Landracing Forum
Tech Information => Technical Discussion => Topic started by: DSR88 on March 07, 2010, 09:45:49 AM
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For those of you that scale there car, I am just wondering what would be a good front to rear % number ? Like a stock body car or an alt or comp coupe exc. This would be a Bonneville or El Mirage question.
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We race a rear-engined modified roadster at 3400#,currently 60% rear, 40% front with fuel and driver. The first thing we do at the Salt is put the car on the scales with the driver and check corner weights and ride heights (compare to set up in shop) after the 2200 miles "shakeout" trip from NCarolina. This also allows us to zero the shock pots for the data system. Some people look at us like we're nuts, but we've been doing racecars - road racing and oval track - this way for so long that I'd feel like I cheated the checklist if we didn't do it on the Salt. I have heard that shorter wheelbase cars like you mention want closer to 50/50, but you need to balance adding downforce and drag vs grip at the rear wheels. Trevor Harris once told me to exhaust all avenues of balancing a car mechanically first, then apply aerodynamic aids once you were out of mechanical solutions. I've followed this for the last 20+ years. I would start out at 55rear/45 front and rebalance as handling dictated; I hope that others here with more experience with your class vehicle will provide more proven solutions. vic
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Very good info,I was out in the shop scaling my open wheel modified and though did would be a good question. We run a comp coupe and we did scale our car on the salt in aug only because we ran out of time at the shop but you bring up a good point about doing it every time to to towing.That will go on our ck list now. Maybe we will get some more input on this.
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What is your current % and are you spinning your tires in high gear currently?
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I don’t know why more people don’t scale there cars on the salt for the exact reasons that Krusty mentioned.
Trevor Harris once told me to exhaust all avenues of balancing a car mechanically first, then apply aerodynamic aids once you were out of mechanical solutions. I've followed this for the last 20+ years.
Its like deja vu Trevor Harris recently told me the same thing. He is consulting on our chassis, and those are some words of wisdom from one of the iconic chassis designers in racing. Tony
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Hey Troy, Not have a problem in high gear,Just kinda looking the lower gears.I really was just wondering what other people were doing lust to come up with some sort of baseline. I think that is a good way to keep up with you car. Just think I you run your car for a couple of years and you have a suspension part froze up you would see it on scales.
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We have some slippage in 1st and 2nd gear, 3rd and 4th is not a problem. Once we put taller gears in we shouldn't have as much slipping in the lower gears. We are 65% rear, and DO NOT SPIN OUR TIRES IN HIGH GEAR. :-D. Good luck this year. :cheers:
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We have some slippage in 1st and 2nd gear, 3rd and 4th is not a problem. Once we put taller gears in we shouldn't have as much slipping in the lower gears. We are 65% rear, and DO NOT SPIN OUR TIRES IN HIGH GEAR. :-D. Good luck this year. :cheers:
Or 3rd gear :-D
JL222
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I run a rear eng Lakester that is set up mor like a rear eng roadster--I run 1/3 F 2/3 R with a SWAG slight bias on the RR and LF to offset eng and Drive line tq.
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Yes we scale the cars too.
The Vicky is 50/50 empty,,, add me and 8 gallons of gas and it's 52% Rear...48% front.
We plan on the Stude to be very close to that balance as a starting point. With the longer wheelbase,, may put 1 to 2 % more out back if need a bit more traction.
Charles
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I was wondering if any one aloud for enging TQ. Do you think that a spolier or a wing would over come that at high speed? That is a good point.
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A stude was the first car I ran on the salt as a c/gc, I had a great idea take all the ballest out and I could pick up the four mph I need to hit the 200mph mark.Not knowing any better that is how I got into the spin-out club!!!!!!Triped the 3 mile light with the back bumber @186. At that time I didn't even know what scales were. Good luck with your new car.Stude's are cool.
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My front drive streamliner is a static 90/10 , at speed 90/20 .
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:? . . . 90/20 is more than 100%. Not sure I follow your thinking, John. . Are you adding downforce? And how are you applying it to the rear and not the front?
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He's looking for vehicles such as stock bodies cars, altered or Comp Coupes. What salt fever you never gave 110% before? :-D :-D :-D
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I am interested in how you figure down force at speed. I know John's liner has the engine in front of the front axel and was wondering if there was something unique to that combination that was giving him an unusual number.
110% is fine if you are young or take little blue pills. :-D
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Yes aero downforce on the tail to overcome possible low pressure under the nose . In 5th gear maybe it's 95/20 .