Originally Posted by
A Squared
I suppose that true if you don't know how to downshift. It's quite possible to downshift and engage the clutch with virtually zero relative rotation.
Heel and toe technique - initially developed to ensure that when the rear tyres were lightly loaded braking down to a corner that the sudden imposition of further braking forces when you lift off the clutch in a lower gear didn't give you compression lockup.
A very usefull technique as it makes driving smoother and at the cost of a tiny fraction of fuel reduces wear on your clutch and engine mounts.