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Discussion Starter · #1 ·
In planning for a solid axle I was wondering what is the best way to mount the springs. I have seen shackles up front or solid mounts up front with shackles in the rear. What are some of the pros and cons of each mounting configuration?
 

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I've always put the shackles up front, which if I have thought this out right when the shackle swings forward it creates more positive caster. I load the axle with (depending on use ) 12 to 18 degrees, positive caster. I think this is one of the most debated issues... :)
 

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Yes, it certaily is debated a lot, and when looking at factory setups it seems they use both ways also! My stock straight axle on the Austin was shackles in the rear, so I went back that way, but most the Tri 5 Chevys I've put axles (5 of them) were shackles up front.
I honestly don't think it means anything either way, so I'd do whatever works the easiest for you.
More important things to consider are kingpin angle, and drag link angle. Those things will drastically affect the way the car handles, and much more concern than shackles front or rear.
 

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Discussion Starter · #4 ·
Yeah, even the HAMB threads I read today were mostly debate on which was better. I will have to do some reading on how to set up all of the angles correctly.
 

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I agree, however kingpin angle is a bit confusing, because there are assentialy two. One ( scub point ) being were if you draw a line threw the top of the kingpin to the ground, the line should intersect threw the center of the tire. Here's were wheel offset will change that making steering rough threw the corners if the center of the tire moves outside the scrub point.
The other kingpin angle ( caster ) is how far back the top of the pin faces back towards the passenger compartment ( or fire wall ) or away. Always think of it as if there's a ten dollar bill at the top of the pin positive caster means its closer to you were negative is further away.
Both of these angles work well together in corners and will help lift the car and return the steering wheel to the center.
 

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On another gasser forum, I read that the fixed end of the spring should be on the same side of the axle as the steering box, but Ive seen it both ways. I put the shackles out front on my Henry J, but couldn't make rear steering work so I'm breaking this "rule" myself. If you have a panhard bar parallel with the drag link (cross steer) I can't see it should make any differance.
 

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I always look at the straight axle trucks and have observed shakles at either end. They also have lots of other apparatus attached too but it must work ok because they always blast past me on the hiway at 90 mph!
 

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I have a theory of shackle position and Prostreet steve and I already wrote about this but i want to clarify the correct way by diagram. Is this normal ride height Position #1 and then a weight shift to position #2 the correct shackle positoning for best situation of shackle angles.. One time I saw a willys gasser for sale and the shackles were all the way back almost touching the frame and It hadn't gone over any bumps yet so I guess they would slam into the frame on a bump. since then i always thought the shackles should be a good distance away so they don't hit the frame.
Am I right about this theory or am I off?
 

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Mario, if photo 1 is, as it sits, and 2 is when it loads. I would think there would be plenty clearance, and no worry of hitting the frame. I like to start the curb position just forward 90, but most likely would make little difference.
thanks Steve, I have posted pics of the 1st attempt I made on the mg project thread. They are forward. My latest position is pretty much the same forward probably about 60*.
 

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OKAY, I hope I am not stirring the pot here cuz there is so much I need to know about the old stuff, (which is all new to me),, but, how about ackerman angle? Are there any choices of straight or drop axles that come with built in ackerman angle? Or do they all have it built into them?

Ideal ackerman angle is going to be different for each of us when we move axles forward or rearward at either end.

Now I figure this will probably need clarification to someone reading this eventually, so, I will attempt it here without pictures.

Consider the top view of a car and specifically steering angles. To set up an idea situation for ackerman angle, you would draw a line through the steering pivot point at each wheel (the ball joint) and then through the kingpin pivot point ,,,, ideally that imaginary line would point to the center of the rear axle.

Now let me say it in a different way,,( but it does the exact same thing). If it is a rear steer set up, meaning that the steering joint is behind the axle, then the imaginary line starts first at the kingpin and travels through the steering arm ball joint and then points at the center of the rear axle.

This ackerman angle is really important for proper tire wear and CORNERING,,,,yes, CORNERING, something, we do not think about alot in the gasser word :) but ackerman angles are a big part of the puzzle, of course along with all the other angles mentioned above in this thread. Additionally it helps make for a good daily driver or to and from events.

So, can you guys school me on the choices we have on this ackerman angle stuff as it relates to straight/drop axles?

56 VIC - Tom
 

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Tom , you just schooled me! LOL but seriously after looking at this web page, https://www.google.com/search?q=ack...VK5Pr0QGHpYD4Cw&ved=0CDkQsAQ&biw=1760&bih=860 , I have to say that the ackermann angle is more for independent suspension vehicles. On a straight axle , leaf spring setup with steering arms, handling will be at some disadvantage and at that point the ackermann angle is really not as influencial in that case I would say. This is only my opinion but the other guys would be able to add to this. When I drive a gasser Im not expecting to hit an exit ramp real fast , if you know what I mean.
MM
 

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Thanks for the input,,and I definately agree that we should not be trying to outrun anybody on off ramps with these gassers. :D
 

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I have spent far too much time looking at everything pertaining to ackerman angle, and as it applies to my straight axle. So much so that when I built my Austin I was sure it would be ill handling, and some even said a "death trap" because of the leading tierod and steering setup. Believe me, it can drive you nuts and cause many a sleepless night!
I finally just decided to weld it up, and test drive it when I was done. I figured if I approached it by working my way up in speed until I felt something weird, at the worst I'd redo it if it didn't work. After all the fretting, and nightmares, everything worked out great. It drives straight on the freeway, and no shimmy or death wobble. Handles nice in the corners, even with less than smooth roads, and is a pleasure to drive, even up to 100 mph. Haven't had it over that, and in the 1/8th mile I doubt I'll ever break 100 mph.
So my suggestion is to make sure your kingpin angle is in the 7-10 degree range, keep your drag link as level as possible, if you use a panhard bar keep it level too, and the rest will fall into place.
 

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So image #2 is under lead?




I have a theory of shackle position and Prostreet steve and I already wrote about this but i want to clarify the correct way by diagram. Is this normal ride height Position #1 and then a weight shift to position #2 the correct shackle positoning for best situation of shackle angles.. One time I saw a willys gasser for sale and the shackles were all the way back almost touching the frame and It hadn't gone over any bumps yet so I guess they would slam into the frame on a bump. since then i always thought the shackles should be a good distance away so they don't hit the frame.
Am I right about this theory or am I off?
 
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