With all stock front end parts +1º caster is about all you can hope for, and some cars don't have that much adjustment.

With power steering, do the same with a stock front end. You can get 3-5º more caster with aftermarket tubular upper control arms. It's a good mod.

I'm still confused, but that's pretty common.
With tubular uppers and a 500 power steering box, how much caster is recommended? I think 6 degrees would be way too much, with wider than stock tires (225-55-16).

 

Don, most of the recommendations are for 3-5º of positive caster with power steering. I don't recall ever seeing aftermarket control arms with more than 5º extra, though I'm sure it's possible they are out there. So you'd have to go to some extra trouble to get more than 5º with a modified stock front end.

Not real sure, I think that a C4 Corvette front end may have somewhere around 6º caster.

I think there's probably enough assist from power steering to handle that, I don't think that's a problem.

At some point you get instability when backing up when you get too much positive caster (positive caster is actually negative caster when backing up). Occasionally you see this on a dragster or funny car, but those cars might have 20º of positive caster, and the instability only shows up when they back up at high speed.

The other half of aftermarket control arms with 5º extra is that for the same reasons you can only adjust the stock front end so far, you can only reduce the positive caster from an aftermarket control arm so far.

 

Wheel Alignment 101

See link: http://www.familycar.com/Alignment.htm

 

Pops asked me to comment on using split camber or caster settings to deal with the crown in the road. If everything is set equal on both sides, your car is going to tend to run (downhill) toward the shoulder.

His link mentioned using split camber to get the car to track straight on a crowned road, and I think the CCI recommendation is for a split camber setting.

I've never tired to use this. I think there might be some variation in the results based on what tires are on your car and how wide they are.

What I've done successfully is to split the caster settings. If you put about 1/4º more positive caster on the passenger side, this should take care of the crown in the road.

You UK and Aussie guys would have to do the opposite.

 

Steering axis inclination.

Sometime the "steering axis inclination" is included in alignment specs or discussions.

This is the angle through the lower and upper ball joints when viewed from the front of the car. It is NOT adjustable, and is machined into the spindle.

The main thing that the steerign axis inclination afftects is the scrub radius. The distance between the spot where the steering axis inclination line meets the ground from the center of the tire is the scrub radius. Positive scrub radius is where the tire centerline is outboard of the axis.

A complete discussion of scrub radius is pretty lengthy. In general you want a positive scrub radius and you want it small. Wide wheels and negative offset wheels make the scrub radius bigger. Cars designed for wide wheels will have a higher steering inclination angle (think Corvette).

Toe out on corners

In general, you'd like for the inside tire in a turn to turn a little more than the outside one. That way they won't fight each other when you're turning.

This is controlled by what's called "Ackerman". The angle of the steering arm is what controls it. "100% Ackermen" is where a line from the lower ball joint through the tie rod pivot on the steering arm intersects with the center of the car at the rear axle, when viewed from above.

55-57s have pretty close to 100% Ackerman.

If you wanted to use the stock steering arms with a front steer rack, you'll screw up the Ackerman in a big way. Front steer cars have the steering arms angled outward at the tie rod instead of inward.

 

What does "split" caster settings mean exactly? Is it different than just increasing or decreasing on one side? By the way, Thank you Rick for your many posts and research in this area!

 

Yes it's just what you said. You use a different settting on each side.

 

This comes up so frequently, decided to make it a sticky:

Stock specs
Camber Degrees......0º to +1º
Caster Degrees........0º +/- 1/2º
Toe In....................1/16" to 3/8"

The biggest deal here is the caster. Positive caster is what makes your car track straight down the road and makes the steering wheel return to center when exiting a turn. It also makes the steering effort harder.

With all stock front end parts +1º caster is about all you can hope for, and some cars don't have that much adjustment.

With manual steering, as much postive caster as you can adjust for is about all you should do, as more will make the steering too hard.

With power steering, do the same with a stock front end. You can get 3-5º more caster with aftermarket tubular upper control arms. It's a good mod.

Another way to get more caster (or camber if you can't remove any more shims) is to use offset upper control arm shafts. They'll usually get you an extra 1º - 1-1/2º

On the camber, zero or even slightly negative is a small plus for cornering.

On the toe in, the shop manual says 1/8" -3/16", but that was superseded by a factory bulletin in the mid 50s. Radial tires will definitely not want much toe in.

The above deviations from the stock specs are my opinion. I think most agree with the general nature of them, but some may have their own ideas on the details.

Rick,
great information, but can you do anything but take the car to an alignment shop with all their computers and technology? This can't be done in a garage of the restorer, can it? thanks for the enlightenment,
Mike

 

hpnelson, I know you asked this over a year ago, but since this is a sticky thread and links get posted to it periodically, I thought I'd answer.

There are several ways to do alignment or parts of the alignment job in a home shop. The results will be as good as the tools you build or use and the care and thought that you can or are able to put into the job.

First of all you need to do your home alignment on a level surface, both side to side and front to back.

You can set camber with a level or digital protractor by measuring it on the wheel at its maximum diameter. Because of the way wheels and tires are shaped, you'll need to build something that sits on the wheel without touching the rest of it; it also needs a surface for the level or protractor.

You can set toe-in with a tape measure. You just measure across the widest part of the tire at spindle height in front of the spindles, and behind them. Building a tool that is essentially a giant caliper can help with that, or you can use a pair of carpenter's squares.

You can measure caster by turning the wheels 20º to the right and measuring camber, then do it again, turning the wheels 20º to the left. After that you go through some math. Kind of a long winded procedure to get a number. But pretty easy to see whether it's the same on both sides. The measurement gets more accurate if you have the front tires on turntables. A couple of pieces of sheet metal or even cardboard can be a poor man's turntable.

Or you can use a camber/caster gauge that clamps on the front hub. 50 years ago a lot of shops used that kind of tool. And through the years a lot hobby cars and race cars were done with one. That gauge won't fit with many of the custom wheels though.

 

As info- Heidt's has A arms with 6 degrees positive caster.

 

alignment of my 55

wow thanks for all the info As usual you seem to nail it on the head.
Now if I could ask you a couplew more questions as my 55 has been done for a couple of months but was simply to scary to drive as I have too much money in it to take a chance. There is always tomorrow

Who's after market cross shafts do you recommend? My weak area on these cars is the front end. Is there a way to remove the top control arms without compressing the coil springs. A fellow told me that it was possible but I do not know if he was telling me a story.

I would love to get this fixed then I can work on my vintage air problem. The fan wants to run when iut is turned to the off postion. I think its a ground problem

But I need to key in on the cross shafts and the R&R of the control arms

Thanks Gary

 

Gary....

1) Who's after market cross shafts do you recommend? I get my offset upper control arm shafts from CPP:http://www.classicperform.com/Store/1955_1970_Fullsize_Cars/TG119O.htm and replace the bushings with ones from Moog....(Much better rubber)

2) Is there a way to remove the top control arms without compressing the coil springs? Yes...

You have to jack/support the car by the lower control arm. Do NOT allow the front wheels to hang. See "Upper Control Arm Spherical Joint". It may be easier to take the ball joint off the upper control arm rather than take it off the spindle ( steering knuckle), unless it is still riveted on. If it's still riveted, it probably needs replacing, since that's an original ball joint. ..... http://chevy.oldcarmanualproject.com/shop/1955/55csm0310.html ....

 

caster/camber settings

Rick, Hi, I'm new to these forums. Could you suggest caster camber settings for a 57 Bel Air with 2" front drop and CPP 500 power steering. I used stock settings and stock A-arm shaft and I am getting balding wear on inside edges. Tells me at least the camber is wrong. I am getting a set of offset shafts from Danchuk through their Christmas sale. All help is greatly appreciated.
Thanks,
LB

 

As you said, the wear on the inside of the tires indicates you have too much negative camber (top of tire is further inboard than the bottom). Which means you need to remove shims or go to offset upper control arm shafts.

As far as caster, with a CPP500 box you can handle a lot of caster. If you don't have tubular upper arms, you are stuck with whatever you can get using the stock shims and/or offset shafts.

Remember this part. You set the camber first by adding or subtracting shims on both bolts. Then you add positive caster by subtracting shims from the front and adding it to the back. Once you've run out of shims on the front you're done, you can't adjust caster any more without affecting camber. When you go to offset shafts, you'll need to add more shims on both bolts to get the camber right. This means you have more shims to remove for setting caster.

 

Great information. Maybe I can add a few details.

:To get a caster reading with an angle gauge. Turn tire 20 degrees in at the front and measure the angle, then turn it past straight ahead to 20 degrees out and measure again. Multiply the overall change by 1.5 and you will have a caster angle. If when turning the wheel in at the front the angle goes more negative than the static camber reading then you will be reading positive caster. If it goes more positive then you will be reading a negative caster angle.

Example: Static camber= 0. Turn tire in at the front 20 degrees and remeasure camber. Say it then reads -1/2. Then turn the front of the tire outboard past the straight ahead point to 20 degrees out and remeasure the camber. For the example say it now reads +1/2. The difference is 1 degree overall. Multiply 1 x 1.5 and the caster angle is positive 1.5.

:The comment about tire wear on the inside edge can be from camber, but it can also be from excessive toe-out.

:The most common method to compensate for road crown is the 1/4 - 1/4 method. Add 1/4 degree more positive caster on the right, and 1/4 degree more positive camber on the left. Typically though I just add the caster on the right and set the camber the same on both sides. You get more consistent cornering that way. If it still has a tendency to pull to the right, add a bit more positive caster on the right.

Andy

 

I'm trying to set up my 55 front end after complete rebuild. Please help me understand caster. After you have the camber set. You then check caster as described above. Say you do the math and you determine you need more positive caster. This is were its fuzzy. When you remove the shim from the front bolt and install it on the rear bolt that will increase positive caster. But what does that do to your camber setting? Am I missing something or is the camber setting just a starting point to get the caster? Thanks Ron

 

.......When you remove the shim from the front bolt and install it on the rear bolt that will increase positive caster. But what does that do to your camber setting? Am I missing something or is the camber setting just a starting point to get the caster? Thanks Ron

When you move a shim from front to back, it will move the upper ball joint back, but it won't move it in or out very much. Think of the upper control arm as a triangle that you move 2 corners, one in and the other out, the same amount, the third corner swings in a arc between the others.

 

Thanks Don that helps me a wrap my head around the logic on this set up. Been working on these cars for years. I have rebuilt lots of front ends. But always took my cars to a good front end shop for alignment. But these days it's getting to the point you can't find a shop that you can trust leaving your car with for repairs. And most mechanics are not trained on these old cars. I guess those days are fading away fast. Ron

 

I'm still fine tuning the front end of my 55. Stock A-arms and spindles bias tires.
The stock spindles have four flat spots near the ball joint mounts two on the front top and bottom and two on the rear top and bottom. I've done some measurement and the flats seem to be the same distance from the center of the BJ to the flat spot top and bottom.
My question is with a special jig to set on the flat spots top and bottom of the spindle tires in the straight forward position. Can you measure caster with degreed angle gage.
Just trying to eliminate turning wheels 20 degrees in each direction an multiply by 1.5
So if I measure off the spindle and get 4 degree positive is that 4 degree positive caster. Thanks for the help. Ron

 

If you can access it to make a measurement that will work.

How are you going to access that for a measurement with the wheel and tire in place and on the ground? You have to make this check at ride height.

Positive caster is when the upper ball joint is to the rear of the car compared to the lower ball joint.

 

Thanks Rick that's what I was thinking but wasn't sure.
Yes I'm making all measurement on level floor with car sitting on the tires.
My jig is rather crude but it stays true. The Allen bolts I use on spindles, caster and the beem clamps I use on the outer wheel lip, camber.

It's not to bad to get to the front of the spindles while laying on the floor in front of the car. Ive double checked my reading after several short test drives and keep getting the same numbers. 5 degrees positive caster L R 1/2 positive camber LR 3/8 toe. Ron

 

This comes up so frequently, decided to make it a sticky:

Stock specs
Camber Degrees......0º to +1º
Caster Degrees........0º +/- 1/2º
Toe In....................1/16" to 3/8"

The biggest deal here is the caster. Positive caster is what makes your car track straight down the road and makes the steering wheel return to center when exiting a turn. It also makes the steering effort harder.

With all stock front end parts +1º caster is about all you can hope for, and some cars don't have that much adjustment.

With manual steering, as much postive caster as you can adjust for is about all you should do, as more will make the steering too hard.

With power steering, do the same with a stock front end. You can get 3-5º more caster with aftermarket tubular upper control arms. It's a good mod.

Another way to get more caster (or camber if you can't remove any more shims) is to use offset upper control arm shafts. They'll usually get you an extra 1º - 1-1/2º

On the camber, zero or even slightly negative is a small plus for cornering.

On the toe in, the shop manual says 1/8" -3/16", but that was superseded by a factory bulletin in the mid 50s. Radial tires will definitely not want much toe in.

The above deviations from the stock specs are my opinion. I think most agree with the general nature of them, but some may have their own ideas on the details.

So I'm almost ready to get alignment done. I'm going to let a shop do it, but I want to make sure I give them the proper numbers. I've got CPP tubular upper arms, stock lower arms with a CPP500 box. So, based on what I've read my numbers should be:

Camber 0 degrees

Caster +5 degrees

Toe in 1/16" to 3/8"

Is this correct?

 

How big a job is it to replace the cross shafts?......what's all involved?

 

If your replacing them to gain caster it might not be a bad idea to install the new A-arm with + 5 built in.
You can get with rubber or poly bushing. Love your car! Hope to see you next august at the Tri-five Nationals.

 

Nice..........thanks

 

This comes up so frequently, decided to make it a sticky:

Stock specs
Camber Degrees......0º to +1º
Caster Degrees........0º +/- 1/2º
Toe In....................1/16" to 3/8"

The biggest deal here is the caster. Positive caster is what makes your car track straight down the road and makes the steering wheel return to center when exiting a turn. It also makes the steering effort harder.

With all stock front end parts +1º caster is about all you can hope for, and some cars don't have that much adjustment.

With manual steering, as much postive caster as you can adjust for is about all you should do, as more will make the steering too hard.

With power steering, do the same with a stock front end. You can get 3-5º more caster with aftermarket tubular upper control arms. It's a good mod.

Another way to get more caster (or camber if you can't remove any more shims) is to use offset upper control arm shafts. They'll usually get you an extra 1º - 1-1/2º

On the camber, zero or even slightly negative is a small plus for cornering.

On the toe in, the shop manual says 1/8" -3/16", but that was superseded by a factory bulletin in the mid 50s. Radial tires will definitely not want much toe in.

The above deviations from the stock specs are my opinion. I think most agree with the general nature of them, but some may have their own ideas on the details.

since this is a sticky, thought I would ask the question here. My 55 Belair has stock, manual steering. I am planning on rebuilding the front end with the stock kit, including springs and rubber bushings from Ecklers. I run radial tires. I read where adding caster helps power steering systems. should I worry about changing the A-arm shafts or shafts with those with increased caster, or just plan on utilizing the stock arms and shafts (assuming they are good and not bent)? I know I can go shafts or A-arms with increased caster, but is it needed with the manual steering? Haven't torn it apart yet, so don't know the condition of the a-arm shafts, and whether I need to replace them or not. also, heard that Poly bushings will give you a squeak. is it best to stick with the rubber bushings?

 

Ricks information is spot on by my experience as a frame and front end tech from years gone by. I probably aligned thousands of 55-57 Chevys over the years when they were daily drivers for non car enthusiasts. His advice about radial tire toe is also right since radials have far less rolling resistance to side resistance ratio than bias tires. Too much toe will scrub radials faster than bias. Keep on mind my experience was mostly on original vehicles with lots of daily wear and the requirements for your new-tech higher performance builds result in the need for higher caster. I just put my 57 on the road first time in 28 years with lots of these upgrades and am having to learn to make it drive well with the combination of old and new tech, sorting it out is very satisfying.