Chassis "Band-aids" for Slicks

[jmimac351]

Originally Posted by NZGTRA17

Thanks Jim, I have a chrome moly supplier just down the road so once you have posted the spec I will get on to it.

Here is the chromoly tubing: Chassis Eng p/n MIS 1042 1-1/8" X .083

http://chassisengineering.com/shopDe...ProductId=1687

Here are the threaded, weld-in tubing adapters:

C/E3860 5/8 - 1-1/8 x .083
C/E3860L LH 5/8 - 1-1/8 X .083

http://chassisengineering.com/shopDe...ProductId=1572



We had an engineer friend run the numbers on the tubing and he said it is actually stronger than the "upgraded" aluminum arms. This size allows you to reuse the rod ends. You'll need to cut to length and weld the adapters in.

[Wess-RA]

Much appreciated, Jim

[jmimac351]

No problem. By the way, I've been reminded that the upgraded aluminum arms are 50% stronger than the stock arms and these chromoly arms are TWICE as strong as the UPGRADED aluminum arms. So they are quite an improvement in strength over stock GTRA spec.

[Cobrafang]

Thanks Jim for running it down.

Thoughts on this:

What about the idea that the Arms are a crush point? I know that chromoly is stronger but more brittle than some metals. I just wonder if you would be putting your mounting points at risk. Thoughts. Can your engineers do some analysis?

[NZGTRA17]

Originally Posted by jmimac351

Here is the chromoly tubing:

Thanks Jim, much appreciated.

[jmimac351]

Originally Posted by Cobrafang

What about the idea that the Arms are a crush point? I know that chromoly is stronger but more brittle than some metals. I just wonder if you would be putting your mounting points at risk. Thoughts. Can your engineers do some analysis?

I can't speak to that. Our concern was to prevent the arms from twisting when we put the spurs to these cars with more power. I think most of the issues have been with the arms and more hp. I don't plan on wrecking the car but I do plan on adding hp so that was the concern. I've seen 3 different mounting configurations - 1 with the rod end mounted to a threaded bung on the chassis, 1 with a thin walled box setup for that mount (what I have) and 1 with the same box design but with thicker walled material (what you get when you order the box upgrade material from Panoz). Not sure whether that thicker walled material is on other GTRA or GTS cars or if it's just the metal they had when they made these retrofit pieces. My buddy got them when he ordered the chassis upgrade pieces from Panoz. I don't know whether these chromoly arms are stronger than the boxed mounting points. In a wreck I suppose all bets are off anyway.

[Wess-RA]

Tom, I had mentioned that that was the comment from Panoz. But how strong is to strong or too weak for that matter. Too weak is easier to determine based on various cars h.p.. (I have decided that with my wimpy 245 hp, that I am fine for now). However if I were to back into a wall and had the strong torsion arms-what is too strong to not do frame damage?. I think it is fair to assume that the 5/8" thread would break before the steel arms, so theoretically there is still an engineered failure point. It would be good to know the strength comparisons between the 1" arms, the 1 1/4" arms and the 5/8" and 3/4" rod ends. Elongation and compression. Easy materials engineering stuff if someone has the engineering buddy with the material specs. Blah, blah, blah! Just rhetoric-no useful answers from me!

[panozracing]

I got a question....whats the weight diff. between the steel and the aluminum. When I called coleman and asked about their steel arms they told me they are thinner wall than the aluminum and weigh slightly more but have the same bending specs as the aluminum 1.25" so I went with the aluminum.

[Wess-RA]

Jim, I just read yours-The rod end bolted directly to the bung, welded to frame was the premod configuration (speaking for the RA's)-see my pics posted earlier. The thinner walled "box" (posted by Eric below) were done by someone other than Panoz (I had sent that pic to Josh at Panoz-he claimed that that was not their work) The thicker walled "double shear bracket" is found in the Panoz parts manual pg. 20 P/N GTs3-1431. I just bought a set. I am told that I should be using the same bolts. Sounds weird to me as the bolt heads tighten down onto the bracket. I would have expected a longer bolt with a bushing to sandwich the rod to the frame, with the bushing taking up the difference to the bracket. Using the original bolt, the way Panoz instructed me, would leave the rod end floating between the frame and the bracket. Something is wrong with that concept.

[jmimac351]

Brian, the chromoly arms I have, cut to length with the tube adapters welded in, weigh 3lbs each without the rod ends. Not sure how much the aluminum ones weigh.

Uwe, I agree that no bushing sounds weird.

[Wess-RA]

Anyone else have bushings? Eric in your pic I can't tell if its a bushing as the color is the same cadmium plating on the bolt head. The bracket is bent a bit under compression. That indicates either no bushing or too short of a bushing.

[Wess-RA]

I reposted this pic just to complete the loop. I know there are at least 6 school cars out there with this issue. Maybe more! The mechanic at the school from which I bought the car stated that it isn't an engineered weak link, but rather the "previous" schools way to solve a bump steer problem. By raising the connection point it effectively put the steering arm articulation closer to the same arc as the suspension articulation. If this was their "quick fix" to that problem I have to wonder how the bump steer is on the cars without this poor alteration. Have you guys had bump steer issues with the full thickness arms? If so, what better solution did you come up with?

[Wess-RA]

I know I'm beating a dead horse here-but there are several cars out there that need to cross this bridge if they put slick and engines in their cars.
I had a short interaction with the design engineer at Panoz. I would take his word as gospel on these issues:

• The front steering arms (P/N GTR8-5024 and 5025) should be exchanged for their thicker ones-he knows of no bump/steer issue. Mystery as to why the school did this mod to several cars. Dangerous at best!
• The rear double shear brackets (P/N GTS3-1431) are important. After welding, they should mount so that there is no spacer (bushing) needed. It should be a tight squeeze-possibly necessitating bending back the bracket to install the Rod ends. This is dependent on how much heat the welder uses (suck in as a result of deep penetration) Some of the pics I have seen some of your postings indicate that they are not "Panoz" parts-I am seeing gaps between the rod ends and the bracket. I can't tell if you are using bushings-I guess I have to assume you are as they wouldn't be working otherwise)
• The 1" Trailing arms did fail (as some of you have attested to) the 1 1/4" arms haven't failed on the GT hp cars (around 450hp) There is no data available (at the factory) on owners mods who have used the 1" steel arms with the original 5/8 thread rod ends.

There you have it straight from the factory engineers mouth (paraphrased of course)

I might be the only one who cares about this issue as most of you regular posters have this resolved already. It's lonely out here.

[Wess-RA]

OK, I'm raising this topic again from the grave. My GTS car doesn't have the rear trailing arm strengthening brackets. I'll be installing those.

When I called PAD for new trailing arms and hardware, they stated that all GTS's came with the new larger dia. trailing arms. I just measured mine. To my surprise they were 1 1/8" dia. What gives? I thought the non-upgraded ones were 1" and the upgrades were 1 1/4". Does anyone else have 1 1/8" arms?

[bobg416]

Mine are 1-1/8 and came from PAD...I think all of the upgraded arms are 1-1/8 not 1-1/4.