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Is it necessary to resurface the brake rotors?

While rotating the tires a few days ago I checked the brake pads and noted that the front pads were almost completely gone. It doesn’t look like I got into the metal on the rotors and there has been no squeaking. Is it necessary to resurface the rotors, or will new pads be sufficient?

Most shops will tell you yes. Depending on the vehicle the rotors MAY not have enough left on them to turn (one time use rotors). If you are DIYing or can talk to the mechanic who agrees you can do a “pad-slap”. New pads, wire wheel the rusty ridge at the outer/inner edge of the wear surface, scuff up the wear surface, off you go. Pad-slaps work but the break-in can be a bit weird and it usually works better if you are using a "soft’ pad, not a ceramic, carbon or whatever high performance pad. Also you need to be sure that the rotor you are leaving on will have enough metal to go another set of pads. Need spec. thickness new, current thickness, min. thickness allowed to figure this. If you are paying someone to do a pad-slap “properly” (some would say there is no proper pad-slap) you can see that it may cost close as much in added time as a new set of rotors.

A shop makes every effort to avoid a comeback and that would always include turning the rotors. If the rotors are not unevenly worn or warped and are well within specs there is no need for the DIYer to turn them. If there is a squeal when the job is done you can live with it or do the job over and get them turned.

If they aren’t warped or damaged, I don’t resurface them. Resurfacing them makes them thinner, which makes them more susceptible to warping. If they need resurfaced, you might as well replace them.

A proper brakejob means replacing or machining the rotors. A shop should do this; a DIYer can choose not to do so and let the chips fall where they may.

Machining a rotor does not neccesarily mean the rotor will be more prone to problems than a new one. It all depends on;
A. How much is machined off, how close the rotor is to the minimum limits, etc.
B. Cost of machining the rotors weighed against the cost of new ones.
C. Whether the rotors are properly machined or not.

When doing my own I check the rotors and if the surfaces aren’t scored or glazed and the vehicle is stopping straight and true I just change the pads. But, as others have suggested, a shop will always and should always either resurface the rotors or replace them. It’s really the only way to ensure customer satisfaction.

@ Whitey: Good point.

@ok445: re B. above. Yeah, have you priced out a good set of carbide bits recently, mucho $$

A shop will probably not give you the choice. They state a flat price for brake service and that always includes resurfacing. You might insist that they do NOT resurface, but don’t expect an automatic price reduction.

If you simply replace the brake pads yourself, you may choose to skip resurfacing. I always do.

Squeaking and squealing can result if you don’t resurface the rotors…The is a spray-can product, CRC No Squeal, something like that, you spray it on the rotors during pad replacement and it “resurfaces” the rotors and seats the pads during the first few stops…Works pretty good…Call it a “Glaze Beaker” if you like…

My comment about comparing the cost of machining to replacement is based on who is doing the cutting.
At a dealer the flat rate time is generally around .8, give or take, hours for machining a rotor. Multiplying that X the shop hourly flat rate charge can run the cost way up there.
However, some places may send them out to an auto machine shop who will do them for much less based on their business model. Charges can from 10 to 20 dollars a rotor and this can be cost effective.

There’s also a caveat. Some places that machine rotors will try to zip through them very quickly and this often means peeling a lot of metal of in as few passes as possible and skipping the most important cut of all; the final one which should be done on slow and is time consuming.
A visual inspection of a cut rotor will generally reveal right off if the slow cut was not done, if a chatter band was not used, etc, etc.

I generally take a look, or if it is someone I trust, I decide then. If there is any doubt, most of the time I will replace an axle at a time. Once I am that far along, would just as soon do it all. Modern rotors don’t really have that much metal to them so I figure by the time my brakes (your braking needs and style may be different) need to need work, I figure the little difference in effort/cost, I will just buy a new set.

In addition to not turning properly mentioned by ok4450 I have seen bad jobs because the shop or store was using worn bits, that was my point, the bits have gone way up in price the last few years.