Front rotors and pads need replacement at 25k mi? Wondering if other people have used up their rotors that quickly

[razorlab]

Is that an actual rotor or a double stuffed oreo? Asking for a friend. I remember when a rotor was one solid piece of steel.

The rotors on your supra are two piece too. Aluminum hat, iron rotor.

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[AndyK5]

..aand here comes RT to flip your worlds upside down (except Phil, he's already upside down )...

I present to you, the GR Corolla front brakes!

Pads are a reasonable $120, and rotors are a budget-minded $810 EACH!

I had a CE…hated the fact that rotors were so expensive. Not that you need replace two piece rotors that often but that ot was absurdly priced AND you can’t just replace the rotor surface, tou have to replace the whole thing if its OEM which defeats some of the purpose of the 2 piece wheel design.

 

[razorlab]

Motorcycles and pebbles....

Thats fair, I am not sure if my calipers have that cut...or maybe they do and I have not thought about using that notch.

So, I am pretty much done with arguing with people on here so I will just share more info about this.

The micrometer is a much better tool than the flat calipers for measuring automotive rotors. It's even what they use in the actual service manual for our Supras:

Also note, they measure at three different parts of the rotor face. Rotors don't wear flat. Imagine that.

So, let's see why it's a better tool. For this demonstration, I will be using an actual rotor that came off a Supra, not some random non vented rotor on some random car that isn't a Supra. I know, weird right?

Supra rotor in question, nice and worn, I think there are about six or seven track days on this particular rotor.

Since this rotor is used, it now has a lip on the outer edge, which worn rotors have. Also note that rotor wear ain't flat...

Let's take our calipers and make sure the indent in the caliper is where the worn lip is on the rotor, per our resident Aussie's suggestion. Now if you notice, that makes it so we can only measure one part of the face of the rotor. That will only give us one measurement on the face of the rotor. This does not follow the service manual.

Now, let's measure that lip on the rotor:

Hmmm, it measures 36.20. The rotor starting thickness, per the service manual should be 36mm. Well, metal does weird things when it gets hot, this being one of them. You know, let's just excuse that, since this isn't a post about metallurgy.

So we have our one measurement of the rotor face with our calipers, which is 35.81mm. With this one measurement (The only one we could get with this caliper), these rotors are only worn 0.19mm

Now, let's use the tool the service manual uses... and take three separate measurements across the face of the rotor.

First off, this is much easier to use as the lip worn into the rotor is not giving us any restrictions with this tool, a tool that the service manual uses...

Measurement #1, note this is showing a different thickness than the calipers gave us.

Measurement #2, which also happens to be the same area that the calipers were only able to measure... note this is showing a different thickness than the calipers gave us.

Measurement #3, note this is showing a different thickness than the calipers gave us.

So, the service manual tells us to take the lowest value of these three measurements and use that for the rotor wear check...

35.15mm, note this is showing a different thickness than the calipers gave us. This rotor has worn 0.85mm, still within the valid number, shown in the service manual, as measured by the tool used in the service manual.

So, the takeaway here is to use the right tool for the job, or in this instance, what the service manual tells us to use. Also, it's also good to actually measure rotors from the actual Supra, since we are on a Supra forum, talking about Supras, not motorcycles or our wifes random car that isn't a Supra.

Btw, if I remember correctly, this tool cost me a hefty sum of $40.

 

[EddieNel]

We can do it your way or we can do it what some people call the right way. Well here ya go! Thank you @razorlab for that extremely sarcastic but yet very informative explanation.

 

[rwense]

God bless @razorlab, I live for your data and sarcastic write ups ? the patience you have is mind boggling.

 

[a90taxi]

I went through mine in 10k miles

 

[Rensuhlo]

@razorlab never change. We must protect you. You're a 10/10 on 10/10.

 

[decodeddiesel]

@razorlab is 100% correct here.

Flat calipers only measure the height of the HIGHEST PEAKS. You are closing two parallel planes along an AREA. This is only going to measure the high points in the area. This is not a point measurement.

The brake disc calipers come to a point, and measure the rotors at specific points. This allows measurement of the peaks and the valleys. This is critical because rotors don't wear flatly, they have ridges, ie peaks and valleys. The low point is what you're worried about, and the only way to measure that is to use an instrument with a point.

Not for nothing but this is pretty basic stuff here.

 

[Rensuhlo]

$30 and you can return it after use. Hella expensive.

https://www.harborfreight.com/6-in-long-reach-digital-caliper-63714.html

 

[baagel]

Micrometer companies after razorlab's post

 

[Rocksandblues]

I’m going through a set of front rotors each year While not as exact and thorough as professor razor- he is spot on per usual.

 

[Todday1]

Great info by razorlab. I track rotor duration by number of track day events I can get out of them. Fronts have been the issue. As you get to faster tires/ race compound then you can go in deeper / brake later. So really depends on driving levels and tires. I have cracked front rotors in as fast as one 3 day week end. Heat management for fronts has been a struggle and am now on my second big brake set up. Custom built 15” rotors. So will see how these hold up. So if you track a lot you will go through fonts a lot faster than rears.

 

[razorlab]

@lucky phil my little Aussie man, nothing eh?

Let us at least talk about pebbles in the rotors! Come back to me my always wrong but always calling me out for some reason huntsman spider slaying brother!!!

At least post more photos of your 1982 garage! Please, I love it.

 

[rwense]

@lucky phil my little Aussie man, nothing eh?

Let us at least talk about pebbles in the rotors! Come back to me my always wrong but always calling me out for some reason huntsman spider slaying brother!!!

At least post more photos of your 1982 garage! Please, I love it.

Yo I'm just coming here to say, fuck pebbles. 3 times now ?

 

[razorlab]

Yo I'm just coming here to say, fuck pebbles. 3 times now ?

Agreed. @lucky phil always thinks it’s something else though, even after proven wrong! Maybe his garage from 1982 knows something we don’t!

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