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Post by ukblue on Jan 1, 2013 17:42:26 GMT -6
When you lower a j-bar it lowers rear roll center and tranfers weight to adds side bite or does it tighten the car . The reason i posted this i was told when you see a car rolled over on the right rear the weight is more on the the left rear then right rear that is way the car is tighter with a lower rear roll center also when you raise the roll center you loose roll and loosens car but the load is on the right rear . What are you guys thoughts on this UKBLUE
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Post by confused on Jan 1, 2013 18:25:41 GMT -6
The lowering of the roll center by lowering the j-bar tightens the car. This happens by allowing the weight to transfer over to the right side in an arc. The spring will compress to a point and then transfer the weight(energy) to the right side tires. If the j-bar is raised, the energy is transferred more laterialy and creates a shear force. Thus creating a loose condition. The spring converts the kinetic energy into thermal enrgy during compression. After the spring has compressed to a certian point, the kinetic enrgy is transferred to the tire contact patch. If the spring won't compress(high j-bar), the energy won't be transferred to the tire contact patch.
Hope this makes sense.
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Post by ukblue on Jan 1, 2013 20:10:32 GMT -6
I understand that i think what if the roll-center is high then you soften the rr spring alot can you still get side-bite thanks
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Post by confused on Jan 1, 2013 20:47:40 GMT -6
Softening the RR sping tends to loosen entry. What are you trying to achieve? Is the car tight or loose, or are you wanting to learn more about them?
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Post by ukblue on Jan 1, 2013 21:08:36 GMT -6
Just want to learn more where my problem is to me a lower rc or soft right rear spring does the same thing i under stand a stiffer right rear tighten the car on entry and a softer will loosen off the throttle i guess where i screw up at a lower rc tranfers weigh to right rear and a softer right rear does not but they are doing the samething. I run a pierce clamp car with a straight bar i have never ran a j-bar anyway.Thanks for your help
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Post by confused on Jan 1, 2013 21:53:21 GMT -6
The j-bar has a big influence on the center of the turn as well. More so than the spring. The spring controlls the tire and supports the car. The distance that the spring is from the tire also has an effect on how the car rolls over. There is way more to the rear suspension than just the roll center. J-bar/straight bar angle has a big effect as well.
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Post by clbaker25x on Jan 2, 2013 8:11:01 GMT -6
Right rear spring softer or stiffer will have different effects depending on if the driver is on the gas or not. If on the gas than softer spring tightens entry, if off the gas stiffer spring tightens entry. The opposite is true also if on the gas and need looser in you can stiffen the right rear spring to free the car up.
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Post by ukblue on Jan 2, 2013 12:05:11 GMT -6
25X AND Confused thanks for your replys i understand there is a limit to have stiff or soft you can go on the rr spring also i can also see a j-bar adds side bite but how can you get side-bite with a car with a straight pan-hard bar hooked the left side of pinion and the right rear spring on top of the rearend also with the right rear spring the top of the spring is higher in the car does this make a differce . thanks ukblue
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Post by clbaker25x on Jan 2, 2013 13:31:34 GMT -6
Here is my understanding of the panhard bar changes and effects. Overall lower bar gives car additional side bite and tightens car mainly on entry and throughout the corner. Adding angle to the bar will make the car tighter in and make it have more effect going putting pressure down on the rear end. A higher panhard bar location will free the car up, and high and flat will make the car really free.
We run a northern sportmod and run our panhard bar fairly low and flat. On a spring over the rearend setup I like a flat panhard bar better than an angled one because I think it reduces the tendency of the car to want to spit out rear springs. The rearend will move more to the left during roll the more angle is in the bar.
I have never ran a shorty bar in front of the rearend, but have ran both J-bars and panhard bar behind setups.
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Post by teamgrt12x on Jan 3, 2013 1:07:39 GMT -6
You can get to a point where you have too little angle, and be too low (thinking this will provide great side bite and still turn) but it is the exact opposite. We have to remember that the car turning in, to middle depends greatly on how it "scotches" up. I recommend a flatter J bar for big, sweeping tracks, and more angle for tracks that are stop and go, tight cornered where you really need to muscle the car. You are going to do much more for "free" and "tight" by moving your mounting location on the rear end side than you will on the chassis side. I've run as little as 3" and as much as 7" and prefer to start at 5" even with the pinion and go from there.
Like confused said, there is a lot more to it than roll center. I rarely ever put that into the equation when I'm diagnosing a problem. Rarely, once I get the panhard to my liking for the tracks I race, do I adjust it. There are times that the track will get really heavy and rough that I will pick the J bar up one hole on the pinion, but I also raise the right side lower one hole as well. Play with it sometime at a test and tune. Bury the J bar on the pinion and run some laps, with a stopwatch... then take it back to where you had it, and bury it from the frame side with a bunch of rake, and test again.
With what you are doing, you need to be around 2.5" Rake, maybe 3", one hole below pinion. We used to run this setup quite a bit on a 2 link. You can gain side bite in other areas, roll some index into the right rear spring if you are a 4 link. Pull the right rear tire in, drop the right lower one hole...
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Post by ukblue on Jan 3, 2013 4:42:06 GMT -6
With our straight bar we have about 28 degrees 14.5 inches long mounted center of pinon on 9in rear that how the car built older pierce one place to mount the straight bar it may have 7.5 rake that the basic set-up if i pulled the right rear in would that tighten the car off the corner or balance the bite out
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Post by flipflopoo1oo on Mar 5, 2014 18:59:55 GMT -6
With the set up of old school, lifting the gas, nosing the rt ft sends the weight to the left front as the cross changes and sends weight to the right rear instantly and lifting the left rear at the same time creating steer and in you go with right side weight in place just by lifting the throttle! And now as you are starting in and already steering left with side bite and already back in the gas, roll and more weight transfers! As per extreme caster is used, a right turn sends left rear to maintain left rear to reduce steer and equalize traction, to eliminate pushing, putting the cross back in place while holding rt ft down as frame lifts under acceleration first with soft shock as to stiffer left! All 4 stay planted with tension from springs keep the switching balance to max side bite ft and rear, holding the car on all 4s with higher a percent to right side and to rear traction! Drivable up or down while in the turn or coming off! Driver controllable to win!
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