LegendsRacer - Legends & Bandolero Racing Forum
LEGENDS => Setup and Handling => Topic started by: GoneDirt on May 17, 2009, 09:21:27 pm
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I'm fairly new to the legends car and i run 3/8 dirt track, I am having issue's with being loose out of the corners to the point i either spin out or bounce off the wall, I have tried a hard and soft spring on the rr but it didn't effect exiting. I at a loss of what the adjust.
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What are you running for tire pressures and spring rates?
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Yep, what Jim asked. Also what cross weight are you running, it makes a huge difference with these cars? If you want consistent handling you must scale your car.
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P.M'ed,
Let me know if you need anything else,
Jim
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Thanks to every one for the input, made a few changes to the cross and tire pressures and had a good run, finished 4th out of 11.
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Sounds good, congratulations
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Congratulations!!!
Keep up the good work!
I told you there were awesome people here on the site!!!
Steve
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Can you guys share the info that you gave him? Tire pressures for dirt? RR with bead lock tire pressure? Cross? Can some one explain calculating bite?
Sent you a PM.
Calculating side bite:
The formula for lateral acceleration is LA=V2/32R
The formula for finding the amount of weight transfer is Transfer=W x CGH x G
TW
What the hell does that mean! ???
It has to with Lateral Acceleration and Weight Transfer.
Lateral acceleration is the sideways force which a car generates in a turn. It is a measurement of the maximum amount of cornering force a car will generate.
Lateral acceleration is dependant on two things: velocity (speed) and the radius of the turn.
Lateral Acceleration is the Velocity squared (expressed in feet per second) Divided by the Radius Of The Turn x (times) 32.
Example:
A race car is tested and found to corner at .85 G's. One G equals the weight of the car, so this means that the car's suspension system can corner hard enough to withstand a sideways force equaling 85% of the car's total weight and still maitain tire contact with the track. The more G's of lateral acceleration the car can produce under maximum cornering, the greater cornering power of the car.
A reasonable lateral acceleration for a Legends (or Dwarf) Car would be .85-G to 1.0-G for a paved track car, and .75-G to .85-G for a dirt car.
Once the later acceleration for a particular car set up is known, the actual pounds of weight a car is transferring from the inside wheels to the outside wheels during maximum cornering can be calculated.
There are three major factors which affect weight transfer: The car's weight, center of gravity height and it's track width. (See formula for finding weight transfer.)
In other words, the amount of weight transfer in pounds eqauls the car weight (expressed in pounds) times the center of gravity height (expressed in inches) times the lateral force coefficient (expressed in G's) all divided by the car's track width (expressed in inches).
References used for the above information come from the "Automotive Math Handbook" by Forbes Aird and "Dwarf Car Technology" by Steve Smith.
Check them out... Both are excellent books. Obviously, there is more information in the books. The "Dwarf Car Technology" book is easier to understand, and gives some practical use information.
You asked for the formula to calculate side bite.... So there you go. ;)
Have Fun!
Steve
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Wow, so how is that going to be usefull?
If you use teh basic setup provided by Steve Smith in his Dwarf car book you should be fine. I am not that far off his setup and am doing pretty good. I think far to many people try to out think these cars, you have limited adjustments so get the basics down and drive it like you stole it.
This is a setup that I posted in another post:
This setup worked for me at 1/4, 1/3, and 4/10 mile tracks flat and banked.
Springs:
185 200
165 145
50.0 - 51.0% cross weight
Tire Pressures:
9psi 14psi
9psi 14psi
You can swap the rear springs rates if you prefer a looser car.
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You can start between 50 and 51% cross weight and tire pressures around 9 on the left and 12 on the right. I have not used a beadlock yet, so someone else can probably tell you how much you can drop the right rear pressure. You can find good information on springs, rear offset, etc. by searching previous posts on here. My setup is a combination of what I learned on this site along with advice from some other legends racers. I only have one race in this car, so other people on this site can give you more detailed setup help based on their experience.
Bite is the amount of left rear weight compared to right rear weight. You want to get what you can to plant the left rear tire, but within the 52% left side weight rule.
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Jeff got to this before I did. Go with what he said in his post. He has a pretty good winning percentage this year.
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I think you are both right, most people tend to over think the whole situation. He wanted to know the formula, so I posted it (with a bit of explanation). ;D
The legends cars are a spec class... In that respect, as John stated, go with the basic set up that Jeff posted (He does have a good percentage of wins. Not only this year, but last year also). You can always adjust to your driving style and preferrence for the feel of the car. If you are building a car from the ground up (like I am), all those formulas come into play. I didn't start out with a pre-designed chassis. The info provided was meant as a "for what it's worth". Obviously, you can not modify the chassis of a Legends Car. John is also correct with his suggestions about rear percentages and cross weight. As for tire pressures; Start out with what Jeff suggested
Steve
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I was not trying to undermine what you stated Steve but I have seen too many new or inexperienced racers get themselves off coarse. As far as with the beadlock, you can lower air pressures all you want just remember that it will change the spring rate of your tire. I personally haven't lowered my RR tire pressure much.
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Jeff,
I didn't think you were trying to undermine what I posted. You are correct that sometimes people tend to get caught up in the math, or make it more complicated than it needs to be. Given that the Legends Cars are a factory spec chassis, the math is pretty much already done.
I think the set up that you posted would be a very good start for anyone. Thank You for sharing!
Steve
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Jeff, what ride heights would you use on a setup like that? I run paved tracks but have always wanted to try dirt.
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LF RF
4" 4-1/8"
LR RR
4-3/8" 4-1/2"
The biggest issue I have is keeping the RR tire from busting my fender when I hit the cushion. I used to run a little lower but I have raised it up a bit to try and save my fender and running board on teh right side. If your track is smooth and slick I would run what you do on asphalt.
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I just gotta say thanks to everyone on here....Thanks for all the posts! I have a bead lock and ran 9 lbs in it....on a real bumpy track too! But I don't think it helped to run quite that low....like stated it changes your spring rate in the tire....testing still in progress, I'll post more info as I get it.
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The thing with running to low of air pressure on the right rear with a bead lock is this..... the side wall flexes under way to much... then coming outa the corner it springs back out. Seams to make the cara bit loose coming out. Our tires are not created for dirt. If we were running hoosiers then it would be a different story. Still think the bead lock is a great piece of insurance policy though.... I hate driving 200 miles to blow a bead 2 laps into the feature then go home. Like Batzer said "testing still in progress".
Joe
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We raced on dirt for the first time in our legends Sat. We left one of my cars with asphalt set up the other we tried several setups we ended up with a pair of 150 on both sides of rear. Both cars with 2 diff. setups were loose fron apex to straight with no forward bite. What can be done are is this normal on dirt.
Thanks Joey
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Dirt cars tend to be loose. Lack of grip because of the spec tire. Read through some of the old threads on dirt set up, that should help you with ideas how to tighten your car up.
What track are you racing at? We have members from all over that may be able to help!
Welcome to the LegendsRacer Family! Good to have you aboard! I hope you enjoy the site.
Steve
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We raced @ Thunder valley speedway in Glenmora Louisiana. We also race asphalt @ Monroe motor speedway. If there is any racers in La are Tx that would like to race dirt we will be racing @ TVS agin in 3 weeks and need more cars to make it work. I am buying and selling legends in our area to help build the class I have a 37 sedan set for dirt real clean car new body 1250 sealed $6800
Thanks Joey
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Hi Joey,
Post what you have to sell in the For Sale section. You might also want to post a schedule and links to the speedways in our Track Announcement section.
We have a couple of guys that run at Monroe. As I am a pavement guy, Monroe looks like a very fun place! Talk Knuclebuster into joining in on the fun! ;)
Steve
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Joey,
Compared to pavement, on dirt you will not have much grip to work with coming out of the turns, especially on a dry slick track.
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Will adjusting pinon angle make any differance with it being a solid bar?
Joey
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is the ride height set with the driver in or out
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Do a search on this site for the pinion angle threads. There is a lot of good information on how to set them for dirt. The more pinion angle, the better.