In case you haven't figured it out from my earlier routes, some of Taiwan's best cycling is in the Chiayi area.
A real Taiwanese glove
For a weekend trip, I recommend getting down to Chiayi on Friday night because you'll want to be off to a dawn start the next day--it can very hot down here at any time of year. Whether you're coming down by train, high speed rail, or plane, there are a host of reasonably priced hotels (c NT$800/double) in the small streets opposite the rain station.
Day 1
The easiest way out of town is east on Minzu Rd, which eventually turns in to Daya Rd. before finally morphing into Chiayi Route 159A. Let all the tour buses and SUVs get their kicks on Highway 18 (the Alishan Highway) while you cycle in peace on 159A.
You'll cycle pass the Lantan Reservoir the Formosa Freeway, the Renyitan Reservoir, and Highway 3 through some hills. Note the junction with Highway 3--this is the way you will be coming back.
After Highway 3, we knock about 8km in the nondescript countryside of Fanlu ('Aboriginal Road') Township. The fun begins just after the impoverished village of Kezhuang where you climb a few km up to the temple complex at Bantianyan. There is a nice outside cafe on the right just before the temples and some shops where you can stock up on food and water.
Be careful or this might happen to you on 159A
The riding gets really good here. 159A is a wild one lane country road rising from betel nut country up into tea farm country. Almost zero traffic even on holiday weekends. You'll probably need a good four hours or so to reach Shizhuo (石桌) at the junction of 159A and the Alishan Highway.
Shizhuo is a good spot for a late lunch at the restaurant on your left at the junction. There is also a breakfast shop on the right and across the parking on the second floor is a cheap hostel (Minsu) where a double usually goes for about NT$500.
You may well see other cyclists in Shizhuo. That's because you have so many route options from here. You can turn right and head down the Alishan highway to Longmei where you can continue on with the Chiayi-Pingtung ride Rank wrote up in Great Taiwan Bike Rides III. Or turn left ride 55km up to Tatajia, the Yushan trail head. Neither of these routes is recommended on holiday weekends although you might not have such a horrible time with the traffic if you stay in Shizhuo and get off to a pre-dawn start. Whatever you do, stay far away from the town of Alishan, one Taiwan's most horrid tourist hell holes.
Another area to explore from Shizhuo is the Dabang/Jiali area accessible on Route 169 heading east from Shizhuo. SatelliteTV of Forumosa fame lives up in Dabang.
But this loop takes the other way on 169 back toward the tourist town of Fenqihu, a much smaller and tolerable version of Alishan. At Shizhuo, you can stay at the large hostel attached to the Catholic Church and managed by a Polish priest. About NT$700/night.
Tea leaves out to dry
A tradition on Rank bikes rides especially in the summer is to while away hot afternoon by a waterfall or swimming hole. If you have the time in Fenqihu, head down the steep access road toward Zhonghe Village (中和村). This road is a left after the Catholic Church but before you get into Fenqihu proper. The road heads down steeply for two or three km. When you hit some tea fields look for a private access road on your left near a farming shack. If you see signage for an old trail just before a big construction site you have come about 300 meters too far.
Head down the private access road (very steep) to the Yima River (譯馬溪) for some swimming in the cool waters. Be careful though because you are just upstream from the thunderous Xiaocaishen Watererfall (小財神瀑布) and the rocks are very slippery. There is a dangerous path to a lookout point above. Alas we have been unable to discover a route down to the bottom of the falls. I'm sure you could ask in Zhonghe Village. Incidentally, the outside access road connects Zhonghe Village to Fenqihu from 159A if you want to do a brutal climb up to Fenqihu and skip the longer way through Shizhuo.
Day 2
Ride up from Fenqihu on 169 through Taihe Village (太和村) toward the junction to Laiji Village (來吉村). There are places to stay in Laiji if Fenqihu is too rowdy for you. At the Youcheliao (油車寮) junction take 169A on the left. Wind through the beautiful high altitude tea farms. Just before a big down hill, hang out at the view point overlooking the great Caoling lanslide across the canyon in Yunlin County. The devastation here was caused by the 1999 Jiji earthquake. Check if the vendors are selling iced passion fruit or mulberry juice. This is all local produce and supposedly organic. Whatever. It's the best on a hot day.Landslide near Daxiagu closes the road to most traffic...
There is a long descent into Daxiagu (大峽谷) on the Shengmaoshu River (生毛樹溪). Some beautiful water down here. Cross the river and begin the long climb on switchbacks up into Bihu Village (碧湖村). As you can see here, we crossed a landslide that should be fixed by now.
Eventually you will make it to Taiping Village (太平) after a good six hours of riding from Fenqihu. This is the only reliable place for lunch after Fenqihu although snacks and water are available along the way. From Taiping, enjoy the breathtaking descent into Meishan Township on the plains. There are 36 hairpin turns on the way down.
Meishan is a typical country town. On the main street there are a couple of grubby Vietnamese noodle stalls if you are desperate for something other than Taiwanese food. Ride south out of town on Highway 3 about 15 km through Zhuqi until you reach the junction with 169A. Turn right and head back into Chiayi.
Day 2 is a full day of riding that assumes you leave Fenqihu early in the morning.