So I'm having my mechanic flush my brakes and replace the pads. He said that they absolutely will not replace the pads unless I either resurface or replace the rotors at the same time. I've done research on this, and what I find is conflicting. Some places say that unless the rotor is worn, it's best just to replace the pad. Other places agree with my mechanic. I know that I have heard that resurfacing the rotor isn't a great idea as it makes it thinner. As a result, it is more prone to warping, and able to absorb less heat. This makes sense to me. My mechanic feels that even if the rotor is in good condition (which mine are), the new pads will never seat in and work optimally unless the rotor has a fresh surface. Now, I'm certain that most people who pay thousands for a BBK that track their cars regularly are not paying for new rotors every time they replace their pads. I don't have a BBK, they are just powerstop Z23 rotors. Also, I'm not replacing my pads because they're worn. I'm replacing them because I'm not happy with their performance. I need something that isn't going to fade like hell after the first time I brake from 100+ mph.down to 35 mph. I do trust my mechanic. I also know for sure that he isn't trying to scam me as I always provide my own parts, so I only pay for labor. Since I have found a good deal supporting both sides of this argument, I was curious what you all think? Is it necessary to replace or resurface your rotors every time you replace the pads?

 

For years on daily drivers I have changed brake pads without rotor attention. If your vehicle stops without pedal pulse and jerking but the pads are thin I would change just the pads (but I never worry about stopping from 100 mph). On daily drivers I have bought rotors from auto chain stores that were made in Mexico or China that worked fine. Did the same on older Corvettes but haven't touched brakes on my 2002 vert. Bought it with 47k miles 8 years ago, 59k now, I suspect original owner changes them once because they work fine. It ain't broke so I won't fix it.

 

I NEVER surface rotors when I change pads. Since I track my car I try to change pads when they are about 50% of new pad thickness because on those 100 + down to 35 braking zones the pad material is an insulator between the hot rotor and the caliper pistons and brake fluid. My last set of OEM style front rotors finally got a little thin after 40,000 miles, four pad changes and 16 track days so they were replaced. Thin rotors have less heat absorption capability, another reason not to surface them.

If you track the car and the pads get thin, the caliper piston rubber dust bellows will get burned to a crisp-- ask me how I know.

A couple of years ago at Laguna Seca, I measured front rotor temperature at 550 degree F---- AFTER a cool down lap and parking in the paddock.

For track use you must do the pad manufacturer's break in ahead of time for new pads.

In my view, most "warped rotors" are an old wives tale. StopTech explains:

https://centricparts.com/getmedia/af...rakeJudder.pdf

As far as pads go, I have been perfectly satisfied with Hawk HP Plus pads-- plenty of braking authority on street cold or after the tenth brake down from 110 to 35 on a hot day. Dust- yes. Squeal- yes, turn up the sound system.

 

Not on my personal cars. On a customers car it's either cut rotors if they're thick enough or replace them. It's so you're sure the rotors are true and the car won't have a brake pedal pulsation. You don't want them coming back upset.

 

Measure the thickness and decide from there. Definitely not 100% necessary. Maybe a good idea if you're changing pad compounds, though.

 

I once read, I think it was in an old hot rod magazine, that most rotor turning machines have a cutting tool in such poor repair, that, instead of cutting a new flat surface, it actually traces a tightly spaced continuous spiral groove, much like a vinyl record , when inspected under magnification. So it is actually cutting a surface that promotes pad wear, instead of a flat clean one for optimal braking. . one needs a blunt tip rather than a point on the cutting tool, which provides no overlap when cutting.

I don't have enough experience to talk much about brake service for street use, and know only enough to not offer advice about race brakes, but I am a pads only guy. your mechanic is probably requiring the rotors for the same reasons the above poster stated, to lesson any chance of profit eating be backs. it is pretty easy for corrections on previous repairs to shred any profits from the failed repairs, while also trying up the space needed for new profits. .

or he might feel a need to avoid some kind of legal exposure by following old conventions that were always needed with drum brakes, where they were always turned just to make sure the things ere returned to round after all the heat cycles.


I would just measure the rotors to see if they meet specs, and replace as needed. it is pretty easy to feel if a rotor has surface problems when you use the brakes before the service. , so measuring for flatness would be rare, but it is pretty easy. wear would be the only reason I would replace a rotor, not just because of any established pattern without a clear reason behind it. old mechanical wisdom is sometimes best discarded rather than trying to jam it into new situations just because.

I think the tip about the pads serving as insulators very useful to have, even if I never run stuff harder than when on mountain roads . an obvious truth, handy for track use, , yet never covered in any of my other reading where wear indicators , the noise makers , are about the only measure of pad wear.

 

Thanks for the responses. My mechanic is definitely old school. At the same time, he is also an experienced race car driver. He's owned several corvettes of multiple generations including a C5. He knows cars and Corvettes specifically better than just about anyone I've met. I've always been happy with his work, and I've never questioned his advice before. My rotors are only a few years old, and they show absolutely no signs of wear at all. They look and feel smooth to the touch, and my braking is smooth. The only reason that I'm changing pads at all is that the ceramic compound on my current pads fades badly when braking from high speed. When I was making my appointment with my mechanic, I told him that I had new pads and new fluid, and he said they absolutely refuse to change pads without resurfacing or replacing the rotors. When I questioned this, he told me that once the rotor gets hot, it forms a crystalized layer on the surface. He told me that crystalized layer is part of the bedding process, and that as long as it is there that there is no way that a new set of pads can properly bed.

 

My last two daily drivers. The first had 77000 miles with the original rotors, Two replacement sets of pads. The second with 50000 miles with original rotors and one set of pads replaced. The rotors were real good when the pads were replaced. No need to replace them. Each time the pads were good but were cracked. No problem. The thinking of your mechanic is not wrong but out dated. My guy was the same way at one time, until he saw how good the rotors have been.

 

I wouldn't balk at a resurfacing of the rotor. That's okay. I would definitely balk at outright replacement without them measuring the thickness.

Especially since you're changing pad compounds, it'd probably be a good idea.

 

Sorry i disagree. If the rotor is good way cut them. In my opinion it increases the chance of warping.

 

Fly cutting a few thousandths off is just going to get the deposits left from the other pad compound off of the surface.

Most brake pulsations are from pad deposits or debris that gets lodged between the rotor and pad surface that damages them. Turning the rotor isn't going to increase the (incredibly slim) chance of warping. Manufacturer's have minimum thickness specifications for that reason.

 

Guess I'm old school....rotors and pads are cheap.... change both when necessary.

 

You make a good point. Hopefully, I'll be happy with the new pads, so I shouldn't have to worry about it again for a long while. Frankly, if the new pads don't do what I need, I'll probably have to consider the Wilwood 6 piston anyway.

 

What pads are you going with?

 

Hawk High Performance Street (HPS) 5.0

 

Those are decent. If they don't work for you, reach out to Ken at KNS Brakes for a solid recommendation.

 

Help me understand your (incredibly slim) chance of warping. Is it not possible to warp a rotor? Cut or not cut.

 

I don't replace them unless they're warped, beyond useful thickness or damaged in some way. I've also read about the cutting tool leaving groves and whatnot. Like stated before, they're fairly cheap for a stock set so I don't bother turning them anymore when they need attention. I've also tried the hawk pads you're trying and they do work good. They also will dust more then ceramic ones. I got tired of constantly cleaning my wheels so I went back to ceramic again.

 

Hey Mark, that was my original thought process. I certainly wasn't going to replace my rotors when there was nothing wrong with them. However, my mechanic absolutely refuses to just swap the pads. I'm going to let him spin them, but I'm not thrilled about it.

 

If he's got one of those newer style on-car lathes, it'll be quick and easy. I genuinely wouldn't worry about it. We use them every day at the dealership.