Desert Pass

Visit the site http://www.environment.sa.gov.au/cgi-bin/pass.pl.....
You guessed it...bikes and cars ....its all the same....$85 ! Once there, you can make your mind up as to whether its worth it. TIp: Buy the pass from the closest outlet to your first park entry point. That way, if it rains and you call the trip it off, you don't have to watch the $85 ticking away each week. Some of the Outback roadhouses sell the DP passes and the daily passes.Love the bush - stuck in the city - help.

Sounds expensive one for each bike, be more logical to share one between three or so. Check the site Darian said, otherwise depends which way you are going call one of the local agents such as Tibooburra NPWS (North West NSW). I would go one for each vehicle so that will give them something to read while you guys have fun. If you run into a Ranger out in the Simpson the chances of them checking are pretty remote - anyway be friendly and offer to buy one on the spot and they'll probably say it's alright. But then you could find one on a bad day.
Wish I could join you on the bikes just sold mine. Use to live at Tibooburra and rode my KLR 650 Kengai all round the place, but always wanted to cross the Simpson but did not have support crews. Saw a German couple up at Cape York last Sept on a TT600 he had a 4yr old on the front and his wife had a DR350 with a 2yr old on the front - small foot pegs and all. They had done the Plenty Hwy, Gunbarrel, Gibb River Rd and Cape York - all no problems.
Have Fun ! Cheers,

Beddo Surf KZN185

Pay the money it goe's toward upkeep so we can all enjoy it , there are less places for us to go all the time.Wish i was still here / Gulf in July

Dave D. ,,Seems to be 2 thoughts on your query,, realy boils down to HOW HONEST are you willing to be ,, cardboard bike carriers, very few rangers ,VERY FEW WHO I WOULD TRUST OR SHARE A BEER WITH IN THE MIDDLE OF NOWHERE FOR THE SAKE OF $85.00.