DIY geometry alignment

[buzzer]

I have had some Dunlop tracking gauges for many years, these are still good and accurate bits of kit for setting the tracking on the car and they have the advantage they are easy to accurately calibrate.

One of the things I have never been able to do though is set the rear track… By using the gauges on the rear wheels (you have to reverse the readings) it’s possible to get an accurate Toe in or out, but you never know if the wheels are aligned to the fronts… It’s possible that if you say have 4 mm “toe in” on the rear, it could be all on one wheel. I have tried the string method to measure this but with limited success.

A few weeks ago I hit on the idea of using a couple of laser levels in combination with the tracking gauges… by carefully mounting them on the top of the track gauges, and then calibrating them so they shone the beams parallel, I was able to accurately set the rear track in relation to the front. due to the length of the beam, the slightest variant on the rear shows up 20 fold on the measure...


While I was on, I made a camber gauge out of one of the cheap digital angle gauges. These measure to a .1 of a degree, which I feel is accurate enough, given to tolerance most manufactures give for the settings.

I also used the laser level to check how level the garage floor was… The answer was that side to side, it was 5mm out, but from front to rear (where the wheels of the car sit) there was a 40mm slope. I made some turn plates so I could compensate for that, and also as there is grease between the plates, it means that any adjustment made to the suspension easily settles, rather than keep rolling the car back and forth.

So far I have checked my SLK 55 AMG which was almost bang on to the middle of the settings given by the manufacturer. My MX5 however was MILES out! The camber and castor on the front was OK, as was the track (I had previously set this…) but the rear camber readings were 1.8 degrees on the NS, and 0.5 on the OS! The track was also out, but more importantly the wheels were massively misaligned to the fronts. It took me ages to get it right, but now after driving the car, the transformation in how it drives is amazing!

[blitzracing]

Using the thin tensioned string (Like kite thread) method or fishing line between parallel metal bars at the front and rear of the car to form a perfect rectangle around the car as a reference point. I prefer this to lasers as its dead easy to get the distances between the front and rear wheel centres spot on by moving the bars, unlike lasers angles that have to be spot on on their mounting points as they project forward. Not quite so high tech' but do it properly and +/- .5mm on the toe distance is easy done. In terms of turn plates , high gloss magazines work well. Certainly cheap and cheerful.

Edited by blitzracing on Sunday 6th April 13:26