I'm glad you have such high credentials. Could you divulge into the mechanical concepts that justify this? Why would we want to restrict the placement of the rear roll center when we don't have to? The rulebook isn't limiting us?I see no reason to couple the front and rear roll centers in anyway. Providing optimal slip angles for the intended configuration doesn't require us to limit our adjustability.. I'll let Chad Knaus and Chip know they might as well weld up those adjustable mounts. Is their an optimal position for a particular slip coefficient? Sure. Does it change constantly? Sure.I'll take adjustability.
You are taking an orange and comparing it to an apple. Us dirt racers don't run 500 miles in a single run. They don't have time to changes like we do in between runs. NASCAR pit stops are around 15 seconds. Its very hard to make changes to other components in a timely manner. So they are very limited on changes they can make to improve handling. Air pressure adjustments, spring rubbers, and track bar movement is about all the "quick" adjustments they can make. Adding/removing wedge, shock changes, adding ballast, etc. all take too long. Like i stated above, you can't compare an orange to an apple and expect it to be the same. Both fruit, both spherical in shape, both completely different.
I'll just agree to disagree. I'll select adjustability. You won't see any non adjustable mounts on my panhard bar anytime soon unless the rules require. Apparently your racing somewhere I know nothing about.
I run a mod with a rules package similar to an imca sport mod, solid pullbar, panhard bar behind rear end. Contrary to everything I've read, when I raise the bar on the frame (left side mounted) it tightens the car. My rear housing bracket is not adjustable, but I'm going to change that and see if I can gain anything from it. I don't think you can ever have too much adjustability in a race car.
Well still no one has answered my question directly. Is this one of those that it affects every car differently there is no right or wrong answer and that's why you see so many answers saying the same adjustment did the opposite?
Well still no one has answered my question directly. Is this one of those that it affects every car differently there is no right or wrong answer and that's why you see so many answers saying the same adjustment did the opposite?
There is no one right answer. As there isn't for most things in the chassis tuning world. Raising the j bar on the frame will tighten your car if it isn't too high already.
I have checked several setup adjustment guides and they all say raising it will loosen the car. The same could be said for just raising the frame side as this Will raise the roll center slightly. That is my thinking on it.
I have checked several setup adjustment guides and they all say raising it will loosen the car. The same could be said for just raising the frame side as this Will raise the roll center slightly. That is my thinking on it.
Raising on frame only affects average height and angle. Those two things are having opposite effects. That is why it gets tricky.
raising the frame only will tighten the car due to the angle has a short sweeping angle thus pulling the rearend to the left and under the car more almost the same as moving the wheel offsets to the left more
roll center height and it's relationship to the center of gravity of the race car. Lower the J bar will lengthen this relationship and raising will shorten. That is why most say to raise the bar to loosen entry and lower to tighten entry. Most believe that the j-bar relationship is for mid corner handling changes, per the afco tuning guide. The roll axis relationship of the placement of the front and rear roll centers is important. If the roll center on the front of the car is lower than the rear then forces acting upon the center of gravity and the roll center up front are greater than out back. There is a whole bunch of stuff that is going on. Whole bunch because you have dynamic forces changing with the application of throttle/brakes. Think about the center of gravity of your race car and the placement of these roll centers. The center of gravity will be around cam height. That's why placing weight above or below the center of gravity matters. As to the J-bar excessive angle. Excessive angle can loosen because when the center of gravity move vertically the resistive forces may not be enough *traction of the tires* creating a loose condition. You can only create leverage with resistance............hence you need traction to get up on the bars.
Hey Anonymous 24… you brought up 'wedge'…. I haven't heard that in years. Makes me want to go get my 5/8" socket and my floor jack so I can adjust the car for the feature (another old term).
[QUOTE=Krooser;1812067]Time for a snack…Hey Anonymous 24… you brought up 'wedge'…. I haven't heard that in years. Makes me want to go get my 5/8" socket and my floor jack so I can adjust the car for the feature (another old term).[/QUOTyes wedge.....that tells ya how long i have been doing this
That's how i do mine. Set ride heights, jack up in center of rear end and measure how much rr comes off ground before lr, i have that measurement wrote down. Of course i put car on scales every four or five races to be sure. Works for me. JMO
I only add wedge at the track if needed. All tracks have their own setup and that work is done at the shop. Rarely I put wedge in it. I prefer to hang ballast for the feature. That is if any adjustment is needed to be made.
Last year I spoke to a new 'driver' who was bemoaning the high cost of going racing… his Dad had just bought a tractor and 53' stacker trailer but they hadn't started racing yet because they were waiting to be able to buy $3,000.00 wireless scales...
Last year I spoke to a new 'driver' who was bemoaning the high cost of going racing… his Dad had just bought a tractor and 53' stacker trailer but they hadn't started racing yet because they were waiting to be able to buy $3,000.00 wireless scales...
I am an old fart. I have been known to use a jack and a socket. I agree on the cost of racing, but I have yet to see a stacker trailer win a race. I love these so called racers who have never raced before, that have their T-shirts, window stickers, and wrap on their car before they ever get an engine. Ive raced for 37 years, and I have never had a window sticker. I must be going about it the wrong way.
Wedge is for asphalt, Bite is for dirt, I consult with a lot of both, Nascar Cup cars are on bumpstops, the lower series are on coilbind setups, when your on packers and stops a lot of times the easiest adjustment is a panhard bar there are to many variables and temp changes, weather conditions or maybe you missed the setup, there are many times I'd love to change something in the race on a dirt car because my LR TO RR balance isn't right, If you wanna put yourself in a box and say never change something go ahead, it will eventually bite you so its best to know how it works right? You need to understand rake and how your arc moving effects how your body moves in relationship to your rear end, Raising both ends of any rear track bar j bar front or rear mounted will raise your roll center and free up the car on a left side frame mounted J bar, Raising your frame side will lower roll center and tighten car, raising pinion side will raise roll center and free up car. If your on and other setup then a Left side frame Jbar post it and we can tell you how it works. But any panhard bar you need to know the rake (mounting bolts to ground) and just pay attention to your overall height. on anything other then a jbar where its mounted on the tube changes week to week so what Anonymous24 tries to sound informed about doesn't hold water I work on the cars it all depends on asphalt what your trying to do with rear steer what your bumpstop package is and what your rules package is just like on dirt you can change your effective bar length to change your reaction speed, or move it closer to one tube and change loadings and rear steer properties. KNOW HOW IT WORKS as fast as your tire loadings and adjust to the driver don't get wrapped up in numbers and put yourself in a box understand how it works the rest doesn't matter as long as it works if you need a general baseline most people in here will help Mastersbilt know his stuff!
Originally Posted by let-r-eat
Senior Member
I am an old fart. I have been known to use a jack and a socket. I agree on the cost of racing, but I have yet to see a stacker trailer win a race. I love these so called racers who have never raced before, that have their T-shirts, window stickers, and wrap on their car before they ever get an engine. Ive raced for 37 years, and I have never had a window sticker. I must be going about it the wrong way.
Reply With Quote
Posting Permissions
Bookmarks