Suspension Questions

[JJRJR]

Guys, the guy restoring my car wanted me to run a few things by you. We're getting new torsion bars and going to go with the .96 diameter from Mancini. Also going to get new strut rods. One question is should I stick with the stock strut rods or get the adjustables? The adjustables are a bit more $$, but wanted to see if anyone has any thoughts.

OK, he said he's heard that we can really firm up the ride by "upper/inner fender support braces" and "lower radiator support brace." I don't know what either of those are, but hoping some of you have some experience with this.

Thanks much,

John

 

[A31PKG]

Adjustable strut rods will make it possible to fine tune the caster setting. Can't comment on the braces you describe...not sure how they would factor into the suspension?

 

[69hemibeep]

John, here is a thread from moparts with some suggestions http://board.moparts.org/ubbthreads/sho ... ost7003899

 

[JJRJR]

OK, so here's what we decided for suspension improvement and stiffening up the frame. Pictures attached of the lower radiator support and the inner fender braces. Already asked and no clearance issues with the front tires; pictures taken with front end bottomed out.

1) Torque Boxes - already installed;
2) Sub-Frame Connectors - already installed;
3) Adjustable Strut Bars - ordered from Mancini today
4) .960 Torsion Bar - ordered from Mancini today
5) Control Arm Stiffening Plates - ordered from Mancini today
6) New Front Sway Bar Kit - original was a little weary. Ordered from Summit today
7) Rear Sway Bar Kit - ordered from Summit today
8) Lower Radiator Support Brace - ordered today. See picture.
9) Inner Fender Braces - ordered today. See picture.

From a weight perspective, I think I'll still be net weight loss from stock considering aluminum heads, intake, headers, and fiberglass hood. Also, dropped off the rear today for a new set of 3.55 gears and a rebuild kit.

John













By the way, the pics of the lower radiator support and inner fender braces are not of my car, just examples of the product.

 

[A31PKG]

Very interesting...Your car should handle like a go-cart!

 

[sixgunrunner68]

With all of these chassis stiffening components maybe the 1.03" bars would be the way to go. Seems obvious that you want an above stock handling car.
:huh:

 

[JJRJR]

Thanks guys. Well, I've never actually driven a "stock" 69 RR. But, I'm told back in the day they were less than perfect in the handling arena. I'm doing this mainly to tighten it up as much as I can within reason. I've looked under the car and it's amazing how seemingly cheaply built these things were from Ma Mopar. Just want to keep it all together.

 

[ACME A12]

I've looked under the car and it's amazing how seemingly cheaply built these things were from Ma Mopar.

And yet they managed to withstand the pounding of a 383, 426, or 440. Climb under some of the tin foil crap built today if you really want to be amazed...

 

[Big John]

OK, you're serious about this.

Higher rate (stiffer, larger) torsion bars are going to cause more understeer. You already have a front heavy, understeering car with the stock suspension.

Before you go too much farther, it may be best to read up on suspension theory... what induces under/oversteer etc. But basically, stiffen the front (bigger t-bars, bigger sway bars) and you invite more understeer. Stiffen the rear and you have more oversteer.

 

[JJRJR]

Thanks John. Well, I've followed several blogs on this topic on other Mopar sites and this one and it seems that the people running the improvements I speak of are happy with the results. You are correct, I don't know suspension theory or even what over/understeer is. I thought I was doing a good thing by stiffening up the frame and getting T Bars a bit bigger than stock. Of the improvements I listed, what would you change?

John

 

[JJRJR]

John, you have me concerned. We are keeping he stock size sway bar up front and only going slightly bigger on the T Bar. Torque Boxes and Frame Connectors came stock on the 426/440 cars I think. Adding the rear sway bar should compensate for the over/under steer you speak of? The other improvements (lower radiator brace and inner fender braces) shouldn't effect steering as they are just meant to hold the frame together better.

Please let me know where you see the problem before I go adding all these parts.

Thank you.

John

 

[Big John]

We'll get a few definitions.
It helps if you're ever driven on ice and snow... LOL.

Understeer is just what it sounds like. You turn the wheel and the car goes straight. Cars that are heavy in the front will do this.

Oversteer is the rear of the car trying to pass the front. Rear engine cars will do this.

I best heard it put this way by a NASCAR mechanic. Understeer is when you hit the wall with the front of the car. Oversteer is when you hit it with the rear.
[youtube:1nr0efds]http://www.youtube.com/watch?v=lvOg2ydEY7Q&feature=player_embedded#![/youtube:1nr0efds]

 

[Big John]

John, you have me concerned. We are keeping he stock size sway bar up front and only going slightly bigger on the T Bar. Torque Boxes and Frame Connectors came stock on the 426/440 cars I think. Adding the rear sway bar should compensate for the over/under steer you speak of? The other improvements (lower radiator brace and inner fender braces) shouldn't effect steering as they are just meant to hold the frame together better.

Please let me know where you see the problem before I go adding all these parts.

Thank you.

John

Actually, that sounds pretty good to me. The rear sway bar will help with the understeer.

I might have read more into this then I should have. I saw some serious (and very good) mods and thought maybe you were going autocrossing or something like that. LOL. I see now that you are really looking to improve street handling and taking some time to stiffen the car.

Best thing to do is do some reading. There's a ton of stuff out there for free on teh intraweb or I suggest something like this:
http://www.amazon.com/Chassis-Engin...=sr_1_2?s=books&ie=UTF8&qid=1326496559&sr=1-2

 

[SomeCarGuy]

A lot of the sway bar companies will sell you a matched set of front and rear. What they consider to be a balance.