Anti-Squat?

BUCKETOBOLTS

BUCKETOBOLTS

Member
Joined
May 4, 2005
Location
Faith, NC
I'm trying to layout a plan to a 4 link suspension. I followed the advice from the Peterson's article for laying out the bars. I then plugged those #'s into the calculator from the Pirate board. I'm getting a 20.9% anti squat. Too high, low? What should I be shooting for?
 
20% sounds a little low IMO. The roll center and how the AS behaves through the travel is just as important when you're working in that calc, IMO.
 
Rich said:
how the AS behaves through the travel is just as important
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:lol:

You mean things like whether it gets drunk and unruly, then hits you up for $20?
 
So I should try to get 40-50% or does it need to be higher? My rig now sits at 92" wb with leafs in the rear. I built a traction bar to stop the axle wrap. I think I have to much anti squat with that set up. It feel like it picks the whole truck up when you stomp it. I believe it unloads the front axle on hard hill climbs. The traction bar is only 42", the lower links I use in the calc are 48" with a 33.5" upper. And they are triangulated. How do you read how much steer you get during articulation from the calc?
 
roll axis is how much steering you get...

You're absolutely right about the traction bar, they can induce a shit-ton of anti-squat.

Honestly, I'm not a pro at this, I just have countless hours of reading, research, and a little practical application on it..

But if you want to use the calc, you really need a good understanding of everything involved, and I'm not the guy to be able to teach ya...

A *verrrry* general rule of thumb, and this is by NO means definitive - 50-80% AS, as close to 0 on the roll axis, as high a roll center as you can get (the closer to your CoG the better, but it'll not get that close), make sure the AS stays consistent through the travel, and, oh.. the most important part.. make sure it'll all fit on your rig.. ;)

Also, look at some rigs that you see that work well, and note their setups..
 
oh.. the most important part.. make sure it'll all fit on your rig..
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Thats the fun part. I can take my starting figures and move the upper link up and down 1" and move the A-S from 2*-49*. I think I can adjust the mounts enough to get were I can adjust from somewhere about 20-70*. Shoot if had Rich's money, I'd throw a set or Rockwells under there while at it:huggy: .
 
In the "travel" tab, you can see how the anti-squat (and other parameters) will change as the suspension cycles through stuff & droop.

You could shoot for say 75% AS, but if the AS rises to 125% when the axle is 3" drooped, well... shit ain't gonna work too well.

Obviously you can't model for everything since we don't 'wheel on flat land, but it can get you to a decent baseline - I think one of the good fab guys said it best- "It's a tool, but it's not the be-all-end-all"

(That said, I've seen rigs that should have crappy "numbers", but worked well enough..)
 
Rich said:
In the "travel" tab, you can see how the anti-squat (and other parameters) will change as the suspension cycles through stuff & droop.
Click to expand...

That's because that little calculator is nothing more than that -- a little calculator. It's handy and all, but it's no substitute for a little bit of common sense. At least you understand that AS is never going to stay the same. As a general rule of thumb, it's going to increase as the axle droops and decrease as it stuffs. It's just simple vector geometry.

Like Rich stated earlier, pay attention to the slope of the roll axis, the height of the roll center, and go with what fits... you're going to have to make compromises when it comes time to fit everything under the truck.
 
roll center

Roll center is really torque steer or skateboard-truck-affect right? When it articulates, it steers to one side? This is neglecting the use of some kind of sway bar.
 
You could shoot for say 75% AS, but if the AS rises to 125% when the axle is 3" drooped, well... shit ain't gonna work too well.
Click to expand...

Basically as the axle droops it is wanting to drive under the vehicle and push the suspension further down.

Roll center is really torque steer or skateboard-truck-affect right? When it articulates, it steers to one side?
Click to expand...

From what I understand, yes. It can cause the rear to shoot out from under the rig when your articulating and looking for traction.
 
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