A g force is an acceleration force. Because the feeling of gravity is the same as the feeling of acceleration (Einstein's Equivalence Principle), when we're sat on the surface of the earth (as we all are now), we're said to feel "1g". This is equivalent to an acceleration of about 10m/s/s (so if you accelerate from rest to 10m/s in 1 second, you feel "1G", or perhaps to 30m/s in 3 seconds, 40m/s in 4 seconds etc). Incidentally, the usual analogy of the equivalence principle is that a man in deep space accelerating upwards in a lift at 10m/s/s wouldn't feel any different to a man sat still on the earth. Using this, you can easily work out the "g force" of any acceleration (it's actually 9.81m/s/s if you want to be more accurate), by just dividing the change in speed in m/s by how long it took, and then to get the g force, divide by 10, or 9.81. Don't quote me on this, but I think 0-60 in about 3 seconds is 1g (edited to say: stated below as 2.74s). Most road cars will pull approaching 1g in braking and cornering, because that's the frictional limit of your average road tyre against your average tarmac (probably the reason most road cars don't dip below 3 seconds 0-60...). Typically, a normal road car or motorbike will get up to about 0.7-0.8g, and something like an Elise may just about breach 1G. That's in cornering and braking. American magazines test this for cars, so you can find this info on the web. Junior level single seaters such as I race will get around 2-3g, thanks to very soft slick tyres (they give their best after about 40-50 miles...) and modest downforce. Incidentally with only 350-400bhp/tonne (the same as a Caterham R400), a Formula Renault will do 0-100mph in 4.9 seconds, such is the grip on offer!). Formula One cars can pull up to 5G. When g is experienced downwards or upwards, such as when banking hard in a fighter jet, the blood rushes away from or towards your head, causing black-out or red-out. I think the limit for most fighter pilots is about 7-8g, but correct me if I'm wrong. People vary enormously in their tolerance of vertical g, and the soviets actually select their pilots early on in training based on this criteria. I'm terrible, and blackout if I stand up too fast! Obviously the cars I race though only pull g from side to side and front to back, so I'm ok, provided my neck muscles are strong enough. Personally, I love lateral g; there's nothing quite like the feeling of cornering at over 100mph - at Snet I'm taking Coram flat at about 115mph which is great smile I'd love to try a higher downforce car like an F3.
HTH
I'll hope to be able to do a S85 and a P85 model test drive close together !
