?

It's useless for anything other than circle track and maybe drag racing.

It is done by adjusting springs and/or using spings that are stronger/weaker side to side. The purpose is to put more/less load on a wheel. This can help with handling and/or tire wear issues on circle tack cars.

This is one of the things you'll see happening durring NASCAR races when they jam a wrench in the rear quarter panels. (They could also be adjusting the panard rod angle...)

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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurasic Park)

The Ogre's Fiero Cave (It's also at the top of every forum page...)

like ogre said - it is useless for most people. most people have better options for adjusting the handling of their cars. NASCAR does this because the cars in a VERY controlled environment, and these slight adjustments are for the specific day/track/temp. there is NO WAY ON EARTH anyone would want to worry about this if they are going to making more than 2 turns during their drive. most people who turn in multiple directions & multiple radius's (radiai?) prefer to use adjustable coilovers to create the same effect.

yea you have to be careful with the camber and that too.... it can make your car pull in one direction regardless of your alignment.... most if not all nascars are setup for the turn.... that is that on the straight away there really turning the wheel more to the right to keep it straight and in the turn barely turning it because the car is already setup to take the corner properly... this is more previlant on big tracks like daytona and talledega... and im sure they have compensation devices that allow the driver to keep the wheel straight down the straight away... but without those camber adjustments those cars would never be able to take those corners at that speed... they'd simply push up into the wall.

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Actually I think NASCAR and most others use power steering now, which really cuts driver fatigue problems related to fighting the wheel.

You guys are making this way too complicated and mysterious. It's not. Let's start by defining the term. Weight jacking means adjusting corner weights. Corner weight means exactly what you think it does - park the car with each wheel on a scale and weigh each corner. The relative weights of the different corners affect how a car handles.

Adjusting corner weights is simple if you have adjustable ride height. Many cars have coil over shocks with threaded sleeves and adjustable spring perches. NASCAR Cup cars have the spring bucket mounted on the end of a large bolt that lets you vary its height. This is called a "weight jack," hence the term "weight jacking." Both setups function exactly the same way.

You can not change front/rear or left/right weight bias by adjusting corner weights. The only way to change this is by changing where mass is located in the car. What you can change are the diagonal weights. These are the Left Front + Right Rear, and the Right Front + Left Rear.

A car that turns both directions should have the diagonal weights equal. A car that only turns left will want some "wedge," meaning RF + LR > 50%. A rear drive solid axle drag car will probably want LF + RR > 50% to try to prevent the RR wheel from spinning on launch.

Simple enough?

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Doug Chase
Chase Race
Custom: cages, exhausts, fabrication
Duvall, WA
425-269-5636

[edited for grammar]

[This message has been edited by Doug Chase (edited 02-13-2006).]