Replace Brake Rotors in Pairs: Does anyone ever ask why?

[IntegrityAutoCare]

Ok, before you all begin assaulting and attacking me for being a half ass mechanic...let me explain:

 

I AM NOT posting this because I make a practice of replacing only one brake rotor or because I want to argue a case in favor of such practice. I, like most of you I imagine, have always been taught and trained to replace/refinish brake rotors ONLY in pairs. NO EXCEPTIONS. Or else the world will explode! haha...ok, well, maybe not the world I guess. But presumably something really bad will happen.

 

But do any of you ever get asked by the customer WHY you had to replace both rotors when only one was "bad"? What do you tell them? Do you just make something up, spout off the same generic response that your old boss/instructor/teacher/mentor, etc. told to you about how you need rotors of the same thickness for equal stopping force blah blah blah or do you actually KNOW the concrete scientific reasoning behind this "universal truth"? I myself am a little fuzzy on the details. It seems like I am constantly having to explain to customers that I had to replace BOTH brake rotors, but when they ask me why, I don't really know exactly. I'm hoping you guys can help me out with either a detailed explanation or a link to some technical artical that will explain it.

 

I will also accept personal experience as evidence such as "I tried replacing only one rotor one time and the customer was back the very next week in a full body cast with his lawyer pushing the wheel chair."

 

Ready: GO

[Jeff]

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[xrac]

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[bstewart]

I was taught that it maintains even braking. If the old rotor is thinner it will build heat and thus fade faster than the new one. That in turn will develop a brake pull that could cause loss of control.

I believe this is the correct answer, although I think the potential safety issue is very minimal IMO. Don't forget that you almost always have a slight brake pull due to the crown of the road.

I also think that refinishing/replacing in pairs is to keep both sides wearing at the same rate, so if one is worn out, the other will be soon to follow.

That being said, I work at a heavy duty dealership at the moment, and we regularly replace single rotors on commercial trucks with disc brakes if the other is still within spec.

 

If I was in your situation, I'd measure the "good" rotor, estimate how much time is left before it fails, and inform the customer.

Educate them to the cost of fixing it now vs returning for another appointment where you have to disassemble that wheel end again.

Obviously recommend changing rotors in pairs, but if they don't want to, I wouldn't press the issue.

If the rotor will last until their next scheduled maintenance, maybe they'd want to have it replaced then, always give your customer the choice.

[IntegrityAutoCare]

I am not a car guy but I have worked in this business for 15 years.

This statement left me scratching my head....

[mmotley]

This is a really good question. I would say 'technically' you can replace just 1 rotor. After all, if the other one is within spec... it's within spec! I would say 'replacing as a pair' is probably more of a good practice, IE Jeff - " If the old rotor is thinner it will build heat and thus fade faster than the new one. That in turn will develop a brake pull that could cause loss of control" .

 

I would also agree, now that I think about it, that I don't recall reading or hearing any official material say that they should be replaced in pairs... Maybe a quick google search would turn something up?

[xrac]

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[Dee1234]

I think the brake pull is a good answer but could lead to the question of if you think its unsafe then why would you perform that practice and open yourself up for potential law suit after admitting to cust that it could cause loss of control. I usually play the economic card...saves money to do it now. Then let cust decide, assuming rotor is within spec.

[uniautoser]

i always use things that people can relate to like the LP record and the sun analogy. Heat will warp a record like heat will warp the rotors.. so in this case i tell customers that brake rotors should be replace together because they both have to be the same thickness and then i tell them if they would you ever consider buying only one shoe. if only one shoe gets worn will they just buy that warn shoe? after that what can you say "I under stand, go ahead and replace them.." Done "Change them Bob..."

Edited April 11, 2016 by uniautoser

[kars]

I will do one rotor as long as I turn both the rotors for a matching finish. Of course the other rotor needs to be within spec after the refinish. This scenario does not come along often for me.

[carolinahigear]

i always use things that people can relate to like the LP record and the sun analogy. Heat will warp a record like heat will warp the rotors.. so in this case i tell customers that brake rotors should be replace together because they both have to be the same thickness and then i tell them if they would you ever consider buying only one shoe. if only one shoe gets worn will they just buy that warn shoe? after that what can you say "I under stand, go ahead and replace them.." Done "Change them Bob..."

Most of my clients have never played an LP Record, and if I used that term most would not have a clue what I was talking about. I have not seen one out of its protective sleeve in well over 30 years!!

 

With that said, When I give a price on performing the brake job on a vehicle that is in the shop with wheels off and inspection finished, I give the price for the brake job. I do not mention pads or more importantly, rotors. I tell them that the price for the front brakes is $388 for example, and that the rear brakes are ok at this time. I would say that on 80% or more of my brake jobs I install new rotors. We do not machine rotors.

[HarrytheCarGeek]

Replacing rotors in pairs helps keep consistency in maintenance, and safety. By doing so you remove the guessing game of when you need to do it again, and basically the customer trades some dollars for convenience and certainty.

 

Kinda, doing light bulbs in pairs, you know, I am sure you had a customer come in for a burned out headlight bulb and a few weeks later he comes in again for the other one.

 

There are customers that if you explain to them that they may have to comeback for the other bulb, they dispense with the inconvenience and tell you to do both.