Rear Suspension Knuckle Failure Anyone?

[Smoky]

Edited to remove potentially confusing link

I will see if I can get some of the fix off our cars.

It is basically some small peices of metal cut to fit jut below the mounts to lengthen them and increase the strength.

In addition there are some extra welds put inside as the existing welds are very small.

I am not sure its a bad issue for the average car, but if you are hard on it (say have worn out a set of hubs or here clicking in your suspension when you backup and go for again) you should at least check for stress cracks in the paint or signs of rust under a crack.

About one in ten I have seen have signs, but most people I am around with Viper's, road race them.
I have often wondered in a hard pot hole could have the same effect in a extreme case.

We used to call Tom Francis for the metal pieces from X's, but we just cut our own on the street cars.

I will see if I can dig up the ACR-X bulletin with pictures.

Looking forward to the pics so I can take this to my local welder! Thanks so much for posting this!

[XSnake]

Just to confirm, is this the product people are using from Snakeoyl?

http://www.snakeoylproducts.com/prod...cat=341&page=2

No, this one:

http://www.snakeoylproducts.com/prod...cat=341&page=1

[Smoky]

Ok Thanks! I'll remove my links above to avoid confusion.


Is there an install writeup for that reinforcement? I would assume the installer needs a frame lift so the wheels can hang free, unloaded?

[FLATOUT]

Ok Thanks! I'll remove my links above to avoid confusion.


Is there an install writeup for that reinforcement? I would assume the installer needs a frame lift so the wheels can hang free, unloaded?

Smoky you can do that one in your driveway with a standard jack in less than 30 minutes.

[Smoky]

Awesome! Thx!

[LATAMUD]

Remove the wheel, remove the two bolts and the tie rod nut. Place the brace, reinstall the nut and two bolts, tighten. Install wheel.

[Smoky]

Remove the wheel, remove the two bolts and the tie rod nut. Place the brace, reinstall the nut and two bolts, tighten. Install wheel.

Sounds easy enuf. Will need to get these ordered before the season starts! Thx guys!

[commandomatt]

Its kind of interesting that there hasn't been more responses from those that think this is BS. On an older thread on VCA I got cut down for being concerned about this from several people, including track rats and even a dealer that said this was absolutely no issue whatsoever. It was a long thread and the majority of posters said it was caused by impact during the accident....not causing the accident itself. It was always blamed on poor driving. This even though the evidence pointed to a possible weak design

It pretty clear to me if there is even a remote possibility that this could happen, that this should be addressed somehow.

Nice to see how this thread is dealt with here on VOA. More open minded and responsive

.....yet another reason we are here....instead of there.

Matt

[ViperTony]

Is this something that can affect GenII's too? I noticed SnakeOyl has the bracket for the GenII: http://www.snakeoylproducts.com/prod...cat=341&page=1 I've already installed anti-toe brackets but that addresses a different issue, I think.

[n49]

Think this is another "swerve to avoid a deer" excuse.

If you could have been there to see the very low speed contact the motorcycle hit may rear wheel causing the knuckle to break, you would have been totally shocked. I was parked at the time. A 3 year old on a tricycle could have hit the wheel harder. No visible damage at all....when I moved the car the wheel went on the 45 degree angle. My fear now is any spirited diving as I fully believe this can cause failure of the knuckle. I am going to install the brackets, for sure.

[v10addiction]

I would think the Michelin full racing slicks help increase the likelihood of the control arm mounts cracking compared to street rubber. Very good idea to check them and even strengthen them if running R compound tires on the track. I'd like to see what updates were suggested to the ACR-X racers.

Cheers,
George

Yes, you are correct that the better compounds put more load, but its not the grip I see breaking the frames, its the bumps.
TWS has a bad exit off the straight and the load is unreal.

But you don't need R compounds to to get that kind of load on a track or the street.

The ACR-X's are extreme use vehicles and demonstrate in a short period what happens over time for the street cars.

Honestly, my street ACR had the cracks and never had anything meaner then the stock tires.
But I put a lot of track time on my street car on a known bumpy track.

I also believe just the right slide off a track will encourage the cracking or even finish it off.
I have been off the track, trying to hit the ragged edge more times than I won't to count.

Lets just say I can rebuild the splitter in my sleep now.

Nice to see you in here George!

[n49]

In addition to the rear knuckle failing (even on Gen IV's), the control arm mounts on the rears tear out with heavy use.

Chrysler pushed a mandatory weld upgrade on the ACR-X's after a failure at TWS occurred.
Granted the car had 1.5 seasons on it, but they felt it was an issue.

It is a minor job with a good welder, but my street car had the same cracks and I did mine as well.

I wouldn't drive a viper without both upgrades.

I never have been able to wrap my head around why the rear suspension is a front style suspension setup to begin with.

It seems like they could come up with a better design.
If you look at it closely, you can see the design encourages bump steer.

At least double up the knucles, giving you front and rear control of each wheel.
I think you would be hard pressed to break both.

I have seen an ACR-X first hand loose a knuckle, and it's not pretty.
The tire basically goes wherever it wants.

I was directly behind the car at TWS that the control arm tore loose from the frame ripping out, and that was downright terrifying!
First I thought the track was covered in oil, then saw the tire walking out of the wheel well.

When you say to at least double up with the knuckle do you mean add the bracket from Snake Oyl? As for the welding, is this a separate issue, or should this be done as well to prevent the knuckle breaking? Sorry....not very mechanically inclined here!

[AZTVR]

Is this something that can affect GenII's too? I noticed SnakeOyl has the bracket for the GenII: http://www.snakeoylproducts.com/prod...cat=341&page=1 I've already installed anti-toe brackets but that addresses a different issue, I think.

The logic of "better safe than sorry" would be the same, if cost is not an object. However, I don't remember any posts in the last 8 years about this issue related to Gen II failures. JonB would know more about that history. The upright design is definitely different. The moment arm related to the toe link attachment point looks longer on the Gen 3; but, the thicknesses of materials looks similar. Also, alloys may have changed. I wonder if the Gen 3 "light impact" (like n49's) failures and heavy impact failures fractured in the same location.

[cash84]

I had a little incident about 4 years ago. Hit a tree on the rear passenger side of the car. No damage on the car whatsoever but threw the toe off. Never broke. After like 5 track events later still hasn't broke. Never even thought that it had an issue til this was brought up..........

[ViperTony]

The logic of "better safe than sorry" would be the same, if cost is not an object. However, I don't remember any posts in the last 8 years about this issue related to Gen II failures. JonB would know more about that history.

I agree and I don't remember hearing/reading about the issue on a GenII either. At the very least it gives me a reason to wrench on my Viper over the winter.

[Garron]

I agree and I don't remember hearing/reading about the issue on a GenII either. At the very least it gives me a reason to wrench on my Viper over the winter.

The Gen 2 supports are a nice piece. No reason not to do it Tony. The cotter pin goes through the hole. (You will understand when you get them)

[ViperTony]

The Gen 2 supports are a nice piece. No reason not to do it Tony. The cotter pin goes through the hole. (You will understand when you get them)

Thanks Garron. It's on my TO DO list now.

[n49]

I just ordered the kit from Jon B (partsrack). Will now have piece of mind knowing that my rear wheel(s) won't suddenly go on the 45 degree angle during "spirited" driving!
And once again....knowledgeable, helpful & courteous service from Jon - Thanks again!

[FLATOUT]

I still want to see the updated welds for the ACRX cars That I would be very interested in doing.

[n49]

I still want to see the updated welds for the ACRX cars That I would be very interested in doing.

Same here...

[Garron]

I still want to see the updated welds for the ACRX cars That I would be very interested in doing.

Same here...

I would like to see what they are actually welding, the knuckle is aluminum and it is the piece that is breaking. I have brackets on mine, the rear knuckle looks very well supported.

[FLATOUT]

I would like to see what they are actually welding, the knuckle is aluminum and it is the piece that is breaking. I have brackets on mine, the rear knuckle looks very well supported.

I think it's reinforcing the control arm brackets (the welds).

[n49]

I think it's reinforcing the control arm brackets (the welds).

What would a control arm failure do? Would it cause you to lose control such as when the knuckle breaks?

[FLATOUT]

What would a control arm failure do? Would it cause you to lose control such as when the knuckle breaks?

Control arm doesn't fail, the welds that attach the bracket that the control arm mounts to cracks under extreme forces and fails. I think thats what was said. For those of you that don't know Texas World Speedway has a large banked oval section of the track where Gen IV Vipers hit 150+ and then come down off the banking into the infield track section. So if you're in an ACRX at 150mph you are generating 1100lbs of downforce and then you transition from a banked surface on to a flat portion of track at speed. That's a pretty violent transition and I could see any weak point being found with repeated exposure.

[Redsled]

Control arm doesn't fail, the welds that attach the bracket that the control arm mounts to cracks under extreme forces and fails.

This is correct. I have had this situation fail on (2) GTS race cars. One broke on the passenger front and the other on driver's left rear. The control arm does not brake, but rather the brackets that are welded to the frame. On both occasions the welds broke and the steering became very sloppy, I was fortunate that it happened on a slower portion of the track. Those brackets need to be boxed in and reinforced. Both cars were race cars utilizing racing slicks for many years. No visible signs until they actually cracked and separated.