To service rotors or not??

[ThunderGod]

ive done brake work before and just did on my sisters car and she just wanted to put front pads without servicing the rotors..I always like to have mine done but my question is..isit really neccessary to have the serviced? Ive read online as long as no major grooves it be ok not too but some say no have them serviced..Is there a right answer to this,hope Eric can shed some light on this or anybody who wants to answer…

Topic

[Dustin Hicks]

[quote=”ThunderGod” post=47852]ive done brake work before and just did on my sisters car and she just wanted to put front pads without servicing the rotors..I always like to have mine done but my question is..isit really neccessary to have the serviced? Ive read online as long as no major grooves it be ok not too but some say no have them serviced..Is there a right answer to this,hope Eric can shed some light on this or anybody who wants to answer…[/quote]

If a fingernail scraped across the rotor/drum doesn’t catch, or there aren’t major visible grooves, you can ‘get by’ just replacing the pads/shoes on your own car, no one else’s. Otherwise the rotor/drum must be resurfaced/replaced. Keep in mind though that if nothing is done to the rotor/drum, braking efficiency, and pad/shoe life will decrease. Because of that efficiency loss, if there are problems later, legal liability can come back on the mechanic.

I never replace pads/shoes without resurfacing/replacing the rotor/drum at the same time just because of that. Most really top notch shops won’t either. Not because we want to inflate the cost, but for the customer’s and the public’s safety. That’s also one of the reasons why both ends of the axle have to be done at the same time.

[EricTheCarGuy]

To be honest if you don’t have a pulsation I don’t recommend machining rotors or drums. The main reason is that when you machine something you take metal away. The more metal you take a way the less able the rotor is at dissipating heat. In fact I know that Honda does no recommend machining unless there is a pulsation for I believe this very reason.

[college man]

I Put new pads on the back if the rotors are smooth.
The fronts I replace.No machining.

[Matthew Ross]

I always change the front rotors at the same time as the pads. Modern rotors weren’t really designed for machining (at least that’s what a lot of professionals tell me). They have become cheap enough where most people just replace them.

I have personally experienced problems with replacing just the front pads. I did it once, and within a few days my steering wheel shook under braking. Essentially, the wear “pattern” of the old rotors doesn’t exactly match the perfectly flat surface of the new pads. I had to take everything back off and install new rotors anyway. That problem doesn’t always happen, but it is possible. Even the local mechanic told me that he sees that from time to time.

Here’s a quote from tirerack.com on this exact question:
“Installing new brake pads with used, unturned, or worn rotors can also cause warping due to the uneven overheating. Most used rotors will have irregular, grooved wear patterns on the surfaces. Mating this with the flat surface, a new brake pad will generate heat and friction only on the raised areas of the brake rotor causing those sections to heat faster than the recessed areas not touching the pads. Any brake pad transfer film from the previous set of pads can also affect the new pad’s ability to bed-in properly. The residue on the rotor can quickly lead to hot spots on the surface that can result in noise, vibration, dust, and warping problems.”

[dave]

as a caveat to what mr. car guy has mentioned, you should clean your rotors w/ every good brake job. you should cut your rotors only when you experience pulsation.

[ThunderGod]

maybe ya should make it a video topic Eric? it was on 2004 chrysler concorde now i gotta do the back so i prob wont have the rotors turned..

[EricTheCarGuy]

[quote=”matthewross1987″ post=48704]I always change the front rotors at the same time as the pads. Modern rotors weren’t really designed for machining (at least that’s what a lot of professionals tell me). They have become cheap enough where most people just replace them.

I have personally experienced problems with replacing just the front pads. I did it once, and within a few days my steering wheel shook under braking. Essentially, the wear “pattern” of the old rotors doesn’t exactly match the perfectly flat surface of the new pads. I had to take everything back off and install new rotors anyway. That problem doesn’t always happen, but it is possible. Even the local mechanic told me that he sees that from time to time.

Here’s a quote from tirerack.com on this exact question:
“Installing new brake pads with used, unturned, or worn rotors can also cause warping due to the uneven overheating. Most used rotors will have irregular, grooved wear patterns on the surfaces. Mating this with the flat surface, a new brake pad will generate heat and friction only on the raised areas of the brake rotor causing those sections to heat faster than the recessed areas not touching the pads. Any brake pad transfer film from the previous set of pads can also affect the new pad’s ability to bed-in properly. The residue on the rotor can quickly lead to hot spots on the surface that can result in noise, vibration, dust, and warping problems.”[/quote]

That’s not true. I think they’re just being lazy or they don’t know how to machine the rotors properly. Every rotor has a minimum spec and it can be machined to that. I’m not saying that modern vehicles don’t use much cheaper materials than older models but as far as brakes go you should be able to machine the rotors and if they are in spec you should be just fine. In fact, the best way to do it is with an on-the-car brake lathe. This helps eliminate any run out in the hub and yields the best results as far as rotor machining.

Tire Rack is also way off on installing pads without machining or replacement. The rotor has no idea that new pads have been installed so how would that result in overheating and warping? New pads will wear to old rotors. I’ve installed hundreds if not thousands of brake pads without machining rotors and up to this point I have not experienced anything close to what they described.

I should see if I could dig up Honda’s statement about NOT machining the rotors and just replacing brake pads.

[Matthew Ross]

Thanks for the info. I’ll ask a different mechanic to machine the rotors next time. After one mechanic told me to buy new rotors, I just took his advice without checking elsewhere. Sorry if I’m spreading misinformation…

[Charles]

The only time I have had trouble with brake jobs preformed by others on my car I attribute to the improper tightening of the lug nuts. My symptoms were that I observed brake pedal vibration about a week or two after the work was done. The cast iron rotors are very prone to warp if the bolts are tighten wrong. I have never had a problem whether the drums were turned or not when I did the work myself and torqued the lug nuts.

[steven jacobsen]

I usually replace rotors since they are so cheap. If they are the more expensive ones then I will machine them. This is mostly for noise from that rust ridge that is always there after a while. If the customer refuses to spend the money I will just reuse the rotors as is, as long as they measure out good and there are no groves etc. If they are groved or undersize then they have no choice.
As for an earlier comment about liability we have a strange system here. If you are not a liscenced mechanic and it goes terribly wrong you can not be prosicuted, just taken to small claims court for the cost of the labor only, which is never worth it. If you have a mechanics liscence and you screwed it up then you can be prosicuted for any resulting damage of the car and whatever the car hit, and negligence causing death if that happens, thats 10 years in prison right away. Then anyone involved can sue the hell out of you. Someone can persue an unliscenced person but it usually doesnt go anywhere.

[EricTheCarGuy]

[quote=”matthewross1987″ post=49550]Thanks for the info. I’ll ask a different mechanic to machine the rotors next time. After one mechanic told me to buy new rotors, I just took his advice without checking elsewhere. Sorry if I’m spreading misinformation…[/quote]

No worries man. That’s not how this forum works. We all try to keep the information as relevant as possible. We all have different experiences and I know many opinions are based on that very thing. Don’t be afraid to voice those opinions here as they are always welcome.

[Author]

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