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2-piece Floating rotor set-up design

2-piece Floating rotor set-up design

2-piece Floating rotor set-up design

Hi everybody,

I am working on designing a 2-piece floating set-up for a road car (that will also see some track time).

I understand the fundamentals of the floating rotor design.
I have the rotor material (G3000 Grey C.I)
I have the Hat material (6061 Alu)

I have seen rotor temperatures on a very similar set-up approach the 1100F mark on track, so I am using 1200F as my upper limit for operation temperature.

There are two dimensions for float: Radial and Axial

Given the thermal expansion coefficients, you can easily calculate the amount of radial float that must at least be present.

My question is: How to control the axial float?
I understand most race car set ups are not concerned with the noise that is generated with a floating set-up, however I need to have spring preload and still allow for axial thermal expansion.
I have experience using a set-up that uses belleville washers in between the bolt head and rotor flange. This allows me to torque the hat to the rotor without having relative movement.

How should I determine the amount of float needed in the axial direction? We are accounting for both thermal expansion and movement in the suspension/braking components bolted to the uprights.

This seems a little open ended, but I am looking for advice. If there is anything missing from this post that may be needed to pose an answer, please let me know.

I appreciate it, thank you.

RE: 2-piece Floating rotor set-up design

Do you design for a preload that does not exceed a value that would prohibit radial expansion? - Thinking out loud here...

RE: 2-piece Floating rotor set-up design

You know what - You are right, this was a little lengthy, I apologize about that.
I was able to figure this out. Calculate the force generated to move a given amount due to thermal expansion at your operating temperature. From there you can select your spring rates.

RE: 2-piece Floating rotor set-up design

The floaters that I have seen used on the street used a shoulder bolt to seat the nut against and then a belleville washer between the nut and the floater to allow for the expansion and movement. The length of the shoulder was developed to give a certain amount of precompression of the belleville between the nut and rotor when the nut was seated against the end of the shoulder.

RE: 2-piece Floating rotor set-up design


With disc brakes you can use axial float of the rotor or axial float of the caliper. Racing disc brake systems usually allow radial and axial float at the rotor-to-hat attachment and use rigid caliper attachments. Most automotive disc brakes use a rigid radial/axial rotor attachment, and an axial float of all/part of the caliper.

Racing disc brake rotors are attached to the hat using "hat bushings" like this: http://www.apracing.com/drawings/CP2872_1000CD.pdf

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