why does a drop axle and mono's cause bump steer

58fridge100 i have that article and thats why i was wandering but thanks for all the info. also if i do a 4inch drop in back will it make the ride level since the back is higher or if i do the drop the back and do just the drop axle? what do you guys think
thanks for everything guys
-kujo

 

every situation every angle is different even on the same vehicles.
It is purely a problem of geometry, your own personal geometry on your vehicle not a question of materials or name brands or even the style of suspension your running. it is an engineering, setup and adjustment issue.

anything that causes the up and down of the suspension to push and pull on the steering causes bumpsteer.
bad gas, mismatched brand names, and religious affiliation will not cause it. No amount of superstition hear-say or "what he did on his car" will fix it on your car. you have to learn about suspension and steering geometry if your going to change anything.from stock and be happy with it(unless your lucky)

It cant turn the steering wheel in the bump because your hand is holding it still so it turns the tires instead.

 

As Tommy's drawing shows you need to keep the drag link parallel with the ground to keep the up and down arcs at a minimum and equal.

 

There was a thread some time ago about a dropped straight axle setup (think it involved "flipping" the axle over the springs) where the builder moved the steering box up about six or so inches to tame the bump steer. Might be in the tech archives?

 

also the greater the distance of up and down travel in your suspension is what
increases the amount of bump steer you will have if your geometry is
incorrect, if you had no movement then the angle of your drag link wont matter,
no sway bar can allow bump steer to occur, poor shocks can as well, so my point
is if you can't get the geometry to work out so as much bump steer is
eliminated as possible then keep the ride stiff and bump steer won't show up.

 

I have a 4 inch dropped axle with mono's and cross steering in my '46.. Absolutely no bump steer. Drag link is very close to parallel with tie rod. Also have reversed eye mono's on rear.