22 replies to this topic

[plane]

I just noticed that my "high end" $31.00 Brembo Rotors have very small very short "cracks" mostly in the middle of the rotor face. You can't feel them and when you clean the rotor face they are harder to see. How normal is this and at what point do they need replaced?

[Bench Racer]

I just noticed that my "high end" $31.00 Brembo Rotors

Are these rotors truly Brembo at $31.00? Pretty economical for Brembo. When I raced a RX7, I found China copys in a Brembo box. Even talked to Brembo about the issue, they admitted there out there.

[HoneyBadger - BrianW]

I have brembo rotors and have noticed the same thing. I don't worry about them until I can almost put my fingernail in the crack. If there are hairline cracks that go all the way to the edge and to the other side of the rotor surface I would probably change them.

[Keith Andrews]

I agree with BrianW no worries with the small cracks. This is not exclusive to Brembo rotors.

I've been using the Wearever rotors from Advanced Auto, around half the price. They are great as far as I'm concerned. I get a season or more out of the rears and 3/4 of a season out of the fronts. My season is about 10-12 race weekends.

[plane]

Thanks. This is the first set or rotors I have had that did not warp after 2 weekends so I am new to how rotors age. They look and feel real (casting and machining looks better than all but Mazdaspeed rotors) and don't warp and I hope Amazon is helping to police resellers. They come from Hoerr Racing Products.

[Zauskycop]

Carroll Smith, once in a small "town hall" type meeting I attended, spoke about rotor warping. He said that a good 75% of rotors don't really warp, and what you are feeling is the material from the pads adhering to the rotor when the car comes to a complete stop. He adamantly emphasized that you should try to run the cooldown lap without using ANY brakes, and even then try to let the car coast to a stop so you avoid stopping the car completely with hot brakes. Have never had a brake rotor "warp" since.. Crack? Yes haha

[MPR22]

Small cracks ok, but check rotors regularly, had a set on my 1.6 crack full thickness in two places one of which was close to going through the entire width of the surface. Felt like a bad flat spot and caused bad lockup of that wheel.

[robertcope]

Just pulled this Brembo off my car...



Guess I got my money's worth out of this set of rotors.

robert

[Bench Racer]

Yes and a bit more.

I may be a bit more sensitive than some about rotors. After an ITA RX7 session at Road America I came in (aware of not using brakes on in lap) got out of car, walking around car and hear a loud SNAP, what? After examining the RF rotor, it was cracked open through the bearing hub like a water mellon.

[Dennis]

Just pulled this Brembo off my car...



Guess I got my money's worth out of this set of rotors.

robert

In your picture I can see the little cracks or fissures that Plane is talking about. They always appear no matter what kind of rotors I use. I just keep checking them and don't replace the rotor until they start to open, pretty easy to see with a flashlight. I use about 2 sets of fronts a year, around 15 race weekends.
Dennis

[robertcope]

In your picture I can see the little cracks or fissures that Plane is talking about. They always appear no matter what kind of rotors I use. I just keep checking them and don't replace the rotor until they start to open, pretty easy to see with a flashlight. I use about 2 sets of fronts a year, around 15 race weekends.

Yup, they're there and they always are. This set of rotors has about 37 days on them. Clearly they should have been replaced some time ago, though. I got lazy and complacent.

robert

[Tom Sager]

Small cracks like these are a very common occurrence from what I've seen and more likely if you use the same unmachined rotors for more than 1 set of pads. Choice of pad is a factor as well. Some pads create more heat and wear to the rotors and let's not forget that we're using performance pads that likely create a lot more torque and heat than what the factory intended for these cheap rotors. Frankly I think we're lucky that our brake components hold up as well as they do given what we do to the brakes. Many preach new or freshly machined rotors with each pad change and the thinner the rotor the more likely it is to develop those cracks. That and I've seen variations in the visible design and weight of rotors that are sourced from the same supplier showing the same part number on the box.

[Muda]

And here's what it looks like just before if fails.
There's a reason they're so cheap.
Change them with every set of pads.

[Jim Drago]

If that is just before it fails... I would hate to see a failed one

I have said it before on the site, the best rotors I have ever used are ones we pull off street cars. We resurface close to min thickness and run them typically a season with no issues

Jim

[Bench Racer]

I have said it before on the site, the best rotors I have ever used are ones we pull off street cars. We resurface close to min thickness and run them typically a season with no issues
Jim

Oven heat cycling new rotors gets similar aged heat cycle results.

[FTodaro]

you guys are using to much brake.

I buy 20.00 rotors at NAPA they will last me a season with no issues.

[Tom Sager]

you guys are using to much brake.

I buy 20.00 rotors at NAPA they will last me a season with no issues.

A couple weekends a year at Blackhawk Farms will shorten the life of your rotors, pads, hubs and the fillings in your teeth.

[Duane Polsley]

Chinese Blimbo's no worky long time !

[Bench Racer]

you guys are using to much brake.

I buy 20.00 rotors at NAPA they will last me a season with no issues.

That's why there's a helmet rule.

[SaulSpeedwell]

I just noticed that my "high end" $31.00 Brembo Rotors have very small very short "cracks" mostly in the middle of the rotor face. You can't feel them and when you clean the rotor face they are harder to see. How normal is this and at what point do they need replaced?

Very normal, and not *USUALLY* a function of the rotor quality. Pads, tracks, and your "cooldown lap" procedure make a difference.

Rules of thumb vary, but a conservative rule is that cracks up to 1" are OK on a rotor of this size, until and unless they open up enough to catch a thumbnail in it.

The smaller uniformly distributed hairline "cracks" are described as "heat checking", and are categorized as normal, and can be returned to service without turning, by every drum / rotor failure analysis manual I've ever seen.