pushing remote branches

Hi

I recently started to use git, and I experienced problems with branches: on my machine I did (on an already cloned repo)

git checkout -b experiments origin/experiments

and thus my config reads

[remote "origin"]
         fetch = +refs/heads/*:refs/remotes/origin/*
         url = git://...
[branch "master"]
         remote = origin
         merge = refs/heads/master
[branch "experiments"]
         remote = origin
         merge = refs/heads/experiments

isn't this enough to be able to push the experiments branch?

I tried

git push origin experiments

It tells me that it is a read-only url...

after adding

[remote "experiments"]
         url = git@...
         fetch = 
+refs/heads/experiments:refs/remotes/experiments/experiments

I can now push that branch with

git push experiments experiments

but I was wondering whether the initial config wasn't enough...

many thanks in advance
	Lorenzo