You basically have 4 widths to choose from for 27inch tires from a 25c narrow width to 37c fat width -see options below
|27 inch size||ISO||rough metric equivalent width|
|27 x 1||630x25||25c|
|27 x 1 1/8||630x28||28c|
|27 x 1 1/4||630x32||32c|
|27 x 1 3/8||630x37||37c|
There are a bunch of companies making 27 inch tires including; Avenir, Bell, Cheng Shin, Continential, Kenda, Michelin, Panaracer, Schwable, and Vittoria to name the big ones. Just do a search on Amazon and you will see for yourself.
You can spend $8 a tire for some Cheng Shin gumwalls or $36 a tire for Continental gatorskins and every where in between.
You want a traditional gumwall, my favorite, you have choices in every size. I personally like the Kenda K35 which is a great looking tire, sturdy and a very good bang for the buck.
You like color matching the side walls or treads to your bike? your covered- check the selection from Junky Rusty Bikes
So if you want; skinny or fat, colored or black, hip or retro, road or cross, you have choices with 27 inch tires. Don't get me wrong 700c is a great size with tons of options just don't convert your old school 10 speed to a modern wheel size out of the misguided notion that there aren't many options for the old school 27 inch tires. That's just a myth.. As Always....
Based on some comments it appears some folks think that 700c tires and 27" tires are interchangeable, THEY ARE NOT, and if I have said anything here to make you think so I am sorry. To be very clear 27" tire will NOT work on a 700c rim and a 700c tire will NOT work on a 27" rim. I have tried. The diameters are too different a 27" tire has a bead seat diameter of 630 and at 700c tire is 622.
If you are in doubt about what size you currently have look at your rims which usually have a size stamped on them and look at your current tire, in addition to having a size on the sidewall, they should also have the ISO number expressed in (parentheses) as below.
This is a 27 x 1 3/8 tire and the ISO is expressed as width and diameter (BSD) so (37-630) if this were a 700 x 23c tire it would be (23-622). So step 1 - determine your rim size, step 2 - buy tires that match that rim size, Step 3 - don't let tubes confuse you, since they don't have a bead they can be used in either 700c or 27" and you will see both sizes on the box the tubes come in.
As you can see above the phrase "Get the grip" it shows sizes for 700c and 27", tubes are interchangeable, Tires are NOT. Again tires must match the rim size. I will close with repeating that 27 inch tires and 700c tires are NOT interchangeable. Thanks.