G-body rear link angles?

[ScotI]

Years ago I never really was concerned about the angles of the rear arms but now I'm wondering if there's more in the combo w/some adjustments.



My car currently has trimmed stock rear coils, KYB's, & an aftermarket sway bar (Suspension Techniques). It's lowered for stance/looks & I want to make it functional as well.

Should the upper links be level @ ride height? Should the lowers?
Is there an ideal combination for a street/'touring' type G-body?
Does anyone have any good links on setting up G-bodys to handle (w/o building a 'race' car)?

[Randy67]

I would get hold of Marcus at www.scandc.com. He has done alot with G-bodies and could help you out alot.

[Norm Peterson]

One thing you don't want is lowers that run downhill from the axle to the chassis (side view). That condition works against both traction and handling. Plan on level to slightly uphill instead.

Side view inclination of the uppers mostly affects the anti-squat (read: launch traction). While the effects on rear roll center height and the rear suspension's roll steer from more steeply inclining the uppers are relatively smaller, they are such that you trade off rollsteer (getting more of something that too much of is entirely possible) to get more anti-squat. A classic dragstrip vs corner-carving situation in which it helps to identify where in the spectrum between those extremes you want to end up (50% - 65% A/S and 3% - 4% vehicle roll understeer sounds like it might suit your intentions).

Norm

[ScotI]

Thanks for the quick responses. My big issue is I like the car low but never really worried about how much it affected the total performance of the package.

I'm going to be 100% honest & say my car will prob never see a track. That being said, I still want it to handle better than a stock G-body did back in 79.

When I took a quick look under the car last night after we approximated the rear ride height, the lower links were level to a very slight incline towards the frame. The upper links were definitely sloped from the rear housing to the frame mounts. If this isn't good, how can I remedy the situation & still maintain my lowered stance? Can I lower the attachment point of the lower-links @ the rear end or would that open another can of worms?

Currently the front of the car has 2" dropped spindles, 600# Suspension Tecniques front springs, 1 3/8 ST front bar, poly bushings, & KYB's (= 3~4" drop). I would like to get SC&C's front G5 set-up to get the better geometry while still lowering the car & the benefit of the larger disc set-up but it's not in the budget right now.

Maybe I need to start a 'street touring' movement .

[Norm Peterson]

If the lowers are angled up toward the frame, that's in the right direction.

If not, lowering the axle-end pivots of the LCAs is a fairly common mod for the Fox/SN95 Mustang chassis (generally referred to by that crowd as anti-squat brackets) and 3rd/4th gen F-bodies (aka "relocating" or more simply "relo" brackets). It's a sufficiently common mod that there are commercially available kits at least for those cars. Be forewarned that many such kits are a bit more dragstrip oriented and drop the axle side pivot too far (to achieve more A/S at the expense of what most here would consider an excessive amount of roll understeer). But if you're careful (and do a bit of research) you can redrill the brackets for holes at heights more suited to a PT machine (defined here as anything with more serious cornering intentions than it has with its OE specs).

As regards a "street touring" vs a more hardcore "race" setup, geometry and springs/bars/shocks are separate parts of the equation. I'd rather get the geometry straightened out and compromise on things like spring rate to suit a less than all-out competition effort than put up with a ride that's stiff simply to keep bad geometry from letting/making the wheels point off in stray directions not necessarily of my choosing. And I'm pretty tolerant of a firm ride.

That said, your front spec's aren't bad, if somewhat soft for auto-x or serious track lapping (that's my reference point, not a reflection on yours). The only real question is how well the KYB's will stand up to the combination of 600 lb/in springs and a 1.375" sta-bar.

The rear roll stiffness is the big question mark at this point, but with that much stiffness up front I'd be looking (gut feeling with no specific numbers run yet) at 140 lb/in or stiffer rear springs and a 1" rear sta-bar to take some of the cornering work off the fronts - unless you have a stout motor and like to steer with your right foot, anyway..

Norm

[ScotI]

If the lowers are angled up toward the frame, that's in the right direction.

Actually.... I'm backwards so I'll need to relocate the rear end mounting points a little lower.

The only real question is how well the KYB's will stand up to the combination of 600 lb/in springs and a 1.375" sta-bar.

When this set-up was in my elcamino, I actually had Monroe Formula GP's & the ride was equal to a Fox body Ford or GM F-body. The car/truck handled pretty decent (subjective) so it was a big improvement over stock GM. Since then, the camino was totaled & my buddy snagged all the front end stuff for his malibu but already had KYB's.

These days, that Malibu belongs to me. I would prefer to lose the dropped spindles & get some new 'improved' rear arms but figure it's better to sort through what I already have & get the geometry dialed-in before spending cash on more stuff.

[Marcus SC&C]

Scot,I think you`re absolutely right about dialing in the geometry first and going from there. That`s how we like to do it too. You can relocate the lower arms downward on the axle end with a bracket kit made to do just that. It`ll also relocate the instant center and improve your traction. Generally these cars loose traction when you lower them (unless you repair the geometry again). The brackets bolt in place to locate them,then they have to be welded in place. Pretty easy install. We have the kits,with hardware for $65.
FWIW I think you could use some more rear spring rate too. If you`re doing the low buck thing try Moog 5413. They give a slight drop from stock and are 167lbs/in vs. 125lbs/in for stock Malibu springs so you`ll still gain rate even over your trimmed rears.
Keep in mind that the factory geometry on these cars (and a lot of others) is pretty poor so you can get very impressive results with geometry and alignment mods less radical than G-5. It`s really more of a no holds barred package for a very few people who`re going *all out*. For now a set of Bilstein shocks would be a step in the right direction (they`d go really well with a Stage 2 package BTW ;) ). Mark SC&C

[ScotI]

'Norm' & 'Mark', I have read your posts on related subjects & value your opinions & suggestions greatly. Mark, I like the idea behind the SC&C G5 kits. Correcting the camber curve, adding height to the spindle, & shedding some weight; all while lowering the car a similar amount to dropped spindles + springs suits me well. The C5 brakes are the icing . . .... you're not having a 'barely used' sale anytime soon are ya? (lol).

I figured I could adjust the lower rears to be level w/relative ease.... it was the uppers that were more of a concern because they have a pretty drastic angle. At first I thought I would switch to some of the adjustable 'mono-ball' style uppers to help & that's when I asked the question: "What angle is optimum for a pro-touring style car?".

I'll look into the rear relocation bracketry (I looked on the SC&C site before but didn't see anything). My buddy is 100% correct in pushing me to get the car sorted & going 'as is' so this build-up doesn't drag on for years; & then refine as needed later.

[Dust87ss]

For now a set of Bilstein shocks would be a step in the right direction (they`d go really well with a Stage 2 package BTW ;) ). Mark SC&C

I would say they go really really well with a Stage 2 package. My spring rate is also similar to Scot's.