I'm getting close to putting this thing on the ground and have a couple of questions. First, does the engine need to be in - I would guess yes from the impact the added weight will have on geometry. Second, has anyone done this on their own? What kind of tools or gadgets did you use? Od did you just take it to an alignment shop (where's the fun in that!?).
Wheel Alignment
- Thread starter patbarry
- Start date
Hi Pat,
If you opt to do the alignment yourself, there's quite a lot of things you need to check, most can be done with the engine out.
For example, front and rear bump/roll steer can be checked with a fairly simple jig using a dial gauge. Its difficult to describe in words, but if you can get hold of Allan Staniforth's excellent book, " Competition Car Suspension", there is a full description of the jig and how to set it up in Chapt 7. Using this jig, I was able to virtually eliminate front bump steer and rear roll steer by shimming the steering rack and locations of the rear (lower) transverse and radial arms. Then I replaced the shocks with fixed length bars to simulate the nominal ride height of the car and used simple thread and plumbob to set the camber angles of the front and uprights. Most of this stuff is iterative and time consuming, but like most things, the more time you put into it the better the results. The original GT40 suspension settings were given on this forum some time ago and in the absence of anything better, I used those. Castor measurements can be done using a professional castor gauge, but I got carried away and analysed the front geometry then calculated how the camber should change over a range of steering angles for a given castor angle. Castor alters the camber at different steering angle, but there are quite a few other factors (eg kpi,etc) to take into account). Although not for everyone, I found the exercise of doing my own alignment to be very informative when trying to understand the car's handling behaviour. The use of an inverted A arm for the rear suspension means that some care must be taken to ensure there is minimal rear roll steer, especially under compressive suspension loads.
Good luck
If you opt to do the alignment yourself, there's quite a lot of things you need to check, most can be done with the engine out.
For example, front and rear bump/roll steer can be checked with a fairly simple jig using a dial gauge. Its difficult to describe in words, but if you can get hold of Allan Staniforth's excellent book, " Competition Car Suspension", there is a full description of the jig and how to set it up in Chapt 7. Using this jig, I was able to virtually eliminate front bump steer and rear roll steer by shimming the steering rack and locations of the rear (lower) transverse and radial arms. Then I replaced the shocks with fixed length bars to simulate the nominal ride height of the car and used simple thread and plumbob to set the camber angles of the front and uprights. Most of this stuff is iterative and time consuming, but like most things, the more time you put into it the better the results. The original GT40 suspension settings were given on this forum some time ago and in the absence of anything better, I used those. Castor measurements can be done using a professional castor gauge, but I got carried away and analysed the front geometry then calculated how the camber should change over a range of steering angles for a given castor angle. Castor alters the camber at different steering angle, but there are quite a few other factors (eg kpi,etc) to take into account). Although not for everyone, I found the exercise of doing my own alignment to be very informative when trying to understand the car's handling behaviour. The use of an inverted A arm for the rear suspension means that some care must be taken to ensure there is minimal rear roll steer, especially under compressive suspension loads.
Good luck
One other book you might find useful is "How to Make Your Car Handle" by Fred Puhn. This book is probably easier to find in the U.S.
It shows a similar bump steer gauge as Staniforth (but I recommend using dial gauge not fixed pointers) and explains how to set up all alignment measurements.
It shows a similar bump steer gauge as Staniforth (but I recommend using dial gauge not fixed pointers) and explains how to set up all alignment measurements.
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