# Homework Help: How to adjust cars diagonal weight without scales?

1. Jun 11, 2013

### chkhikvishvil

hellow everyone, this is not a homework but a real life problem

this is the weight distribution of my car , on 4 tires

[URL=http://s1328.photobucket.com/user/chkhikvishvili/media/20130611_112304_zps58a4ee33.jpg.html][PLAIN]http://i1328.photobucket.com/albums/w527/chkhikvishvili/20130611_112304_zps58a4ee33.jpg[/URL][/PLAIN]

it is very important to make the diagonal weights the same, so I want to rise the rear right side of the car which will shift the weight so that diagonals will be equal, by rising I meant that i will put something under the spring which will rise the chases

but the problem is i dont have the scales to adjust the rise, thats why i need to calculate by how many cm i need to rise rear right side, i feel that is possible to calculate :) also i am sure I must input something about the springs, how stiff they are, because I think it matters, but how can I characterize them? also i can measure the wheelbase and track width if its needed

any ideas how i can do calculations? :)

thank you

2. Jun 11, 2013

### SteamKing

Staff Emeritus
Instead of fiddling with the springs, it would probably be easier to take some weight out of the heavy side of the car or put some weight on the light side of the car.

I'm curious: why is it so urgent that the diagonal weights be the same? I hope you realize that the engine and transmission in your car is what makes it so heavy at the front end. There are only a few cars which have a 50:50 F/R weight distribution.

3. Jun 11, 2013

### haruspex

Do you mean that you don't have on-going access to the pictured device? There are lower tech approaches. With the same pressure in all tyres, estimate the area in contact with the ground. E.g. on a dry concrete surface, slosh water around then move the car and measure the dry areas.

4. Jun 12, 2013

### chkhikvishvil

SteamKing
yes I am happy with F/R weight distribution as it is, and you can not even change it without moving the mass inside the car, but the diagonal weights distribution it really urgent because if they are not even the car is like a table with one leg shorter then the others, it has great impact on handling, and when i brake on my car, front left and rear right tires lock up first because of that
haruspex
exactly I dont have access to that device any more :( and the method you described seems practically impossible, and tire walls are also quite stiff so there is not only the pressure that holds the weight so you can not calculate like that
On the other hand is must be mathematically calculable, given the data I have, also wheelbase and track width you can first find the center of mass, and then calculate how much you should rise the rear left side of the car so the weight would shift and you get equal weights on diagonals
but I dont know how to calculate that

5. Jun 12, 2013

### haruspex

I'm pretty sure that if you let all the air out of the tyres they'd go a very different shape.
Not that I can see. As you noted, you don't know the spring stiffness.
Another possibility is if you had some strong stiff beam you could place over a fulcrum. You could drive onto it to find the balance point of one side. Bit tricky, though.

6. Jun 12, 2013

### SteamKing

Staff Emeritus
If your brakes are locking up, you need to have them inspected and repaired if necessary. IMO, the weight imbalance from side to side, front to rear is not the cause of the lock up.