Sorry for digging up an old thread. I'm adding a comment as a public service to people who google "steam clean bicycle" and find this thread. I posted this info elsewhere on the bike forums on a another steam-clean thread.

There is a LBS here just outside of Madison, WI that has been offering steam cleaning for bicycles for years now. Many of the anal riders I ride with (like the ones that wipe off their spokes after each ride!) take their bikes to this shop to get them cleaned and the results are incredible. The bikes look showroom new. I've never felt it was worth the $100 cost of the cleaning, I just jube up the chain and wipe it down witha rag, and leave the grime everywhere else on my bike until it starts acting funny and I'm forced to take it apart and wipe it clean everything by hand. But I wanted to share that steam cleaning is done, and I've heard of no ill effects after a few years of people having it done.

I think the confusion is around what a "steam cleaner" is. My impression is that a steam cleaner doesn't "blast" steam out like a pressure washer, it is more like the steam that comes out of your iron but more of it, it kind of "wafes" out. It is very hot and it heats the grease/oil hot enough to lower the viscosity so it can no longer hold the sand and grit, so the extra grime just drips off along with the sand and grit etc. However since no detergents are used it doesn't actually "break down" the oil which makes it must gentler than using chemicals. Plus you don't have to worry about any detergents that seeped into places they weren't supposed that will reduce the effectiveness of your new lube after cleaning. It all makes sense to me, just never felt it was worth the cost.

I don't see how water will get anywhere it doesn't already get on your bike when you ride in the rain, or even just from condensation riding on a humid day, then parking your bike in a cool garage, water condenses inside your frame etc.

Just another experience to add the all the knowledge floating around!