This is my experience putting TRP Hy/Rd disc brakes (disk brakes) on a V20. I'm sure this info has been covered on this forum in various places, but since I had to stop and order more parts every step of the way, I'll summarize my experience in case it helps someone else do it more efficiently.
I made a video (which really should of had a 2nd take) to help here:
https://www.dropbox.com/s/qrb9gesubph2yc7/TRP_Hy_Rd_Parts.mp4?dl=0
Once you have the right parts, installation and adjustment is easy as shown by TRP:
https://www.youtube.com/watch?v=_8T6cON6y_Y&t=108s
1) first thing you need know is what rotors your wheels take. Most take 6-bolt rotors, but mine took centerlock rotors so I had to order them and then order lockrings. The centerlock rotors I'm using were made by TRP and the lockrings are Shimano SM-HB20.
2) next thing you need to know is adapters. The V20 frame has International Standard (IS) mounts and the TRP Hy/Rd calipers are for Post Mount (PM). You'll need an adapter to go between. These adapters for upright bikes have different spacing for front and rear wheels, so the adapters are sold as front and rear adapters. What does that mean for Cruzbike? Well what I learned from multiple orders is you only want REAR adapters for both the drive and non-drive wheels. In my case I put a 140mm rotor on the non-drive wheels so this needed a Rear 140 PM to IS adapter. I put a 160mm rotor on my drive wheel so this needed a Rear 160 PM to IS adapter.
Examples:
Rear 140:
http://www.trpbrakes.com/category.php?productid=1231&catid=188
https://www.amazon.com/RavX-Disc-Br...491925727&sr=8-23&keywords=disc+brake+adapter
Rear 160:
http://www.trpbrakes.com/category.php?productid=1187&catid=188
https://www.amazon.com/RavX-Disc-Br...25968&sr=8-3&keywords=ravx+disk+brake+adapter
3) you'll need a little longer brake cable for the non-drive wheel. It will need to be at least 2100mm.
4) I think the largest rotor that would fit in the back is 140mm. On the front you could go 160mm or 180mm.
--Doug
P.S. After two shoulder surgeries and 6 months unable to ride off the trainer, my surgeon has finally given me clearance to start riding this weekend. I'm hoping I can still balance it. Does the statement "like riding a bike" apply when you've been off a Cruzbike for a long time? I'll comment on how much I like the disc brakes after they are burnished in.