geerookie

I'm sitting in my hotel room in the UK and getting bored. I've been over here for a week already and don't leave until this Saturday.
So while sitting here I thought I would stir the pot on this debate with some facts I collected this past season, plus I had the time to do the work to upload the high res pictures.

I switched to two piece rotors a couple of years ago for various reasons.
Lighter weight, longer lasting, better performance, less work at the track or in the shop, safer, just to name the big ones.

I run Wilwood calipers front and rear. SL-6R/ST's front and SL-4R/ST's rear. These are the full-size calipers with the Thermolock pistons.

I have used Cobalt Friction XR2 pads (7420) all year.

The rotor's pictured below have between 130 and 140 track sessions on them. I can't remember the exact number and my documentation is at homebut I'm sure it is at least this many sessions. About 60% of those sessions were 20 min sessions. The rest were 30 or 45 minute sessions. Some days my car was on track in back to back sessions all afternoon. A few other people drive my car, not always me. Some are harder on brakes and a few are easier. Those who are harder will remain nameless...you know who you are

The tracks were, Watkins Glen at least 5 full days, NJMP (both tracks), Pocono (all 5 tracks), Limerock and it seems like somewhere else but my memory is fading. It's getting late over here.

I used 5 sets of pads total, front and rear combined for the whole season.
The set of pads still on the car have about 35% front and 45% rear left.

When I was running NAPA rotors with the same pads I would use a set of rotors in the front every weekend and they would be in worse shape than these after the whole year. That was with factory C6 calipers, not the Wilwoods.

These rotors are from Gary Hoffman at Hardbar. These are not the new T1/AP Racing rotors. These are the ones he designed to work with the factory slide rail calipers. They are either $800 or $850 a set. They use balanced Coleman Rings.

From my experience these Hardbar 2 piece rotors were well worth the initial cost and saved me tons of work and fear of cracking a rotor.
By my calculations I would have bought 9 sets of NAPA rotors at about $84 per set which is $756 plus tax. This was a great investment. It made my car safer and saved me a ton of time which resulted in more time to help others change brake rotors and more importantly have time to hang out and talk.

RX-Ben

Wow. That is a lot of sessions and I'd love not to lug 6 spare rotors to the track with me. Changing discs at inopportune times gets old.

ace996

My last day with NASA/PDA at NJMP Thunderbolt led to a major crack durning the 2nd session. Front/driver rotor. Crack was bad and was very unpleasant/unsettling to drive home to LI. I'm considering going to 2-piece and, based on your write-up above, I'd like rotors to last a whole season, too.

Funny, several guys were more than happy to help me change the rotor at the track...seems like all the vette-guys have a trunk-load of rotors on hand...which is telling me something.

I'm still running the stock calipers with PF01s in front, with DRM/Quantum ducts.

See you next season,
TomK

Dan Wendling

I don't understand what using a 2 piece rotor has to do with the very long rotor life you are experiencing.

My read is that you never changed the rings over the 130 - 140 track sessions. Seems like a quality 1 piece rotor could give similar longevity at a lower cost.

So what do new Coleman rings cost vs a quality 1 piece rotor? I think they are about the same?

So while there is a technical benefit to a 2 piece rotor, it is not clear from your experience that they are more cost effective.

PS> I agree that it is also nice to carry 1 or 2 types of rings not to have 4 different rotors to carry around. But I don't think this alone is worthy of the initial cost.

argonaut

Last year I used "napa" rotors and cracked them regularly. This year I mostly used a set of PFC two piece (bought used from forum member) and didn't have any issues. They have at least 60 sessions on them and have typical heat checking but will survive many more sessions. Cost wise they have almost paid for themselves already (because they were used, i.e. cheap) - but in my opinion not having to swap rotors in between sessions and possibly loose sessions due to rotor issues is easily worth the price anyway.

Besides the convience of not doing rotor swaps all the time, 2-piece have other advantages - like transfering less heat to the wheel bearings, and if they are full floating, say good bye to judder. Some two piece rotors are lighter also (although my PFC's aren't).

Recently got the Hardbar T1 AP rotors, so the PFCs are now my back ups. Nice to have two sets of high end rotors - I don't anticipate any rotor problems for a long time.

jaa1992

Dan - when you really start using the brakes the one piece rotors heat up a LOT.
I know C5 guys that go thru 3 - 5 quality rotors in a weekend. Even cryo treated rotors!

Now on my C4 my seasoned with street miles rotors have lasted all season, just need to get three more events out of them. Hoever if the stars and finances align I'll be getting a big brake package with two piece rotors for next season.

I understand where the OP is comming from. For a C5/C6 I agree with his assesment.

PaintballaXX

I was responding so someones quote that I misread but im leaving the response anyways, even though most of you track guys already realize this.

In a one piece design the outside of the rotor, the swept area that comes in contact with the pad, obviously heats up much much more than the rotor hat. A two piece design, where the rotor is only about as thick as the pads, will have unconstrained thermal expansion. With one piece designs the rotor geometry cannot hold true when the inside and outside of the rotor are not at a uniform temperature.

PeOR

So, I am reading this after having spent a good amount of time today trying to get the material transfer from my Hawk DTC70 pads off my DBA4000 rotors with a belt sander.

I got too bad vibration this second track day and tried to get two shops to help me turn the rotor. No one wanted to touch them due to the small heat cracks. I guess they are not used to track used rotors. Usually the rotors tend to clean up themselves but for some reason not this time.

So my statistics so far is 6 track days on a set of DBA4000 and rear pads, 2 track days per set of front pads. After reading this I really need to consider those Wilwood brakes. Or at least some DBA5000.

PeO.

JVetthead

Man.... I guess I just dont use my brakes enough.. Been runnin the pointy end of TTu for 4 years. My napa rotors last all most all season.
dedicated track car.

Stock calipers, fronts on the rear, xp12 both ends. pads last at least 1/2 a season on front and 2 on rear.
I will try harder to use 'em up next season....

I reckon the aero might help transfer more work to the rear.

GeorgeZNJ

I'm with you on this one, and I'm normally not at the back of the pack. DTC-70's on napa rotors.

geerookie

Generally speaking 2-piece rotors use a higher quality metal than 1-piece rotors. I assume manufactures think most people buying 1 piece rotors are not racing so they don't need the higher quality due to much less heat generated.

John Shiels

140 sessions is

Jason

That's amazing.

brkntrxn

I agree. Wow! What is the secret????

I generally crack at least one rotor per weekend. Front or rear, doesn't matter.

This past weekend at CMP, I thought I had gotten away with not cracking one by only running Sunday. One of my fronts cracked before I got out of Kersaw and I spent the next 90 miles downshifting and using the emergency brake to come to stops.

I don't leave home without at least a spare front and rear rotor in the truck and trailer. Most of the time I have a spare full set. Heck, I damn near take a spare and tools with me when I drive the car to the store for beer!

geerookie

I'll bet your guests love it when you go on a beer run.....Don't worry, he'll be back in about 2:13:22 today. His best time was 2:12:31 but he as at least 3 heat cycles on these tires.

brkntrxn

Haha, you know it! Remember the dad from The Christmas Story? You oughta see me with flat tires.

True story:
Back in October, I was towing back home from CMP and got a flat on my F250. I called my wife to tell her I was going to be later than expected. After hanging up, I beat feet around the truck and got the tire changed pronto. As I was getting back up to speed on the freeway, I called home again and said, "What was my time???"


-Kevin

RX-Ben

OT - the NAPA rotors are steel, correct? I plan on MIG welding my cracked ones to make some art/furniture pieces.

JimbeauZ06

This is always an interesting topic and several of my buddies and I have debated and experimented with this a bit over the last two years.

3 years ago a set of NAPA rotors would last all "season", but a season was maybe 10-12 days and I know now I wasn't going nearly as fast as I thought at the time. Definition of "flat out" is much clearer now.

The last two years the "season" has been 17-20 days and at no time this year did I make it through a 3-day event without cracking at least one rotor even if they started new on day one. What was once an occasional inconvenience has become a major PITA, and since I've begun instructing I don't have a lot of extra time to change rotors between sessions.

I've also found myself "babying" the brakes toward the end of an event to try and forestall having to replace them at the track. Not ideal.

This winter I have several planned upgrades and the new AP T1 brake kit has made it's way near the top of the list right behind the tranny cooler!

codename Bil Doe

^This. 2-piece rotors are better materials and forgings (esp vs. Napa crap), better heat dissipation due to alum hats, plus the added benefits of reduced unsprung weight and rotational inertia.

geerookie

Give me a call sometime this week if you get a chance.