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What is corner weighting
What is corner weighting, I see it all over the forum and I don't understand what it is. Also I have a Backdraft so please target your responses toward this vehicle. I live in North Jersey so who would do this or is it a easy DYI project.
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Corner weighting is putting each tire on a scale and trying to get the pressure on each tire the same or very close front to back. Because of the nature of coil over shock adjustment you can get it out of wack when adjusting the shocks pre-load and ride height.
A race shop locally would be able to help you. The scales are around a grand. |
It is adjusting all 4 corners of the car while on 4-corner scales to establish an even weight distribution front to rear and corner to corner. You should be in the car when it's done (or put your equivalent weight in drivers seat) and most guys do it with 1/2 tank of gas or so. Much debate on this site about it, but for me and many others it made a noticeable difference in handling.:cool:
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Here's the classical way of describing it for the non-technical. Imagine a four legged table on a flat floor with all four legs the exact same length. If the table weighs 40 pounds and the weight of the table is evenly distributed, the foot of each leg will be carrying 1/4th of the weight, or 10 pounds. Now imagine that you saw a quarter inch off the bottom of one leg. The table will rock back and forth between the short leg and the one opposite it, with most of the weight being carried by the other two legs. You might find, for example, that the short leg is carrying no weight, the one opposite it is carrying 8 pounds and the other two legs are carrying 16 pounds each.
If the distribution of weight in your car AND the suspension settings are not optimized, your tires may not be carrying equal weight. Thus, when near the limits of traction (e.g., hard acceleration, braking or cornering), a tire carrying lighter weight may break loose before another. This will happen sooner if the corner weights are not balanced, and it may cause the car to change direction (left or right spin). |
Just skip to the last post of this lengthy thread: http://www.clubcobra.com/forums/all-...ht-my-spf.html
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Thanks all now it makes sense. The chair legs did it for me. Any idea what a speed shop would charge to do this?
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Weight jacking
Just to clear this weight distribution thing, when adjusting 4 corners weight transfers in an X pattern. The following numbers are just examples. If you raise the LR 2 turns it adds 20Lbs to LR and RF. Equal amounts are subtracted from the RR and LF. Get the same results with tire pressures by lowering the RR it will add weight to the LR and RF. If your car weighs 1200 in the front and 1200 in the rear NO adjustment will change this. The only way to change front to rear distribution would be to cut something off the front and weld it to the rear. Example, if you raise the rear equally 2 turns that is all you've done-raised the rear.
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Disconnect both sway bars before you start the process.
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I adjusted my SPF to the recommended ride height and when I checked the corner balancing it was spot on. I have never driven my Cobra with the corner balancing off by much so can't comment on the improvement made.
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Any idea what a speed shop would charge to do this?
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I have corner balanced sedan type road race cars. The method used was to match the cross weight of the RF/LR to the weight of the LF/RR. This does not yield equal weights on thr RF/LF or the LR/RR. The target is to achieve similiar cross weights to create a neutral chassis balance durng aggressive cornering. Example-a higher weight percentage on the RF/LR cross favors left hand turns. Keeping the cross weight similiar generates a setup that turns right and left with similiar handling characteristics, no oversteer or understeer when turnng right or left. However this is all fine if your spring and sway bars are perfectly chosen as they also impact "tight or loose" Performing this on a Backdraft may be a pain the #%ss as you only have coil over adjusters on the front. The rear spring is conventional (seperate from the shock). This would require spacers placed under the spring. In addition to balancing the cross weights, you also have to maintain correct ride heights, not as easy as it sounds. This can be a half days work. In addition our scales are on setup stands that are laser leveled with each other. The surface of the shop floor is not accurate to do this.
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I should have added this is done with driver or similiar weight in vehicle and sway bars disconnected. It is almost mandatory to have some form of adjustable sway bar link to reconnect without disrupting the scale work performed.
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I had one shop try it years ago and although in their minds they had it balanced, the ride height was all messed up. As stated above, not as easy as it sounds. You are wrestling with two variables. Height and balance. |
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It possibly needs re-stating that you're not trying to get all four wheels to show an equal weight. If you have a front or rear weight bias, no amount of corner balancing is going to change that.
Instead, the idea is to get the sum of the weights of the diagonal wheels to be equal i.e. LF + RR = RF + LR. As Pat just said, it isn't rocket science, but it can be frustrating and you'll be surprised how little adjustment you need to make a big difference to the registered weight. Get your ride height and tyre pressures set first though before you start messing around with the corner weights. You really need to have all four wheels on the scales at the same time i.e. one under each wheel. You can't just weigh one corner at a time because you'll chase your tail forever. :JEKYLHYDE Paul |
Here is an interesting site with some very good technical information. The first Cobra on the weight sheet is mine with 160# of fuel and a 165 # driver. I have a 46.5% F and %53.5 R bias. They have been at many Good Guys car shows with their 4 corner racing scales. They do it for no charge and provide you with a 4 corner print out. The real work is getting the cross corner weights adjusted as Patrick has indicated.
Vehicle Weights « Ridetech – Tech |
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