Maria Island makes for a great overnight cycling trip, allowing you a chance to not only explore the more commonly visited sites on the Northern Island, but also a chance to head down to the much less visited Southern Island, and spend a wonderful night at Encampment Cove.
The route described below sets aside the first day for a leisurely exploration of the Southern end of the Island on the first day, overnight camping at Encampment Cove, and then a walk up Mt Maria and exploration of the more visited Northern end of the Island on the second day.  However, once on the Island, you can mix and match the rides to your own liking.
Maria Island has an amazing abundance of wildlife, so it can be worth taking a good torch for a bit of a night time look around.

MAPS

It is definitely worth purchasing the Maria Island National Park map and notes before going to the Island.  More relaxed (and budget conscious) explorers could get by with just downloading the Maria Island by Bike map.

WARNINGS

Maria Island has no food, and limited water availability so make sure you take everything you’ll need with you.
Check out the National Parks fact sheet for more details on the island.
The park is thought to be one of the few places in Tasmania free of Phytophthora, a disease that attacks many native plants. Phytophthora can be spread by soil from your bike, especially soil caught in wheels. So give your bike a good clean before you leave home, and then when you arrive use the washdown station located at Darlington Jetty to give it a good second going over.

ROUTE OPTIONS

Maria Island is a National Park and cycling is only allowed on designated trails – not on beaches or walking tracks.
The route described below, could be done by a fit cyclist in a single day, but if you’ve gone to the expense of getting to the Island, then do it justice and stay two or three days and enjoy it.  Three days is recommended if you wish to climb both Mt Maria and Bishop and Clerk.
The route assumes you camp at Encampment Cove, which is generally a lot quieter than Darlington, but of course an alternative option would be to camp at Darlington and just do day trips further south.
Give some thought to putting aside some time either before heading off south, or after the ride, for a look around Darlington and an exploration of the fossil cliffs as they are a highlight of the island.

GETTING THERE

Maria Island is accessed via a ferry which leaves from the township of Triabunna.
Triabunna is about 85kms (one and a half hours) North East of Hobart on the East Coast.
For more details on Ferry Fares, times and costs visit http://www.mariaislandferry.com.au/ .  They charge about $10 to take bikes, or bike hire is available through them.

ROUTE NOTES

You will land at Darlington at the Northern end of the Island, and if it’s your first time on the Island, then it’s worth having a bit of a look around at the visitors centre to get your bearings.
From Darlington head south on the gravel road towards the painted cliffs.  There’s a little bit of a climb over thea headland just as you head out of Darlington, but once over the headland, it’s downhill again towards a beautiful beach.  Follow the track along the back of the beach (ignoring the turn off inland towards Mt Maria about 2kms out of Darlington).  A few hundred metres past this turnoff, park the bike and head out and visit the painted cliffs for a look around.
After visiting the cliffs, continue south towards French’s Farm.  This is fairly easy riding all the way on a good gravel track with some lovely views.  Trust me when I say you can spoil this ride by rushing along.  You’ve got all day, so use it and enjoy.  It’s approximately 11km from Darlington to French’s Farm, the turn off is signed.
There’s an old farmhouse, lots of campsites and some tank water and toilets here, and it’s a good place to drop you camping and overnight gear to lighten your load as you continue south as you will come back here before heading to Encampment Cove.
Continuing south, you head down a short hill and across a bridge and then very quickly hit the loose sand which will be your companion for the next 4km across the Isthmus.  The trail is mainly rideable, but it is loose sand, so don’t be surprised if you end up pushing some sections.  At the far end of the Isthmus you can head down to one or both of the beaches and have a bit of a relax.
At the far end of the Isthmus, the track splits heading to Robeys Farm to the right (4.5km each way) and Haunted Bay to the left (5km each way).  It doesn’t really matter which way you go, as they are both out and back rides.
The ride out to Haunted Bay is the quieter and more pleasant of the two trails, and if you only do one of these rides, then choose this one.  The first kilometre sidles along behind the beach, but then the trail begins to climb and over the next 3.6km you will gain 200 metres in height (yep – it’s all downhill on the way back).  The last 400 metres drop back down to a spot where the track ends, still 150m above, haunted bay.  There is a signed (and steep) walking track from here that drops down into the Bay, which on a sunny day is a lovely place to explore the rocky shoreline and enjoy the views over lunch.  Return to the Isthmus the same way you came.
The ride out to Robey’s Farm is a fairly flat ride out through bushland with limited views on the way.  It ends at an old farm house which you can have a poke around before turning tail and heading back to the Isthmus.
After exploring the Southern end of the island, return across the Isthmus to French’s Farm, grab your gear and head down to Encampment Cove which is directly across from French’s Farm.  It is about 2kms to the campsite which has some superb little sites right along the shore.  You’re guaranteed to get plenty of nocturnal visitors (which can include some mozzies) but more pleasurably possums and plenty of wallabies.  There’s a small shelter here as well.
If you have enough time and energyyou can head out and explore the old convict and probation station about a kilometre to the west, or head out there the next morning.
On the second day, either retrace your steps to French’s Farm, or if you didn’t get out to have a look out at the convict site last night, you can do a bit of a loop out around there (see map above) which will drop you back put on the track towards French’s Farm.  From the farm, head back towards Darlington, looking for a turnoff on your right about 1.3km north of the farm and head off this way.  This inland route firstly winds its way through some lovely forests, but after about 4kms the track turns up, and it’s a bit of a steep climb up to the pass.  After a quick run down the other side, there’s one last small climb up to the start of the Mt Maria walking track.  You’re just over 6kms from the turnoff at this point.
The walk up to Mt Maria is about 8kms return from this point and will take 2–3 hours on foot.  The final ascent includes a bit of a scree scramble and can be very slippery, so don’t tackle this walk lightly.
From the Mt Maria trail head it’s a fun 2.5kms descent back out onto the coastal track.  You’ll emerge just behind the painted cliffs and from there you can retrace your tracks to Darlington and the ferry.
For those with the time, you can drop your stuff off and go a short circuit out to the fossil cliffs and around the greater Darlington site (see pink line on map above) or a more relaxing option would be to camp the night at Darlington and give the place the time it deserves.  The walk up Bishop and Clerk is a lovely climb with better views than Mt Maria in my opinion.