Making the HD ride better

number9 · February 3, 2005

As some of you may know by now, I bought an 02 GMC 2500HD last Friday. My 99 Z-71 rides very good and this HD, well rides like an HD would be expected. I am the 3rd owner. 1st owner had it for 4900 miles and 2nd owner had it to 27000 and now I have it. Apparently the 1st owner cranked the T-bars and had larger tires on it as the air dam is trimmed. The PO didn't even realize the T-bars were cranked or that you could even do that. I have measured and it sits 39" to bottom of front wheelwell and 40" to bottom of rear wheelwell. It has about 1/2" or so gap between the jounce bumber and A-arm, the stock 245's at 50PSI at all 4 corners.

I plan to mount 265/75 tires and will go with Mich LTX-M/S most likely. It will be daily driver and not haul/tow anything larger than utility trailer with couple streetbikes as largest payload.

I have searched this board for several hours and seen posts of adding spacers to front shocks to improve down travel and ride. I have also seen mention of velvet ride shackles. I plan to make spacers for the shocks and maybe get the shackles as well. Has anyone addressed issue of spacing jounce bumper back down to contact A-arm as it was designed to be? Also, what load range (D or E) and air pressures would you guys recommend based on the planned usage of my truck for best ride quality without totally sacraficing the HD capabilities of the HD?

Here she is - bad pic I took at sellers house before buying it but only one I have at the moment.....

Bgdsub72 · February 3, 2005

turn the torsion bars back down and you will gain better ride quality...that about it...still gonna ride like an HD.

btw...nice truck.

Shaners · February 3, 2005

I'm running 265/75/16 Michelin LTX M/S (load range E) @ approx 50 psi on all four corners and the T-bars cranked just a few turns. The ride is better in warm weather than in the cold... However, after 3 1/2 years and 18K miles, I think the stock shocks are about junk.

I would suggest changing the shocks as a good place to start for ride improvement.

With the type of hauling you'll be doing, a load range "D" in a 265 should be a heavy enough tire. It actually has about the same carrying capacity as a 245/75 load range "E" tire, but should ride a little better.

lrymal · February 3, 2005

There will be a zillion different answers on the ride-quality issues. The only alleged facts that I ***know***, supposedly, are that the front end needs to be positiioned geometrically as determined by this thing called the Z-Rating. It is basically a geometric trim adjustment with the T-bars and THAT, along with shocks that are NOT positionally affected, will give the factory ride quality back. I have seen so many high school guys (Besides farm work, I work in education), who have taken their GM trucks in for the Z-trim adjustment because of the stiff ride as a result of their doing the T-Bar front-end rise. They tell me having the adjustment done solved their ride problem. Can't recall what they did about the shocks, though.

This adjustment is there for weight-induced front-end lowering compensation because of snow plows, etc.

number9 · February 3, 2005

Hmm.....that's a new one for me. Never heard of this Z adjustment. I am assuming this is only on HD's then? and is part of alignment process that dealer will know about / can do?

firstruck · February 3, 2005

Wow! like you guys are reading my mind. My new to me 1500HD will need some work on the jounce snubbers and a little crank on the T bars to reverse the effects of gravity. In a quick look last week to see what this t bar thing is all about, I saw a yellow label on the crossmember warning of setting the T bars to the correct Z setting. Don't know what that is but I'll need find out before replacing the snubbers and cranking the bars. So, what is this "Z" setting?

lrymal · February 3, 2005

Not sure why the Z setting is called that. I'm guess it is some sort of geometric definition for vehicle suspensions. The shop manual has a chart with measurements and a couple of pages on how to get the Z setting to where it is supposed to be. When a heavy accessory is installed on the front end, one is supposed to adjust the T-bars and get the Z setting back to factory specs. When that heavy accessory is removed, then likewise, readjustment is needed.

I'm not near the shop manual I bought, but maybe someone can scan those pages so y'all can see. In the meantime, here is a thread regarding issues about adjusting the torsion bars and a harsh ride (as opposed to firm ride---there is a difference):

http://www.gm-trucks.com/forums/index.php?...c=33694&hl=ride

mamachala · February 3, 2005

Number 9,

If you decide to go with Velvet Ride spring shackles I have a new set I'm going to sell. I put them on my '01 K3500 for 2 weeks, but the air springs I have on it didn't allow the shackles to move enough to smooth the ride. They are $160 new, I'll sell them to you for $100, that includes shipping.

Jack

http://www.lord.com/Default.aspx?tabid=921

Here is a link with shackle info.

number9 · February 3, 2005

You have mail.

Mighty HD · February 4, 2005

what do those shackles do?

lrymal · February 4, 2005

what do those shackles do?

<{POST_SNAPBACK}>

http://www.lord.com/Default.aspx?tabid=872

Valsport · February 4, 2005

I think the reason it is termed a Z adjustment is because of the direction of the adjustment in 3D space. If you remember your calculus the x-axis comes out at you from the page, the y-axis runs a parallel east to west from the ground, and the z-axis runs perpendicular to the y-axis (movement of elevation). This is the direction that is changed when torsion bars are tightend or loosened.

number9 · February 5, 2005

Well, I tinkered with the truck a little today. First time I had checked, but the T-bars are maxed out, well the LH has 1/4" and the RH has about 5/8" thread left. I made spacers for the top and bottom of the shocks. When I took the shocks off I didnt like how the LH one felt, VERY slow to rebound when copressed. The RH shock was/is hammered. Very hard to compress and extremely slow to rebound and only returned about 3/4 way and stopped. Anyway, got the spacers on and took it for a drive - rides better without the harshness of the shocks bottoming out.

I have decided against the velvet ride shackles, as I have read here that they will lower the rear of the truck about 1.5" and I don't want to do that. One of the main reasons I decided on getting an HD was due to the fact that they sit nice and tall - like a real 4x4 should.

Now I have to add another decision to think about......what shocks to get Rancho 9000 or Bilstein AND to get longer or stock and use spacers I made?

2nd, to add 265 or 285's?

How bad would 285 kill gas milage/power?

If going with 285, leave cranked or add green keys and *maybe* rear block?

Ahhhhgggg......I haven't even started driving this thing yet.

N900WM · February 7, 2005

Number9,

I have the Velvet Ride shacles on my truck as well as the Road Master set-up. I did not detect any rear end drop when I installed the shackles. However, I already had the Roadmaster installed at the time. Both devices have helped the ride characteristics to a noticable extent. It helped enough to make a difference. I would and will install both again an a new truck when the time comes.

Unfortunatly, the front is still stiff and you can feel the front jounce more than the rear. To me, the rear is still firm but not nearly as rough. Makes a long trip a bit more comfortable, especially with some weight in the back.

I can send a picture of the stance with 285's and the rear suspension set-up installed if you want to see it. Just shoot me an e-mail and I'll send it to you.

I didn't notice much difference in power loss with the 285's. If anything, the truck seems to have better low end throttle response and certainly better traction on launch. And she will still burn'em off if requested.