Getting a FC Station Sedan to handle

[Glenn 'Stinky' Stankevicius]

Can a Station Sedan be made to handle well with the leaf spring rear or should I be looking at other options?
I am thinking of spirited drives in the hills, hill-climbs, maybe track days.

[Errol62]

I used to punt my EK sedan up and down the old mt barker road every day for a couple of years when I lived at Bridgewater, throwing her into corners like the devils elbow with confidence. Rear springs reset 1" lower, front 2" lowered stock HR springs (reduce uncompressed length by 60mm from memory). 185 and 215 radials on 6 & 7x13s, heavy duty gas shocks, 25mm custom front sway bar and battery in the boot. I had the camber dialled up pretty well to even up the wear on the front rubber. Battery in the boot makes a significant difference together with radials and lowering. For my van I'm planning the same setup with the addition of a rear bar from a UC Torana.
One of the main influences on handling and performance is weight and weight distribution so considering them carefully when modifying will give the best result.
Cheers
Clay


Sent from my iPad using Tapatalk

[ardiesse]

Glenn,

If you're running an HR front suspension, there's a trick you can do to improve the car's handling: lower the mounting points for the upper control arm shafts by an inch.  It's not quite as easy as drilling four new 1/2" holes in the crossmember - there's quite some work to do on the crossmember towers with angle grinder, welder and drill though.

The effect is to raise the roll centre of the front suspension, which reduces understeer.  Equivalently, what this mod does is make the camber go negative when the front suspension goes into bump, which largely offsets body-roll-induced positive camber on the outside front wheel.

I did this mod to an HD I had.  The handling improved, and I got an extra 10000 miles out of my front tyres.

While I'm thinking of rear suspensions, you'll find the car handles better if you reverse the rear spring shackles, so that the rear eye of the rear spring is below, not above, the spring hanger on the body.  Now, you'd obviously need to get the rear springs reset lower, and maybe even get custom main leaves made up that are an inch or two longer to minimize the risk of the rear shackles inverting.

This change lowers the roll centre of the rear suspension.  Think of it this way - the rear spring transmits a proportion of the cornering force to the body through the rear spring shackle to the hanger on the body.  When the back of the rear spring sits below the hanger, the cornering force is effectively applied to the body lower than would be the case when the back of the rear spring sits above the rear spring hanger.

The car's roll axis is on a front-to-rear line joining the roll centres of the front and rear suspensions.  When the roll axis slopes down toward the front of the car, this is bad.  Chronic understeer is the result.  We've all seen photos of early Holdens heeled over hard on the outside front wheel, with the inside rear wheel nearly off the ground.  Example: any picture of the 1965 Bathurst race with an HD Holden cornering.

Generally, an early Holden's front roll centre is maybe an inch or two below the road surface, while its rear roll centre is maybe an inch below the rear axle's centreline, so about ten inches above the road surface.  Any change you can make to raise the front suspension's roll centre and lower the rear suspension's roll centre will be beneficial.

Here endeth Suspension Design 101.

Rob (and thanks for the Antique Gold photos)

[59wagon]

Hi Rob, great write up, thanks. With this mod, I can see what's required on the tower inboard side to allow the upper control arm shaft to be lowered, but I'm wondering if the outboard side needs attention as well.  It looks like there's a chance that the upper control arm "bump stop" rubber may hit the reinforcing plate on the tower when the upper control arm drops whilst driving. Is this an issue? If so, how would you mod this to correct it.
Cheers, John

Glenn,

If you're running an HR front suspension, there's a trick you can do to improve the car's handling: lower the mounting points for the upper control arm shafts by an inch.  It's not quite as easy as drilling four new 1/2" holes in the crossmember - there's quite some work to do on the crossmember towers with angle grinder, welder and drill though.

[hsv-001]

If you go heavy duty shocks on the rear then reinforce the upper mounting points or you will tear the shocks out .

[mcl1959]

Glenn, this is a good mod. I did it a couple of times at Hoppers Stoppers when I was there. The easiest thing to do with the top bump stop is to replace it with an FB EK one which is more of a tapered shape (I think it's FB EK anyway. Purchased them at R/S) this can then be easily trimmed down a bit to provide more clearance.

Ken

[ardiesse]

John,

You wrote -

". . . I can see what's required on the tower inboard side to allow the upper control arm shaft to be lowered, but I'm wondering if the outboard side needs attention as well.  It looks like there's a chance that the upper control arm "bump stop" rubber may hit the reinforcing plate on the tower when the upper control arm drops whilst driving. Is this an issue? If so, how would you mod this to correct it."

Unless I misunderstand you, hit the reinforcing plate on the tower of an HR front suspension is what the rebound stop is designed to do.  When you lower the upper control arm mounting points in an HR front suspension, the rebound stop rubber still contacts the reinforcing plate on the tower, but just in a slightly different place than before.  You should also be aware that you lose maybe half an inch of total suspension travel when you lower the upper control arm mounting points; but the loss is all at the extreme of rebound.  In short - I figured that I wouldn't be doing any Dukes of Hazzard -type driving, and I could live with the slightly lessened suspension travel.  I had no problems.  It's worth pointing out that the HR rebound stop rubber is very short, shorter than the HR bump stop rubber, and much shorter than an FB-EH rebound stop rubber.

If you are thinking of lowering the top control arm mounting points on an HR front suspension, let me know, and I'll send you a long and gruesome pm detailing all the work you need to do.

Rob

[59wagon]

If you are thinking of lowering the top control arm mounting points on an HR front suspension, let me know, and I'll send you a long and gruesome pm detailing all the work you need to do.

Rob
[/quote]
Thanks Rob, I'd appreciate the long and gruesome message if it's not too much trouble. It sound's like a positive thing to do.
Cheers, John

[59wagon]

Glenn, this is a good mod. I did it a couple of times at Hoppers Stoppers when I was there. The easiest thing to do with the top bump stop is to replace it with an FB EK one which is more of a tapered shape (I think it's FB EK anyway. Purchased them at R/S) this can then be easily trimmed down a bit to provide more clearance.

Ken

Thanks,  Ken. I think I'll give it a crack.
Cheers, John