Need A Rotor Diagnosis (pic inside)

[KAA]

What is causing this pattern on my front rotors? It repeats this pattern all the way around and it's only on the outside face, not the inside.

[chicane67]

In this on both left and right ??... and only on the outside surface.

Do you have an outside micrometer that will measure to 0.0005-0.001" ??

What it looks like is TV (thinckness variation). If it is only localized to one rotor, it could be a soft or hard spot in the pad itself. Now if it were on both rotors..... it could still be TV and I think that it would be caused by a temperature spot on the rotor itself. Which, would be from the rotor design and/or the way it was drilled in relation to the internal vents.

It could also be from the slots building up enough cut material when the pad first come to the slot itself. It could then feed it onto the rotor at that point and that could also cause a localized TV from the extra cut material and the fact that the cut material is more susceptible to higher initial temperatures.

I dunno..... just some thoughts.

[andrewb70]

Can it be cause by some gease that contaminated the pads during installation? Just more thoughts...

Andrew

[chicane67]

Definately.... could.

[KAA]

I doubt I contaminated the pads. I'm always extremely careful not to get anything on them. Also, these have been on the car for three years and it just showed up after the last track event I went to. The picture is of the driver's side rotor. The passenger side looks the same but not quite as bad. If it's bad, I dunno. And yes, it's only on the outside face. These are Wilwood rotors. The calipers are Wilwoods 6 piston Superlites.

I don't have an outside mic but I think I can borrow one.

[paul67]

If the rotor has different thicknesses the pedal should be going up and down if you put your foot very slightly on the pedal.

[DeltaT]

Can you mark up that rotor and show where the inner vanes are relative to the spots that you already pointed out?

Jim

[BA.]

forgive my lameness here, but they look like hotspots like I've seen on a clutch plate. (motorcycle)

Also, they look to be perfectly/equally spaced apart from each other don't they?


.

[chicane67]

If the rotor has different thicknesses the pedal should be going up and down if you put your foot very slightly on the pedal.

Not necessarily. A difference of 0.001" can create issues like this. In fact, I will agree to a point. Normally it takes as little as 0.001" for it to create enough TV for it to be felt in the pedal itself. But the thickness, when measured, can possibly give us a better idea of what is actuall happening.

If there is none.... it is probably a thermal issue localized to that one sector. Which, could be from the rotor design and/or the way it was drilled in relation to the internal vents.

[OneslowZ28]

my vote is for hot/hard spots, very common when hard on the brakes and they will continue to reappear till the rotor is replaced. many people think machining them will take care of it and it will not. ive delt with this before from a customer at a brake shop i work at. i machined his hardspotted rotors for him just to prove a point when on the lathe the bits did not cut the spots as well as the rest of the rotor. needless to say he came back in a few day to have them replaced.

I could be wrong but this is what i have come across before. Sucks they are not cheap rotors that it happend to. Good luck!

[ProTouring442]

I agree. They look like hot spots to me too. And just like the previous poster, I too have tried to turn them out on the brake lathe. You can't!

Shiny Side Up!
Bill
'72 442 "Inamorata"

[RSX302]

What is causing this pattern on my front rotors? It repeats this pattern all the way around and it's only on the outside face, not the inside.

Keith, What pads do you run. I wish mine looked like that.

I agree 100%...Those are high hot spots. I noticed on mine that Wilwoods are not the flatest rotors in the world. How does it stop? Any vibrations? If all works good, I wouldn't worry to much about it.

[KAA]

Those spots are gone. They disappeared the day I went to the drag strip. I also did an open track day since then and they did not reappear. Odd.

The pads came with the late model F-body kit I installed. They're the Polymatrix E compound pads. They seem to work great. The rotors don't show any signs of wear but I do think they're getting warped. The only time I notice it is on the track when I really hammer on them. When I get down around 60-50 mph the front end starts to shake. I never feel any pulsation in the pedal and the steering wheel doesn't so much as twitch. This started after about 10 laps the first time I put the car on the track. They don't fade but that shaking is definitely getting annoying. I'll be trying a different rotor. Most likely a slotted non-drilled rotor from Coleman racing that I can bolt directly to my Coleman aluminum hubs and eliminate the Wilwood rotor hats.

[RSX302]

The warp you will feel in the pedal. I would recheck wheel balance. Could have thrown a weight.

[ProBell]

That is the opposite problem I get. I get pad build up on the rotors that cause a break pulsation that goes away after a few laps. I is was better after I went to Hawk HPS pads. I think I need to go to a more aggressive pad. Have you tried different pads? Track pad verses street pad. A few of the guys I run with have two sets of pads and rotors to help with break problems. Randy

[paul67]

Where are you feeling the shake ?

[paul67]

Where are you feeling the shake ? how old is the brake fluid and what grade ?

[KAA]

Where are you feeling the shake ? how old is the brake fluid and what grade ? On the road course under very hard braking, say from 110 to 50. It starts doing it around 60 mph as the car is slowing. I put brand new Wilwood 570 fluid in before my last track day and it did the same thing.

[paul67]

If its doing it after some use it might be the wheel bearing heating up , coming loose and causing the disc to shake.

[sinned]

TV from the track day excursion. Your trip to the 1/4 sent rotor temps high enough during the back side stops to burn off the material (hint to guys with "warped rotors"; heat up till they glow and allow them to cool naturally, it burns off the excess material).

[vintageracer]

Just a thought. We had a fellow racer with Datsun 510 at a Vintage Race that was having what he thought was TV with his rotors. After a thorough complete front suspension evaluation by several fellow racers including myself at the track, the problem was isolated to a loose idler arm. The slight feedback he was getting through the steering wheel and brake pedal was actually the steering arms moving ever so slightly up and down. He replaced the idler arm and problem was solved. He now realizes that HIS "pre race" car preparation must improve!

The owner was the only one who drove the car so his initial diagnosis was based only upon his own personal skill set. When others with more knowledge looked at the problem from a broader perspective of the whole front suspension, the real problem was found.

This may not relate to your problem however it is something to consider!

[OneslowZ28]

okay i think this thread is getting a little tooooo deep now. KAA... did you get the answer you were looking for?