The possibilities for loops like this in Marin/Sonoma are endless. Do you have a Krebs map? You can ride from the city or go start off Lucas Valley Rd. You can include some or all of Mt. Tam, Marshall, Wilson Hill, Chileno Valley Rd., Coleman Valley Rd., Bohemian Hwy.
Honestly there are just too many options and I don't have them all mapped out as individual rides. I usually just do a smorgasbord and decide how I feel. From Mill Valley to Pt Reyes Station and then down Hwy 1, coming back either BoFax or Pantoll is a favorites of ours. That's in the 60 mile range. BoFax adds quite a bit of climbing because you get to do the *ahem* "sisters" on Ridgecrest.
Or From MV up to Nicasio, Cheese factory, Marshall and then down Hwy 1 and either all the way down 1 and over Pantoll of over Olema hill. That's more in the 80 range.
Or go to Nicasio and ride up over Wilson, Chileno Valley, through Freestone, over Coleman Valley Rd then back down over Marshall. That's about 90. Lots of climbing - GREAT loop. 2 bakeries - if you drop into Pt Reyes Station it can be a THREE bakery ride.
Sounds like we should ride.