Increase positive castor

[40cpe]

I'm starting another thread so as not to butt in on the already active thread about steering issues. I have radial tires and integral power steering on my '55. The car has been checked at an alignment shop and has stock specifications now. The steering feels too "light" at road speeds and doesn't want to track straight ahead. Ball joints, tie-rod and ends are new, idler arm is new. Wheel bearing play has been checked. I've reduced the pump pressure all I can. I want to add some positive caster to see if it helps. Without going to an alignment shop at every trial setting, can I remove some alignment shims from the rear of the "a" arm and accomplish more caster? If so, about how much thickness would accomplish the desired 4 degree increase? If that helps I don't mind springing for another alignment to get things squared away.

[Ole Don]

Go for it, but check toe after. Up to a point, more is better.

[KULTULZ]

Originally Posted by 40cpe

I'm starting another thread so as not to butt in on the already active thread about steering issues.

I have radial tires and integral power steering on my '55. The car has been checked at an alignment shop and has stock specifications now.

The steering feels too "light" at road speeds and doesn't want to track straight ahead. Ball joints, tie-rod and ends are new, idler arm is new. Wheel bearing play has been checked. I've reduced the pump pressure all I can. I want to add some positive caster to see if it helps. Without going to an alignment shop at every trial setting, can I remove some alignment shims from the rear of the "a" arm and accomplish more caster? If so, about how much thickness would accomplish the desired 4 degree increase? If that helps I don't mind springing for another alignment to get things squared away.

Most Factory Settings
(bias ply tires)
0.5 Negative Camber
0.5 To 1.0 Positive Caster
0.24 Toe-In

Good Street Performance Settings
(radial tires)
0.5 Negative Camber
3.5 TO 4.5 Positive Caster
0.10 Toe-In

SOURCE- http://www.superchevy.com/how-to/cha...gnment-basics/

If you can manipulate the shim packs and come out without a way to read the final settings, you are a better man than I am...

You need to find a reputable spring shop or HI-PO shop IMO.

[miker98038]

I know the pass car and the bird use the same A arms, I’m not sure how the mounting and adjustments work out. But my 55 bird wouldn’t get to much past 2 degrees on the caster until I modified the upper ball joint mount. That was a major deal. But there’s a huge difference in how it tracks at 3.5 degrees after the mods.

I read in a post somewhere that a guy had shifted the washers on the lower arm, pushing it a bit forward and got better numbers. Unfortunately, I can’t remember where or any more details.

[deucemac]

Changing caster only can be tricky. You can't just remove a shim tom the rear or add a shim in the front. Doing so will change both camber and caster. If say you remove a 1/8th shim from the rear then a 1/8th shim must be added to the front. That will cause caster to increase and the camber to remain the same. Having done brake and front end for an eternity plus teaching it for 15 years, I have found that you will most likely be happy with no more than 3 degrees of positive caster on an independent suspension. Also remember that camber and caster are not the same from side to side. A 1/2 degree split is necessary on camber and caster. A 1/2 degree heavy camber on the drivers side will compensate for driver's weight and will even out with the driver in place. A 1/2 degree extra caster is adjusted into the passenger side to combat road crown for drainage. All roads have it to some degree and by increasing the right side caster you will track straight. Setting it even on both sides will cause the car to follow the crown and drift to the right. Make sure that the alignment is set to the heavy camber left and heavy caster right BEFORE swapping shims. Done right you can improve handling. Done wrong you may end up with a car that handles like a safe in a wheelbarrow.

[KULTULZ]

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..damn...

What he said ...

[40cpe]

deucemac, Thanks for the information. I'll take it to a front end shop with your recommendations.

[bobss396]

I don't know if more positive caster is going to help the situation. On cars with symmetrical a-arms, you can more shims back and forth equally and have little impact on the camber.

Deucemac has a lot of good information in his post.

Try to find an old alignment shop and talk to those guys, possibly a truck shop. I borrowed an alignment rack when I needed to align my Ford after all the front end work.

[miker98038]

I think deucemac said it as well as it could be said without taking his class.