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sstock #1289343 Fri Nov 30 2018 09:37 AM
Joined: Jan 2009
Posts: 246
S
Shop Shark
By added more toe in does that keep the bump steer down ?

sal moreno #1289357 Fri Nov 30 2018 02:32 PM
Joined: Mar 2014
Posts: 3,070
J
'Bolter
Sal, what are you talking about with 2 springs in the front? I'm confused...do you mean you took out all the spring leaves but 2?


Jon

1952 1/2 ton with 1959 235
T5 with 3.07 rear end
Jon G #1289362 Fri Nov 30 2018 02:50 PM
Joined: Jan 2009
Posts: 246
S
Shop Shark
Well I don’t know know if that’s what did but they built new spring s for the truck cause there’s only two those aren’t the original springs .

sal moreno #1289372 Fri Nov 30 2018 03:41 PM
Joined: Feb 2000
Posts: 4,528
J
'Bolter
Here is picture from GM showing the difference in '36 and '37 truck steering. Pay attention to the compression and rebound walk. If you end up with the drag link not on center of its theoretical path, you can end up with bump steer. This why everyone says the drag link must be level.

To explain caster angle, picture a shopping cart, it will easily go any direction you point it because of negative caster. Now picture one of the old time dragsters with the front axle laid way back, they would go dead straight almost by them selves because of all the positive caster. You enough want positive caster to go straight with little input, yet still be able to steer.

Toe-in adjustment causes similar driving problems. The tires just don't know which way to go so they hunt around for a straight path to follow. In actual driving, the tires should be dead ahead straight. The toe-in as set for the front of the tires ( at spindle hight ) to be 1/8" closer together and rear of tires 1/8" farther apart. When you are driving, all the slop in the steering joints is compressed and the tires end up dead ahead.

Attached Images
Steering angles.jpg (217.58 KB, 142 downloads)
sal moreno #1289376 Fri Nov 30 2018 04:33 PM
Joined: Feb 2004
Posts: 25,002
H
Kettle Custodian (pot stirrer)
Joe, the idea that people who don't have a basic understanding of steering and suspension geometry are modifying their vehicles simply to get a desired visual effect is downright terrifying. It's sort of like getting brain surgery at the corner drug store- - - - -from the computer jockey cashier, not the pharmacist!
Jerry


"Freedom's just another word for nothing left to lose"
Kris Kristofferson

Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!

There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self.
Ernest Hemingway

WAG MORE- - - - - -BARK LESS!
sal moreno #1289407 Fri Nov 30 2018 08:02 PM
Joined: Feb 2000
Posts: 4,528
J
'Bolter

sal moreno #1289468 Sat Dec 01 2018 03:33 AM
Joined: Mar 2004
Posts: 5,618
M
'Bolter
In a nut shell, as you travel over a bump in the road at a high rate of speed the up and down movement in the suspension causes the wheels to turn left and right making the vehicle change direction. This happens because the geometry changes even though you were holding the wheel straight! By removing all but two springs, the up and down travel of the axle is now way greater than the steering was designed to handle which in turn amplifies the bump steer.

Toe-In is what helps keep the truck running straight when you take your hands off the wheel. It also helps automatically return the wheels to straight after making a turn.

Mike B smile

sal moreno #1289471 Sat Dec 01 2018 03:52 AM
Joined: Feb 2004
Posts: 25,002
H
Kettle Custodian (pot stirrer)
Caster also helps the wheels to self-center. Because of the geometry of a properly-designed steering system, as the wheels turn away from straight ahead, the front of the vehicle is lifted. Gravity pushing down on the vehicle makes the wheels try to return to center. As the caster angle is increased, the tendency to self-center after a turn also increases. Vehicles with power steering usually have much more caster than those with manual steering because the increased steering effort is handled by the power assist. All this is designed into the car or truck when it's manufactured, and thoroughly tested before a steering system goes into production. Making radical (or sometimes minor) modifications without totally re-engineering the steering and suspension often results in not just annoying, but sometimes deadly changes in the handling characteristics.
Jerry


"Freedom's just another word for nothing left to lose"
Kris Kristofferson

Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!

There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self.
Ernest Hemingway

WAG MORE- - - - - -BARK LESS!
sal moreno #1289473 Sat Dec 01 2018 04:02 AM
Joined: Feb 2000
Posts: 4,528
J
'Bolter
Mike, thats not entirely true, the motion of the front does cause the bump steer only if the drag link is not where it's suppose to be. The amount of spring travel or the number of leafs has nothing to do with the steering, assuming the steering and all adjustments are correct. On these trucks, the axle travel has pretty limited travel so it still comes back to either caster, toe-in or geometry of the steering links.

Not to be a pain, but it's caster that makes the wheels return from a corner and what keeps it going straight, toe-in also does, but the caster angle is the more important one of the two. Go back and look at the picture two posts up, the arc of the drag link needs to follow the arc of the springs as closely as possible. If you start out with the drag link at either end of the arc, you get bump steer, even with a dead on everything right front end, you still get some bump steer, it's just the way they work.

sal moreno #1289482 Sat Dec 01 2018 04:38 AM
Joined: Feb 2004
Posts: 25,002
H
Kettle Custodian (pot stirrer)
The same concept applies to independent suspension. Unless the length and position of the tie rods is approximately the same as the length of the lower control arm, as the suspension moves through jounce and rebound, bump steer will be induced. People who mismatch a rack & pinion steering gear and an independent suspension system can have the same, or worse problems with the vehicle self-steering as an altered ride height vehicle with a straight axle. The tie rod, steering knuckle, and lower control arm needs to form pretty much of a rectangle with the wheels pointed straight ahead, with the inner tie rod pivot and the lower control arm pivot in virtually the same position, side to side.
Jerry


"Freedom's just another word for nothing left to lose"
Kris Kristofferson

Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!

There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self.
Ernest Hemingway

WAG MORE- - - - - -BARK LESS!
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