I got a nice frame not very long ago, and it's just too big I decided to 650b it and with the variety of wheels I've found I think I'm going to go fixie, this is dropping from 27x1 1/4 wheels.. other then BB clearance can anyone tell me any inherent problems I might encounter?

Your pedals will be over 23mm lowerer and much, much more likely to strike the ground while cornering.

Your geometry will be off for the wheel size and handling will likely suffer/suck.

It will also look goofy.

The frame will still be the wrong size.

When you decide to get a frame that fits, you will be stuck with a set of wheels that are more or less usless unless you can find a 650b frame.

IMO get a frame that fits instead of trying to shoehorn into one that doesn't.

How bad is it with 700c?

How "nice" is this frame? I would get a frame that actually fits you and you don't have to mess around with smaller wheels and weird fitting to get it to work.

Seriously, sell that frame and buy one that fits you. Problem solved.

What Scrod said. There is just no way around a frame that is the wrong size.

Yep, smaller wheels won't do a thing for the more important handlebars to bottom bracket to saddle relationships.

Meh... it's rideable and the 650b is just a fascination really. I won't know just how bad of a fit it is until I get a couple more parts for it and can finish it's mockup as an 18 speed.. sounds like making it fixed and small wheels is just bad joo joo. Thanks guys.
Edit: The bike is my Super Course, just going to finish building it up and will transfer everything to a fitting raleigh frame when I get my grubby hands on it.

The Most of the time a 650b conversion doesn't actually drop the bottom bracket to much, 650b tires are usually pretty wide, so the difference in rim diameter is usually made up by tire diameter. A typical conversion from 700c tires drops the bottom bracket by a few mm. A 27 inch tire might pose a problem though, you already have a fairly hefty tire, and you have a few extra mm of rim to deal with.

It might not be a good idea, but I think you could probably get away with it.

27" = 630 mm
700c = 622 mm
650b = 584 mm

630 - 584 = 46 mm

46 mm / 2 = 23 mm = 2.3 cm

That is a pretty big difference, enough to make pedal strike a big issue as well as mess up handling.

Also, no options for brakes, bike will still be too big.

Don't forget to take tires into account, assume you are using a standard 700c 25mm tire, and you switch to a 38mm 650b tire. Neither of these tires sizes is terribly absurd, in fact, they're pretty standard. If you take the tire differences into account, the difference in tire size reduces the drop by 1.3 cm.

Even just going from a 27 1/4 tire to a 650b 38mm tire reduces the bottom bracket drop to 1.7 cm.

The brakes are still an issue, no denying that.

Basically you can think of it roughly the same as switching from a 165 to 182mm crank in terms of clearence. A lot of people have strike issues going from 165 to 170/175.

hmm still against 650bing it for now.. great info though guys!