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Author Topic:   c.g. in a mod whats too high?
LITTLEMAN
Member
posted February 13, 2002 09:33 PM
can a mods forward bite and side bite be improved by raising the c.g. of the basic design of the chassis to increase the c.g.has anyone ever done this ?to what extremes?by building the chassis purposely heavy on top won't that improve sidebite and forward bite? ?how much is too much ?what do ya think?


jammin
Administrator
posted February 13, 2002 10:10 PM
Thats a very good question. This is my thought. If you build a car to do this, you still have to have enough bite from the left rear to get you off the turns. I dont think there is a max other than getting off. If you build one to roll like this, your going to hinder it, so you have to maximize bite to allow you to exit properly. If you dont, you wont be anything come feature time when the track is slick. An example that comes to mind in relation to this is a latemodel with a locked left rear cage. It lifts on the left side soooo much that it will do this reguardless of the roll center or whatever roll you have setup in the car.

My Two Cents.

jammin


wfoondirt
Member
posted February 14, 2002 12:24 PM
A higher cg will help forward accel because of increased fore/aft weight transfer, but hurt cornering to to increased lateral weight transfer. I try to keep cgh @ 10-12 inches.


LITTLEMAN
Member
posted February 14, 2002 06:14 PM
wfoondirt, could the higher c.g.be counter acted by more leftside weight to take roll out of the car and make the car get back on the left rear faster,So it would get out of the corners faster and use the higher c.g. for more forward bite?I realize this ain't the norm for set-ups but I'm not one to go for the norm on my own car.I was thinking about using a steel deck and sail panels to get a higher c.g. using a flat 16 gallon cell up against the deck.


HEAVY DUTY
Member
posted February 14, 2002 09:50 PM
I think you would pay too great a penalty for the increase in overall weight. Its difficult to get alot of ls weight on a mod without adding additional weight to the car.
Like heavy was getting at the higher cg would be better counteracted with higher front and rear rc. But you will still pay a penalty in cornering due to the higher cg, which will probably offset the small gains in accel grip.
In my experience i have found more gains in lowering the cg than i have in raising it.


LITTLEMAN
Member
posted February 15, 2002 10:31 PM
wfoondirt,moving the left side tires in and the right side tires out would increase left side weight without increasing total weight.The theory of moving the rc closer to the c.g. won't aid overturning weight on to the right side tires and I was taught that makes sidebite.Your thoughts on a higher c.g. hurting cornering is why? because the right side tires would be overloaded or the left side tires would be unloaded?


wfoondirt
Member
posted February 18, 2002 09:00 AM
Lateral weight transfer increases grip of the right side tires, but its not proportional to the amount of grip lost on the left side tires. This results in less overall grip on that end of the car. But the increased grip of the right side tires can cover up a loose condition and make the car feel tighter to the driver. Its really a pretty popular beleif and is somewhat acceptable due to the short nature of most dirt races, but the increased weight on the right side tires become a wear issue in longer races. A dynamically well balanced car will show more even tire wear and perform better in longer races.

You are correct that moving the rc closer to the cgh increases roll resistance. I mentioned that earlier as a counteract to the increased roll due to raising the cg.

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