I am 6'6 - 190lb. I have 27" Schwinn continental. It has 27" tires. Seems to be the right size for me with the seat and the bars raised. I haven't been on a bike in 30 years, never in my adulthood, so I have no reference point... im a total newbie.

The thing is, if I spring for another bike, another vintage bike would be what I purchase since I probably cant afford anything of quality new (less than 300 buck range).

I am not sure how to refine my craigslist searching for the proper size? I don't know what I am after in regards to size. Any tips?

I've got a friend who is new to cycling and is also 6'6", but about 220 lbs. He bought a new KHS, as they have models made for tall folks. They come with longer crank arms and he really likes them. I'm no expert but to me it doesn't make sense for a guy 6'6" to ride the same length cranks as me at 5'8". The KHS was not expensive as far as new bikes go. I realize this is out of your budget but just wanted to give you something to think about.

I am a big guy just like you. I love 27" frames and I ride them like they are. They are too expensive to upgrade to modern equipment. Go spend some money on new brake pads, new tires, new tubes, new cables, new handlebar tape, and clean the bike up. Ride that vintage Continental like you are the boss of the road. Get into shape and in the meantime start researching bikes and keep checking out craigslist. The most important thing is to get out and ride. You can get some riding shorts, a jersey, helmet and all the works too. Spend your money on equipment to get you out riding and get your Continental in prime working condition. You should easily be under $300 bucks to get you and the bike out on the road. That is what I would do.

is there something wrong with
or a reason why you cant ride
your Schwinn

because keeping what works sounds to me like the best solution

if you have 300 dollars burning a hole in your pocket
you can get a set of nicer 700c rims built onto your old hubs
and maybe some modern long reach dual pivot brakes

otherwise just go ride

No, there is nothing wrong... im loving it so far. I just have to gain my confidence out on the roads, I don't enjoy the cars zipping by, I already crashed over a curb and into the grass once and I cant see behind me. But yes the plan is cleaning this bike up (its already pretty decent for a 40 year old bike) and getting to and from the grocery store with it.

I just wanted to know what the largest common size was in case something cool ever popped up on the local craigslist and I didn't know how to refine my search to show just the bikes that would fit me.

If you're lucky, you'll find a beautiful custom bike on ebay that was made for some basketball player who no longer wants it. The pool of people looking is small, so you can get a good deal that way (i saw it happen a year or two ago!)

Next up, there are occasional sightings of frames from 64cm to 66cm out there but they are extremely infrequent. You would probably be OK on a frame that size if you can find one.

Or... just spiff up your existing bike and ride that one. You can still find repair parts and tires in that size, so there's no reason you can't still enjoy it.

I am 6'5 200 and I ride a 58cm and a 62cm. The geometry is very different on the new bikes in comparison to the old. If you are scouting on craigslist, look for XL frame or 60+ cm.

new bikes in xl or 60 cm maybe

but for an older bike
with a level top tube
rather than newer sloping top tube bikes
op probably needs a 64 or 66 at least
or a 23 to 25 inch mtb

I'm 6'7" and have the same issues. I have turned to CL for my searches and have found a few of them in the past couple of years. "Tall" is my go to filter for CL and eBay. I have picked up a 67cm 1989 Bianchi Sport SX, a 27" Cannondale ST400, a 68cm 1983 Specialized Sequioa, and a few others along the way. Oh, and the search can become quite addictive.

I'm 6'5". When I got my first road bike, I scouted 2nd hand and after about 6months, found my first roadie. It was okay for me, but as I rode more and learnt more I came to realise that the bike was only just too small for me. It was comfortable enough but not quite right. So over the course of 4 years or so, I scouted around for what I wanted in a replacement and saved the money to purchase a Felt F4 in their 61cm size.

So, I would recommend, because you already have a bike that is ok, why not give it a little going over to make it rideable and just ride it. Save your money and either keep an eye out for something second hand or even save up and buy new eventually.

Measure the top tube length of your existing bike from the centre of the steerer tube in line with where the top tube meets it and horizontally to the centre of the seat tube. Use that measurement to compare to your existing bike to gauge if any bikes on the market will fit you. Within 5mm or 1/4in will be good enough. Bike manufacturers have all different ways of measuring their sizes, but knowing the horizontal top tube measurement is a way of bringing them all down to the same level and easy for a seller to measure. If you can't find the geometry of a bike you're looking at on the net to check measurements, then ask the seller to measure for you. You can get way more technical than that, but it's a good starting point.

Have fun!