Deamon2002

iTrader: (3)

Just like the title says, I have read and read and can't get a decent answer to quench my hunger for knowledge. I do not want to lower my car, due to the body kit, so stock ride height is a given. I would like to upgrade my LCAs and PHR first off, but I'm not sure if I should get adjustable or non adjustable. I know I want both poly ends on everything as I'd like some civility to the ride. I have a little rear end clunk I believe is the suspension as well. Also another question. After I install these I should get everything aligned, correct? After this will come some sub frame connectors and about a year from now new shocks and possibly springs, but we'll get to that in a year. Thanks for all the help guys, I think it's time for me to let the search engine cool down a lil.

JasonWW

iTrader: (2)

I think you may have heard some misinformation. The PHR is not usually loaded and rod ends are highly recommended there. Getting all that slack out will really help the rear supension to feel tighter and more nimble, which is good. They should also last a longtime.

Now the LCA's are under a lot more stress all the time, so rod ends will make the ride rougher. Poly does have some more give in them so the ride shouldn't be as bad as rod ends, but they have a another problem. Due to their inability to flex much, they don't allow the LCA's to twist like they should. This can create bind which won't allow the rear axle to move up and down as easily while cornering. If you don't care about cornering, then the poly/poly LCA's should be fine. Really, the factory LCA'a are pretty good as far as ride and handling is concerned. I would wait and change them out last. Or you could replace the bushings in the stock arms with MOOG units. They are supposed to firmer like the 1LE bushings.

I'm looking into making a rod/rubber LCA. They seem to have the best of both worlds.
http://frrax.com/rrforum/index.php?act=ST&f=3&t=3553&

Deamon2002

iTrader: (3)

OK, so what your saying is, rod/rod combo on LCA, WILL affect ride quality?

JasonWW

iTrader: (2)

I don't know from first hand experience, but yes. Everybody says they will make the bumps feel more sharper. Imagine the LCA's as they go down the road. When the tires hit a bump, the car will want to continue forward, while the tires and axle will want to stop due to the shock valving as well as the spring tension. The wheels and axle WILL move up or down, but the factory LCA bushings absorb some of the bump or dip impact. Remember that the job of the LCA is to center the axle front to rear. When you get rid of the rubber, those impacts will feel sharper and the NVH (noise vibration and harshness) will increase. That's why it's probably better to replace the LCA's last as there are a lot of other things that can make the car feel better.

Oh yea, I forgot to mention. It is entirely possible for you to make your own LCA's and PHR. Rod ends can be bought from Jegs for $30 ea. tubing can be bought from Coleman for $12-$25 and the step bushing can be bought from Cal on these forums. You can make the PHR for about $95-$100 and the LCA for about twice that price since it's just like making 2 short PHR's.
http://www.jonaadland.com/Z28/Mods/L...minumLCAs.html
http://www.jonaadland.com/Z28/Mods/PHB/AluminumPHB.html
http://frrax.com/rrforum/index.php?a...=3&t=1491&st=0

BADZ

iTrader: (5)

I would go adj. The tubular stuff is not as strong as solid billet...

JasonWW

iTrader: (2)

I would think the tubular would be stronger due to it's larger diameter. I think most of the aluminum sections are hollow tubing, not solid. Still, It's not about strength. They are all plenty strong, it's more about what type of ends you want. On the PHR, you need adjustable to keep the axle centered. You may not need it now, but if you lowered the car then it would help, plus the stiff rod ends do help with handling feel.

You don't really need adjustable length on the LCA's unless you weld in relocation brackets wrong or something. If you do get the ones with adjustability, just set both LCA's to the same legnth as the factory arms.


It's not necessary to get the alignment checked after installing these parts. The PHR will not effect it at all. The LCA's have the potential to affect the rear axle alignment, but if you keep everything the same length you should be fine. If you were really worried, you could get the car 4 wheel aligned and explain to the alignment place that even though your car only calls for a 2 wheel alignment, you want a 4 wheel. They should do that.

Setting the length pic below.

BADZ

iTrader: (5)

No, solid anything is stronger.. When you cut 1.2x - 3x 60ft's!!!! its nice to have that extra strength..

Deamon2002

iTrader: (3)

Thanks for all the input guys it has helped out a lot in my decision. And I did decide to go ahead and get adjustable LCAs and PHR, because I was getting a good deal on them. Strike while the irons hot I suppose, plus the wife rarely says "OK, get your parts". LOL.

Jon A

I would just love to hear the technical reasons as to why from the Ebay Engineer.

JasonWW

iTrader: (2)

I'd like for you to get technical about this stuff Jon, but still, "Ebay Engineer"?
That's not very cool.
UMI sells on Ebay as well.

Jon A

What's not cool is misinforming people for one's own personal gain. Be it purposely or out of ignorance, the result is the same.
From his ebay listings.

If he'll admit this misinformation was due to ignorance and he wasn't knowingly being dishonest, I'll be glad to apologize for the Ebay Engineer comment.

orangeapeel

iTrader: (18)

Just weld some steel over your stock ones. then they will be partially "boxed" and you will still have the stock feel for obvious reasons.

my $0.02

JasonWW

iTrader: (2)

I don't think you'll fell any difference at all, so what's the point?

orangeapeel

iTrader: (18)

Who knows really, that was why i havent wasted the time to do it. But if you think it is going to help...ha why not? that is normally a cheaper alternative, and half the time people are looking for that approach to their cars anyway.

BADZ

iTrader: (5)

You don't have to apologize, you're obviously an idiot and don't no nothing about tensile strength of solid vs tubular.

Definition: The maximum tensile load sustained by a specimen during a tension test, divided by the original cross-sectional area. The maximum engineering stress sustained. In SI, results are expressed in kilograms per square centimeters of area.

Jon A

Gee, I guess I don't no nothing about that? Here are some questions for you. Since I knew you wouldn't be able to answer them and I'm suuuch a nice guy, I went ahead and answered them for you. You're welcome.

1) Tell me, how does the increased tensile capability of the section increase the strength of the overall part when both sections' capability exceeds that of your rod ends by a large margin?

Answer: It doesn't. The part is only as strong as its weakest link.

The commonly used 1.125 X .219 wall tubing has a cross sectional area of .622. At an ftu of 42 KSI that's over 26,000 lbs tension capability.

Your 1" solid section has a cross sectional area of .785. This results in a tension capability of close to 33,000 lbs.

[Note, that's ignoring the location at which they'd actually fail--the hollow space at the end of the shank of the rod end where the area will be .480 giving only a 20,000 lb capability (You didn't really think it would tear in half right at the strongest part in the middle of the solid section, did you?) but I'm feeling generous tonight, it doesn't matter anyway...see below.].

The ultimate static radial load capability of a 3/4" QA1 XM or equivalent rod end is about 28,000. This means a part made from the tubing using these rod ends has an ultimate tensile capability of about 26,000 lbs.

But a 5/8" rod end (the size you use) QA1 XM or equivalent is only good for 18,000 lbs. So your part will be limited to 18,000 lbs with those rod ends no matter if the center section was 2" diameter solid steel.

So the tubular part with 3/4" QA1's is about 44% stronger in tension than your parts--and that's if you used QA1 XM's or an equivalent. It's very possible (given your prices) the particular rod ends you actually use have a much smaller load rating, further weakening the parts.

2) Exactly how much tension stress are the LCA's under during a launch?

Answer: Less than zero. It's a negative number denoting compression.

As entertaining as the above was, it's really academic as neither part is likely to ever fail in tension due to non-crash loads. So now we get to the good stuff, compression.

3) You recited a definition from somewhere for tension, is it the same story for compression?

Answer: It would be if the parts were only a couple inches long. But they're not. They won't suffer a pure compression failure. Under too large a compressive load they will buckle.

4) How do you calculate that?

Answer: For these purposes, a simple Euler buckling check is more than sufficient. The equation for that is Critical Load = pi^2*E*I/L^2. The only variable that changes here is I, the Cross Sectional Moment of Inertia. The equation for that for a round section is pi*r^4/4 for the outside radius, minus the same for the inside hollow radius if the part is hollow.

This gives your section an I of .049 in^4. The "flimsy tube" noted above has an I of .068 due to its larger diameter.

Thus, the "flimsy tube" can withstand a force 39% larger before it buckles. For the LCA's this amounts to about 18,000 lbs vs 13,000 for your parts.

So as you can see, not only are your parts weaker in tension, they're also weaker in compression. They're simply weaker.

That's still rather acedemic as even 13,000 lbs is quite strong and one would be hard pressed to fail even your weak LCA's in compression.

Where it makes a very real difference is the PHB. The "whimpy tubular" is good for only about 3700 lbs. Yours is good for about 2700 lbs. That's a difference that hits home. An F-Body with sticky tires, under the right conditions can put around a 1500 lb sustained load on the PHB during cornering. Add a little for spike loads caused by bumps mid-corner, etc, and you can see the 2700 lb capability has virtually no safety margin left.

For this reason I would not recommend anybody (besides pure drag racers) use your PHB. It just isn't strong enough. The much stronger "flimsy tubular" one is the minimum I'd recommend (and I use it myself with confidence). Anything less than that is asking for failure to put you into the wall when you least expect it.

Here endeth the lesson.

JasonWW

iTrader: (2)

So basically, the 1/8" larger diameter of the hollow tubing more than makes up for the added material in the center of the solid arm, at least to prevent buckling, right?

I think BadZ was comparing arms made of similar diameters with only the difference that one is hollow and one is solid. Only then would the solid arms be stronger. That's what I'm guessing. I don't want to speak for him.

It almost makes me want to get some tubing in 1.5" or so, just to over build everything.

Since we are getting technical, how much of the rod ends load is on it's threads and how much is on the jam nut threads? It looks to me like the thicker the jam nut, the better. Any comments on that?

ßlackßeard

This is way too much fun to read... Jon A, good for you. I second his math, and not that you need it to know this stuff but I have degrees in Mechanical and Manufacturing Engineering and currently practice engineering in the automotive parts manufacturing industry. To really hammer home though, look what the guys who actually race use and trust their lives and cars to, and that should solve any doubts. Anybody here pulling 1.3x 60 foots, running 9.xx ETs at 150 mph... what are you using? The guys I know are all using BMR tubar PHB and boxed LCAs or tubular LCAs.

Just my 0.02.

BADZ

iTrader: (5)

Sorry guy's, I don't need to sit here and wright a biography on our pieces, We will keep making them for the custom (serious drag racer) applications and you guy's go and buy your street setup...We don't only build for late model applications, we build for super gas etc. You are right Jason, I'm only comparing apples to apples and not oranges....Like I said before, Solid may be an over build but I don't use tube for nothing...

Jon A

Exactly.
Uhmm...you asked:
He answered:


That gets pretty difficult to predict since it entirely depends upon the preload the user puts on the jam nut, and since you can't really use a torque wrench to do it.... Basically you always want the threads of the rod end in tension and the jam nut in compression against the bar regardless of load--or the jam nut is going to come loose. As the load switches direction, they sort of trade load back and forth but both keep some. Sort of hard to describe. Anyway, especially when using a steel jam nut, it doesn't need to be thick. A thicker nut takes up too much space and can leave you with too little thread engagement between the rod end and the bar. Regular sized jam nuts are all that are needed. And yes, keep them tight (wrench flats help for that a lot more than knurles do ).

Glad you enjoyed it, BlackBeard. Do you think the guy understood a single word I said? I wonder if he'd sell us a "solid bar-frame chassis"?