Ackerman vs reverse

skipnrocks · Jun 28, 2017

So my buggy turns ok. But not super sharp. But I noticed the last time out that the outside tire turns significantly sharper than the inside. Then I got to thinking this is backwards than what I thought was supposed to happen. So my question is is this normal good or bad and can it be swapped.

This is on a Dana 6 front with high steer arms. Psc 2.5x8 double ended ram mounted in an artec front truss. So fairly common setup. But it's quite dramatic difference between steering angles on each tire

TBItoy · Jun 28, 2017

You'll have to get new high steer arms and/or remount your steering ram if you want to "fix" ackerman

What kind of steering arms do you have?

ridered3 · Jun 28, 2017

Here is a thread about Ackerman in a little red wagon, but lots of discussion about the theory behind it too.

http://www.hardlinecrawlers.com/forums/index.php?topic=50823.0

Ackerman is one of those topics that folks seem to have various opinions on.

skipnrocks · Jun 28, 2017

TBItoy said:
You'll have to get new high steer arms and/or remount your steering ram if you want to "fix" ackerman

What kind of steering arms do you have?

I don't remember the brand. They are a set of springless. I want to say their about 8.5 in from king pin to mount hole

skipnrocks · Jun 28, 2017

I have spent all morning on google and can't seem to find concrete data on how to correct it. Only one arrival suggested moving the conestor rods closer at the knuckle to reduce it. But if I had a direction I would start moving forward with it. I can't move the ram much. There isn't a lot of wiggle room in the artec trus

skipnrocks · Jun 28, 2017

So I have a theory. I wish I could draw this. But moving the ram isn't a very good option so let's see if I can describe it. Right now if you draw a line perpendicular to the front axle the heim attaches on that line. But if I move that heim in a little so it is medial of the perpendicular line it will tune the inside tire more and the outside less. Not sure if this makes sense but a lot of the high steer arms I have seen are a little L shaped. And in the drawing on the red wagon you can see the mount holes are medial of that line also.

Thoughrs?

tiny · Jun 28, 2017

On the wagon, the tie rods are behind the kingpin/ball joints. So you have to continue that line past the kingpin pivot in the same direction. To correct your Ackerman you would need to move your tie rod mounting locations out. Towards the wheel.

skipnrocks · Jun 28, 2017

I did read up a little from the red wagon. And then went out and measures my arms. I'm at 7.5 from king pin to mount. And then straight line through the steering arm center of bolt to center of king pin puts me perpendicular to the axle.

Also I broke a stud so maybe altering the arm a little to allow a bolt to go through the arm to the oem arm would be good. Then move the bolt in a little off center. I'm not sure how much it will take to make a difference.

skipnrocks · Jun 28, 2017

tiny said:
On the wagon, the tie rods are behind the kingpin/ball joints. So you have to continue that line past the kingpin pivot in the same direction. To correct your Ackerman you would need to move your tie rod mounting locations out. Towards the wheel.

.

I didn't consider that. I assumed that it wouldn't matter front or back. I read up on the north west fab ones. They have their bolt lined up with the inside bolts on the knuckle I guess that had influenced my thought. Now I need to rethink this a little.

I wonder why the hole never lines up with the oem one cast into the knuckle. Seems like that one should be correct?

TBItoy · Jun 28, 2017

SBJeepn said:
.

I didn't consider that. I assumed that it wouldn't matter front or back. I read up on the north west fab ones. They have their bolt lined up with the inside bolts on the knuckle I guess that had influenced my thought. Now I need to rethink this a little.

I wonder why the hole never lines up with the oem one cast into the knuckle. Seems like that one should be correct?

Artec (and others) sell arms that line up with the stock cast in steering arm.

Mounting a DE ram in close to the axle helps with the geometry also.

paradisepwoffrd · Jun 28, 2017

Re:

If we are just talking ackermann.

Draw a line or pull a string from center on rear axle to the center of front kingpins. If the steering is in the rear, the tierod bolt hole needs to be along that line. If steering is up front extended the line out past the kingpin. the tierod bolt hole in the steering arm should be in this line.

The factory steering arm tierod hole is likely close enough.

Moving the tierod/ram closer to the kingpin increases the amount of travel/rotation for that ram stroke. But it decreases the amount of turning force for the tire.

Scrub radius is another common issue among offroad rigs. Some argue it should be neutral, some say it helps.

skipnrocks · Jun 29, 2017

Will something as small as a half inch help in adjustment on for this? Like if I went from a 7.5in arm to an 8 inch arm

croes · Jun 29, 2017

Jesse Haines runs reverse ackerman intentionally on some of his buggies with spools in the back. Sounds like yours is far too aggressive, mine is setup with reverse ackerman and maybe turns the outside tire 2 degrees more. It has crazy bite with spools f&r and I hardly ever have to back up with 45 degrees of steering w/ rcv's. I can one shot tight turns on bump and hustle courses where the majority of people can't. :****:

tiny · Jun 29, 2017

wrong direction, to change Ackerman. Move the tie rod location sideways on the arm, toward the wheel to make it correct. Honestly don't worry about it. Get as much steering angle as your axle shafts will let you. Leave the hole centered for 0 Ackerman and shorten the arm as much as you can to give you the most turning angle. Give yourself 2 degrees of safety off of the smallest angle your shafts bind at. Or clearance them to get a little more and even them up. Real PITA.
the difference between 0 Ackerman and correct Ackerman on a trail rig ain't going to mean much. If your going from reverse Ackerman to correct Ackerman, yeah sure. You would tell a difference.

skipnrocks · Jun 29, 2017

tiny said:
wrong direction, to change Ackerman. Move the tie rod location sideways on the arm, toward the wheel to make it correct. Honestly don't worry about it. Get as much steering angle as your axle shafts will let you. Leave the hole centered for 0 Ackerman and shorten the arm as much as you can to give you the most turning angle. Give yourself 2 degrees of safety off of the smallest angle your shafts bind at. Or clearance them to get a little more and even them up. Real PITA.
the difference between 0 Ackerman and correct Ackerman on a trail rig ain't going to mean much. If your going from reverse Ackerman to correct Ackerman, yeah sure. You would tell a difference.

That's what I need to do. My shafts are clearances to run 50 ish degrees. Through branik. I'd love to use that

skipnrocks · Jun 29, 2017

So I had a good talk with north west fab. They were awesome. They said the best way to correct was line up using the stock steering arm hole.

paradisepwoffrd · Jun 29, 2017

Re: Re: Ackerman vs reverse

SBJeepn said:
So I had a good talk with north west fab. They were awesome. They said the best way to correct was line up using the stock steering arm hole.

That, and get more travel to use all your turning angle.

skipnrocks · Jul 2, 2017

So after talking to north west fab I decided to redrill the holes at 5.5 inch and .5 in further lateral. And now I have perfect Ackerman within a couple degrees of each other and can easily turn steering stop to steering stop.

Now my question is what angle would oem stops be set at and second what is the max angle of a gm steering knuckle if I remove the stop bolt?

paradisepwoffrd · Jul 2, 2017

Re: Re: Ackerman vs reverse

SBJeepn said:
So after talking to north west fab I decided to redrill the holes at 5.5 inch and .5 in further lateral. And now I have perfect Ackerman within a couple degrees of each other and can easily turn steering stop to steering stop.

Now my question is what angle would oem stops be set at and second what is the max angle of a gm steering knuckle if I remove the stop bolt?

Turn the stops all the way in, rotate the knuckles until joints bind, back off a few deg, reset stops.

skipnrocks · Jul 2, 2017

I pulled the stops completely and turned full lock and still could run a piece of cardboard from the front through the back at full lock. I still need to jack it up and spin it but I think it's good. I can't tell you how elated I am for all that extra steering. And correct geometry.