sjanzeir

Hi everyone,

So, now that I've bought my first-ever bike with disk brakes after having been politically opposed to the concept, I'm taking my first steps up the learning curve which, though apparently steep, thankfully seems like it could be a fairly short one with enough practice and a willingness to learn.

So I got questions. And my first 101-level question is about brake rotors - and their shapes, to be specific.

There are the ones that look like they mean business:




There are the weird and wonderful:




The psychedelic, if one's so inclined:




And the ones that look just hilarious:



So, my question is, do the actual shapes of the braking surfaces serve a purpose look like that, or are they just styled the ways they are for pure esthetics?

tyrion

I think the complex shapes are needed to have every part of the pad wiped by an edge of the rotor to clean the pad, in a sense, but not expose the pad to a large edge that might catch on the edge of the pad. Other than that requirement I think the shaping is just aesthetics and branding. Maybe the shapes and holes can aid cooling - I don't know.

The 2 piece rotors supposedly resist warping better.

Andrew R Stewart 

When I face unknowns I often look to other industries and see what they do, and what they claim (the two being not the same). With the money in the auto or the motorcycle businesses being so much greater I would think a shaped, cut away, rotor's being of greater performance (braking wise, not sales) would make this the standard. But we don't see this. Instead we see solid rotors for (likely) 95% of the applications we pay for. Cross drilled or grooved rotors are pretty much only found at the tracks.

Now bikes do have different demands then cars and motorcycles do. Are the differences vast enough to assume that these motorized vehicle versions don't indicate what works best for most of the time? Maybe others have more experience in these things. Andy

shelbyfv

I suppose these are the best road rotors. Look kind of plain jane compared to some of the others.

TiHabanero

Heat. Slotted rotors dissipate heat more efficiently than solid rotors as it introduces more air to the surface by effectively creating a "finned" effect in the rotor itself, much like an air cooled motorcycle engine has cooling fins. Wavy rotors, which are seen throughout the motorcycle industry, are advertised as better at the job, but the guys I worked with in that industry laughed at the idea and confirmed it is marketing parlance, not actually real. It is the slots that clear the dust from the rotor/brake interface and introduce more cooling air as well. The waves are just fancy looking.
"Riveted" rotors, or more accurately called "floating" rotors, offer the advantage of expansion and contraction of the braking surface independent of the mounting points to the hub. Less rotor warp from heat during use. All this learned from engineers and racers when I was in marketing with a motorcycle parts company.
Carbon rotors are amazingly efficient in dealing with the production of heat during braking, and consistently run much cooler than metal rotors. Of course pad material matched to the carbon rotors is paramount. At some point they will be available for bicycles.

alo

Having the gaps makes them light weight, which is ideal for bicycles. The shapes also help clean them.

Cars and trucks need much more strength, therefore solid rotors.

sjanzeir

Thank you all for the informative input. I've been reading up on six-bolt and center-lock rotors and the merits of each and felt that it isn't something I should worry about, given my particular application and usage (like what seems to be the vast majority of bikes, I've got six-bolt hubs and rotors.) Any takes on that?

dsaul

Just 2 different ways of attaching a rotor to a hub. Give it no more thought than which style your hub requires.

TiHabanero

I prefer center-lock because it is quicker and easier to remove or install the rotor. Center-lock is also much easier and quicker to clean behind the rotor. Both center-lock and 6 bolt do the same job.

ARider2

Center lock brake rotors have been largely out of stock at most bicycle parts suppliers while there has been a better supply of 6 bolt rotors available. Also I think center lock brake rotors are slightly more expensive.

adamrice 

You do need a special tool to remove a centerlock, which could be a problem if you're on a tour in the middle of BFE (there is such a thing as a portable lockring tool, although I'm not sure how it would work braced against a fork leg). Admittedly, you're pretty unlikely to bend a rotor.

tyrion

If you travel/ship your bike a lot, you might want remove rotors from wheels, and centerlock rotors make that easier.

TiHabanero

I imagine if on tour and concerned about parts availability in the wild regions of the world, caliper or cantilever brakes are the better choice over disc brakes. No concerns finding brake hose, olives, banjo bolts, etc. should they be needed. Brake cables, pads, and fastening hardware are almost universally and readily found around the world (outer Mongolia exempted, of course).