Need some help with 69 Z/RS front suspension. - Lateral-g Forums

GMJim · #1 06-30-2013, 11:55 AM

Hi Y'all
As I'm mainly drive train guy I've found myself at a loss to decide which way to go with some not so extreme front suspension upgrades. My level of expertise in this area is admittedly lacking! I've done a lot of searching and reading but still haven't had any luck deciding. My restored 69 Z/28 RS is bone stock with the exception of a healthy 350 and a 5 speed TKO transmission (original engine and transmission are resting comfortably) and I've recently decided that keeping the front suspension stock is going to kill me. The quick ratio steering box, long pitman arm and stock upper and lower control arms are fine for daily driving but at 70 mph on a tight corner the fear of swapping ends is very real! The lack of caster adjust-ability and light steering feel make this car very twitchy at highway speeds. I'm thinking new upper and lower control arms, and some 4 piston calipers would get me where I want to be. I may need to change the steering box and pump as well. I don't track this car but I do take it to the drag strip once in a while. Does anybody have suggestions? Before you ask about budget I'm a great believer in you get what you pay for but I don't think I need the best out there.
Thanks.

Vince@Meanstreets · #2 06-30-2013, 12:05 PM

Quote:

Originally Posted by GMJim

Hi Y'all
As I'm mainly drive train guy I've found myself at a loss to decide which way to go with some not so extreme front suspension upgrades. My level of expertise in this area is admittedly lacking! I've done a lot of searching and reading but still haven't had any luck deciding. My restored 69 Z/28 RS is bone stock with the exception of a healthy 350 and a 5 speed TKO transmission (original engine and transmission are resting comfortably) and I've recently decided that keeping the front suspension stock is going to kill me. The quick ratio steering box, long pitman arm and stock upper and lower control arms are fine for daily driving but at 70 mph on a tight corner the fear of swapping ends is very real! The lack of caster adjust-ability and light steering feel make this car very twitchy at highway speeds. I'm thinking new upper and lower control arms, and some 4 piston calipers would get me where I want to be. I may need to change the steering box and pump as well. I don't track this car but I do take it to the drag strip once in a while. Does anybody have suggestions? Before you ask about budget I'm a great believer in you get what you pay for but I don't think I need the best out there.
Thanks.

Hi Jim,

I'd go with the full DSE or Speedtech treatment with a 600 box. As far as the steering feel you can play with the alignment numbers.

**Sieg** · #3 06-30-2013, 12:48 PM

Jim,

My car was stock suspension when I started. I'm far from a suspension expert and may get corrected on a few points/options as there's numerous ways to to obtain improved safe geometry. I'll just touch the tip of this iceberg.

First handling modification move was firm and lower springs. HO Performance front and Global West leafs with 1" blocks rear. One of my next moves will be Global West's Cat5 bushing system in my leafs.

Second was firmer shocks Koni at firmest setting front, Monroe Gas Magnum rears.....remember these were done years ago.

The steering was stock and scary, aligned it to max caster which gave me an aggressive camber of -1 to -1.2, not ideal for the street. Next was having Lee rebuild my box to a quick ratio 2.25 turns and install the firmest valving. The valving made a huge difference.

Regarding control arms - You can keep the stock arms and perform the Guldstrand mod works, and add Howe tall ball joints and tie rod ends. (After watching the historic races yesterday, they all appeared to run the Guldstrand mod and stock arms due to regulations and some of those cars handle very well.) On the track it appears the weak part of the stock lower arm is the ball joint and bushing mount areas which can be beefed up.....depends on how hard you're going to push it.

SPC has a fully adjustable upper arm, and there's numerous quality "one piece" upper arms Detroit Speed, Speed Tech, Ride Tech, Global West, Hotchkis, etc. If you go with non-adjustable uppers and lowers don't mix & match manufacturers geometries.

Stock OEM spindles appear to get the job done and won't hinder getting decent brakes.

Brakes are another cookie jar of good choices, if you don't desire the brand names and appearance, Kore3's has kit's that cover most needs and work well, besides you'd like dealing with Tobin.

There's a lot of good info in Pozzi's site: www.pozziracing.com and Marc at SC&C has also provided a lot of good info to consider. There's so many good sources it really complicates the process. Personally I'm leaning towards modified stock in a Smokey Yunick kind of way.....easier on my budget and I like the old school method with my particular car.

That's just a little start, hopefully it helps in your quest. Don't hesitate to call if you'd like.

Or you could simplify and just have Vince "handle" it.

GMJim · #4 06-30-2013, 02:30 PM

Thanks for the replies Guys! I've been looking at the DSE uppers with the adjustable bushings for caster. Will the Speedtechs with the 4 degree caster adjustment built in be sufficient? I guess I want to run about 5 degrees + caster.

**Sieg** · #5 06-30-2013, 03:58 PM

The alignment man's ability to adjust the upper control spec is one feature I really like. No limits.

Here's a link to my last alignment with all OEM suspension components:
http://photos.smugmug.com/photos/i-L...L8stLjs-X2.jpg

Vince@Meanstreets · #6 06-30-2013, 09:19 PM

Quote:

Originally Posted by GMJim

Thanks for the replies Guys! I've been looking at the DSE uppers with the adjustable bushings for caster. Will the Speedtechs with the 4 degree caster adjustment built in be sufficient? I guess I want to run about 5 degrees + caster.

The built in caster feature you will want will be in the lower. It will move the ball joint forward to compensate. This will keep the rear of the tire away from the wheel well when running 4+ degrees.

GMJim · #7 07-01-2013, 12:00 PM

Thanks for all the info. This helps a lot. Seig, I haven't forgot about the new style BJ shifter. They are due in any time. I'll e mail you!

GMJim · #8 07-01-2013, 12:14 PM

Quote:

Originally Posted by Vince@MSperfab

The built in caster feature you will want will be in the lower. It will move the ball joint forward to compensate. This will keep the rear of the tire away from the wheel well when running 4+ degrees.

Vince
The speed tech site says the 4 degrees is in the upper? I see how it would be an advantage in the lower. Does DSE have this in the lower?

http://www.speedtechperformance.com/...prod/prd44.htm

**Sieg** · #9 07-01-2013, 12:39 PM

Quote:

Originally Posted by GMJim

Vince
The speed tech site says the 4 degrees is in the upper? I see how it would be an advantage in the lower. Does DSE have this in the lower?

http://www.speedtechperformance.com/...prod/prd44.htm

Jim - That's where it gets complicated, most likely due to proprietary safeguarding. It's also where Vince's experience becomes a real asset.

Vince@Meanstreets · #10 07-01-2013, 03:08 PM

Quote:

Originally Posted by GMJim

Vince
The speed tech site says the 4 degrees is in the upper? I see how it would be an advantage in the lower. Does DSE have this in the lower?

http://www.speedtechperformance.com/...prod/prd44.htm

I was hoping Blake would jump in here. I know there are some that add to the upper but that would be tipping towards the rear. Im sure he has some built in the lower to add to it.

Thanks Seig. Its nice to have different products in front of me to disect. Im a big fan of the Hotchkis lowers arms. All of my customers have loved them.