Rear sway bar needed?
03-03-02, 08:17 PM
#1
Junior Member
Thread Starter
Join Date: Feb 2002
Location: LA
Posts: 29
Likes: 0
Received 0 Likes
on
0 Posts
Rear sway bar needed?
Is the rear sway bar needed for the car to drive properly? I heard on a thread that some people removed the rear sway bar so that the rear doesn't fishtail. Is there any future problems with removing the rear bar? Anyways, the reason i am asking is that my rear sway bar is bent out of shape and i have removed it cause it was wobbling in the rear. Wondering can i drive it safely until i get some ST sways.
03-03-02, 11:53 PM
#3
Rotary Freak
dont know if removing it will increase handleing,
suspension tekniques whole selling scheme is to sell you a bigger bar for increase road holding ability.
go with the st its nice,also dont forget poly bushings.
suspension tekniques whole selling scheme is to sell you a bigger bar for increase road holding ability.
go with the st its nice,also dont forget poly bushings.
03-04-02, 12:26 AM
#4
Old [Sch|F]ool
It all depends on your driving style and how much power you have.
My car for example never had much power (maybe 125-130hp at the MOST in street trim), so I would never get as much speed in the straights, and I could get on the power earlier in the corner, and my car understeered like a bastard despite having negative camber in the front and the huge 18mm rear bar.
I tend not to brake while cornering - I wait until the braking is almost done before turning in. This also results in understeer. I also turn in gradually - turning in too sharply unsettles the chassis and causes big oversteer.
Basically, if you're a very aggressive driver, and/or have lots of power, (160-180+hp) removing the rear bar could be of benefit to you. How does the car feel to *you*?
BTW stiffening the whole suspension up doesn't increase roadholding, that's what the tires do. Making one end stiffer makes that end lose traction first... for example let's put a huge bar on one end. That causes more weight transfer to the outside tire, because the bar fights body roll by picking up the inside tire and pushing down the outside tire. In extreme conditions the inside tire comes completely off the ground, which is 100% load transfer. (ever watch an older GTI go around sharp corners?) Basically you are unloading the inside tire and overloading the outside tire, resulting in less traction at that end.
The opposite, of course, is true when you make things softer. You reduce load transfer and increase traction at that end.
Be careful not to confuse weight transfer with body roll... weight transfer is a function of roll center height and track width, body roll is a function of the suspension. You can, however, use body roll to control load trasfer. The suspension needs only be stiff enough to keep it from bottoming out, any stiffer than that and you'll have less grip because the tires lose traction more easily over bumps.
My car for example never had much power (maybe 125-130hp at the MOST in street trim), so I would never get as much speed in the straights, and I could get on the power earlier in the corner, and my car understeered like a bastard despite having negative camber in the front and the huge 18mm rear bar.
I tend not to brake while cornering - I wait until the braking is almost done before turning in. This also results in understeer. I also turn in gradually - turning in too sharply unsettles the chassis and causes big oversteer.
Basically, if you're a very aggressive driver, and/or have lots of power, (160-180+hp) removing the rear bar could be of benefit to you. How does the car feel to *you*?
BTW stiffening the whole suspension up doesn't increase roadholding, that's what the tires do. Making one end stiffer makes that end lose traction first... for example let's put a huge bar on one end. That causes more weight transfer to the outside tire, because the bar fights body roll by picking up the inside tire and pushing down the outside tire. In extreme conditions the inside tire comes completely off the ground, which is 100% load transfer. (ever watch an older GTI go around sharp corners?) Basically you are unloading the inside tire and overloading the outside tire, resulting in less traction at that end.
The opposite, of course, is true when you make things softer. You reduce load transfer and increase traction at that end.
Be careful not to confuse weight transfer with body roll... weight transfer is a function of roll center height and track width, body roll is a function of the suspension. You can, however, use body roll to control load trasfer. The suspension needs only be stiff enough to keep it from bottoming out, any stiffer than that and you'll have less grip because the tires lose traction more easily over bumps.
03-04-02, 12:31 AM
#5
Old [Sch|F]ool
i can't edit that post? anyway i had a brain fart - that one part should read "weight transfer is a function of CENTER OF GRAVITY and track width".
Roll center is a whole nother ball game, and part of how the suspension determines how much body roll there is... explaining that would take another five pages but basically it's why the stock 1st-gen suspension isn't so hot, the rear roll center is too high...
Roll center is a whole nother ball game, and part of how the suspension determines how much body roll there is... explaining that would take another five pages but basically it's why the stock 1st-gen suspension isn't so hot, the rear roll center is too high...
03-04-02, 02:53 AM
#6
Rotary Enthusiast
well i have talked to some experts in autox and track racing and they have told me with the suspension setup that 1gen has, the front sway-bar is suppose to be way bigger than the rear. So some ppl that don't upgrade the front one, just remove the rear one on track. But I don't think it would be a good idea on street.
my 2 cents
my 2 cents
Trending Topics
03-04-02, 03:47 PM
#8
Guys,
When I raced we had a nearly stock suspension, just front bar, springs and some camber - we were just starting out at the time. (and about 105hp
We ran Blackhawk Farms Raceway for one race with the bar on - in fact the school race, I drove the Rx3 and my bud drove the Rx7... After the morning experience Tim took off the rear bar in the pits between practice and race, he ran a whole second faster with it off but the car was less fun to drive as it nearly ruined turn-in response, it made it more of a chore to drive fast.
Now, if you do this on the street, the speeds you reach you will not experience the sudden snap oversteer we were trying to avoid, so you won't see any benefit from removing the bar, in fact you will only notice that car has a "heavy ***" and won't turn into corners with any quickness (one of my favorite part of the cars street handling) I have a 79 I like to run around in.
So, if you race the car with the SCCA (not AutoX) then take it off... but put it on again for AutoX and if you get a panhard bar or tri-link.
If you want to talk handling for Rx7's - I kinda figured it out - contact me at my e-mail on my profile.
When I raced we had a nearly stock suspension, just front bar, springs and some camber - we were just starting out at the time. (and about 105hp
We ran Blackhawk Farms Raceway for one race with the bar on - in fact the school race, I drove the Rx3 and my bud drove the Rx7... After the morning experience Tim took off the rear bar in the pits between practice and race, he ran a whole second faster with it off but the car was less fun to drive as it nearly ruined turn-in response, it made it more of a chore to drive fast.
Now, if you do this on the street, the speeds you reach you will not experience the sudden snap oversteer we were trying to avoid, so you won't see any benefit from removing the bar, in fact you will only notice that car has a "heavy ***" and won't turn into corners with any quickness (one of my favorite part of the cars street handling) I have a 79 I like to run around in.
So, if you race the car with the SCCA (not AutoX) then take it off... but put it on again for AutoX and if you get a panhard bar or tri-link.
If you want to talk handling for Rx7's - I kinda figured it out - contact me at my e-mail on my profile.
03-04-02, 08:19 PM
#9
Junior Member
Join Date: Feb 2002
Location: Nanaimo, BC, Canada
Posts: 42
Likes: 0
Received 0 Likes
on
0 Posts
Most of this is just experience from games like Sports Car GT and NASCAR Heat, but it seems as you increase rear bar diameter, the car will have more of a tendency to oversteer. So if your rear bar is removed, and you still have the front bar on, your car will understeer compared to having the rear bar on as well. Also, if you go to buy new roll bars, ask around and see what sizes other people have. Too close and you could be causing excessive oversteer.
See ya in the ditch!
See ya in the ditch!
03-04-02, 08:44 PM
#10
Old [Sch|F]ool
That sudden snap oversteer is due to two things... the ****-poor geometry of the stock 4-link binding up at high roll angles, and a too-high roll center in the rear.
The Tri-Link or similar will fix the binding... a Panhard rod will fix the roll center.
The Tri-Link or similar will fix the binding... a Panhard rod will fix the roll center.
03-05-02, 01:27 PM
#11
Peejay is absolutely right...
Turbo Crazy... Well you're right, if everything in the suspension works correctly.
as peejeay mentions, due the poor geometry of the rear 4-link design, the axle rolls too much and binds with the watt's, this causes the car to get into a condition where the effective roll resistance is practically solid, therefore the snap oversteer.
If you remove the sway you allow more freedom of movement for the axle to rotate, therefore delaying the "snap".
Now if you add a panhard and remove the watts - (the Universal fix for this style of suspension) - then you effectively remove one of the sources of bind. However adding the panhard lowers the roll center enough that to gain back some turn-in response you need to increase roll resistance - it's like going too far with one adjustment only to have to re-adjust for what you just did. Now you have to go from 150lb or 175lb rear springs to ~200-250 and add a '85 rear sway bar or an adjustable.
The tri-link is another great device that eliminates bind altogether by also limiting the roll of the axle so that it no longer rolls forward or backward. This elminates wear on the tail shaft of the transmission as an added benefit, and really allows the Rx7 to work.
So, for the street, get the suspension techniques suspension kit, it worked well for me in ITA my first year and did OK in CSP...
Turbo Crazy... Well you're right, if everything in the suspension works correctly.
as peejeay mentions, due the poor geometry of the rear 4-link design, the axle rolls too much and binds with the watt's, this causes the car to get into a condition where the effective roll resistance is practically solid, therefore the snap oversteer.
If you remove the sway you allow more freedom of movement for the axle to rotate, therefore delaying the "snap".
Now if you add a panhard and remove the watts - (the Universal fix for this style of suspension) - then you effectively remove one of the sources of bind. However adding the panhard lowers the roll center enough that to gain back some turn-in response you need to increase roll resistance - it's like going too far with one adjustment only to have to re-adjust for what you just did. Now you have to go from 150lb or 175lb rear springs to ~200-250 and add a '85 rear sway bar or an adjustable.
The tri-link is another great device that eliminates bind altogether by also limiting the roll of the axle so that it no longer rolls forward or backward. This elminates wear on the tail shaft of the transmission as an added benefit, and really allows the Rx7 to work.
So, for the street, get the suspension techniques suspension kit, it worked well for me in ITA my first year and did OK in CSP...
03-05-02, 08:15 PM
#12
Old [Sch|F]ool
I had a diagram of what happens in the rear suspension... basically the binding is because of the fact that the upper and lower links are different lengths and not parallel to each other.
When the car leans over, the axle rotates about the roll center. (In the case of a stock car, this is the center pivot of the Watts) The lower links are okay but the uppers have a lot of sideways motion to them, because they are so much shorter. You will get to a certain point of axle motion, and they will simply stop moving altogether. Lowering will make this a lot worse.
Removing the rear sway bar does not help... in fact it makes it easier to get to the binding point. However the car will be understeering so much that it's not scary when it binds up.
Ideally you'd want to stiffen up the rear suspension and not lower it, so that the suspension never gets to the binding point. You need to do other things to the suspension to make the car driveable after that, though...
As for roll center heights, this is probably the best explanation I have ever seen...
When the car leans over, the axle rotates about the roll center. (In the case of a stock car, this is the center pivot of the Watts) The lower links are okay but the uppers have a lot of sideways motion to them, because they are so much shorter. You will get to a certain point of axle motion, and they will simply stop moving altogether. Lowering will make this a lot worse.
Removing the rear sway bar does not help... in fact it makes it easier to get to the binding point. However the car will be understeering so much that it's not scary when it binds up.
Ideally you'd want to stiffen up the rear suspension and not lower it, so that the suspension never gets to the binding point. You need to do other things to the suspension to make the car driveable after that, though...
As for roll center heights, this is probably the best explanation I have ever seen...
from my files
I agree, a lower rear roll center increases the distance between the
rear center of gravity and the roll center, thus making the car more
predictable. As an example: lets say a stock setup has 100 lb springs
and the distance from the roll center to the rear center of gravity is 6
inches, under race conditions this distance could change from 3 inches
to 9 inches, the roll stiffness is directly proportional to this
distance thus changing from twice as stiff to 50% softer as you
drive/race. The same car with a panhard: say the distance - roll center
to rear CG is increased to 12 inches, this will cut your roll stiffness
in half thus requiring stiffer springs or swaybars, so you change to 200
lb springs, now under race conditions the distance (roll center to rear
CG) will change from 10.5 to 13.5 inches, the roll stiffness now changes
a tiny amount in comparison... much easier to drive.
I agree, a lower rear roll center increases the distance between the
rear center of gravity and the roll center, thus making the car more
predictable. As an example: lets say a stock setup has 100 lb springs
and the distance from the roll center to the rear center of gravity is 6
inches, under race conditions this distance could change from 3 inches
to 9 inches, the roll stiffness is directly proportional to this
distance thus changing from twice as stiff to 50% softer as you
drive/race. The same car with a panhard: say the distance - roll center
to rear CG is increased to 12 inches, this will cut your roll stiffness
in half thus requiring stiffer springs or swaybars, so you change to 200
lb springs, now under race conditions the distance (roll center to rear
CG) will change from 10.5 to 13.5 inches, the roll stiffness now changes
a tiny amount in comparison... much easier to drive.
03-06-02, 01:21 PM
#13
Senior Member
Join Date: Apr 2001
Location: indiana
Posts: 406
Likes: 0
Received 0 Likes
on
0 Posts
i've had mine off for several months now will no ill effects on street driving. it does take more to get the rear end to kick out... something i kinda miss! i've noticed the steering feels a bit heavier too. i got a taste of understeer making a quick corner last month.... not acceptable! i hate understeer! then again, the first things i learned to drive were 3- and 4- wheelers with oversteer a'plenty. on a related note... if i were to reinstall the bar, would it be better to go with stock rubber or polyurethane bushings? i'd think the poly's might contribute to the binding in the back end.
03-06-02, 06:22 PM
#14
Full Member
Join Date: Jan 2002
Location: Yarmouth, Nova Scotia, Canada
Posts: 61
Likes: 0
Received 0 Likes
on
0 Posts
How about the combination of a Suspension Techniques front bar and a Racing Beat rear bar? Anyone used this combination? I've been buying suspension parts all winter (waiting for clear roads) and I have a line on a ST front bar. Would you recommend this setup?
Thread
Thread Starter
Forum
Replies
Last Post
need RX7
2nd Generation Specific (1986-1992)
11
08-19-15 08:27 AM