Anti Squat and Suspension Tech

[Cole82]

What is everyones opinion on anti squat? Do you want the whole truck to sink down on climbs? Do you want the front to sink and the rear to raise up?

What ya thinking?

[JohnRobHolmes]

I do my best to keep it nuetral. I dont like my rear extending on a climb, or sagging under the chassis. My first build had bad anti-squat and it would tip backwards easily.

[RodyRazorBackc5]

I would say it really depends on the degree of the incline , Or decline for this matter.

[Jneves]

I go for neutral as well... my first tube build has messed up link geometry in the front and picks up the left front too easily which keeps the suspension from working properly. I got lucky on the rear end and nailed it on the first try no noticable squat/rise and no torque twist. I think you need some amount of antisquat in the rear to prevent torque twist without having to resort to miss matched springs/preload from side to side.

[EeePee]

Ever since I've been using a TLT I've played with squat numbers. My newest attempt at the perfect suspension has a little anti squat in the back, and hopefully even more in the front. I'm trying to force my tires into the ground. And in the front I figured it'll suck the front tires down on climbs. It visibly works.

My next change will put a little more anti-squat in the rear to aid in pushing the front down. You can easily go to far with anti-squat in the back, and create a wheel hoping reject. Conversely, you can also go to far and create a back flipping turd. So make small changes at a time.

I've found I usually need to play with spring preload, or change the spring rate when I make squat changes. The torque twist can become excessive if you go far with squat.

In this picture, you can see spacers under the top link mount. It's how I added front squat. The front torque twists more than the rear does with this little change. Before, there was no noticable twist in the front.

And that's what I got about squat!

[EeePee]

And I just noticed it's pulling my upper link mount away from the plastic ears...

Interesting... maybe.

Or I could be wrong...

[Cole82]

EeePee that was what I was looking for. Some trial and error awnsers. It does look to be seperating the plate from the axle.

I'm trying a real goof ball setup at the moment. The rear jacks WAY up in the air and the front sinks down untill it hits the servo. It seems to work ok on the climbs, but on boulder fields it pretty much eliminates the rear suspension under power.

[Reflection]

Eee Pee,can you post a picture of your rig from the side....to see the link plains and verticle seperation? Just for comparison. I always build in adjustments for verticle seperation at the chassis. I believe mine,right now,has a touch of squat in the rear and quite a bit of squat in the front. My new chassis/link set up does ALOT better than my last.....but theres always room for improvements

I put,or tried to put a touch of squat to help with wheel hop. I've not noticed much,if any wheel hop with my current set up.

[EeePee]

I'm all about breaking parts, and trial and error!

Show us some pictures Cole, I'd like to see how goofy it is.

[Brainstain]

So, anti-squat is basically just the relation of the links' angle to each other right? So, changing link separation at either the axle or the frame would change anti-squat..Right?

[EeePee]

Originally Posted by raptorman57

Eee Pee,can you post a picture of your rig from the side....to see the link plains and verticle seperation?

You know I picture whore, so of course I can.

But you can't see how the rear is set up. Sorry. But it's close to how the front looks. Maybe!

Front is on the left.

Both front and rear links converge to a point, eventually, neither are parallel. Both are mild geometry numbers, as going to extremes seems to have a more negative effect than good. And Pinchflat did a good job of making this truck pretty nuetral from the beginning.

Spring rates have a pretty big impact on letting all of this squat geometry stuff do it's thing. As do shock angles. Too much of a falling rate and things get worse as the suspension goes through it's travel.

I love suspension.

[Reflection]

Originally Posted by rambuller84

So, anti-squat is basically just the relation of the links' angle to each other right? So, changing link separation at either the axle or the frame would change anti-squat..Right?

Correct. You gotta remember though,when setting the front up,everythings reversed,so you gotta figure it backwards

[Brainstain]

The way I was doing my new tuber was, the top links are gonna lay flat and the lower links would be on a decline from the chassis to the axles. So, that would work on the back, but the front would need to be the opposite? I have another TLT that apparently has too much separation at the front axle and that would be the reason it won't articulate worth a crap.

[EeePee]

Rambuller, the overall effect would be dependant on your ride height, and where the two links converge and make a point in relation to your center of gravity.

[Brainstain]

Ok. I think my tuber needs to come back apart for more link mounts and I'll just go from one extreme to the other and see what does what. Trial and error with a little bit of knowledge. Thanks Eeepee.

[joesbruiser]

There is nothing harder to do than make a 1000+horse power stock suspension class drag car hook on a small tire like a 295 drag radial.But to do it you have to play a lot with the instant center and anti-squat and with some time you can move a 3200 pound tire on a dot legal tire down in the 1.20-1.30 60ft range .
The same principles work for any 4-link design .Now to get to the point here is a very good article on 4 link set ups it is on the sight of the guy who helps me setup my mustang it may be usefull.Here is the part explaining anti-squat and the link so you can see the rest of stuff that has to do with 4-link.Ihttp://www.baselinesuspensions.com/info/Launching_A_Drag_Car.htm If a car squats in the rear it is not actually putting more weight on the tires it is actually lifting the tires away from the ground.When you do have some anti-squat and the chassis seperates from the tires it is putting more pressure to the ground.
Definitions:
Anti Squat (AS):
This is a term used to describe how much the rear of the car will Rise or Squat during launch. If a chassis has 160% of AS then the rear will rise drastically, planting the tires violently. By comparison if a chassis has 100% AS then the rear of the car will not rise or squat and if a chassis has less than 100% the rear of the car will squat.
~A common problem with high horsepower cars running Too Much AS is that the tires will plant the tires very hard for the first several feet but then start to unload the tires and spin when the chassis starts to settle. If your car does this, then look into the value of the AS. Much too often racers will detune the engine to "calm down" the launch instead of look into the suspension geometry.
~A common problem with high horsepower cars running Too Little AS is that the suspension will cause the rear of the car to squat which tries to unload the tires. Again racers detune the engine to maintain traction instead of looking into the suspension geometry.
Normal/Neutral Line:1. Draw a line up through the center of your front wheel.
2. Draw a Horizontal line through the CG until it crosses the line drawn through your front wheel and mark this intersection point. The Normal Line (or Neutral Line) is the line drawn from the Rear Tire contact patch through this intersection. Neutral Line

The location of the IC relative to the CG and the Normal Line (or Neutral line) is what determines what the chassis is going to do. One term used to describe the chassis movement for a 4 link suspension is Anti Squat. An IC that is located ABOVE the Normal Line is said to have more than 100% Anti-Squat. An IC located BELOW the Normal Line is said to have less than 100% Anti Squat.

~4-link settings of 100% Anti Squat should accelerate the car w/o any raising or squatting of the rear of the car.
~4-link settings with MORE than 100% Anti Squat will Raise the rear end and hit the tires HARDER.
~4-link settings with LESS than 100% Anti Squat will cause the rear end to Squat and hit the tires SOFTER.

~IC's that are located IN FRONT of the Center of Gravity (CG) will tend to lift the NOSE of the car.
~IC's that are located BEHIND the Center of Gravity (CG) will tend to lift the REAR of the car.

[EeePee]

C'mon Cole, let's see it!

[Cole82]

Ok EeePee is that the rear axle or the front axle you added the spacers to?
It took so long because I retested everything after EeePee posted that Pic. I was thinking that was the front axle. If it is the front axle then my testing goes against what you posted.
Here it goes the front links go away from each other. They would intersect infront of the axle not on the chassis side. The rear is the exact opposite. They intersect right infront of where they mount on the chassis.
My testing is all done by EYE and could be completely wrong. I undestand the rear just fine as far as where to put links for AS, RS, IC etc.. They front I'm still learning.
When I have the links in the front setup like the rear the front jacks up in the air.
When I mount them farther apart on the chassis and under the front servo mount. The front then sinks down.
To measure this I put a piece of tape from the chassis to the front axle. If the tape went limp it was easier to see if it squated. If it went tight it lifted.

[JohnRobHolmes]

Im really digging this thread. It is so hard to get proper adjustments on such a small scale. The way you are shimming the links is ingenious.

[Cole82]

Originally Posted by johnrobholmes

Im really digging this thread. It is so hard to get proper adjustments on such a small scale. The way you are shimming the links is ingenious.

I did it with carbon.