I added fenders to my Helios P8 and found they interfere with the v-brakes. Has anyone had this problem? Any suggestions for resolving it?
You're not very specific with exactly what the problem is, but you might have to cut away some of the sides of the fenders if the arms on the brakes are hitting the sides of the fenders. This will only work if the fenders are supported with some sort of attachments elsewhere on the fenders, usually a bolt near the bottom bracket and stays near the rear of the fender.
Sounds like you need to drop the fender down closer to the tire. If there is room to drop it down you can buy either a straight or an angle bracket at your local hardware store and either extend or replace the current bracket. It depends on how the current bracket is attached to your fender.
I have also used nylon wire-ties to attach fenders on some bikes where the standard mounting methods won't work.