RDnomorecobra

so I guess a few questions ...

who here not only swaps pads for track, but also rotors ... keeping street pads matched with street rotors and track pads matched with track rotors?

just front or front and rear?

who actually owns a brake rotor runout gauge and checks it when swapping/replacing their own rotors? overkill?

Z06trackman

The best way to handle different brake applications (e.g. street & autocross vs. track) is to have seperate rotors and pads. There are two reasons for this:

1) the dimensional profile of the pad and the rotor is unaltered (important for the street where it may take a long time for the pad to wear in)

2) there is a metallurgical change to the rotor from the pad material diffusing into and depositing onto the rotor (especially under track conditions). This may not be true for the new sintered metal pads - I don't know.

I have never used or needed a run-out gage. This bring ups another point. Contrary to popular lore, rotors almost never "warp". A pulsating pedal is caused by a large and uneven transfer of pad material to the rotor - which is not supposed to happen. This occurs when the pad is used beyond its max operating temperature. You can usually see this visually, and it often happens on the street when the stock pads are used continually on a long hill (regular cars and SUVs, probably not Corvettes or sports cars). It also occurs when an insufficient pad (or too thin rotors which cause higher pads temps) is used on the track.

I kept the same rotors for both pads for years until I finally figured out that it doesn't cost any more to have two sets of rotors, and all the problems of switching pads on the same rotors go away. You will need three sets if you use different pads for autocross and street, but if you don't mind dust, autocross pads should be fine for street use.

longdaddy

race pads will remove any street pad material from the rotor on the first couple of laps. i tried different rotors for street/track, did not see any benefits as far as longevity goes and stopped bothering.

regarding runout - it is never an issue for tracked Corvettes, you will crack the rotors from temperature changes much faster than you will remove enough material to measure any meaningful runout.

i have been through about a dozen rotor sets and have never had any warping. uneven material deposits from overheated pads are removed by the fresh pad once you realize you killed the old pad, although if you keep driving on the pad that is actively disintegrating, I guess you can eventually compromise the rotor (assuming you don't crash first)

when the rotor lets go and cracks, in my experience, the surface always looks great, aside from the cracks of course, and there is hardly a "ridge" on the outside. OEM rotors, made in china replacements, hi perf one and two piece - they all go the same way. the only difference is time you get.

Greywolfe

I was switching from track pads and rotors to street pads and rotors but it gets to be a PITA after a while. I have be using my Carbotech track pads XP10/XP8 on the street now since my I put them on in March for a track weekend. The squeal a little now and then but work fine on the street. It probably because I barely have to use my brakes on the street.

Bill Dearborn

I just swap the pads back and forth and don't change the rotors unless they require changing. Going from a race pad to a street pad it may take a little longer for the street pad to seat in but it will. Going from street pads to race pads it doesn't take very long for the race pad to make the rotor its own. Hawk Blues were especially quick at doing that. All I had to do was easily drive a few miles and they had machined the rotors clean.

Bill

Z06trackman

I agree with all that has been said since my last post. However, track pads, when used for a long enough time on the street, not only clean the rotor, but can machine it until its thin. (that is how I learned thin rotors on the track can lead to a pulsating pedal) Also, I wasted a set of new rotors once driving all winter on track pads!

So I guess using one or two sets of rotors depends on your situation, the pads, and your needs. When I switch from track to autocross I need perfect braking right away. I also don't like waiting for the street pads to seat, but yes they do.

gamman3

"when the rotor lets go and cracks, in my experience, the surface always looks great, aside from the cracks of course, and there is hardly a "ridge" on the outside. OEM rotors, made in china replacements, hi perf one and two piece - they all go the same way. the only difference is time you get."

Thread drift a bit: I am deciding if I want 1 or 2 sets as well (Street/track). How long (events or hours) do the rotors last before cracking?

OEM
China
Hi perf 1pc
Hi Perf 2pc

If the surface is spider webbed cracked, is that a precursor to real cracking IE: dangerous on track, or is the spiderweb in the surface the cracks that you are all talking about, to NEVER use? IE: that is when you relegate them to the daily driving or trash?

argonaut

In my experience there are to many variables to give a definitive answer regarding "How Long?". Start with your driving style - how hard you brake has a huge impact on how long they will last. What tracks - some are easy on brakes, some are hard. Also, "China" is too broad - from what I understand a majority of rotors (both good and bad) come from China these days. Very few rotors are made in the US/Canada anymore. Of course pads are another factor determining rotor life. In general higher quality rotors will last longer but they also cost more, so its a trade off. If you are relatively new to this the best advice is to get a set of cheap rotors (like the famous "Napa" rotors or RockAuto), these are just aftermarket OEM replacements. Use them and keep track of how long they last for you. Some guys will only get one weekend out of them, I can generally get 4-6 days, others will get 8 full track days or more. But...I've also cracked a rotor in 2 days, its a mixed bag.

Spider cracks are very normal, all rotors will do it, its just a matter of time. The rule of thumb is continue using them on track until your fingernail catches on a crack as you drag it across the surface. A rotor will generally crack when you pull into the padock and the rotors start to cool, so its ususally not an on track problem. Always inspect rotors before going on track but if you do have a cracked rotor while on track you will know it right away. The car will still brake fine but you will have a very noticeable pulsation in the pedal, time to pull in and change rotors.

sothpaw2

I cracked my first one right through after VIR on the way home. So yes--it can happen not on cool down. The pulsatation is extreme and highly recognizable--trust me you will know it when you feel it.

I think the rotor life is a large function of the pad compound. I think the higher friction pads that make you stop faster dump a lot more heat into the rotors, resulting in quicker formation of the spider cracks. I get about 3 days out of fronts w/wil H pads. This requires good cool down laps. If you have a lot of sessions ending pre-maturely (red flag, black flag, etc etc etc), denying you adequate cool down, then your rotor life will really suffer.

95jersey

Been swaping out just the pads for 10 years. Never been a problem and brake performance has always been oustanding regardless of pad combination or brand swap.

Like stated above, one hot session will wipe any residue from the former pad right off. I could never tell the difference or had any issue changing pad compound (or even brand) in a moments notice. Before I trailered my car, I actually swapped my pads at the track before the first morning session as I drove there with street pads and swapped them back on the way home. Also, at the time, I was winning time trials and running extremely fast laps all day long.

If you are not cracking your rotors long before wear becomes an issue..

1) You are not driving fast enough
2) You are being far too easy on your brakes

Also, choosing a brake pad has MORE to do with your tire choice than driving style. The most hardcore XP16 race pad is overkill for any street tire, and a Hawk HP is going to fade very fast using a set of Hoosiers.

Match your pad to your tire and you will be more happy.

Also one important thing to keep in mind...in MY OPINION rotors are the single biggest disposable part of a track car (more than tires and sometimes brake pads). I would rather be cracking rotors first than eating up brake pads or tires. Find the cheapest rotors you can get your hands on and just tear them up and change them out like you bleed your brakes. Save your money for better things. Rotors should be the LAST thing you worry about saving.

95jersey

Also, I have found that running rotors on the street for some time before track duty makes them last longer at the track. If you take a brand new rotor and immediate subject it to track duty it will crack VERY quickly.

If I know a rotor is in bad shape by the end of the season, I will purposely ditch it and get a new one after my last event, so it can be seasoned on the street during the winter/spring. The gentle heat cycling of street duty hardens the metal slowely and allows it to endure hard duty once it has seen some gentle heat cycles. I always find them to last longer this way than if I have to replace them mid season without any street "break in".

C5Lion

So does this mean when you first put the new rotors on that you do not season them in any way, but just let normal driving season them? When I say season them, I mean braking from 60 mph to 5 mph a number of times and them driving for 20 minutes to let them cool.

95jersey

Yes, I use street pads and just drive the car like any other street car. The process you describe is a pad bedding process (not a rotor seasoning process). The rotor doesn't need a bedding process like race brake pads. It just needs gentle heat cycles (ie. street driving). Don't confuse pad bedding with rotors seasoning. Pad bedding allows the correct amount of pad material to transfer evenly over the face of the rotor, has nothing to do with rotor metalurgy or hardending.

Keep in mind no rotor "bedding/seasoning" is required, I have just found using them on the street prior to track duty makes them last longer all around.

bluemagoo

I've been doing HPDEs and track days for a couple of years now and went to dedicated pads and rotors for the track last Fall. I'm following this thread with interest - it is time-consuming to switch rotors back & forth. I do like the fact though that once I switch to the street set or to the track set I'm pretty much good to go for that purpose.

I'm inclined to agree with 95jersey on gradually heat cycling new rotors. While I'm not a metallurgist, it would seem that this heat cycling would help to gradually relieve internal stresses in the rotor prior to subjecting them to severe service.

Regarding runout, when I removed my stock rotors the first time and installed my DBA4000s, I checked the runout with a dial indicator after thoroughly cleaning the mating surfaces of both the hub and rotor. I found that on one of the rotors, I was able to reduce the runout slightly by repositioning the rotor one stud over on the hub. I've indexed both stock and track rotors to their respective hubs, so I can put them back the same way each time without rechecking.

As a historical side note to runout - the OEM C2 and C3 Corvette caliper design incorporated lightly spring-loaded pistons with umbrella-type seals. Rotor runout in excess of approx. 0.005" produced "air-pumping" into the hydraulic system which could quickly create a soft brake pedal. The way to minimize the runout was to try different orientations of the rotor on the hub and see which position resulted in the least amount of runout. Aftermarket development of O-ringed caliper pistons (& without the springs) in the mid-'90s eliminated the air-pumping problem and the need to pay as close attention to rotor runout on those cars.