New guy confused by suspension terms

[rusty63ss]

I am all new to changing suspension and do not understand what some of the terms mean. I understand some of this stuff like instant center, roll center. But some for instance;

Bump
Bump scrub

What does this mean and why is it important?

Thanks for educating the new guy.

Dhamen

[jay72nova]

The common use of bump is simply when you suspension is "absorbing in its travel" like when A arms go up to absorb a possom in the road. I don't know what bump scrub is. I could guess but I won't

[rusty63ss]

Originally Posted by jay72nova

like when A arms go up to absorb a possom in the road.

I hope to never collect one with my Nova but that is funny.

Thanks for the reply and helping me understand another term. I am sure there will be more.

[jay72nova]

Originally Posted by rusty63ss

I hope to never collect one with my Nova but that is funny.

Thanks for the reply and helping me understand another term. I am sure there will be more.

yeah...it happens..

just to take a guess on bump scrub ..would it be your scrub line at full bump?

so whatever parts on the headers engine chassis hangs down lowest creates your scrub line and whatever that would be at full bump could be your bump scrub?...just thinking outloud here....

[pragmatist]

Bump scrub is another name for bump steer. No, we are not talking cows here. If your suspension is not fully maxed out one of the problems you may encounter is bump steer. When a wheel goes though it's travel if the inner and outer tie rods for the steering are not placed in the proper location the wheel will actually change direction as it goes through the bump. This is a most unsettling feeling and restricts your best efforts of achieving a fast ride. Usually only a few washers either raising or lowering the outer tie rod will correct the problem.

[jay72nova]

Originally Posted by pragmatist

Bump scrub is another name for bump steer. No, we are not talking cows here. If your suspension is not fully maxed out one of the problems you may encounter is bump steer. When a wheel goes though it's travel if the inner and outer tie rods for the steering are not placed in the proper location the wheel will actually change direction as it goes through the bump. This is a most unsettling feeling and restricts your best efforts of achieving a fast ride. Usually only a few washers either raising or lowering the outer tie rod will correct the problem.

ahhh...weird name for it

[rusty63ss]

Thanks for all the replies guys. I'm learning. And that is why I'm here.

Thanks again.

[jay72nova]

Originally Posted by rusty63ss

Thanks for all the replies guys. I'm learning. And that is why I'm here.

Thanks again.

I'm in the process of learning all this myself and have read a whole buch of books on this stuff, there are a couple of sources of information I really learned alot from and have been using to st up my Nova
david Pozzis website.
the book "How to make Your Musclecar Handle"
"The Unfair Advantage" ...Donahues accounts of his race cars and racing experienes...alot of "set up process" narrative
There is another book by Valkenburg (coauthor of the unfair advantage)called something like "race car dynamics" (I have to go find it to make sure)it was really good as well
"competition car suspension, a practical handbook" was good also...way too much math! but it had a very in depth and informative discussion on Ackerman and its effects on handling that I have not found anywhere else.

[funcars]

One more book appropriate to old muscle cars - Steve Smith "Advanced race car suspension development". Inexpensive but very useful and practical.

[ccm399]

Bump scrub would actually be the amount of lateral movement the tire makes (track width change) as the suspension is cycled. The change might be wider or narrower (or possibly even both through the full cycle) it doesn't matter.

The basic description of bump steer given earlier is correct.

Hope this helps.

Chris