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Discussion Starter #1
First off, thanks for checking this thread!

So the other day I was checking my discs and found that a small crack going to the edge of my stock rear disk. I decided to upgrade to the BOE's as I also plan to supercharge the car in the near future. Got them in today and noticed that one moves around too easily and the other hardly moves under my force. What is considered normal? I'm sure they moved easily under the force of the car and with the heat but is the loose one too loose? It seems like it would make excessive noise and chatter.

Made a quick video as well.
 

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I would imagine they both need to be tightened down... Sounds like you need to get in touch with BOE to find the recommended torque.
 

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The comments are not correct. They're both in perfect spec. Full floating rotors have both axial and radial movement. Axial movement is often felt at room temperature just as shown in the video. Once the rotors bed in and settle, they will both move freely within their respective float ranges (Axially) on the bell in a similar manner.

Hope that helps,

Phil
 

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My floating rotors from sector 111 have spring loaded shims to keep them from moving like that, I'd exchange them. I've also handled dozens of Baer rotors as well and never seen movement like that.
 

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They are floating discs for a reason! That is the way they are supposed to work. What good is a floating disc if the disc does not float? Production tolerances is the difference in drag between the two discs. Under the 1000s of pounds of force that the hydraulic brake system exerts, that 2 to 10 pound difference is nothing. If you don't want them, I'll take them off your hands.
 

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<@¿@>, Exactly:up:

Yellow, you're partly correct. There is such a thing as anti-rattle springs for full and semi floating rotors. They're sometimes used on street cars to prevent low speed rattle with full-floating rotors when cruising around parking lots and the like. Typically, rattle is a bigger issue on street cars with very large rotors. It's not damaging, it's just like running loud track pads on the street... they just can create noises typically heard on a street car. The reality is that a street car doesn't need two piece rotors though.

Your rotor isn't the same animal as ours. It doesn't have any appreciable axial movement, so it's more akin to a semi-floating rotor. It can move radially unlike a DBA 2-piece rotor for an example, which is fixed position and non floating.

Our rotor is certainly designed with the track in mind. It's fine on the street, but WAAAY overkill. Also, you'll find purpose built rotors like ours will typically have 2-6 thou (depends on several design factors) of free axial movement. It is truly a full-floating rotor.

Best,

Phil
 

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Discussion Starter #8
<@¿@>, Exactly:up:

Yellow, you're partly correct. There is such a thing as anti-rattle springs for full and semi floating rotors. They're sometimes used on street cars to prevent low speed rattle with full-floating rotors when cruising around parking lots and the like. Typically, rattle is a bigger issue on street cars with very large rotors. It's not damaging, it's just like running loud track pads on the street... they just can create noises typically heard on a street car. The reality is that a street car doesn't need two piece rotors though.

Your rotor isn't the same animal as ours. It doesn't have any appreciable axial movement, so it's more akin to a semi-floating rotor. It can move radially unlike a DBA 2-piece rotor for an example, which is fixed position and non floating.

Our rotor is certainly designed with the track in mind. It's fine on the street, but WAAAY overkill. Also, you'll find purpose built rotors like ours will typically have 2-6 thou (depends on several design factors) of free axial movement. It is truly a full-floating rotor.

Best,

Phil
Thanks Phil,

My car spends most of its time on the street but that is not my long term intent. I had some sketchy braking issues at my last track event and with the crack that recently formed I wanted to get some quality slotted rotors. Now I'm a bit worried that it's going to be overkill for my car and how my wife is going to react to the added noises. Are they really that bad? If you only notice them in parking lots then it's fine with me. I have so many other rattles coming from the adjustable swaybar and regular Lotus noises.

Next up is the TOC pan :shift:
 

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Cool. Ya, some of the Lotus seem to have very touchy ABS systems, can be overly sensative to "ice-mode" etc. I hope that your car is not one of those!

As far as noise, I doubt you'll notice it all. We make a GTR full floater as well. It's a 15" rotor!-eek-:eek::crazyeyes and you can certainly hear it in parking lots or pulling into the garage. It's huge and heavy (compared to a lotus rotor). However, even on the big GTR rotor once it's rotating at speed, it can't rattle in the same fashion, so there's nothing to hear.

On the little lotus rotor, you may never hear anything. There's just not a lot of mass there to "ring". If anything, it would again just be limited to very low speed bumps, etc and not anything that would draw attention...

Later,
Phil
 

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Discussion Starter #10
I don't have the ice mode problem. In fact I didn't even think my abs worked until I tested it in a safe location last week. The problem I'm having is that the rear end gets squirlley under hard breaking. Everyone at my last track day said they thought I was going to spin out at the same spot. Can't wait to test them out at the track this weekend!
 

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I agree, that is normal for full floating rotor assemblies (without anti-rattle springs).

I have full floating Brembo race rotors. I made my own hats to Brembo specifications, and used Brembo floating rotor hardware, and the play on the right rotor is totally fine. The tolerances that they specify would also allow the tightness of your rotor on the left. The axial gap is supposed to be between .25mm to .5mm on Brembo's system.

I ran mine at first with race pads on the street, and they didn't make any extra noise at all, couldn't even feel or hear the slots. Then later I developed a brake leak from the seals around a caliper piston, and the pads started squealing extremely loudly! I switched to some street pads Porterfield R4s and the squealing stoped, totally quiet (after cleaning the crap out of the rotors and rebuilding the calipers).

You should be fine, just use the correct pad for the correct application. Switch pads between track and street.

If you were getting squirrely in the rear end under braking, then that may point to suspension settings (if yours are adjustable) alignment, or tire pressure.
 

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Discussion Starter #12 (Edited)
Update

I followed BOE's bed in process and did a track day Saturday. Braking performance has improved drastically, especially at 100mph. No more shenanigans in the rear...
 

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The Brembo system of McLaren anti-rattle springs would require several of the screws on each hat to be longer than yours currently are...

Have a look here
How to Replace Brembo Floating Rotors

My brakes do not have the springs, and are loose like your right rotor, and do not make any noise with the correct pads.

My calipers are full race, with totally loose pads, not much holds them in except some slides and a quick release bail to allow you to remove the pads within a few seconds... no noise! No springs, no shims... Just ceramic brake lube.

Here's the rear

front
 

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I am wanting a set of these for my car (front & rear). :D :popcorn:
 

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I am wanting a set of these for my car (front & rear). :D :popcorn:
Are you referring to BOE's rotors or "my" Brembo race brakes?

Cause my brakes would be about $14k new... ;)

But I didn't spend that, designed and made the hats and brackets myself.

Oh, and they probably won't fit on an Elise;) The rotors are 328x35mm, and the calipers are super wide for 1" thick pads and 4 vented titanium pistons.
 

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Are you referring to BOE's rotors or "my" Brembo race brakes?

Cause my brakes would be about $14k new... ;)

But I didn't spend that, designed and made the hats and brackets myself.

Oh, and they probably won't fit on an Elise;) The rotors are 328x35mm, and the calipers are super wide for 1" thick pads and 4 vented titanium pistons.
Where the Brembos are gorgeous...I could only think/dream of affording the BOEs. :)


So BOEs are what I want. So I am curious to see how these pan out.
 

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In that case, floating rotors should only be used on fixed calipers with opposed pistons so you only should need front rotors:)
REALLY!!! I didn't know that. Why is that, only because I wish to become better educated on the topic. Also, what would you guys suggest then for the compliment in the rear? I had originally been considering EBC rotors that were dimpled and slotted.

Just to fill in, I am looking at this mostly as an autocross car, but it is still driven on the street quite a bit. :D
 

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Do the 328s fit inside a 16" wheel? I'm designing a brake system for my '09 Exige Cup 260 and I chickened out of 320s thinking they would not fit inside a 16" wheel.
I can't imagine they would clear. I have AP Racing 315s inside my 16" Team Dynamics and there isn't enough room between the caliper and wheel for wheel weights. My 17" TD rears with AP Racing 330s only have ~1/4" between the caliper and wheel.

San
 
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