Are two-piece rotors worth the extra money?

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...

This thread now has me wondering what a machine shop would charge for machining a combined hub / hat for Mopar 11.75" brake rotors, where the hub and rotor are a one-piece casting.

In my case 2 piece rotors come stock on the front (GR Corolla), so I have no inexpensive replacement options, especially as they can't be rebuilt. Stock or aftermarket is about the same cost, so I suspect when it does come up, I'll get aftermarket so that my consumable cost can go down next time. This is definitely an unusual case though.

In reply to RX8driver :

A lot of BMW and Audi plebemobiles come with two piece rotors now, too.  They have a separate hat and rotor and are permanently assembled at the factory.

It's pretty neat, it allows the rotor to grow in diameter without being warped by being affixed firmly to a cold hub, while being constrained rotationally and laterally.

Other vehicles like Fords get the same effect by having "bent fingers" in the casting.

I have some friends that race in Lemons.  They have a 240SX with a V6 swap. One of the team members purchased a used car that had a "big brake" kit installed. It was Wilwood calipers and 2 piece rotors. They asked me to adapt these brakes to their race car. I made new mounting brackets and when looking over the rotors found that they were the same thickness and diameter as the standard Ford "Cobra" rotors the Mustangs used from 1994-2004. The cost of these rotors from your local Napa is about 1/3 the cost of just the Wilwood rotor, and your don't have to safety wire all of the attaching bolts the Wilwood 2 piece rotors use.  They have since converted to the Cobra rotors.

I road raced and open tracked a Mustang back in the 90's and found the stock  Cobra rotors to be good for a season of open track or a few races. I later upgraded to Wilwood rotors & calipers and while better than stock the improvement wasn't quite worth the cost when only club racing.