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Author Topic:   forward bite
flywheel
Dirt Roller

Total posts: 9
posted November 08, 2002 09:28 PM
Trying to figure out how to get more heat in my left rear tire. Right rear heats up quite a bit. The car is pretty neutral, so its not like its loose. I was just thinking if I could get better contact patch, it might be better up off the the corner. Any suggestions would be greatly appreciated. The car is a leaf spring rear end weighing in around 3200 lbs. Thanks.

c21
Dirt Freak

Total posts: 346
posted November 11, 2002 10:14 AM
these 2 changes made (in proper purportion) can tighen up your exit without hurting the rest of the turn.

soften up your right front spring (or remove front sway bar if you are running one)and... add more static cross.

The additional static cross will plant your left rear better on exit while the softer RF spring will cause the car to loose less cross when transfering weight rearward (exit) and .....

the softer RF will also cause the car to gain less cross in roll (mid turn), but the additional static cross (used in the correct purportion) should compensate.

c21

hoganhomer
Dirt Full Roller

Total posts: 27
posted November 12, 2002 01:20 AM
If you soften the rf, and it gives you less cross through the middle that will help it turn better. Correct? (I think that is what you said) However, will that in turn take weight off the left rear when you apply the throttle? I'm confused about the front springs. Do they act the same as tire pressure on the front tires? I know that it effects the body roll, but does rolling over the rf help the car turn better through the center?

c21
Dirt Freak

Total posts: 346
posted November 12, 2002 10:45 AM
The wheel rate (which is proportional to spring rate) at a given corner reflects how much weight that corner accepts (or gives up) for a given amount of body roll (or pitch in the case of weight transferring forward during breaking and rearward during acceleration).

softening the RF forces the RR to accept a larger portion (relative to the portion accepted with the original RF in place) of the weight of the vehicle being transferred laterally in roll which will loosen the car up .... which is why I suggested increasing static cross to bring the middle turn behavior back to neutral.

At the same time ..... softening the RF will cause the RF corner to give up less loading (relative to the LF) during rearward pitch at exit which will translate into increased cross on exit and more loading on LR .

Dynamic cross needs to be considered separately from static cross. Static cross is what you see on the scales when there are no outside influences (aside from gravity) and is a good point of reference for set up.

Dynamic cross is what static cross becomes when: the car rolls over and is influenced by the difference between front and rear roll resistance ...
or: the car pitches (forward or rearward) and is influenced by the difference between left and right pitch resistance...

...but actually Dynamic cross is always (to some degree) influenced by varying amounts of BOTH pitch and roll resistance as you go through various parts of the turn.


In so far as your question about the change in loading on the LR ..... at the very least, the static cross should be reset to previous (although I did and do recommend adding additional static cross) .... therefore the loading will be the same (or greater) at static AND will increase on throttle (see above).

On your tire question, tires are springs and small changes affect wheel spring rate (lower pressure acts like a softer spring)while large changes affect both wheel spring weight AND sq. inches of rubber available for traction.

hope that helps,
c21

c21
Dirt Freak

Total posts: 346
posted November 12, 2002 03:53 PM
I wanted to make it clear (only because I didn't in my last post), that tire pressure and it's resulting affect on "true" wheel spring rate ..... is NOT considered part of the traditional "wheel spring rate" calculation.

What I should have said in my previous post in reference to the affect of changing tire pressure was something like..... " it changes EFFECTIVE wheel spring weight"

sorry about any confusion

c21

jammin
Dirt Administrator

Total posts: 5556
posted November 12, 2002 07:25 PM UIN: 16262997
Thanks for the good info c21.

jammin

flywheel
Dirt Roller

Total posts: 9
posted November 12, 2002 08:34 PM
Thats why we come here.

c21
Dirt Freak

Total posts: 346
posted November 13, 2002 11:02 AM
quote:
Originally posted by jammin:
Thanks for the good info c21.

jammin



Thank you Jammin .... for giving us a place to share and learn.


c21

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