I'm confused. I thought you said that you two bought a bike... for you? You went cycling together... so I thought that meant you have a bike too?

I think we all know that our body tells what is good and what is too much. Honestly, I don't know if anyone can tell you if that is too much or not.

Really, the only thing I would warn you against, would be mashing on the pedals and not spinning. I think runners turned cyclists, have a tendency to think they have to muscle through the stroke, not realizing that it doesn't take that much muscle to turn the pedals fast... if you know how to use your gears properly.

Now, I never ran as much as you... but I never had any knee issues, until I started riding a bike... because my fit wasn't good at first (my cleats were locked into the wrong position on my clipless pedals), and I was mashing the pedals.

Good luck and it is important that you ride a bike fitted for you.