Can subdomains boost the main domain?

[Grumpy_Carl]

HI

I know that having a strong domain can help when creating sub domains, but can it also work the other way round? Can having a number of strong sub domains help the top level domain's quality and history?

My reason for asking is that I have half a dozen domains which have been used for various projects, and still are, which have involved having a landing page on the root domain and running dozens of sub domains.  These subdomains, across 6 root domains, have about 500,000 pages indexed. I have now decided I should do something with the root domain so am wondering if there are any benefits I would have gained from my initial approach.

Thanks

[AlanMosley]

Yes it has in my experience, I worked on such a site, where the root domain had only a home page with 4 sections of links for each sub-domain, it ranked well for the link text of the outgoing links, with no other mentuions of the keywords.

[EGOL]

Early this year I 301 redirected all of my subdomains into folders in the root.  The results have been kickass.  Everything ranks better now because the power of the subs were united with the root and the power of the root was united with the subs.  It was like uniting the clans.

[onlinemediadirect]

In my experience I have been pleasently surprised by the performance of sub domains. I have a blog sub domain that has the same page rank 4 as the main site.

So performed really well.