like the topice says. i am going to run a 17 x 11 wheel with dms springs. what will i need suspension wise to keep everything alligned? i plan on doing subframes, adj. panhard rod, lca brackets and lca's. what else would i need to do to keep everything ok without problems? thanks guys

thomas

 

that should do it....i have those and am fine

 

Im going with the exact same setup.

Are you buying the package deal from DMS????

 

i didn't know that dms was having a suspension package gp. i might look into that. i was just going to run bmr stuff.

 

why the LCA's?

The other stuff is nessesary for lowering (except for the SFC's but it's such a huge improment I wouldn't even question it) but what advantage will you find with heavier LCA's? Do you do a lot of drag racing? I wouldn't throw them out if I had them, but I'd definitely save my money for other stuff (like SHOCKs)

You'll need some Bilsteins, Koni, or Hal shocks. The DeCarbons are barely adequate for stock spring rates... lowering springs will feel pretty "bouncy" with the stock DeCarbons.

 

Why do you need to make any modifications to the suspension if the car is lowered? I don't know how much drop those springs provide though... I'm getting some Eibach Pro-Kit springs and I wasn't anticipating any problems that would require changing the suspension geometry. Will the car not align w/o changing the panhard bar and lower control arm bracket? or is it just a matter of having them be in the same alignment as when the car is at it's stock ride height. And, if that is the case, is there a noticable performance problem with not changing these parts with only a 1-1.5" drop?

Thanks,
Brian

 

when you drop a car, the angles of certain suspension pieces swing more towards the "compression" side of a stock alignment (liek all 4 wheels are going over a bump at the same time).

As a result, the optimum angles for motion control are "off" and things don't quite work like their supposed to.

LCA's for example:
At rest they should be horizontal (parrallel to the pavement, with the front joint bolted to the frame, and the rear bushing/joint mounted to the rear axle). The LCA's are designed to flex and rotate any direction, but should NOT allow the rear axle to move forward or aft in relation to the body (i.e. wheels shouldn't be in your back seats or slide back into your rear bumper). THey do this by swinging in a small arc, with the intention being to keep the horizontal component of motion minimal, while permitting verticle motion.

By dropping the body 1", you've just made the resting point 1" higher, and worse, given yourself an upward angle on the rear axle. So when you accerate hard, and weight shifts to the rear, the body mount lowers even more and you get into an angle great enough that it starts to pull the rear towards the front of the car... and rotate it forwards/down, at the same time the torque from the driveshaft is trying to toque it up/back. The LCA bushings just started to infringe on the job of the Torque Arm... making for a bumpy ride known as wheel hop.

This problem is exagerated by the fact that my TA, like most Fbodies, had slight upward-angles on the LCA's in stock form.

Obviously this system has to work the otherway as well... under braking, so it's not like you'd want to compensate for one or the other. The system is designed so that each componate controls a specific axis of rotation... two of which get "tweaked" by lowering the body (either with springs or with 200lbs sand in teh trunk... trust me, if your LCA's are messed up, extra weight at the drag strip will make hooking up HARDER, not better )



Lowering the car will typically cause:

- the LCA's to angle upwards... more (LCA relocation brackets)
- the rear axle to move to the driver's side a bit (adjustable PHR)
- a bit more angled tie rod ends (bump-steer kits are available for extreme drops such as 2" or more)
- lower roll center, and nessesitate higher spring rates as well (you'll need new shocks valved for the higher rates/forces)


So what's the advantage?
- lower roll center (less weight transfer under the same G forces)
- less ground clearance (meaning less air and up-force generated from under the car at high speeds, >140 mph)
- lower cross section area (1" x the width of your tires is now covered... hense less drag for Bonneville guys, again >140 mph )
- it looks pimp.

 

to answer you questions:

yes, your tire alignment will probably change (for the better).
no, you can do without a PHR for now, unless you have 315's out back

LCA bracket? ummm... depends how you dirve I guess. For any performance driving, yes you need the LCA brackets. People show ~0.1s improvement in the 1/4 mile just by installing them on STOCK height vehicles. correcting the alignment would be best.

Without changing anything you'll probably notice the car is a bit more "bouncy" (due to the already questionable DeCarbon shocks getting put through the ringer with higher spring rates), and you may get some noticable wheel hop if you try to launch hard. If you hear a washboard earthquake GET OFF THE GAS.

Oh yeah, and you'll probably pich up a little camber up front, so she may not understeer as much.

 

Thanks for spending the time on the explanation... And thus making me realize I was seeing things completely wrong. I was thinking the lower control arm relocation brackets were for the front which is why I was questioning the need for them. I see why they might be a good idea in the rear. I work for GM and I'm accustomed to calling those trailing links. I get wheel hop as it is so I probably am going to have to consider brackets to keep the LCA parallel with the ground. I just have the stock 275 on the rear BTW.

Brian