0Anthony @ LGMotorsports

Hi guys,

Many of you have been asking me about brakes, and what is right for you. So I thought I would start a little tech corner and go into some of the more popular questions.

Two Piece Rotors


There are many companies out there that offer two piece rotors as upgrades for your car. So what makes a two piece rotor an upgrade?

WEIGHT
By changing the center section of the rotor from a heavy cast iron piece to a lighter material like aluminum you can remove a lot of un-sprung and rotational weight from your car. In some cases over 10 lbs per corner can be lost. Loosing rotational weight will give you a car that can accelerate and decelerate much quicker than it did before. Un-sprung weight lets the shock and spring package do more of what it was designed for, holding up the chassis.

COOLING
Most two piece rotors are going to have an upgraded iron section for better cooling effiecency than the OEM rotors. Not only that a lot of companies are adding in vanes and fins to the hats of the rotors to further help pump air to cool the rotor. The aluminum hat is also going to dissipate heat quicker than the iron, which transfers less heat into the wheel bearing assembly.

KNOCK BACK, FLOATING OR FIXED
Most street customers will not notice this, but you road racers will. There is always some flex to the brake assembly, and tolerance in the parts assembled. As the loads increase you have deflection at the bearing, and this causes the entire rotor to move as well. This movement causes the pads to be pushed, and the pistons to be pushed into the bores. When you apply the brakes you must first take up the slack and push the pads back out, then the brakes start to work. This is not a comfortable feeling for a race car driver to have to pump the brake pedal going into a corner.

Base Corvette's and most production cars have a floating caliper so the caliper just slides on it's pins and moves with the rotor. The Z06, ZR1, and most aftermarket companies use a fixed caliper which is must stiffer, and more likely to see this under hard use. There are ways to stop this from happening. One is to use a good quality wheel bearing like an SKF but that is only part of the solution. The next step in the solution is going to be to float or not, your rotors.

Not all two piece rotors are going to be of a floating design and everyone uses a different method to do so. At the same point not everyone needs a floating rotor.

What a floating hat and rotor does is allows all of the hardware to remain tight, but give a small gap between the hat and the iron so the hat can move with the bearing and the rotor spin true, even if they are not running 100% parallel with each other. This acts like a shock between the two giving you a more consistent brake pedal at the track.

There are numerous ways to do this from small bobbins, to drive flanges, to twin plates. Every company has it's own trademarked floating and attachment system to do so. StopTech and Brembo use a small drive pin, or bobbin that bolts through the hat and rotor. Alcon uses a bolt on stand that the rotor slips into, sandwiching the hat but not bolting through it. PFC uses a similar design to Alcon only uses a full plate on the back side (see above figure). Most are going to have some noise to them, which typically sounds like loose coins at low speeds depending on the design. Some like Brembo have 'anti-rattle' clips which dampen most of it but do stiffen the assembly. Some like StopTech can be built either way fixed or floating depending on customer setup.

LOOKS
Nothing says performance like a Big Brake kit filling up your wheels.





If you have questions about upgrading your rotors, or your entire system let me know. I would be more than happy to assist on any specific kit you have in mind.

63Corvette

Great writeup. Thanks Anthony

LEAVINU

This is what the forums are all about.

PeOR

Nice write up. Two questions from me:

My one piece rotors tend to crack after 6-7 track days. With One piece slotted rotors the cost is about $170 per rotor. If I go two piece with for example the cost is $380. Is it realistic to think the two piece rotor will last twice as long?

Do you ever save the center piece and just buy the outer rotor?

PeO.

John Shiels

You just buy the outer rotor ring and sometime hardware. Hat can be used multiple times. One piece tends to crack faster because of the one piece shape. Ring can expand easier because it does not have the center hub in one piece.

tstar

Like John indicated, floating rotors also allow the friction ring to expand and contract seperatly from the hat during heat cycles helping to eliminate cracking... I honestly don't know if TOTALLY eliminates cracking but it certainly helps.

Here are a few shots of the ones I have showing the attchment hardware;

John Shiels

two piece does not always mean lighter even in the same diameter.

0Anthony @ LGMotorsports

That is very true. Typically in the larger sizes it does, but some of the smaller ones like a 12 or sometimes 13" it will not due to the hardware weight and also it will depend on the thickness of the rotor material. Some narrow the vanes and make the sides thicker, which adds material and weight.

Painrace

GREAT write up, Anthony. I am going to miss you guys at RA this year.

Jim

airspeed247

Great Info. Thanks

0Anthony @ LGMotorsports

John has some very good points.

Most two piece rotors are going to have a slot on either the hat side or the rotor side because of the two dissimilar metals and the fact that they expand at different rates. This isn't so much as to keep the rotor from cracking as it is to keep more life in the hat.

Hat life is going to depend on how the setup is used, a street car is not going to be nearly has hard on parts as what a race car is. You will get an idea after a season or so on how long rotors and hats will last you. Hardware should be replaced EVERY time you pull one of these guys apart, especially the systems using the bobbins. Again depending on the race car but we might do hats on a StopTech kit in the challenge cars every 5 races, the ALMS car maybe the same or more, depending on the length of the race. Keep notes on your car and you can get an idea. Some of my street/HPDE guys are going almost two full years on the same hats.

Most aftermarket rotors are going to be of a better material and cooling design, so yes they should last longer. 2-3x longer, I doubt it. Again depends on how the car is used. I think driving style and pads do more for rotor life.

Do shop around when you are looking at two piece rotors and big brake kits as rotors are going to be a consumable part and some systems can be almost twice as much as other kits but not offer twice the life.

C5inWV

PM sent

UstaB-GS549

Why replace hardware? I helped a friend replace rings on a Nissan GTR using AP Racing rings and hardware. The fasteners were Gr.8.8 and the recommended torque was well below yield. The bobbin takes the shear load and probably would not fall out even if the fasteners were missing.

0Anthony @ LGMotorsports

Always been good practice, especially on the race cars.

Most companies will send new hardware with the rotors. You have to think it is more than load, as all of those hardware pieces see not only stress but heat transfer as well.

There are a few designs, and this goes back to how each company wants to do it, that you would not have to replace the stands, but new bolts and nuts would be a safe practice to get into.

Zenak

Are these them on the website:

http://www.lgmotorsports.com/catalog...oducts_id=1908

Thats the pair cost? Or per rotor? Whats the cost on the rings to replace?
Im assuming ring price is with bolt replacement hardware as per this thread?

0Anthony @ LGMotorsports

Those are the StopTech units that are currently on hold from StopTech. When they do bring those back, replacement rings retail for $255/ea and do come with all new hardware.

John Shiels

Why are they on hold? Can I still get OEM C5 style I have?

0Anthony @ LGMotorsports

Just the Z06 units have been put on hold. The C5 units are still being produced and yes you can still get rotors for those as well.