Are two-piece rotors worth the extra money?

Thanks for the continued updates.

Brakes larger than a Spitfire's wheel...that's a perspective I can understand.   

Well, I can say with certainty that two-piece rotors look cooler than the stock rotors. 

The two pieces look very good but the article may have answered my question are they worth it for a street car that gets driven to the track. Unless the testing reveals a vastly superior wear rate the weight difference isn't worth the cost for a car used just for HPDE. It would be cool if the rotor wear rate gets tracked as this project mirrors the direction I'm going for my VN. Good stuff. 

In reply to IKR :

In theory your consumables expense can go down, even if life is the same, because you are buying generic 8-on-7" rotors and not brake rotors specific to your vehicle.

You might be able to get cheapo parts store rotors cheaper, but who knows what the iron quality is vs. a rotor specifically made for motorsports?

In reply to Pete. (l33t FS) :

I was thinking that initially but after seeing the prices for just the rings (not hats) for some of the brands, even using an OEM quality rotor is cheaper. So unless the rings have superior wear characteristics I know which way I'm going.

No.  Definitely not.  Almost all of us aren't going to be able to discern a performance difference.  Cost is dramatically more for the 2 piece rotors and when you've worn them out, the rotor rings/hardware kit to "renew" them is several times more expensive than the standard rotors.

Let's use my 996 Turbo as an example.  Now I've upgraded it to 997 Turbo brakes, which are 350mm rotors.  FCP Euro has Stebro slotted, 1 piece rotors for $372/pair.  A set of 2 piece Giro Discs are $1300, so 3.5 times more expensive.  The rotor rings and hardware kit is $850, so almost 2.5 times more expensive. 

Let's not even mention the fact that once you've bought the Stebro's from FCP, you're only paying shipping for new sets going forward, but focus on just the purchase price.  Sadly FCP Euro doesn't sell any of the 2 piece rotor options for Porsches. The Girodiscs are 3.5 times as expensive to purchase and 2.5 times as expensive to replace.  Is the small performance advantage enough to offset that huge price differential?  Nope, especially when they both wear out at basically the same rates...

IKR said:

In reply to Pete. (l33t FS) :

I was thinking that initially but after seeing the prices for just the rings (not hats) for some of the brands, even using an OEM quality rotor is cheaper. So unless the rings have superior wear characteristics I know which way I'm going.

I'm finding rotors in the $30 range.

The rotors in the article appear to be application specific and not a generic part, which of course is going to be more expensive than generic parts.

Pete. (l33t FS) said:

IKR said:

In reply to Pete. (l33t FS) :

I was thinking that initially but after seeing the prices for just the rings (not hats) for some of the brands, even using an OEM quality rotor is cheaper. So unless the rings have superior wear characteristics I know which way I'm going.

I'm finding rotors in the $30 range.

The rotors in the article appear to be application specific and not a generic part, which of course is going to be more expensive than generic parts.

For my application, Hyundai Veloster N, my experience mirrors that of docwyte's but I'll look again.

Something not mentioned is how a slotted rotor bites harder than a plain blank surface.  The machined edge grabs onto the pad harder.  That can either be a good thing or bad.  It also makes a repetitive groaning sound.  I have them on some of my cars and it is tolerable.  On this particular car, it was not...at least to me.  It did get better after a lot of track miles, though.  The edges of those slots were slowly getting worn to be more rounded.

I have two-piece rotors on my Miata and can get just the rotor rings (vented, non-directional) for ~ $30 each. Currently trying a set of higher-end rotors with the fancy slots, directionally vented, etc. I'm bad at keeping notes, but they don't seem to be at all worth it. Feel/performance is honestly not perceptible to me. Pad life doesn't seem to be significantly different. I bought them "used"-but-BNIB, but they are something like 5x the price. I'm stock powered but with a Dynapro 11.75" BBK, I think taking the time to add brake ducts is way more likely to net me longer pad life compared to bling rotors.

I have seen a hardware kit, from Coleman (IIRC), that is supposed to make standard 2-piece hat/rotors into floating rotors. Haven't used them, but I wonder how much of a difference that would actually make, if any.

Centric branded Miata rotors are $12.08 for the rear and $13.56 for the fronts.  They're up a bit from the $10 they used to be.  What is the "quality" of the iron?  I dunno, but in decades of running $10 Miata rotors I've never had one fail, including plenty of track use.  Last I checked, it's what the Spec Miata folks were running as well.

Things I care about in a rotor: I like it when they actually include the threaded hole to pop them off the hubs when they're rusted on, but as long as I remember to put some anti-seize on the back I don't need it...  I'll admit that the ones that have coating on the parts that rust are pretty, but not enough for me to, you know, pay for the coating.

Going to have a really hard time convincing me that spending the purchase price of my track miata on a set of brake rotors is worth it:)

With dedicated track pads the OE equivalent Zimmerman rotors are fine. On my 19 GTI I did 11 days on track, and they're still fine to do a few more before the cracking gets to the point of replacement. I highly doubt I'll get 50+ days out of a set of 2pc rotors to make the up front cost worthwhile. The Zimmermans get free replacement at FCP as well.

Also it is worth noting their new policy is you must PURCHASE a second set of rotors before sending in your first set. And you get reimbursed store credit, not money back. So if you don't mind shelling out $3750 for two sets of rotors and THEN you start getting to exchange them with each other over and over using store credit, then yes you're eventually going to get your money's worth. It would take a LOT of track days to do that though.

In reply to flatlander937 :

Since they're doing store credit now, don't you have to send in the old brake rotors first?  That way you get the credit to use it for the new brake rotors.  Not exactly convenient anymore....

In reply to docwyte :

You must PAY for a replacement first.

Buy item X (#1)

Use it.

Buy another item X (#2)

Return item X #1.

Recieve store credit.

When item X #2 wears out, you can use store credit to buy item X #3. 
 

Return Item X #2. Get store credit, etc and now you're rotating through your two purchases via store credit.

But for $1800 worth of brake rotors, you've gotta have the money to purchase a second set in order to get store credit... not a cash refund.

spedracer said:

I have two-piece rotors on my Miata and can get just the rotor rings (vented, non-directional) for ~ $30 each. Currently trying a set of higher-end rotors with the fancy slots, directionally vented, etc. I'm bad at keeping notes, but they don't seem to be at all worth it. Feel/performance is honestly not perceptible to me. Pad life doesn't seem to be significantly different. I bought them "used"-but-BNIB, but they are something like 5x the price. I'm stock powered but with a Dynapro 11.75" BBK, ...

11.75x.81"...sounds like a Wilwood kit.  Be careful with using the cheap Wilwood rings, as they have a tendency to crack on the inside, as pictured here below.

I use their Spec 37 directional line, but with the plain face.  Better metallurgy, better cooling, and they don't have those "windows" near the center that cause premature cracking.

Berck said:

Centric branded Miata rotors are $12.08 for the rear and $13.56 for the fronts.  They're up a bit from the $10 they used to be.  What is the "quality" of the iron? 

The 120-series "premium" rotors are the best you'll find in an OE style replacement.  Note that Centric and Stop Tech are the same company, and the rotors are made in the same foundry (in China).  But Centric also has a cheaper line...don't get those.  It's all about the quality control.

FCP Euro is basically a core charge. Buy replacements, send in old ones, "core charge" refunded. The core charge is just equivalent to the cost of the new rotors.

--

There seems to be some confusion here on two part rotors.

Part 1 is the hat, which is hub-specific and usually application specific. That's the part that costs a lot, up front. Almost all of them made for street cars use a standard 8-bolts-on-7" circle pattern. There are some stock cars which use an 8-bolts-on-7 5/8" pattern and Midget cars that are 6-bolts-on-5.5".

For your street car you want 8-on-7". The hat does not get replaced between brake changes  it is, theoretically, a non-wearing part (the hub underneath is a different story).

Part 2 are the rotors/rings/discs which bolt to the hat. You replace the bolts and discs. Disc diameter has to match your caliper mount height, but: 11.125" x 0.81" is one common size and 11.75 x 1.25" is the other common size, both on the 8-on-7" pattern. Rotors start at about 25 bucks and go up to 4-500 bucks a piece.

---

On a small, light(er), low powered, rear-wheel drive, exceedingly common, car, you almost certainly can't destroy the brakes fast enough to warrant switching. 

Once you start changing that equation, larger, heavier, higher powered, FWD/AWD, less common - the costs of rotors and frequency of changing them can make sense. There is also the ease of changing them. The two piece hat system makes rotor swaps a much easier job overall. 

Andy Hollis said:

11.75x.81"...sounds like a Wilwood kit.  Be careful with using the cheap Wilwood rings, as they have a tendency to crack on the inside, as pictured here below.

Yeah, I did this to several sets on my turbo Miata -- one of them went from brand new to this in about 3 track sessions.  It does it on all of the ears, in opposite directions on either side.  It's literally tearing the ring off the ears.

I asked Wilwood about it and they said that that rotor was never intended to go anywhere near the road course and to use the Spec 37s instead.  So I did and that was the end of that problem.

In reply to codrus (Forum Supporter) :

Good point!  I really never knew that.  
 Thanks for the information.  

DocRob said:

The hat does not get replaced between brake changes  it is, theoretically, a non-wearing part (the hub underneath is a different story).

Hats can wear out. I've had to replace the Stoptech hats on my C6 Z06 due to the hat-to-ring mounting holes elongating. The fasteners themselves were also worn. While the brakes were still completely functional, they sounded like I had metal playing cards stuck in the spokes any time I turned the steering wheel. It was so loud that random drivers and pedestrians were flagging me down.

Stoptech told me that that the rings / hats were still safe to use as long as the rings met the minimum thickness spec, but I changed them because I was tired of the added attention.

In reply to DocRob :

Gotta disagree with you here.  Two piece rotor/hats are not easier to swap vs one piece.  One piece rotors you remove from the car, put the new ones on and you're done.  Two piece rotors you remove from the car, disassemble a whole bunch of small bolts that are probably seized in place, reassemble with new bolts/rotor ring and then put on the car.

As I've already pointed out, the economy isn't there either, maybe it is for cars that can use Wilwood kits, but not cars that are using Stoptech/Alcon/AP Racing/Girodisc/Brembo parts/kits....

I was overheating the stock Miata brakes* installed on my Midlana car (1,700 lbs and 400-530hp), so went with a Wilwood "big brake" two-piece kit from V8 Roadsters. Expensive but absolutely solved the brake issue. Never had to replace anything because they were never stressed.

* I briefly considered Miata Sport Brakes - until I picked up one of the discs. They were so heavy it wasn't even funny.

Interesting discourse on the subject. I just upgraded our 1994 Accord for Champcar from Wilwood DPHA calipers and 98 Acura CL Rotors (same bolt patten but rotor over hub vs. the Accords hub over rotor design) to 11.75 two piece rotors. Using a hat that had to be drilled out for 4x114.3 and Coleman directional rotor rings and a bigger Wilwood caliper. Sebring this weekend will be the first big test with them. We made the move because we kept destroying the centric rotors after one race (granted 14 hours of racing) it never quite had a confident feeling pedal. 

If this doesn't work we'll be going back to a all OEM setup of NSX/Legend GS Calipers and Legend GS rotors. 

docwyte said:

In reply to DocRob :

Gotta disagree with you here.  Two piece rotor/hats are not easier to swap vs one piece.  One piece rotors you remove from the car, put the new ones on and you're done.  Two piece rotors you remove from the car, disassemble a whole bunch of small bolts that are probably seized in place, reassemble with new bolts/rotor ring and then put on the car.

As I've already pointed out, the economy isn't there either, maybe it is for cars that can use Wilwood kits, but not cars that are using Stoptech/Alcon/AP Racing/Girodisc/Brembo parts/kits....

IME seizing in place isn't usually an issue, but it definitely takes more time to do the ring/rotor swap, especially if you're safety wiring them in place.

They are expensive when compared to large volume single piece rotors.  The thing is that for a lot of the applications where you use rotor-on-hat there is no large volume single piece rotor available.  Rotor-on-hat is cheap compared to the cost of a fully custom single piece rotor.

In reply to Andy Hollis :

Thanks for the heads up, will steer away from them in the future. Not sure if I'm just slow, if its because I'm stock powered, or its because I'm paranoid and knowingly change rotors way early, but I haven't run into that in probably 3 sets of the cheapies.

The track you race at makes a major difference..  

    Elkhart Lake is 4 miles long with 3 really long straights and tight corners st the end of each.  Total of 14 corners on the track with enough straight between them to get up some great velocity. 
  When the Indy cars come they put their biggest  air scoops on  and often replace everything on Saturday.  Same with the Trans  Am  cars.   I flushed race brake fluid between each session.  
      Having brakes that still worked towards the end of the race could get you back a lot of lost positions.  
     Brainerd is a 3 mile track that you get to the same top speed on the main straight but the corner is a big radius turn with a decent sized straight following it.    There is enough straight after each corner so the rotors are no longer glowing  when they are next called upon.  
     Mid Ohio is more like Elkhart Lake but not as long of straights and some of the corners don't even require braking. 
 Laguna Seca is relatively easy on brakes. So is Watkins. Glen. 
Same with Road Atlanta. 
         

frenchyd said:

 Laguna Seca is relatively easy on brakes.

Laguna actually has a reputation for being really hard on brakes, at least locally.

In reply to codrus (Forum Supporter) :

Maybe compared to other tracks in that area, but I've never had any sign of brake stress at Laguna. High Plains Raceway, on the other hand...

There are a bunch of technical reasons to use two-piece rotors - more dimensional stability, less heat transfer to the hub, less (useless) unsprung and rotating mass - but they're rarely the cheap option unless you're making something really weird like putting circle track brakes on a VW van.

In reply to Keith Tanner :

I see nothing weird about circle track brakes on a VW Van; I'm a fan of huge brakes on Swiss army knife vehicles.

Keith Tanner said:

Maybe compared to other tracks in that area, but I've never had any sign of brake stress at Laguna. High Plains Raceway, on the other hand...

I haven't driven High Plains or the midwest tracks mentioned above, but Laguna's by far the hardest track on brakes of any of in California.

In reply to codrus (Forum Supporter) :

Thus the "in that area" comment :) What I'm taking from this is that brake systems designed to handle California tracks may need a little more work elsewhere...