for a point of reference for future susp designs I was wanting to calculate the anti-squat with my leaf springs and trac bar. the formula's i've seen in the 4-link threads don't seem feasible to use for leaf springs. can anybody help me out ?

- jack

use the point where the traction arm connects to the frame. this is your Instant Center, heh.

do you mean panhard bar or traction bar?

trac bar, traction bar, whatever you want to call it. like the one Sam's offroad sells ...

- jack

You have to use the track bar as a link as well as a portion of the front half of the leaves as a link in the side view to figure it out. The arch of the spring matters!
I wish I had a link but MJ has a pic in his webshots.

can you elaborate more on how to calculate it triaged ?

- jack

Originally posted by morpheus
trac bar, traction bar, whatever you want to call it.
No, not "whatever" Jack. A traction bar is what you have. A Track Bar is another name for a panhard bar - it locates the axle laterally in 5-link suspensions, radius arm suspensions, and in (for some reason I'll never understand) YJ's.

Originally posted by TNToy

and in (for some reason I'll never understand) YJ's.

LMAO, true.:D

Here's the skinny. on a muscle car leaf spring rear the rule of thum is that the instant center is located on a line through the center of the axle parallel to the ground. and it is 2/5 of the total leaf spring length in front of the axle. This works OK with smallish tires and flat leaf springs but it isn't very close at all with typical lifted 4x4. When I was in colege I wrote a TK Solver program that calculated instant center location for leaf spring vehicles using the whole spring compliance. I don't really know how acurate that was either, but the first rule of thumb, that the instant center was always about the height of the axle center line seemed to hold true pretty well for the examples I tried.

Anyway with the sam's Offroad style traction bar where the traction bar is bolted solid to the axle housing and then mounted to a shackle the traction bar its self is not the link at all the shackle is the link. So if you draw a line through the upper and lower shackle bolts and a horizontal line through the axle center line where those lines intersect should be your instant center for your application.So if you draw a line through the upper and lower shackle bolts and a horizontal line through the axle center line where those lines intersect should be your instant center for your application.

Hope that helps

Originally posted by Gordon
Here's the skinny. on a muscle car leaf spring rear the rule of thum is that the instant center is located on a line through the center of the axle parallel to the ground. and it is 2/5 of the total leaf spring length in front of the axle. This works OK with smallish tires and flat leaf springs but it isn't very close at all with typical lifted 4x4. When I was in colege I wrote a TK Solver program that calculated instant center location for leaf spring vehicles using the whole spring compliance. I don't really know how acurate that was either, but the first rule of thumb, that the instant center was always about the height of the axle center line seemed to hold true pretty well for the examples I tried.

Anyway with the sam's Offroad style traction bar where the traction bar is bolted solid to the axle housing and then mounted to a shackle the traction bar its self is not the link at all the shackle is the link. So if you draw a line through the upper and lower shackle bolts and a horizontal line through the axle center line where those lines intersect should be your instant center for your application.So if you draw a line through the upper and lower shackle bolts and a horizontal line through the axle center line where those lines intersect should be your instant center for your application.

Hope that helps

That does not make sence, if the two bolts on the shackle are drawn through the center line of the axle, then the only place they converge is at the axle.
Can you word it a bit different, this is a cool one, i have thought about this before, kind of a way for us to make leaf spring stuff have a bit of a performance bonus even though it is not quite linked.

Ian-

http://community.webshots.com/photo/13190727/13201648cDNsWVGxwr

Everyone should bookmark mj's webshots.

interesting diagram triaged. though I'm not quite sure what to do with it :confused: .... especially since my axle is spring over. does that change things ?

- jack

Originally posted by Gordon
So if you draw a line through the upper and lower shackle bolts and a horizontal line through the axle center line where those lines intersect should be your instant center for your application.


thanks for the help Gordon. so, if the shackle is vertical then the line through the two bolts would be vertical and meet up at a right angle with the horizontal line that was drawn through the center line of the axle. right ?

- jack

Originally posted by morpheus


thanks for the help Gordon. so, if the shackle is vertical then the line through the two bolts would be vertical and meet up at a right angle with the horizontal line that was drawn through the center line of the axle. right ?

- jack

Yep

do morpheous' words make sense to you Krusty?

Got it, but are we still talking the shackle on the traction bar or on the leaf spring.

Ian-

on the traction bar.