JIM73240Z Posted February 21, 2009 Share Posted February 21, 2009 OK. I'm trying to picture this. Only one side is adjustable, correct? So you fix one side in a position and then adjust the other side. To me, this would make the car handle different depending on which way you turn. Am i missing something? Jimbo Quote Link to comment Share on other sites More sharing options...
drmiller100 Posted February 21, 2009 Share Posted February 21, 2009 Loosening anti-roll bar end links delays when the anti-roll bar starts working and allows more initial and overall roll. It can also create asymmetry into anti-roll reaction. . That is kind of the point to having ANY adjustable sway bar. It changes the handling behaviour of the car. For sure it isn't the same as changing the roll center, but changing the roll center is a lot of work. Quote Link to comment Share on other sites More sharing options...
johnc Posted February 21, 2009 Share Posted February 21, 2009 OK. I'm trying to picture this. Only one side is adjustable, correct? So you fix one side in a position and then adjust the other side. To me, this would make the car handle different depending on which way you turn. Am i missing something? Yes. An anti-roll bar is a spring, just like a coil spring. It doesn't matter which end of the spring you push or pull on, you get the same force in reaction to the push or pull (Newton's 3rd Law of Motion). An anti-roll bar is a spring with one virtual lever arm which is the combined length of both physical arms. Quote Link to comment Share on other sites More sharing options...
tube80z Posted February 21, 2009 Share Posted February 21, 2009 For sure it isn't the same as changing the roll center, but changing the roll center is a lot of work. Actually it is quite easy. Just change the ride height. I often do this before messing with the bars. Cary Quote Link to comment Share on other sites More sharing options...
thehelix112 Posted February 21, 2009 Share Posted February 21, 2009 That is kind of the point to having ANY adjustable sway bar. It changes the handling behaviour of the car. For sure it isn't the same as changing the roll center, but changing the roll center is a lot of work. I think John's point might have been that its not the same as changing the rate of the bar. Lets say the reaction force for can be defined by: F = bx Where x is the vertical movement, and b is the rate of the bar. What I think loosening the end links does is effectively provide reduced reaction for small values of x, which is effectively the same as: F = b(x-y) Where y is the distance the endlinks can move before the bar itself is made to deflect. Somewhat of a gross oversimplification, if its even moderately accurate that is? Regardless, changing b, and changing x, you'd think would do quite different things to the way the car behaves, and something to be aware of. Dave Quote Link to comment Share on other sites More sharing options...
JIM73240Z Posted February 22, 2009 Share Posted February 22, 2009 HPR has them on their site with pics (blade type) http://www.hrpworld.com/index.cfm?tpc=Genesis_Technologies_Cockpit_Adjustable_Sway_Bar_Kits&form_prod_id=217,212_1432&action=product. These are 1100 to 1500 per bar. I wasn't able to find a good pic of the type John mentioned but if you take a look at http://www.gurneyflap.com/Resources/BRABHAMBT28-2124.jpg you'll see a manual slider arrangement. The adjustable models hooked a cable to the slider to move it and used a pin in channel typically to keep it from rotating. An easier way to build your own is to use square arms (1.5x.5 tube) and put a roller bearing on top and bottom. This is held by a simple flat bracket on both sides with the cable adjuster actuating it. This can be done with simple cut and weld tools and makes a lighter piece overall. I first saw these on the IMSA GTU And as you can see if you have the setup really close only one side needs to be adjusted, not necessarily both. OK, I see the manual adjuster. Thats fine for me I guess, but if you hook up a cable to it, I can see the pulling of the adjuster but not the pushing part. I guess I am picturing a bike cable or something. Maybe its more than that and I have not seen it. jimbo Quote Link to comment Share on other sites More sharing options...
drmiller100 Posted February 23, 2009 Share Posted February 23, 2009 Actually it is quite easy. Just change the ride height. I often do this before messing with the bars. Cary if you can lower the car, why in the world would you run it any higher then you have to, unless you are drag racing????? Lowering the car doesn't usually change roll couple distribution very much. Quote Link to comment Share on other sites More sharing options...
drmiller100 Posted February 23, 2009 Share Posted February 23, 2009 I think John's point might have been that its not the same as changing the rate of the bar. Lets say the reaction force for can be defined by: F = bx Where x is the vertical movement, and b is the rate of the bar. What I think loosening the end links does is effectively provide reduced reaction for small values of x, which is effectively the same as: F = b(x-y) Where y is the distance the endlinks can move before the bar itself is made to deflect. Somewhat of a gross oversimplification, if its even moderately accurate that is? Regardless, changing b, and changing x, you'd think would do quite different things to the way the car behaves, and something to be aware of. Dave so we are assuming the sway bar is used to tune steady state cornering, right? Sway bars pretty much suck for tuning transitions anyway, unless we are doing something like changing spring rates or roll centers and "fixing" results with swaybars. so, on steady state, we can assume the car is fully leaned over, suspension is leaning pretty much as much as it can. If in the middle of the corner we could run out and loosen up the swaybar links, you can see it will change over/under steer characteristics. likewise, if we could run out and physically change the sway bar and tighten the links, we could get the same results. Likewise, if we could change the contact points on the endlinks, same results. Quote Link to comment Share on other sites More sharing options...
tube80z Posted February 23, 2009 Share Posted February 23, 2009 if you can lower the car, why in the world would you run it any higher then you have to, unless you are drag racing????? Lowering the car doesn't usually change roll couple distribution very much. What I'm talking about is changing rake, and it's really not that large of a ride height change but it does change the lateral load distribution. This is a very effective means of chasing balance that doesn't rely on lowering the grip of one end of the car. And there are times you may want to raise the car. If it's cold and you can't build enough heat into the tires would be one example. A one inch change in IC locations will add around 40 to 50 degrees of tire temp. Cary Quote Link to comment Share on other sites More sharing options...
260DET Posted February 23, 2009 Share Posted February 23, 2009 What I'm talking about is changing rake, and it's really not that large of a ride height change but it does change the lateral load distribution. This is a very effective means of chasing balance that doesn't rely on lowering the grip of one end of the car. And there are times you may want to raise the car. If it's cold and you can't build enough heat into the tires would be one example. A one inch change in IC locations will add around 40 to 50 degrees of tire temp. Cary Yeh and by changing rake you change the aero too, it really is an often neglected tuning tool. Quote Link to comment Share on other sites More sharing options...
drmiller100 Posted February 26, 2009 Share Posted February 26, 2009 And there are times you may want to raise the car. If it's cold and you can't build enough heat into the tires would be one example. A one inch change in IC locations will add around 40 to 50 degrees of tire temp. Cary I've never had tires that were too big. What is it like???? I've never had too much grip either. how come you couldn't just lower tire pressures? When you raise the car on either or both ends, you lower the overall grip of the car. If you adjust the sway bar, it is possible to move grip from one end of the car to the other without losing overall grip in the car. Besides all that, raising the car up doesn't move the rollcenter of the suspension. If it does, you have much bigger problems. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted February 26, 2009 Share Posted February 26, 2009 When you raise the car on either or both ends, you lower the overall grip of the car. If you adjust the sway bar, it is possible to move grip from one end of the car to the other without losing overall grip in the car. Raising the car ALWAYS lowers grip? You're sure about that? You don't think that raising the roll center 1/4" or 1/2" might have a different effect if the car was unbalanced before you did it? You don't suppose that raising the roll center has any effect on the roll resistance of that end of the car? You don't suppose that increasing roll resistance on one end might change the balance? Is it impossible that raising both ends works the tires harder? None of the above is true??? I'm not even touching on the myriad other reasons why raising the car might make it handle better, probably the biggest one for Z car is because the car is driving around on the bumpstops before it was raised, but there are others, bumpsteer curve, camber curve, caster curve, etc. Besides all that, raising the car up doesn't move the rollcenter of the suspension. If it does, you have much bigger problems. Check the diagram on p2 against your roll center ideas. Lowering the car CLEARLY lowers the roll center on strut suspension. So then what does raising the car do??? http://www.banningcohen.com/buick/handling/documents/making%20it%20stick%20-%20suspension%20tuning%20guide.pdf Quote Link to comment Share on other sites More sharing options...
drmiller100 Posted February 26, 2009 Share Posted February 26, 2009 the diagram shown is not a real car. even if it was, the CG is moving the same amount as the IC, so the RC will not be changed. However the CG going up will cause more weight to be transferred to the outside tire, reducing overall grip of the car. A lower CG is always better then a higher CG, except in dirt or snow racing, and maybe in rain if you can't change tire sizes. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted February 26, 2009 Share Posted February 26, 2009 Roll center is not defined by the center of gravity. As shown in the diagram, it is a relationship between the strut top, the ball joint, the lower control arm pivot, and the center of the contact patch. The center of gravity has nothing to do with it. Many lowered Z cars have their roll centers underground. That doesn't mean the CG is underground. Look at the diagram again. If you think the CG moves as much as the IC, then we have reached an impasse that I can't talk you through. You are right about the weight transfer, but that isn't always the biggest priority. If you can't get any heat in the tires (at a cold autox in OR for example), perhaps getting heat in the tires would be a bigger priority in some cases. I'm starting to think that your posts aren't serious. Are you a troll? http://en.wikipedia.org/wiki/Internet_troll Quote Link to comment Share on other sites More sharing options...
thehelix112 Posted February 26, 2009 Share Posted February 26, 2009 I keep singing in my head: You've gotta pay the troll-toll to get into the little boy's soul. You've gotta pay the troll-toll to get in! Dave Quote Link to comment Share on other sites More sharing options...
Mikelly Posted February 27, 2009 Author Share Posted February 27, 2009 drmiller, I've read several of your posts, and I keep waiting for the heavy (very heavy) hand of the admin staff to come down on you... Regardless where else you post, please try not to post any further in my threads. I post so little these days, and I can't afford to get any dumber reading your disertations. Thanks! Mike Kelly Quote Link to comment Share on other sites More sharing options...
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