Trying to Learn squat....

[Grant 302]

The one thing that has me a little worried is the current UCA angle of 15 degrees seems a bit steep, looks like a little wench gymnastic will be required to make it longer...

The easiest way to adjust that angle would be to raise the rear ride height. Then move the rear LCA connection up by the same amount or the next higher hole.

 

[Mad Hatter]

I got out of work early today so went under the car to relax..... It was plain to see that the BMR brackets highest setting is about a inch and a half lower then the original setting.... So I changed to the top point and left the LCA's at 1.4 degrees up toward the front. Was going to wait to test, but got itchy fingers.

I can raise the rear a bit more to get it to two degrees. The UCA angle seems a little extreme though... Whats a tipical angle you see in a stock position??

I liked those spring rubbers! But I think I will go from 600/350 to 500/300.

Forgot, but can you update the Koni 30 single ajustable shocks to JRI's??

 

[Mad Hatter]

ahh, just worked it out that as I raise the rear my UCA angle will also go down.

 

[Fabman]

Something to think about, as you steepen the angle of the upper arm you gain anti squat.
What you gain on acceleration you lose on deceleration and the anti squat is now working backwards against you. So, don't get carried away. A couple 3 degrees up on the lower arms (must be set with the driver weight in the car and appropriate fuel load) and a long instant center by using a gentle angle on the upper. I quickly dumped the 3rd link for a torque arm so I don't have a number for you, but don't get carried away with it.

 

[Grant 302]

ahh, just worked it out that as I raise the rear my UCA angle will also go down.

Always nice when the light comes on!

Forgot, but can you update the Koni 30 single ajustable shocks to JRI's??

Yes, but that's replacing the whole shock eyelet to eyelet and re-use the rest of the hardware. For the struts, the housing is also re-used and the threaded insert is changed out. I'm sure a call to CorteX would explain it better.

I got out of work early today so went under the car to relax..... It was plain to see that the BMR brackets highest setting is about a inch and a half lower then the original setting.... So I changed to the top point and left the LCA's at 1.4 degrees up toward the front. Was going to wait to test, but got itchy fingers.

I can raise the rear a bit more to get it to two degrees. The UCA angle seems a little extreme though... Whats a tipical angle you see in a stock position??

Or go to the stock hole for the LCAs and raise the car more...you want it to squat, right? I'd forget about anything near 3º up to make that work.

 

[Fabman]

Always nice when the light comes on!



Yes, but that's replacing the whole shock eyelet to eyelet and re-use the rest of the hardware. For the struts, the housing is also re-used and the threaded insert is changed out. I'm sure a call to CorteX would explain it better.



Or go to the stock hole for the LCAs and raise the car more...you want it to squat, right? I'd forget about anything near 3º up to make that work.

so, induce a bunch of roll under steer?
Upon acceleration it would suck the rear end up into the body and give it anti traction....is that what you're suggesting?

 

[Fabman]

I mean, yeah that would make it squat, but that's not the same as transferring weight to the point of over coming the spring rate, which is what would give you traction.
The anti squat pushing against the weight of the car as it transfers diagonally....its that force back that makes traction.....just sucking the wheel into the wheel well doesn't do that, quite the opposite. It takes weight off the rear wheel and the car flops down because there IS no resistance. You still want antisquat, just less of it. Like 50% or less. That allows the car to transfer weight and still resist it.
Am I missing something here?

 

[Grant 302]

so, induce a bunch of roll under steer?
Upon acceleration it would suck the rear end up into the body and give it anti traction....is that what you're suggesting?

lol. "anti-traction".

Yes, and roll understeer is part of the solution. I wouldn't say a bunch.

And yes, the outside rear will tuck into the well. But 'suck' into, no.

Draw the free-body diagram...

 

[Fabman]

lol. "anti-traction".

Yes, and roll understeer is part of the solution. I wouldn't say a bunch.

And yes, the outside rear will tuck into the well. But 'suck' into, no.

Draw the free-body diagram...

I'm clear on how it works, less than zero antisquat has the opposite affect of anti squat. It will mechanically lift the tire just the way anti squat lifts the body and pushes down the tire.

 

[Fabman]

The key here is less than 50% antisquat. Not the total absence of it.

 

[Fabman]

The car will still squat with 50% anti squat.
Less than zero antisquat is how you get wheel hop.
That's the force lifting the wheel and then dropping it back down when it loses traction and cycling over and over.

 

[Fabman]

Thats why I said gentile angles. Still lowers up and upper down, but gentile angles.
A long instant center will react more slowly and is more gentile on the tires so it doesn't tend to shock the tires loose. A short instant center is more violent and tends to bite initially and then spin. I'm sure you know this from drag racing.

 

[Grant 302]

Am I missing something here?

I think to start, a couple of things. First, the car is already rolling. Second, the car is already turning.

But even in the static/drag scenario, you have most of it correct. But the action of squatting the rear nets compression of the rear spring resulting in more traction. A car with 100% anti-squat neither lifts or compresses the rear and the spring load is the same as resting. But go up say 110% anti squat and you get the ability to 'shock' the tire more, but that quickly unloads as you lift the body and unload/decompress the spring. Net, you get less traction rolling out. Conversely, a squatting drag car can't take as much of a 'hit' or shock, wastes some energy and takes a bit longer to get going. Technically speaking, the real term is 'jerk' or rate of change of acceleration. Anti-squat allows higher jerk or ramp up to max acceleration and squat lets you eventually accelerate more but you gotta get there a bit slower since it take time to load the suspension up.

Setting up Mad Hatter's car to squat is the whole point of this thread.

 

[Fabman]

I think to start, a couple of things. First, the car is already rolling. Second, the car is already turning.

But even in the static/drag scenario, you have most of it correct. But the action of squatting the rear nets compression of the rear spring resulting in more traction. A car with 100% anti-squat neither lifts or compresses the rear and the spring load is the same as resting. But go up say 110% anti squat and you get the ability to 'shock' the tire more, but that quickly unloads as you lift the body and unload/decompress the spring. Net, you get less traction rolling out. Conversely, a squatting drag car can't take as much of a 'hit' or shock, wastes some energy and takes a bit longer to get going. Technically speaking, the real term is 'jerk' or rate of change of acceleration. Anti-squat allows higher jerk or ramp up to max acceleration and squat lets you eventually accelerate more but you gotta get there a bit slower since it take time to load the suspension up.

Setting up Mad Hatter's car to squat is the whole point of this thread.

My point is there is more than one way to induce squat and one way is definitely better than the other.


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[Fabman]

Think of it this way, if you put a come along between the axel and frame and jacked the body down over the tire it would certainly squat, but that would give it anti traction. Now put a leaver between the axel and frame and lift the body, now add enough weight transfer to over come that leverage and you get squat....AND traction. That’s how it works.


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[Grant 302]

The car will still squat with 50% anti squat.

Agreed. It'll squat at 99.9% anti-squat. That's part of the definition.

Less than zero antisquat is how you get wheel hop.
That's the force lifting the wheel and then dropping it back down when it loses traction and cycling over and over.

I'm not talking about going that low. IC below the ground? No. Not even close to what I'm suggesting.

I think this is where you're misunderstanding me and what I'm suggesting and the rest of the geometry. The LCAs can be pointing down and still have anti-squat. Draw it out and you'll see. Even pointing DOWN 3º you could get values over 100% anti-squat.

 

[Grant 302]

Oh I understand perfectly, I’m just not very successful in getting my point across, but what I’m trying to tell you is 100% accurate, you can take it to the bank. I’m just running out of ways to explain it.

Exactly the way I feel.

 

[Fabman]

Exactly the way I feel.

Let’s boil it down to this:
If I took a come along and jacked the rear end housing up into the body would that tire have more traction....or less traction?


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[Grant 302]

Here, look at it this way....take the right rear spring out of the car. Will it squat? Of course it will. But there is nothing to resist that squat ergo no traction. That’s what you are doing with bad geometry. Negating the spring resisting the weight transfer.

No, that's not what would happen. The frame would rest on the axle, and there would be traction.

 

[Grant 302]

Let’s boil it down to this:
If I took a come along and jacked the rear end housing up into the body would that tire have more traction....or less traction?

Terrible example. All and any traction would be in the jack wheels. You can't just add or delete stuff from the model.