# Lightweight rotors for xc (not downhill)



## Gliding_serpent (Aug 8, 2017)

So i was searching for good options to go with my xtr race brakes and scott spark (reasonable 21lbs build). This is for xc use as i just dont live in a mountainous area. So no masquerading as a downhill bike. I also weigh 130lbs or so... so we are stopping 150-160lbs.

I could not come up with a lightweight focused review of the subject... but i did come up with a few things, even if outdated:

FAQLoad - Lightweight disc brake rotors

Right now my eye is on the ashime ai2 rotor for steel construction, and light weight at 66g each. The price is decient also.

Thoughts appreceated as i want quiet, durable, good cost, and light (usually an impossible combo ask) given that i am a lighter guy, and i dont expect to see a ton of abuse on the brakes. No fragile race day only stuff.

Thanks for thoughts, experiences, opinions on what you use.


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## fxrextreme (Mar 11, 2015)

Ive had good experiences with kcnc rotors. Light,cheap and work for me. I even use 203/180 on my am bike
Kes


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## RS VR6 (Mar 29, 2007)

Ai2 for the past few years. Never an issue.


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## Jayem (Jul 16, 2005)

AirRotors and Ai2 work pretty well. I do notice that on extended downhills they heat up real fast and overheat. We do a couple fat-bike races at the ski resorts where we ride down the mountain chinese downhill or interval style, at those speeds and on those slopes, they overheat and I smell burning brake. The rotor doesn't have much surface area to dissipate heat, so not unexpected. For this reason, during summer XC race season, I use shimano icetech rotors, I have found they are extremely resistant to fade and I do a bunch of races with big downhills on em, although I could definitely get by with the Ai2s on many of my other races if I really wanted to push it. I go to a 180 Ai2/Air Rotor on the front to make up for the lack of surface area, but that also means a bit heavier brake-adapter too. In short, these are ok for most "fairly level" XC stuff. If you got big steep descents where you are on the brakes a lot, not the best choice IME.


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## alexdi (Jun 25, 2016)

AI2 was made for you. You could do 160/140. Less in the front, even, depending on about a dozen factors. I run 180/160 at 175 lbs in kit.


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## Gliding_serpent (Aug 8, 2017)

You just made me think that low mass rotors would be better in (proper) winter fatty riding. You get heat in them faster (so that they actually work), and overheating would be a non issue. I am going to be riding in -17oC temps tomorrow on my fatty. Brrrr...



Jayem said:


> AirRotors and Ai2 work pretty well. I do notice that on extended downhills they heat up real fast and overheat. We do a couple fat-bike races at the ski resorts where we ride down the mountain chinese downhill or interval style, at those speeds and on those slopes, they overheat and I smell burning brake. The rotor doesn't have much surface area to dissipate heat, so not unexpected. For this reason, during summer XC race season, I use shimano icetech rotors, I have found they are extremely resistant to fade and I do a bunch of races with big downhills on em, although I could definitely get by with the Ai2s on many of my other races if I really wanted to push it. I go to a 180 Ai2/Air Rotor on the front to make up for the lack of surface area, but that also means a bit heavier brake-adapter too. In short, these are ok for most "fairly level" XC stuff. If you got big steep descents where you are on the brakes a lot, not the best choice IME.


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## Gliding_serpent (Aug 8, 2017)

I was thinking the same. It seems that my "build" allows me to push the limits a bit more when selecting components.



alexdi said:


> AI2 was made for you. You could do 160/140. Less in the front, even, depending on about a dozen factors. I run 180/160 at 175 lbs in kit.


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## Jayem (Jul 16, 2005)

Gliding_serpent said:


> You just made me think that low mass rotors would be better in (proper) winter fatty riding. You get heat in them faster (so that they actually work), and overheating would be a non issue. I am going to be riding in -17oC temps tomorrow on my fatty. Brrrr...


That's pretty much what I do most with them.


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## Davide (Jan 29, 2004)

I am using an Ashima Ai2 160 in the the back of my Norco Olve 21 ... it works fine for my 158 pounds. In the front I have a Shimano 160 (mostly because it felt silly to dump it) and I stick with Shimano 180 on my HD3.

At 135 pounds you should be more than fine with the ashima 160 in front.


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## Erwandy (Jan 8, 2016)

These skinny rotors does heat up fast during descent. But they cool down fast too. And they eat up resin pads FAST! hahaha. But I can't really complain on the performance side, I am happy with the results so far


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## sfer1 (Feb 22, 2009)

The Ashima AiRotor ARO-08 (160mm, 85g) and the KCNC Razor (160mm, 73g) work noticeably better than the Ashima Ai2 (160mm, 67g) rotors. I wouldn't sacrifice braking performance to save 12-36g.


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## alexdi (Jun 25, 2016)

sfer1 said:


> I wouldn't sacrifice breaking performance to save 12-36g.


Horses for courses. Personally, I don't want to cart around a performance reserve I'll never use. My local trail only has 200 feet of elevation change and I try to stay off the brakes for every one of them. Doesn't ask much of the rotors.

I'm comfortable with the recommendation because this OP described weights, riding style, and terrain. Plenty of margin for him. Other folks, maybe not so much.


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## Gliding_serpent (Aug 8, 2017)

alexdi said:


> I'm comfortable with the recommendation because this OP described weights, riding style, and terrain. Plenty of margin for him. Other folks, maybe not so much.


For sure, and i ordered a set (160 front and rear... call it a conservative start).

To be honest, with standard rotors/pads, i generally just squeeze my brakes. Anything else is too harsh, and i am sure i can throw myself off the bike if the tire grip is there. So it was just overkill. My next build is more of a focused trail bike anyway, so i am not building an all rounder.


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## samarskyrider (Mar 22, 2015)

Did anyone try Ashima Flo-tor?


Sent from my iPhone using Tapatalk


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## xblitzkriegx (Jul 29, 2016)

using XT brakes with Ai2 rotors, 180/160. i weigh 195lbs. never had a problem overheating the rotors on any trail ive been on. visited colorado springs and rode nearly every trail there except bar trail, never a problem. rode every trail worth riding in MN, never problem. rode in bentonville in AR, ALL the trails there, not a problem.

i ride as aggresively as you can on a hardtail and i show it no mercy. youll be fine on Ai2 rotors. the other rotors mentioned in this thread are fine too. 

i noticed no difference in braking power between the centerlines they replaced. i do notice at speeds from 0-2mph when braking during technical sections, youll tend to feel the voids in the rotor but braking performance is still strong. i can still lock up the 3" wide front tire if i choose to do so. 

also, still using the stock resin pads and they have plenty of life left. i tend to do very little braking and generally use them sparingly when i do.speed = fun.


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## Ryandurepo (Nov 29, 2012)

i use ashima airotors on my topfuel. Cat 1 midwest, 200 kitted, 160/160 with no problems. Ive actually thought about doing a 140 rear. Running G04ti pads with great life.


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