[Kmac]

I have noticed multiple threads with front end issues as the main concern. I am curious if we are making something out of nothing, or is there a true problem. If there is a problem, I curious to know what it was, what mileage and was it resolved.

 

[Lscman]

I have noticed multiple threads with front end issues as the main concern. I am curious if we are making something out of nothing, or is there a true problem. If there is a problem, I curious to know what it was, what mileage and was it resolved.

Your inquiry is a bit odd, as if you feel failure rates are absolute and based strictly upon miles or some folks with suspension issues are imagining things. Clearly, some cars have no suspension problems while other's do. The condition of each car's suspension varies WIDELY. Condition of suspension components is greatly influenced by:

1) duty/use (street or track flogging)
2) driving behavior
3) short or long trip
4) ozone, dirt, temperature and other environmental factors
5) cleanliness
6) condition of dirt boots on dampers and joints
7) road conditions (smooth, rough etc)
8) cargo/weight
9) mileage
10) age of vehicle
11) original parts or replaced before

E39 has fundamental weakensses in the front suspension which specifically include dampers leaking in 50K miles or sometimes less and thrust arm bushings that tear and fail every few years with little or no correlation to mileage. The thrust arm bushings can cause the suspension to go into an underdampened oscillation at certain speeds that makes the car very difficult to handle. The vibration with bad bushings generally occurs under braking. The dampers can lose their hydraulic fluid from bad rod seals which causes the car to handle terribly and it encourages the wheel to bounce like a ball on rough roads at certain speeds. Folks who do not recognize these E39 weaknesses and inspect this hardware often flush (waste) lots of money on aftermarket suspensions and new tires or wheel balancing.

The thrust bushings (two) are about $40 each and the dampers cost about $200 each. These components should be replaced in pairs. When replacing dampers, it always works best to replace all four. Aftermarket Koni's are superior to OEM.

Your car may or may not have these problems. A poll will not help determine that. I would suggest getting a technician to investigate.

 

[Kmac]

Agreed on where to take it to get it fixed, since a suspension is a highly complicated system, without multiple parts failing. What I was looking for was a small cross section of quantitative (your arguement that its could be qualitative is duly noted) data within the community to see if the failures on the components that we have so much discussion about are simply wear out failures or actual design weaknesses. Most, not all, car manufacturers design wear components to fail outside the normal warranty range to minimize expense, which is why I chose 30k miles as the first parameter. If parts are failing prior to the designed warranty period then its a design flaw. So, imho, if its a design flaw I am not going to put the same part back in only to have it fail again if there is an alternative.

Case in point - I have thrust arm bushings that are torn. Do I put the OEM back in? Do I put the X5 bushing in, which although better, still seem to fail around 30k? Or do you go big dollar and put a poly or monoball in its place?

Just some of the rats running through my head at the moment.

Thank you very much for the comments, we agree entirely.

 

[Lscman]

...........Case in point - I have thrust arm bushings that are torn. Do I put the OEM back in? Do I put the X5 bushing in, which although better, still seem to fail around 30k? Or do you go big dollar and put a poly or monoball in its place? ..........

Monoball is for severe duty track junkies who are willing to give up NVH qualities for tiny gains in track perfomance.

The X5 bushings are brute compared to the marginal M5 bushing. If you failed an X5 bushing in under 125K miles or 10 years, I'd be real surprised.

The huge tires/wheels, vehicle weight, off-road duty, 4WD and high center of gravity of the V8 X5 all serve to pound the heck out of their thrust arm bushings. These same bushings retrofitted on an M5 will be "complete overkill" from a durability perspective while still providing some BMW-like compliance for road isolation that a monoball will not offer. I personally feel that monoballs and other extreme hardware should be avoided on a big 4dr sedan. Corvette Z06 and Ferrari's don't even go that far. They simply don't belong on a sporty premium luxo car that sees 95% street. If we were talking a M3 weekend warrior vehicle for frequent track use, I'd consider them. Some will claim the monoball provides acceptable NVH, but so will and X5 bushing. The monoball has friction surfaces that will likely wear and rattle with miles. The X5 bushing has no friction wear surfaces.

 

[jetblack01m5]

I replaced my front thrust arm bushings at 70k miles and just put the OEM bushings back in.

Next time if I feel the need to replace the bushings with something other than OEM I'll use the bushings by Powerflex.

 

[Need4Spd]

I agree with Lscman. I am not being critical, but will note also that I think there are many variables and too few choices on the poll to yield much in the way of useful statistics, as there are too many suspension pieces that could fail, and too many ways to define "failure." I think worn thrust arm bushings have quite a latitude in terms of how you might describe them as "failed." Certainly, if you look under the car and see them torn, you can say they are failed. But it often seems there are smaller tears that can't be seen, or the rubber has deteriorated in a way that allows for some bump steer, steering imprecision or mild axle tramping upon braking that may go unnoticed for many miles or be blamed in combination on pad deposits on the rotors. As they don't always go away abruptly, you can drive for many miles just soaking up the failure by adjusting your driving to make more steering corrections. You don't realize how bad they are until you replace them with fresh ones.

Then there are shock failures (another wide variety; they are "failed" when they leak, certainly, but at what point are they "worn out"? Their effectiveness goes away slowly. How do say exactly when? When your car's slalom speed goes down by 1-2 mph?), ball joint failures, strut bearing failures and worn out wheel bearings.

But, to give it a try at helping out with some info, I replaced my thrust arms at 70k miles. I noticed an immediate increase in steering precision but the old bushings didn't show any signs of tearing or overt failure. The thrust arm bushings were part of a full arm replacement (Vines) that included fresh ball joints. I replaced my shocks at the same time. They were not leaking, but the ride and handling improved considerably afterwards, though some of that is due to the different design of my Koni FSDs. Since I replaced so many parts, it's hard to tell which of the old ones were the cause of the steering imprecision that I had gotten used to. Probably a combination of all these parts.

I recently noticed a low frequency rumbling sound out of my front end when the car is rolling, almost a sure sign of worn out wheel bearings (the other possibility is an internal belt or other construction failure of one or more of the tires, but the tread is relatively fresh and wearing evenly; I'm told that 80k miles for wheel bearings isn't that unusual, and for a good portion of those miles I stressed them beyond expected by running rear wheels and 275mm tires up front). I now have about 83k miles on the car and this is a rather recent development, so I'd say the wheel bearings are "failed" at this point and need replacement.

 

[Kmac]

Again, not to be repetitive or redundant , I specifically asked this question to understand, in a very simply manner, if these are design issues or wear issues.

My main concern is that by replacing the standard bushings with the more robust X5, I am going to cause a follow on failure.

I started another thread looking at this issue from the point of view that you have replaced the wear parts, then added and aftermarket suspension system. Did this increase/decrease/no change the wear parts B50 life?

You can definitely throw money at this problem. thrust bushings, control arm replacement, rotor replacement, caliper rebuild, guibo replacement, tie rods, alignment, wheel trueness, tire trueness, wheel bearings, etc.

ATM, for other reasons, I am replacing the rotors, pads, the thrust arm bushings, wheels and tires. I will have the flex plate checked as it is most likely has failed or is badly worn. The wheel bearings and tie rods are other things that will be check while they are there. Once I have invested this money, I would like to have some idea how long it will last.

Then, for pure upgrade purposes, I am looking at replacing springs/struts, but I became curious as to the wear effect that would have on the car. That is why I posted the other thread.

I have had the car since the beginning of the month, it has 85k miles on it and will be my highway warrior/daily driver with the M3 being the track baby. I have the maintenance records back to the inception date of the car, but have no idea how it was driven, so my instinct is to have a highly qualified tech (Wildturkeyman) check it all out - since he works at my local BMW dealer and owns an '02 M5.

Please keep the posts coming - you guys are great at this and I want more opinions and info on my theories.

Thanks again - Kmac

 

[Need4Spd]

My main concern is that by replacing the standard bushings with the more robust X5, I am going to cause a follow on failure.

I started another thread looking at this issue from the point of view that you have replaced the wear parts, then added and aftermarket suspension system. Did this increase/decrease/no change the wear parts B50 life?

I don't think upgrading to X5 bushings will cause any harm. Many members here have done that w/lots of miles now, with no problems. The Vines arms I have basically have upgraded bushings in them, but we'll see how long they last. The problem with a lot of this is that all of our cars are aging in the real world not on some test bed, so it's hard to predict what will happen to longevity until there is a failure or string of them some thousands of miles down the road. But by then, it's too late because either you will have done the same mods or not, and your car similarly will be thousands of miles older. The best we can do is identify a weak part and replace it with something that at least in theory should be more robust, and that because of the way it's hooked into other components, shouldn't cause follow on problems. The X5 bushing upgrade is one of those. It is far more robust in construction than the stock M5 bushing, the way it's implemented in the car shouldn't lead one to think it will cause failure of other components, and many members here report no problems with having them in over many thousands of miles. So this one is pretty low risk.

Other changes are harder to predict. But some can be guesstimated. If, for example, you put OEM rear wheels with 275mm tires on front, you will most definitely get better handling. But how much sooner will things like thrust arm bushings, shocks or wheel bearings wear out? Hard to predict. They most certainly will wear sooner, because there's no question that larger, heavier wheels/tires will put more stress/load on the suspension. But it could well be that the difference does not significantly affect component life to the point you would forego the mod in order to preserve longevity. My wheel bearings likely need replacement now, and I have 83k miles on the car. How much longer they would have lasted had I continued to run stock wheel/tire sizes up front is a complete mystery. I ran OEM rears for maybe 40k miles before going back to OEM fronts around 12k miles ago. I did that only because my car was the rare one (evidently) that ran into clearance issues with FSD shocks (the main tubes have a slightly larger diameter than stock shocks). Had it not been for the clearance issue, I'd have stayed with the OEM rears for the handling. The car pulled Gs like a racecar with those tires.

I very much doubt that other upgrades like shocks would reduce other components' lifespans, although they indirectly could if they caused you to take turns harder than you did before. But we drive our cars to enjoy their capabilities, not maximize component life. You pays your monies and youze takes your choices!

 

[Kmac]

+1

 

[Kmac]

80% after 50k - preliminary answer: Wear items not being taken care of. See Lscman's post for details.