It is an absolutely wonderful road to drive. E16 from Sandvika to Fagernes. There you will have an option to go via road 51 to Lom or continue E16 to Leirdal, Road 5 to Sogn and there take road 55 to Lom. Both this roads with 50's will take you over the summits and can be closed due to weather conditions. 90% they are are open but you never know. It is the same with the alps. Usually open 1st of June.
A good idea is to check the weather online via
www.yr.no It will reveal conditions around 6th of June 10 days ahead
Suggest you all to see Kjetils presentation movie all about it. It is stuffed with information.
Also have some tips shared at my blog. Use google translate to get an idea what the hell I'm writing about.
http://varadero.skye.se/norska-alperna-2012/http://varadero.skye.se/norge-2013/In the latest report there is a lot of movies but also give you information what to expect. But believe me, you have to see this with your own eyes. Roads that seems small are easy to travel through. Gravel are availble but not shown in routeplanners.
I have driven the Pyreenes but never into the Alps so I can't give an comparison. Pyreenes are 1000 meters more to climb but.. Drive on those roads are autostrada compared to Norway.
Avoid Road 7. It is also a commuting road for trucks going between the 2 largest citys in Norway. Oslo and Bergen.
(If you like skiing, 45 km south of Geiranger you have Strynefjellets sommerskicenter. Road open end of may and snow disappear mid July.
http://www.stryn.no/sommerski/forside.aspx )
You will see asphaltroads with snow 3 meters on each side driving in a tube..