Rear Trailing Arm let go

[aromocki]

I just crashed hard into a wall a few hours ago (110 mph) because one of my rear trailing arm brackets let go. Its the bracket that wraps around the axle and attaches to one end of the trailing arm. I noticed that its design has it tack welded to the axle housing in about 5 different spots on either side. I am running 14" wide tires and 650 crank hp so I am sure its getting a work out beyond the original Panoz design specs. Just wondering if anyone else has had a similar problem? I thought these rear ends were supposed to be bullet proof?

Any info or advice would be appreciated.

I assume that if you welded a bead around both sides of this bracket that would likely suffice??

[PanozDuke]

With that power and wheel/tire combination, NOTHING is bullet proof. Ouch, glad you weren't injured.

If the welds broke, but the brackets did not fail- I'd guess a continuous bead would be much stronger. If the brackets failed and tore the welds loose, I'd consider the extra welding and heavier gauge bracket material as well.

I personally have not heard of this failure. There were issues with the mounting points where the four link bars bolted to the frame- the GTS's got the double sheer mount modification and I haven't heard of them failing once that mod was done. I have also heard of the arms themselves failing, but that has been on the non-GTS cars that had the smaller bars. Can not recall any GTS's having that failure. But with 650 hp? You and Brian are two of only handful putting that kind of power down through real race rubber. I would guess driving style may also play a part as crashing the curbs really hard and often might cause more frequent failures of such bits.

You are right that PAD never designed them for the level of performance you have. Even though they were built with a pretty good reserve of strength, you are in uncharted territory which is likely to require some upgrades. Many of us are following your lead in upgrading and are mighty interested in your findings.

Hope you get it back together, better than ever, soon. That transmission sounds great. Is the original drive shaft up to your power or have you upgraded it? I noticed today how small it looks.

Mike

[aromocki]

The welds are what failed and what was interesting is that the other bracket held when the first one let go and sheared a 3/4" bolt where it attached to the frame. So the brackets are clearly mounted well, it just seems like one of them let go for some reason?? I dont have the double shear bracket on my car, I will be installing one on the rebuild but the prior owner upgraded the bolts to 3/4" from 5/8" and I know that he experienced a similar failure in the past. I should have clued in when he provided me with a spare axle! I think what I will do on the rebuild is weld a continuous bead on both sides of the the bracket and that should add a significant amount of extra strength. The only theory that we have other than metal fatigue is that when we were checking the tightness of the trailing arm mounting brackets that the bolts were stretching and not providing enough clamping force.

I also checked the panoz manual and in the manual it doesnt say anything about torquing the bolts on the trailing arm brackets. Do you know if you are supposed to tighten them as maybe thats what broke the welds??

[aromocki]

BTW the G-force GSR Single Rail Refurbished Nascar Transmission I installed is an absoilute pleasure to drive. I really enjoyed it for the 5 laps that I had to use it. Definitely the best transmission I have ever used. Made my Tex 101 look like a dinasour. Very short throws and very crisp shifts, probably doubled the speed of my shifts.

[PanozDuke]

Don't know the torque on those, but I would use a high grade bolt (5 or 8 whatever is called for) and torque according to the thread and grade from a standard fastener torque chart.

I'm glad to know about the G Force trans. I am still using my ol' 3550. If it won't hold up, I'll definitely consider the G Force. Tom (Cobrafang) has recently gone to the Jerico and has had some throttle off popping out of gear. Might be a shifter issue and it will be looked into. I'm really not hard on the drive train as I just play rather than actually race. So far the 3550 has been fine, but with my new motor, it may not be.

Mike

[aromocki]

I guess I have to make a call when rebuilding the car whether it can handle the power as I read in some of the other posts that the rear suspension welds tend to aquire stress cracks which is not good. The welds failed on the trailing arm bracket but thats just one bracket of many that may potentially fail.

I will see how expensive the repair is but my powertrain is intact and the engine alone is worth about 30k, tranny 7.5k and not sure about the diff. Instead of rebuilding the Panoz I just may drop the powertrain into another car??

[Squerly]

Sorry to hear of your misfortune Aromocki but I'm glad to hear your OK. Bet that was a rather interesting few moments! How bad is the car?

[PanozDuke]

You've got such great development in your car at this point, it seems like the only potential issue is the rear suspension (may be the drive shaft). I'd think you could reinforce the mount points, upgrade the four link arms to chromoly and make sure the yokes, u-joints and drive shaft are up to what you are putting on the ground and be faster than anything this side of $75,000, unique, easy to work on, robust, predictable performance and beautiful. Not sure what you'd put the drive train in that would compete with all that and you'd have to go through all the teething issues again. Seems to me you are real close to having it nailed.

Mike

[aromocki]

Yup you hit the nail on the head, you are almost always better off with the Devil you know. The power train is bullet proof, and I mean bullet proof as the last tranny was crappy and I missed shifts constantly and over revved the motor and not a complaint at all. We fixed the hood flutter thanks to Brian and fixed some broken brake pedal linkages, tightened the entire car up, ascertained the perfect spring rates/ride height and are basically capable of taking down a 997 Cup Car. I already have beefier control arms, heims, forward mounting bolt is bigger as well on the trailing arms. I think the big thing I have to strengthen is the trailing arm bracket attatchment or simply have a preventative maintenance schedule on the rear suspension as Brian mentioned. The car is so easy to drive and so quick with an absolutely INSANE amount of grip in the corners. I also have a feeling that going to a lower ride height and stiffer springs caused the damage as notihing failed last year with the softer setup. So I think some of this was self inflicted. I am also more than happy to share all of my development with you guys in the hopes that anyone wishing to take their Panoz to the next level has some major failing points avoided.

The car took a pretty major hit and ripped the front left corner off of the car. It was a clean break and I htink my caliper is actually ok on that side. It crushed the headers, ripped a few mounting studs out of the block, sheared the driveshaft, and bent three rims. It only damaged the front left fender and nose though for body panels. The others are all ok surprisingly!

[boothkc]

Nothing is bullet proof and we have broken and reinforced just about every bracket on the car. We run 450hp (crank) so much less force.

I have broken the stock rear end (cracked input housing), those brackets (noticed the crack before it let go), and also the front Panhard arm gussets which even after reinforcement (PAD piece) still broke again. Not to mention spindles and various joints etc. At one point we considered changing the arms from aluminum to steel (available from Coleman), but kept new Aluminum just to have some give somewhere.

EVERYONE needs to really nut and bolt their cars often if you are pushing hard or have high HP etc. Up on a lift stress and wiggle everything and see what gives may suprise you.

The solution is to re-weld and reinforce. We have "eliminated" most crappy spot welds such as on the rear suspension mounts and front engine mount supports to name a few.

Glad your Ok, cars are fixable.

Kevin
GTS-GT2

[aromocki]

Thanks for the input. I think I will recheck everything and reweld what I see are weak spots to ensure that this does not happen again. I will do the inspection myself and outline what I want to my shop as they are clearly not on the same page as they typically replace stuff when it breaks but they do nut and bolt the car thuroughly. I will just have to develop a preventative maintenance cycle for the suspension components to ensure that they do not fail!

[NZGTRA17]

Originally Posted by aromocki

Yup you hit the nail on the head, you are almost always better off with the Devil you know. The power train is bullet proof, and I mean bullet proof as the last tranny was crappy and I missed shifts constantly and over revved the motor and not a complaint at all. We fixed the hood flutter thanks to Brian and fixed some broken brake pedal linkages, tightened the entire car up, ascertained the perfect spring rates/ride height and are basically capable of taking down a 997 Cup Car. I already have beefier control arms, heims, forward mounting bolt is bigger as well on the trailing arms. I think the big thing I have to strengthen is the trailing arm bracket attatchment or simply have a preventative maintenance schedule on the rear suspension as Brian mentioned. The car is so easy to drive and so quick with an absolutely INSANE amount of grip in the corners. I also have a feeling that going to a lower ride height and stiffer springs caused the damage as notihing failed last year with the softer setup. So I think some of this was self inflicted. I am also more than happy to share all of my development with you guys in the hopes that anyone wishing to take their Panoz to the next level has some major failing points avoided.

The car took a pretty major hit and ripped the front left corner off of the car. It was a clean break and I htink my caliper is actually ok on that side. It crushed the headers, ripped a few mounting studs out of the block, sheared the driveshaft, and bent three rims. It only damaged the front left fender and nose though for body panels. The others are all ok surprisingly!

Sorry to hear about the accident but thanks for posting on the cause. I will certainly be checking out the brackets on my diff very carefully.

Hope the rebuild goes smoothly and dont give up on the Panoz now that you have got it in such good shape!!

Kel.

[aromocki]

Unfortunately I will now be building a Transam legal/SCCA GT-1 car. The repair costs were quite significant on the car but more importantly the chassis needs to be reinforced for the power that I am putting through it. Remember that I have a 10" wider track as well and dont leave much on the table when I drive the car. I stress it quite badly. I am going to use the transmission in my GT-1 car but am going to sell everything else. So if anyone wants an all Aluminum 406 cubic inch engine with 6 hours on it I will let it go for $11k. The build cost is $30k.Any other parts requests will be entertained. I only damaged two body panels which is annoying!

[boothkc]

That is a good fun solution. We have flirted with going to a GTA type car for a while. The Panoz is fun, but really needs another 50-100hp (among others) to win in GT2 and this isn't going to happen. When I wiped out the front half of the car at T11 Infineon it ended up at about $40k to rebuild and paint the entire car. Essentially new but not cost effective. We seem to notice a new crack or broken piece 1-2x/yr and I think I'm asking alot of a 11yr old race car. Unfoturnately, they aren't really worth anything and I have too much into it to justify a change. So for now we keep ahead of the breaks and survive the next race.

Good luck and hope you keep us posted on progress and how you like the new car. Some of us may be there soon!

Kevin
GTS-GT2

[Werling]

I have interest in the 406 can you let me know about the bu ild on the engine, would like email at werling@aol.com Thanks Les