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July 2004

Suspension alignment

I had realised the suspension was out of line after the cars recent MOT. At the MOT both front brakes registered the same braking force, however on a loose surface the passenger side front wheel always locked under braking with the others still turning. This was obviously not good and something was slightly out with the geometry. A lot of searching later and I found a company called Kelvedon Motors who are very highly regarded in the Lotus tuning world. They told me they could do the alignment for a mere 42+vat an hour!

With some trepidation for a wallet emptying bill I took the car down to them to be sorted out. the first problem was finding them as the only clue to their location is a piece of yellow tape on a telephone pole (seriously) once I had done this I left the car and waited for the results.

Before adjustments

Setback: + 0 Deg 25'
Total Toe: + 0.00 Inch
Individual Toe: -0.18 Inch +0.17 Inch
Camber: -00 Deg 51' -00 Deg 20'
Caster: +03 Deg 30' -00 Deg 38'
KPI: +14 Deg 30' +11 Deg 06'
Included Angle: +13 Deg 38' +10 Deg 47'
Toeout on Turns: -00 Deg 54' +00 Deg 05'
Full Steering lock left: +25 Deg 38' +25 Deg 38'
Full Steering lock right: +29 Deg 02' +30 Deg 40'
Geometrical drive axis: + 0 Deg 21'
Total Toe: + 0.17 Inch
Individual toe: +0.26 Inch -0.09 Inch
Camber: -03 Deg 04' -02 Deg 34'

So what does this all mean. Starting from the top.

Setback

The ammount by which the axle centerlines are not in alignment (ideally it should be 0)

Toe settings

Normal toe settings as done by any garage, however you can see I had equal toe in opposite direction when the started.

camber

Again it should be equal on each wheel to preserve steering geometry

Caster

It should be equal as this is what determines the self centering ability (think shopping trolley wheels). Look carefully at the table above, there is virtually no caster on the right of the car and a huge ammount on the left side. Hence the rather strange cornering performance.

KPI

Angle through the wheel hub to a point on the ground. Not the easiest thing to adjust as it is dependant on the hubs being equal (so we will blame Ford for that one)

Included angle to Full lock right

The angles that change as the steering wheel is moved from lock to lock. It is a quirk of the Tiger that it will steer tighter on right hand turns than left hand. Someone will probably argue that most tracks are driven clockwise!

Rear Suspension

The rear suspension on the Cat can only be changed with a lot of engineering work being done, that work is "under consideration" at the moment.

After adjustments

Setback: + 0 Deg 27'
Total Toe: + 0.06 Inch
Individual Toe: +0.03 Inch +0.03 Inch
Camber: -00 Deg 27' -00 Deg 16'
Caster: +04 Deg 13' +04 Deg 13'
KPI: +13 Deg 59' +11 Deg 01'
Included Angle: +13 Deg 31' +10 Deg 47'
Toeout on Turns: -01 Deg 05' +00 Deg 09'
Full Steering lock left: +25 Deg 20' +25 Deg 00'
Full Steering lock right: +28 Deg 36' +31 Deg 06'
Geometrical drive axis: + 0 Deg 22'
Total Toe: + 0.12 Inch
Individual toe: +0.24 Inch -0.11 Inch
Camber: -03 Deg 48' -02 Deg 54'

As you can see the second set of figures are a lot more balanced that the first, and the car does handle noticably better than before, the only downside - getting to this stage cost 8 hours of labour and a 400 spend, so the back suspension will wait a while before getting done.

The biggest change is that now it will brake in a virtually straight line and when cornering the steering slowly weights up as the lock is increased. This has the advantage of giving a lot more feel to the car when cornering hard. Certainly I felt the difference when at North Weald a couple of days later although it will take quite a few more miles before I am entirely certain about what the car will do under different conditions.