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Comment by jacquesm | Hacker News Reader

If you replace brake pads and you are going to keep your rotors have them turned down a tiny bit to ensure roughly double the wear life on your brake pads. If they are too thin to be turned down safely then you'll have to replace them anyway.

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Nobody turns brake rotors in the US anymore. If your price sensitive, you'll just buy a Chinese-made rotor for about what turning would cost. If you're not so price sensitive, chances are good that your brake rotors use an alloy that the old brake lathes can't cut anyway.

I used to get rotors turned. Then I stopped because it was a pain. Unless a rotor has been grooved by a completely worn brake pad (i.e. the backing plate and rivets made contact), I haven't seen any difference in performance or longevity.

I don't know of many places that still turn rotors, many of the big shops stopped and so did some smaller, unless they're specialty I always buy new, partially the reason I do it myself.

That's mostly a decision to increase turnaround speed on their bridges, it is faster to swap a rotor for a new one than it is to turn one down. But if you're cost conscious enough to replace your own brake pads and you don't want your new shiny pads to be just as bad as the old ones after a couple of weeks (as in: grooved, they will likely still be thicker) then turning the discs is a good option. Where I live this is still pretty easy, it might be harder in other places to find shops that will do this. Cost me about 10,- / disc.

I'm still not really clear on why it matters. If anything, grooved rotor/pad combos have more friction surface :)

I just swapped pads last weekend for a track day, my rotors are grooved and should be replaced next time I have to replace my street pads, but once the pads are bedded in, they still grip amazingly well.

It essentially cuts life from the pads, it does not change your braking distance.

Just as bad in a few weeks seems like a bit of an overstatement then, unless you're replacing your pads based on their wear rate instead of how worn they are

Depending on how bad your disks are that can really add up.

> That's mostly a decision to increase turnaround speed on their bridges, it is faster to swap a rotor for a new one than it is to turn one down.

I used to turn the rotors on my European cars, but about 10-15 years ago the alloys started warp after being turned just once or twice. Easier to just pay to replace than take the risk of doing the labor twice.

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