Do brake discs need to be turned in pairs?

[Saluki]

I am replacing the pads on my 99 windstar, and one disc is grooved. The other side, which I did first and have already put back together was smooth. Do I need to pull it off and have them both turned?

[12Ounce]

I see no need in machining or replacing the rotor on the side you've already serviced.

All manufacturers design rotors so thin, there is very little chance to (legally) machine one if there is much grooving or wear. You don't want it failing during a severe braking load.

I find the aftermarket rotors priced low enough to make them more attractive than paying for machining.

[zirb]

Never had much luck getting them turned down. For the price of a new one I would just replace it.
They should only be about 25-35 dollars each.

[ModMech]

The answer is: It depends.

If the rotors are on the FRONT, then BOTH should be replaced. The reason you NEVER replace (or turn) a FRONT brake part (pads, rotor, caliper) on one side only is that that is where the steering is, and you can EASILY cause unequal braking between the LH and RH sides that could cause a loss-of-control during a hard stop.

It is my recomendation to ALWAYS REPLACE both FRONT rotors if either show signs of wear, warpage, or excessive corrosion. If the old rotors are BOTH smooth and there was no hint of pulsation when stopping, just replace the pads.

For rear rotors, almost anything goes.