Road disc 160/160 vs 160/140mm in the mountains

[mrlobber]

There are numerous threads on road discs vs rim around here (and maybe the question on rotor sizes is buried inside them as well), but let's put that all aside for now.

Due to potential 20-30g savings, I'd be interested to swap rear to 140mm for my "light" disc bike. I live in a flat area, so I'd even be able to run 140mm rotors on road disc all day long, however, given the occasional trips to Alps, I'd like to hear real experiences from people who run road discs in mountains daily or weekly - how much rear 140mm reduces actual braking performance and/or time to heating the brakes up.

My weight is in the 70...75kg territory.

[TobinHatesYou]

If you care about the weight, go ahead. You should only be feathering/trailing the rear a slight bit during aggressive descending. I just think the asymmetry looks goofy so I haven't bothered going 140mm in the rear.

[MarcFaFo]

It is very common to use 160/140 set-up. Also in the mountains I have seen last summer during the Marmotte

[siim]

I used 160/140 this year in Dolomites (Maratona) and it was absolutely fine. My weight is about the same as yours.

[moyboy]

I used 160 160 in the Dolomites (Maratona). I think 140 would work well too. you do not want to lock that rear!
I'm just a horrible descender!

Will be going to a 140 rear this year.

I used 160/140 this year in Dolomites (Maratona) and it was absolutely fine. My weight is about the same as yours.

[tnkn]

I've used 160/140 in the mountains. Was absolutely fine at 68kg.

Not once did I think I needed more stopping power.

[MichaelB]

I use 160/140 on hills with no issue and I’m 95kg.
Mind you, run Zee calipers so a much bigger pad than the flat mount ones

Edit - damned phone auto correct!!

[rainerhq]

What about 140/140 for 67kg rider in the mountains?

[mattr]

Think you'll be into "how good is your technique" there.........

I switched from 180/160 to 160/140 on my XC bike, and while i didn't actually have any problems (the brakes still worked) i did manage to slightly over heat/heat treat the front disc, as far as i can tell, it's hit about 300-350 degrees in a few spots. Difficult to tell exactly due to the fact that it's a friction surface, but the arms were discoloured where they meet the friction surface.
The 180/160 combo i had on that bike prior to that have been on for several years with no issues (and no colouring of the disc at all.)

Best i've seen was a 200mm disc from a tandem that had overheated so badly it had permanantly distorted by about 10mm and was dark blue..........

[nulldreiundreissig]

What about 140/140 for 67kg rider in the mountains?

Sitting at 62kg and living in the Zurich-area with regular trips to alpine passes, I was torn between 140-140 and 160-140, too.
Went for 160-140 ultimately, because it’s only a few grams saved and I felt more comfortable with the option to choose 140s in a second stage.

I’d rather consider latex inner tubes on a disc equipped bike for some easy weight savings than probably sacrificing some breaking power.

[spdntrxi]

Allroad 160/160
TriBike 160/140
Road 160/140

83kg.. no lack of power with the 140