High Speed Front End Vibration - Causes / Symptoms. Let's Discuss

[ViolinARC]

I now have an intermittent vibration from around 65-80mph after replacing my thrust arm bushings. They were definitely worn out, and I replaced them with complete Meyle arms. I'm wondering if the vibration had always been there and because of the new bushings it can actually be transmitted to the steering wheel. It feels like an out of balance wheel/tire though, so hopefully an alignment and wheel balance cures it.

[StephenVA]

I personally think that the solid worm gear and center link applications tend to transmit every little slack or out of balance part right up the steering shaft or into our butts (front verses rear). On the rear suspensions/drive shafts, they have a lesser cushion mounts so they transmit that buzzzzzz all the way to our backsides.

Solution? New parts! Welcome to ownership of what were once high end cars. After all it is only money and our labor....

[pimp cauldron]

If you see a stock silver 540i with really ugly headlights give me a wave!

[R Shaffner]

I need to track down a front-end shimmy that can be real bad at 45 mph when the tires are cold. Wheel will shake noticeably. After everything is warmed, it will cruise at high speed pretty smoothly. (Slight vibration.)

I know the tires are contributing. They were worn unevenly from misalignment. I have a lowered '02 540-6 and had to drive to special shop who could do the alignment. (BTW, I had them give it M5 alignment which is GREAT! Not kidding. No more understeer. MUCH better than M Sport or other 540 alignment.)

I got this car 1.5 years ago so I think the suspension needs work. The shimmy is getting worse. I just don't know what the issue is yet and will start checking. Thx for all this input.

About persistent vibration in these cars that cannot be traced to the front or another specific location:

BMW uses a single universal joint in the drive shaft, along with a Giubo disc and a constant velocity joint. As I understand it, U-joints add a sign-wave motion with each half-revolution whenever they are not perfectly straight, which is much/most of the time. Most (perhaps the vast majority) of rear-drive cars cancel those vibrations out by using 2 out-of-phase U-joints, one at each end of the drive shaft.

In short, with most other rear-drive cars, the driveshaft can have a slight sine-wave motion where it speeds up and slows down a bit, but that motion is cancelled out and not transferred to the rear-end. However, in the e39 (or at least the 540 that I'm familiar with), there is just one U-Joint, so the slight sine wave vibration MUST be transferred to the rear-end whenever the driveshaft isn't perfectly straight. (The rear CV joint transfers that motion accurately to the rear wheels without cancelling it out.)

I wonder why BMW didn't just put a second out-of-phase u-joint at the differential.

[philly98540]

Agree, but he driveshaft is held straight or damn near close to perfectly straight all the time. The rear diff is fixed so it does not go up/down like a live axle car thus the driveshaft stays straight.

[scottieducati]

In my instance, I ended up doing the following (amidst other work) to address the various vibrations:

- Brakes (didn't fix, but helped on brake application)
- Front control arms (front wheel vibration vastly reduced, particularly the aggressive shake back and fourth.... I knew these were needed and already planned / unrelated to the rear end vibration I was feeling but they were needed at the time anyway. However the rear end stuff at times felt like it initiated shake up front, if that makes sense)
- Brakes (shop recommended, I acquiesced only b/c I'd used cheap rotors, this did not fix the problem but braking was again improved (b/c old rotors had sat and rusted a bit).
- After that didn't solve it (and I didn't expect it to and had said as much, but was happy to have the Zimmerman's on the car now anyway), I had the shop do my driveshaft with a new refurbished from DSI. I also replaced my giubo (even though it was visually OK) and went with the M5 (thicker / beefier) variant. This brought a definite and noticeable improvement in vibrations throughout the car....

But, now it is obvious that what I'm feeling (since the beginning, but most noticeable in winter) is really an axle CV going or "flat spotted." The boots are there and no cracks or leaks, and no play in them while they are installed. Also no clicking. But it is the "rear wheels feel flat spotted" at low speed when cold, and the rear end vibration at highway speeds (that can definitely reverberate through the car, it makes the steering wheel "vibrate" a bit but not shake at high speed / frequencies).

I haven't even had the new OE reman'd axles I picked up (fuck me, $$$$$$$$) installed, but I am confident they will resolve the issue. I also have new FAG wheel bearings all around waiting to go on, even though she rolls down the road coasting beautifully and the wheel bearings are more or less fine. At this point, w/ 170k, I'm happy to do the wheel bearings as preventative measure.

So all told, I shudder at the expense and frustration along the way. I should have done new axles when we did the wavetrac but admittedly hoped I wouldn't have to. I also should have been firmer with the shop that it wasn't the brakes after I'd already gone through two entirely different brake setups, and had just rebuilt the brakes on the car and braking up until then had been perfect and smooth.... but anyways.

Arguably doing the axles from the off and I'd still have the old brake rotors on the car and the old driveshaft on the car (because it had no play, and was overall in decent nick).... but now that I'm nearing the end of a full chassis restoration I know that I will enjoy many, many miles of buttery smooth riding. She's come good and had gotten better at every step along the way, even replacing some new but off-brand control arms and stuff.

I'll of course report back after next week when the axles go in and am sure I"ll be onto new troubles before long, but hollly shite these cars can absolutely have small issues that cause / relate to others and make it quite a challenge to track things down.

[R Shaffner]

Agree, but he driveshaft is held straight or damn near close to perfectly straight all the time. The rear diff is fixed so it does not go up/down like a live axle car thus the driveshaft stays straight.

Great point. But doesn't that beg the question about why BMW used both a u-joint and a CV joint? Neither would be needed if the drive shaft was always perfectly straight.

It would make sense to plan for a perfectly straight shaft, and then have some accommodation for it not being perfectly straight. (Like when an amateur like me installs it.) Or when the motor and transmissions mounts wear and flex.

I wish we knew a retired BMW engineer that could answer these questions for us...

[philly98540]

The DS is in two pieces to prevent vibrations and noise if the DS was all one piece. They use a u-joint in the center for simplicity and weight. There is no need for anything more there as there is minimal angle (joint is pretty damn near straight) to deal with here. For the rear, a CV joint is needed since there is an angle between the axis of the DS and the input into the diff so the CV joint cancles the cyclic rotational inputs to the diff here.

[Uturn540]

One issue that I have found that will cause a vibration is failure to lube the wheel centering up as per BMW when installing the wheels. Don't ask me why other than maybe the wheels just don't seat correctly. I had the same issue especially when braking. Had the tires rebalanced three times, since it started right after a tire service. Took the front wheels off to check all the components, every thing new, in spec, and tight, and when I put them back on I remembered the lube procedure for the hubs. After that no more vibration, go figure.

[R Shaffner]

The DS is in two pieces to prevent vibrations and noise if the DS was all one piece. They use a u-joint in the center for simplicity and weight. There is no need for anything more there as there is minimal angle (joint is pretty damn near straight) to deal with here. For the rear, a CV joint is needed since there is an angle between the axis of the DS and the input into the diff so the CV joint cancles the cyclic rotational inputs to the diff here.

OK. I get what you're say now.

For example, when I rebuilt a '60 Triumph TR-3 (decades ago) everything I read said to make sure to have the 2 u-joints out-of-phase. That was needed because the transmission output shaft and the differential input shaft were on parallel axes. So when the rear axle moved up and down, the angular deflection of both u-joints was about the same, so they would cancel out pretty well.

Here, with the e39, the rear CV joint is needed because the driveshaft and input shaft in the diff have different angles. There is a different angle (mostly little or no angle) at the u-joint in this case. So there's no sine wave motion to cancel out.

Thanks Philly. I got it now.

[whiteghost1]

One issue that I have found that will cause a vibration is failure to lube the wheel centering up as per BMW when installing the wheels. Don't ask me why other than maybe the wheels just don't seat correctly. I had the same issue especially when braking. Had the tires rebalanced three times, since it started right after a tire service. Took the front wheels off to check all the components, every thing new, in spec, and tight, and when I put them back on I remembered the lube procedure for the hubs. After that no more vibration, go figure.

Can you elaborate more on what the this lube procedure is please?

[scottieducati]

Anti seize around the hub and mating face of hub - wheel area.


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[Uturn540]

Not on the mating face, but on the flange that centers the wheel. Take a dab of anti-seize, lithium grease, silicone grease, or other lube on your finger and smear a light coating around the outside of the flange. It is actually a listed item within the brake inspection area on the Inspection I list.

[scottieducati]

I always use a thin coating on the hub up here in New England.... have had a wheel frozen / seized on a hub more than once!


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[whiteghost1]

Good suggestions, I’ve always struggled with my wheels sticking to the hub, will make sure to do this ASAP.

[citationav8r]

Ive been reading a lot of posts addressing the common front end shimmy/vibration but have yet to narrow down the cause. I have a 2003 540 sport that when I first drive the car, the shimmy begins at around 65 mph and gets worse when brakes are applied.. It stops above 75. The issue I have is that after the car has been driven for awhile, the problem decreases or sometimes goes away altogether.

[scottieducati]

FWIW I went round in circles chasing an annoying intermittent vibration. Definitely replaced thrust arms that helped, rebuilt brakes and did all that but it was still there.

It was my axles. Went with Genuine Remans and I’ll be damned if she doesn’t roll down the road like butter. Had 168k on the car at the time of replacement and presume both were original.


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[StephenVA]

I know this is not what you want to read but have you tried to clean the hubs BEFORE installing the rotors? This a big issue on many applications as a small amount of dirt/rust/junk on the hub will force the rotor and wheel out of perfect alignment which in turn cause a vibration at various speeds.

Takes just a few mins per wheel as all you need are these and a drill.

Next step vibration testing
https://www.motor.com/magazine-summa...ns-march-2018/