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there are ti, and alu rotors.. but SS is still the best material for rotors... there are nice lightweight alternatives like the floating rotors Steve mentioned...or rotors like Alligator or Ashima that are very light eventhough they are SS
 

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Meh.
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They aren't true floating rotors. They're 2 piece rotors. It does help with heat management to an extent as well. You are right, the carrier is very wide, and sometimes the rivets rub up against the adapter or caliper.

There are titanium and aluminum rotors, but Ti and Al have lower friction coefficients. And you can only use certain pad compounds. Stans makes a coated aluminum rotor, but the coating wears off rather quickly if you ride in mud. I don't think Magnesium would be a very good material...

Stainless is indeed the best option. There are some designs that are plenty light. Check out the Save Some Weight forum.
 

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So, Will, what's the difference between a 2-piece rotor and 'floating' rotor? I've done a fair amount of searching and I'm not sure that I'm any the wiser. All examples of floating rotors that I can find, for moto and MTB, are more or less identical to the Hope rotors. What am I missing? Is it simply that there is a lack of lateral play?
 

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Meh.
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Looks can be deceiving. Yeah, it has to do with the lack of lateral play. The Hope's blade is riveted to the aluminum carrier. It doesn't move. As far as I know, there are no true floating rotors for MTB.

http://www.zeckhausen.com/Brembo/Rotor_Replacement.htm

Above is an example of Brembo's floaters. The aluminum expands at a different rate than the iron. To compensate, the mounting holes are oval shaped. It uses clips and bushings to prevent rattling. The hardware allows the rotor to move and expand and all that.
 

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Good information, cheers. The page I found covered the floating design for motorbike brakes. The 'float' of the Hope rotors is directional, that is to say the main rotor moves along the length of the button/rotor, rather than laterally, is it would on the motorbike floating or semi-floating rotors.
This 'play' can be felt by applying the brake and rocking the bike back and forth, as you would to check the headset (a good thing to bear in mind when checking headsets on bikes with 2-piece rotors!).
 

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A wheelist
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XSL_WiLL said:
There are titanium and aluminum rotors, but Ti and Al have lower friction coefficients. And you can only use certain pad compounds.
I tested Ti rotors for someone who was thinking of importing them. They were awful and did everything badly - except their weight.
 

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Photog Cyclist.
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Well from my youth when I raced motorcycles--on the racetrack not the road. I had Performance Machine floating front rotors. There was a carrier that bolted the the rims and a SS braking surface with these round donuts that held the SS rotor to the carrier. You could grab the braking surface and move it side to side--rattle it--quite a good amount too. This gave the rotor room to expand when heating up under braking,

Why not on MTBs--they rattle and are noisy and nobody wants that. But for pure downhill racing they might be a good thing--but I don't know if anybody makes a true full floating disc for MTBs
 

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Hopes are floating. Walk into any motorcycle shop and grab the front rotor on any sport bike. Write back and tell me if it moves. If it move by touch how loud do you think it would be rattling down the trail.
 

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Photog Cyclist.
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Production motorcycles don't come with floating discs you need to go aftermarket with PM or Brembo to get a true floating rotor. Read the link SteveUK put on "floating or semi-floating" that write-up sums up my experiences. And yes they are noisy
 

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Professional Sociopath
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The Hope 'floating' discs are not compatible with some other makes of caliper, my Hayes doesn't sit so the carrier 'rivets' catch on the body of the caliper, so ask around if you are thinking of going down that route.
 
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