Anti-squat question

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Old 09-20-2007, 10:57 AM
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Default Anti-squat question

I'm a little confused, to say the least, about how anti-squat works in off-road.

In on-road, anti-squat prevents the rear end from compressing under power. To get more rear traction under acceleration you REDUCE anti-squat and even move toward pro-squat.

Now in off-road, according to the set-up books for both my Losi MF2 and Xray XB8 buggy, to gain forward traction you INCREASE the anti-squat. Why is that, since isn't that preventing the weight from shifting to the rear? Also, why is there no pro-squat in off-road.

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Old 09-20-2007, 11:25 AM
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in offroad anti-squat also keeps the rear end of squatting under power, but in offroad anti-squat is more used to be able to handle bumps better, thats why you see most setups with 2-deg anti-squat....and because offroad isn't a smooth surface, more anti-squat means more bite.

as for in onroad the reason anti squat is removed to give more traction because the rear squats more, more weight is shifted giving more rear traction

this is all just from my experiences in the last year, i am by no means an expert, i have only been racing about about 15 months.
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Old 09-20-2007, 11:29 AM
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I've never really understood it much either but as a mechanical engineer I have a guess:

When you add anti-squat to the rear end of an electric offroad truck, basically what you're doing is tilting the whole rear axle and suspension assembly back, kinda like adding caster to the front. When you do that, any time you accelerate the tires not only pull the car forward but they pull the rear suspension down (extending) as well. Basically any time you give it gas the rear suspension tries to resist the inertia of the chassis pitching back (hence the term "anti-squat", the rear of the truck doesn't "squat down" as much under acceleration).

Adding anti-squat is an extra force that resists the weight of the chassis, planting the rear tires into the track. It's not so much about resisting weight transfer as it is getting the most out of the weight that comes to the back tires, instead of it being absorbed by the springs. If we used pro-squat, the force of the truck moving forward would try to compress the suspension and take pressure off the rear tires. The truck would wheel-hop.

Long story short adding rear anti-squat is a way to boost the spring's ability to push the tires into the dirt.
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Old 09-20-2007, 11:38 AM
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My xxx-4 buggy use's pro-squat.. But I am reluctant to use that setting, because of bumpy track surfaces..
Am I correct in thinking this way?
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Old 09-20-2007, 11:43 AM
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Originally Posted by Jake S View Post
but in offroad anti-squat is more used to be able to handle bumps better, thats why you see most setups with 2-deg anti-squat....and because offroad isn't a smooth surface, more anti-squat means more bite.
Hope you don't mind if I elaborate on this Jake

The guide may tell you that on a rough track you should reduce anti-squat, while if the track is smooth you should increase it. And in the T4 manual, that's all they say (thanks for the explanation guys )

If you were to put a lot of anti-squat in a truck on a rough track, every time one of the rear tires hit a bump the added force of the anti-squat would push the tire into the bump. The result would be a rough ride and the truck will get knocked off course as one tire finds traction before the other. Reducing anti-squat will let the shocks and springs take more control over the tire movement and allow it to absorb and roll over the bumps.

See, you onroad guys are spoiled, your tracks are glassy smooth. A "smooth" dirt track by offroad standards is still uneven, but the bumps are small enough that they won't knock the truck around. So you can put a little more anti-squat in to keep those tires on the ground and moving you forward, the track is smooth enough that there's nothing out there that will jolt the truck so much as to knock it off course.

If it helps, you can think of adding a degree or two of anti-squat as a very, very small increase in your rear spring rate, smaller than even altering shock positions.
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Old 09-20-2007, 02:28 PM
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Per Charlie Perez about 'antisquat' on a B4.

http://www.rc10b4.com/forum/showthread.php?t=32

=================================

"Zero degrees of antisquat "Frees Up" the rear end On Power and it also gives you a little more side bite. I like to start with the minimum amount of Antisquat because it gives the rear end the most balanced amount of traction as you enter and exit the corner. It also minimizes wheelies, which are cool to watch, but waste time. The only time that I increase the Antisquat is if I am on a smooth surface track that has limited traction. If I am on a ruff track I always run 0 as it makes it easier for the suspension to soak up the bumps and ruts.

The amount of Antisquat you use depends on the track conditions. If the track is very smooth, more antisquat will give you more forward traction. If the track is bumpy or rutty more antisquat will give you less forward traction"
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Old 09-20-2007, 07:32 PM
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Thanks everyone. You've been very helpful. Just so I'm clear:

I'm looking for more forward traction from my MF2 (side grip is great). I run on a technical and dusty, low-bite track, so lots of accelerating out of corners. Stock set-up is 2 degrees of antisquat, but if I understand correctly I should reduce it to 1 degree or even 0 degrees?
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Old 09-20-2007, 08:25 PM
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So would pro-squat be better for rough track situations?
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Old 09-20-2007, 08:41 PM
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Originally Posted by Alltapdout View Post
So would pro-squat be better for rough track situations?
No it would not. Basically for the same reasons that more ANTI squat is not good on rough tracks.
PRO squat is not good in any situation. Possible exceptions may be in multi link or canti lever suspension systems.
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Old 09-21-2007, 07:01 AM
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It was mentioned above, and it should say the same in your losi manual, more antisquat makes the car pop up higher on jumps while less gives you a flatter, lower arc.

Simply stated, antisquat (and prosquat for that matter) puts the suspension in a bind, slowing down it's reaction from power input and feedback from the track surface. The more squat the more pronounced this bind becomes and is always so on power. This is why more squat will make a car bounce more on a rough track. It's this effect which causes the pop up effect on jumps. The suspension is pulled down by G force as the car makes the transition up the jump face then suddenly unloads when you get off the throttle as the car reaches the top of the jump ramp. Less squat allows the suspension to begin unloading sooner so you get less of a pogo stick effect at the lip of the jump.

Running CVD's on a 2wd off road car will give you much the same effect as they bind under acceleration and loosen up off power.
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Old 09-21-2007, 08:15 AM
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Default that ain't squat

Actually my Losi manual did not mention anything about the vehicle being launched differently off jumps. It says that changing from -3 degrees of anti squat to -1, or 1 degree of pro squat adds traction to the rear end going into turns and a decrease in traction out of the turn.
So I thank you all on your interpretations, so just to re-ask the same thing again
Would the best position be with the rear arms setting as level and possible for a rough low bite track?
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Old 09-21-2007, 09:22 AM
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Originally Posted by Alltapdout View Post
Actually my Losi manual did not mention anything about the vehicle being launched differently off jumps. It says that changing from -3 degrees of anti squat to -1, or 1 degree of pro squat adds traction to the rear end going into turns and a decrease in traction out of the turn.
So I thank you all on your interpretations, so just to re-ask the same thing again
Would the best position be with the rear arms setting as level and possible for a rough low bite track?

I've got to say I agree with Alltapdout. My Losi manual says more anti-squat=more rear traction on-power. The Xray buggy set-up book says the same thing. I can't understand why anti-squat would EVER give you more rear traction - whether it's a smooth track or a bumpy one - because it's letting LESS weight transfer backwards. Am I wrong?
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Old 09-21-2007, 09:44 AM
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Think of it this way:

When you try to make the tires "hook up", it's by forcing the tires towards the ground. Since Mr. Newton says that every force has an equal and opposite force...if you force the tires down, there must be an opposite force...enter "anti-squat".

Essentially, if you have "squat", the chassis and the tires are both moving towards the track. With anti-squat, you want the tires and chassis to move in opposite directions. Essentially, the tires are forced towards the ground and are opposed by the chassis. What you're looking for is separation.

The wagon has a 4-link setup and you use the same terms and the physics are all the same. If you want to hook up, you want the tires to go down and the body to go down (relatively) less.
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Old 09-21-2007, 09:55 AM
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Originally Posted by Turbo Joe View Post
Think of it this way:

When you try to make the tires "hook up", it's by forcing the tires towards the ground. Since Mr. Newton says that every force has an equal and opposite force...if you force the tires down, there must be an opposite force...enter "anti-squat".

Essentially, if you have "squat", the chassis and the tires are both moving towards the track. With anti-squat, you want the tires and chassis to move in opposite directions. Essentially, the tires are forced towards the ground and are opposed by the chassis. What you're looking for is separation.

The wagon has a 4-link setup and you use the same terms and the physics are all the same. If you want to hook up, you want the tires to go down and the body to go down (relatively) less.
Well said. Because anti-squat tips the lower rear suspension assembly back, the control arms not only travel down but slightly forward. Because the tires are attached to the ends of the arms and not directly to the chassis, under acceleration the forward pull of the tires resists the compressing action of the rear of the chassis, forcing the tires into the ground.

I'm at work right now, when I get a break I'll jump on the CAD software and sketch up a quick diagram comparing 0 of anti-squat to a rear end using anti-squat.

I know, I suck at explaining things like this through speech, and I'm even worse when it comes to typing an explanation for someone. I've been trying to teach one of the guys I race with how a swaybar works for about the past 2 years now.
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Old 09-21-2007, 10:45 AM
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Originally Posted by Turbo Joe View Post
Essentially, if you have "squat", the chassis and the tires are both moving towards the track. With anti-squat, you want the tires and chassis to move in opposite directions. Essentially, the tires are forced towards the ground and are opposed by the chassis. What you're looking for is separation.
Great explanation. I think I'm finally understanding how it works - and seeing that there's more to anti-squat than simply weight transfer.
But two more questions: 1) On a bumpy track with low grip, to get more forward traction under acceleration is it more or less anti-squat (I've seen both arguments in this thread) and 2) does anti-squat work different in on-road, as all the on-road set-ups I've seen (including the XXX Main, which is a great source of info) say LESS anti-squat equals MORE rear grip on-power.
Thanks again.
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