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Hello Juraj, what first should be addressed is the reason for the upgrade in sizing. If you are unable to slow sufficiently with the current set up at 160mm, then upsizing front can make a difference in some cases. If braking feels maybe just a little slow, then upgrading rotors and/or brake pads can make a difference as well. A few Notes: -Depending on the model year of the frame, Salsa designed the rear to accommodate 140mm and 160mm rotors, and nothing larger. In this case my reference was a 2020 Cutthroat frameset (before UDH). --This is pretty common as flat mount brakes are in that 140-160 range for most bikes and designs (slowly changing here in 2025). -The Cutthroat Carbon Deluxe V2 Fork can accommodate up to a 180mm rotor -Front Braking is most of your braking, so this would be the one to upsize to 180mm. ---Officially, an approved and tested 160 to 180 flat mount adapter for SRAM Road groups doesn't seem to be available. May need to go aftermarket. -A Larger rear Rotor will just stop spinning once enough braking force is applied like a 160mm, then just slide across the terrain. Effectively the rear is just a support to the front, especially when loaded with gear. Bikepacking.com here actually made an article about 180mm adapter options in 2022: https://bikepacking.com/gear/180mm-brake-rotors-on-flat-mount/ Depending on which specific shifters you have, you may also be able to use a 4 piston MTB caliper with the road levers for more contact on the rotor and apply more pressure. This would also require a flat-mount to post-mount, so may not be worth it. With more information regarding brake lever model, specific bike model year, and what issues are currently presenting with braking I may be able to get a bit more specific for you. Cheers!

I asked Salsa and here's what they had to say... So, the front is pretty straight forward – you can use a 180mm rotor on the Cuttroat fork by installing the rear standard, 35mm +20 adapter. I’m currently running this now with Shimano GRX. SRAM has the same adaptor available. The rear is more involved and is technically not compatible to set up a flat mount caliper with a 180mm rotor, as there is not OEM solution to go from a native 140mm frame to 180mm rotor. That being said, there are a couple aftermarket options – one would be to convert the brakes to a post mount system using a rear post to flat mount adaptor and SRAM post mount brakes that utilize DOT 5. SRAM does not officially market a post mount caliper that is compatible with drop bar controls, but I have successfully set up a gravel bike with a 2-piston LEVEL caliper. The only other option that I can see is to order one of a few adaptors that allow 180mm rotor spec with flat mount calipers. I have not personally tried any of these, but just ordered up this one to test fit - https://peak-torque.com/products/180mm-rear-disc-rotor-adapter-for-flat-mount-road-gravel-frames. This article poses one other option - https://bikepacking.com/gear/180mm-brake-rotors-on-flat-mount/. I DO NOT know if the ladder solution will work as it my interfere with the frame, especially under flex, but we also don’t have 3D of this adaptor, but the 3D below moves the Shimano adaptor into the position needed for a 180mm rotor.

This is a tough one to answer without having the bike on hand for some classic trial and error. If I had my Cutthroat still, I'd try some options to see what worked. It seems to me that any +20mm adapter should work, but, I think your best bet is to take it into a well-stocked bike service shop that might have some adapters on hand. I have used the Shimano adapters with other brand brakes, for the record. That bit shouldn't be an issue.