Re: 2WD C10 Modern/Performance Alignments
I will have to check but I think I read 3/4" forward. Not sure if thats center to center or from the leading edge. I'd love to be a little more scientific but time restraints....Its late. I'm gonna do some research tomorrow.
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Re: 2WD C10 Modern/Performance Alignments
doc, I moved mine, on our JT build, 1" forward, and 1/8" out. This is from CL of the OE socket, to CL of the new socket. Keep up the good work.
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Re: 2WD C10 Modern/Performance Alignments
Thanks Rob! I will assume that you got 8 or 9 degrees of caster with a 1" movement?
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Re: 2WD C10 Modern/Performance Alignments
yes, without much mis-match in the shims
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Swapping Upper Control Arms ...
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Re: 2WD C10 Modern/Performance Alignments
Well I had my truck re-aligned today. Final camber was right around -0.5 degrees on each side, caster is +4.39 & +4.5 degrees. That was as close as he could get. Removed all but 1 shim on the driver's side, still have a stack of shims under 1 bolt on the passenger side.
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Re: 2WD C10 Modern/Performance Alignments
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Re: 2WD C10 Modern/Performance Alignments
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Drive home it did nice. Biggest thing I've noticed is less bump steer than before, felt good on the big S-curve on my way home. |
Re: 2WD C10 Modern/Performance Alignments
This thread is awesome. Nick, I am very appreciative if the time that you are putting into this for all of us!!!
So I have a shiny new caster camber gauge on the way and icsnt wait to take a whack at my own alignment. My concern is that ive read that the wheels must be turned exactly 20* in each direction when performing an alignment. I know that turnplates can be purchased but they are well out of my price range. I read a few pages back that a couple pieces of tile and greese can be used. Can you go into this in more detail? Is there a better way to measure this? (My idea involves fabricating some metal plates to use as a guide, but if there is a string, tape measure, or any other method that works I'd love to hear about it. Thanks in advance everybody. |
Re: 2WD C10 Modern/Performance Alignments
Nick,
Thanks for the lengthy discourse on your alignment specs and theories. It got me on the right track for my 82 Chevy Shortbox. I recently replaced the upper ball joints, idler arm, pitman arm, and all the tie rod ends, but had to have a shop do the lower ball joints, since I had no press and couldn't even get the old joint tapers to release. That shop also did an alignment. The truck drove worse than ever, and I mean ever! So I started asking questions, and I found a shop where the guys had fixed a lot of Chevy frames, where they crack at the steering box, and who said that they regularly put 8° of caster on big 4-wheel drive pickups, whereafter they drive like a dream. I tried to take the truck back to the original shop, but my appointment time came and they blew me off, so I demanded a refund, and took the truck to Les Schwab, where they have the same alignment machine as in your pictures. Sweet! My thrust angle started out (left) at -.35°, and I can't do anything about that. Eight degrees sounded a little extreme for me, but I liked your idea of a lot of caster. I requested 3.5° of caster on the right, and 3.25° on the left, and got 3.7° right and 3.3° left. Pretty good, and still within a half-degree side to side. I liked your argument about camber, but the book and the alignment tech said slightly positive, and exactly equal side to side, so I ended up with .5° positive camber on both wheels. OK. The tech said it was the difference in caster that compensates for road crown pull, but I still like the idea of slightly less camber on the left. Finally, the book calls for .13° to .25° toe-in (.26° to .50° total), and using your midrange method, that puts each wheel at .18° with .36° total toe-in. I ended up at .20° for a total toe of .40°, which is right about the midrange average. OK. The bottom line? The truck drives like brand new now, and if I feel like I want to tweak something in the future, Les Schwab said they would happily do it, and not turn me away when I set an appointment. The alignment cost me $56 there. So anyway, you gave me a big push in the right direction, and if you're still out there, thanks. Mike |
Re: 2WD C10 Modern/Performance Alignments
@hairlesshobo
I appreciate your gusto! But you know, a good alignment is pretty cheap, about $60. Anyway, generally, without knowing anything about your guage, you also have to lock the brakes to do a caster sweep, and that means all 4 brakes, not just the e-brake. So you need to jimmy-rig something to jam the brake pedal, or get the special tool to do it. It's just a bar with a pad and a stop. It works just like the thing that holds the screen door open on your front door. Just open the door as far as you want, set the little metal thingy, and it stays. When I first bought my truck I aligned it just by feel. It wasn't great, but it drove OK. I think you'll have better results using some tools on it, but you'll never get it as fine-tuned as a guy using a Black Widow alignment machine. Good luck, and have fun. |
Re: 2WD C10 Modern/Performance Alignments
Thanks for the feedback Mike! It is good to see this info really working for people! The original factory specs are horrible at best. A truck drives like a truck for a reason but a better alignment can improve the way it drives. It was my intent to show you guys the factory specs and how they could be modified for a better driving truck and what happens to the alignment as the truck is modified. I wanted you guys to be able to read an alignment sheet and understand what it all means so that you can make your own educated judgement on how to modiy your trucks specs while at the alignment shop. I can't wait to see more feedback from others!
As far as your trucks alignment goes, it makes me courious to see how far out the Thrust Angle has to be before the truck is "dog tracking" so bad that you can visually see it. I'm starting to think that as results come in from other guys we will see some rather large numbers. I would venture to say at this point that -.35 might not be so bad. |
Re: 2WD C10 Modern/Performance Alignments
Mike, everywhere I have read failed to mention anything about the brakes needing to be locked in order to use a caster camber gauge. Would you be willing to explain why? Iljke to know how/why something affects something else when I do it, and I definitely want to make sure I take my time and do it right.
Also, i have yet to find a shop in town that does even a decent job at an alignment, especially one that you can ask for something other than what their computer says without them arguing with you. Plus, every shop I've been to here wants a minimum of 75 for a real alignment. |
Re: 2WD C10 Modern/Performance Alignments
I never explained that the brakes needed to be locked down either. I have been under the assumption that most would sub out the alignment. I haven't explained at home alignment because I have had a machine at my disposal for years now and haven't had to perform an alignment in that manner. As far as good alignment shops, I think its because you toss the key to them and tell them to align it. Leaving them to their own devices can cause them to be lazy. You would have to search out a shop that would be willing to work with you on the specs.
In short, the brakes need to be locked so that the wheels don't move as you complete the caster sweep. The lock tool is picturd in a previous post. A steering lock is also shown to keep the steering wheel straight as toe is adjusted. |
Re: 2WD C10 Modern/Performance Alignments
I see how not locking the brakes could negatively effect it when turning the wheel side to side. If it were to roll at all it would negate the point of sweeping left to right. Thanks for clearing this up. So just to recap what I have learned from here and from uncle Google, tell me if I am missing anything. I am going to take a whack at doing an alignment for the first time tomorrow.
Have I missed anything in this? I plan to use the string & caster/camber gauge method. I will first setup a completely level surface, then box off string square around the vehicle. I will set caster, then camber using the gauge. I will then set toe using the string as a guide. I would also like to check if my rear end is lined up properly. I plan to measure from a point on the outside of the axle, just inside of the rear tire to the first u bolt of the lower control arm. I will do this on each side and then compare the measurements. If they are off, I will adjust accordingly. Is this a reliable method for checking the "alignment" of the rear axle without a fancy machine or is there a better do-it-yourself method? I am very excited to take a whack at my own alignments. I feel that it has the potential to be VERY handy for as long as I am building and restoring vehicles, as well as save me a lot of money. Thanks again for all of the pointers everyone! -Steve |
Re: 2WD C10 Modern/Performance Alignments
As rusty as I am at home brewed alignments I'd say you are on the money. If you wanted to, after your caster/camber set up, you could reset the strings to match thrust and set your toe according to this angle. You'd only have to tweak the strings to match the angle. It may be time consuming and not worth it considering we are learning that the older trucks have much more angle that can't be adjusted out than I am currently used to. Have fun and if it messes with your head walk away!!!
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Re: 2WD C10 Modern/Performance Alignments
I am thrilled to hear that. So I assume my idea for checking if the axle is straight would work then?
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Re: 2WD C10 Modern/Performance Alignments
good info doc thanx for the rite up
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Re: 2WD C10 Modern/Performance Alignments
Nick,
My truck was a rebuilder, put together by a couple of guys who did a repectable job; there really aren't any rattles or squeaks to speak of... But the truck was hit at the front left frame rail, and I think that unsquared it a little, giving me the left thrust angle. Push the left rail back, and it turns the rear axle to the left. The alignment guy said he has seen these old Chevy trucks with angles of plus or minus .45°, and it didn't hurt the alignment or make the truck pull, or make it hard to center the steering wheel. I would imagine that to actually be visible following a rig, it would have to be off by 5 degrees or more. Anyway, I've driven the truck for a couple of days now, and it corners better than ever, drives straighter and truer, and the wheel unwinds from turns in a predictable and positive manner. So I decided to spend a thousand bucks on new wheels and tires! Thanks again! Mike |
Re: 2WD C10 Modern/Performance Alignments
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Re: 2WD C10 Modern/Performance Alignments
Well I tried to take a whack at doing an alignment but quickly found that the garage I was working in just didn't have the space I needed to set everything up. I think I am going to try it again next weekend in the parking lot of my complex or my job. I will post back when I know more.
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Re: 2WD C10 Modern/Performance Alignments
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In refreshing my memory about alignment theory, I found the following about toe-in: Ideal toe-in is 0°. But that is at road speed. Tires have a certain amount of "rolling resistance," which is the rearward force exerted on the wheel by the road, and by air pressure, as it is pushed forward by the vehicle frame. There is a certain amount of flexibility in the A-arm bushings (assuming they are the stock rubber ones), and this flexibility responds to the rolling resistance. At highway speeds, the static toe-in angle is negated by the suspension system flexibility, and the total rolling toe-in ends up being 0°. The static toe specifications assume the factory designed A-arm bushings, which are much more flexible than, say, polyurethane bushings. Therefore, any vehicle with polyurethane or custom performance bushings will probably require far less static toe in than a stock vehicle. Such vehicles with polyurethane bushings using factory toe-in specifications will probably be unstable, and may be observed to wander at high speeds, because of too much toe-in. Mike |
Re: 2WD C10 Modern/Performance Alignments
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I like Nick's idea of negative camber on the front wheels, and if it's set at 1° or 1.25°, I can't see where it would cause any undesirable steering anomalies, but if anyone tries it, I would definitely to read about the results. |
Re: 2WD C10 Modern/Performance Alignments
Is that right? You have a BMW (325 I assume) that has more than 6° of caster?
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Re: 2WD C10 Modern/Performance Alignments
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Many years ago I was working at a Goodyear shop (I used to be an ASE certified Master Auto Technician), and a big four-wheel-drive Ford truck came in with horrible wheel alignment. The thing was so big it wouldn't fit on the alignment machine, and so we were reduced to aligning it with tape measures. With the rear axle, we did pretty much exactly what you did, which was loosen up the U-bolts and slide the axle back and forth until we had the parallel and cross frame measurements within about a 16th of an inch. Many leaf spring locator pads have a pin to positively locate the spring to the axle, but fortunately this one didn't, and if it did, we would have ground it off. We couldn't measure the results of our efforts, but the before-and-after drive results were a world of difference away. |
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