measuring and setting Toe in.

[gvy]

Hi,

Since I had to change my rubber mounting / radius arm bolts recently ( one just broke ), I thought it was the right time to check the cars geometry.

I am a DIY er so , DIY it will be.

First I made 2 identical straight ( heavy) SS bars. With double sided tape, I taped 2 rubber feet on them and I marked the center point and two identical marks right and left. One bar comes on the front of the car and one bar on the back.Right and left of the car I connect the two bars with a masons string. I use the identical marks to be sure that the two strings are perfectly parrallel. Next I place the system measuring from the string to the wheels. The two strings are now perfectly parrallel positioned with the centerline of the car.

 

FRONT OF THE CAR

 

BACK OF THE CAR

 

Next I use two straight aluminium bars of 2m. On the corners I put a short string and a ringscrew as plummet. The aluminium bars are layed on a brick and in contact with the tires.

Next I can measure from front plummet to masonstring, and from back plummet to masonstring. Some math and I have the exact toe in or toe out value of the wheels.

It is quit accurate, because I use the 2m long aluminium bars to amplify the distances.

 

I did set the rearwheel toe in and the frontwheel toe in.

I deviated from the values given by the handbook and followed some tips from Tim Engel.

So

rear toe in right wheel is now  2,16mm ,

rear toe in left wheel is now 2.16mm

front toe I set to 0 mm.

 

The total toe in of 8mm according to the handbook for the back is well... a lot.

this is not a turbo car so the back is not swinging its ass that fast, so I safely set it to a total toe in of 4.32mm and spare the rear tires a bit more.

On the front I try a neutral 0mm instead of a safer 3mm toe in according to the book. This makes the car a bit more vivid cornering, without being unstable. Some people even use toe out.

Geert

 

 

Edited April 6, 2017 by gvy

[C43]

good write up. You can simplify it a bit by lifting the front and rear bars to axle height and then just measuring from the string to the centre of the wheels to make sure the bar are set equal left and right. Then just measure from the string to the front and rear of the wheel and do the maths to get the toe. In this way you don't need the bars added each side of the wheels. Probably better to use fishing wire if doing it this way as its thinner. I know this method seems a bit crude but F1 has been using that method for the last 40 years at least and some teams still do it.

Chrisitan

[gvy]

Christian,

I have thougt about those suggestions before, but for me this setup works fine. I explain:

I chose to place the wire just above the ground. (about 0.8cm, thickness of the rubber under the bars), because  for me it is easier to accurately measure on surface level.( ruler on the floor).

To set up and position the strings. I measure from center of the wheels using a square. But I soon discovered , that , in my case, I got the same result measuring on the floor from the bottom of the tyres to the string. Both measurements gave the same outcome. So I am quit sure the two strings were placed exactly parrallel to the centerline of the car.

Second, I really prefer to use the 2m alu bars. The wheel diam is about 390mm. The two plummets on the bar are 1950mm wide. So measuring a difference between the two plummets of fe 10mm gives a toe in of 2mm measured on the rims. I mean, the long alu bars amplify the measurement difference with factor 5 , leaving me with a more accurate reading.

So infact:

If you measure from a string to the front and rear of the wheel, you are measuring differences in magnitude of 0.5 to 4 mm.

With the long alu bars, I am measuring differences in magnitude of  2.5mm to 20mm

 

Geert

[gvy]

A good Idea would be to lift the front and rear bars (and thus the strings) to axle height (as you mensioned) , but still use the 2m alu bars at axle height, without the plummets.

That way it is , as you say, easier to position the system and I keep the accuracy of those longer bars. I admit that the plummets can be a pain, because they tend to swing a bit if they are touched.

[jonroberts]

I use exactly the method Christian outlined with nylon fishing line and its quite accurate, but you are right the offsets are small to measure.  I like your idea with the bar and amplification Geert.

[DanR]

I use this tool. Fast and accurate.

http://www.ebay.com/itm/Toe-Plates-Most-Accurate-DIY-Wheel-Alignment-Tool-Gauge-/281932528463

Periodically I do the string check to make sure the body and both axles are square and in line. Ideally the body should be raised, plumb bobs used to mark the floor and a diagonal check from the suspension pick-up points to make sure the car is square.