Come on someone?

I found they induced a weird pulsing/brake judder on the front end.
config: 180 disk on XC hardtail, Reba Teams at 100mm. Shimano XTs with sintered pads.
Changed for Superstar rotors - problem went away.

There's much less metal for the pads to grab, so surely they can't be as effective as a more normal disc, can they?

pulse but light

tell you in a couple of weeks, got one in my kitchen cupboard ready to go on the wheel I may eventually get round to building.

I've got one on the back of my XC bike. Purchased as that was all they had in the shop. Haven't thought about it since putting it on so must work ok. Can't comment on how it might perform on the front.

EDIT: This was a 160 rotor with Avid Elixir CR.

They work fine - friction is independent of contact area in general terms, but wear isn't - so you MAY notice slightly faster pad wear.

I have been using them for a few years now and apart from the aforementioned pulsing, they work just like any others

I've got a pair, 180front on a 29er reba and 160 rear, XC hardtail with XT brakes, superstar sintered pads

nice and light and work plenty well enough for me (90kg give or take)
I can't say I can feel pulsing but they do have a very distinct sound and I could believe the pulsing some report, how much of an actual issue it is not sure.

btw there was a batch with the direction arrows the wrong way so pay attention when fitting 'em if you get some. I ran mine the wrong way for a while, I hadn't noticed until a mate mentioned it and I swapped 'em around a few weeks later.
note I didn't die! 🙄

Interesting about the direction arrow.
I simply assumed that there was a good reason for it to contradict every other rotor I'd previously used. I used it as per (possibly incorrect it would seem) arrow.
Can't see that this would have induced the judder/pulse though.... or could it? Juddering of the forks was certainly visible under braking.

Got KCNCs, no pulse, plenty of power, cheap and light. That'll do me! Very very marginally more pad wear, possibly!

No problem with the Air Rotors, I've been using them all year and find them really good.

I have a 140mm one on the back of my hardtail. Combined with an Avid Clean Sweep G3 160mm on the front, running Elixir Rs, they seem fine. I weigh about 80kg and haven't noticed lack of power, or increased pad wear.

Does rotational direction actually matter?

Does metal have different strength/stiffnes in compression vs. tension?

Does rotational direction actually matter?
Does metal have different strength/stiffnes in compression vs. tension?

If so, then probably not sufficient to make any noticable difference.
I was thinking more in terms of potential effects of any directional differences within the cut-out pattern, but TBH it looks fairly similar either way around !

Contact area does not affect braking friction as smaller contact area = higher contact pressure which is what actually counts.

Bigger disc = more torque so more braking power.

More contact area = better heat dissipation = real world better performance

Lots of cut outs = trade off between worse heat dissipation but improved forced cooling (but also lower radiation cooling) and also can increase pad wear. Due to the higher local contact pressure you can also have increased deflection in the pad material (which causes more wear due to gouging) and can give a spongy feel - not that you will probably notice it on bike brakes with plastic hoses and 2 part calipers etc etc.

As for fitting them the wrong way - you need to have the spokes trying to "open" under braking forces. If you have them the wrong way you are more likely to buckle the disc or have pulsing problems due to radial movement. Especially with lightweight rotors.

I have these on both of my XC bikes (160F 140R). Yes they are light, yes pad wear is slightly increased. I don’t really notice the pulsing, stopping power is fine but BEWARE.! I have heard a few catastrophic failures, Im sure someone will post up a picture of one bent-up before long. Apparently, the older ones are the ones that failed and according to Ashima they have been modified (I have old and new). The only difference I can see is the printed direction of rotation arrow now goes the other way.

If you need to know what is old and what is new I can check tonight. Let me know.

Got a 180 and 160 for sale if anybody wants them.

180 is 2 rides old, 160 is 4 rides old. Didn't like the pulsing sensation they give with Shimano brakes (I've heard with other brakes it's much less apparent due to bigger pads). So gone back to standard shimano rotors.

£25 posted for the pair if you want them.

I got on well enough with them with my XT brakes and my old Tektros but they don't seem to work as well with smaller pads, much more pulsing/roughness.

The direciton arrow thing is weird, they changed their minds about how they should be run after a while so old ones say to run the opposite way round from most rotors, new ones say to reverse that. So one of mine said to run it one way, the other the reverse.

There's a picture that does the rounds of a horribly folded up one, but it also has obvious scorching on it- looks like it's the result of some sort of uneven heat torture test using a gas axe, rather than a real world failure.

I got the KCNC ones and really didn't get on with them - they pulse and judder really badly and produce a really annoying vibrating noise when braking. I've gone back to the bog standard AVID ones but if anyone fancies a pair of 160mm KCNC rotors for a few quid get in touch.

Farmer John.
interested in the KCNC's but you dont have an e-mail address.
e-mail me
thanks