Increase G-body track width/decrease scrub?

[monteboy84]

Has anyone here done this? Obviously a stock front suspension with dish wheels has a nasty scrub radius, I'm exploring options to cut that down and run a deeper backspace wheel. I'm thinking the best option may be to relocate lower A-Arm mounts outward in order to maintain a reasonable (read: stock) length lower arm, realizing that I'll have to run coilovers outboard the frame and lengthen my tie rod arrangement. I'd also relocate my upper mounts outboard a certain amount to create the camber curve I want.

I don't mind the lengthened tie rod option, since I plan to run heim outer ends with an arrangement to adjust my bumpsteer. I also don't mind the idea of running coilovers, since it will be a better system with them anyway. I plan to run high-caster for stability and the negative camber gain while cornering.

Anyway, just wondering if any of you have experimented with this at all, hope I'm not too far off my rocker with my plans.

Thanks in advance.

ETA: I wasn't thinking too well about the LCA when I posted this, better plan would be to build a longer LCA to move the LBJ outboard, then move my UCA mount/pivot point outboard. This would work with either the stock spring bucket or the coilover setup I mention earlier. Anyway, let me know if you've had experience with any of this, I'm sure Savitske is the guy to talk to, I'm sure they've at least tried this?

[Norm Peterson]

The longer LCA is definitely the better way to go here, unless you were going to modify the length of the centerlink (not recommended).

Are you considering tall ball joints or other means of extending the vertical separation between the upper and lower ball joints?

Lengthening the LCA and leaving the UCA alone will tend to increase the rate of camber gain, while moving the UCA chassis-side pivots purely outward (no vertical component of relocation) should raise the front roll center minutely. Either change will affect bumpsteer a little.


Norm

[monteboy84]

Thanks, I'm looking into a couple of those items still. For vertical separation, I'm looking at 4x4 Blazer spindles (using 2wd hubs) which will function as a bit of a drop spindle, and I believe they are also taller than the G or S-10 spindle.

If I move the UCA outboard, and increase the LBJ to UBJ height difference, I will also increase the UCA pivot height with my new mounts, since I don't want much negative camber gain. I still need to pull the springs and mock the ride height with the wheels I want to run, in order to try spindle options and level the LCA's at my intended ride height. Once I get that sorted I'll extend my LCA's and figure my UCA geometry.

Am I on the right track here? I'm pretty new to this.

[Norm Peterson]

First thing you want to do is make sure that the camber gain is going in the direction that you want. I'm pretty sure that with the OE initial arm inclinations that the front RC is below grade and that the camber gain is +camber in bump for most of the suspension travel. I'm not sure what revising the arm length and lowering will do to that.

One thing to watch with drop spindles is clearance between the wheel/tire and the outer tierod end/steering arm. At about 4.25" backspace with a 15" wheel, the outer lips of the UCAs will probably start be the first points of interference (under combinations of steering plus bump), and this probably happens with 16" and maybe 17" wheels as well.

At a 18" wheel size, all of that stuff may fit inside the barrel of the wheels, at which time the wheel clearance issue may move to the front sta-bar or the LCA itself.

Investigate carefully!

For a PT car, you probably want some -camber gain in bump.

A dedicated dragstrip toy probably wants something else for camber gain.


Norm

[monteboy84]

First thing you want to do is make sure that the camber gain is going in the direction that you want. I'm pretty sure that with the OE initial arm inclinations that the front RC is below grade and that the camber gain is +camber in bump for most of the suspension travel. I'm not sure what revising the arm length and lowering will do to that.

Well, to have a negative camber gain, the UCA needs to be level or angled slightly upward with the LCA level, with an UCA that is shorter than the LCA. At stock ride height with stock arms, you're correct, the camber gain is positive, since the UCA's are angled slightly downward. By lengthening the LCA and keeping UCA stock length, it will increase my negative camber gain. Anywho, I'll have to look into what gain rate is most attractive for my application, I can tweak it later if my UCA brackets are made to be adjustable.

Thanks for the heads-up with the interference issues, I'll have to look it all over with the wheels I plan to run, they're 17's. With the LCA lengthened and a stock width S-bar, I'm hoping to have more than enough clearance, but I'll have to investigate to be sure. Measure twice, cut once as they say ;)

ETA: I am indeed focusing on PT with the car, drag racing doesn't appeal to me in the least.

[Norm Peterson]

Looking at those clearance issues again - the ones I listed for the 15" wheels are for stock G-body spindles. Drop spindles will likely get tight in different places at different offsets/backspacings.


Norm

[monteboy84]

Looking at those clearance issues again - the ones I listed for the 15" wheels are for stock G-body spindles. Drop spindles will likely get tight in different places at different offsets/backspacings.


Norm

I hear ya, I'm guessing the first places I'll see issue is with the tie rods and LCA's. I'll stick a hub/spindle assembly in a wheel to see what it looks like.

Is there a thread where I can see the specs on your Malibu?

[Norm Peterson]

I've never put together any sort of build thread for that car - there hasn't been any particular direction to the mods anyway. Basically I've just been tinkering with this car off and on since about six months after I bought it new in January of 1979. Virtually all of the work I've put into it predates my internet presence, some of it by nearly 20 years.

There is some really brief stuff in the "G-body Roll Call" thread in the Open PT Discussion forum, and I think I posted more information somewhere else, but don't remember just where. Might not even be here on PT.com.


Norm

[Norm Peterson]

I was right - it wasn't here. Wouldn't count for much as a 'Project Updates' build thread anyway, so maybe it should be called a 'build post' instead?


Chassis
Original F41 car with the braces
Extra nonstandard front crossmember
88A poly body bushings in most locations
Springs - Moog #5660 front (~640 lb/in), #5413 rear (~165 lb/in), not trimmed
Shocks - Bilstein HD, S10 front, G-body rear (IIRC)
Sta-bar, front - 32mm front, poly chassis bracket bushings, poly endlinks (the poly endlink bushings have been modified)
Sta-bar, rear - 22 mm
Control arm bushings, front lower - poly with the LCA bushings trimmed back just shorter than inner sleeve length
Control arm bushings, front upper - poly, unmodified, and they have squeaked since day 1
Control arm bushings, rear lower - poly, modified similar to the front lowers (and then some more)
Control arm bushings, rear upper - OE
Wheels - 15 x 8.5 x -13mm offset on all four corners, some trimming and other clearancing was required

Tires - currently mismatched SZ50 and g-Force Sports in 225/60-15. Nobody makes a street 245/50-15 any more. I cut down one of the SZ50's shortly after they went out of production and had to settle for the BFG's as being the best of the bad lot that remained (if this sounds a little like a rant, that's probably what it is )

Alignment - my own specs
. . . . . Street -0.7° camber, +3° caster
. . . . Auto-X -2.5° camber, +3° caster
If I was going to use just one of those settings for everything, I would set toe at 1/32" in for street and start at 1/8" or so out and experiment if I was going to completely dedicate the car for auto-X and trailer it to events.

Powertrain
355 w/Accel SuperRam, headers, own-design exhaust system, Tremec 3550, 3.73's, Auburn Pro Series diff, still 26 spline axles.

Body
Tunnel mods to suit the Tremec
A few patches - sills, lower rear quarters, floor, etc.

Paint
Mostly the original color scheme with the sills and pinchwelds blacked out and the original redline striping is all I'm going to say about it.

Other
Trunk-mounted battery
Cloth bucket seats from 1987 Nissan Maxima
Lightweight carpeting
Aftermarket tach and electronic speedometer installed in original locations


There really isn't a whole lot that isn't bolt-on at this point.


Norm

[monteboy84]

Thanks, sounds like a fun car.

[Norm Peterson]

It's been a lot of fun (and a bit of frustration as well) over the years.

Now that I'm not dependent on it for either primary or backup transportation for either of us, I ought to go through it one more time and build in a few of the more extensive chassis ideas I've had cross my mind.

Either that or pick off all the good parts for a different project entirely - and let my son take the remainder and run with it in whatever direction he chooses.


Norm

[driftinblzr]

I'm looking at 4x4 Blazer spindles (using 2wd hubs) which will function as a bit of a drop spindle, and I believe they are also taller than the G or S-10 spindle.

I don't think you'll be able to use a 4wd spindle without some fabrication. The lower ball joint points toward the ground, on the 4wd, compared to a G-body/S-series (2wd) spindle where the lower ball joint points up. In other words, the taper will be in the wrong direction.

Later, Doug

[monteboy84]

I don't think you'll be able to use a 4wd spindle without some fabrication. The lower ball joint points toward the ground, on the 4wd, compared to a G-body/S-series (2wd) spindle where the lower ball joint points up. In other words, the taper will be in the wrong direction.

Later, Doug

Thanks for pointing that out, I should have noted that I'd have to bore and ream the LBJ hole straight and larger, to accept a shouldered chromoly insert with the correct taper and direction for the GBody LBJ.

Well see though, it'd definitely be more work than using the newer 2wd Blazer Spindles....