icyclist 

I've rented bikes in the valley. They'll be available in May. However, as mentioned above, the bikes are cruisers; they come with balloon tires and they're heavy bikes. On the plus side, once you start moving, inertia will keep you going in the Valley, which is fairly flat.

Assuming you are fit, you could ride the entire valley in a day on one of the rental bikes. You could pedal the entire width and length of Yosemite Valley, including every road and all the bike paths. There are probably less than 20 miles of legal riding. The loop road, with a bailout point half-way through, is about 8 miles around.

There is no legal riding anywhere in the park off a road or off a bike path. You'll see signs at places leading to Mirror Lake and Yosemite Falls, etc., where bikes aren't allowed. You don't have to worry about anyone stealing the rental bikes - no one would want one of those behemoths.

So if you want a good workout, you'll need to repeat your rides, or reverse directions on the bike paths (the roads are mostly one-way) if you go with a rental bike from Yosemite. (I've also ridden my fixed gear bike in Yosemite Valley several times; it's the perfect place for fixies.)

The bike paths in Yosemite Valley itself are safe and easy; just watch out for other riders and pedestrians. While the roads in the valley are somewhat narrow, there aren't many and they're mostly two lanes. They're all fine if you're careful.

If you rent a road bike or mountain bike outside the park and bring it with you, then you can sample, as mentioned above, the steep roads leading out of the valley. Those roads lead for miles. However, I've rarely seen anyone ride outside the valley, because all the roads are long and steep and narrow.

• Highway 41 takes you up about 1.5 miles or so out of the valley to the famous Tunnel View. It's a steep climb. After that, it's mostly uphill to Glacier Point. That's about 28 miles from Yosemite Lodge,which is in the heart of the Valley. As per above, the roads are narrow and you'll have to be prepared to have cars and buses slip past you with inches to spare. That would be a good day's ride, and you'd want to be in fit condition.

Highway 41 can also take you about 20 or so miles past the turn-off to Glacier Point to the Mariposa Grove of sequoias. On the way, you'd get an 8-mile downhill ride from Glacier Point to the store/gas station/historic hotel at Wawona, and then another five miles or so uphill to the Grove. That could be an all-day ride, too.

• Highway 120: it's about 11 miles from Yosemite Lodge to the little community of Foresta. There's a steep 4-5 mile uphill stretch and then a wonderful downhill run for a couple of miles to some historic barns (e-mail me privately and if you'd like to know more about the barns and the area). With a mountain bike or a cross bike, you could ride down a dirt road from Foresta into the Merced River Canyon at the community of El Portal. You'd have a long, steep, ride on another narrow road back along Highway 140, up the river canyon, or you could reverse course and head back to Foresta and then down to the Valley.

Or you can continue past the turn-off to Foresta and continue on Highway 120, pedaling up the continuing steep road for a few miles to the store/gas station at Crane Flat. From there, the road leads about 45 miles to Tioga Pass, almost 10,000 feet above sea level.