Rear Sway Bar

If you read the wiki I posted you would of noticed this, "This arrangement is not usually used with a leaf spring suspension, where the springs themselves supply enough lateral rigidity, but only with coil spring suspensions." Pan hard bars are a must have when racing a car with a solid rear axle although racing a car with a solid rear axle is questionable in the first place. Pan hard bars make the the imaginary into reality.

 

Good thought but completely opposite.

 

think about it when in a heavy corner the only thing keeping your trailing arms from deforming under stress is the thickness of the trailing arm itself and your shock absorber. people blow a lot of smoke about strut braces to prevent your cars body from flexing but what is preventing the strut and trailing arms from flexing?

 

There's merit to be had in stiffening the body. This preserves the geometry of the suspension when comparing front to back.

The strut is designed to flex in the axial direction. It's linked to pivot in the plane parallel to the wheel, which is required by the trailing arm design. I don't understand what you mean by strut flex though...

The panhard bar seems to connect the frame and the axle. Don't see how this would help the trailing arm any.

Can you spell out how the panhard bar would work on the Prius? Seems like the wrong tool for the job.

 

The only thing preventing your rear axle from swaying from side to side is your trailing arms and you rear shock and springs. a pan hard bar see picture above is attached to the chassis and the axle. Now the axle can not move left or right because there is like a 30 mm bar telling it NO absolutely not, you cannot do this. I wont let you. now remove the pan hard bar and the rear axle says ha ha you stupid car I am going to move from left to right as I please because nothing is stopping me from doing so. Get it?

 

Sorry when I say sway I don't mean body roll. and by body roll I don't mean get out of your car and roll around on the ground. when I say sway I mean it prevents your rear axle from sort of jumping or skipping from left to right.

 

Panhard Bars - Universal - SummitRacing.com

Here are some universal ones but I would personally make my own or have one made by a machine shop. The mounts on these look pretty flimsy. I would make the chassis mount out of some rectangular steel stock like this,

 

I understand the function of the bar, but you're describing on how it works on a car without trailing arms, as does the picture you've provided.

Installed as you've described on the Prius, the panhard bar will only affect the movement of the crossmember connecting the trailing arms... it's not going to do anything for the trailing arms themselves. They're still going to flex. You haven't solved anything with the bar, yet.

 

if you look at the new bushings vs your old bushings, you'll notice the poly bushings are much thinner than the rubber bushings. this will move the sway bar closer to the subframe, and possibly allow it to hit the subframe. we may need spacers to move the bar slightly away from the subframe.

 

ok, first, you'd need to attach a panhard bar to each trailing arm (which wouldn't work), because w/ the prius solid axle, the sway your talking about is from the arms flexing. its not like a true solid axle rear wheel drive car w/ control arms or leaf springs. you could put solid or some type of less elastic bushings where the axle attaches to the body if you wanted to tighten it up, or strengthen the arms somehow, but a panhard bar isn't gonna do much for a prius. it would only stabilise the side to which it is attached, if it was attached close to the spindle. the other side would still flex. a watts link might help a bit more, but i don't think its necessary. are you really gonna drive a prius that hard?

 

Sorry how am I describing how it works on a car without trailing arms. it only works on a car with trailing arms and a solid rear axle and coil over shocks. This is how our suspension looks. the pan hard bar prevents the rear assembly as a whole from moving side to side or laterally the trailing arms prevent the rear axle from moving longitudinally or front to back and the shock and coils and sway bar allows the whole assemble to move up and down. The rear sway bar determines the rigidity of the rear axle

 

i'm sure all this stuff you read is like the gospel and all, but this "dude" has had grease under his fingernails for over 30 years daily, and i understand how sway bars work. and let me tell you, the corolla bar works. until you drive a prius w/ upgraded bars, you don't know what you're talking about here.
the thicker rear bar helps, but the back wants to kick out if you turn sharp quickly. by adding a stiffer front bar too, it balances out.

you said it yourself:

"be careful as you can end up with rear wheel lift on a hard corner. On a race course this can be a good thing, as it'll allow you to rotate the car much more quickly in a tight corner.
On a public road, in a low traction condition (such as rain), this could mean you spin out into a telephone pole."

forget the race track; no one has any business driving that hard on a public road anyway. and its been known and printed for decades you want the bars balanced to avoid excessive over/under steer. installing just the rear bar-- which is designed for a car w/a stiffer front bar anyway-- is unbalanced and might cause you to hit that phone pole.

the whole point of upgrading the sway bars on a prius is not for slalom times, its to reduce the undesirable excessive body roll which our cars do have. this should be done in a balanced way.

 

You couldn't be more wrong;

Basically, both a panhard bar and a watts link serve the same function latterally locating the rear axle in the car, and linking the lateral loads generated when the vehicle is turning. As these loads increase the strenth of this linkage must be adequate to the task.

 

you don't understand how the prius rear axle works. it flexes. the panhard bar will do nothing to lessen axle flexing. it might compensate for soft bushings where the axle attaches to the body, but there is alot of flex in the axle, which is why the stiffer "stabiliser bar" per your diagram works. it does reduce (but not eliminate) flexing. a watts link could be attached to the spindle ends of the arms to keep the axle centered but would probably not affect flexing much.

 

First of all I didnt say this,

"be careful as you can end up with rear wheel lift on a hard corner. On a race course this can be a good thing, as it'll allow you to rotate the car much more quickly in a tight corner.
On a public road, in a low traction condition (such as rain), this could mean you spin out into a telephone pole."

Read more: http://priuschat.com/threads/rear-sway-bar.53494/page-15#ixzz2LyFarppq

second of all:

69shovlhed said: ↑
"the thicker rear bar helps, but the back wants to kick out if you turn sharp quickly. by adding a stiffer front bar too, it balances out."

the back wants to kick out because the front wheels turn the corner and the back wheels want to keep going straight. this can be fix by unloading the front end by applying slight pressure on the brake and gas at the same time when entering the corner (left foot braking) this will balance the car front to back allowing you to take the corner flat out. Having a loose sway bar in the front will help you to load the tires better in a sharp corner giving you more traction on the wheels that are powering the car forward. adding a stiffer front brace will only wrap you around a telephone pole sooner than trying to race a car with a solid rear axle FF layout and no pan hard bar.

like I said before having a loose front sway bar and a more rigid rear sway bar increase under steer not over steer like you said. the fact that the rear of the car kicks out has nothing to do with the sway bars unless you are running stiff bars in the front which promote over steer.

 

Watch the tone dude, keep the discussion constructive. Explain yourself, ask questions, but don't be throwing any stones.

 

What the heck are you talking about you make absolutely no sense.

*Mod Note: be nice, no need for the snarky stuff.

 

the point of a pan hard bar is not to prevent flexing but to keep the rear axle from moving laterally from side to side in a sharp corner. sway bars stop the axle from flexing not a pan hard bar they are 2 separate things.

 

I'm not reading, I'm talking to guys that have built and tuned race cars. Just trying to do my homework before I take my project out on the track. And there are guys out there running with stiff springs, no front roll bar, and a rear roll bar. And some of these guys are actually winning their classes. Is their word gospel? No, but I'll take it with more consideration.

I'm not going to race my Prius, so I'm not going to set it up as such, and I'm not going to test your claims. So how can you back them up besides your seat-of-the-pants opinion? Just wanna know why you're so adamant, that's all..

 

they run stiff springs which would suck on the street. if you like the ride of a conestoga, you'd love racing springs. but since we have potholes and such to worry about, stiff racing springs are out of the question.
the only way i can back up my seat of the pants yaw rate sensor is for you to come here and drive in my car. if you did, you'd understand. it would be quite obvious to you.