Author Topic: Sway Bars  (Read 9382 times)

0 Members and 1 Guest are viewing this topic.

Offline maguromic

  • Hero Member
  • *****
  • Posts: 1736
    • http://www.barringtontea.com
Sway Bars
« on: February 16, 2009, 03:23:18 PM »
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
« Last Edit: February 16, 2009, 03:34:40 PM by maguromic »
“If you haven’t seen the future, you are not going fast enough”

Offline fredvance

  • FVANCE
  • Hero Member
  • *****
  • Posts: 2297
    • Vance and Forstall Racing
Re: Sway Bars
« Reply #1 on: February 16, 2009, 04:23:25 PM »
At least not on purpose. :-D
WORLDS FASTEST PRODUCTION MOTORCYCLE 213.470
Vance&Forstall Racing
WOS 2011 235+MPH
Engine by Knecum, Tuned by Johnny Cheese.
Sponsers Catalyst Composites, Johnny Cheese Perf, Knecum Racing Engines, Murray Headers, Carpenter Racing

McRat

  • Guest
Re: Sway Bars
« Reply #2 on: February 16, 2009, 05:29:14 PM »
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.

Offline interested bystander

  • Sr. Member
  • ****
  • Posts: 997
Re: Sway Bars
« Reply #3 on: February 17, 2009, 12:42:04 AM »
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?
5 mph in pit area (clothed)

Offline jl222

  • Hero Member
  • *****
  • Posts: 2955
Re: Sway Bars
« Reply #4 on: February 17, 2009, 09:29:53 PM »

  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

 

McRat

  • Guest
Re: Sway Bars
« Reply #5 on: February 18, 2009, 10:02:36 AM »
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.

Offline Bob Drury

  • Hero Member
  • *****
  • Posts: 2599
Re: Sway Bars
« Reply #6 on: February 18, 2009, 04:25:22 PM »
  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
Bob Drury

Offline VeeTwin

  • Full Member
  • ***
  • Posts: 53
Re: Sway Bars
« Reply #7 on: February 18, 2009, 05:55:08 PM »
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.

McRat

  • Guest
Re: Sway Bars
« Reply #8 on: February 18, 2009, 06:11:49 PM »
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. 

Offline Rex Schimmer

  • Hero Member
  • *****
  • Posts: 2625
  • Only time and money prevent completion!
Re: Sway Bars
« Reply #9 on: February 18, 2009, 06:31:51 PM »
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
Rex

Not much matters and the rest doesn't matter at all.

Offline Gwillard

  • Full Member
  • ***
  • Posts: 238
Re: Sway Bars
« Reply #10 on: February 18, 2009, 06:44:32 PM »
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.
Will weld for beer :cheers:

McRat

  • Guest
Re: Sway Bars
« Reply #11 on: February 18, 2009, 06:53:41 PM »
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.

McRat

  • Guest
Re: Sway Bars
« Reply #12 on: February 18, 2009, 07:20:25 PM »
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.
« Last Edit: February 18, 2009, 07:23:09 PM by McRat »

Offline John Burk

  • Sr. Member
  • ****
  • Posts: 695
Re: Sway Bars
« Reply #13 on: February 18, 2009, 09:30:11 PM »
With a straight front or rear axel and a split wishbone or hairpins the axle becomes a very stiff anti-roll bar .


 

Offline jl222

  • Hero Member
  • *****
  • Posts: 2955
Re: Sway Bars
« Reply #14 on: February 18, 2009, 11:03:12 PM »

  You guys with heavy springs ''have fun spinning your wheels''

     JL222 :-D