Chevy & GMC Vans

Hoping the experts can comment on my ride quality issues -

I'm more than a bit unhappy with the on-road behavior of my current setup. I've got the Overland 4" lift with maxed stock keys, and OEM rear shackles since I was getting a ton of lift just from the springs (more on that in a moment.) Bilstein shocks in the front. OEMs in the rear, with relocated shock tabs. With 60k on the van, I'm sure the rears are toast. Bilstein replacements on the way for the rear. Tires are Yokohama Geolandar 245/70-16 on stock aluminum 5-spoke wheels.

Yes, I acknowledge this discussion is semi-pointless until I know the rear shocks are replaced and functional, but I'm not sure the problem I'm having is solely a lack of rear damping (although maybe it is?).

The ride is more than a bit harsh, and occasionally I hit a bump in such a way that it feels like suddenly there's no rear up-travel. It doesn't happen all the time, but sometimes a bump that doesn't look like a "big" one will crash the rear end pretty hard, sort of the way it felt in my old Miata when I was getting coil bind on too-soft lowering springs. What's weird is that in those situations it feels like the rear doesn't compress at all. Almost like somebody jammed a log in between the leaf and body.

Here's what I'm sweating: I swear it's like my springs are too firm.

When I first fitted the lift, the rear was REALLY high. I even started a thread on it. At the time I reached out to Overland Vans and tried to confirm that I didn't get the heavy-duty spring pack, but the regular 22-687 (1350lbs) springs. I ended up switching back to the OEM rear shackle to get things back to a manageable level. With maxed stock keys and the 2" pucks, I wasn't QUITE able to get to level, but I didn't want to swap the keys.

I've even re-confirmed the part# against my photos of the lift installation and called the spring manufacturer directly, so I guess I really do have 1350lb springs. What's weird is that despite having more arch, these have theoretically 60lbs LESS load capacity than the stock springs (which are 1410, according to what I can find). I haven't had the van weighed, but given that I have the pop-top, a big house battery, an oversized spare tire, and now a water tank, I don't think I'm running a "light" load, and yet the ride quality has that "empty 1-ton truck" feeling some of the time.

Am I totally nuts? When I do the old "rock the vehicle on the springs and see if it oscillates" test, it doesn't ACT like the shocks are failed. Like I said, I've got replacements coming, but I'm just concerned this isn't going to fix whatever else is going on. Up until now, I haven't cared that much because the van only got used for weekend camping trips and the occasional big-box store run, but now I'm seriously considering making the van my daily driver for a while, and I'd like to not hate every minute of that...

Is there anything else I should check?

Thanks.

I can't offer a direct comparison because I don't have 22-687 (1350 lbs) or the 22-687HD (1750 lbs) because I'm running Fabtech add-a-leafs on the stock pack and OLV/Airbagit shackles in +2" position. I do want to install a set of 22-687HD springs eventually.

There are a few theories available though:

It could be as simple as a case of not enough shock damping to control spring movement right now and once you install better shocks, the problems will lessen.

With the worn out shocks and relocated shock mounts, it is possible the shocks are bottoming (or topping) out?

I don't know what your van weighs with all your mods, it could even be a case of being under-sprung in the rear. That, combined with lack of compression damping in the shocks can feel very harsh.

Or the over bump harshness could be a lack of rebound damping to slow the movement down once it has compressed and springing back. Of course, it doesn't help that the stock shocks probably don't have much, if any compression damping left in them either.

Are the Yoko Geo's "E" load and what pressures are you running? They will transmit more load directly into the suspension due to the stiffer construction, not to mention the additional unsprung weight of the tires.

Realistically, the stock rear leaf springs anyone is riding around on today are nowhere near close to the stock rating any longer and probably pretty sagged out in most cases whereas your springs are new and closer to the original rating.

Once you get the Bilstein shocks installed on the rear, you'll have a much better idea of where you're at!

Just some random thoughts I had for you...

The other thing to check is your shackle angle to make sure it alows the back of the leaf to move. If the angle is wrong and it doesn't alow the spring to move forward and back as it compresses it can hold the spring in place. Lie under the van and have someone jump on the back bumper so you can see if it cycles smoothly.

Kidhauler wrote:The other thing to check is your shackle angle to make sure it alows the back of the leaf to move. If the angle is wrong and it doesn't alow the spring to move forward and back as it compresses it can hold the spring in place. Lie under the van and have someone jump on the back bumper so you can see if it cycles smoothly.

That's very likely to happen if the springs were installed Short End to the front. When I installed my springs the correct way (SE to the front as leafs were designed to be used) I had to make my own offset "boomerang" shackles to clear the frame and keep from describing the scenario above.

Before, OLV lift shackle:





After, homebrew offset shackle:





X2 on getting under there and looking. If the spring was installed SE to the front I'm sure you would have very little tire clearance in the front portion of the rear wheel well.

Ok guys, that's great info, thanks.

I remember having the concern about which end of the spring went forward. My solution was to measure the OE spring and keep the same spacing for bushing to pin distances, but I will re-check. I think I have proper tire centering in the rear well, so that part is probably ok, but it costs nothing to check that while I'm under there watching the shackle while my wife jumps on the bumper. ;-)

I will also re-check the overall lift in the rear. If things have settled out a bit, maybe I can re-fit the overland shackle s well.

I should clarify. When I said the "correct way" I meant that springs are designed with the short end to the front to make that part stiffer and less likely to bend from axle wrap. The long end goes to the rear to keep things nice and cushy. For whatever reason the designer of the Astro van decided they would be installed ass backwards. Stock on these vans is long end to the front. I swapped mine around because it just made sense to me. Of course a lot of other mods made that possible.

OK, UPS finally came through with my Bilsteins. Right rear was probably too squishy, but didn't look awful:



Left rear was positively toast, however:



And best part of the job was that I had a great helper:



So after a brief test drive, I can say that things are already improved noticeably. So I guess my personal "shock dyno" sucks and is out of calibration. Pursuing the theory that I might also be bottoming the shocks, I re-checked my ride height to compare against old data:

Old measurements (post install, 2011): Current measurements (7/26/2014): So that's around 1" of settling in the rear. Given the weight I've added, (fridge, battery, water tank) it sounds fair. I'm agreeing with the shock-bottoming theory now, since while installing things I could feel where the end of travel was, relative to the "neutral" position when the van is more or less flat. Time to raise the rear up again, so I will re-install the OLV shackles.

I've been having more thoughts on my suspension in particular, and some of our accepted wisdom in general. It seems like pretty standard practice to raise up the lower shock point when doing a lift. Either using the OLV shock tabs, or cutting/bending the OE mounts, or whatever. The motivation seems to be to remove the under-axle tabs so they don't hang up on stuff, and to be able to use stock-length shocks.

I'm wondering now, does this endanger the shock at all? It seems like this sort of reduces the ability of the bump stop to protect the shock. On the one hand, you're compensating for the lift which returns the shock to its (approximately) factory operating range (i.e. the neutral position of the shock should be roughly the same since you raised the pick up point by about the same amount that you "lowered" the axle, relative to the upper mount. But the bump stop is on the axle, and now it sits 4" or so farther down. Doesn't this increase the likelihood of bottoming the shock instead of hitting the bump stop?

Just curious. I'm far from the expert here, but trying to do some critical thinking.

Anyhow, I've re-installed the OLV shackles in my van, so my ride height is about where it was 3 years ago when the lift was first put on. Time will tell if that and new shocks fixes what ails me.

Being I just went with a two inch lift I didn't relocate or replace my shocks so I hadn't given this much thought but i think you may be correct in thinking that a stock shock in a raised tab could be vulnerable to bottoming out without modifying the bump stop, and that ain't good for the shock. I know with my last project I got huge rear axel travel and the limiting factor was the shocks . A buddy recommended I install limiting straps . Same problem only in reverse I am thinking.

If a shock repeated bottoms out top or bottom i think it would lead to failure.

Put a ziptie around the shock shaft to get an idea how much travel is being used.

Stroverlander wrote:Put a ziptie around the shock shaft to get an idea how much travel is being used.

That's an idea with merit. The Bilstein boots are more sleeves, so I'm not sure I'll be able to get to the shaft easily, but I'll take a poke at it.

Another update, having done some more research, it seems that I might not be completely insane on the bumpstop thing. It seems that "bumpstop extensions" are a common item, and not very expensive. For my own piece of mind, I will probably order a pair and try to fit them up.

I'm not so worried about on-the-trail issues, since I don't wheel as hard as most here seem to, but I'm supremely worried about street issues. SoCal city planners and street designers make frequent use of those concrete drainage channels at intersections. They are highly variable in terms of depth and placement, and I have occasionally bounced over them HARD when I didn't see one or was going through an intersection at speed. As mentioned upthread, I got to coil-bind on my Miata when those dips fully compressed the rear, and I'm fairly certain that hitting one of them hard in my Z3 coupe was what finally broke the welds on the rear subframe (a common issue). I'm more than a bit worried that if any one thing is going to bottom out the rear shocks, it'll be one of these!

Looking forward to your observations.

Tires are Yokohama Geolandar 245/70-16 on stock aluminum 5-spoke wheels

I know this is old but I'm doing a tire search and saw this. So......

I put these same tires on last summer in stock size. They FIXED my ride issues from carrying too much weight and hauling a bike on the hitch and towing an almost 5k camper. BUT.... I feel every crack, pot hole, road patch beyond what I want to feel!!!!

These tires are stiff and do not absorb like p-rated tires do. In this situation from OP I would think a lot of the harsh ride is due to the stiff tires.

(TREAD-JACK) I want to use up a pair of P-rated tires. These Geolanders are not good in snow so I plan to put the P-rated tires on the back. I need traction to get up and out the driveway and with the van empty for winter I'm thinking they won't squish and return me to the unstable ride I had loaded up. Any thoughts?

I had 235/70-16 Geo A/T-S XL load with Bilstein shocks and the ride didn't feel that way at all although I previously I had two sets of stock size 215/70-16 SL load Geo A/T-S so perhaps I got used to the ride characteristics somewhat.

I do feel like the XL load tires were an improvement over the SL tires. Towing, I used to run around 38 psi front / 40 psi rear and a bit less empty.