thanks to all that responded to my usa car rental question

the dodge neon is sounding like a good deal..but im going to do a fair amount of miles in it and keep it for 3 weeks

anyone driven a late one..what are they like?? i dont want to be bombing about in a really nasty car

or can anyone comment on what car they got Read more

8 < SNIP 8<

Yes, I know it's Friday, but we still don't allow the backroom to lower itself to that level, thankyou.

DD. Read more

I am bored.

What is the cheapest fun intro to motorsport ?

I'm thinking hill climbs, rally, track. Dont fancy grasstrack. I would like to do something which can feed through and improve my ordinary driving (I am of course excellent already ;-) By which I mean vehicle control, understanding limits etc that you cant/shouldnt play with on the open road.

I know that there are road rallies which seem to be about mapreading and planing, and I could do trackdays but neither of those really appeal.

Any suggestions ?

Thanks

M Read more

Hi

Do grooves in tyres increase cornering traction? I'm thinking if the edges of the groove catch on the ground surface and help prevent sideways sliding?


--------------
Mike Farrow Read more

Having seen a couple of threads where some confusing information has been given about load transfer under braking and cornering, I thought I might have a go at clarifying the subject.

Firstly, I want to restrict the post to steady state behaviour - by which, I mean once the car is settled into the corner, or has been braking for some time, and the car body is no longer continuing to roll or pitch any further. Considering the full response including transients is much too dull for a leisure time activity!

Tyre load transfer under braking is *solely* due to the fact that the tyre force occurs at ground level and the vehicles centre of gravity is above ground level. (This is the vital idea people tend to get wrong)

A pitching moment or torque is created by the braking force multiplied by the height of the centre of gravity - this is entirely balanced by the load transfer multiplied by the wheelbase. Whether the braking is done by the front or rear wheels does *not* affect the amount of load transfer.

Note here, I'm talking about how much extra vertical force is pushing the front wheels down into the road, not how far the vehicle's body pitches - that's a different matter.

The response of the vehicle body to this weight transfer, i.e. how far the car pitches is proportional to the weight transfer, the pitch angle, while governed by the stiffness of the suspension, may be modified by anti-dive and anti-squat suspension geometry, so that the pitch angle under braking can be related to how much braking occurs on the front compared to the rear.

Exactly the same situation occurs in cornering - with one extra significant complication.

The *total* amount load transfer across the car is governed by the height of the centre of gravity, and the track width of the car, together with the car's mass and lateral acceleration, that's all there is to it.

The amount of roll angle is governed by the roll stiffness of the car. But, this may be modified, both by suspension geometry, and by devices like anti-roll bars.

Here's the complication - in roll, the weight doesn't need to be transferred equally front and rear. As an aid to picturing this, consider chopping a hypothetical car into two functioning halves, left and right, only joining them with a ball joint type bearing at the centre of gravity. If you were to drive this car in a straight line and then brake, the two halves of the car would still move as one (you have mirror symmetry about the cut). If you took another car, and replaced the cut along the length of the car with a cut across the car with the same type of ball joint at the centre of gravity and try to go round a corner, you would find that either the front of the car, or the rear would roll further - depending which end had the stiffer suspension in roll.

An anti roll bar attracts more vertical load. For example, consider a car with a 50:50 weight distribution and a stiff front anti roll bar (or a suspension geometry naturally stiff in roll). During a corner, the anti roll bar will make the front outer wheel carry more than 50% of the load transferred from side to side.

For a given lateral or longitudinal acceleration, all you can do to reduce load transfer is to reduce the height of the centre of gravity, reduce the total mass, or increase the track or wheelbase respectively.

Number_Cruncher

Read more