J-Bar Theory

[billetbirdcage]

Billet I have a theory on your Lakeside hammer down track experience.
In following my theory that more j-bar angle tightens "entry" and frees "exit" we should really stop using those terms in quotes because the car doesn't know where it is on the race track. It only knows if it is decelerationg or accelerating or turning and which direction the weight is transferring based on that.

So I'm wondering if (in those hammer down conditions) you were dealing with a "tight on entry while on throttle" condition which leads us to the same logic of stiffening the LF instead of softening to free entry. Am I making sense?

"Entry, middle, or Exit: To me these has 2 meanings/locations depending on who or when someone is describing them. I'm guilty as anyone using them both ways, but I typically use them in context.

Entry: can be the physical location on the track like turn 1 to the middle of both turns or the place which the car is decelerating/out of throttle.

Middle physical middle of turn 1 and 2, or the place the driver picks up throttle

Exit: physical out of turn 2 or the place past after which he's been in the throttle a while.

Obviously if never lifting there really is only the physical places and not 2 meanings.

Yes, I understand what you mean by reverse adjustment effecting entry because your not lifting and there really isn't an entry. However with the Lakeside case, while I said hammer down you was still lifting for brief second to rotate the car (sorry that wasn't probably clear).

However I'm NOT a believer in the "that more j-bar angle tightens entry and frees exit. Not saying I'm right and your wrong or vice versa, but as a general statement not something I agree with 100% in my experience. The crate was tight in the physical middle of the corner (not lifting) so your theory could explain that, but with the lake side it turned better upon brief off throttle and when he picked up the throttle. So, that doesn't really follow that theory and one could say it should have make the brief off throttle worse.

A person could make a ton of legitimate arguments as to why it did that or to why it's misinterpreted and I'm not here to argue but just state that sometimes things don't always follow a rule for whatever reason.

[Matt49]

I'm not here to argue but just state that sometimes things don't always follow a rule for whatever reason.

Ain't that the truth. Good stuff though.
For such a simple thing (a single piece of suspension connecting a beam axle to a chassis), it sure does things that don't make a lot of sense. It's so simple that it's complicated.

[Austin34471]

Ain't that the truth. Good stuff though.
For such a simple thing (a single piece of suspension connecting a beam axle to a chassis), it sure does things that don't make a lot of sense. It's so simple that it's complicated.

It’s original purpose is very simple, but us dirt racers like to use suspension parts to do things they were never intended to do... we use the jbar to jack the left side a mile in the air, move the rearend a half of a foot back to the left to negate the rear steer added by the 4 bar setup, which changes the CoG, track alignment, dynamic spring rates, anti roll and squat values for the back, etc etc. I’m usually pretty good at explaining what 15 things happen when you make one adjustment, but Billet is better at explaining what actually happens to the car.. cause it’s hard to know how many of those 15 things are contributing to making the car handle one way or another. Only way to really know is test it and find out, something Billet has done more than everyone on this thread combined. Lol

[fastford]

more than any one on this thread combined ? thats saying a lot billet , what say you?????

[Burke1118]

good info guys, thanks those taking the time to give you're opinions

[Jim11h]

Billet, have you thought that maybe you was already at max adjustment for desired effect and went more which can (usually does) give opposite effect? Seems to me where you was at and effectively learned how to use as tuning device where other folks it throws them and they start chasing their tail

[fastford]

i had a driver that used the rear brakes to get in the turn , raised the j bar 2 inches on frame , he could still get in pretty good , but he could drive off the corner on the right rear liker a bullet , this fit his driving style better than a driver that likes to keep the car straighter in and through the turn , point is , sometimes you have to go against the norm to find a balance between driver , car and track.....i also use to think there was nothing better than a short strait bar , that was before all this soft rt frt stuff ,

[billetbirdcage]

more than any one on this thread combined ? thats saying a lot billet , what say you?????

While there is no way to say for sure, I'd be willing to bet yes by a large margin. I've done tons of private tests for the last 12-13 years with several racers and at times that can get upwards of 20 times a year. This isn't including open practices nights at a track as I don't generally accept them as gathering good data.

Not a 100% if Austin meant total hours testing or all the different types of stuff I've tested over the years.

[Matt49]

A little off topic but along the same thread of thinking about j-bar...
Has anybody thought about or experimented with some type of tether system for the rear end as a safety net in the event the j-bar (or something holding it on) breaks. Not sure if any of you have ever broken a j-bar but suffice to say that the j-bar isn't the only thing you'll be replacing if you ever do. The shocks and birdcages are usually going to end up destroyed. It seems like some sort of tether system could be easily developed to "save" some of this additional damage and potentially increase safety. I was sitting still the time mine broke (got hit square in the LR while at a complete stop sideways) but breaking one at speed in the corner could get ugly.
I think it's something to consider. I've thought of putting tabs on the rear frame rails some sort of mounting mechanism above the center of the rear end and then just using some old harness belts. The belts being adjustable would make it sort of a universal design. Thoughts?

[billetbirdcage]

Billet, have you thought that maybe you was already at max adjustment for desired effect and went more which can (usually does) give opposite effect? Seems to me where you was at and effectively learned how to use as tuning device where other folks it throws them and they start chasing their tail

Sure it can happen, but in these instances typically doing that adjustment would not loosen them up. It's on of those deals where it's situational and a lot of it is based on experience with it and knowing the drivers/cars well from being with them for a long time. Now if every time I got over that certain point it did that, then I would agree but that wasn't the case here.

The experience I'm talking about isn't all that different then knowing/guessing from experience when to do 4 soft tires, 3 soft and 1 hard, or left soft and right hard. While not exactly the same, sometimes you just know or base what is gonna work the best off experience. Like knowing that the soft tires tonight isn't gonna work as well as it typically does and they are gonna give up.

[billetbirdcage]

A little off topic but along the same thread of thinking about j-bar...
Has anybody thought about or experimented with some type of tether system for the rear end as a safety net in the event the j-bar (or something holding it on) breaks. Not sure if any of you have ever broken a j-bar but suffice to say that the j-bar isn't the only thing you'll be replacing if you ever do. The shocks and birdcages are usually going to end up destroyed. It seems like some sort of tether system could be easily developed to "save" some of this additional damage and potentially increase safety. I was sitting still the time mine broke (got hit square in the LR while at a complete stop sideways) but breaking one at speed in the corner could get ugly.
I think it's something to consider. I've thought of putting tabs on the rear frame rails some sort of mounting mechanism above the center of the rear end and then just using some old harness belts. The belts being adjustable would make it sort of a universal design. Thoughts?

The drive shaft as it gets into the tunnel/(not a nice word)(not a nice word)(not a nice word)(not a nice word)pit or when the RR tire hits the 4 link bracket or frame, is our safety stops, lol

Not saying it isn't a good idea but what about back ups for other things? I've torn up way more when the torque arm or 6th coil chain breaks, so where do you stop on back up's?

[Matt49]

The drive shaft as it gets into the tunnel/(not a nice word)(not a nice word)(not a nice word)(not a nice word)pit or when the RR tire hits the 4 link bracket or frame, is our safety stops, lol

Not saying it isn't a good idea but what about back ups for other things? I've torn up way more when the torque arm or 6th coil chain breaks, so where do you stop on back up's?

Billet, I realize you're kind of playing devil's advocate (maybe not) but if NOT destroying the drive shaft is the outcome of a tether system, it kind of supports my point. I just look at single points of failure and try to think of ways I can limit the damage if/when those failures occur. Obviously routine maintenance is our best friend but things do fail outside of what a small team can reasonably quality control. With a failure like I'm describing, you're obviously out of the race, but if you can salvage some form of financial losses and/or increase safety, it has to be worth evaluating, right?

Love this discussion by the way. 4m tech section has been lacking these in the past few months.

[95shaw]

Billet, I realize you're kind of playing devil's advocate (maybe not) but if NOT destroying the drive shaft is the outcome of a tether system, it kind of supports my point. I just look at single points of failure and try to think of ways I can limit the damage if/when those failures occur. Obviously routine maintenance is our best friend but things do fail outside of what a small team can reasonably quality control. With a failure like I'm describing, you're obviously out of the race, but if you can salvage some form of financial losses and/or increase safety, it has to be worth evaluating, right?

Love this discussion by the way. 4m tech section has been lacking these in the past few months.

Are we thinking of creating another tether which can be morphed by someone into a tuning device?
My other concern would be that we are simply moving the stress points when the failure occurs.


Thoughts?

[billetbirdcage]

Are we thinking of creating another tether which can be morphed by someone into a tuning device?
My other concern would be that we are simply moving the stress points when the failure occurs.


Thoughts?

You mean like the bungee cord type chains/limiters guys are using now? Joking. . .

















or am I. Shrugs

[billetbirdcage]

Billet, I realize you're kind of playing devil's advocate (maybe not)

Yes, I’m playing devils advocate. My point was if you had a back up/safety for every item on the car, it might weigh 100# over weight or have so much stuff in the way it’s hard to work on or something else to get tangled and cause issues while racing. If you can do it without causing additional problems or things I listed for such a rare occurrence, absolutely nothing wrong with doing it.