Shocks and rear wheel allignment

Fifty150hs · #1 10-09-2016, 01:07 PM

I took my 2006 3.0i with standard suspension (no airbags) in for a wheel alignment. The mechanic could not get the rear camber into spec. He said he thinks it is because the rear struts are shot. (so are the fronts, I don't think they've ever been changed in 180,000 miles.) He said he thought the worn struts were allowing the rear end to sag thus forcing excess upper, inward camber. Does this sound right to you guys? I didn't think shocks had anything to do with ride height. I thought that was controlled by springs. If it is the shocks I'll replace and hopefully solve my problem. I'll replace them anyway due to their age, but if the problem is caused by something else I'd like to address it at the same time. Any input is much appreciated. Thanks

O3X5 · #2 10-09-2016, 01:45 PM

Shocks control up/down while springs control side to side

bcredliner · #3 10-09-2016, 02:03 PM

while the primary role of shocks is to attain a certain ride by how they compress and rebound, worn shocks can cause a lower ride height if shocks are worn out. The lower the vehicle rides the greater the negative camber. Excessive negative camber will wear the inside of the tires. Springs have nothing to do with side to side movement. Modern springs seldom sag.

X53Jay4.8is · #4 10-09-2016, 02:21 PM

Quote:

Originally Posted by Fifty150hs

I took my 2006 3.0i with standard suspension (no airbags) in for a wheel alignment. The mechanic could not get the rear camber into spec. He said he thinks it is because the rear struts are shot. (so are the fronts, I don't think they've ever been changed in 180,000 miles.) He said he thought the worn struts were allowing the rear end to sag thus forcing excess upper, inward camber. Does this sound right to you guys? I didn't think shocks had anything to do with ride height. I thought that was controlled by springs. If it is the shocks I'll replace and hopefully solve my problem. I'll replace them anyway due to their age, but if the problem is caused by something else I'd like to address it at the same time. Any input is much appreciated. Thanks

With the degree of miles on the X5 you probably have a number of worn suspension components that need to be replaced to get it back into geometry and spec. Its not related to shocks and springs.

bcredliner · #5 10-09-2016, 02:51 PM

Quote:

Originally Posted by X53Jay4.8is

With the degree of miles on the X5 you probably have a number of worn suspension components that need to be replaced to get it back into geometry and spec. Its not related to shocks and springs.

It is an assumption the suspension has not been rebuilt. Even if it has not that does not eliminate the shocks as a contributor or the single cause of not being able to bring camber within specs. Certainly, if the suspension has as many miles on it as the shocks the suspension is due to be rebuilt so it should be thoroughly checked prior to purchasing shocks.

oldskewel · #6 10-09-2016, 03:24 PM

The shocks would be about the last thing to consider here. First would be the ball joints. Second the rear upper control arms. Search on here for cases where people actually had a similar problem (uncorrectable excessive rear negative camber) and what they found the actual problem to be, and you'll find the above. Skip all the info about replacing everything based on mileage - just because that tells you nothing about cause and effect.

Nice thing about shocks is that they're easy to replace. But for your case, you could probably repaint your car too with similar effect. (none)

You are correct in that the primary purpose of shocks is to provide a damping force - i.e., a force that varies with the *rate* of motion. Springs provide a force that varies with the displacement. But shocks are often gas-charged, which means that in addition to the damping force, they provide a spring force (that is far lower than that provided by the real springs, but can be enough to affect the ride height slightly). In the simplest case (from physics class or wherever they might teach it), the damping force is directly proportional to velocity, and the spring force is linear with displacement. In reality on cars, they complicate these simple linearities to improve performance (compression vs. rebound, variable spring rate, etc.). But the basics of rate-dependent damping vs. displacement-dependent springs are still true.

You can check your ride height and compare it with other x5's. If the tire sizes are the same, you can check the gap between the top of the tire and the fender. If tire sizes are different, you can measure from the wheel hub to the fender lip. Cars of course must be parked on level ground, and not overloaded, etc. for a fair comparison.

Regarding replacing them even if they are not a problem. On the one hand, they are absolutely easy to get to and replace at any time you feel like; no need to think that "while you're in there ..." On the other hand ;-), while you're in there fixing your ball joints you'll be at least removing the bottom connection, if not the whole shock. So even though it's easy to replace later, you'll literally have the old part in your hand with the decision of whether to put it back on or put a new one on. Mine (at 170k) seemed fine and I put them back on.

Fifty150hs · #7 10-09-2016, 05:11 PM

Thanks guys. No work has been done to the rear suspension that I'm aware of. I expect I'm going to need to do some work there. I just replaced everything up front except the tie rod links. Feels much better. Tighter. Still getting occasional clunking up front but not as bad as it was. Still haven't been able to run that one to ground yet. Given the milage I suspect a complete rear suspension refresh is in order as well as new shocks. I just wanted to check because I learned way back in the day that shocks were for dampening not lift. Unless of course we go back to the 70's and air shocks. ;-)

X53Jay4.8is · #8 10-09-2016, 05:15 PM

Quote:

Originally Posted by Fifty150hs

Thanks guys. No work has been done to the rear suspension that I'm aware of. I expect I'm going to need to do some work there. I just replaced everything up front except the tie rod links. Feels much better. Tighter. Still getting occasional clunking up front but not as bad as it was. Still haven't been able to run that one to ground yet. Given the milage I suspect a complete rear suspension refresh is in order as well as new shocks. I just wanted to check because I learned way back in the day that shocks were for dampening not lift. Unless of course we go back to the 70's and air shocks. ;-)

The rear suspension on our X5s are sophisticated compared to other common SUV which gives then the dynamic of handling they possess. There are number of links with bushings that should be changed and restore it back to its natural order.