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CHECKING AND SETTING WEDGE/CROSSWEIGHT WITHOUT USING SCALES


tricknology

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CHECKING AND SETTING WEDGE/CROSSWEIGHT WITHOUT USING SCALES

 

From,,,,

 

http://www.mstrc.com/index.php?showtopic=5646

 

CHECKING AND SETTING WEDGE/CROSSWEIGHT WITHOUT USING SCALES

 

You will need;

Floor jack

Tape Measure

1 1/8 to 1 ½ inch shallow socket

A level piece of pavement

 

This is done with the driver OUT of the car.

 

Put the car on a level piece of pavement with the front wheels pointed straight ahead, Not turned.

 

Place the Socket on center of the pad of your floor jack with the ½ `` square drive pointed UP.

 

From the Back of the car, roll the floor jack under the rear axle until the socket lines up with the CENTER of the rear axel. The socket is to act as a pivot under the rear axel.

 

Carefully and Slowly jack up the rear axle, IF you have wedge/crossweight the right rear wheel will lift off the ground FIRST because it has LESS weight on it,

Then continue jacking until the LEFT rear just clears the ground and spins freely.

 

STOP.

 

Now you will measure and calculate your wedge.

Both rear wheels will now be off the ground, but the Right rear will be much higher off the ground. This is positive wedge.

NOTE: If your car has the opposite condition ( LR higher than the RR ) you have Negative wedge ( a Bad thing that causes a very loose car)

 

Go to the RR wheel.

 

Using your Tape measure, place the Tang at the 12 O’clock position of the RIM bead and extend the body of the tape measure straight down to the ground in a straight line.

 

Now READ the tape measurement, you do not have to compensate for the length of the body of the tape, just read it direct as you see it.

 

Record that measurement.

 

Go to the LR wheel.

 

Using your Tape measure, place the Tang at the 12 O’clock position of the RIM bead and extend the body of the tape measure straight down to the ground in a straight line.

 

Now READ the tape measurement, you do not have to compensate for the length of the body of the tape,

Because you are going to calculate the difference in height from right to left.

Just read it direct as you see it.

 

Record that measurement.

 

Subtract the LR form the RR.

 

That dimension is your wedge in INCHES, (not in % or pounds).

 

Most street stocks run 5 to 8 inches of positive wedge.

 

More inches of wedge = more crossweight.

 

More wedge = tight

 

Less wedge = loose.

 

Whenever you change tires, tire pressures, sway bar pre-load, springs, or move lead around, re-check your wedge this way.

 

Always check your wedge after every heat race and AFTER every feature race and record all your measurements.

 

 

PS> it turns out that for most street stocks for every inch of wedge ( Plus or minus 1/4 inch ) = 1 % of crossweight.

 

Sooo...for some cars every 3/4 "" = 1% for other cars every 1 1/4 ''" = 1 % of crossweight.

 

Measure IT before and after EVERY RACE.

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This technique was used by racers back in the 60's and 70's before scales were invented.. LOL...

 

I got real hi-tech back in the early 70's and used a torque wrench to "weigh" each corner of the car at the wheel. A bit complicated and you needed to know the total weight of the car (we'd use the public scales at the SA stockyards) in order to get the proportion of that weight correct for each wheel.

 

I miss the good old days.. LOL

 

Nick

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believe it or not i still see this method used regularly by many even those with scales good practice to use with or without scales was practiced many times on the 44 hobby stock in kyle last few years but only late at night with no one around dont want people thinking i was crazy especially with a set of scales normally sitting right there or fresh off the scales

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From Bob.....

 

"" We used to do the same thing 40 years ago, BUT we used a deep socket and layed the socket on its side - with the half-inch square facing forward or backward - so the socket acted as a true pivot point for the axle to roll around.

""

 

Well I tried this too, and with a GM 10 bolt rear, the car kept rolling off the socket, almost causing damage to my fuel cell and me.... I think the laying the socket on its side will work better with a Ford nine inch, which have a relatively flat bottom. The GM 10 bolt has a relatively rounded bottom so the axel will pivot on flat end of the socket.

 

So maybe get a short piece of 2 X 2 or bigger angle iron, lay it on the jack pad so that the peak is pointed up, it will look like an inverted “ V “ when you look at it from the back of the car. This may work with a GM 10 bolt rear. Try it and see.

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Hey Nick Seems i was told that if you run at say 56% left side weight that you go 56% from the RR axel flange and jack the car up from there. Then both rear tires should should come off the ground evenly and give you a balanced set up for any track? He! He! See you on the 7th. Got to go work on Bruce's car!!!

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  • 2 weeks later...

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