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Old 06-12-2007, 01:24 PM
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Straight axle steering help!

Need some help in figuring our steering problem, steering is really touchy and the smallest of bumps upsets it. Really keeps your attention. I have put a square to the front wheels to make sure they are straight (90 degrees to the axel) then brought the toe in a few degrees. No help, I am posting picís of the set up in my gallery. I had to swap the spindles left to right and put the steering arms to the front and run a drag link. The steering tie rod goes to the passenger side steering arm I use an extra bolt on steering arm to do this. Will having the panhard bar going opposite (pass side frame to driver side axle) create any problems? Also the steering arms attached to the drag link tying them together are almost parallel to the rims. Could this affect the ackerman? Like I know what that is. All I know is itís a handful to drive, any help would be appreciated.
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Old 06-12-2007, 02:56 PM
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I did a bit of a search an discovered this http://eprints.usq.edu.au/archive/00...aPOPA-2005.pdf

It is a research paper by Cristina Elana Popa A grad student in Australia.

Go down the page and Ackerman is explained. She does a good job of explaining all steering principles if you care to read though it. section 2.3 concerns steering principles.
After reading most of her paper I have one comment. Some of the specifications are directed towards a vehicle that is being setup to autocross and won't be the best for the street. Street driven cars usually run a bit of positive or zero camber. the 1.something negative that she listed is for track cars only. with that amount of neg camber most street driven cars would eat a pair of tires in a couple hundred miles or less.

Toe in is set in inches or by metric measurements if you are so inclined. normally a solid front axle rig runs 1/8 to 3/16 toe in. The desired caster varies but most guys like to run about 5 degrees positive caster.
Can you show some photos of your steering linkage? Also check for any movement in that linkage.
Yes, with a cross leaf front spring it is normal to run a panhard rod to control side to side movement with a cross steer setup.

Last edited by Chopt 48; 06-12-2007 at 03:11 PM.
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Old 06-12-2007, 03:18 PM
F&J F&J is offline
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Those PDFs always lock my pc up so I can't read it..

Anyways, I don't think you can get a proper Ackerman angle with a suicide tierod. The hole in the steering arm needs to fall in line with a line from the center of kingpin to the middle of the rear axle; and all ackerman diagrams I've seen show the tierod on the backside (for straight axles, not independent)

The front wheels when steered to one side, has the inside wheel turning tighter than the outside wheel...it needs to do that because the 2 front wheels are turning on 2 different diameter circles.

If the tierod is up front, it's the opposite....the outer one is trying to turn tighter. My kid's da#m farm tractor is like that, and it's outer wheel always tears the lawn real bad.
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Old 06-12-2007, 05:26 PM
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Thanks guys. I posted some pic of my set up in my gallery if you want to look. Can I heat and bend the steering arms to get the right ackerman? Or not a good idea.
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Old 06-12-2007, 06:21 PM
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Quote:
Originally Posted by PureC4
Thanks guys. I posted some pic of my set up in my gallery if you want to look. Can I heat and bend the steering arms to get the right ackerman? Or not a good idea.
Yes & No.

Yes you can heat and bend the steering arms. Be sure to let everything cool naturally. No quenching or forced air.

No because you will probably not be able to bend the steering arms enough to correct the "Ackerman effect" due to interference with the rims.

I would suggest installing the steering arms as originally intended and then drop the steering arms by heating and bending. You could also cut off the original steering arms and purchase aftermarket dropped steering arms.

The panhard bar can be mounted as you suggested and should not cause any problems.
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Old 06-12-2007, 06:28 PM
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Found your new pics in your Project area, not gallery

I think you have 2 seperate problems;

1-the ackerman won't/can't be right for a straight axle with a solid tierod. But that wouldn't cause a twichy feel IMO.

2-The twichy feel could likely be that the stock VW pitman arm on the box is too long in comparision to the aftermarket steering arms?? Back to some of my kids tractors again....He has one that was way too touchy and he could not plow snow with it because it was hard to keep the steering wheel from going to full lock. We ended up making the steering arms on each spindle Longer, and the pitman arm Shorter. It made a huge difference.

I was looking at the old pic where you had your wire welder gun laying in the front trunk area. In that pic, I see where you tried to use 2 tierods like the stock beam did. Anyways, that pic shows that you own 4 arms to experiment with. I can't tell for sure, but are 2 arms a good bit shorter than the other 2? If so, try using the 2 longest arms for the tierod.

If that helps some, you could always get a spare stock VW pitman arm and experiment by drilling a new drag link mounting hole closer to the pitman shaft (to make it a "shorter" arm) What you are trying to do is change the ratio on the steering....instead of fast ratio or "quick steer", you want a slower steer.


It would be great if you can find a way to run the tierod on the back side to correct the ackerman, but with that beam extension in there, i can't tell if there is enough room left. The tierod out front should cause tire scrubbing on tighter turns...and probably a strange handling reaction in the tighter turns. However IMO, if the car is twtchy in straight ahead driving, I doubt the front tierod situation is causing that twichyness. So, try changing the ratio for now. EDIT: Skip swapping the arms because then you would end up with a shorter arm for the drag link, and that would cancel out putting the longer ones for the tierods. Try drilling a new hole in a spare pitman to try to diagose the twich.

Last edited by F&J; 06-12-2007 at 07:09 PM.
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Old 06-12-2007, 07:12 PM
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Ackerman is only important when making really tigh turns, driving straight down the road ackerman is un needed.

What you have sounds more like bump steer aka roll steer. That when a change in wheel height causes a change in toe.

Almost all cars are designed with some bump steer or more precisely roll steer. ( it's hard to get one without the other)

what you want is the tire to toe out slightly when the wheel moves up into the wheel well. This means when you turn a corner and the car rolls to the outside the outside wheel will gain toe out causing the car to turn less ( this is called roll understeer)

If you were to design it to toe in on bump, the car will turn more as it rolls causing it to roll more causing it to turn more...untill the car spins out or the driver looses control. Even if the driver doesn't allow the car to spinout it's a hard way to drive and a bit scary.

Now too much bump steer will make the car a real handfull since the car will be steering itself on every little change in pavement height.
Too much bump steer is anything greater than about 1/4" total change on fullsuspension travel.

Also make sure you have 1/16" to 1/8" toe in. You need to measure this for real, you can do it with a tap measure but thats another topic...

Keith
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Old 06-12-2007, 07:24 PM
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After looking through your pictures I think I see the problem.
It's the placement of your steering box and steering rod / arm.

You have it at a completely different plane from the tie rods. This causes the bump steer I was talking about.

Look at how the steering arm moves as the wheel travels up and down. The steering arm MUST travel in the exact same arc as the tie rod or bumpsteer.
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Old 06-12-2007, 09:27 PM
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Quote:
Originally Posted by 427v8
After looking through your pictures I think I see the problem.
It's the placement of your steering box and steering rod / arm.

You have it at a completely different plane from the tie rods. This causes the bump steer I was talking about.

Look at how the steering arm moves as the wheel travels up and down. The steering arm MUST travel in the exact same arc as the tie rod or bumpsteer.
I am lost, sorry guys. I cant move the drag link to the back side of the axle because of the tunnel in the pan. The steering was worse when I used two tie rods. Whats really strange is when I put a T square against the rim and axel to get a 90 on each side the pass side tire looks like it's toe'd out ??

Also, how would I get the steering arm to move in the same arc as the tie rod.
Bend the pitman arm?
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Old 06-12-2007, 10:11 PM
F&J F&J is offline
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So you never set the toe correctly?? If it has toe out, it will wander all over.

Since you have a sraight axle, you can accurately set it yourself.

There is a tool that was used on big trucks that allows you to put a scribe mark on the tire. You jack up the axle, put the tool with it's spring loaded needle against the tire tread, and spin the tire. Now you have a 100% accurate mark to measure from. WAY more accurate that someone measuring to the grooves in the tread.

So find a way to make that mark; maybe with a nail braced on something. Then let the jack down. Then measure the front of the tires to those 2 lines, then the back. I use a long 1"x1" piece of wood, sitting on 2 quart paint cans. I make a mark on the wood for each line on the tires, then set the cans & wood stick on the backside to compare. You need 1/8 to 3/16" toe in.

Hope your car is not too low to find a way to measure it in there !

Set your toe and repost how it handles. There are plenty of builders here to get it working right.
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Old 06-12-2007, 10:23 PM
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The comment was made about the angle of your steering link or "drag link". In this pic, it sure looks like you could level it by putting the heim joint UNDER the steering arm. Or would that make it hit the axle extension under the car???
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Old 06-13-2007, 05:40 AM
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Quote:
Originally Posted by PureC4
I am lost, sorry guys. I cant move the drag link to the back side of the axle because of the tunnel in the pan. The steering was worse when I used two tie rods. Whats really strange is when I put a T square against the rim and axel to get a 90 on each side the pass side tire looks like it's toe'd out ??

Also, how would I get the steering arm to move in the same arc as the tie rod.
Bend the pitman arm?
Too bad. you cannot fix something by just bending random parts.

I suggest you learn about steering systems and figure out how to put the links where they have to be.

An I agree about the toe. Set it properly.
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Old 06-16-2007, 10:00 AM
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Quote:
Originally Posted by F&J


The comment was made about the angle of your steering link or "drag link". In this pic, it sure looks like you could level it by putting the heim joint UNDER the steering arm. Or would that make it hit the axle extension under the car???
I Think there is enough clearence to move it to the bottom. Will try that and see if it helps. At this point even small improvements will be great.
Thanks all for the suggestions, my son and I appreciate it.
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Old 06-16-2007, 03:15 PM
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I agree to move it to the bottom. If it's still not level you could space it down. They do this on dirt modifieds to clear the frame if needed.
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Old 06-18-2007, 06:39 PM
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Quote:
Originally Posted by PureC4
I Think there is enough clearence to move it to the bottom. Will try that and see if it helps. At this point even small improvements will be great.
Thanks all for the suggestions, my son and I appreciate it.
Ok moved it to the bottom and raised it on the pitman arm to get it closer to level. Seems to have made it worse. Will check alignment tomorrow, over corrects really bad. Scares the ^$#@ out of ya!
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