What height does bumps steer become an issue??

[smoknbarrels]

I am bagging my truck at the moment, but I wanna know how low I car drive it, until bump steer becomes a problem (or start happening?).

I am setting it up so that the control arm will touch the ground when deflated, so i figure I'll drive the truck with the front crossmember about 4 inch off the ground, will I have bump steer problems with that setup?

arms, crossmember, and mounting locations are all still stock. but I do have drop spindles installed.

[N2TRUX]

Originally Posted by smoknbarrels

...I am setting it up so that the control arm will touch the ground when deflated.....

For safety, I suggest you set it so the lowest part of the truck is no less than 3/4" off the ground. Imagine blowing a bag or line at 60+mph. If your suspension makes contact with the road, it's not going top be a "controlled skid".

[vin63]

It's not so much the height of your vehicle as it is the steering arm geometry. If your steering arm is on the same hoizontal plane and remains parallel to the lower control arm through your designed suspension travel, there will be minimal bump steer - this is independent of the ride height. Do you have a photo of your steering arms in relation to the lower control arms?

[smoknbarrels]

I could set it up so that when deflated it will be 3/4" from the ground, that sounds like a good idea.

but as far as geometry, well its all stock other then drop spindles, so the angle of the upper ball joint is still quite sharp when sitting at my wanted ride height.

what causes the bumpsteer? the upper balljoints angles I thought?

I just figure that since there are a lot of guys out there that still use factory arms, that maybe there was a ride height magic number that bumpsteer starts happening at.. I'm sure there is... (since the angle of my arms would be the same as all the other stock arms guys out there).

??

[SCOTI]

Originally Posted by smoknbarrels

what causes the bumpsteer? the upper balljoints angles I thought???

Bumpsteer is caused when the arc of travel is different for the steering (steering-arm to outer tie-rod pivot) vs. the lower BJ C/L to lower a-arm pivot C/L.

If they're not on the same plain, they will be swing on different arcs as the suspension compresses/extends. The result is the steering wants to pull/push when the suspenion is cycling through its travel. You hit a 'bump' in the road, the suspension compresses, the steering & lower a-arm are @ different plains so they're fighting against each other which 'steers' the truck in the process.... ala 'bumpsteer'.

[abadsvt]

Originally Posted by smoknbarrels

I could set it up so that when deflated it will be 3/4" from the ground, that sounds like a good idea.

but as far as geometry, well its all stock other then drop spindles, so the angle of the upper ball joint is still quite sharp when sitting at my wanted ride height.

what causes the bumpsteer? the upper balljoints angles I thought?

I just figure that since there are a lot of guys out there that still use factory arms, that maybe there was a ride height magic number that bumpsteer starts happening at.. I'm sure there is... (since the angle of my arms would be the same as all the other stock arms guys out there).

??

VIN63 pretty much explained it but i will put it how i first learned it. As your spindle goes up and down through the suspension travel it forms an arc kind of like this ( . Your tie rod ends from your steering also have an arc similiar to the spindles arc. If one arc is a greater than the other as the suspension goes up and down the tie rod will either pull or push causing the front wheels to pull inwards or push outwards. This causes the steering wheel to "jolt" giving you a very unstable steering. In an ideal world the spindles arc will be exactly the same as the tie rods arc but it is extremely difficult to achieve that and so many things play a factor (upper or lower control arm mounting points, length of tie rod, height of tie rod and so on.) The reason why when you lower you truck you get bumpsteer is because the suspension is setup for a ceartan ride height. In the pic below imagine that the ride height is the center of arc (red line). As you go through your normal 4" or so of travel the arc are so close to the same that you don't notice the bumpsteer. As you lower your vehicle you are raising that center of arc line up. See how much different the arcs are higher they go. You really start to noctice the size difference which cause the steering to "jolt". Did that help explain why you get bumpsteer?

I am no expert just have learned stuff along my journey to learn everything.

Josh

[abadsvt]

Damn Scoti replied before i was done writing my book.

[SCOTI]

Originally Posted by abadsvt

Damn Scoti replied before i was done writing my book.

Yeah, but I didn't provide the PowerPoint presentation..... Nice job BTW.

[abadsvt]

Originally Posted by SCOTI

Yeah, but I didn't provide the PowerPoint presentation..... Nice job BTW.

Thanks scoti!

[bagged69chevy]

If Your suspension is set up properly... Bump steer will never be an issue, no matter how hi or low you are, or how much suspension travel you have... I fabricated my own front suspension, I have 14 inches of travel.. and less than 1/32" bump steer through the entire suspension arch.