brake rotor direction?

[madman]

How important do you guys think the rotation of a brake rotor is?  I have an extra GS front rotor and was maybe thinking of trying to use it as a second rotor on a GSXR rim.  The problem is that it would be spinning backwards.  I am not sure if this is a good idea or not.  Can the rotor be removed from the center piece?  If it could, then I could just turn it arounda and reinstall it.  Thanks for your help.

Madman

[KevinC]

I have no idea why they specify the direction of rotation, but since all the discs I've seen have it, I suspect there is a good reason.

Some GS disc can be taken off the carrier. You can even sort of make into a floating style disc. Directions in the "Racer's Corner":

http://www.gstwin.com/racers_corner.htm#susp

[Bob Broussard]

You can simply unbolt the GS rotor from the rim.
I don't think it will work as a second disc on a gsxr wheel. The rotors might be slightly different. The center carrier might be deeper or flatter, so the rotor may not fit in the gsxr caliper properly. The diameters may be different also.
I don't recall ever seeing a directional arrow on a brake rotor.

[KevinC]

Yep, Bob is right on all accounts. The only brake disc I have out of 3 types that has a direction arrow is my Braketech full floating one, and it is obvious why. It is designed to only take braking loads in 1 direction.

It is highly unlikely that a GS disc on a GSXR wheel will line up with the calipers.

[octane]

I don't think stock rotors have a specified rotation - some of the race rotors do, mostly the grooved type.

The GS carrier is offset too far to use on a GSXR wheel. It won't slide into the caliper.

[The Buddha]

Rotor direction is in theory important.... The metal deforms in one direction, and if you reverse it, it could gall and fragment and break. I have never tried swapping rotors from side to side in any of my bikes... so I dont know in reality if it will break or not.
Cool.
Srinath.

[KevinC]

Where do you get this stuff?!

"Gall and fragment"?! Galling is a sliding/sticking phenomona, typically between the same type of metal. If metals fragmented from a change in elestic or plastic deformation direction, it would be falling apart all around us, since that is how most things are formed.

[The Buddha]

OK.. OK.. someone told me... Now constant reversal of loads will prevent any directional deformation. Like rail road tracks. The case in question is where there is a good period of one direction load, causing it to deform. when reversed... would it not sort of roll up like threads and fall off, or sorta have small pieces like little grains fall off the rotor. That's what I meant by gall... not probably the technichal term. never seen it happen, just been told by people.
Cool.
Srinath.

[KevinC]

There are a bunch of metal failure mechanisms, but very few cause grains to fall off - the only ones I know of would be corrosion failures such as exfoliation corrosion that happens with 2024 aluminum alloy.

Reversing loads can cause fatigue failures over millions of cycles, but those are typically just a break. Fatigue also happens much more easily with aluminum than any steel.

I can't imagine why reversing the brake force would cause any metal problems on a SS disc.

[The Buddha]

OK reversing will not cause it to... I dont know the english word for it... lemme try engrish... "get to pieces with thread like elements comming off the rotor"... Sorry man the guy described it to me in tamil... no idea what it is in english... but thread like pieces will fall off the rotor under hard braking if what he says is correct. Ok You say aluminum yes, steel no. And I thought the rorots were mild steel, not stainless.
Cool.
Srinath.

[KevinC]

Nope, didn't even say it would happen with aluminum, just that there are some unusual mechanisms that could make it do something like you described.

Most rotors are stainless steel, so that they look nice. Most racing discs are cast iron because it works better, but they rust very easily. Not a big issue, other than appearance. GP rotors are typically carbon.carbon composites.

I wouldn't worry too much about "thread-like" bits falling off your rotors, no matter which direction they are running.

My Braketech disc has to run one way because the carrier is only designed to take the braking loads out of the floating disc in one direction.

[dgyver]

Stock dual rotors have L & R stamped on the disk. Don't know if the GS has a marking since it is only the Right side.

[werase643]

I love it whe MR GS-BS gets caught in one of them .....what the F^#$ are you talking about scenarios. :nana:

[KevinC]

Stock dual rotors have L & R stamped on the disk. Don't know if the GS has a marking since it is only the Right side.

That's what I had in my mind for some reason also, but I have a pair of stock SRAD GSXR discs, and a pair of stock SV ones, and neither have any direction or L or R stamped on them. Checked twice now, once after Bob's post corrected me.

Ahh, I figured out where I'd seen it, other than my Braketech full-floating ones - I have EBC rotors on my BMW, and they have a rotation direction arrow. I think it must be because of the drilling pattern on the EBC's.

[dgyver]

[BanannaMan]

Strictly from my experiance working on cars......(20 years)

Jack-legs (shade-tree mechanics)will tell you that brake rotors ....of course much thicker and without directional cooling holes on cars...can be switched from side to side.

However........

I have seen the condition Srinath described.
Due to whatever reason...too much heat....poor metal....stress.....sometimes the rotors will become "brittle".
If a rotor that has become "brittle" is switched to the other side...it will splinter or worse.... break.
A rotor that is brittle will also have loud brake noise even with new pads.
Not applicable to bikes but the rotor will also splinter in a brake lathe so it usually gets worse (to the point of being ruined) if you try and turn them.

The condition is rare but......due to this..in the shop where I work...
ALL ROTORS and BRAKE DRUMS ARE MARKED AND PUT BACK ON THE VEHICLE IN THE SAME LOCATION.

Yes...it happens....and I see it about once a month or so on cages.

[The Buddha]

OK so it happens... The guy that told me was an olllllllllllllld timer.... an old army mechanic in India... so I doubt he was totally fibbing.

[TR]

It seems to me that those cage brakes which got britte are due to excesive presure over the disk or drum surface, so they became forged and get fragile, so they were ruined before they were installed to work on the opposite direction, however this would happen only to steel, iron casts are not likely to be forged. The only good reason I found to not to switch rotating direction on bikes discs is perforation patterns or installation design, but a simetrical piece should work fine either way. Only overheated discs would show abnormal grain growth and therefore superficial deformation, flaking or any kind of cracks.