I walked Ben Chonzie from Invergeldie in 1996 when I was bagging Munros. From what I can remember it should be rideable for most of if not all the way up. There is a track that goes up to the plateau area at 800m then I think it's short grass to the summit. The contours look good. Think I will put this on my biking to-do list.

As for the rest of the area, have a look at the map. There's tracks going off in all directions. Might be worth a weekend visit.

I was there yesterday and I can tell you that there's no way on God's green earth is anyone riding this all the way up. Sure, a lot of it is rideable lower down but by the time you're about half way up the gradient and the rocks on the trail are such that even a world champion couldn't ride it. Then when you strike off the path onto the grass it gets even steeper and at some parts you're having to shoulder the bike. Don't get me wrong though it may be a dull munro for walkers but on the bike after a slog to the summit, it is totally ballistic on the way down. I took the hard tail yesterday after breaking the mech hanger on my full bouncer at Tress at the weekend ... and I still had a blast. That said though I'd have prefered to have had suspension both ends. All in all though a good if short ride. If you've got a bit more time park the car at Comrie and cycle up from there. Adds another 12k (there and back) of B-class tarmac.   

Off the top of my head - there's a looping landrover track on the NE side of Loch Turret where you can get upto Auchanfree Hill. From there there is probably a path of some description upto Chonzie. Vaguely remember reading about it as a possible way of getting upto Chonzie.

Other routes around that neck of the woods - don't have my maps to hand, but there a couple from Callandar heading up along the Glen beside Ben Vorlich and coming out at Loch Earn. 

Proper scottish route though - ie some pushing, a lot of swearing but utimatley far superior to any 7 stane pansying around ....

The big expanse between Loch Tay and Loch Turret has a lot of landrover tracks, which could be linked into some epics as well.  Certainly looks doable on the OS (although that's not also necesarily true ....)

If you put the names of some glens into the search facility here, there is a lot of good Scottish route advice.

Let us know how you get on for future ref!