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Old 30th March 2008, 09:40
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alackofspeed alackofspeed is offline
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Join Date: Jul 2005
Location: Dorset
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John - I don't have the skills to drive around the woes, which is why I'm trying to get the car corrected, and made more docile. I've spent too much time driving idiot proof FWD cars to be especially able with a mid-engine RWD car, with a fairly low moment of inertia.

Presently, there's no denying the car is a ditchfinder - reasonable in a straight line, but throw in some corners and a broken surface, and the car gets very unsettled! A typical modern diesel hatchback is far more capable on b-roads, and that my daily driver bettered Ric H's lap times around Llandow, goes to show the lack of confidence the car inspires. I don't think the lap times at Llandow have anything to do with driver ability, as I think I'd be faster on track at present in my hatchback, than in the 5EXI.

Yesterday there was a lot of rain, with standing water lurking on many of the single-carriageway a-roads. I'm pretty sure the instability of the rear geometry caused by the closely spaced top pick up points on the rear uprights, means the rear end grip under drive is considerably lower than it could quite easily be. Whatever the cause, when it's like it was yesterday, the ease with which the rear wil step out, excites one to exercise appreciable caution, and drive as smoothly as possible.

A few figures from yesterday's exercise:

Front / rear weight distribution: 44% / 56%

Axle split left to right - just under 1% on both the front and rear.

Front roll centre approx 115mm above ground.

Rear roll centre approx 145 mm above ground.

For comparison, Jon Coombes' car has a roll centre about 25mm off the ground, which is generally regarded as good practice.

The front suspension has an element of pro-dive, which is slightly unorthodox, and generally translates to needing a higher spring rate to counter the dive, which compromises the braking ability.

The rear suspension has a small amount of anti-squat, which is common practice, and generally considered appropriate for a road car. Dragsters, and hill climb cars, are typically the exceptions, and I understand sometime have pro-squat.
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