Axle arm. Mandrel to check the arm alignment.
Tool to check if an arm is bent. Videos at bottom of the page
The mandrel fits into the 2 bearing cones The pin has a 5 degree inclination with points on either end
Each pin is 400mm long. The other pin fits into where the kingpin would be. It has marks on it to centralise it and 2 collars to keep it in the proper position. Fit the mandrel into the bottom of the arm. Lay the arm onto a flat surface, using the flat metal plates underneath and turn the mandrel until the kingpin end is lying flat on the surface. It will not fall over. The 2 pins must be absolutely flat, to get an accurate measurement. Measure the distance between the points, on both sides, the 2 pins should be parallel to each other. You have an allowance of a maximum of 10mm out of true. If it's over 10mm, the arm is bent too much and has to be replaced. You will wear your tyres out very quickly. If you feel that your steering is impaired, even when you have hit the kerb, it might be the best idea to check your arm(s). After an impact, the track rods can also be damaged. This will affect your steering also. All the tools, to do the inspection and testing, are avalable for hire.
Checking the camber angle. Wheel straight ahead. Checking the camber angle. Wheel on full lock
The axle arm has to be balanced and positioned in a horizontal plane, so that the bearing bore is perfectly in line with the base. I used a Moore and Wright spirit level to achieve this setting. A plastic school protractor is needed and an adjustable angle measuring gauge. In the straight ahead position you should get a reading of 1 degree + 40' or - 25'. On full lock you should get a reading of 9 degrees - 1, + 25'. Find the level of the flat surface and note the bubble position. Transfer the spirit level onto the arm top at the bearing end. It needs to be really clean for the level. Note the bubble position again and adjust the arm to the correct bubble position. The arm should now be in horizontal plane to the flat surface and you can now measure the camber angles. The arm should be in the position it would be on the car, all be it, it is upside down on the test table. Re-position the king pin end to get a 10mm clearance between the 2 lugs and the table surface at the bearing end. RE-CHECK THE BUBBLE POSITION.
Checking for a bent or twisted arm. In the next video, I show an improvement to the long bar that goes into the kingpin hole. The arm keeps sliding up and down and needs to be kept in a stable position. I have made some collar stops to hold it in the correct position[s] and also added some 20mm square bars to lay the long ruler onto, to make easier and more accurate measurements between the points. I have also added 3 flat metal plates to enable the whole arm to lie on the table. The video shows where they go.
Checking the camber angles at straight ahead and full lock. Its important for the arm to be level and square with the flat table.