The Stovebolt Site Forums The Parking Lot Big Bolts Bump Steer

Hi guys,

My 47 1.5 ton has the front axel flipped to lower the truck. It has some MAJOR bump steer. do any of you fellas know the best way to eliminate that? I think what I need to do is, drill a hole higher up on the arm coming out of the steeriing box and attach the link to the new location...Please take a look at the pic and see what you think..
http://a1.sphotos.ak.fbcdn.net/hphotos-ak-snc6/189790_1468983705207_1852033637_858040_1182919_n.jpg

Thank you, John

You're one of several lately that have talked about a "flipped front axle" and I've yet to see a good picture or get my head wrapped around how this works or actually lowers the truck....

How does it work?

In my mind if you flipped the front axle (turned it over) you'd gain about 4" height and ground clerance.... and some poor geometry, which sounds like you have.

Grigg

If you do that you will lose much of your turning radius. I hope whoever welded that steel plate onto that axle knew what they were doing.

Looking at the photo, my guess is that "flipped axle" is being used to describe the front axle beam being mounted above the springs (with spacers to make it even higher) instead of below to raise the spindles relative to the frame and the rest of the truck (or lower the truck relative to the spindles and ground, just a matter of persective).

It would change the steering geometry but I don't understand well enough to say if better or worse and how much. But you would hope the original designer put in the effort to be fairly close to "best practical". One thing I am sure of is that if a new hole is drilled as mentioned in the pitman arm, closer to the steering box, the angular travel limit on the pitman arm will be same but the shorter effective arm will have 2 effects. One is that the steering efort should go down roughly in proportion to the shorter effective arm. The second effect is that the wheel cut angles will decrease and the turning circle will increase. A shorter pitman arm will make less linear travel in the drag link for the same angular travel which in turn will reduce the travel at the steering arm on the spindle. I would also want to be sure there was enough material left on the pitman arm for strength. Most stock pitman arms are enlarged around the drag link attachment point to keep the full section once the hole is taken out.

PLEASE tell me that's on some kind of show truck, not something that gets driven on the street to endanger a lot of unsuspecting fellow motorists! That thing's a rolling deathtrap!
Jerry

Grigg, if you turn the axle upside down that would only be a half flip! John's axle has been moved from under the springs to on top of the springs doing a full flip. John you could look at moving the steering box up, it would change the angle of the steering column a little bit but probably not to noticeable.I'm no engineer, this might be a dumb idea. Good luck

Flipping the axle is what was called raking the front end in my day. It serves no other purpose than to lower the front end. Since the steering axle is now very close to the frame, it is common for the steering axle to bump the frame. The only way I know of to eliminate this is to put the axle where it was when it left the factory.

A few post were deleted, please keep it professional from here on out.

Grigg

If a person desires a vehicle that was built with an I beam steering axle to be lowered, installing an IFS front clip or purchasing a dropped axle are the only two acceptable methods, in my opinion, of accomplishing this.

Truck gets driven everywhere...Not a "rolling death trap"... How can you say that with out asking how the truck drives? You have no idea whats going on. Just looking for some advise, not critisism!

What about the "rolling death trap" comment? Is that profesional? Com'on...

I believe you'll find that in some -maybe many- jurisdictions home modified steering components are illegal precisely because of the danger they present to others on the road .... considering the regulatory regime in CA, I wouldn't be surprised if it was so there

Bill

So all hot rods, street rods etc...are illegal then...99% of them have modified steering to some degree. I NEVER hear of anyone being hasseled over that...so there

Its an opinion and an observation. Without more info and pictures it's hard to say if it's true or not, but certainly could be. I will say that from the one picture posted I was not impressed either.

So a "flipped axle" is simply a spring under axle conversion, that's a whole lot easier for me to picture and understand.
The reverse of that, is a "spring over axle" or SOA seems popular with the jeep crowd looking for room to fit bigger tires.

Grigg

Impressed? The posted picture is of the stock configuration steering once the axel has been flipped.

What you saying is this, all profesional or non profesional comments are subject to your interpretation. So I will disagree with your decision to remove my post...

Grigg, compared to your well-illustrated and researched thread on front axle modifications and disc brake conversion, that one picture is ample reason for my opinion. I've also been the guy who cleans up after the wrecks caused by ignorant amateurs who modify things with no clue about what they're doing nor the dangers involved. I stand by my original comment.
Jerry

This forum has no need for mean spirited arguments and name calling, that is exactly why both sides of the earlier argument were deleted. They added nothing to the forum and only made the both of you look bad.

I'm willing to go along with this thread and see if we can learn anything from you, and perhaps you will learn something from everyone else, you were originaly asking for ideas and help I thought.

One last chance, if this thread heads downhill again don’t be surprised if the whole thing is gone.

not "some degree of modified steering", but home modified steering components, as in drilling the aging original pitman .... for that matter, where I live you'd have major problems with inspectors over that shortened frame

Johnny, you might find it a bit easier to have a conversation about things here if you refrain from the grade school comebacks, "so there" sure won't work with your DMV or insurance company .... please remember that you're the one who originally said "It has some MAJOR bump steer. do any of you fellas know the best way to eliminate that?" you've gotten some honest thoughts from folks with decades of experience with these trucks, if you don't want to hear what they have to say, than you shouldn't ask for opinions

Bill

Asking for opinions and receiving derogatory comments like the one from hotrod Lincoln or whatever his name is, and your response of, “so there” are not pleasant. If you want professionalism like Grigg is talking about then be professional yourself. Maybe Hotrod Lincoln is hyper-sensitive to this because as he said, cleans up the mess on the highways. I bought this truck with the suspension the way it is. I’m just trying to gather ideas of how to improve the bump steer. If I need to make an entire new arm I will, but man, the rolling death trap comment, is ridiculous. He doesn’t know how the truck drives, or even asked…Just “pooped” off with that. No one knows everything…So be frickin nice!
As for deleting the thread, man I don’t care, go ahead…

The bump steer issue is obvious even to the casual observer. The detail point is how to deal with it in a safe and logical manner. Respect to everyone is first, then we can all roll up our sleeves and help if its still wanted. Don

you are exactly right, your response was not pleasant, a simple "I have no idea what the CA law says about back yard engineering" might have been better

Bill

Bill, your right..Im sorry. I got a bit "riled up", and for that I appoligize. We have a really cool show here once a year and I want to drive the truck all over with out this issue. Im going to look into raising the steering box by possibly making a mount that bolts to the frame, although it would create other issues...maybe. If I make a new arm the range of motion will shorten because the arm will be shorter. That would mean a larger turning radius becasue the shorter arm wont extend as far right? I If that is the case, I dont think it will be an issue, since the truck is so short...Opinions????

Johnnyc47; Try this website below. I'm building a '45 GMC dually pickup with a 350/700r4 setup and am thinking of lowering the truck the same way he has [axel flipped] with the same steering box set up and c-notched frame he did.I have all the parts-just no time to do it. Good luck.

http://www.jalopyjournal.com/forum/showthread.php?t=245130

Jeff, if you choose to follow the example of the thread you referenced, be aware that they have made one major mistake in their setup. The steering gear should have been rotated 90 degrees so the Pitman arm hangs straight down with the steering centered. The way they have it mounted in their picture series will still induce some bump steer issues as the axle travels through its range of motion. By fabricating a bracket to forward-mount a newer design steering gear, a lot of problems can be avoided.

One very important improvement with the modern steering gear is the possibility of adding a collapsible steering shaft which will not impale a driver in case of a serious front end crash. It's no fun watching the paramedics cut the roof off an older vehicle to retrieve the body of a driver with a steering shaft through his chest.
Jerry

Johnny, You may be able to use something like this. http://www.timbren.com/index.htm They have been around for a while. I have not used them. However, a trailer factory in CA has been using them with composite springs for about 5 years with good success. I have ordered one of their trailers. http://trailer1update.com/Frameless%20BD/waste3.html I am going to give it a try. If I am not satisfied with it, I will put a Neway trailing arm suspension under it which will add about 500 lbs.

Jerry; Point well taken.The steering gear I'm using is the whole setup[power steering box,column w/collapsible shaft] taken out of the donor truck [1976 GMC 4x4].The way the guy in the thread has the steering box mounted back toward the axel looks like it would have a problem with bump steer.I'm going to mount it up towards the front of the '45 frame where it was originally mounted in the donor truck where it worked just fine and it had a lift kit and big tires Rotating it 90 degrees should help also.The jury is still out on the lowering thing with the axel flip.I may have trouble with the 7.50-20s scraping the fenders-they're already close. Thanks, Jeff

Think about how the original steering gear mounts, behind the axle with the Pitman arm hanging down beside the frame rail. When the new gear is mounted forward of the axle, it needs to have a vertical position that allows the drag link to run parallel to the ground, and also parallel to the frame, same as the original drag link but pointing back, not forward. These dimensions needs to be established with weight on the wheels, or at least with the axle at the anticipated ride height.

Some creative bracket fabrication might be necessary to put the steering gear in the right place. Don't forget to consider the swing of the tire and wheel as you decide on where to put the steering gear! On the circle track cars, I like to mock up brackets with 1/2" plywood, and when they fit right, then I duplicate them in steel plate. Plywood is a lot easier to manipulate than steel, and a screwup is less expensive and easier to correct.
Jerry

johnny, i just got back in to town and got your pm reply on my original question about this. i will call you this week and we can pick each other's brains on this issue. thanks-DVZ