A-Body Lowering ??? School me....

[FlatBlack4Life]

I'm trying to do some homework on lowering my 1970 Buick Skylark. I'm not too familiar with the geometry of lowering w/ consideration to weight of the car and performance. Skylarks weigh about 3400 to 3500lbs like most chevelles. Can anyone offer some suggestions to a nice suspension setup, ride height and wheel/tire combo that works for an A-Body too handles daily driving very well??.....Thanks....

[USAZR1]

I'm trying to do some homework on lowering my 1970 Buick Skylark. I'm not too familiar with the geometry of lowering w/ consideration to weight of the car and performance. Skylarks weigh about 3400 to 3500lbs like most chevelles. Can anyone offer some suggestions to a nice suspension setup, ride height and wheel/tire combo that works for an A-Body too handles daily driving very well??.....Thanks....

How much do you want to lower the car? What diameter wheel do you want to run?

[FlatBlack4Life]

How much do you want to lower the car? What diameter wheel do you want to run?
I would like to see what a 2 inch drop would look like w/ an 18 inch rim.

[TravisB]

I would like to see what a 2 inch drop would look like w/ an 18 inch rim.


Thats easy......you can either cut your existing coils or order drop springs and cut them to desired height! 18's are no problem!

[Blown353]

Factory front GM A body springs range from 15 to 18 inches free height. You don't want more than about 500 psi for a street car or it will be too stiff.

Just for the sake of clarification: spring rate is in lbs/inch, not psi.

Also, 500 lb/in is actually pretty darn soft on these cars. I was running 550 lb/in on my small block which was *too* soft. I'm now running 625 lb/in springs, and they're still too soft; I'm going to step up to 750 or 800 lb/in and see how they feel. The ride with the 625 lb/in springs is firm but not jarring, but they're still too soft and the car "porpoises" a bit on fast right/left transitions. If you aren't abusing the car in the corners they're just fine, and probably a little bit firm by many people's definition, but they certainly do not provide a harsh ride. Pairing them with decent shocks is also very important, a lot of cheaper shocks out there don't have adequate rebound control.

If you're just going to cruise the car with some occasional spirited turns and want good smooth road manners, I would suggest running about 500-550 lb/in springs for a SB car. I can't comment on good spring rates for a BB car. Rear spring rates between 150-175 lb/in are where the A-bodies seem to function best.

Also, an easy way to lower the car and also be able to adjust your height WITHOUT cutting coils is to hit up a circle track supplier and buy Afco spring jacks that sit up in the frame and then use Afco springs. You can get the springs in a wide variety of rates (cheaply, too) and then adjust the height via the springjacks.

Troy

[Derek69SS]

I don't have them installed yet, but I went with AFCO 5"x9.5" 700lb springs, and the taller height adjusters from speedway.

[Derek69SS]

Once you add poly bushings the ride is even stiffer. :D I'm putting solid bushings on all 16 control-arm locations :unibrow: ...this is for a car that will be 95% street, 3% drag, 2% road course. :_paranoid :willy:

[Derek69SS]

It may be too stiff, it might not be... I won't know until it's together and I'm driving it.

I'll post a full testimonial in June when I get back from driving it from Rochester, MN to Nashville, TN with the wife for our honeymoon. A little vibration might be a good thing :unibrow: :D

I will be running solid bushings in front with 700# springs and a small (if any) sway bar, and spherical bearings in the rear with 175# springs and no sway-bar. I'm currently driving on stock springs with big sway-bars and it handles OK, but not great. The ride way too stiff in the rear from the poly-bushings in the quadra-bind C4L. I'm actually anticipating a smoother feel, the bumps will feel sharper, but not as big.

[sinned]

Factory front GM A body springs range from 15 to 18 inches free height. You don't want more than about 500 psi for a street car or it will be too stiff. The wire diameter and spring height determine the spring rate.
Relax guys, I'm going to be nice because he obviously both new to the site and to cars in general.

Camino, if you are going to post technical spec or pretend to speak tech jargon you must first learn a little bit about what you are speaking of. Spring rate is calculated using number of active coils, wire diameter, and mean diameter. Free height never factors in to rate. As already stated, springs are rated in lbs. in.; not psi. 500lbs is pretty weak for most cars, even factory springs in newer cars are over the 500lbs. in. mark as manufactures have figured out that heavy rates do not equal harsh ride. I run a 750/175 combo and am going to up to 1000lbs. in the fronts (yes, I drive it everyday on city streets). Lastly, the two schools are not light springs/big bars and big springs/big bars, they are light springs/big bars and big springs/light bars.

Derek, you are going to need at least a 7/8" bar up front, the 700# just aren't enough by themselves.

[67 Camino]

I outta here. Go blow smoke up someone elses ass.

[sinned]

Hmmm, I thought I was very polite.

[Derek69SS]

Derek, you are going to need at least a 7/8" bar up front, the 700# just aren't enough by themselves.
I figured on running the stock 15/16" bar, but the AFCO lowers don't have any place for the end link to go. I thought I'd give it a try w/o a bar first before I go welding something to my shiny new arms.

I outta here.
Stick around, this really is a great place to learn, and an awesome place to hang out. The commeraderie is incredible on this site, and the cars... all I can say is "WOW" :yes: :unibrow:

There are a lot of opinions when it comes to anything technical, especially if there is more than one way to achieve something. With something as subjective as ride-quality, there will always be differing opinions.

Hmmm, I thought I was very polite.
You were a little rough on the fella. :_paranoid You offer good advice (I hope! because I've taken a lot of it :D ), but in a "don't sugar-coat it" sort of way ;)

[Mean 69]

Well, Den, I thought you were too, didn't see anything abrasive?

Just keep in mind, one spring rating for a given platform is not likely going to give the same response in a differnt platform, i.e. comparing a Chevelle to a Miata, Camaro, Mustang, etc. In all cases, the motion ratio of the various suspension designs will come into play, what really matters is what is happening at the wheel itself (wheel rate).

I'm putting solid bushings on all 16 control-arm locations

This statement caught my eye. Not a good thing for basically any street suspension, but CERTAINLY not a converging four link, like the early Chevelles, later model Mustangs, etc. These systems depend upon bushing compliance (flex, compression, whatever you want to call it) to allow the suspension to roll. Without bushing compliance, the system will look for something else to flex, it "has" to, and the "else" is comprised of the chassis, differential housing, control arms, and everything else in between.

A four link sytem, whether it is a converging tyoe (Chevelle system), or a parallel/less converging setup, is over-constrained mechanically. Period. The only reason they work in roll, in the real world, is because something flexes in the system (again, it might be chassis, control arms, most likely bushings if they are not solid rod ends).

Mark

[Marcus SC&C]

Flat black, we`ve done a lot of R&D on A bodys over the years. A simple combo we`ve had good results from starts with our Street Comp Stage 2 package. The A body stock geometry is pretty lousy and it has a lot of bumpsteer. The Stg.2 revises the geometry to be more in line with what you`d get on a modern performance car,improves the factory bumpsteer about 85%,which makes the car nicer and easier to drive hard and lowers the car about 3/4". Run this with a stock size front bar (you won`t need a big "band aid bar") and stock rear bar. With a set of Eibach lowering springs all the way around you`ll have about 2" of drop front and 1.5" or so rear. Finish it off with a really good set of shocks and you have a really nice driving car that handles very well and has just a little understeer to keep you out of trouble. Marcus SC&C

[Derek69SS]

Mean 69, I should clarify. My rear suspension will be all rod-end spherical bearings from wolfe racecraft, not solid "bushings". My front (already have the parts, so no turning back) will consist of AFCO lowers with rod-ends and SPC Adjustable uppers with solid bushings.

I really don't think the front will be much, if any, harsher than using delrin bushings. In the rear, I currently have all poly, and well, it's horrible to put it lightly. :rolleyes: I truly believe it will ride better when i'm done than it does now with the poly rear bushings.

[KAA]

I outta here. Go blow smoke up someone elses ass. That's your first post on this site?? Sheesh. :(

[FlatBlack4Life]

Flat black, we`ve done a lot of R&D on A bodys over the years. A simple combo we`ve had good results from starts with our Street Comp Stage 2 package. The A body stock geometry is pretty lousy and it has a lot of bumpsteer. The Stg.2 revises the geometry to be more in line with what you`d get on a modern performance car,improves the factory bumpsteer about 85%,which makes the car nicer and easier to drive hard and lowers the car about 3/4". Run this with a stock size front bar (you won`t need a big "band aid bar") and stock rear bar. With a set of Eibach lowering springs all the way around you`ll have about 2" of drop front and 1.5" or so rear. Finish it off with a really good set of shocks and you have a really nice driving car that handles very well and has just a little understeer to keep you out of trouble. Marcus SC&C
Hey, thanks to all you guys for your advice. Just reading this thread, I"ve learned quite a bit I didn't know. And Marcus, this was kinda just what I was looking for.....thanks man..... :hail:

[Marcus SC&C]

No sweat. :) Marcus SC&C