Just built up some lighter weight wheels for ‘normal riding’ (KOM i25, DT 350, Revs) and saved about 120g’s per wheel over my current ones.
Now thinking of saving a bit more weight – rotational mass and all that.
Currently have Hayes V8(200g) and V7(160g) as it’s what I had lying around.
Is anyone running lightweight rotors and, if so, which ones and are they any good?

I use these http://www.xcracer.com/shop/viewproduct.php?productid=172 . No complaints so far.

Be careful of the ones that just have big holes in the pad area, I had some previously and they were very juddery under braking. Those KCNC ones look good.

I’ve been pleased with these;
http://www.xcracer.com/shop/viewproduct.php?productid=224

Shimano RT76 for me, marginally lighter at best but probably not worth it as a weight saving exercise.
I have run Ashima Airotors in the past and didn’t like them. They had far more cut-out than actual braking surface and the large size of the cut-outs caused some pulsing effect on the XT brakes that I was running.
I wouldn’t recommend.

[edit] basically, what somouk said [/edit]

RT76. Fit forget
RT66. Fit forget + cheap

I’ve used a few pairs of lightweight rotors.

Some are better than others, and some work with some brakes and not others.

Despite what GCSE physics says, surface area and friction are related when it comes to brake rotors, there’s considerably less power than with a solid rotor.

On the plus side pads last for ages because they run that much hotter and shed mud/grit/water quicker.

I’ve gone back to OEM rotors and wouldn’t go back to the lightweight ones except on a very XC build where I’d already shaved every gram off and braking wasn’t an important issue.

Alligator Windcutters here – Definitely experience some pulsating on front – but it’s not that bad – overall I’ve been happy with them ..

On the plus side pads last for ages because they run that much hotter

*puts hand up*

Sir, I don’t understand.

Mostly they’re barely any lighter than sensible rotors tbh. I have airotors on my xc bike just because I already owned them but they’re only like 20g lighter than the “sensible everyday” formula ones like I use on the big bike.

Formula lightweights- with the millions of holes- perform exactly like normal rotors but wear stupidly fast and unevenly so not really fit for everyday use. Airotors are pretty brake-dependent, I really didn’t like them with my old oros, they were juddery and inconsistent but with my the ones they work well- longer pads I think reducing the effect of the big oles?

Discs with big oles don’t necessarily give less power, it’s counterintuitive- you’d think more surface means more friction, but less surface means more pressure on the surface that’s there.

I ran the ashima ‘explodydeathanhiliatorotor’ for a bout four years, they were fine plenty of power but unless your weight weenie-ing the difference in weight is pretty minimal

Sir, I don’t understand.

Less material means that power goes into heating them quicker, and less surface area means they can’t dissipate that heat as quickly.

My Windcutters in the spares box are blue, and were only ever used for XC. The Avid rotors on the #ENDURO Gnarpoon still looked new despite probably doing a lot more braking.

And hot rotors mean pads last longer because the surface is hardened by the heat during bedding in, so keeping them hot keeps them bedded in. More solid rotors allow the grit to wear off the surface, quicker than the heat can harden the newly exposed pad.

you wheels are hardly weightweenie, just fit the V7’s

you wheels are hardly weightweenie, just fit the V7’s

I’m not looking for ‘weight weenie’ reductions. I’ve just noticed that there are lighter rotors out there. The Hayes are heavy for standard rotors..

^^^^
But providing your happy with the performance of a disc such as the kcnc (I am) why not save 170gms 4.5gms per £1 is a bargain when your weightweening.

For some riding lightweight discs are fine.

For some riding I wouldnt.

Personally i choose shimano.

Brakes are probably one of the first places I wouldn’t want to shed weight.
Take a dump before you ride, or fit a lighter tyre.

Besides, whilst the disc are rotating weight, they are nearer the centre of the wheel, so dont have as greater effect on rotational weight as weight loss from the outer circumference of the wheel.

And hot rotors mean pads last longer because the surface is hardened by the heat during bedding in, so keeping them hot keeps them bedded in

Is that why mine always feel a bit shit until they get hot at the start of a ride? Like contaminated pads.

I have used lightweight rotors for years without any issues until I tried ceramic pads on them, despite the shop saying “Reduces damage to rotor“.
I still use them on my lightweight 29er.

people notice more judder from rotors with significant cut-outs, does this judder contribute to early wear in the bushings on the brake side of the fork?

Take a dump before you ride,

I love the way this old chestnut always pops up when the talk is about lightweight bits 😆 Weight of the bike is more to do with how the bike feels, not necessarily going faster. In any case I always have a dump before I ride and my rotors are light as well. 😀

OH GOD

lightman – Member

I have used lightweight rotors for years without any issues until I tried ceramic pads on them, despite the shop saying “Reduces damage to rotor”.
I still use them on my lightweight 29er.

I ran the ashima ‘explodydeathanhiliatorotor’ for a bout four years, they were fine plenty of power but unless your weight weenie-ing the difference in weight is pretty minimal

Not really, upto 100g per rotor.

But, if you do go for the really lightweight Ashima ones and then notice the performance start to suffer – it’s because you’ve worn them out… Just thrown away the one on my HT, now only 2/3 the thickness of a new one.

The juddering did it for me on the Ashimas. I’m sure the more solid rotors work a bit better too.

what size rotors are you running?

what size rotors are you running?

203mm F, 180mm R

Less material means that power goes into heating them quicker, and less surface area means they can’t dissipate that heat as quickly.

Surely a fat chunk of metal will take longer to heat up and cool down than thin piece.

I suspect they heat up quicker and cool quicker.

IME pads don’t last as long in heavily holed rotors as they do in standard. I destroyed a set of EBC resin pads on one dry lap of the Marin with Ashima rotors, only run sintered with them now for that very reason.

Similarly, used these for a few months which have also been good with XT’s (can’t justify the cost of XTR!) –

http://www.xcracer.com/shop/viewproduct.php?productid=297

I fully committed to the weight weenie cause and went 160mm both ends which meant that I got rid of the calliper mount as well.

But then I weigh 65kg, and this is on my XC race bikes. Braking power is slightly reduced going to the smaller front rotor, but nothing dramatic, and still fully controllable with one finger – just needs a bit more force. Metal pads have lasted well thus far too…

I have these ^ and I don’t like them because they seem to eat pads in the wet. Almost like they chop through them or something.

I bought the these Quaxars which have been ridden and raced for about a year. Front 1/2 way worn and I’ve just replaced the rears – they weren’t worn all the way but enough to have made me nervous if the 24hr I did was wet:

http://www.xcracer.com/shop/viewproduct.php?productid=299

Stopping power about 95% of the RT76’s they replaced IMO.