I am currently running 180/160 HS1 rotors, with an IS adapter at the front, and a PM adapter at the back. How much will I save going to 160/140 (including the lighter IS adapter, and ditching the rear PM adapter)?

According to r2-bike:
HS1 180 mm: 123 g
HS1 160 mm: 90 g
HS1 140 mm: 77 g
140 to 160 PM adapter: 35 g
160 to 180 IS to PM adapter: 19 g
160 IS to PM adapter: 14 g

Going from:
(123+90+35+19) g = 267 g

To:
(90+77+14) g = 181 g

That's a drop in weight of 86 g. Does this sound reasonable?

You will save a bit more at the rear as you have to use shorter bolts for the caliper too. But otherwise it seems correct.

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/jonas l
http://cerrol.wordpress.com (my cyclingblog)

large frame bikes tend to come with 180/160 discs - and I did conversion to 160/140 - got the data somewhere on the saving but will be converting to 160/160.

You lost too much power going to a 140 rear disc?

Depends on your riding and brakes.... I run 160/160 which are more than adequate for me at 85Kg ready to ride.

What brakes? I have Shimano (M765 ish - one lever and caliper are saint M800 which are the same with different paint) so put an IS caliper (M965) on the rear which was a saving of 43g when comparing the 2 bolts I was using to an adaptor and extra pair of bolts although the caliper is slightly heavier with it's arms.

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Impoverished weight weenie wanna-be!
Budget 26" HT build viewtopic.php?f=10&t=110956

It'll be standard XC riding. I weigh 69 kgs, and I've got SRAM X0 brakes on my bike (29er hardtail).

For XC, even with Xo, you should be fine on 160/140.... get some lightweight discs like alligator and they would be lighter for 180/160 than the HS1 would be for 160/140 though.

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Impoverished weight weenie wanna-be!
Budget 26" HT build viewtopic.php?f=10&t=110956

As far as I can see, 160 mm Ashima Ai2s weigh 65 g each (lighter than Alligator Aries).

Two of those, including the other hardware will be:
(65*2 + 14 + 35) g = 179 g

So 2 g lighter than 160/140 HS1.

However, there was that guy on a road bike that had problems with the Ai2s on an alpine descent on his road bike. I'm not saying I'll be doing anything like that on my mountain bike, but still...

More info plz!

for my weight, about 40% more than you, 140 mm plus lightweight rotors i.e. where a lot of air replaces the metal braking sruface result in a gentle retardation as opposed to pin sharp stopping.

emike: I'm not saying it was only the rotors' fault. It would probably have happened no matter what rotors he'd used.

It's kinda old news too, but since you asked: http://www.bikerumor.com/2012/02/14/roa ... they-work/" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;

I ended up going for 160/140 mm HS1 discs. I also got rid of the CPS washers (which aren't supposed to be used with 2013 X0 brakes!) and got some shorter titanium bolts. Weight savings: 102 g.

What I took off:


What I put on:

I have the new xo trail brakes and switched to 160/140 because the brakes were to strong. I went with Hope lightweight rotors and I really love the set up now. I can still lock he read wheel up with ease but I feel I have more control with the 140.

Scott

this topic answered my question also. thans to you all!