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Comment by peterwwillis | Hacker News Reader

About 26,472 cubic inches. Fifteen gallons is 3,465 cubic inches. (Taking the wheels off, if the car were rectangular its dimensions would result in around 696,581 cubic inches of volume, so the battery pack takes up about 3.8% of that)

Rotors don't have to be changed as frequently as pads. It's probably a lot easier this way vs dismantling the whole thing.

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Thanks for that info! So the batteries take up about 9 times as much space as a gas tank?

If you do not replace the rotor when you replace the pads, a machine shop has to grind the rotor, so its surface will be flat to work effectively with the new pads. If you don't, the pads won't make full contact with the rotor, and maintaining the brakes would make them operate worse until they wore in.

Ah, you're right. I'm cheap and lazy but this car deserves doing it right. Perhaps the pads are slipped in after the assembly is put together so you don't have to juggle with them while putting it on? Alternate idea: a chunk of the caliper missing reduces unspring weight?

I thought this was absurd so looked it up. Apparently most cars these days have metal pads, so both the pads and rotor wear equally. I'd never heard of that, all the small city cars I've had always had pads made of rubber/ceramic material.

A lot of manufacturers sell cars with ceramic because it's less annoying to the driver. Performance brake pads are going to be metal (or a combination of alloy and something else) because they bite harder and pull heat away from the rotor.

Brakes in electric cars receive vastly less wear than conventional vehicles, feels like literally an order of magnitude. They really only come into play at all during final stopping and emergency braking. The separate parking brake design on the Tesla is an interesting related detail.

Interesting -- so braking system consumables should last ~4 times as long as on a fossil-fueled car?

In my experience so far (Prius, 110000 miles) it is more like 5x. And the Prius brakes are tiny things, especailly compared to the huge brakes on the German cars I've owned in the past. The Tesla S is comparable to them in weight and handling, and the brake system looks comparable too. From the testing and reviews we know it has excellent stopping distance, so it looks to me like the best of both worlds. I wouldn't be surprised if it gets 10x the lifetime out of brake pads, depending on driving conditions of course.

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