[Porsche]

Originally Posted by JDM-dono

I got my BRZ a few weeks back and don't know whether I'm doing something wrong or otherwise.

You’re doing something wrong, mate.

Say I'm driving along a straight road at 80km/h (50mph) and am going into a slip lane for a 90 degree turn into a suburban street. I'll downshift down to 2nd gear and as I release the clutch (from 3rd to 2nd), the rear tires chirp (or slightly lockup).

I’ll bet they do. And you’re correct, you’re momentarily locking up your tires, which is to say they’re skidding. A tire that’s skidding like that has little to no directional control. Do that in the wet (it rains in Australia from time to time, right?) and while initiating a turn … and you’re likely to find yourself spinning around and quite possibly crashing. People do this all the time in the city and while the speeds are generally low, what happens is that they slap a curb sideways with the wheels and fold them under. Typical repairs are in the neighborhood of $5000 US and up. More if you flip your car on its head. You’ll be unhappy.

You’re changing down too soon and to a gear that’s too low. Change into second gear to go around a turn at 10-20 mph, perhaps. Use third gear, otherwise; it's good for 23–83 mph @ 2000–7400 rpm.

When you change down into second gear at 50 mph, while abruptly engaging the clutch you’re sending a shock through the drivetrain, the engine is acting as a brake on the drive wheels because it cannot instantly spin up to almost 6100 rpm at 50 mph, causing the rear wheels to lock up momentarily … and this is a scenario leading to a crash real soon now, especially in the wet.

...how can I avoid this?

Stop doing that.

Cruising along at 50 mph, an appropriate gear would be fifth or sixth gear.

Don’t change down into the next lower gear until the revs in the current gear are around 2500 or lower.

The tachometer (tach) will tell you this. That’s why God gave us tachometers for our sports/GT cars. They’re very important, even more so than speedometers. We need speedometers largely to avoid confrontations with The Law. The tach is for driving the car properly, keeping the engine in the appropriate rev range and power band as required.

By the way, before I forget, Sierra is an unusually knowledgeable fellow and you could learn a lot from him, AND he’s a fellow Aussie, I believe.

I'm tempted to ease of the clutch slower but then I'm worried about riding the clutch.

Exactly. Excess clutch wear is the inevitable result of “dragging” the engine up to 6100 rpm by slowly engaging the clutch. You MUST do that anyway, if you insist on changing down to any gear that zings your revs (rpms) up to 6000 rpm or even 4500 rpm. It’s too much and runs the risk of locking up the rears (tires). You don't want to do that. Not so much because it's abusive to your fine car, but because it's dangerous.

You MUST slowly engage the clutch, however, regardless of the wear issues, BECAUSE YOU’RE GOING TO CRASH OTHERWISE! It’s just a matter of time…

Crash repairs will easily exceed the cost of clutch disk replacement.

Slightly getting worried about how all this affects the life of the transmission/clutch 

You should be worried, yes. What you’re doing is not only dangerous, skidding your rear end, it also subjects the clutch and entire drivetrain to unnecessary wear.

You CAN change down at higher rpms, but then you must learn to rev match properly. That’s why rev matching was “invented.” Precisely to avoid this problem and allow one to SAFELY change down through the gearbox at higher rpm while largely eliminating clutch wear (when done skillfully).

Heal and toe (sometimes a misnomer) is simply rev matching while SIMULTANEOUSLY braking. This is a technique for going faster, basically, and not running the risk, once again, of locking up those rears when charging into a corner.

Yes, there’s a lot to learn, but you can do it despite the initial awkwardness everyone experiences. It’s challenging, fun, and as Whaap alluded to, eventually you will “become one” with your machine.

It is immensely satisfying.

Keep working at it. And buy some good books on driving. Frankly, most of the youtube videos I’ve seen are poor at best. Do a search on “Skip Barber.”

Better still, find a good racing-oriented driving school at a local race track if you have such things in your area. It would be money well spent. I’d recommend that before buying hardware for your car.

I must run, now.

I hope this has been at least a wee bit helpful.