Replacing pads versus replacing pads and rotors

[Captain Blood]

So I need new brake pads on my S3. Most of the places I talk to say most cars now you have to change the pads AND the rotors. $1300 vs $350. Seems silly and overly expensive. I did the pads myself on my 135. Does anyone else here have a car where it is recommended that Not just the pads, but the pads and rotors be replaced as a matter of common policy, not just because the rotors might be warped?

[Efthreeoh]

I don't know about Audi, but BMW I always replaced pad and rotors as a set. I do all my own brake work, so the labor savings easily justifies new rotors. With BMW, the rotors are soft and never stay in spec through the second set of pads.

A proper brake refurb dictates removing the rotors to have them resurfaced so there should be no extra labor cost to remove and replace the rotors using new parts. And the price for a new rotor is just 60% more than the cost to have the rotor resurfaced.

But rotors are $900 for an S3?

[ga9213]

It was significantly cheaper to resurface my rotors than to replace them on my M40i. You should only need to replace if there is not enough material to turn them.

[Boomer 2019]

BMW dealers and I assume others as well will tell you that it is necessary to replace your rotors whenever you replace yours pads. This is absolutely not the case, and is purely a sales pitch. A car which is driven on the street only will probably go through 3 or 4 sets of pads during it's lifetime, and not need it's rotors replaced for many, many years. Probably longer than most people keep their cars, and maybe longer than the functional lifetime of the car itself. Rotors are tough. Damaged rotors are a separate issue.

I have tracked my cars a lot over the years using many dozens of sets of track pads which are much tougher than street pads, and have never had to replace a rotor. Of course given enough time and use everything eventually wears out, but I have not reached that point with my rotors yet. I say this to point out the fantasy that rotors need to be replaced regularly. They do not.. barring damage.

All rotors are stamped with a minimum thickness below which it is recommended that they be replaced. Even this is not a hard and fast rule.. think of it as a "use by date". The only time a rotor needs to be replaced is when it has been worn to below the minimum thickness. A reputable garage can measure them for you, ideally when you have to take the wheels off for some reason. You will then have unbiased information from someone who is not trying to sell you something.

[Alfisti]

Problem is when i get a price to resurface the rotors it's damn near 75% the price of a spanking new set.

[spielnicht]

So, you're saying that BMW "used" to say it was OK to replace just the pads when they were covered under the first 4 years free of charge, but now that is no longer the case, they advise you change both pads and rotors at same time?. Something is fishy here. I call BS.

[unluky]

Depends on your version of "OK". Most will say do it all and use premium parts. I have replaced just pads many times in my life on many different cars. Likewise I have replaced rotors without pads to, but I do always do them in sets (per axel, not always all 4).

Kind of a personal opinion kind of deal, you will get the full spectrum here. I also do all my own, so as stated above - that pays for a LOT of parts to just do it while you are in there. If $ is an issue - replacing pads only is usually fine - just inspect everything while you are in there and if in doubt - replace.

[Ximian]

Changing both is recommended because the shop can avoid dealing with customers complaining about problems that can occur when replacing just the pads.

The best way to determine if the rotors need replacing is if there is a lip around the outside of the rotor. That means the rotor surface has worn enough to be getting close to minimum thickness and with some aftermarket pads, they might not fit well.

[M5Rick]

If the disc surface is smooth then okay to fit new pads as they'll bed in nicely but if liney and rough they'll be hard to bed in and if discs are lipped a lot then yes discs need replacing and pattern discs are fine to use too.

[DrFerry]

Resurfacing drilled, cast with holes, or slotted rotors can be done providing the rotors are not at the minimum thickness.
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[Redd]

There is no need to change pads and rotors as a set. This is purely a way for a service center to get more money from you. Change rotors if they are worn past the minimum recommended thickness.

There is also no need to resurface a rotor unless it is warped or has vibrations. If you drive the car hard or go to the track, it is almost certain you will see surface crazing, wavy patterns or blueing on the rotor surface. If you have cross drilled rotors, it is almost certain you will see small cracks propagating out from the drill holes. This is normal. As long as two cracks don't join together there is nothing to worry about.

[Mandi90TT]

No need to change rotors with pads.

I used to track my M4 extensively, and used race pads on the track, street pads on the street. Rotors are just fine.

It's purely a sales tactic.

[DocL]

Last month I was told by my BMW service advisor that I needed new front pads. I asked about replacing the rotors and he said it was not necessary at this time. Like many others here, I did the pads myself and saved a ton of money, plus I installed the Akebono pads and I have almost zero brake dust now. I also don't notice any difference in the stopping power now that they are fully bedded in.

[kring]

Depends on age/miles of the rotors, they key is being in spec. BMW Recommends in their technician manual to resurface if there is enough rotor to do and keep in spec.

However, it ALWAYS best to replace both at the same time, but as you pointed out it cost a bit more. This will give you the best performance, life and quiet stable braking for another pad lifetime.

Rotors develop a resonant frequency and that marries the pads as they break in together. Quite often a resurfaced rotor and a pad will not develop into a harmonic match and you will forever have brake squealing, the degree depends on how harmonically they are out of sync. Or you may get lucky and they align. I have turned maybe 10 sets of rotors in my life and I’d say only twice it worked out perfectly… the rest either had squeal, relatively quickly they developed uneven stopping or accelerated wear.

If you can get them turned for nothing, you could try it.. but keep in mind that id its a bust, you may now be out another set of pads if you have to go for the full rotors the second time. You wouldn’t want new rotors with used bedded pads. Could you? Of course you “could” do that… but you might as well trade the S4 in for a prius at that point.

Give your car the love that it gives you and do a proper brake job on it.

[Redd]

First time I've heard of 'harmonic matching' pads and rotors. Some pads squeal, some don't. Some copper slip helps if it does squeal.

[cooolone2]

Hahaha, hoarmonic balancing of rotors to pads... Well that's a hoot! Guess when they're out of tune it's time to change em'

Dude, that's seriously hysterical!

It's just simple... But shops opt to sell you ice in winter and maximize profits, and also eliminate complaints.

Fact is, the rotor material has a minimum thickness for the braking to be effective within tolerances of the pad depth as well. Combined, they will exert pressure to stop rotating mass. The pads wear from friction and so does the surface of the rotors. Depending upon the pad material, they can both wear at different rates (mileage). The thickness and also the surface condition of the rotor will determine if replacement is necessary. Most shops won't even check the rotor thickness or whether or not it's within tolerances or even if they're true, ie, not bent! Most shops will sell secondary inferior rotors that are already at low thickness tolerance and is why they don't last. They basically suck! But if you do your research and get quality brake rotors and also pads, they'll last and last, and last. All depending upon dirivng style and use of course. If there's surface irregularities and the shop is knowledgeable and has the equipment then there's nothing wrong with cutting rotor surfaces to a smooth finish within tolerances! Again, most don't bother any more and just make the sale with the old You Gotta Do Both BS!

Have fun!

[zx10guy]

I have changed brakes across multiple makes and evolved into the current guideline I follow. I won't ever change the rotors unless the surface of the rotor dictates it or if there is vibration felt under braking. Otherwise, it's always just pads.

Resurfacing of the rotor is a waste in my opinion. Yes you'll have a flat surface again. But what hasn't been mentioned is resurfacing removes metal off the rotor. You're decreasing the thickness of the rotor which will make the rotor even more prone to issues in the future. Particularly warping as the amount of metal is what is important in the amount of heat capacity the rotor has.

[ga9213]

Originally Posted by kring

Depends on age/miles of the rotors, they key is being in spec. BMW Recommends in their technician manual to resurface if there is enough rotor to do and keep in spec.

However, it ALWAYS best to replace both at the same time, but as you pointed out it cost a bit more. This will give you the best performance, life and quiet stable braking for another pad lifetime.

Rotors develop a resonant frequency and that marries the pads as they break in together. Quite often a resurfaced rotor and a pad will not develop into a harmonic match and you will forever have brake squealing, the degree depends on how harmonically they are out of sync. Or you may get lucky and they align. I have turned maybe 10 sets of rotors in my life and I’d say only twice it worked out perfectly… the rest either had squeal, relatively quickly they developed uneven stopping or accelerated wear.

If you can get them turned for nothing, you could try it.. but keep in mind that id its a bust, you may now be out another set of pads if you have to go for the full rotors the second time. You wouldn’t want new rotors with used bedded pads. Could you? Of course you “could” do that… but you might as well trade the S4 in for a prius at that point.

Give your car the love that it gives you and do a proper brake job on it.

Where did this information come from?

[Mandi90TT]

Originally Posted by ga9213

Where did this information come from?

His ass.

[tranquility]

What a joke. I knew something was up when they told me to change rotors w the pads but didn't know enough to resist. OK, so now only pads unless there's actually something wrong w the rotors.

[shawnhayes]

Originally Posted by Mandi90TT

His ass.

HAHAHAHAHAAHA.

Mostly agree with the opposing view here. Replacing the pads will be fine 99.9% of the time, but you have to check the rotors. KNOW what the "needed" replacement characteristics are (weight or thickness) so you know when the rotors need replacement.

Shawn

[kring]

Originally Posted by Mandi90TT

His ass.

HAAHAHAHAH…. So funny, yuk yuk.

What do you think a squeal is? Please share an explanation of what’s happening that produces that noise.