raiyu said:
I downshift to first all the time and always downshift as my primary braking, helps reduce break wear, I dont care if I wear out my synchros by that time I will probably be giving the car back anyway, plus its a good habit to have because in an accident situation downshifting + braking will slow your car down faster with more control.
I have used downshifting to slow the car down in lieu of brakes, particularly in inclement weather, but if you do not match the revs the car has as much or greater potential to lose control.
When you downshift and do not match the revs, the road speed is translated back through the wheels, driveshaft, transmission, to the engine, which is why you see the RPMs increase.
That action will often cause the rear tires (on a RWD car, of course) to break traction. Race car drivers downshift so they will be in the correct gear at throttle application in the corner, not to slow the car down. Many a spin has been caused by a botched downshift in heavy braking that caused the rear tires to break loose.
So, if you are using a non-rev matched downshift in emergency situations, you are creating more of a dangerous situation than if you had just used the brakes.
And, if you do match the revs, you don't wear out the synchros.
BTW, what most people think about as synchro wear is actually hub selector wear, which is the first thing to engage when you shift, followed by the synchros and ultimately the gear itself.
