Floating rotor vs. Solid

[Kaizmuth]

I'm picking up a new Shimano XT M785 front brake. Is there any real advantage to a floating 180mm rotor vs. a solid one? I would think that a floating rotor would have a bit more tolerance to the caliper not being perfectly centered, but I have no real world experience with this. Any thoughts?

[mefistofeles]

I think in theory the answer should be no but my experience the answer has been YES YES YES. For example at one point even though I was using one piece rotors with my Shimano Saint M810's on Giant Faith 0. When I switched the rotors on my Faith 0 to RT-76 and RT-86 two piece rotors I noticed a significant increase in braking power.

Believe it or not I think this is Avid's main problem. I don't think their brakes are bad but their rotors SUCK. I had terrible squealing and vibration problems on my Giant XTC 29er1 (which was equipped with Code 5's). After I changed the rotors to Shimano RT-76 rotors these problems were greatly reduced.

If your rotor vibrates your bike is probably going to vibrate as well. Even if the rotor doesn't vibrate I would imagine that rotor flex is probably going to adversely effect braking performance,which is why I believe the one piece rotors on the Faith 0 had less stopping power than the two piece rotors that replaced them.

However bike weight,suspension travel and frame material play a huge role in stopping power and vibration. I have Avid Code 5's on my Giant XTC Advanced carbon hardtail with one piece rotors but I don't notice any vibration,in fact the brakes on the XTC Advanced stop it better than any other bike I have. In this case suspect I suspect the XTC stops well because it's a light carbon hardtail with limited suspension travel (100mm).

So although two piece rotors are probably better than one piece rotors they may not be neccessary or even desirable depending on the bike that they are attached to.

[LyNx]

Since I just made this move I think I can safely comment. The Shimano 2 piece rotors are not true floating rotors the outer rotor is fastened tightly to the alu spider, unlike on a real floating rotor design where it is not actually fastened, but loosely riveted together.

Still, I prefer the 2 piece rotor, like Misfit I have up till now used single stamped rotors from both Avid and Hayes and I've always had noise issues and never really felt they were as powerful as they could be, but when I switch to the XT M785 I got the RT76 rotor and no noise, loads of power. I only have the front so far (mix up in the order and shipping) but ordered the RT76s instead of the RT86 because most of what I read said the RT86s could be more prone to warping and didn't seem to give anything more unless you had very long descents, which we don't.

[Ilikemtb999]

The rt76/86's are not a floating rotor at all. The biggest benefit of them is just how stiff they are and less prone to bending/warping etc.

Hope makes floating rotors.

[vk45de]

What he said^

Hope rotors can expand radially out from their spider when hot so it reduces wrap.

[Zachariah]

Yep, Hope and Magura are about the only makers of the floating rotor. They both self-cool, when heated up.

[kcvpr]

the main advantage of two peice rotors is the stiffness increase wich helps with warping, and they have better cooling properties because the carrier is often made from some sort of alloy vs the steel of the stamped versions.

[007]

This has been asked, and answered already: Fixed vs. Floating Rotors?

The bottom line is that to the best of my knowledge, there is not one single true floating rotor available for any MTB, by any manufacturer. There are many 2-piece rotors, however, none are truly floating. The closest thing is offered by Hope, which I guess could be considered a semi-floating rotor. There is a KEY distinction though between the Hope's and the other 2-piece rotors, which is the gap between the brake track and the carrier (see the linked thread above for more). Without that gap, there's zero functional purpose to a 2-piece rotor, other than to potentially save weight (even this is negligible with some of the manufacturers).

The Hope 2-piece rotors are very nice. I run them and will so long as they make them. They work, and they work well, especially when paired with an aggressive pad compound. They stay very true once adjusted, and minor warp (from say getting bumped) can self-correct if you get them hot enough. Plus they make fun "pinging" noises as they cool

[giantdale]

True floaters: iso raven sl 82g

[007]

True floaters: iso raven sl 82g

Nice to see that those are finally in production, though I'd wager that they are actually semi-floating, just like the Hope's.

However, at 85 euro's a pop . . . no thank you.

[007]

The biggest benefit of them is just how stiff they are and less prone to bending

I have found the exact opposite to be true. The 2-piece rotors are significantly more sensitive to bumps and bends though are much easier to true.

[customfab]

. They both self-cool, when heated up.

As opposed to other rotors that need to be manually cooled?

[mjduct]

yup,

you pee on them

[007]

yup,

you pee on them

Man, I've been doing it wrong!!

[006_007]

Man, I've been doing it wrong!!

You still have that rotor burn mark on your a$$ from doing a num 2 on them for cooling?

[stumpynerd]

Ran Hope floating rotors for a couple years, the rear however developed play in the rivets. I replaced it with a hope fixed rotor. Didnt noticed a difference in performance, however it still has the inspiring Hope Buzz noise. Love that noise.

[007]

Ran Hope floating rotors for a couple years, the rear however developed play in the rivets. I replaced it with a hope fixed rotor. Didnt noticed a difference in performance, however it still has the inspiring Hope Buzz noise. Love that noise.

I'd say that's pretty normal . . . . any reason for going with a fixed over another 2-piece?

[cfrea]

What size Hope's do you have? I was looking for 180mm but everywhere only seems to stock 183mm

This has been asked, and answered already: Fixed vs. Floating Rotors?

The bottom line is that to the best of my knowledge, there is not one single true floating rotor available for any MTB, by any manufacturer. There are many 2-piece rotors, however, none are truly floating. The closest thing is offered by Hope, which I guess could be considered a semi-floating rotor. There is a KEY distinction though between the Hope's and the other 2-piece rotors, which is the gap between the brake track and the carrier (see the linked thread above for more). Without that gap, there's zero functional purpose to a 2-piece rotor, other than to potentially save weight (even this is negligible with some of the manufacturers).

The Hope 2-piece rotors are very nice. I run them and will so long as they make them. They work, and they work well, especially when paired with an aggressive pad compound. They stay very true once adjusted, and minor warp (from say getting bumped) can self-correct if you get them hot enough. Plus they make fun "pinging" noises as they cool

[007]

What size Hope's do you have? I was looking for 180mm but everywhere only seems to stock 183mm

That's all they make unfortunately. Damn proprietary parts . . . .

[Kanik]

3mm diameter difference? Who cares? Put a washer under your caliper posts.

[stumpynerd]

I'd say that's pretty normal . . . . any reason for going with a fixed over another 2-piece?

Well no, just wanted to try fixed, and not deal with with rivet play issue again.

[Ilikemtb999]

Aren't the rivets what supply the float? Or were you just using a 2 piece non floating rotor?

[stumpynerd]

Yes, its the two piece, I had over 3 mm of play. And the rotor would chatter on the trail, so I swapped it out for a fixed.

[Ilikemtb999]

Hope floating rotors do just that.....float.

[BTTR]

What size Hope's do you have? I was looking for 180mm but everywhere only seems to stock 183mm

Here HOPE Floating Disc 6-Bolt Black - Probikeshop

BTW what's the reason of those 3mm difference? I mean there hare 180-183mm and 200-203mm rotors, why?