Shim thickness for Guldstrand Mod

[cornfedbill]

I am planning to perform the Guldstrand Mod on my '74 Nova Hatchback the hard way by removing my upper mounts, trimming them and then re-welding them back on the frame. I am contemplating moving them inboard a bit to reduce the thickness of the spacers needed to get the correct camber.



For anyone running the Guldstrand mod, what is the total thickness of spacers you are running on the upper control arm?

Thanks!

[fast98]

Even if everyone gave you some numbers it wouldn't help you. Every car is different, the frames aren't all the same, the control arms aren't all the same. Best bet is to measure your own car and go from there.

[cornfedbill]

Thanks. Maybe I can clamp the upper control arm in the new location to estimate the camber.

I know that the G-mod often requires a lot of shims. I am hoping to move the upper mount to minimize the shims. I was thinking of moving the mount inboard about 1/8" when I relocate it. I just don't want to go too far.

[TheBandit]

Do you plan to ever run aftermarket control arms or cross shafts? If so, I don't think I would mess with it. There are a lot of variables to consider. For example, different ride heights will determine the control arm angles which will necessitate different shimming to get the same static camber.

Here are a couple of threads that may be of interest to you:
https://www.pro-touring.com/showthread.php?78054
https://www.pro-touring.com/showthread.php?81498

[cornfedbill]

Thanks. You are probably right.

If I cannot lay out the front suspension before I begin to cut, it may be best not to move the mounts inward.

Thanks for the links. Good information!

[TheBandit]

If you make a jig like what I used, you could add spacers when you make the jig on the original frame, then remove the spacers when you re-position the towers. That would give you the moved-in geometry and you could tack it in place, do a rough alignment, and see where you stand. If you don't like the change, put the spacers in and weld it up in a position that doesn't move it inboard.

I would be a little worried about moving them in because while you can easily add shims if they are too far out, you can't take away any more shims once the cross shafts hit the frame.

[68Formula]

I've seen a number of stock frames with tons of shims (mine included). Especially closest to the firewall. If you move the front one in 1/8", and the rear 1/4" (firewall) on each side, you will still have plenty of room to adjust some additional camber and toe. Without requiring several (and I mean several) shims.

[Rod]

I've seen a number of stock frames with tons of shims (mine included). Especially closest to the firewall. If you move the front one in 1/8", and the rear 1/4" (firewall) on each side, you will still have plenty of room to adjust some additional camber and toe. Without requiring several (and I mean several) shims.

the extra shims on the back of the arm is because alignment guys are adding caster to the car .....if you pull the back of the arm inboard, that swings the ball joint backwards and in turn tilts the spindle rearward therefore adding caster, the original Guldstrand template moved the arm downward for camber gain and back for caster gain and tilted it less for a better control of the anti-dive under braking...with stock arms and the guldstrand you can get just barely over 4.0 degrees of caster, way better than the roughly 2.0 degrees you get stock.......remember there is NO FREE LUNCH, by adding caster the wheel and tire combo moves backwards in the wheel well and closer to or even hitting the fender depending on tire width, rims and offsets

[68Formula]

the extra shims on the back of the arm is because alignment guys are adding caster to the car .....if you pull the back of the arm inboard, that swings the ball joint backwards and in turn tilts the spindle rearward therefore adding caster, the original Guldstrand template moved the arm downward for camber gain and back for caster gain and tilted it less for a better control of the anti-dive under braking...with stock arms and the guldstrand you can get just barely over 4.0 degrees of caster, way better than the roughly 2.0 degrees you get stock.......remember there is NO FREE LUNCH, by adding caster the wheel and tire combo moves backwards in the wheel well and closer to or even hitting the fender depending on tire width, rims and offsets

Thanks. Was wondering why all the shims in the back. That means I can use the other inserts in my DSE arms to add caster, and take out a bunch of those shims.

[David Pozzi]

A lot depends on who's arms you use and how much positive caster and negative camber you want to set. Global West seems to have pretty equal shims front and rear at 5 deg positive, 1 deg neg camber. Only 1/4" of shims front and rear on a friends car. Another issue is, - Positive camber and negative caster increase at lower ride heights due to the angle of the upper A arm holes front and rear, the upper ball joint travels rearward in dive.

[nokones]

Wouldn't it be easier just buy some SPC Adjustable Control Arms? With the SPCs you can dial all the camber and caster you desire? I bought my SPCs from Guldstrand many years ago.

[Rod]

Wouldn't it be easier just buy some SPC Adjustable Control Arms? With the SPCs you can dial all the camber and caster you desire? I bought my SPCs from Guldstrand many years ago.

yes and no.....the guldstrand mounts the arm in a different location,changing the pivot point.....Under cornering conditions, the original factory '67-'69 Camaro/Firebird and '68-'74 Nova and were designed with no "camber gain" into its suspension geometry...repeat "NO" camber gain you can add static camber and that helps, but there is no dynamic(moving) camber gain in the suspension design so you must change the pivot location to improve the geometry, the only other way to do this is with a tall ball joint(often not tall enough) or a tall spindle(may require a larger dia. rim than stock) not a big deal with modern PT wheels.......Using the Guldstrand (for First Generation Camaros and Firebirds) will let you lower the upper control arm pivot points by .75 inch. This raises the front suspension roll center from below ground level, to a point well above the road(better handling). This will reduce the angle of the lower control arms and make them more parallel to the ground, giving you a more favorable camber curve. The new holes will also move the top of the spindle rearward .25 inch from stock. This will create more positive caster, which will make the steering feel more "snappy.

[David Pozzi]

Wouldn't it be easier just buy some SPC Adjustable Control Arms? With the SPCs you can dial all the camber and caster you desire? I bought my SPCs from Guldstrand many years ago.

SPC's have more adjustment range for sure. The downside is no stop for suspension droop. The shock will become the droop limiter, but that's not uncommon. There are several threaded connections that could come loose or break. Not likely, but something that is different from the "regular" tubular A arms. The pivot bushings look smaller than the tubular A arms. I've heard of one breakage, but it was due to the pivot mounts being installed upside down.

Ride Tech and Detroit Speed are moving the lower ball joint forward and the Upper ball joint rearward, which helps keep the spindle centered in the wheelwell. Some others may be doing the same. At 5 deg caster I don't think the wheel is moving rearward much but maybe .5". The trouble is, large tires on a Camaro usually hit the rear splash panel, so it often needs some bumping back.