What's harder on the car, Autocross or Tack days?

[brake-fade]

Any thoughts on which puts more stress on a car, autocrossor or track days? I have a 2008 128, 6 speed manual with 246,xxx miles on it, and I love to drive it at it's (my) limits. I know the two are very different stylesof driving, but which is going to be harder on my car? I would really love to do a couple of track days this summer in addition to 6 autocrosses, but I'm hesitant because of the milage. It's the drivetrain I'm concerned about. My suspension is completely new...every bushing, shock, strut, spring, contol arm, trailing arm, M3 swaybars (M3 stuff at every point, front and rear) Swift Springs and Koni yellows with Dinan fixed camber plates. The brakes are also new but pretty basic. Coolant system is also completely new. The drivetrain is totally original, including the clutch...which is why I'm hesitant. So which is harder on my car? After all, I will need to drive it home.

[summitp]

Track day. Harder on engine, harder on brakes, harder on chassis.
At the track, your car is basically working as hard as it can in all aspects, putting down power, braking, cornering. Cooling system is taxed and will likely need upgrades. Stock brake system will need a thorough going through, and may need upgrades.
That said, the 128i is a desirable track machine as it's relatively simple, good driving dynamics, and relatively low on cost of consumables, (tires, brakes, gas, etc...)
Autox is fun though. I haven't done either in years. Getting ready to jump back into autox with the 128i.

I tracked a street car for a while until the motor let go with 140k on it (Toyota mr2 turbo) and had to trailer the car home. I fixed it, but i never took it to the track again. I ended up buying an already built Porsche 944 spec car and driving that and getting into wheel to wheel racing. Good times. And the 944 was a relatively cheap car to run on the track. Tires and gas. Change the oil every other event. Car never gave me a lick of trouble. But then kids came along and no more racing.

[e4603]

I agree with Summitp. Track days are much harder on your car. Like Laguna Seca turn 2 braking from 100 mph to 40 in a street car while driving in a “relax” pace. In autocross I probably brake from 25 to 10 and not get out of second gear.

[twinturbovan]

Hey dude! Track guy here, can tell you easily that track days are harder than autox. However track days are much more enjoyable imo although a lot more costly. Brake fade can be a serious issue if you are not experieneced espescially when your new a person tends to push the brakes more often than not because of nerves but that goes away with experience. Going from 160+ down to 40 after the straight at COTA is pretty insane but extremly hard on the brakes. Ive seen some cars go off track due to brake fade, even saw a McLaren wheel break off completely. I started off tracking mine as a complete stock car and stock suspension with the exception of BC Coilovers. Now the car has undergone big turbo upgrade and putting down a lot more power and currently installing my RSF Splitter to flow with my RSF Wing and have a lot more track spec stuff coming even M3 Suspension parts. Either way i can guarantee you that tracking a car is harder on everything but if the car is well maintained you shouldnt have any issue. My car always had misfire issues but with the new build i have no issues so I should be able to start working on time attack since im a solo driver now. If you have any questions feel free to hmu.

[twinturbovan]

Here some photos of two different track days I attended at Circuit of Americas: