I'm not knowledgeable on "reading" a rotor that has seen track duty, thought I'd get some opinions on this. I noticed on my last HPDE increased pedal pressure required to slow the car down. It's the goodwin Wilwood 11" kit with polymatrix pads (not 100% on which letter). So I inspected my rotors and they don't look quite right to me. Lots of inconsistent markings, and some light surface cracks. They don't have any noticeable lip or anything that would make me thing they are worn, did I manage to cook them? I've always given them a cool down lap.

 

I should say, fluid is fresh, rears look 100% fine. This was at Blackhawk farms (~106mph tops) in 85 degree ambient.

 

If they were solid, I'd be OK on those for another day or two with careful monitoring. Since they are slotted, I'd pull them now.

 

those rotors have seen some heat. the rules for when it's time to replace a rotor.

1. if you go past minimum thickness.
2. If you can fit your fingernail inside a crack
3 if you have a crack starting at the edge of the rotor.


the blue tint you see is transfer layer from the pad. that will develop cracks and it's nothing to worry about. once you see the iron splitting apart it's time to switch.

 

Thanks for all the info. Now I just have to decide what to replace them with (v4 wilwoods, blanks, or upgrade to 11.75...)

 

i'm a big fan of the V8 roadsters 11.75" kit. but that's just me

 

The fact that replacement rotors are only ~$40 might make the upgrade a real possibility. I'll have to give them a call to discuss.

 

true. they use a 8x7 bolt pattern (same rotor as 90% of circle track cars). so when you burn up the $40 rotors( won't take too long) you can find quality rotors that will last. for example i'm on PFC rotors. i'm on year 5 with the same rotors. mind you i have 500hp, and do 15 track events a year. my pfc rotors have out lasted a set of dynalight calipers lol.

 

Very true...I think I'll be going with the TSE or V8R upgrade kit and sticking with my current dynalites. I don't track the car nearly as much as you and others on here, should be enough for what I need.

 

It hasn't been mentioned, but I've never heard of anyone running Wilwood pads on Miatas. Are those just the pads that came with your kit? You might be better off running something else.

 

They came with the car and had plenty of life so I didn't mess with them. But I will be trying out other options with the new rotors.

 

As Johnny (OGRacing) said, those very fine cracks are normal and not cause for alarm. Check your rotor thickness with a caliper (the tool not the brake components) to get a feel for how far through their usable lifespan they are. You're probably not even half way through.

On a separate note regarding heat, you may also be using the wrong pad for track use, which will contribute significantly to putting more heat into your rotors than if you use higher torque pads intended for track use.

Polymatrix is a whole line of pads from Wilwood of varying compounds. What is the letter designation for your pads?

-Ryan

 

I'll have to confirm the letter when I get home from work. I purchased this car already setup for the track by a driving instructor, so the rotors had seen a good amount of track time (VIR, Road Atlanta) before I touched the car (and I'd hope he knew what he was doing when selecting pads). I've ran 5 HPDE events since purchasing the car. Either way, I'll get the exact info this evening.

 

right. every rotor company will post minimum thickness. general if you go threw 1.5mm it's time to replace them. the dynalight we(miata people) have on our cars uses a 20mm thick rotor. if it wears down to 18.5mm it's time for a replacement.

 

I agree that I am likely not near the end of the lifespan in terms of thickness (I'll measure to confirm). Should I be worried about the inconsistent marking on the rotor? Would it be worthwhile to clean them up a little with some fine steel wool or should I just let them be? Sorry again for all the questions, I don't want to cut corners or make assumptions on something as important as brakes.

 

leave them be. most brake companies have a $1,000,000 CNC mill with tiny tolerances. Then the rotor is fine tuned perfectly by your pads. just think about that next time you take a rotor to napa and have it tuned on a $500 brake lathe.

 

Wow! Do you have a part number for those PFC rotors you are running or the specific line? looks like they have a few different options.

 

Slotted:
299.20.0045.01 & 299.20.0045.02
Performance Friction Slotted Replacement Rotor - Late Model, Modified

Blank:
299.20.0045.11 & 299.20.0045.12
Performance Friction Replacement Rotor - Late Model, Modified

Note that I don't believe the P/N is correct on the OGRacing site for the slotted rotors - it's listed as the same P/N as the blank rotors, but it's an 01/02 designation at the end for the slotted rotors.

-Ryan

 

I'm an idiot, I was looking at PFC's website when I asked that question. I clearly wasn't paying attention otherwise I would have looked at OGracing considering I was asking "OGracing".. Sorry about that

 

Checked the pads, they are wilwood E's