Would this make me steer when I bump?

I am having some problems with bumpy roads. On smooth roads I'm great but on bumpy back roads I'm all over. Would this pitman arm make that happen? I'm a '53 Chevy 3100 with a straigth axle and power steering. I have a steering stabilizer and everything is tight on my steering components. My wheels have been checked for toe-in but I'm still all over. PO did the upgrades but something about this doesn't look right? Any ideas?

 

how long is that drag link?? I'm not familiar with the chevy truck front end setup but from the looks of it it may have been a cross steer setup originally and then converted to a drag link? if that's the case, with such a short (at least it looks that way from this angle) drag link you may not be able to get rid of the bump steer.

also, it kinda looks like the tie rod end could bind up under compression of the suspension. is there room for full range of motion??

 

It looks like maybe you have some leafs missing from the leaf springs to get it lower. That makes the ride softer so the I-beam can bounce up and down a little more than normal when you hit a bump. With that setup with the short drag link from the pitman arm to the spindle, it seems like any large up and down movement of the I beam would cause that short arm to swing through a short arc, which would make that arm pull on the spindle a little every time you hit a bump, which is what bump steer is. So that probably explains it. If you could stiffen up the springs a little that might help a little, like maybe replace those with some de-arched leaf springs with the full set of springs?

 

It appears the original steering arm has been cut off and a fabbed upper arm has been added, but I can't really tell how it attaches to the pittman arm which appears to have been heated and bent up (?). Looks pretty cobbled up regardless. Do you have a side view?

 

The drag is just about a foot long.

 

Some leafs have been removed to lower the stance

 

why not just remove the shock and jack up the suspension and see if the steering changes throughout the range of motion..

basically bump steer is caused when the steering arm moves through a different arc to the wheel - hopefully you can see what part of the geometry is wrong. hard to tell from here.

'course, an alignment shop could probably help too.

 

and you wonder why you have bump steer

 

Here are a couple of more shots...

 

Looks to me that you need a much longer drag link.

 

I see the idea, it is similar to a '80 chevy 4X4. Look at one in the junk yard, the arm that is attached to the spindle curves to the back adding length to the drag link.

 

I would agree. This looks just like an 85' Chevy full size Blazer I have. That was a production car and it worked fine. However, they were know for some bump steer. A lot of off road guys will convert to an aftermarket cross steer set up. Is that something you can consider?

 

My setup seems to be similar to the kit offered by Classic Performance Prod. with the exception of the pitman arm.

http://www.classicperform.com/Store/1947_59_Trucks/4754PSKS.htm
http://www.classicperform.com/tech_articles/Power-Steering-Trucks/Power-Steering-Trucks.htm

That's why I'm a little confused. Why would they sell/design a system that is going to lead to so much bump steer.

 

A "foot long" is bragging rights, but not on a drag link!

You'll always have bump steer unless you dramatically increase the length of the drag link or go with a cross-steering system.

Can't tell if it's feasible from the photos, but my suggestion is go with the cross-steer setup. You might be able to fab up a rack and pinion setup, but I'm thinking a Vega steering box/cross steering is your best bet.

 

First my disclaimer: I don't know what I'm talking about.

That being said, it looks to me like the drag link is not parallel to leaf spring. Actually, I don't think it is that simple to describe, but it's close. As it bounces up and down, if the arc traveled by the drag link from its fixed point on the pitman arm to the steering arm is significantly different from the arc traveled by the axle from its spring's solid attachment point to the axle's attachment point on the spring, then you will get bump steer. It looks to me like the line from the leaf spring eye to the axle attachment is nearly horizontal and the drag link is not. It looks to me like the pitman arm is bent up too high. But I don't know much and the picture may not be representing the way it really sits. I could easily be wrong.

 

Is this the stock steering setup, draglink etc.?

The drag link does look overly short.

That said, how much tire pressure are you running?
Front shocks real stiff?
High tire pressure or stiff shocks can create problems running offroad.

Solid axle front ends seem to float around on the stutter bumps when running offroad.
In fact, darned near any suspension will do that.
Especially so when the speed is coordinated with the stutter bumps distance apart.
Slowing down or speeding up seems to help.

How does the truck handle on paved streets?

Keep in mind that the maximum tire pressure indicated on the tire sidewall is not necessarily correct for your vehicle.
Small example: My new at the time 88 Mustang 5.0 liter GT came with 35# in the tires.
Done by the dealer and the tire sidewalls indicated 35# max load rating.
I was beginning to wonder if I could live with the car the 2nd day I had it.

I finally found a sticker on the passenger door jamb that said 30#.
Made all the difference in the world.

 

On paved city street it handles great. It's just the bumpy back roads to my house.

It's not the stock steering for these trucks. From what I can tell the PO installed something similar to the kit I mentioned in the post above from Classic Performance in order to install power steering.

 

I would not waste my time with that suspension at all.
I know exactly what you're going through as I rebuilt a stock suspension entirely and still cleaned out all the ditches along the road.
Those trucks weigh alot up front and the suspensions are not made for that road at those speeds. These were farm trucks for the farm. thats all...
I would pull that baby out of there and install an alternative setup.
I have had a lots of luck with Must 2. It liturally makes the truck handle like a sportscar and you're as low as you'd like.

 

I ran a similar setup on my '37 chevy truck for a short time - it sucked bad enough that I changed it immediately.

Bump steer is all about matched geometry. Your suspension travels on an arc (of sorts) having your drag link travel on the SAME ARC is what eliminates bump steer (think of it working like a parallel 4 bar set up) when you mismatch these lengths - you get conflicting arcs = bumpsteer.

You can bet your bottom dollar that any recent factory set up similar to yours has arc lengths very well matched.

 

Here's a great article on early suspension geometry:

http://www.rodandcustommagazine.com/techarticles/135_0312_solid_axle_front_suspension_details/

 

Nice article...thanks

 

Lots of good advice in this thread...here's my $.02

It's safe to say that the drag link is too short, relative to the leaf springs. Keep in mind that one end of the leaf is on a shackle, which allows the effective length of the spring to change as the suspension deflects. So, the leaf spring length varies whereas the drag link length is fixed...and the compensation for those conflicting lengths is translated as bump steer.

The conflicting arcs are defined as the distance from the end of your leaf spring to the axle centerline (call that Arc 1) and the distance from your pitman arm to the axle centerline (call that Arc 2...it is basicaly the length of your drag link).

Crosssteering would resolve it, as would moving the steering box closer to the spring mount.

The steering stabilizer is a lateral control device...assuming it is mounted from the tie rod to the frame...and therefore would control steering "shake", typically caused by not having enough caster...but it likely wouldn't be a cause, or a cure, for the bumpsteer.

My $.02

 

I thought you had a gasser with straight axle so I opened the post to take a look. Your photo shows a stock solid axle which is not a straight axle.

 

my apologies....wrong term . stock solid axle....in other words not MII

 

NO APOLOGY NEEDED. Straight axle high riders have changed geometry and different issues.

 

that does look just like the kit offered by cpp. have you tried talking to them about bumpsteer problems? i hear all the time that you cant lower these trucks with mono leafs and a dropped axle. you have to do one or the other or you will encounter bumpsteer problems. but i was also told that if you lower these trucks dramatically with the stock suspension that all you have to do is bend the steering arm back to the stock geometry. it looks like the previous owner tried to bend the pitman arm back, but only far enough for it to work. it doesnt look anything close to stock geometry. my drag link is 15.5 inches long but from where the pitman arm connects to where it ties into the spindle its only about 12 inches. you might also want to try to bring this up on the stovebolt page. heres some quick pics i just took of my stock 50 chevy 1/2 ton. hope this helps
http://i132.photobucket.com/albums/q29/playinsafe44/100_0612.jpg
http://i132.photobucket.com/albums/q29/playinsafe44/100_0624.jpg
http://i132.photobucket.com/albums/q29/playinsafe44/100_0623.jpg
http://i132.photobucket.com/albums/q29/playinsafe44/100_0622.jpg

 

i just checked out the cpp products and they offer a dropped pitman arm for lowered trucks. i would think all you would have to do is bend the arm to where the drag link is parrallel and lever to the frame when the wheels are straight. and get it to where the tie rod ends are also level. i want to know what fixes this problem. i want to lower one of my trucks with the stock axle one of these days and i defenitally dont want any more bumpsteer the it has already has

 

I sent a message to cpp this morning, haven't heard anything yet. I've also posted on the stovebolt.

I'll let ya know what I found out.

 

sorry to hear about your steering problem. when you do find out who made it please post it, don't want anyone else having same grief. if it is a poor install by po. please post pic's of your solution. they also have a toyota 4x4 steering box conversion that is available for your truck. good luck!

 

I meant to post on this earlier- I think the majority of the problem may lie in the angle on the pitman arm. see how c.p.p.'s (great products'by the way) is reeeeally short by comparison?

the way yours is now, it moves the drag link in 2 arcs-meaning that if the axle were "upset" (meaning driven down a very uneven surface with any speed behind it at all) the box is going to force the wheels to move around alot. ALOT. kind of like a bow and arrow effect. (when combined with the natural effect of the "leaf spring dance")

I would imagine that there is also a point during a sweeping turn when the steering seems to "quicken" when the rate of both arcs change at the same time.

don't know if this would fix anything, but I bet the cpp pitman would make a positive difference.