[Mr. 5]

I met up with a company the other day that is interested in making a 2 piece rotor for the 335i.
The hat will be made out of forged aluminum.
The disc will be made out of high carbon alloy and heat treated iron.
There are many more details that could be explained but I'm just starting this thread to gauge interest.

The weight savings per rotor will be approximately 3-4 pounds (each).

[The HACK]

If I'm not mistaken, RacingBrake is already in development with a 2 piece direct replacement. Their 2 piece rotors are what I have on my MZ4 Coupe (my primary track vehicle).

This will be a REAL upgrade as opposed to drilled or slotted rotors on a one piece replacement. A 2 piece rotor will save weight, prevent heat from transferring to the hub, and provide better air inlet for cooling. The typically cooler rotor temperature will also extend pad life too.

I'm surprised no one has come out with a 2 piece offering for the E9X 335i yet (RB is still a few month away from a prototype for testing if I'm not mistaken).

[DJKhan85]

I have been waiting for this. I want all the benefits of a 2 piece rotor but I don't have the need(yet) for a BBK. I would be down for a set.

[m1bjr]

Be careful what alloy they use for the carrier hub.
It should be a heat treated aluminium that will take repeated heat cycling.
These are normally spun from a solid piece of metal.
Forged parts may be raceparts but are not always designed to last more than one race

[Mr. 5]

Originally Posted by m1bjr

Be careful what alloy they use for the carrier hub.
It should be a heat treated aluminium that will take repeated heat cycling.
These are normally spun from a solid piece of metal.
Forged parts may be raceparts but are not always designed to last more than one race

Cool. I'll keep that in mind but this company makes 2 piece rotors already for the general public with no issues whatsoever.

[m1bjr]

Originally Posted by Mr. 5

Cool. I'll keep that in mind but this company makes 2 piece rotors already for the general public with no issues whatsoever.

No problem, sounds like no issue at all then.
I got a company here in England (Compbrake) to make us some for the S2000.

If going for track work, have a word with your guys in Carbotech USA.
The XP pads are simply awesome - very expensive but last twice as long as a Ds2500 for example and no fade.

Fir a cheap performance mod, take off the front water shield when you take off the rotors.
It's only held on by a few short M4 bolts. The cooling ducts in the front apron send air right to the wheel but its largely pointless as the dust shield masks it from cooling the darned rotors!


Edit: Just looking at your homepage and the Cool Carbon pricing... damn they are cheap?!

[Tee212]

Whats the ill effect of heat transfering to the hub/wheel? and why would you not want for it to do that? the only benefit i can see from a 2p rotor/hat would be just less unsprung weight?

[The HACK]

Originally Posted by Tee212

Whats the ill effect of heat transfering to the hub/wheel? and why would you not want for it to do that? the only benefit i can see from a 2p rotor/hat would be just less unsprung weight?

For PERFORMANCE APPLICATIONS, where heat generated by the braking system can exceed 1,100º F, if that same heat gets into the bearings and hubs it can potentially cause the bearing to seize.

Secondly, metal expand due to heat. Again, for performance applications that heat will cause the rotor hub to expand and contract and potentially damage the bearing hub surface or the wheel mounting material (studs or bolts). A floating 2 piece design will allow the rotor disc to expand independently of the hub thus preventing heat stress on the hub.

Third, for performance applications, you NEED improved airflow through the center cooling vanes in a rotor (if it's got a vented rotor design). If you look at typical cast one piece rotors, there's only one way for the air to enter the center of the hub and it's typically open on the inside, covered up by a brake dust shield. An open, 2 piece, floating rotor design allows air to be drawn in from both side of the rotor hub through the center of the disc and typically has much larger area open to ambient air to draw from.

Lastly, for performance applications, you can use a much lighter material for the rotor hub, and make the rotor disc sweep area much thinner to shave a lot of weight off of the rotors without sacrificing significant sweep area. Plus the hubs are typically re-usable since the rotor rings are attached via expandable fasteners, so for example, on the MZ4 Coupe it cost $300 to replace the front 2 piece euro floating rotors, since the fastener hardware is CAST into a sandwiched hub so when you replace rotors it will cost me $300 each time. On the RB 2 piece rotors I got, the original rotors cost $350 (I get a nice discount with them from my industry connections), the replacement rotor rings are $120 ea. Doing the math, on my third set of replacement (approximately one set every two year, if tracked heavily) it would be cheaper to replace.

[Tee212]

Thanks Hacks! your posts are always useful!

[ah gon]

just wondering...i can order any size of the rotor right?i have 325i with 335i front brake.but i can't put my rear on since the 335i's parking brake r bigger so the inside space of the rotor r bigger.which mean i can't use my e-brake!
if any size can do,which mean i can have 335i's size rotor with 325,328 size for parking brake right?

[lpphreakx06]

In for a set for daily driving, nothing to crazy

[The HACK]

Originally Posted by ah gon

just wondering...i can order any size of the rotor right?i have 325i with 335i front brake.but i can't put my rear on since the 335i's parking brake r bigger so the inside space of the rotor r bigger.which mean i can't use my e-brake!
if any size can do,which mean i can have 335i's size rotor with 325,328 size for parking brake right?

No.

The "hub" portion will have to mate to the specific hub, meaning a 2 piece rotor designed for a 335i, unless the 335i has the same size "hub" and rear brake mechanism as the 325/328, won't work for a 325/328 period.

HAVING SAID THAT.

All the 3 series have the same basic hub design. The difference between the 325/328 and the 335i in the rear, is the actual parking brake mechanism (in addition to the rotor size, of course). You've probably already know, you can bolt on 335i rear brake rotors and caliper and caliper bracket, but you will LOSE the rear parking brake functionality.

When UUC used to offer their Wilwood big brake kits, what they did was use rear brake applications from the 330 on the kits designed for the 323/325/328, and insert a "ring" inside the hub to accommodate the smaller diameter hub of the 323/325/328. One kit works for all the E46es except for M3s. I suspect the E9X is the same way.

RB IS developing a one piece replacement for the 328i I believe.

[ah gon]

Originally Posted by The HACK

No.

The "hub" portion will have to mate to the specific hub, meaning a 2 piece rotor designed for a 335i, unless the 335i has the same size "hub" and rear brake mechanism as the 325/328, won't work for a 325/328 period.

HAVING SAID THAT.

All the 3 series have the same basic hub design. The difference between the 325/328 and the 335i in the rear, is the actual parking brake mechanism (in addition to the rotor size, of course). You've probably already know, you can bolt on 335i rear brake rotors and caliper and caliper bracket, but you will LOSE the rear parking brake functionality.

When UUC used to offer their Wilwood big brake kits, what they did was use rear brake applications from the 330 on the kits designed for the 323/325/328, and insert a "ring" inside the hub to accommodate the smaller diameter hub of the 323/325/328. One kit works for all the E46es except for M3s. I suspect the E9X is the same way.

RB IS developing a one piece replacement for the 328i I believe.

thanks!
but i just don't want to lose the function of the parking brake.
try to looking around see which shop can do the custom rotor for my rear brake.
btw,what is "RB"? vendor?

[tlrid3r]

If you guys are looking for a good set of 2 piece street rotors check DBA Brakes.

[Mr. 5]

Originally Posted by tlrid3r

If you guys are looking for a good set of 2 piece street rotors check DBA Brakes.

I've seen those but the price is crazy expensive.
2 grand for 4 rotors is out of this world.
This company will be much more affordable.

[The HACK]

Originally Posted by ah gon

thanks!
but i just don't want to lose the function of the parking brake.
try to looking around see which shop can do the custom rotor for my rear brake.
btw,what is "RB"? vendor?

RacingBrake.com. They're located in Fullerton, CA. I've done some preliminary testing work for them on my MZ4 Coupe and on what used to be my 350Z. They don't do "custom" work, but I can tell you this...Your problem isn't really that big of a deal. Measure the inside diameter of the 335i rotor hub. Measure the inside diameter of the 325i rotor hub. Have a machine shop make a "ring" out of cast iron with the outer diameter .0001" LARGER than the 335i rotor hub (or the closest tolerance the machine shop can get to) and the inner diameter the same as the 325i rotor hub. Mill the ring to approximately 3/4" thick. Take a butane torch and evenly heat up the hub portion of the 335i rotor, then insert the machined cast iron ring into the hub and wait for the assembly to cool naturally.

VOILA. 335i sized rotors that will work for the 325i parking brake. You may have to experiment around a little as to the placement of the ring, but MY experience on the E46 is the ring just has to sit FLUSH with the small indentation in the larger hub. I'd have to see the inside of the 335i rotor hub to confirm if this will work.

[stressdoc]

Stillen and DBA have two-piece rotors. But they are not cheap. Who could resist a set of four for around 1k?
I was hoping to get my brother to work up a set of ceramic composites for us, but the legal issues are big.

[Former_Boosted_IS]

I have also heard a floating rotor setup for the E9x is in the works and should be released in the near future. It appears this may be the year of the brakes for the E9x!

[Mr. 5]

Originally Posted by Former_Boosted_IS

I have also heard a floating rotor setup for the E9x is in the works and should be released in the near future. It appears this may be the year of the brakes for the E9x!

I think so.
A good 2 piece rotor is exactly what we need right now.

[The HACK]

I'd pay more for a 2 piece rotor. I wouldn't pay more for a drilled or slotted rotor.

When my buddy used to work at Brembo, he used to encourage all of his customers and distributors to PUSH drilled rotors. I asked him why point blank, since we both knew there's no tangible benefit to drilled rotors. And the answer is simple. It cost "them" the same to make a set of drilled rotors (or very marginally more) but they charge a lot more for drilled rotors since there's a perceived "performance" benefit in the market. Simply put, there's a demand for it in the market and they'll continue to price it as and market it such, and from a business standpoint it's all PURE PROFIT on their consumer end products.

Unfortunately that is all too true. The way he puts it, 2 piece rotors may be the best thing since sliced bread in braking technology, but they're hard to sell because no one sees it. But everyone will see the drilled holes on a rotor.

By the way I'm still waiting for my 2 piece RacingBrake rotor to wear out after 4 years of very heavy tracking. Mean time my rear OEM rotors are about past due for replacement...Since I couldn't get my Cobalt XR3s to fit in the rear I've been using harsh, track pads up front and OEM-ish or Axxis Ultimate equivalent pads in the rear...And the front RacingBrake rotors are holding up MUCH BETTER than the rear OEM rotor. I don't know what sort of magic they use, but from what I understand the better the cooling, the longer the rotor (and pads) will last. I'm on my 3rd set of brake pads in the rear while just recently swapped out the front pads after 4 years.

Hate to sound like I'm "pushing" products, but the 2 piece rotors from RB that I got for the front (at $350 ea, no less) are the BEST brake upgrade I've done next to the pads...And I've yet to experience any fade issues in the last 4 years.

[Mr. 5]

I heard from a person that worked for Brembo for 15 years...
"The reason for the drilled rotors was for qualifying purposes. They were thinking of ways to make the car lighter and perform better for qualifying and someone thought---We can drill into the rotors making the rotors lighter and therefore making the car quicker overall. During the real race, the rotors used are slotted."

The drilled "look" caught on and now are sold as a performance option.
The rest is history.

[Hedges]

I always love when Hacks post! Full of good information!