QUESTION: Steering with arms POINTNG FORWARD...pros/cons????

The total performance front steer arms WILL NOT clear ford drum brakes. And they look like ****...... I tried em and sent em back....

 

After reading this thread I had to go study my '82 Chev 4X4 PU and I'm kinda stumped. An imaginary line from the tie rod end through the centerline of the ball joints doesn't come anywhere near the center of the rear, yet it steers just fine. There has to be more to it than just worrying about Ackerman. One thing I did notice is that the ball joints seem at more of an angle to the axle, which leans the tires into the turn alot more than the old Ford setup. If you look at a straight axle 4X4 at full lock, those tires are leaning WAY over. My '95 Chevy PU with the torsion bar front end also has the tie rods in front, so it definitely works, half the vehicles Detroit ever built have it in front of the axle.

 

Check this out

http://www.nationaltbucketalliance.com/tech_info/ch***is/ackerman/Ackerman.asp

 

That's a great read

 

Thanks for posting this. I was going to post a big long explanation of this concept, but without the illustrations, as the "rest of the story" with respect to Ackerman's principle. Thank you.
Pete

 

In regard to the link to the National T Bucket Alliance site:

Although the explanation sounds and looks good on paper,I still don't believe you can bend the steering arms enough to effect a true Ackerman with drum brakes on the front.I can only envision two possible scenarios where it might work:

1)Use a super offset(reversed center)wheel and locate the arms in the space between the tire and the edge of the backing plate.

2)Extend the length of the steering arm so that it is actually in front of the tire.

Neither possibility seems to be practical or esthetically pleasing.

One other consideration is that with the arms positioned like that,the wheels will describe radically different arcs in relation to the actual movement of the tie rod.It is kind of difficult for me to explain as I am not an engineer but as the tie rod moves in a linear track and converts the motion to an arc(the wheel pivoting about the king pin axis)there is gradual change in the rate of motion(the sharper the angle,the less the travel ).Or maybe it won't.

 

There have been a number of vehicles thta were designed for and ran front steer setups. The same principles apply wether it's straight axle, a-arm, cross steer, rack/pinion.
some cars its measured thru the king pins, some the ball joints.
When your puttin a rod togeater sometimes ya pay's you nickle and takes yor chances. Could run true, could be the Drunkin Monkey, or THE DEATH WOBBLE.

 

Bottom line, in my mind anyway, is that just swapping the spindles from side to side to get the tierod out front will give you problems EVERY time. Thats proven and fully accepted.

Bending the arms outward and lengthening the tierod to get as close as possible to the correct Ackerman will improve the situation.
If you can't get it perfect...well, thats how it goes...but you WILL get an improvement in the amount of tire scrub during tight turns.

I'm not convinced its worth doing anything radical to get it just a little closer...like deep offset wheels etc. That can bring its own problems into the mix. I'd prefer stock offset on the wheels with the Ackerman just set as close as possible.
The closer you get the Ackerman to perfect, the sharper you need to turn the wheels to notice there's still a problem.

EG:You won't notice a problem out on the highway because you just aren't cutting the wheels far enough in turns to get the misalignment to become an issue.

 

The new Rod & Custom Mag. arrived yesterday and in it is featured Total Performance's new King T. Guess what? It has the tie rod leading the way. With all the liability that companies face, it would seem that their arrangement must produce a satisfactory steering situation, even though Mr. Ackerman has been woefully snubbed.

 

I used to have a '98 with the same setup. Don't know how yours is, but mine had a little tire scrub when turned at full lock. Drove fine otherwise, just irritated me in parking lots. I had the 30" factory tires FWIW.

 

I think I'd spend the time up front to engineer a system with conventional tie rod location rather than take the easy way out and spend all the time trying to force it to work right after the fact. I took this picture just to show that a suicide front end does not force you to mount the tie rod out front. It can be done. I think it looks good and I know he drives the wheels off of it, so it must work well.

 

that's how i currently have mine off of the top brake mounting bolts. it looks p***ible on this car but looks like **** on mine since it is higher to clear my suicide perch. It does work great though. I have no problems..

I'm going to do some cad mock-ups this weekend to see what's possible with front steer and ford drums. I'll be sure to post them to the thread...

I think it may be possible for me to come close to ackerman since i have a fairly long wheel base.

Can someone give me the outside diameter of a ford tie rod end? I'm currently using heims and will be converting. I'd like to make my drawing as accurately as possible.

 

Pretty much all straight axle 4x4's have kingpins. Its not really the same as a early ford frontend, but they definetely still have a kingpin axis.

Another stock front steer car is a late model chevy truck. I worked a little on a 03 chevy (2wd) which was a front steer. As it was said, the only problem with front steer is getting the ackerman right. Lots of road race cars run front steer, but that is because they want reverse ackerman, which is bad for a street car.

 

Doesn't answer the question, But I finally know what you guys mean when you talk about Ackerman The illusrations are great.

 

Well i did some quick measurements last night and have determined that it is nearly impossible to get close to ackerman with front steer and ford brakes.

The problem is that the centerline of the kingpin is 7/8" of an inch from the backing plate. Since 5/8" heims are are 1 1/2 in diamter and ford rod ends are 1 3/4" the best you can do is have them just parallel to the kingpin (thus those imaginary lines head to infinity). In order to get close to ackerman the centerline of your rod end would need to be roughly even with the backing plate (this will depend on your wheelbase, axle with etc but is pretty close for most cars).

The only way to get close would be to bend your arm down so you could help the rod end miss the backing plate. Without a major drop (which may look like ****) you aren't going to do much better than getting the lines to intersect a few yards behind the car.

One thing to keep in mind is that most cars do not have true ackerman. Even old fords in their stock configuration. It's just a general guideline to help the car steer better. I think with a little planning and careful fabwork you could get it "good enough" in this setup.

 

Why don't you run them behind and bend your tie rod? I've had this set up for 12 years and never a problem.

-JAM

 

I have a 27 roadster with front mounted tierod and it drives OK, no noticable scrub unless in a tight turn, its a hot rod not a F1 car, take a look at a new full size pick up and what ****py tire scrub they have on hard turns, I say dont try and over engineer an old design that works fine for normal use

 

Jam, you have a closer pic of that? Anyone else tried this? I am at this same point with my front suspension. Other than the risk of having the tie-rod play bumper, no one had ever mentioned to me about Ackerman or how what I was doing would affect it. I had just seen this done so many times that, steering performance wasn't something I ever heard anyone talk about. So, now I am looking at correcting this. I had thought about adding some kind of stands to bring the tie-rod tall enough to clear my perch or hang a little under to clear my wishbones. Simply bending the tie-rod sounds like a great idea...almost too simple, but might be just the solution that will work for me.

 

FWIW. I vaguely remember some specifics when I was setting up my 41 Pontiac front suspension rebuild and couldn't get the ackerman exact. - Street tires have a certain amount of "slip angle". +/- 8* as I recall. The difference in turning angle with proper ackerman is about 2 *. I'm sure the exact math is available somewhere. The point is, in normal street use, with normal flexible sidewall tires, if you get it close it will drive like it is perfect. If you can't get Ackerman angles, set it up to get equal turn on both wheels (which is less than 3 degrees off of the Ackerman angle) and it will drive fine.
Can't remember if Bias or Radials had the greater slip angle (thus more forgiving) but a tire guy would know.
Slip angle is the "X" factor that allows non ackerman factory setups to work fine.

 

Sorry Boys. Jumped here from another post and didn't realize this one was 8 months old.
Kirk, any follow up on what you did and how it worked?