On my AE92, the last set of rotors, which were just regular Centrics, had to be tossed due to fine radial cracks on the surface of the discs. They had about 3 years of use on them with maybe 6 track days and 5 autocrosses per year plus a bit of street driving. I went through one complete set of front pads (EBC Yellow) and maybe a quarter of the material on the rear pads in that time.
This is the problem 2-piece rotors were made to solve but I can't spend 2-piece rotor money, especially since some custom work would almost certainly be needed to put together a set for this car. Should I do more brake warmup before using the brakes hard on track? Would a brake vent system help? Maybe less aggressive pads?
GameboyRMH said:
On my AE92, the last set of rotors, which were just regular Centrics, had to be tossed due to fine radial cracks on the surface of the discs. They had about 3 years of use on them with maybe 6 track days and 5 autocrosses per year plus a bit of street driving. I went through one complete set of front pads (EBC Yellow) and maybe a quarter of the material on the rear pads in that time.
This is the problem 2-piece rotors were made to solve but I can't spend 2-piece rotor money, especially since some custom work would almost certainly be needed to put together a set for this car. Should I do more brake warmup before using the brakes hard on track? Would a brake vent system help? Maybe less aggressive pads?
Get rid of the heat. Brake ducting would most likely solve this. Cryo treated rotors might solve it also.
I'm assuming rotors that are not solid rotors. They have vanes in between the faces of the rotors, right? If so, duct to the inside center of the rotor. Air is supposed to go in there and exit the vents.
Uneven cooling can cause this as well.
Fine cracks (crazing) are not really an issue. It happens.
Deep cracks (as in cracks you can see light through) are an issue.
You need cooling, and better warm-up/cool-down routines, if your problem is deep cracks
Unfortunately I didn't get pics of the cracks, I was crazy-busy at the time and the shop working on the car has tossed them in the months since. They didn't look like they were close to letting light through, but they were deep enough to catch your fingernail on. Here is a pic of similar damage I found online:
I'd been planning on adding a brake vent system anyway so that's an easy improvement. Previously I'd been doing 1 lap with gentle-to-moderate braking for warmup and at most a full lap for cooldown. I feel like there could be room for a less aggressive pad, the EBC Yellows laugh off any heat I can dump into them and only feel fully warmed up on the track.
In reply to GameboyRMH :
If you can catch a fingernail on them, that's bad... I'll second finding a way to cool them better.
Brake rotors are a consumable. Find a good supplier, use old ones as bases for lamps, and move on.
Some (most) cars, the brakes are not up to competition spec. All the ducts on the world won't make your brakes bigger.
No, but it'll help keep them cool which is more important than making them bigger.
Ducting ducting ducting.
In reply to GameboyRMH :
It sounds like you got decent life out of them all things considered. I'd expect the cracking as cheap centric rotors w/ aggressive pads make the rotors a short-term consumable.
The rotors on my race car get the same exact cracks after a few weekends on use. I've had decent luck with the cryo version for a few bucks more.
For our lemons we buy the cheapest rotors available and treat them like a consumable. If we get 2 races that's 28 hours of hard stops for $25.
That works as long as you're not running a 19 hour race :)
Edited because math is hard. Thanks keith
Ducting it is then. The front brakes are vented and the rears are solid, all had similar cracks though. No cryo-treated models are available for the AE92 unfortunately. I have to squeeze as much life out of these as possible since they'll have to be imported from the US to Barbados, with duties and shipping on those heavy hunks of iron, a $50 set of brake rotors will end up costing me around $200. For cheap rotors like these, most of the grand total cost is shipping.
Barbados changes the whole equation...
What is easy here is not so easy there.
Ducting will help. I'd try to find a way to upgrade to bigger rotors and pads, something you can get locally.
ddavidv
PowerDork
1/20/20 7:21 a.m.
I'd get a few race weekends out of the cheapest USA or German rotors I could find for my Spec E30 race car. It was only the fronts that would crack like that. At $20-$30 each I'd just treat them as consumables. A different story if you've got a car with $100+ rotors, certainly.
wspohn
Dork
1/20/20 10:24 a.m.
Some of the guys that raced the 240Z here back in the day came up with a very creative cooling method. The cars had 14" wheels with fairly large brakes and it was difficult to get more air passing over them, so one bright light found that Corvair engine fans (air cooled, right?) could be machined to fit to the outside of the alloy wheels with lock wired Allen screws, oriented to that they sucked the air through the wheels over the brakes. Made a huge difference to brake cooling.
Wonder if you could do something similar (check the rules)
Nugi
Reader
1/20/20 12:20 p.m.
If shipping is that much, consider having someone in the USA receive and Cyro-treat them, before sending them on to you. Might be cheaper in the long run. Plenty of shops in most cities with the equipment now.
I run the cenric cyros hard on my hondas with no issues. Not sure if there is any difference beyond the treatment.
Cryo rotors and ducting seem to have done the trick for me.
The way to save some $$$ is to not by Centric rotors and expect them to last. You got your $$$ out of that set. Also (and I may be wasting $$$) but when ever I changed pads I changed rotors. If I changed pads because of the track I was going to and they were only half used I would change the rotors and keep the old rotors with the pads for possible future use or as a backup set as long as they were still serviceable.
The point is pads and rotors were always considered matched sets. Only in emergency's would we mix and match.
The only exception was in long endurance races but we would bed in multiple sets of pads to a single set of rotors so in effect we could have three sets of pads bedded in to a set of rotors and have two or three replacement bedded sets as backup with each rotor having at least two sets of pads already bedded in. These were in box's with the pads and rotors labeled so s not to mix them up.
