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Author Topic:   Back to basics
mod777
Dirt Roller

Total posts: 23
posted March 24, 2005 09:16 AM  
Hello guys and gals,

Here is a basic question for you. Let's say:

A car is near the end of the straight, wide open throttle, and traveling perfectly straight(not all "jacked around" because of bars). If a person could at that instant weigh the car, both front tires would come in at, let's say 600 lbs. each. The rears would come in at 700 each (I am assuming a 2600 lb car, and we'll forget about downforce or uplift for now).
My question is, the instant I lift off the throttle, where does the weight need to "move" to, in order for the car to begin turning left *without* turning the steering wheel or applying brake? I just want it to begin "drifting" left as soon as I get out of the throttle.
I realize things like stagger, brake bias, coming down off the bars, and the fact that the car is transitioning from a mostly level surface to the banked corner would have an affect, but leave that out for now also.
I assume it would be either left front, or left rear, but which one?

Mike

dirtbuster
Dirt Forum Champ
Total posts: 2007
posted March 24, 2005 09:30 AM  
I would say LR. That way the car tries to pivot around that point and start turning into the corner. Thats the idea behind adding LR bite to free up entry.

NJantz
Dirt Forum Champ
Total posts: 755
posted March 24, 2005 12:45 PM  
Yep, I'd have to agree based on the fact that leftside weight/LR weight promotes corner entry.

[This message has been edited by NJantz (edited March 24, 2005).]

mod2_x
Dirt Full Roller

Total posts: 38
posted March 24, 2005 01:33 PM  
Will left rear weight also make the car loose entering the corner?

justin
Dirt Freak

Total posts: 263
posted March 24, 2005 02:05 PM  
Yes. With your LR heavier than the RR, your RR will want to pivot around it just as dirtbuster said.

Justin

Rat Trap
Dirt Maniac

Total posts: 129
posted March 24, 2005 03:10 PM  

Without knowing what the cross,rear and left side percentages are when its sitting down how would you know? I'm still learning but don't those percentages have a big impact on where the weight transfers when you let off the throttle at the end of the straight?

[This message has been edited by Rat Trap (edited March 24, 2005).]

dbradley
Dirt Freak

Total posts: 251
posted March 24, 2005 03:59 PM  
Hey guys,
Wouldn't you get nose drop at onset of deceleration increasing front percentage then your percentages would take over...If my mind is thinking right I would say evenly across initially then your spring/shocks would begin to distribute your percentages.
D

A2KY2K88
Dirt Maniac

Total posts: 141
posted March 24, 2005 07:21 PM  
Your gearing plays a big part of you slowing and turning. When you let off the throttle, your rear wheels will act as if you are applying the brakes due to the gearing and the decrease in RPM's due to compression of the motor. I hope that made sense, anyway, this will cause the rear of the car to want to come around. Yes the majority of the weight will shift to the front due to de-acceleration. As you start to turn left, the weight shifts to right front, then right rear. The car will have a tendency to turn better with more leftside weight. The simple answer to your question, if you want your car to turn into the turns better when you lift throttle, you need more left side weight.

sdracer12
Dirt Maniac

Total posts: 180
posted March 24, 2005 09:02 PM  
If your car is pretty flat or level, as you said, weight will transfer to the front of the car when you lift, and when you brake. The stiffer spring in the front will get more weight quicker. If you have an 800 spring in the RF, and a 700 in the LF, the right front will get more weight. More weight at the right front will keep more crossweight in the car. Crossweight and RF weight at turn entry will free up the car, and help it turn well. The opposite happens on turn exit/acceleration. Cross weight and LR bite tightens the car on exit.

So, to help the car start to turn by itself when you lift, the weight needs to go to the RF.

mod777
Dirt Roller

Total posts: 23
posted March 28, 2005 07:37 AM  
O.K.

So it looks like we need left rear to start the turn.(1 reply says right front, the rest are for left rear or left side)

Question 2 & 3:

(2)Does the weight then need to "move" to the right side to make it through the middle of the turn, and then..

(3) ... move back to the left rear to get off the turn properly?

No need to confuse the issue with *how* this should happen,(wedge,bite,stagger etc...) just *if* it should happen.

Mike

mod777
Dirt Roller

Total posts: 23
posted March 30, 2005 07:44 AM  
Anyone?

Kromulous
Dirt Forum Champ
Total posts: 796
posted March 30, 2005 10:34 AM  
Looks like to me your right, when you add LR weight it adds cross, cross to the right front. Basicly a teder toter and the RF & LR are the hinge.

If the right front cant do its job, of turning the car, all the LR weight in the world isnt going to matter.

I also believe rear steer is some what of a crutch, alot of people crank in loads of rear steer to get the car thru the corner, over looking the fact that if they could get the RF working better that wouldnt need all that rear steer.

Alot of rear steer, or to much can lead to the car being loose coming off, and never really have any drive up off the corner. Late models i seen run in the past weeks are starting to realize this and tuning them to come off straighter.

Also, i always percieved the desire to tuck the LR up under the car as being a way to get all the weight on the LR once you begin to exit the corner onto the straight.

Centrifical force, or momentum of the car will plant the RR, but the LR needs help. Because if you had zero bite in the LR and did not have it tucked up under the car you could take the wheel off the car because it wouldnt be doing anything, an exageration of course but its in essence true.

So all in all, i think you got it. I always try to remember the cause in affect deal, you crank in more rear steer thats great, it gets you thru the center good, but the price comes when you go to get up off that next corner and the rear keeps wanting to go to the wall and you have no real drive off.

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