The Stovebolt Site Forums The Shop Area Driveline Help Understanding Alignment Numbers

I need a little help with the alignment numbers that I just got. I replaced all 4 springs and shackles. These parts were bought from Eaton Springs and are the standard springs.

1951 Chevy Truck 1/2 ton, 16" Radials tires, 1954 235 engine. Complete frame off restorations with front sway bar added. I do have a 2 degree shim installed between axle and springs on both sides. The fat part is facing toward the back of the truck. The front end does not seem to have any loose/sloppy areas. I will be rechecking this again in a few days. The truck drives and goes down the road pretty good. I am not scared to drive it at 60 - 65 mph.

Here are the numbers. All values in degrees:

Left front Camber 0.0, Right front Camber 0.6

Left front caster 0.6, Right front Caster 1.3

Left front Toe In 0.15, Right front Toe In 0.15

Front Total Toe 0.29; Steer Ahead 0.00

Left rear Camber -0.5, Right rear -0.3

Left rear Toe 0.27, Right rear Toe 0.19

Rear Total Toe 0.46, Thrust Angle 0.04

Finally my Questions:

1. For a straight axle is the difference between the left & right front side camber that great in practice? I have read that solid axles are usually setup for the same amount of camber on each side.

2. Both front caster numbers seem to be lower than other post talk about. Does the difference between the two sides indicate a problem with the axle being level?

3. I have no idea about Toe In values. The numbers I keep seeing are in inches. I did find a formula for converting to degrees but I need to wait and check the tire size to convert.

4. Thrust Angle - is the number to high. What I have found is ideal the Thrust Angle should be 0.0, with no plus or minus. I was wondering on a truck this old if I should be worried about trying to have the frame checked to be sure it is straight just from the Thrust Angle number?

5. Also looking in the book the setting are displayed in degrees and minutes. Is there a conversion for straight angle readings?

As you can probably tell I have very little knowledge/understanding of the alignment numbers. I have studied several different materials and understand how the readings are generated. I just do not know how to interpret them to help identify if I need to start checking the front end for a problem or what area to check.

Thanks for any help that can be given.

1: They should be pretty much the same. The right side looks to be on spec, the left is within the spec range. I would suggest rechecking the bearings, make sure they are properly preloaded. That can give a false reading.
2: The Caster spec is 1/2 degree for your year truck, with a 1/2 degree plus/minus tolerance. The right side being more than the left could indicate either an out of level or twisted axle issue. If it's driving ok, I wouldn't worry too much about it. If it does bother you, you might put either the next size up wedge in the left, or go down a size in the right. A little extra caster will not hurt anything.
3: Toe looks ok to me. Once you your conversion, it should come out to 1/8".
4: .04 degrees is acceptable. I've seen newer cars with more that drive straight.
5:I can't really help you there, but I'm sure there's a conversion table somewhere. Jerry (Hotrod Lincoln) would probably know for sure where you can find one.
I wouldn't put too much concern in the numbers given for the rear, there are no adjustments. They do not look too bad at all. If the they were way out, indicating a swung axle or something bent, then there would be a concern.

Bill,

Thanks for the reply. Always a good feeling knowing if the numbers indicate a problem or not.
I was a little worried about the caster angle because all the post I read talked about 3-5 degree of caster. I think I will just leave the caster angle alone for now.
I will recheck the bearing torque this weekend.
Good to know that thrust angle is OK. From what I read about thrust angle it would turn out to be a job to correct. I did read that some thrust angle can be corrected when the front end is aligned. If this does not correct enough the frame has to be checked for straightness.

Thanks for the help and information. Got a little more educated about a different section of the truck.

Ditto to Bill's comments. The caster difference is actually beneficial, as it helps the truck run straight down a road with some drainage crown. Adjusting the caster approximately 1/2 degree more negative on the driver's side makes the front end lead slightly left, which helps it "climb" a drainage slope. Since almost all roads are sloped a little toward the shoulder for rain drainage, a little left lead is a good thing. You could increase the shim thickness a little for better return to center if you choose, but it will also increase turning effort.

There's very little to be done about the thrust angle without changing spring bushings, shackles, etc. The numbers don't look bad at all. Be sure the alignment shop knows how to adjust the "center point' of the steering gear. A lot of younger techs who deal mostly with rack and pinion steering have no idea how to adjust a worm and sector steering gear, and it's an important first step before moving along to other adjustments.
Jerry

Jerry,

Thanks for confirming the numbers being good. It always makes me feel better when more than one person agrees.
I forgot to add that the steering box had been rebuild before the alignment. The person who did the alignment is suppose to be very familiar with old vehicles and front straight axles. This was the first time I have used him. I will stop back by and just verify that he checked/adjusted the "center point" for the steering gear.

I think I will leave the front end alone for the time being and just drive it. Maybe after the summer if I do not like the steering I will revisit and try and find a local person who I can take the truck to and do a show and tell to help me understand what changes would be best.

Thanks for all the help. It makes me feel a lot better putting it on the road.