huge anti-dive

[faeez]

Just wondering, what will happen if you have a huge anti-dive say 20%?

[Yellow Ranger]

breakage???

Will your a-arms support it?

[faeez]

really? hmm, is there a way to prevent this? say using stronger material, or make it thicker, would that help?

[Anvit Garg]

20%? Doesnt that mean 80% of the load transfer is reacted by the springs and the suspension will thus deflect proportional to the wheel rate?

So I guess you could then look into stiffer springs or modification of your bell crank to change your wheel rate. Or do other things to change the wheel rate (psi, changing wheels, etc)

[faeez]

thanks anvit, im still confuse on how it relates to wheel rate?

[Anvit Garg]

The wheel rate is computed based off the spring rate of your tires, the motion ratio of your bell crank, and the springs connected to the dampers. (Also the sprung and un-sprung weights)

So I guess this does not directly relate to your anti dive dilemma but I am sure it will be affected by your solution to the 20%

[exFSAE]

Better question:

Why are you running (or considering running) 20% anti-whatever?

[Yellow Ranger]

you know... you could try and tune your car without binding the suspension links...

if its a question of helping the driver feel what the car's doing while braking, then I can see the desire for a little antisquat/dive...

[faeez]

isnt anti-dive is suppose to be good in reducing pitching during braking?

[Yellow Ranger]

I'm pretty sure by helping the car 'stand up' more under braking and increasing weight transfer. We did some testing last year with our 08 vehicle which was initially designed to run no geo pitch center (arms parallel) but made adjustable inserts to give the car a pitch center at .5" and 1" above ground at CG - which meant having antidive and antisquat. We found that the driver could 'feel' the car pitching more under braking with the .5" PC and more so with the 1" PC. Plots from DAQ showed that although there wasn't necessarily more pitch (according to the linear potentiometers) but that pitching did occur much quicker.

I was wondering if anyone else had done any testing like this? We're wanting to do it again this year, just to make sure we had all of our calibrations set up right, and our driver wasn't too hung over from the night before...

[faeez]

so did u manage to figure out where the pitching came from? i mean if from geometry there is not meant to be pitching, where did it came from?

[RacingManiac]

We've had a car that had ~20% anti-dive on the front, and we've had our issues with a-arms that we ended up making beefier a-arms to deal with it.....it was more of a design trial that year and we ended up reducing it significantly on the next car....

[Yellow Ranger]

When the car is braking or accelerating, it will pitch to some degree, and probably heave to another, depending on the location of your pitch center/axis. My thinking is that if you look at side view kinematics like front view stuff, than when you have aarms that are parallel, although your instant center is an infinite distance away, it doesn't mean your car wont roll - the roll center would effectively become the outside tire (the point at which the car would roll over if laterally loaded), but if the vehicle rolls about an axis in the center of the vehicle, the driver is going to feel more of a roll sensation.

I think something along these lines happens in side view kinematics and pitch centers. If there was no pitch center, the car is still going to pitch about a point, it will probably just be about the tire contact patch, and feel less noticeable.

I've been trying to find the data where you could see the motion of the shocks but not having to much luck. Let me know if anyone else has experienced something like this or has a different explanation.

[Anvit Garg]

What is the correct way of calculating the amount of anti-dive?

Is it the SVSA height over the length (from tire patch to IC)? Or the angle of the CG from the tire patch compared to the angle between the IC (side view) from the tire patch?

I was trying to design for anti dive, but realized that since our CG is estimated, that maybe I should just leave the arms parallel. And maybe make them adjustable...

I am just worried by having adjustable arms (along the z axis) might affect your caster behavior. If I maintainted the correct Y length of my upper and lower A arms while traversing them along the Z to adjust for anti's, would this be sufficient in keeping all of my other designed variables safe?

[flavorPacket]

Probably not. You'd need to calculate it though.

A typical adjustable racing suspension has sufficient adjustability to allow the race engineer to change one variable at a time. For example, he may add anti by changing the z position of the upper and lower inboard points. But to keep this change from being confounded by other changes (caster, camber coefficient, etc), the rest of the points will also move to keep the other properties the same as before the change.

Designing a proper system of adjustment is a lot more work than simply moving the inboard points up or down. That being said, just doing that will likely teach you a lot about your car and make you faster.

[Steve O]

In response to anti-dive being good. You have to be very careful with anti-dive/squat as it causes problems with excessing or uncontrollable jacking which is hard to reverse if your suspension geometry is set. Typically formula (real F1 cars) didn't run any anti dive and maybe very minimal anti-squat until more modern hydraulic computer controlled suspension systems were invented to create anti's and compensate for the effects on jacking forces. With the short wheelbases we run and the relative short wheelbases of their cars relative to their track width, it will get you into trouble fast. Typically the purpose of extreme amounts (more than a couple %) of anti-dive/squat is for a smoother ride in luxury cars, not for performance handling.

As far as calculating / controlling anti-dive or squat, think of it as an ARB but for the side view (squat view). What you are effectively doing is binding the independence of the suspension from the tire force vector's relation to the vehicle's CG. As mentioned above in another post by adjusting the A-arm's parallel relation to the other A-arm (in other words adjusting the rake) you will adjust anti-dive or squat depending of course on what set of arms you are adjusting. Basically the component you are modifying is the position of the IC. The simplest way to explain how to calculate this would be a fairly simple geometric model of connect the dots. A line drawn from your instant center to your contact patch would make up your tire force vector component. Now find your CG. Now here is the magic you were waiting for... this tire force vector crosses a vertical line drawn through the CG hopefully somewhere between the CG and the ground and creates a lever. As the braking occurs, force is transmitted to this lever backward through the tire force vector and forward from the CG. As you could imagine as the tire force vector moves up and approaches the CG the car would have less tendency to roll forward or 'dive';therefore, the tire force vector intersection point at the ground is 0% and at the CG is 100%. The interesting thing about this is if you were to move your IC very high your car could actually have a squatting characteristic during braking! This is of course similar to moving your roll center (in plan view) above your CG which causes your car to pitch into a corner instead of out of the corner.

Well hopefully that made sense and was somewhat helpful!

[faeez]

Originally posted by RacingManiac:
We've had a car that had ~20% anti-dive on the front, and we've had our issues with a-arms that we ended up making beefier a-arms to deal with it.....it was more of a design trial that year and we ended up reducing it significantly on the next car....


racingmaniac, just wondering, how did the car go with anti-dive 20~ in terms of performance? besides the beefier suspension wishbone, what other siginificant impact did u realize from the anti-dive?

[C.Zinke]

Originally posted by faeez:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by RacingManiac:
We've had a car that had ~20% anti-dive on the front, and we've had our issues with a-arms that we ended up making beefier a-arms to deal with it.....it was more of a design trial that year and we ended up reducing it significantly on the next car....

racingmaniac, just wondering, how did the car go with anti-dive 20~ in terms of performance? besides the beefier suspension wishbone, what other siginificant impact did u realize from the anti-dive? </div></BLOCKQUOTE>

Since 2007 we are running about 100% anti-dive and 100% anti-squat in our cars. 2008 we were able to adjust it between 100-130% at the front axle. In my opinion it is not possible to design anti-features in 2D. You always have to think in three dimensions. If you just use the sideview of the car's suspension you will get huge errors into your design. Addionally there are some sideeffects, like the force in the toe-links that influence your anti-dive or anti-squat.

From my experience huge anti-dive or anti-squat can gain a lot of performance. But you have to be able to desing it correctly. Furthermore huge Anti-Dive will have big effects on the distribution of the roll-moment in your car with different steering angles. In general: If you have huge anti-dive then you will have more understeer with higher steering angles. If you do not like this effect (in my opinion it is usefull) then you can adjust your steering geometry to compensate for that.

[scott_rfr]

C. Zinke, I am a little confused on how large amounts say 100% antidive is going to affect your roll moment distribution and induce understeer. Care to explain a little more?

Scott

[C.Zinke]

Say you have a steering angle of 30deg at your outside tire. (I know this is a lot, just for the example now). Then you can split your side force of the contact patch into a longitudinal and a lateral comonent. You will see that the longitudinal component (50% of your total tire side force) is acting on your suspension similar to a braking force. This stiffs up your supsension. This was a very short explaination. I hope it becomes clear.

[scott_rfr]

Thanks, I see it now.

Scott

[faeez]

In general: If you have huge anti-dive then you will have more understeer with higher steering angles. If you do not like this effect (in my opinion it is usefull) then you can adjust your steering geometry to compensate for that.

couldnt that be compensated with a anti-roll bar? or resolving it with applying an ackerman?[/QUOTE]

[BilletB]

Originally posted by Anvit Garg:
The wheel rate is computed based off the spring rate of your tires, the motion ratio of your bell crank, and the springs connected to the dampers. (Also the sprung and un-sprung weights)

So I guess this does not directly relate to your anti dive dilemma but I am sure it will be affected by your solution to the 20%

The wheel rate should NOT include the tire. The wheel rate is the rate at the wheel center. The ride rate then includes the tire along with your calculated wheel rate. The wheel rate also has nothing to do with sprung and unsprung masses. All you need to know to calculate the traditional wheel rate is installation ratio and the installed spring's rate. kw=ks*ir^2

You guys are butchering what anti-squat is (as is most often done). You can look at it many ways, but just make sure your way is correct. It has NO effect on your calculated wheel rate. It CAN have an effect on your pitch rates IF you choose to include it like that. I don't do that, I think it's not a clear way of looking at it and thinking of it.

Anti-squat and Anti-dive is just a geometric vertical jacking force that arises from the longitudinal forces at the contact patch being reacted on a line of action not in line with that longitudinal force . What percentage it is depends on how you decide to calculate it. I calculate it as the percentage of weight transfer caused by the longitudinal force at that end of the car that will be reacted by the suspension links and not the spring.

So in the end your load transfer from front to rear (accel) or vice versa (braking) is reacted through the springs and suspension links. The percentage tells you how much vertical force component you generate as a percentage of the load transfer that's caused by the longitudinal force from that end of the car. That can be seen as adding to or removing load from the springs depending if it's anti- or pro-. Add or subtract this to what your wheel rate would be doing if reacting all your load transfer and you can find pitch angles.

Pitch centers and pitch axes are just as much hog-wash as rollcenters and roll axes. They tell you NOTHING realistic. Your car does not roll about your roll axis or pitch about your pitch axis. Your car will not blow up if you have an undefined either, because well they tell you nothing anyways. The movement of the pitch center when making changes is not a cause, it's just a coincidental effect. If you constrain yourself by "traditional" pitch and roll center ideas you're missing lots of good real world design stuff. It's important to pay attention to what each individual link is doing and it's the kinetics of the car that really define how the car pitches and rolls NOT the kinematics.

Anti-dive/squat is not necessary for FSAE cars and you're only handicapping and limiting your car's handling adjustability if you do it. Not saying you can't build a fast car with it, but I am saying it's not what makes your car fast.

On this note, 20% is not a huge amount of anti-dive anyways. I would rather see 0% but I could work with 20% too.

[BilletB]

Originally posted by Yellow Ranger:
When the car is braking or accelerating, it will pitch to some degree, and probably heave to another, depending on the location of your pitch center/axis. My thinking is that if you look at side view kinematics like front view stuff, than when you have aarms that are parallel, although your instant center is an infinite distance away, it doesn't mean your car wont roll - the roll center would effectively become the outside tire (the point at which the car would roll over if laterally loaded), but if the vehicle rolls about an axis in the center of the vehicle, the driver is going to feel more of a roll sensation.

I think something along these lines happens in side view kinematics and pitch centers. If there was no pitch center, the car is still going to pitch about a point, it will probably just be about the tire contact patch, and feel less noticeable.

I've been trying to find the data where you could see the motion of the shocks but not having to much luck. Let me know if anyone else has experienced something like this or has a different explanation.

Your ideas of pitch and roll centers are way off. Parallel geometry will NOT put your 'pitch' or 'roll' center at a contact patch. Think about it. Until we forget these flawed concepts we will always draw poor conclusions. The car will not pitch and combo heave with dependence on your pitch axis. It will pitch and combo heave depending on your wheel rates and net vertical geometric forces. You guys need to invest in some shock pots and produce your own shock data for analysis. You'll learn a lot!

Last note about anti's. Since these forces act over the wheel's vertical direction of motion (like your wheel spring) think about what these large vertical forces may be doing to your suspension's ability to handle disturbances during braking and cornering when they are alive and decreasing pitch and/or roll. What happens to your mechanical grip? Transmissibility?? =]

[C.Zinke]

Originally posted by BilletB:
Last note about anti's. Since these forces act over the wheel's vertical direction of motion (like your wheel spring) think about what these large vertical forces may be doing to your suspension's ability to handle disturbances during braking and cornering when they are alive and decreasing pitch and/or roll. What happens to your mechanical grip? Transmissibility?? =]

Do you think a suspension with huge anti is less able to absorb disturbances?

[Tim.Wright]

I would say no to that.

Tell me if you agree with my resoning.

My understanding of suspension anti's is that the force vector at the tyre contact patch points towards its IC during braking/accel. Therefore the wheel does no travel 'around' the IC in the bump direction (no bump movement)

If you superimpose vertical disturbances onto this situation, they act largely tangential to the IC, therefore most of the disturbance is reacted by the spring and the wheel moves in the bump direction.

So theoretically you could have a setup with 100% anti dive which doesn't pitch under brakes, but wil still allow vertical displacements over bumps.

Practically though, if your a-arm bearings are seeing large forces they might not be so compliant to allow vertial displacements (i.e. binding). I can't comment on the likelihood of this at all as I haven't done the force analysis.

Does this make sense?

Tim Wright
Compulsory Life Member
Curtin Motorsport

[Wesley]

Originally posted by BilletB:
You guys need to invest in some shock pots and produce your own shock data for analysis. You'll learn a lot!


Like the ones we've used for about 4 years now? http://fsae.com/groupee_common/emoticons/icon_biggrin.gif

[Yellow Ranger]

Originally posted by Wesley:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by BilletB:
You guys need to invest in some shock pots and produce your own shock data for analysis. You'll learn a lot!


Like the ones we've used for about 4 years now? http://fsae.com/groupee_common/emoticons/icon_biggrin.gif </div></BLOCKQUOTE>

maybe they're giving us false conclusions...

[Steve O]

Do you think a suspension with huge anti is less able to absorb disturbances?

Timo's response is correct. Theoretically anti-dive should only be affecting contact patch in the fore/aft direction only; however in the real world you end up causing a loss of independence within the front end (for anti dive). This really isn't much different than your similar compromise with an ARB or a stiff suspension.

I believe the RCVD book actually answers this question when it recommends specifically against anti dive/squat for formula cars.

[The Stigg]

Do you think a suspension with huge anti is less able to absorb disturbances?

No Timo's response isn't correct.!
You have to handle with multibody dynamics not just the ones you would like to.
The suspension links transfer forces comming from the tire contact patches - but they also transfer forces comming from the sprung mass! And as nearly all FSAE Cars are equipped with dampers (corner Dampers and Tires) these forces act in a chronology!

Regards Andy

[C.Zinke]

Hehe, Andy is joining our discussion. I like that. Esspecially because your car do not use Anti-Dive and reflects your opinion. So first of all I think that Timo's response is close to correct. It misses some details but got the main point. I spoke to some experienced racecar engineers that had the same opinion. I was not able to notice major drawbacks by using huge antis either. But I am interessted in your thoughts... Can you explain it in more detail? I didn't get it so far. I will do an intership at BMW "Mechanical suspension system and vertical dynamics". I am curious what they think about this topic. As far as I know BMW does use a lot of anti. But they are limited by the understeering effect I mentioned. So lets see...

[Derf]

Why do vertical movements of the unsprung disrupt the chassis? Roll centers and pitch centers are synonymous but orthogonal. Both, when not at the ground want to move the contact patch with respect to the vehicle. In both cases the contact patch, if incapable of independent movement with respect to the chassis, will induce generation of lateral and longitudinal force respectively. But what DOFs of the contact patch are constrained or unconstrained with respect to the chassis? The better question is when are the DOFs limited. Add in tow variation's effect as Chris has stated and Andy's MBD approach, you have good things to think about.

[BilletB]

Originally posted by Steve O:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Do you think a suspension with huge anti is less able to absorb disturbances?

Timo's response is correct. Theoretically anti-dive should only be affecting contact patch in the fore/aft direction only; however in the real world you end up causing a loss of independence within the front end (for anti dive). This really isn't much different than your similar compromise with an ARB or a stiff suspension.

I believe the RCVD book actually answers this question when it recommends specifically against anti dive/squat for formula cars. </div></BLOCKQUOTE>

Timo's response is very incorrect. Using the instant center concept, under braking the chassis reaction force points from tire contact patch to IC. Proportional to AS percentage is the size of the VERTICAL component of this force. This force acts right along with the spring (as long as you're generating braking force at the front tires) and in fact unloads it a distance at the wheel approximately equal to AS vertical Force divided by the wheelrate. This is how your anti-dive works as a geometric force that opposes pitching. During the entire time you are braking there is a vertical force (at the contact patch due to suspension links pushing up on chassis) present because you have anti-dive. You going to tell me that won't affect how your suspension now functions when disturbed? It's amazing how significant suspension member forces become when you break it down that far. It's sooo wrong to think that suspension member forces don't effect wheel motions because only wheel bumps act "tangential" to the IC. So wrong.

[C.Zinke]

Hey BilletB,


his is how your anti-dive works as a geometric force that opposes pitching. During the entire time you are braking there is a vertical force (at the contact patch due to suspension links pushing up on chassis) present because you have anti-dive.

I wouldn't say so. The reason why Anti-X is working is because you build a supspension geometry that doesn't produce any additonal pushrod force under long. acc. In general this is done by designing a suspension that moves (bump/rebound) the contact patch on a curve that is perpendicular to the brakeforce acting at the contact patch. You always have a vertical force at the contact patch. It is just different which suspension members react on the force.


It's amazing how significant suspension member forces become when you break it down that far. It's sooo wrong to think that suspension member forces don't effect wheel motions

Could you explain that in more detail?

BTW: What is AS?

[Dave K]

Just curious, but has anyone here actually tried this setup in real life, instead of on paper?

[C.Zinke]

Originally posted by C.Zinke:

Since 2007 we are running about 100% anti-dive and 100% anti-squat in our cars. 2008 we were able to adjust it between 100-130% at the front axle.

[BilletB]

Originally posted by C.Zinke:
Hey BilletB,

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> his is how your anti-dive works as a geometric force that opposes pitching. During the entire time you are braking there is a vertical force (at the contact patch due to suspension links pushing up on chassis) present because you have anti-dive.

I wouldn't say so. The reason why Anti-X is working is because you build a supspension geometry that doesn't produce any additonal pushrod force under long. acc. In general this is done by designing a suspension that moves (bump/rebound) the contact patch on a curve that is perpendicular to the brakeforce acting at the contact patch. You always have a vertical force at the contact patch. It is just different which suspension members react on the force. </div></BLOCKQUOTE>
You can't NOT say so. Your idea of not "generating" push/pull rod force via geometry is off. Pushrod force is spring force. Always. Whatever force is in your spring due to its deflection, modified by your rocker/mounting geometry, is the force in the pullrod. Try a free body diagram. When your car brakes, there is some longitudinal load transfer. That load transfer is delL=cgh*Fb/wb, where delL is change in load, cgh is cg height, Fb is total braking force, and wb is wheelbase. Now, at that front contact patch the load in the spring should go up by delL/IR. But with anti-dive it doesn't. So if your spring isn't reacting the full load of the normal force at the tire what is?? That's right, the suspension linkages themselves. The linkages have to push up on the chassis while at the same time down on the tire so that the net force in the z direction is 0. It's how antisquat works. It doesn't magically reduce pushrod load. It lifts the chassis with a vertical force.

Now what you're telling me is you transfer load under braking to the front and the pushrod doesn't react it, AND the supsension linkages themselves don't react it. If that's the case then there would be NO increase in load on the front tires, during deceleration, with a cg I assume is above the ground. I don't think Newton is gonna like that. The load has to get to the front tire through something and your only options are push rod and suspension members.

Also, I don't know what you're talking about with brake force being perpendicular to contact patch movement. During that scenario you have 0% antisquat. Braking forces ALWAYS act on the car at the contact patch and parallel to the ground, they don't act up or down. Anytime contact patch movement is NOT perpendicular to this force you get AS and AD. When contact patch movement is perfectly vertical (parallel arms parallel to the ground) you get no anti-'s.


It's amazing how significant suspension member forces become when you break it down that far. It's sooo wrong to think that suspension member forces don't effect wheel motions

Originally posted by C.Zinke:
Could you explain that in more detail?

BTW: What is AS?

I could, but it's pretty complicated and understanding the overall effects of something like how anti-squat works is the basis to start thinking about it. AS is anti-squat.

[The Stigg]

Hi Chris, and all the others
this topic is far more complex than you might think. 2 years ago I started with the same VD-models like most of us. pitch-,poll-,yaw-center shizzle etc. But to be honest: Working with these simplified models is like masturbation. The more you do it, the more you think it's real

Then I was able to take part on a 7-post-rig testing day with a highly adjustable Le Mans car. We tried out a lot of different setups to verify our sugestions. And surprise surprise the recorded data was million miles away of what the literture tells us.

Back on topic:
Anti-X has an effect on the ability of the suspension to absorb disturbances. How big this effect is depends on your tires and the driving style.
This effect is hard to describe but I will give it a try.

1st step: While braking with a Anti-X car a lot of force is !directly! (only damped by the tire) reacted to the suspended mass (how big it is depends on the amount of anti-x)
2nd: This force will be transfered to all 4 contact patches instantly (how this force splits up on every sinlge wheel depends on the dynamics)
3rd: This force changes the potetial energy of the tire. And this is a bad thing as long as the tire is rolling at a significant speed as it produces dynamic imbalances in tire while it is deformed under rolling. A tire acts like a coupled spring and damper system. This creates a frequency generated by the unbalanced wheel that resonates with the spring frequency used by car and could therefore kill your contact patch pressure distribution and your ride quality.
Addon: This effect could be good or bad for a fsae setup and is highly dependend on the tire that is used. From my experience I would say Anti-X is good for radial tires with a low sidewall and relatively high damping (Conti,Dunlop,Pirelli) and its bad for diagonal tires with high sidewalls and low damping characteristics (Hoosier and Goodyear)

Of course you can build a extremly fast car with huge amounts of Anti-X but this is mainly dependend on your tires, the track and of course the drinving style.

[Lukin]

Originally posted by BilletB:
Last note about anti's. Since these forces act over the wheel's vertical direction of motion (like your wheel spring) think about what these large vertical forces may be doing to your suspension's ability to handle disturbances during braking and cornering when they are alive and decreasing pitch and/or roll. What happens to your mechanical grip? Transmissibility?? =]

To me that is the absolute crux of the conversation.

I'm not that much into all the theory stuff.

As most people have pointed out, anti-dive dictates how much longitudinal load transfer goes through the sprung mass and how much goes through the spring and how much through the suspension links.

The way I look at it, the transmission through the springs occurs at the wheel rate (2-4 Hz) while the transmission through the suspension links occurs at a higher rate (8-12 Hz) so any disturbance (bumps) will cause greater change in the grip at the contact patch.

The next point is why do we care about anti-dive and pitching? I've found drivers are real sensitive to pitch under brakes, so we do what we can to reduce it. Not always the amount, but the rate of pitch as someone alluded to. Excluding the loss of driver confidence it can create, too much pitch can increase rear locking and entry oversteer off the brake.

If the track was perfectly smooth you could run a lot of anti-dive for braking support and a soft front spring for front grip and performance over the kerbs.

Most tracks aren't smooth, so the more anti-dive we run, the more prone the car is to locking the inside front and pushing wide on corner entry as the load on the inside front tyre is varying too much over the bumps and disturbances in the road. Off course anti-dive effects the corner entry phase, unless of course you are off the brakes before you start to turn!

So with that in mind you take anti-dive off for bumpy circuits and give the car more front spring (if inside front locking and understeer is a drama over bumps, adding front bar won't be the fix as it will introduce co-dependance between the front tyres you don't really want). This comes back to transmission frequencies, it's better to have disturbances at 2 Hz than 10 Hz if your the tyre!

This hurts the roll distribution front to rear but overall you need to get the car to the corner (without the front tyre on fire and with the car on line) so you take what you can get. It's not perfect but it never is.

If you talk to drivers, they feel it as harsh and say that the more anti-dive you run, the harder it is to unlock a front lock up and you lose feel/compliance as you release the brake and reach full steering lock to the apex.

So that's my 2 cents, all without saying 'pitch centre' or 'IC'.

[Hatschi]

Hey Stigg, how do you apply brake force on a Sevenpost?

BilletB:
From the theoretical side I also don´t understand what the Antis have to do with the suspension transmissibility. The spring can handle the loads like ever. I think Timo is right.

Maybe you get some problems with the joints, the tires or the other realworld stuff like Stigg posted.


But:
You have the lift effect. Christopher, do you see it in your Data?

You have the movement of the suspension non-perpendicular to the vertical load. This will cause some loss of transmissibility.

You have the mentioned understeer. (I understand it now, thanks for that.)

I don't think you really need it. I see no real benefit. Keep it simple stupid.

But I like the idea of driving extrem short Swingaxlelength and maximum Antidive. Why don´t you drive more than 100%, Christopher? I know some hight quality racecars, which reached values near to 120%...



Greets from Munich

[The Stigg]

Hi Hatschi,

good question!
It's very easy! just pitch your car the same way you do it when you're measuring your cg loc.!

[Mark_W]

will anti's affect all vertical load through the suspension?

[gautham]

hello C.zinke i would be happy if u can help me out of here, i am designing my front double wishbone setup for 50% anti dive
for this setup both through 2d sketch and simulation through software i am gettin an anti dive of 50% when my upper wishbone is 16deg declined with horizontal and lower being parallel to horizontal
other datas-
wheelbase 1600mm, caster 8.8deg, cg height 310mm and 960mm from front axle
now the thing is this 16 deg of upper wishbone is it ok or can i get the same results in any other way


Originally posted by C.Zinke:
Say you have a steering angle of 30deg at your outside tire. (I know this is a lot, just for the example now). Then you can split your side force of the contact patch into a longitudinal and a lateral comonent. You will see that the longitudinal component (50% of your total tire side force) is acting on your suspension similar to a braking force. This stiffs up your supsension. This was a very short explaination. I hope it becomes clear.