An interesting malfunction. I got lucky it didn't damage anything.

[KfabR8]

I posted these two threads on RS6.com earlier today and decided to share them here too:

Just out running errands to day in my ride. Ran through a fun little road we call "The twisty road" at about 60%. Nothing serious, nothing slack.

Never hit any bumps or pot holes either.

Came to a four way stop intersection and waited my turn.

As I got rolling (fortunately I was being very relaxed about take off - just eased out on the clutch) the rear end suddenly had a very loose feeling - as if something had let go.

I throttled off and then gingerly rolled back into the throttle - yea, the rear end felt as if it were trying to steer a little bit.

HUH???

I wiggled the steering wheel a bit back and forth and the right rear side of the car seemed to wag much more than I'd ever felt.

I pulled over and inspected the rear end of the car - making sure that all the suspension components were okay. Seemed like all was good.

I visually checked all the bolts and nuts that can be seen through the rims and by laying on the ground under the back of the car. Nothing seemed out of place.

I then sat down and pushed on the leading and trailing edges of the right rear tire with my feet - the wheel wiggled. Uh oh!

I had a feeling that the lower rear link, that controls the toe of the rear wheels, had an issue.

Fortunately I was only about 2 miles from the Audi dealership that services my cars. I very, very carefully drove to the shop making sure that I didn't have any sudden input from throttle or brake. It kept the torque of the rear wheel on the bearing carrier/housing at a minimum.

Sure enough, the mount for the link had come out of the aluminum housing of the rear carrier. The nut and bolt were still in the bushing.

The bushing had worked it's way out of the aluminum casting.

Defect?
Just use and street abuse?

Not sure yet.

Audi's covering it - all warranty. (wouldn't expect anything less, as this is a part/manufacturing failure) They're red-labeling in a new right rear bearing carrier/rear housing. Hopefully it will be here by the end of the week.

I'm looking forward to getting my hands on these parts and inspecting them to see what caused the failure. The Mechanical Engineer and machinist in me has my curiosity running on high.

I'll try to get some pix of the parts and pass on what Audi tells me about the problem as I find out more.

Anybody else have this sort of failure?

I've been thinking about it - track cars, while seeing a high level of stress, generally see a smooth world. The loads are not shock loads, but ramp up and down as the car goes around the course. Throttle, braking, lateral loading are all factors that could attribute to a failure such as this, but in general, for a bushing that is tolerance fit into a cast part to get pulled out via these loads isn't going to happen.

So what about street use (abuse)? Streets are rough, nasty environments. There are always holes, ridges, cracks and such that jar the vehicle.

The streets around here are not to terribly bad and I'm so familiar with them that I know where to dodge and dart to avoid nasty stuff.

We just finished a 3,700 mile trip. I had a couple fairly major thumps given via road work and such, but nothing that would rip out a suspension component.

W/o getting to inspect the piece, I'll stand on the idea that I just happened to be one of the lucky individuals that got a slightly defective piece. (let's hope so).

I guess the only thing that really worries me about it is that, as far as I can tell, I have many more miles on my car than the average R8 owner.

It's the drivers like me, that get out and use their machines on a daily basis, in all conditions, that find the little engineering misses.

No matter how much testing the factories do, it's usually the consumer that ends up finding little nuisance things. (I've seen this happen in the motorcycle industry countless times)

I'll be keeping a very close eye on the left side now.

As stated, I hope this is a one-off issue.

[willyjp]

As stated, I hope this is a one-off issue

didn't Ti-Mike report an incident exactly like this in his (first) R8?

how about it, Ti-Mike?

(meanwhile, I'll search for the thread)

[willyjp]

Yep!!

go and get your car checked ASAP

"rear toe link failure"...."bolt ripped out"

interesting thing is: his ORIGINAL description post seems to be missing from the thread, but read the thread and you'll get the picture!

KfabR8: you should compare details with Ti-Mike. IF this is the SAME component involved in failure, I absolutely think you need to report this to NHTSA, or whoever it is that collects safety issues and issues recalls.

Audi probably wants to hear about that like they want a case of the plague! But IF this is a second incident (and WE DON"T KNOW THAT YET) of a specific component failure THAT WE KNOW OF just on this forum, it's a little scary!

That needs to be looked at hard by engineers who know what they're doing! Somebody could get hurt if the rear toe link rips out under other than the mild driving conditions reported in both stories.

[willyjp]

more research!
what we're talking about here:
http://www.r8talk.com/gallery/data/500/medium/rrend.jpg

the comment was made that:

Having seen the pictures before they were removed, it looks like the threaded part of the lower balljoint has fractured allowing the tapered joint to come adrift from the upright/bearing housing.Personally i think this has nothing to do with the car being tracked or hitting kerbs.--More like was overtightened (if its been removed previously?),but more likely just component failure due to a small defect in the metal.
Suspect just a one off.

Ti-Mike was roughed up a little by comments made about his "abuse" of the suspension of his car. Harrison said he wasn't going to worry until there was a "second instance."

Well, it kind of looks like we MIGHT have a second instance, and in a car that has had no (reported so far) track use. Unfortunately, apparently Ti-Mike pulled his pictures after he felt the gang didn't appreciate his contribution, but we really need his help now on this one:

TI-MIKE!! re-post your failure pictures and compare notes with KfabR8. If we have a pattern here, we need to know about this! Maybe it turns out you were unjustly accused (not by me!) of suspension abuse!

[KfabR8]

Because of the stink that was raised about Ti-Mike's ride being used on a track, bending wheels and such, please let it be known that my R8 has never and as long as I own it will NOT see a race track.

I know myself way too well and if I'm given the chance to put my car on a track, I WILL end up throwing the car away. I would have to push the car past my limits and that would end up in an off track, off road excursion. I have a desert race car for off roading and I would like to keep it this way.

My car has about 30,300 miles on it at present. Over it's life it's hit it's fair share of teeth rattling pot holes, highway seams and such. It's the life of a daily driver. I try to avoid as much of the rough stuff as possible, but anyone that's driven more than a couple hundred miles in their life realizes that you can't miss them all. They always make me grimace too. The **** highway seams can be some of the worst, as they sneak up on you quickly and too often there's nothing you can do but take the hit and then swear a lot...

The failure is the mount for the link that controls the toe. I'm not sure of the name. Some would call it a radius rod, others a drag link (wouldn't a drag link be be seen wearing a dress, high heels and lip stick?) and some would refer to it as a traverse link.

The link mounts to the bearing carrier/rear carrier assembly. The mount for this link is a pressed in steel cup of sorts that's not supposed to come out of it's aluminum housing. The cup is what pulled out.


Click on pic for a better view.

The shiny cylinder is supposed to be inside that piece of webbing just to the left of it.

[HovyR8]

Reminds me of the Q7 major failure story:

http://accident-audi-q7.skynetblogs.be/

[willyjp]

regarding Ti-Mike's issue, JOHN.KUSTARD said:

Having seen the pictures before they were removed, it looks like the threaded part of the lower balljoint has fractured allowing the tapered joint to come adrift from the upright/bearing housing.Personally i think this has nothing to do with the car being tracked or hitting kerbs.--More like was overtightened (if its been removed previously?),but more likely just component failure due to a small defect in the metal.
Suspect just a one off.

I'm not sure exactly what he's talking about here, but is SOUNDS like a failure that, while it produced a similar effect perhaps, was a failure in a place NOT PRECISELY THE SAME as what is pictured above. In any case, I'm not sure I would describe this 5th, lower rear suspension link as a "ball joint." It looks like a cylindrical bushing with a single axis of movement, but maybe the "ball" is just to the right in the booted housing? Be a lot easier if we could actually SEE these parts and get hands on!!

In the Audi tech picture I posted just before, the exact spot of KfabR8's failure pic is a little hard to see, but it's over on the right side rear susp. (you're looking at that from the left side of the car). Notice the upper "A" arm is just 2 links extending out to 2 contact points on the wheel hub carrier. But the lower "A" arm, rear leg, has a second arm just to the rear of it that meets the wheel hub carrier at a 5th, different point, just to the rear of the lower spring mount. That's the link that controls the "toe-in" of the rear wheel, and where that second lower arm attaches to the wheel hub carrier is where KfabR8's car failed....IF I'm reading his photos right!!

If only Ti-Mike or JOHN will come back and enlighten us, it would help!

If it's NOT precisely the SAME PART, then all we can say is, "well maybe those rear lower control links take a beating and that AREA is prone to failure. Possilby a suspension DESIGN issue, but NOT one that can be pin pointed to a SINGLE PART that is under-spec'd or prone to manufacturing defect.

Anyone else out there that saw Ti-Mike's original post and knows exactly where his failure was?

[KfabR8]

This comes from an off road suspension point of view concerning the design of the R8's rear carrier/bearing housing.

Why that is not in double shear is beyond me. That link, while not seeing the lateral loads quite like the upper and lower arms, sees a tremendous load during cornering. It's basically a tie rod like you'd find up front steering the wheels.

Since it's in single shear (only one side of the bolt is supported), the bolt will act as a lever arm on the location that it attaches to the aluminum assembly. It pushes perpendicularly on the bolt as it's stressed.

The rubber isolation should give enough that the stress that may arise during lateral stress should be dampened enough that it doesn't tend to tear the housing out of the end of the link or out of the body of the carrier. It would appear this is not the case in my point.

I really want to see the carrier off the car when they replace it to see if the hole where the bushing used to reside is ovaled or not. If is, the link was loose for a little while. If it's still round and doesn't have any signs of galling then it was a fairly quick removal from the carrier.

I can see this happening if the system were using poly bushings or heim joints (often called rod ends, or spherical ends), but the rubber isolation setup should take care of shock issues.

[James Knight]

Interesting and slightly concerning.

If you look at this



then what we Europeans call the toe link is the bit you can see adjacent to the rear arm of the rear wishbone which then extends to the hub, and controls the "toe" of the rear wheel (think of your feet/toes pointing in or out). With it compromised (play in the joints) or simply broken, then you will get rear wheel steer which is not ideal! In fact it's bloody dangerous to state the obvious.

Failure of toe-links is exactly the sort of thing that you'd expect to see occasionally on cars that have been subject to hard use on track, eg riding curbs or using stickier tyres (which subject components to higher lateral loads), as they are not designed to cope with the stress. Hence most road cars modified for racing will need significantly uprated toe-links.

The two failures on this thread seem exactly the same to me - though it's always hard to tell without inspecting the cars yourself. The fact this joint has now failed on a second car, and one without a history of hard use, is slightly concerning.

However lightning can strike twice, and I'd assume that this part was common with the Gallardo and LP560 and I'm not aware of any issues with those - though I could be corrected.

[willyjp]

Why that is not in double shear is beyond me.

not being an engineer, I kinda get lost there

how can you attach two pieces (with a bushing in between) together with a bolt if both ends of the
bolt are not "in shear"??

do you mean one end is rubber isolated and the other is metal to metal?

do we have steel to aluminum contact at this joint? (electrolysis?)
(being a long time sailor I'm very familiar with that!)

is the aluminum casting "in shear" in this joint? I seem to remember that one of the areas where aluminum falls down most in it's comparison to steel is in shear strength? (as opposed to tensile strength--not sure about that but something like that seems to be shimmering in my distant memory )

just trying to understand what exactly gave out here!