Landracing Forum
Tech Information => Technical Discussion => Topic started by: maguromic on February 16, 2009, 03:23:18 PM
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Just curious what types of sway bars (if any) are used in LSR. Trying to start a discussion on what works and what doesn't work and why. I know we don't turn left or right.
Tony
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At least not on purpose. :-D
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Just curious what types of sway bars (if any) are used in LSR. Trying to start a discussion on what works and what doesn't work and why. I know we don't turn left or right.
Tony
I removed my front sway for LSR, but I'm running a truck, and I did it for safety reasons:
A stiff front bar will cause oversteer. Understeer is acceptable, oversteer isn't.
My thinking is it will be easier to correct if I get sideways. Street testing has confirmed that it's not as tail-happy.
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Knowing a little about Anti Roll (Sway) bars in drag race applications it's possible that with a softly sprung car an anti roll bar might be helpful in increasing roll-stiffness (lessening side to side sway).
REX?
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The 222 Camaro originally had a front anti roll bar but we had to take it off when we went to 3'' blower pulleys
At the Nov EL mirage meet Troy got real sideways at 225-230 mph when he got to the marbles but was able to keep from spinning. They now offer roll bars for 4/links on rear that I would have done.
JL222
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Yup, a stiffer rear bar will do two things: give more understeer, have more rear traction when the vehicle is "upset".
I used to race SCCA Solo2 (autoX) and played around with front and rear sways on my Camaro.
Would it apply to LSR in a near-spin situation? I'm not sure, but it makes sense.
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Mac, I only disagree about 110%. We are not running on asphalt here. If you are worried about understeer, don't, you will already be spinning. If your front suspension wants to shift the weight bias to the outside tire when you get loose, you will never recover. I run my car like a brick, heavy springs, sway bars on both ends, consistantly over 200 mph. Only spin due to driver jet lag. jmo.......... :-D
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Mac, you've got it exactly backwards. Making the front bar heavier, relative to the rear, will generally make the car understeer. Likewise making it softer will make the car oversteer. A stiffer rear bar, relative to the front, causes oversteer, and a softer rear bar makes it understeer.
This relationship between bar stiffness and over/understeer is well understood by anyone in any type of racing that involves turning corners. Basically, you stiffen a bar to make that end of the car take more of the load. You're asking the outside tire at that end of the car to take more of the cornering load, relative to the outside tire at the opposite end of the car. That makes it break loose sooner. So more bar, at either end, has the effect of reducing traction at that end and increasing it at the other end.
Increasing spring rates has the same effect: more spring means that end takes more of the load and therefore gives it less traction and gives more traction to the opposite end. For equal reductions in body roll, a heavy spring will load the outside tire less than a heavy sway bar. The other factor is that sway bars take away the independence of the suspension; hit a bump on the left side and the right side feels it too, and vice-versa. Heavy springs are the preferred way to control body roll as a result. Sway bars are generally a tuning device to balance the car once it's sprung correctly.
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Dunno, a stiff rear bar made my Camaro plow, and a stiff front made it tail happy. Go figure. Not a little bit either.
No warranty expression or implied, your results may vary. Professional driver on closed course. Offer void in Alaska and Hawaii.
Understand my truck has spring rates on it that are very high to begin with, and naturally oversteers.
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McRat,
Your experience with your Camero goes against all logic. An anti roll bar (the real name for the thing) transfers weight from the inside wheel to the outside wheel. This increase of load on the outside wheel causes the tire to go to the down slop side of its traction curve so it actually generates less turning force even with its increased load there for it looses traction and if it is the front it understeers and if it is the back it oversteers. This is all true for running on a flat or near flat surface it you are running on a banked surface it changes.
I agree with Bob, run heavy springs, stiff shocks and if you want to run anti roll bars make them heavy. We are going straight not turning.
When I was doing some road racing we had a kind of "rule of thumb" for anti roll bar stiffness. If you wanted it to be stiff enough that you could actually use it to tune understeer/oversteer you wanted it's roll stiffness to be about 25-30% of the suspensions. Worked for us.
Rex
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Mac, you've got it exactly backwards. Making the front bar heavier, relative to the rear, will generally make the car understeer. Likewise making it softer will make the car oversteer. A stiffer rear bar, relative to the front, causes oversteer, and a softer rear bar makes it understeer.
This relationship between bar stiffness and over/understeer is well understood by anyone in any type of racing that involves turning corners. Basically, you stiffen a bar to make that end of the car take more of the load. You're asking the outside tire at that end of the car to take more of the cornering load, relative to the outside tire at the opposite end of the car. That makes it break loose sooner. So more bar, at either end, has the effect of reducing traction at that end and increasing it at the other end.
Increasing spring rates has the same effect: more spring means that end takes more of the load and therefore gives it less traction and gives more traction to the opposite end. For equal reductions in body roll, a heavy spring will load the outside tire less than a heavy sway bar. The other factor is that sway bars take away the independence of the suspension; hit a bump on the left side and the right side feels it too, and vice-versa. Heavy springs are the preferred way to control body roll as a result. Sway bars are generally a tuning device to balance the car once it's sprung correctly.
Generally speaking, increasing anti-roll bar stiffness will increase the slip angle of the outside tire at that end of the vehicle. Stiffen the rear, car gets looser. Stiffen the front, car gets tighter. But this isn't always the case and exceptions are not uncommon. Since McRat is working with a truck and not a performance car it isn't at all surprising it would react differently.
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I would certainly agree that stiff spring rates are a good thing for flat surfaces. But I couldn't see how a 45lb swaybar on the nose was going to help me in any way shape or form unless I was going to run a cabover camper. As for understeer vs. oversteer? All I can say is what I experienced.
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I had to go back and look and my notes from back then, and you folk are right. I remembered it backwards. I remembered switching front and rear bars to correct understeer, but got the directions backwards.
My apologies.
:|
But the truck does seem to slide out slide out slower with the front bar off on the street. I suppose something else could be causing it.
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With a straight front or rear axel and a split wishbone or hairpins the axle becomes a very stiff anti-roll bar .
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You guys with heavy springs ''have fun spinning your wheels''
JL222 :-D
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Jl222, you are right about traction challenges with stiff springs, for good traction you want the suspension to be compliant but if you are running your car very low to the ground stiff springs are needed. And some springs are better than none.
Rex
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Dave Macdonald spun his to 311..................... and no loopedy loops.................... Car weighs 6200# and runs stiff springs..........................
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Dave Macdonald spun his to 311..................... and no loopedy loops.................... Car weighs 6200# and runs stiff springs..........................
Don't forget about Lindsleys and Leggitt 333mph + and solid suspension. When I asked Les how much weight he had in it he said ''more than you would believe''.
JL222
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O.K. guys I have a similar question for you.
I understand the basics of swaybars in a road race situation, but what would be reccomended in my car for running at mile/Bonneville events. My car is an allwheel drive- 4 cylinder- turbo charged -moderate power (when compared to alot of the folk on here ) (around 1,000 awhp) - the car has independent rear suspension-coil over shocks. So I was thinking of adding a rear swaybar to the car to try and increase its highspeed stability.
Do you think this would help or make it worse.
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Boy of boy, I sure did enjoy Les' 15 minute warm ups in the pits.............. :roll:
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Fast Evo, I don't claim to be an engineer, and I stayed at home last night, but a lot will depend on the downforce of the car. Does it have a spoiler? Whats the wheel base? How heavy is the car?
You will find on this thread and many others that we all have different opinions on everything from aero to weight bias to tire widths, etc.
Someone paraphrased a statement from Mike Cook (Mr. Salt) recently who said forget what anyone else says, every car handles differently and you just have to try it out and see.
Thats part of the fun................and by the way, as soon as you have it figured out on dry salt, a thundershower will hit. Then you get to start over!!! Thats why we race for big bucks............ :-D
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In theory the most spin resistant suspension would be a front anti-roll bar and independent rear suspension with a z-bar .
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O.K. guys I have a similar question for you.
I understand the basics of swaybars in a road race situation, but what would be reccomended in my car for running at mile/Bonneville events. My car is an allwheel drive- 4 cylinder- turbo charged -moderate power (when compared to alot of the folk on here ) (around 1,000 awhp) - the car has independent rear suspension-coil over shocks. So I was thinking of adding a rear swaybar to the car to try and increase its highspeed stability.
Do you think this would help or make it worse.
With 1000 hp and a slippery car you could go well over 250mph. Like Bob says I would make sure the car has downforce and enough weight to keep from flying. I've seen a few small cars fly at bville on utube for no apparent reason but I believe lift.
All wheel drive should help in the traction dept.
I would like an anti-roll bar on the 222 car only for help in a spin.
You don't want to go to bville,fly the car and say ''I should have done that''
Good Luck JL222 :cheers:
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Well JL222- The car I am racing now is pretty stable in the lift dept. ( I've had it to the A2 tunnel), but it wanders around alot at high speeds,it hasn't and hopefully never will see the salt. I suppose I should of asked it as a 2 part question.
1-would a rear bar help with high speed stability on my EVO= boxy not very aero, 100 inch wheel base, awd, to be raced on asphalt only ?
2-would a rear or front or both bars be beneficial on the car I plan to take to Bonneville, which is an eagle talon= small, way more aero, short wheelbase (94 inches ), will also have coil overs. This car will also start running in G/production supercharged.
I hope this question comes across right as I am just trying to get some info from the people who have done it before and tried different things.
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Well JL222- The car I am racing now is pretty stable in the lift dept. ( I've had it to the A2 tunnel), but it wanders around alot at high speeds,it hasn't and hopefully never will see the salt. I suppose I should of asked it as a 2 part question.
1-would a rear bar help with high speed stability on my EVO= boxy not very aero, 100 inch wheel base, awd, to be raced on asphalt only ?
2-would a rear or front or both bars be beneficial on the car I plan to take to Bonneville, which is an eagle talon= small, way more aero, short wheelbase (94 inches ), will also have coil overs. This car will also start running in G/production supercharged.
I hope this question comes across right as I am just trying to get some info from the people who have done it before and tried different things.
Evo
I don't know for sure but I can't see how they would't help. Don't they come from the factory with anti-roll bars?
JL222
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I was driving that black brick shown in the 'avatar' with no wing, no weight{ballast}, and no sway bar.It went straight as a string up to 150, then you could feel it pick up and float. I white knuckled it from side to side,,,, almost felt like torqe steer. I'll add weight, wing, and bar next time.
RICK
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fast Evo
More caster might help also.
JL222
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Tony, If you do decide to run a Anti roll bar, try and make it adjustable. a lot of race cars have a bar with ams that run parallel to the ground. The then run adjustable links down to a point on the lower control arm. If you do this you can have several points on the arms that you can move to. Moving the link closer to the bar will make the bar stiffer and moving away from the bar will give you a softer bar (more mechanical advantage. Because all cars are different, spring rates, cg location, roll center heights and off set; it will be pure luck to have the proper bar dia and length. A adjustable bar will at least get you closer. Or you can set the car on a jig and measure all the points and spring rates and do the calculations and come with a bar that will be much closer. I am building a streamliner and I have a anti roll bar on the rear. I did this for safety reasons. I don't want any chassis roll in the car with a track width of only 23 inches. If the car were to spin and the chassis rolled over I am sure it would dig in and put me on my lid. ( don't want to see blue, white, blue white and so on). Hope I didn't confuse you, I'm not very good at describing things some times.
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Thanks Jerry, I am going to fab up some blades so I can adjust it easily. I was looking to see what others have done on the salt. Steve Conover is helping with the chassis and aero set up . You might remember him from your Indy and IMSA days.
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Jerry O
Allright a streamliner with suspension!!
JL222 :cheers: :cheers:
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As a crewman on Ed Stuck's #299 B/FR I can tell you that #299 doesn't have any antiroll bars. The rear end is mounted solid, the front axle has the old original style transverse leaf spring with about an inch of travel. #299 has lead weight in the front, middle & rear of the car. the ones at the rear take 2 men & a boy to lift them in. Also in the rear is the water reservoir (about 40 gal.)(do the math). And I think there is lead shot still in the frame rails from when Neilson owned the car. The dry weight is about 4700 lbs.
But, then our speed could be due to the superior aerodynamics of the car :wink:
Bob Davis
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Sounds like you guys are on the right track!
KISS -keep it simple . . .etc.
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jl222 ....... I will be running the car at Maxton so I think suspension is need there. The car is a flat bottom car and the ride height can be adjusted from 1 inch to 2 inch inch ground clearance. The way I have designed it I can run as soft or as stiff as I need. I can also lock it solid if need. The shocks are gas shocks that require no coil over springs. The ride height, compresion, rebound. and spring rate are adjustable also.
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As a crewman on Ed Stuck's #299 B/FR I can tell you that #299 doesn't have any antiroll bars. The rear end is mounted solid, the front axle has the old original style transverse leaf spring with about an inch of travel. #299 has lead weight in the front, middle & rear of the car. the ones at the rear take 2 men & a boy to lift them in. Also in the rear is the water reservoir (about 40 gal.)(do the math). And I think there is lead shot still in the frame rails from when Neilson owned the car. The dry weight is about 4700 lbs.
But, then our speed could be due to the superior aerodynamics of the car :wink:
Bob Davis
How did Ed like the ride when the salt was real bad a few years back? I know, my brother Jim was at J and S East Valley Garage when he was there talking about it. Jimmy wished I was there to stick up for suspension.
I just finished reading about the suspension on the Bloodhound 1000 mph attempt [100mm or 4'' of travel droop and bump.
Some real insights on why to use suspension.
JL222 :-D
Go to [Thrust powered land speed information] to read about Bloodhound, it's near bottom of topics on home page.they tell all about it, great stuff