Hi all, I'm new to Ten Tenths and have a motion ratio question

[meb]

I participate in weekend track events throughout the Northeastern US. I drive a 2005 JCW Mini Cooper and I've started to tinker a little with the suspension. I've always understood the reason behind attempting to lower the center(s) of gravity. Increasing track is one option...I've considered increasing wheel offset from a stock 42mm to 23mm up front and to 33mm in the rear.

My first question is, do wheel offsets 'effectively' alter motion ratios?

Second question is, I intuitively understand motion ratios as mechanical leverage, or the lack of. But aside from potentially using this formula to retain a stock damping or balance, my goal above, why else use this formula? Where do we begin and why? It seems to me that knowing much more about the car is important first; RC location and migration, CG location, front and rear axle weight etc. I'm a bit lost. Can anyone help?

Thanks

[PaulD]

At the rear, it won't change the motion ratio because the pivot is across the car so you are not increasing the lever arm - it will increase the loads on the swing arm and its bearings and reduce the camber stiffness.

At the front, it will change the motion ratio - the wheel rate will be reduced (10% or less). Less effect on camber stiffness though.

[meb]

Thank you PaulD. When I read your comment about the rear, I sort of smacked my head, "of course!" So the swing arm increases...the instantaneaous center moves farther away...so...when you refer to 'camber stiffness', what exactly do you mean? I understand camber and camber curves and what these potentially do for tire grip as a car rolls. I've read about this term in my past, but I did not latch onto its meaning.

Thanks again

[meb]

PaulD - I cannot find the edit option, but this questions goes with the post directly above. I assume that motion ratios in effect change as the suspension compresses - in the case of the Mini's Mac strut - and this has much to do with SAI/camber angle?...something a force velocity curve might point out...

[Suze]

meb - quick aside - you can't edit a post after ten mins - some other useful info like that in the FAQs.

back to topic!

[meb]

Okay, thank you...I read the FAQs fairly quickly.

[johnny yuma]

I'm currently reading Fred Puhn's book "how to make your car handle" mainly to try
to get a grip on Roll Centre etc.

The author advises doing the most obvious,testable things first especially
on sedan cars like playing with anti-sway bar rates front and rear,positive caster,negative camber,lowering the ride height carefully without losing
too much ride quality eg smaller diameter race wheel/tyre setup [this will give you more power especially in top gear]--Apart from making sure all the standard components are first class first.

Wheel alignment tools,A tyre temp gauge,a compressor,a day trying different tyre pressures -low key stuff but first things first.