About 34-miles, 45-minutes, via Rt 25-Meredith, Rt 175-Holderness, Rt 93-Exit 28, and Rt 49-Campton & Thornton from the big intersection in Meredith to Waterville Valley, which has rocky, hilly, mountain bike trails and paved roads for smooth tire biking.
WV pay trails system for mountain bikes doubles as the cross country ski trails/winter.
WMNF multiple use trails, pedal bicycles welcome: Livermore Rd, a dirt, single lane, 7-mile long Forest Service road with a locked steel gate that excludes all motor vehicles ..... $5/day or $30/year/WMNF- windshield sticker to 'pahk yah cah' at Depot Camp forest parking lot which has solar powered, public toilets. Parking pay rules are heavily monitored on weekends. About 2 1/2 miles up the hilly dirt road, at the small bridge, the pay-WV mountain bike trails start across the bridge, a $6-day pass ($5-senior/youth) is required, and monitored, especially on weekends. You may get away with no pass on a quiet weekday, but on the weekend, you will be stopped.
Local town roads: 5-mile local WV loop, includes ski area and forest roads
NH Route 49 in Campton, Thornton, & Waterville Valley: 11.297-miles of state road with a 3-4' foot wide, smooth, paved shoulder lane on both sides of the two car lanes, traveling along close to the Mad River and the WMNF, good for road biking.
https://en.wikipedia.org/wiki/New_Hampshire_Route_49 ... NH 49 at Campton Pond, on the Mad River just above the Campton Dam .... a small photo of Rt 49 shows the shoulder space, approximately 3' to 4' wide, that's actually very good for pedaling a bicycle, and is a great feature for a New Hampshire state road like this. Someone really knew what they were doing when they designed NH Route-49! In December 2017, the speed limit for motor vehicles was increased from 40 to 50-mph by the NH Dept of Transportation but that seems to have made only a little change in people's driving habits on this road. It gets a lot of local police attention from the three towns and still seems like a safe road for bicycles. These two 'bicycle lanes' are mostly 3-4' wide with some areas on the curves narrowing down to maybe 2'-3' wide.
https://www.visitwatervillevalley.com/bike The speed limit for motor vehicles drops from 50-mph on NH-49 down to 25-mph where it enters the village/golf course/town square area of Waterville Valley, which makes it a lot safer for bicycles to share the road.
The WV town square area has a pond, town swim beach, grocery, sandwich store, public rest rooms, huge indoor ice skating arena always 40-degrees inside, mountain bike trails retail center, and bike rentals.
Snow's Mountain chairlift runs in the summer, and is set up for carrying one bicycle/chair with a big hook welded to each chair lift support...... is an old, slow 1960's two-seater chairlift ... and the old Snow's Mountain ski slopes, a former small local ski area, got developed and sub-divided into super expensive homes. It also has close to the bottom of the hill, a large, high, artificial synthetic ski surface, practice ski jump designed for inverted aerial ski maneuvers .... with ski-jumpers walk'n back up the jump hill .... flying down the slope on skis, going airborne, twist'n 'n turn'n, and landing on a large, inflated, air bag. This ski jump is about 100-yards in length, running down a steep slope, next to under the old chair lift, and not designed for bicycles, only for ski jumpers.