If you had computers to diagram the action of mcpheson struts you wouldn't say that. there is several reasons why upper and lower a-arm suspensions are superior to mcphersons.And correct toe is another way to address turn-in but mostly to keep some semblance of camber. Ask any CRX racer.
One is much better adjustment of camber changes on compression
On any FWD vehicle the weight is roughly 60% on the front wheels which incurs understeer; a sway bar is used to generate flatter cornering at the expense of cornering force and the limit of adhesion. the action of a sway bar is to lift the inside wheel as it adds spring force resisting the compression of the outside wheel. That sooner puts the entire weight load of that end of the vehicle on that tire and that quickly limits the ability to not slide. Thus the asb does not increase the normal of the inside tire to the road. If you try lifting one side of your car and determine how far you lift before the other side lclears with and without the ASB you'll see what happens. And if you put scales under both plot the weights on both tires you'll see why ASB's only balance, not increase cornering in itself.
Sway bars are indeed used to balance the understeer/oversteer between front and rear suspensions but adding antisway bars on FWD vehicles merely increases understeer. Some say that been demanded by the safety people who want cars to off course frontward so the air bags are more dependable. If that vehicle is expected to have tires that only generate lateral g forvces of 0.7 the thats no problem but when thecornering force is raised toward 0.9 the performance will suffer.
In any case we have topwatched cars with and without front sway bars and with added ear bars and we have conclusively shown that less front antisway or more rear antisway improves test laps or race laps.
Thats not the purpose in a/xing or racing. So disconnecting front sway bars where the weight distribution is 60/40 reduces understeer considerably as desireable. Of course, adding a rear bar is definitely better if rules allow; and yes lowering with stiffer springs also is beneficial. (you might be surprised by the number of 'tricks' used in a/x as well as in showroom stock racing, like tennis balls inside springs)
Try it. Its no big effort to remove - or replace - the link between the shock and sway bar.
Bench racing at its best.
cheers.

 

In the example I used when in a right turn; no front sway bar would increasing "grip" in the front left, decreasing it in the front right in turn creates the rear to "pendulum". Increasing turn in.

You're right there are other options in STF, combining all the "tricks of over-steer" you wouldn't have to go to extremes like removing the sway bar. I'm going to look into the national champs setups, for curiosity.

The sway bar mod's purpose is to make the car rotate around tight cornering, like around cones in a/xing.

I don't know the rules for stock. I heard they allow sway-bar upgrades now. But do they allow removing? I can't imagine that's allowed in stock.

 

Haha... That is bench racing.

 

Here's a few:


or


or

No question that double A-arm is superior.

 

Would it? Too much compression on the front left = positive camber as roll increases, decreasing grip. I've never seen a picture of a macstrut car in full attack mode where the loaded tire/wheel wasn't falling over unless it was running like 3 degrees of static camber and had race tires.

I picked this car because it's cool lol it's still rolling over and the sidewalls are tiny.


Here, read post 10 most importantly, but the rest too.
Camber on a MacPherson strut car (Page 1)

Honestly I don't think you need rotation at all if your car is neutral and doesn't understeer much, if you're pushing so hard you're understeering you're driving wrong. Some of the fastest guys I know run neutral cars. Stock or close to stock ride height and the stiffest springs you can run on your dampers is where it's at with underpowered macstrut cars I think for the reasons above. Lower it too much and you screw the pooch on the camber curve, allow too much roll and the same happens. Sure you can rotate but can you power out?

 

\If the car is neutral there's no need for sway bars. Sway bars are used to increase/decrease understeer at that end of the car to get neutral. In the case of a Fit its understeer is severe and diconnecting the sway bay only helps reduce understeer.

In the example following you forgot to include body roll as the car loads horiziontally from centripetal force. Roll the car about 10 degrees and see what it looks lioke.
Oh, and having raced a Minii guarantee you the one here is pure race car, having almost nothing in common with a Fit stock class a/xer.
But good points.

 

Nice, very good but I have a couple of concerns;
1. there doesn't appear to be any body roll in your simulations. Put about 10 degrees rotation from the roll center in the location of the upper mcpherson and the lower body mount and see what happens. Going straight ahead good demo, but in a turn...
2. The lateral location of the upper shock mount and the lower ram location doesn't look like the Fit. Is yours generic?
The key is having body roll in the demonstration of the hub face angkle.
The real ones we did always ended up losing camber thus requiring great static camber settings, as much as 3-4 degrees.
You will avoid that with double a arms or limited compression length which is our favorite and I suspect inthe Mini shown, Thats in essence a giant go-cart in the manner of the old Margay karts, which were fatriqued out in less than a dozen races but their win record was fabulous. we thought Margay knew that so the limited flex gace superior cornering but needed a new cart purchased every month.
And put the force diagram in for sway bar and see what happens to the inside wheel as the outside wheel loads. The only cure is severely limitb travel or large static camber setting. There''s a reason race vehicles other than off road have small shock travel.

 

Kind of. There's no need for sway bars at all if you can run stiff enough springs to reduce the body roll and the track is smooth enough. The only reason for sway bars' existence is for street cars that you want to keep comfort in a straight line with softer springs and use the sways to reduce roll and increase effective spring rate only in corners where it needs it. If your springs are stiff enough the sway is just along for the ride, doing little to nothing. This is not the case with a stockish autox car, you are correct, so I digress.

Body roll of course I included, that's the whole point of all this and exactly why you have to decrease that roll as much as possible with macstrut cars, because the suspension does not effectively deal with camber under load.

Just saying I don't know if disconnecting the sway and the accompanying lack of effective spring rate is worth it for the few turns that the extra rotation might be needed... there is always LFB, flicks and the handbrake () for those situations too.

I know a guy that's pretty good at autox on this forum that would agree with me I think because he tried it lol I used to be in the small front bar or no front bar camp too but i've seen the light on macstrut cars and I see my previous dealings with double wishbone cars doesn't translate as well.

I'll leave it at that. Carry on.

 

With more than 50 cars to engineer I cannot recall even one that had weight bias more than 2% that didn't benefit from sway bars. Inherently the end with the most weight understeered and the one with less weight oversteered. Basic physics. As I said, the only need for antisway bars is balancing understeer /oversteer in the handling. That true of 3500 lb NASCAR as well as 1500lb vees. The trick is matching suspension travel with the stiffness of the ASB. And yes sometimes we wanted oversteer or understeer depending on the track. And the driver. Which is why of course you see 2 teamates in the same 'brand' car not doing equally well unless their cars match their driver skill and interest.
If you included body roll its not apparent. The mounts of the upper and lower body connections are equal height which isn't the case when the body rolls due to centripetal force.
Draw circles through the upper shock mount and the lower arm mount from the roll center and rotate the points 10 degrees. Then do the hub face angle measurement. Your vid will look a lot different and you will find the hub face will go positive unless you limit travel substantially less than the 4-5": on Fit.
you don't have to motion the movement of body roll just rotate the points 10 degrees and then watch the movement. The 'shortening' of the lower arm angle just kills the camber. When the body is rolled the upper mount rotates outward and the lowerer mount rotates inward, inducing positive camber. Your drawing has both sides of the mounting points at the same level which isn't the case. So drop the left upper mount by 2 inches and out by 1/2" and drop the lower mount by 1.5 inches and in one-half inch and see what the motion looks like keeping the hub face center the same height.
My students in physics go through the same stuff, too. They learned just how intuitive, knowledgable, and skilled it takes to be a good car suspension engineer. It is not even close to easy; matching a hundred variables to get the right setupin all manners of loads, angles, and speeds is just far far out.

 

I definitely know of several people that run with no sway bars at all who were nationally competitive or national champions. Just saying.

This all all relative semantics because like I said to begin with...

There is no formula to a fast car at this level, like I said, this is not F1. A fast car for someone else may not be a fast car for you. You can throw all the mathematics and engineering you want at it, it doesn't mean a whole lot.

This brings me back to when I said:
I like a neutral car, I set my cars up neutral, I don't like a lot of rotation because I don't use it for my driving style. I don't understeer much at full steam and i'm faster than a lot of people where I feel I need to be. Suspension or handling have never been my limiting factor, it's always been power

 

Now I get what you and Mahout are saying. Lorean is right about the camber curve.

The confusion is: Camber is measured relative to the car. When doing a static alignment/adjustments the car just happens to be perpendicular to the ground which sets them equal to each other. There isn't camber loss when loading relative to the car.

When the car rolls the camber relative to the ground is/can be lessen. Which is a product of the camber curve.

In an A-arm camber is gain exponentially faster (the more it compresses, the more camber relative to the car is gained). In a McStrut, the motion of the loading is linear (or close enough to it) that the camber curve creates positive camber relative to the ground.

 

You're right, esp in a/xing, the driver is what wins not the car. But if you throw out engineering then we would be racing in Model A's still, lol. That would be terrible haha. Driving preference is key, I prefer a balanced car too.

 

Yes yes yes! That's what i've been trying to say since our first discussion, I wasn't being clear, thanks for pointing that out, that's important. During roll the camber curve will put the pressure on the outside of the outside tire because the more it rolls the more + camber occurs. My picture in the other thread with the sidewall arrow shows that happening. I don't run camber bolts right now but I bet if I did I could get away with less air pressure before the tire starts folding over the sidewall.

Although I still stand by: Lowering a macstrut car will gain little, if any, camber by lowering alone

Haha yes good point, I just prefer to let those Honda guys do most of the work and then just tweak it a little bit to make it less comfortable

 

Camber is always measured relative to the road . Whatever the car does to affect camber is the reasion for all the math and testing. Just like in FI or NASCAR, the suspension setup is critical to performance. Though F1 does a lot of aero trickery, NASCAR or showroom stock, even a/xers take advantage of whatever aero is available.
Ever taped the gaps around doors? or used a good airplane wax? or an unfderbody flat panel with a little bulge? Ever adjudjusted panels on a oval to bulge a little within the template and flattened on the other side panels to create an airplane wing with the bulged side toward the inside of the oval to create horizontal 'lift' toard the inside of the oval? Thats just a beginning.
Its never cheating unless you're caught. Its actually a compliment to be called a sneaky *****. They look harder at you. Somerimes you deliberately 'mistake' so they don't see the sneaky part.
But all are right; thatrs way too involved when you a/x. Stick with the simple straightforward stuff to winI've got a wall full of trophies that justifies that.

 

Why didn't you just say so. lol.

My handicap, if you will, is that I was mechanic (I still do side jobs for $$) working on cars/motorcycles we only consider the "relative to vehicle" camber. All motion and measurements are relative (to us) to the vehicle.

Going from a technician to engineering I'm still trying to break old habits.

Technicians have no way to observe at or even measure a dynamic camber relative to the ground. We left that for the engineers. If there is an issue with a car it is possible to lift the car and observe dynamic camber to the car which can aid in diagnosis the problem. It was always frustrating to not have the proper equipment to diagnose, making me jealous of race teams.

Just venting.

Here's an easy example to visualize, a motorcycle is on its kick stand and you want to take "camber" (or really any) measurements/adjustments. If you adjusted relative to road there will be an issue.

 

I agree that aero package is important at any speed, car companies have been putting a lot of focus on the aero package for performance. It's tough for guys who participate in local events to put any focus on an aero package due to lack of resources.

Funny thing you mentioned under body paneling. I have been designing under panels for my Fit. Although I don't have access to a tunnel (not one i can put a car in anyway) I have been looking at the designs on higher end cars for reference. I was able to peek under a SLR Mclaren at the MB dealer, that's when I realized how important panels were.

What do you mean by "panels on an oval"?

 

Looking for rotation? Run 40+psi in the rear and trail brake on turn in.

 

^Yes exactly...

Also aero is not allowed in most classes the Fit could competitively run in afaik... it will bump you up to run with 500hp WRX and Evos lol

I am not sure if underpanels are included, but I suspect they are.

 

Hope everyone is having a great conversation about suspension.

Back to the OP post about autocrossing tires lol. I'm not quite ready for suspension modding yet.

So I went autocrossing with the BMW club this past weekend had a lot of fun. They are a very relaxed group. The stock dunlops on the base fit are just not very good for this a lot of sliding lol although no hit cones or off courses. I did work 3 sessions before I went out so it would be painful it I did go off course. Too many people did.

On the stock tires my best was a 46s flat lap while the kit shelbies averaged a 35s lap and the miniSs were around 40-42. It was a tight course and ended up down shifting from second to first coming out of a 120˚ turn

So I decided to buy a set of Kosei K4Rs 15x7 +40 with Dunlop Direzza ZIIs 205/50/15s from tire rack. With treadwear of 200 I'm set for the future. Will try them on later in the week when they arrive and check if I need spacers. If not in 2 weeks is another autocross which will be their first real test. I will run both morning and afternoon sessions. Now it will just be getting lots of practice. I may get 5mm spacers to bring it back to stock 45 after that. Would be civic adaptors from Motorsport tech.

 

Congrats. you certainly picked the right tires so there will be no excuses. good for you. A/Xing is a learning experience and learning with the right tires is the right way to do it. Couple of comments from our a/xers with walls of trophies:
1. do some tire pressure checking for handling in a vacant parking lot using a stowatch to measure differences on 90 dgree and quarter circle turns. our troops recommend about 44 psig front and 38 psig rear to start and about 1 lb more on the driver side.
2. Disconnect the front antisway bar. Don't remove it just take the driver side link out altogether. A timeof 46 sec indicates a tight course and turn in and grip is critical so reducing that horrendous understeer is mandatory. If you want, do your tire checks with and without the sway bar. But in both cases find the minimum time just before the front end washes out. Pick your entry and exit spots 20 yards or so from the apex to get a true measure; remember one of the most important attributes of cornering is braking and how fast your exit increases acceleration to the next corner. Thats why you want that 20 yards in and 20 yards out. Make your gates about 15 to 20 feet wide. Do both left and right hand turns.
3. And get some good brake pads, like Hawk street-race pads for the front. Dpn't worry about the rear.; its only real function is keeping the bumper from dragging the ground..
4. Make sure your seat belts are properly tightened by putting clips on the lab to shoulder belts to keep them tight so they don't loosen during your 'lap'. Serious a/xers install regular 6 point belts used in racing in addition to the OEM ones.
And welcome to racing. Work, work, work. A/Xing just getting starting with the efforts needed to race.
PS adding spacers will not increase offset; it will decrease. If your current offset is 40 mm, adding 6mm (1/4") spacers will decease it to 34mm. So don't expect to get back to OEM's 45mm. Our a/xers, and me, do not expect you to have a problem at 40mm. But at 34mm it may be too close even if your tire diameter is less (better gearing).
Did you check the a/x rules about tread width, ie offset and spacer use)? If there's a concern about the disconnected antisway bar just say its there; nothing in the rules say it has to function. Less offset means the tire is pushed out so camber imporoves a bit and ev ery bit counts just as the lower center of mass helps.
Use a torque wrench to be sure the wheels are properly set.Failure to do so can warp rotors.

Everyone thinks a/xing is just 'relaxing' is unaware. Go get 'em.