Frame / Springs: Leaf Spring forward pivot position

[skycar]

Hi to all here,
I have just completed the difficult task of changing all the leaf spring/shackle bushings (6). They were well overdue for retirement and I think I am too, after that.
They must have been the originals, on my newly acquired 62 GT.

My question is ..... the forward bush mounting position, (the inch and a half diameter bushing) has the bolt located in the lower hole of the fitting. There is another hole approximately 3/4" above this one.
Can I use that hole instead and how will it affect the steering of my non power assisted Hawk?
I was thinking it would marginally lower the back of the car, subsequently slightly raising the front and therefor steering the beast a smichin easier at lower speeds?
Any thoughts or feedback is greatly appreciated, as always.
Regards Roger
Brisbane Australia

[PackardV8]

The likely result would be so slight as to be nil. Lowering the back increases the caster which increases steering effort.

jack vines

[Alan]

Stude built them that way so the car would sit level with a 200 pounder at the wheel.

[wittsend]

Changing the front spring location will alter the pinion angle. This alters a preset relationship between the angle of the driveshaft as it exits the transmission and as it connects to the rearend pinion gear. Vibration is a possible consequence. If you have a two piece driveshaft the problem would seemingly become greater.

Also, many cars have roll steer built into them. With a leaf spring car this is the relationship of the front to rear mounting locations. At times decreasing roll steer is desirable, but you need to know the effects and consequences. And, if roll steer adjustment is the primary goal the pinion angle alteration also should be corrected.

Lastly, as noted you will increase caster on the front wheels. While the 3/4" adjustment might not create any negative effects you need to be aware that any and all are possible.

Tom

[bosshoss61]

I agree with all three posts.............

[skycar]

Thanks to all for the informative input here, sounds like its best to not reinvent the wheel and leave it as it was designed.
I hadn't considered the pinion angle change and possible vibration affects etc and I love the 100 pounder comment.
regards Roger

[StudeRich]

I think the important issue with the Rear Leaf Spring FRONT mounting has not been addressed here, we are NOT talking about moving the location of the Front springs!

The ORIGINAL forward, rear spring mounting was in the upper hole on one side and in the lower hole on the other side to balance the Car.

It sounds like the OP is saying he put them level and wondered if he should raise them both to lower the car.
One of us is misunderstanding this, is it me or the others?

I don't see this 1/2 inch adjustment affecting the front end in any way, certainly not anything like those who cut a Coil or two out of their Front Springs and screw up the ride height, Alignment and balance by 2 to 4 INCHES!

[skycar]

Hi StudeRich,
thanks for your response here. So are you saying to set the car up the way it is meant to be, I should do as you mention in your post?
And as I am in Australia with a Right Hand Drive car, which mount position is correct, "To balance the car"?

The right one in the lower or upper hole, and vice versa for the left side?

Is this to cater for a driver only, "the balance"? Or is one side of the car heavier than the other?

Regards Roger

[Alan]

The left one in the upper hole and the right one in the lower hole for RHC cars. Though they could be in any position and not make much difference. If you weigh 140 lbs. It might be a little high. But you would have to have someone drive behind you and see if the car looks funny. If you weigh 250 or more you will be taxing the springs.

[Mike Van Veghten]

The pinion angle.............!?

No harm in either hole..

1. I doubt Stude engineers would have put it (the extra hole)there as an adjustment point if they were concerned about the pinion angle.
2. It won't alter the pinion angle enough to do harm...it's a big triangle, do the math, the included angle gets less and less as it gets close to the axle. Is the new angle there...yes, enough to hurt anything...I'd bet not.
3. In a leaf sprung car, the axle moves all over the place compared to a solid bar (3 bar, 4 bar, four link, etc., etc.) type attachment point. This also makes the pinion continuously change it's angle more thAn the 3/4" different spring mounting point ever would.

Plus......Alans comment about the driver weight...something to think about..

Mike

[stude dude]

The left one in the upper hole and the right one in the lower hole for RHC cars. Though they could be in any position and not make much difference. If you weigh 140 lbs. It might be a little high. But you would have to have someone drive behind you and see if the car looks funny. If you weigh 250 or more you will be taxing the springs.

Exactly! Roger do you have a shop manual?

Chris.

[skycar]

I do have a manual and didn't think to look there for that type of info. I put the bolts back the way I found them, both in the lower hole positions.
Therefor it now seems that I need to make a correction.
The state of the bushes was worthy of photo's and I assumed they had probably never been changed in 50. The chassis ones were sooo difficult to get out.
Thanks again to all for the knowledge shared here,
Roger

[StudeRich]

Roger, on a LHD Car the Battery, Steering Gear and Driver are always on the Left side no matter what, passengers or not, so the adjustment was with that in mind. The only other balance was that the complete power train is just a little to the right of center and helps only slightly.

So when you go to RHD I guess the Battery is still on the Left, but of course the Steering Gear and the Driver are not, but the power train is shifted slightly to the Left of center and the rear springs setup opposite to LHD as far as I know, remembering that I did not write the book on this.

[skycar]

Thanks StudeRich and to all the others here..... the worldly knowledge shared here, is priceless and much appreciated. The beers are on me when you cross the big pond and visit these distant shores.
Regards Roger

[bosshoss61]

POST # 3----where in the world did you come up with that? That would mean driver shackles or front springs would de different from left side to right. My old lady will have to gain some weight to balance the car out................