't know what you mean by 'nervousness' so I cannot directly address your situation. Many factors such as weight distribution, tire pressure, wheel alignment, condition of the shocks, and torsion bar pre-load will affect the way the truck will handle bumps.

So, now that I have you thinking about all this I will relate my experiences while I was experimenting with front end height adjustments awhile back.

When I would hit a wide bump that affected both wheels at once I noticed a tightness on the driver side as it seemed to rebound quicker than the other side. This was caused by the infamous GM Lean condition where most Tahoes and Yukons 'leaned' towards the drivers side front corner where is was around an inch lower. This caused the control arm to be either closer to the block or resting on it more than the other side. This made the truck act like it had a stiffer spring on the drivers side. When I adjusted the torsion bar to bring the drivers side level with the other, plus a tad more to make up for my weight since I normally drive alone, the front end behaved like it should. This was with the bumpers very lightly on the control arms and this gave me a nice tight Euro feel that cornered well. As winter set in I jacked the torsion bars more to get extra ground clearance. This ok for height but the extra preload stiffened the front end so much I took a beating on the crappy roads in the Detroit, MI area. This was with the bumpers about 3/8 to 1/2 inch off the control arms.

After much experimenting, my sweet spot seems to be about 1/16 to 1/8 inch off the arms. Not as tight a feel but enough leeway to allow for pot holes and the occasional small car or pedestrian. I used a piece of standard shipping box cardboard as a feeler guage and keep the tires at 35 psi. As this suspension has a short travel - a small adjustment is pretty noticeable.

Good luck with it.

Ed

 

[BOSS]

Here's one of my theory's....my experience is different than Grebs, if I level my truck out on both sides, it makes the lurch worse.

Also, the difference in stock ride height is due to the compression and rebound on the body mount bushings over time. The rest of the components are also affected over time as well, making the issue worse. But you'll notice, when you replace your suspension components...the height difference remains

I addressed the difference in ride height by removing the rear spring isolators and adding more strips of rubber to the ends of the springs on one side. I also adjusted the torbars a little bit. I can't say it's 100% but it's DAMN close.

Here's what I posted the other day about torsion bars,

Mine were taken out and put back in and that affected the ride height on one side of my truck. My theory is that since the torsion bars are under constant load for years, if you were to take them out and roll them on the ground they might roll like bent pool stick. So (again "in theory") if you were to put them back in such a way that they are not the same placement inside the hex holes, you could have one side providing a different load capacity and thus different ride heights. So to compensate for that, you must adjust the keys differently from one side to the other to achieve the same height. THAT also seems to me that the load would be different because the pressure would be different and you get what I have on my truck - a slight lurch to one pass side on deep dips in the road. Granted, some might not have ever noticed this on their trucks but when you do your suspension work yourself you tend to notice EVERY single picky ass thing


B