floating rotors

[Cement Legs]

Ive been trying to find hardware at McMaster to mount floating rotors but do not know what the specific name for those pieces would be.... can someone pls enlighten me....

[kwancho]

If I recall correctly, the part is called a float button.

[jack]

yes, it is a button, and let me know if you find somewhere you can buy them alone (without a rotor or spider too). every where i found, you couldn't just get buttons. thanks.

[Alan]

You can buy bobbins from EBC. I'm not sure its in their catalog but they do sell a kit. We found that they worked better when we got our own snap rings from McMaster. You can also get floating hardware from Performance Friction however its more for the style of brake where the rotor bolts onto the hat (the hat and rotor mounting suface are not in-plane).

[Jersey Tom]

We just made our buttons in-house. Quick and easy.

[Denny Trimble]

http://www.apracing.com/car/brakedisc/bobbins.htm

[Cement Legs]

Hey Denny in the spec sheet at that site am I correct to assume that the nominal float is the lateral movement of the disk allowed by the bobbins?

[Denny Trimble]

I would assume so, if you look at the disc flange width and bobbin length columns, the difference is the float.

[kwancho]

So, correct me if I'm wrong, but the AP racing ones have a 1/4" through hole to bolt the button to the brake hat, right? Seems like a heavy solution to me.
I can't really tell, but I think the Spiegler ones (http://spieglerusa.com/cfm/rotoracc.cfm) require basically a semicircular hole in both the rotor and the hat, and the button goes between them. Is that how it works?

[Jersey Tom]

I still think you might as well just make em in house. So cheap and easy. What is it, like 7 bucks for a foot of some 3/4" dia steel from McMaster to make em?

Simple lathe project, good for beginning fabricators.

[Ian McMurdo]

To all the people that are running floating rotors, how are you justifying this? We have never run floating rotors in the past - just bolt steel rotors right up to an aluminum hub, and have never had a problem with the hub or rotor cracking from stresses due to expansion. Not saying you shouldn't run floating rotors, just curious as to what your reasoning is. I'm designing the brake system for our car this year and I'd like to stick with fixed mount rotors for the sake of simplicity and cost. I've yet to log any temps off the old car and do calcs to justify this, but that is my plan.

[Jersey Tom]

Eh, I'm tryin to justify the same this year. I mean its good design practice and makes sense to why its good but I don't know if its measurably better than bolt-on.

[Kirk Feldkamp]

I would seem to make sense from a manufacturing standpoint. I don't know if you've ever had a rotor that wasn't centered in a caliper, but it usually makes for a soft pedal. A floating rotor would allow manufacturing to avoid being hardcore on the production tolerance for the stackup of the assembly, thus reducing cost. I figure the bobbins are about the same price as a high temp nut and bolt.

Small gains? Maybe. Side benefit of a better pedal feel? Probably. Bitchin'? Definitely.

-Kirk

[Jersey Tom]

Bitchin'? Definitely

That's the kind of design engineering I'm talkin bout.

"Allright. How do we justify titanium tophat bolts with silver plated nuts?"

"Dude. That shit is bitchin"

".. allright. I'll sign off on it"

[Nick McNaughton]

Tolerance stackup problems might be reduced, but to avoid loading problems with delicate brake rotor material you've still got to be very careful. The big gain is in freeplay/pedal takeup, with a big reduction in knockback at the caliper and more confidence from the drivers.

[Kirk Feldkamp]

Originally posted by Jersey Tom:
That's the kind of design engineering I'm talkin bout.

Aww come on. Someone around here these days has to have a sense of humor.

...that is unless you were joking, and then I'd just feel like a dumbass.

-Kirk

[terra_dactile]

Hello,

We had fixed mounting on the disks in 2006 and had many issue with warping, they could warp so bad as to push one side of the calipers piston back enough so the back of the pad on that side was almost rubbing against the caliper,

Possible advatages for floating rotors,
limited resistance and wasted power from warped disks rubbing in stead of turning freely

Better pedal feel less play in system

Disks that float generaly get hotter since less heat is disipated at mounting, so they might get closer to ideal temps for the friction coefficient of the pads.

It was one of the flaws that was mentioned by the majority of the judges from Continental Teves during the brake award presentation i made Detroit 2006 and California 2006,

Floating rotors done properly is deffinately the way to go to have an efficient system.

By the way Mr kwan, AP Racing has the exact system you mentioned, however it is used on GP Motorcycles front rotors.


Jude Berthault
ETS FSAE 2003-Current
Vehicle Dynamics Leader

[ahaidet]

check out www.braketech.com (http://www.braketech.com) call Jeff Gehrs he sold us our buttons/bobbins. They worked well, however are a bit pricey at about $5 a piece. Any rate I would try and make them if I were you. We are making them this year on a small CNC lathe.

At any rate we were able to loose nearly a 1 pound per front rotor last year with a floating design. Partially because of the ultra light center carriers we made. Partially because we ran a smaller diameter. Also at elevated temps the floating rotor helps to allow the rotor to freely expand.

[J. Vinella]

We saved some weight and complexity going from buttons to a fixed rotor design.

[kwancho]

Really. I was going to ask you guys at UW especially what buttons you used.

[J. Vinella]

Well, we used to use the AP racing buttons as mentioned by Denny in this thread, but last year we went to quite a different design. Truth be told it isn't the classic bolted rotor design.

[Homemade WRX]

we made our own last year...really simple to do, of course dependant on design.

[Vinnie]

what kind of different design would that be, Vinella?? interested in sharing??

cheers

[J. Vinella]

The design utilizes a spline to match the rotor to the spindle/hub.

[Homemade WRX]

yeah, the two major designs being used in floating rotors being your motorcylce and automotive designs...all in how the rotor lines up with the hat and this changes how the bobbin has to be shaped...
I'll see if I can find some pics to illustrate what I mean because I suck with words http://fsae.com/groupee_common/emoticons/icon_razz.gif

[Samo Simonian]

Hey ya,

I was responsible for the design of the Inner Wheels including spider/hub front and rear last year. We used a 200 mm 'Braking ' disc in the front. And mountain bike brake discs on the back (have to confirm size). Both front and rear AP callipers: 'Motorcycle Rear 2 Piston Caliper Family No. CP4226'.
Both ways we used fixed bolted design. Together with a questionably stiff mounting of the brake calliper and fixed disc-to-spider mounting we ended up with a warped brake disc in the front. The rear is also slightly bent. Don't know if this is a real design error. We used the standard mountain bike fixed mounting holes. Might be judges and interested people going; 'OOOO that looks nice 'n thin, lets bend it to feel if it is really thin, qweeeeek, yep it is!' Our pedal feel also wasn't very good, but that was partly due to questionable bleeding, and pedal box stiffness. I think the parts themselves were ok.
For this year the new guys from brake system will have a look into the floating versus fixed mounting. I think you can really gain on performance by choosing floating design. Of course this depends on disc and spider stiffness, offset between the two, materials used and more. But it will in many cases relieve the two of significant loads.

Interesting topic,

Samo Simonian
Chief Suspension
DUT Racing 2006/2007
www.dutracing.nl (http://www.dutracing.nl)

[Sathersc]

Just out of curiosity, does anyone use the Wilwood hats? My brake guy is set on using them, but I don't think they justify the cost do they (he's telling me $75 for 8 hats).

Oh, and J. your avatar made me crack up when I finally looked at what kept bothering me out of the corner of my eye. http://fsae.com/groupee_common/emoticons/icon_cool.gif

[drivetrainUW-Platt]

Could I see some pictures of how you guys are making your rear hubs to integrate these buttons, I a intersted in doing it and cloudy on how to impliment it.
We are using atv cv's with a splined stub shaft for the hubs.

[Sathersc]

We're doing it similarly to how the Toyota developed FSAE car in the gallery section is set up. That's one of the better pictures I've found on how it can be done on these cars.