Do you resurface OR replace your rotors when changing pads?

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tripower

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I have had some vociferous debates with folks over this issue.
I have always resurfaced (if still within spec) OR replaced my rotors when changing pads (Never just replacing pads alone). The Bentley manuals for nearly every model BMW that I can find back me up on this (Please correct if this isn't accurate). What is your experience and opinion on this issue?
 
In my younger years I used to do pads alone. I often experienced pulsing and grooving of the discs before the pads lived little more than half their useful life. Braking effect ended up not optimum as well. In my opinion, if you want optimum braking performance (= safety), always change or resurface rotors. Local shops out here do them for about $15-$20 ea. Even if you gain only a small percentage improved performance, isn't it worth it? If your rotors are worn beyond factory limits for resurfacing, then it's time to trash 'em..... My 02 cents.
 
To replace the disks (rotors) every time you change pads is a very expensive option. (Yorkshireman living in Scotland speaking :wink: )
I just change the pads, but I do check
1.. Minimum thickness - change if below limit
2.. Any cracks - change if spotted
3.. Run out (wobble), with a dial gauge - investigate, remount, change if not cured.

By following the above I don't think I have compromised the braking performance of any car I have had.

Here in the UK nobody resurfaces disks anymore, probably because the labour costs involved to get them off, recut and put the on is probably more than just putting new disks on.

Malc
 
To replace the disks (rotors) every time you change pads is a very expensive option. (Yorkshireman living in Scotland speaking :wink: )
I just change the pads, but I do check
1.. Minimum thickness - change if below limit
2.. Any cracks - change if spotted
3.. Run out (wobble), with a dial gauge - investigate, remount, change if not cured.

By following the above I don't think I have compromised the braking performance of any car I have had.

Here in the UK nobody resurfaces disks anymore, probably because the labour costs involved to get them off, recut and put the on is probably more than just putting new disks on.

Malc
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It's an even more expensive proposition in terms of your safety NOT to resurface rotors when changing pads. The rotors (and other parts such as your wheel bearings) demand closer inspection when taking your rotors off the car for resurfacing or replacement.
 
why resurface?

I'm with Malc on a subjective basis - unless someone has hard numbers that prove otherwise. We owned Fiats and Lancias for years (Squadra Corsa?), all with 4 wheel discs, and routinely changed pads without resurfacing. The few times I did, it took a few days for them to "bed in" to perform as well as they had been. And when inspected months later, they looked exactly the same as before resurfacing. Maybe the grooves are part of the equation, as they do add up to extra surface/contact area. Anecdotal for sure, but that's been my experience.
 
Re: why resurface?

I'm with Malc on a subjective basis - unless someone has hard numbers that prove otherwise. We owned Fiats and Lancias for years (Squadra Corsa?), all with 4 wheel discs, and routinely changed pads without resurfacing. The few times I did, it took a few days for them to "bed in" to perform as well as they had been. And when inspected months later, they looked exactly the same as before resurfacing. Maybe the grooves are part of the equation, as they do add up to extra surface/contact area. Anecdotal for sure, but that's been my experience.
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The Bentley manual's (as well as others) state that for optimal braking performance and pad longevity rotors should be resurfaced OR replaced when pads are replaced (depending on the particular vehicle, for example I believe with the M3 it is recommended that the rotors be replaced).
 
Changing rotors

Its a need versus cost thing.

I recently replaced rotors (discs ) because they were cracked and were causing the car to judder under braking. Over the years, I have done a few sets of pad replacments only where the discs got the once over and looked fine, so were left on.

The CSi passed all inspections, including braking efficiency, and I didn't ever feel braking performance was being compromised.

I think its fact that discs will always outlive pads - just because of what materials they are both made of?

It's easy for manuals or dealers to say replace eveything - they aint paying for it. Next it will be " replace wheels / tyres / rotors / pads / pipes / fluid every time!" Not for me................

Having said that , I am a Scotsman and we as a race have often being descibed as "tighter than a ducks ass - and that's watertight!"
 
Of course the manual is going to tell you the 100% "right way". Which is resurface or replace the rotors every time. If nothing else, it deglazes and cleans them

If the rotors are warped or grooved they should be resurfaced if they remain in spec. If they are not warped or grooved, I have replaced just the pads. There is a bedding in period. But, there is with new rotors and pads also.

There is a real, old fashoned, parts store here in Pasadena that resurfaces your rotors for free if you buy pads from them.

I honestly think that the real reason why most dealers won't do it any more is simply that they can make more money by selling you new rotors, bearings, and seals, than by charging you to cut the rotors. There is also one less piece of equipment to buy. And you don't have to train anyone how to use it.

Just always make sure you err to the safe side with brakes. If in doubt, change it out.
 
so that's what DP looks like, damn all

Last time I priced rotors they were no way gonna cost under 200 for four, and not under 200 for two either.

I mail ordered a set of four Balo rotors, it cost less overall, but shipping eat me up.

Changing pads? then just scuff up both sided of the rotor and reinstall them really really clean. No greasy fingerprints anywhere.

For new rotors, I degrease, then leave 'em in the weather for a weak. Wipe off the light brown dust with a bit of Scothbrite and water, and wallah! etched rotors the will quite nicely break in a new set of pads, thank you.

And no one pre-bakes their pads to be sure they aren't the culprit, off-gassing who knows what when they are first heated up... How about 350 to 400 degrees for 20 minutes, chaps?
 
Wrong, sort of. BMW rotors are intended by design to be inexpensive enough to replace. Period. Resurfacing of these rotors leaves them close if not beyond that wieerd "minimum thickness" spec, thinner rotors will warp, surge and/or crack more readily than new (duh!) Pads alone makes no sense either. Everyone on this list wants every one of our cars to be valued high, right? So why the hell does ANYone balk at spending 200 bucks (or less) for rotors ? Hell-if-I-know!
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I agree -- I always thought the debate was resurface vs. replace -- not just whether to shove new pads in on your old rotors. That's the approach 2002 owners take -- :roll: I always just replace mine. Mesa lists stock replacements for $60 each on-line -- and I can get them cheaper locally (for anyone close to San Diego -- Inter Auto in Kearny Mesa is THE place!)
 
It's an even more expensive proposition in terms of your safety NOT to resurface rotors when changing pads. The rotors (and other parts such as your wheel bearings) demand closer inspection when taking your rotors off the car for resurfacing or replacement.
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Wrong, sort of. BMW rotors are intended by design to be inexpensive enough to replace. Period. Resurfacing of these rotors leaves them close if not beyond that wieerd "minimum thickness" spec, thinner rotors will warp, surge and/or crack more readily than new (duh!) Pads alone makes no sense either. Everyone on this list wants every one of our cars to be valued high, right? So why the hell does ANYone balk at spending 200 bucks (or less) for rotors ? Hell-if-I-know!
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First, dude you really need to appropriately size you sig image. It is WAY TOO big. Second, resurfacing is acceptable if within spec. How much metal do you think they are removing during a resurfacing? This is stuff that has to be measured with a micrometer. And if it is within spec then the manufacturer of the rotor has determined that it is not at risk of warpage and cracking, which is why there is a spec in the first place.
 
I agree -- I always thought the debate was resurface vs. replace -- not just whether to shove new pads in on your old rotors.
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You would be surprised. A lot of young guys are getting into the game and they just are not taught any better, so they are just replacing pads and not even inspecting the rotors much less resurfacing or replacing.
The whole idea behind this is to remove the rotor, inspect the rotor, inspect the wheel bearings, inspect your caliper and brake hoses, replace any worn out parts in this area, then resurface OR replace your rotors. That is a thorough brake job (don't forget to bleed the fluid).

I saw a set of calipers on "Speed" where you could pop the pads without even removing the caliper. What's the point?
 
.....I saw a set of calipers on "Speed" where you could pop the pads without even removing the caliper. What's the point?
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There isn't any...
You don't have to remove that calipers to change the pads on my 1962 MGA, 1986 Land Rover, 1974 BMW 2002Tii So the idea of replacing pads without removing the caliper is nothing new. sounds like a sales pitch to me

Malc
 
It's an even more expensive proposition in terms of your safety NOT to resurface rotors when changing pads. The rotors (and other parts such as your wheel bearings) demand closer inspection when taking your rotors off the car for resurfacing or replacement.
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Wrong, sort of. BMW rotors are intended by design to be inexpensive enough to replace. Period. Resurfacing of these rotors leaves them close if not beyond that wieerd "minimum thickness" spec, thinner rotors will warp, surge and/or crack more readily than new (duh!) Pads alone makes no sense either. Everyone on this list wants every one of our cars to be valued high, right? So why the hell does ANYone balk at spending 200 bucks (or less) for rotors ? Hell-if-I-know!
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First, dude you really need to appropriately size you sig image. It is WAY TOO big. Second, resurfacing is acceptable if within spec. How much metal do you think they are removing during a resurfacing? This is stuff that has to be measured with a micrometer. And if it is within spec then the manufacturer of the rotor has determined that it is not at risk of warpage and cracking, which is why there is a spec in the first place.
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Sheesh, were you just trolling for a debate? Wouldn't a dial caliper or a piece of string to measure things like rotor thickness be adequate? Why measure at all if (like I pretty much said) I am replacing my rotors? MY POINT wasn't to engage your highness in an anonymous bbs debate, it was to answer your question, "Change rotors, don't "resurface"...they are cheap enough and work best when at full thickness. Sorry my editorial comparing perceived value of these old cars to the tight-wad attitude of self-servicers got your panties in a bunch, or was it that "too big" photo of some dude / shaman-type that bent your nose?
 
This is a great topic but not worth fighting over.

Seriously, on my 87 Volvo common wisdom was that rotors cannot be cut (too thin?), so they are replaced or left alone when replacing pads. Things got trickier as Volvo transitioned from asbestos pads to organic. People complain about brake noise, they make the pads softer and they last lttle. Soft pad means it makes sense to leave the rotor alone when replacing them, but my mechanic is a perfectionist and prefers new rotors. The moral of the story? Replace one rotor and cut the other so we can please everybody...
 
This is a great topic but not worth fighting over.
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I disagree. Brakes are serious business. They are the mechanism that stops the car and if that isn't worth discussing in-depth I don't know what is.

But you are correct, great topic.
 
I don`t replace rotors (or discs as we call them in the UK) every time I replace the brake pads. I have never heard of the need to replace rotors every time pads are changed. It sounds a bit like changing the cam every time you do the valve clearances.... I measure them with a caliper and check for scoring and if they are with in spec I leave them alone. I have always found BMW pads to be pretty soft and tend not to wear the discs.
I have just purchased a set of genuine front discs off e-bay for £26 a pair for when I need a set.
Have any of you guys ever used performance brake pads ? in the UK `green stuff` brake pads seem very popular and are a lot harder than standard pads but would imagine they are a lot harder on the discs.
marc
 
Brake pads more info

Snip.......
Have any of you guys ever used performance brake pads ? in the UK `green stuff` brake pads seem very popular and are a lot harder than standard pads but would imagine they are a lot harder on the discs.
marc
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Marc as far as I am aware "green stuff" pads use a different material mix to "regular" pads.

Start of rant....... :roll:

There is some confusion over pads being "hard" and "soft". While in some respects this is true it is the ability of the pads to shed heat that is mixed up in all of this.

A "standard" pad is designed to warm up quickly to it's most efficient operating temperature, ideal for stop start traffic and "average" driving conditions
However if they get too hot they start to "gas" where a film of gases builds up between the pad and the disk - this is experienced as brake fade, which can be very frightening.
By using a "harder" or "higher" temperature pad the heat is dissapated faster and thus the temperature takes longer to build up, delaying the onset of fade.
The downside of this is that it takes longer for the pads to reach the otimum operating temperature, thus when cold they take more effort to stop the car.
There is no standard on the grading of pads and thus I can only speak from the ones I know.
Mintex will make pads in various grades starting with code 1144 which is the "softest" or "coolest" pad they make - standard production car - up to 1199 which are the hardest or hotest pads, shame the nomeclature seems the wrong way round!
Anyway after much experimenting with my Lancia Delta Integrale I found the best combination for stage rallying is 1177 on the front and 1166 on the rears, this gave a good balance for the stages with the ability to left foot brake.
For tarmac work these were useless and would fade quickly, I ended up with 1199 on the front and 1177 on the rear. But these were quite scary until warmed up.

Then the whole isssue of fluild can up as the amount of heat put into the caliper assembly is amazing and can cause the fluid to boil, leading to a complete loss of pedal....... I ended up using racing fluid which is like DOT 5 standard, but has to be changed every year as it goes "off" pretty quickly

To summarise

1.. Standard pads are fine for day to day driving conditions
2.. Upgrade material if your track thrashing
3.. Use the handbrake! Avoid holding the car on the brakes if they are hot, it causes local hot spots which can cause the disk to warp.
4.. Drilled or grooved disks are fine for racing / rallying, but don't waste your money on them if your car is a daily driver.
(Yes I know Porsche have them on standard cars. A waste unless your Autobahn storming)

End of rant...... :oops:
Malc
 
breaks and stuff

Interesting stuff Malc, you are a tower of knowledge. You mention that Porsche disks are drilled as standard and mine on my old 930 are warped yet again. When I replace them would I be better to replace with out using drilled disks ? Or is this not the reason their warping ? Its been a problem with 930`s since the cars were new and most Porsche specialists now skim the disks on the car when the pads are changed.
Another quick one for you, when replacing rubber brake pipes any real advantage going for braided lines ? When I ever get a `new` old car I normally reseal all the callipers, replace the pads and swap over to s/steel braided brake lines (so far they have been cheaper than original ones) and replace the fluid with dot 5 fluid.
Marc
 
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