How do I correct bumpsteer?

[Russell Ashley]

I finally got my truck together and took it for a drive and it's a big disappointment. I had driven it up and down the smooth street I live on and it was OK, but on less than smooth streets it's not acceptable. I have the CPP power steering kit that uses a GM box mounted outside the frame in front of the axle. I had some doubts about this kit when I installed it but it was written up positively in magazines so I figured it must be OK. My concern then, and now, is that it is mounted between the shackle end of the spring and the axle, and also the drag link is so short, which I think would contribute to bump steer. My question now is how to correct this? Anyone else used this kit satisfactorily? Any ideas anyone?

[sqrlnts]

From the very little that I know the angle of the drag link should be parallel to the frame to minimize bump steer. Looks like yours is angled steeply.

[Denee007]

I can't relate on the drivability cause my truck will be on the jack stands for a long time. My truck suspension is hanging here, but the drag link will be pretty steep When on the ground. I was thinking to call Sid@dropped axles and see if he can weld the pitman arm hole and remachine so I can put the draglink the other direction, maybe it's an idea to consider?
Oh darn, my idea doesn't apply to your setup? I just looked at your setup after I posted.


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[Denee007]

Would Not having shocks make it worse? Do you have shocks mounted?
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[_Ogre]

russell; the picture you show has no sheet metal on the truck
the sheet metal and everything else will lower your truck quite a bit
that may help, but...

i drove these trucks stock for years, i thought that bump steer was inherent to anything with a straight axle
not technically bump steer, but anything with a straight axle has a tendency to veer off at every bump
the heavier the load, the less the veer in the steer

[mknittle]

Sorry to say you will always have a problem with that set upThe drag link is too short! the springs and the drag link are moving in radically different arcs. when I build anything with a straight axle I put the steering box so that when the wheels are centered {strieght head} drag link is at the center of the spring bushing on the fixed end Not the shackle end.
I have not had any bump steer problems doing it this way.

[G&R's57GMC]

A. The front spring mount fixed, rear shackle.

B. Drag link parallel to the ground.

C. When you get tired of messing with this set up and still want a solid axle try this set up
http://www.nolimitparts.com/prodinfo...ber=PS%2DSA%2D

Finally, a rack and pinion power steering system for your classic truck. Perfectly designed to give you the best steering you can have with a straight axle. All kits include new steering arms to correct accerman, and reduce bumpsteer. More exhaust clearance that a stock box. Works with any height springs. You can use a stock or aftermarket steering column. A power steering pump is required. Includes: **Power Rack & Pinion, ** Tie Rod Ends** Rack & Pinion Mount Kit, ** Steering Arms ** Flaming River u-joint for Rack & Pinion ** All necessary hardware ****KIT WILL NOT WORK WITH THE STOCK 3 SPEED COLUMN SHIFT WILL NOT WORK WITH DROPPED AXLE!!!

[buggy5872]

You need to move your box forward like mknittle said. Here is a pic of my box. its a little hard to see and of course a 2 ton truck but the same priniple applies. Mine is lined up with the front spring eye.

I get bump steer but it is because it rides like a bucking bronco empty and I think the weels are off the ground at times. Thats a differnt kind of bump steer. Rides fine when pulling our 5th wheel.

[Russell Ashley]

Thanks for your replies, everyone. I took the pic in my first post right after I finished installing the steering. The frame was suspended on jack stands so that's why the drag link is at an angle. It's level with the truck sitting on it's wheels. I do have the shocks mounted also. With the short drag link and the steering box mounted at the shackle end of the spring I don't see any way to ever make it drive satisfactorily. I was concerned about that when I first installed it, but as I mentioned, this setup had been written about in magazines, so I assumed it must not be too bad. This setup wasn't cheap so I hate to spend more money for something that I shouldn't have to buy anyway.
The rack and pinion setup looks like a possible alternative but the ad says it won't work with a stock three speed steering column, which I have and want to keep. I have already shortened the column as much as possible so I might call them and see if I could make it work. I'd like to be able to fix it without having to remove the front sheetmetal and engine.

[mknittle]

Originally Posted by Russell Ashley

Thanks for your replies, everyone. I took the pic in my first post right after I finished installing the steering. The frame was suspended on jack stands so that's why the drag link is at an angle. It's level with the truck sitting on it's wheels. I do have the shocks mounted also. With the short drag link and the steering box mounted at the shackle end of the spring I don't see any way to ever make it drive satisfactorily. I was concerned about that when I first installed it, but as I mentioned, this setup had been written about in magazines, so I assumed it must not be too bad. This setup wasn't cheap so I hate to spend more money for something that I shouldn't have to buy anyway.
The rack and pinion setup looks like a possible alternative but the ad says it won't work with a stock three speed steering column, which I have and want to keep. I have already shortened the column as much as possible so I might call them and see if I could make it work. I'd like to be able to fix it without having to remove the front sheetmetal and engine.

I noticed most magizine editors of late dont know what the parts are called or even know anything about the tools.

[Denee007]

Perhaps a steering stabilizer would be a good investment? Ive been searching the net, and looks as though the straight axles need the extra help. There are many out there, I just posted this one as it seems to be popular. ; )

I just don't understand about the difference which side the steering gear is on(front or behind) It's affixed to the frame. I wouldn't think the truck knows the difference where the force is coming from to steer.

Another thing, Russel, are you using the stock caster shim? I can't tell in the photo, but is it installed with the thin portion towards the front? Sid at dropped axles talked me into a 6 degree shimming; will it help? ; ). Tell you in a year or so; )

http://www.posiesrodsandcustoms.com/...eering-damper/
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[Dunenutt]

On the 4x4's, it's a common problem. A dropped pitman arm solves alot of it. Here is an example. There are alot of options, google dropped pitman arm.

http://offroaddesign.com/catalog/steeringcorrection.htm

[robin58]

The one thing I don't like about that Nolimit steering set up is the fact it requires you to use a slip shaft to your column to compensate for the movement of the rack with your axle. Steering columns aren't designed to slide in and out except under sudden impact for safety.

I'd be more inclined to look at a cross steer set up but that's just my $0.02

[buggy5872]

It does not matter if the box is in the front or rear, it is the relationship of the moving parts. The pivoit point of the spring and the drag link need to be in the same place so every thing moves at the same rate and same time. If set up correctly bump steer should not come into play. I have run tons of strait axle frontends with out a stabilzer with no problems. Now if you get into monster big/wide tires.......then you need a stabilizer to compensate for what the steering was not designed to handle.

[gab50]

I have the same system and the best that I came up with was the aft end of the draglink about 1\2" higher than the front. My theory was as the spring compresses the center line of the axle walks forward a bit and by having the rear draglink slightly up the pivot point also arcs forward and so the steering was really quite good. I live where the road is quite rough and rolly and it did fine and on a smooth road it was great. I now have installed a Sid's dropped axle and am seeing I might not be able to get it the way I want and so will have to do something. I am looking at cross steering as the real way to fix this problem short of a whole new system. I wouldn't do it again knowing what I know.

[62ChevyII]

Originally Posted by Russell Ashley

I finally got my truck together and took it for a drive and it's a big disappointment. I had driven it up and down the smooth street I live on and it was OK, but on less than smooth streets it's not acceptable. I have the CPP power steering kit that uses a GM box mounted outside the frame in front of the axle. I had some doubts about this kit when I installed it but it was written up positively in magazines so I figured it must be OK. My concern then, and now, is that it is mounted between the shackle end of the spring and the axle, and also the drag link is so short, which I think would contribute to bump steer. My question now is how to correct this? Anyone else used this kit satisfactorily? Any ideas anyone?

As has been stated by others, it is due to the arc each component is traveling in being different. A short arc moves forward and backwards much more than a long arc for the same amount of vertical travel. The difference in forward and backward movement is where your bump steer comes from. The leaf spring is basically a long arm pivoting at the rear and it's allowed to move forward and backward via the front shackle. It's bad enough that the length of the arc is so vastly different but then the drag link is pivoting on the opposite end that the spring is pivoting on so it is even worse. Looks like a poor design to me... To minimize the bump steer, the steering box should be at the rear, next to the fixed end of the spring.

[robin58]

Looks like a poor design to me... To minimize the bump steer, the steering box should be at the rear, next to the fixed end of the spring

A Saginaw conversion is probably one of the most widely done PS swaps there is. There is physically no way to have this type box at the rear spring end.

Before spending a fortune on revising the whole front steering, personally I'd take a look at how drivers of other vehicles have handled bump steer as it is definitely not exclusive to Chevy owners of vehicles converted with different steering boxes. There are countless "bump steer isolator kits" sold (e.g. for Porsche 911's, Datsun Z series, etc as well as offroad applications). They may not be an immediate swap out, but they can give some idea on how to limit the effect of bump steer to at least make it enjoyable to drive.

[62ChevyII]

Originally Posted by robin58

A Saginaw conversion is probably one of the most widely done PS swaps there is. There is physically no way to have this type box at the rear spring end.

Yeah, I didn't mean he could put this particular steering box back there. I just mean geometry-wise that is better location the way I understand it.

[Denee007]

This is very disturbing! There's no way to remedy this? For me, I'm a long way from driving it, so I'm leary of this setup now! So if Russel and I were to "lengthen" the draglink, we'd be less likely to encounter bumpsteer? Darn, and I just welded that triangle piece in for me, looks like I should totally reposition my gear anyway? Eh, another problem to be remedied, right Russel!

Originally Posted by mknittle

Sorry to say you will always have a problem with that set upThe drag link is too short! the springs and the drag link are moving in radically different arcs. when I build anything with a straight axle I put the steering box so that when the wheels are centered {strieght head} drag link is at the center of the spring bushing on the fixed end Not the shackle end.
I have not had any bump steer problems doing it this way.

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[Russell Ashley]

[QUOTE=Denee007;5408405]This is very disturbing! There's no way to remedy this? For me, I'm a long way from driving it, so I'm leary of this setup now! So if Russel and I were to "lengthen" the draglink, we'd be less likely to encounter bumpsteer? Darn, and I just welded that triangle piece in for me, looks like I should totally reposition my gear anyway? Eh, another problem to be remedied, right Russel!





[I've had quite a few straight axle two wheel drive trucks so I know you can make them drive and ride OK. A steering damper might help some and also a set of very stiff shocks to help keep the axle from moving so readily, but I doubt I'm ever going to be satisfied with this setup. Wish I'd gone with my gut feel when I first looked at doing it. I'm going to be away from the truck for a couple of days but when I get back to it I'm going to look at what will be involved in possibly converting it to a cross steer setup. I've got $$$ invested in disk brakes on the straight axle as well as the money spent on the p/s conversion so I'd like to find a solution that keeps this steering box and also won't cost too much. I think my first trip might be to the 4X4 shop to see if they have any suggestions.

[Denee007]

Russel, what is a cross steer setup?
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[robin58]

Cross steer is pretty popular with the 32 Fawd crowd. Look for Unisteer and it will give you an idea.

E.G. http://www.rjays.com/Maval/cross-steer-01.htm

[Denee007]

Thank you Robin, I did another search too. Just getting a little over my head, looks easy enough haha!

http://www.jimmeyerracing.com/a-body.html
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[mknittle]

Originally Posted by Denee007

Thank you Robin, I did another search too. Just getting a little over my head, looks easy enough haha!

http://www.jimmeyerracing.com/a-body.html
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it isn't any harder than what you have. Just make sure the tie rod and drag links are parallel. and some extra bracing where the steering box is mounted wouldnt hurt.

[mknittle]

Originally Posted by robin58

The one thing I don't like about that Nolimit steering set up is the fact it requires you to use a slip shaft to your column to compensate for the movement of the rack with your axle. Steering columns aren't designed to slide in and out except under sudden impact for safety.

I'd be more inclined to look at a cross steer set up but that's just my $0.02

me too! I got into that once before on here. That design sucks pond water!
most cars that I have driven with rack and pinion were twitchy.Add leaf springs and that slip joint and ....No thanks!