C10 Modern/Performance Alignments

[BMERDOC]

It seems that alignments aren't talked about enough on the forum and a starter thread encouraged me to talk more about alignments. Here is that thread:
http://67-72chevytrucks.com/vboard/s...94#post4933494

I wish to make this thread simple enough for all to understand but I will not start by explaining the elementary angles which are toe, caster, camber, and thrust angle. I encourage you to research these topics for yourself so that I may get on with the meat and potatoes of it all. I expect all disagreements to be handled in a delicate manner with a decent explanation of your disagreement and would ask that you thoroughly read the posts so that answer repetition is minimized.
If you have had an alignment and wish to discuss it please post a copy of your print out so that we have clarification.
This thread will discuss 2WD C10s from ’63-‘87 but if you bring up a specific example of another truck that this site is dedicated to, myself or someone else will be glad to address the situation. Keep in mind that the contents of this thread are for a modern alignment and will swing towards a performance oriented alignment. I will warn you if I feel a severe angle will burn tires up.
One last thing, I’m a car guy that knows about alignments. I am not an engineer for Goodyear, Michelin or Hunter.

[BMERDOC]

As I stated in the previous post...negative camber, positive caster, average of "Specified Range" Toe and "0" Thrust Angle. Follow these rules and your truck will handle and drive better than it ever has!

I will start by saying to check YOUR OWN vehicle for loose or bent parts and sagging springs. All bushings must be in good condition (be sure to check your trailing arm and panhard rod bushings!!), wheel bearings should be properly adjusted and no steering or suspension components can be bent. Keep you steering box, rag joint and column condition in mind also. Check your tire pressures and make sure they are even. If you let something slide expect your alignment to reflect it.

Never let a service center perform a Two Wheel alignment. They must refer to it as a Thrust Alignment or a Four Wheel Alignment . If they use either two of those terms you are in good shape and there is no need to question them further. Look for a shop that will work with you to align your vehicle as you wish. The rest of your truck is custom and your alignment soon will be. If they won't work with you find someone who will.

OK! The first angle is Thrust Angle. Thrust should be zero but .1 or -.1 will be fine. Consider a closer look if your Thrust Angle is closer to or over .2 (either positive or negative). This angle reflects how square the differential is to the chassis. If it is out of square it will cause the truck to rear steer like a fork lift and you will find yourself counter-steering to compensate for it. It will also affect the front toe alignment. If you see a vehicle tracking badly as it goes in a straight line either its bent or the Thrust Angle is waaaay off (ed. or they got a two wheel alignment). Again, make sure your trailing arm and panhard rod bushings are in great shape to insure the best possible alignment. Anything else affecting it is probably bent.

Moving to the front caster and camber will be aligned next. Front toe should be the last angle aligned as the other angles will cause the readings to move around.

NOTE!!! I will be aligning my truck in this thread in an experimental manner as I have little to no experience aligning a shimmed vehicle!! I will use my truck to show what alignment angles are feasible with this front suspension. This does not negate my knowledge of alignments, however.

Let’s talk about camber. First, camber should always be negative because when you enter a corner the tire top will want to tip to the outside of the vehicle, rolling over the contact patch. If your camber is 0 or positive expect it to handle poorly in turns because it is already on or past the contact patch of the tire. If it is negative it will roll onto the contact patch maximizing grip. Depending on how you want your truck to be set up have your aligner set it between -.25 to -2.00. -.25 is very reserved and -2.00 is the outer limits of a Daily Driver. For you guys wanting to take advantage of a modern alignment, request -1.00 to -1.5. You will experience some inner wear over the life of a set of tires if your alignment is set closer to -2.00. As a reference track cars usually ask for -3.00 but these are off road and are tossing into turns, setting the contact patch and don't really care much about tire life. For you lowered guys, this is a good rule of thumb so that you will know what to expect when you get your print out.

The next angle is Caster. You always want to dial in positive caster for self –centering steering and good straight line tracking. The more positive caster that is added the more the steering wheel wants to return to center so entering and exiting corners is improved and high speed stability is improved. If the caster is more towards negative then you will need more steering input to keep it in a straight line. As I said in the previous post you’ll notice that when you perform a u turn you can let the steering wheel go and it will want to spin back to center (research steering axis inclination). The Specific Range for my ’67 is 2.00 to 3.00. I would want 3.00 or more if I could achieve it. Again, I will be posting alignments on my truck and will provide specs that are realistic.

There is a theory that one wheel can be set with more positive camber (.25 to .50) than the other to compensate for road crown. It is true that the vehicle will want to “drift” in the more positive direction. I feel that making both sides equal is more desirable because unless your town is 90% crowned roads, your truck will want to “drift” to that side on flat roads. I would rather counter steer into a road crown so that my truck will glide straight at 80mph.

The last angle I want to talk about is Toe. I would stay within the confines of the Specified Range because toe is affected by steering and suspension more than any other angle. If the tie rods are too long or too short they will not pivot on the same plane as the lower control arm (bump steer). You lowered or raised guys may already be victims of bump steer and we don’t want to aggravate the situation. I will use my ’67 as an example again. The Specified Range is .08 to .15. Notice they are in the positive range. This is due to the fact that these trucks are front steer, that is to say the steering gear is ahead of the front crossmember. As the truck rolls the tires are pushed out to pull tension on the tie rods and center link giving the steering a tight, confident feel. If the toe is too much toward 0 the steering will tend to wander because the tie rods do not have enough tension on them and the joints will want to ”roll around” in the sockets, too far out and inner tire wear will occur. Remember, as strange as it sounds alignments are set statically and driven dynamically so I like to see an average of the range, so .15 - .08 = .07, .07/2 = .035, .15 - .035= .115, .08 + .035 = .115. A toe setting of .11 or .12 is acceptable. As the vehicle is driven imagine the numbers constantly changing, by setting average you are more likely to stay in the specified range and save tire wear. If more cornering performance is desired you can go more positive but stay in the range. As a side note for you guys that like to talk about alignments fractionally, 1/16th equals .18 which is mildly out of spec. I don’t know if I’d go that far on a street truck but wouldn’t hesitate on a truck I planned on tracking and didn’t care about tire wear.

I know I’m probably missing some stuff. I started this late last night and finished it up tonight. I know the chassis fabricators are probably gonna blow me outta the water but my information has been gathered over a life time of studying and on the job training. It is meant as Alignment 201 so be kind. Once again, I will be using my truck to find out what specs are achievable. I need to install poly trailing arm bushings, a panhard rod and a left upper A arm cross shaft so hopefully I’ll have the first posts up by Friday. I will include the measured thickness of the shims so that you can do the initial alignment before heading to the shop to save you time and possibly money. I hope I have helped you guys understand a little better about alignments and the benefits of straying away from the original specs. It is not a far stretch for me to say the original specs are scary and can be dangerous especially in a collision avoidance situation.

[BMERDOC]

67/68 Alignment specs:

[BMERDOC]

Some extra notes: Camber is a tire wearing angle but will not wear as harsh as toe. If toe is ok the the tires are rolling straight and camber will wear tires over the long term. Toe, however, will scrub the tire because it is "dragging" it as it rolls. Caster is a non wearing angle.

Tire pressures are up to you but I think that the 20 psi range is too low and the 40 psi range is too high for a street truck. Currently my pressures are at 35 psi. If you want to know more about tire pressure there are charts online that explain tire pressures affects on oversteer, understeer and neutral handling.

[BMERDOC]

"If the toe is too much toward 0 the steering will tend to wander because the tie rods do not have enough tension on them and the joints will want to ”roll around” in the sockets"

This is B.S. I put it in there as filler while writing the information so that I could come back later and word it properly, it somehow slipped through the cracks.

It is my belief that as the toe is set closer to 0, road feel is numbed. The truck would lack a certain confident feel. It may be good for a vehicle traveling in a straight line but not for a vehicle that you would actually want to dip in and out of corners with.