School me on rotor size *noob*

[plpete]

I'm slowly gathering parts for a fast gravel bike and might entertain trying cross. This will be a custom Trek Boone build with Sram Rival 1X. This being my first foray into disc brakes I'm trying to figure out the disc situation. Like I said, majority of riding will consist of longer gravel riding, farting around on local towpath when I need a chill recovery ride and maybe trying some cross. I will probably also use the bike during winter with some more road friedly tires.

I can run either 140mm or 160mm discs or a combination of both. I've seen all set ups but I'm not sure what are the benefits and possible cons of each. Given my planned riding, what would be the best set up here? Also, any centerlock disc recommendations would be awesome

[joejack951]

How much do you weigh?

For centerlock, I keep hearing good things about SRAM Centerline rotors but Shimano Icetech rotors are working great for me. I’m 66kg and do just fine with 160mm front and 140mm rear, and would probably be fine going smaller up front, too.

I went 160mm solely because I had a 160mm front on my commuter bike that I used for years but I was a bit mislead by that experience. The bike and rider (me) were heavier back then and I only had a full mechanical front disc and canti rear, which never got used. With front and rear HY/RD-caliper-braked discs now and less weight to slow down, a 140mm front likely would still be more than adequate.

[plpete]

I'm around 70kg give or take.

I've been looking at SRAM and Shimano too. Could probably get the Shimano ones for less. Sounds like I could do 140 front and rear?

[kafreeman]

I'm 100kg on a good day and run 160F/140R. No problems here.

Hydraulic 685 shifters and 785 post mount brakes. RT99 centerlock rotors IIRC.

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[jlok]

I'm 73kg and I still like to have 160/140 combo.

[Nefarious86]

160/140 gives a more balanced feel, 140/140 can risk cooked rotors on longer less forgiving descents and 160/160 can result in a locked rear wheel under heavy braking if you aren't delicate on the levers.

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[Oyekoituhai]

The bike and rider (me) were heavier back then and I only had a full mechanical front disc and canti rear, which never got used. With front and rear HY/RD-caliper-braked discs now and less weight to slow down, a 140mm front likely would still be more than adequate.???

[cerro]

I use 140/140 on both my gravelbikes, lighter and looks better. But when I was down in the alps and rode with bags it was a bit too small. So depends on where you live. I'm 60kg and uses Sram Centerline rotors which I really like, think the new Shimano rotors look pretty ugly.