Hey all, I got my first bike which I'll attempt to convert to a fixie. It is a 70's (I think) Motobecane Super Mirage. So far I've only done a few things, new bars, tape, saddle, removed shifter/derailer. I have a few pics here: https://flickr.com/photos/tronicscribe

Anyway, I need to either use the stock rear wheel and convert it to fixie, or buy a new wheelset. My question is, if I get a new wheelset, can I fit 700c wheels on this bike? The current stock wheels are 27" so I know 700c is a little larger, and I don't know if the brake pads will line up on a 700c wheel or if it will even fit in the forks or rear dropouts. So, how does everyone seem to buy new flipflop wheelsets for their vintage conversions if all vintage bikes run 27" wheels?

Or, is there a way I can safely convert the stock hub into a fixed gear without welding? Thanks!!

easiest way to make sure everything works, is to buy a pair of hubs, and have your local shop relace the wheels with the hubs. Have any idea the spoke count of the wheels?

27" wheels are slightly larger than 700C wheels, so if you're unlucky, chances are you'll need to get long reach calipers (Tektro makes these) Other than that, everything should be good to go. You can also look for a 27 fixed rear, which is attainable.

For example.. Here

Tthe 27" sizing is no longer standard and decent tires are few and far between. If you are going to invest in a decent set of wheels, going 700c is the way to go.

Oh I thought 700c was larger than 27. I saw it here, https://www.sheldonbrown.com/tire-sizing.html#iso and was confused by what it says for 622mm and 630mm because I if 622mm is 700c then of course that is smaller than 630mm, but then the traditional sizing for 622mm says it is 28xsomething, so 28 is larger than 27.. you see why I got confused?

Anyway, so you are saying that 700c wheels will fit on a vintage bike like mine, but I might have to replace the brake calipers? If that is all, then i should just buy a new wheelset I guess. And if what ianjk says is true, about 27" tires not being easy to come by, that's another reason to get 700c.

700C is about 4mm smaller than 27 wheels. My bike is a conversion of a schwinn frame designed for 27wheels, I put 700's on them and it's fine. Unfortunately my frame is drilled for nutted brakes and my LBS only stocked the Tektro 538, which barely reached the front rim (enough to brake, though). I ended up filing about ~2mm from the fork which brought the brakepads to a more comfortable part of the machined surface of my rims and all is good.

Any reason you didn't just dremel 2mm out of the bottom of the caliper slots instead of filing down your fork?

Not really...the fork seemed more accessible (for filing).

I have the same issue; 80s Ross 12-speed. I want to convert it to single speed before winter, for all the obvious reasons.

Here are the options I came up with:
-strip off derailleurs, keep cassette/chainrings on. Well, you've already done that, so...
-convert 6-speed freewheel to single speed, and take off outer chainring. Although you hear people recommend this quite a bit online, in reality it's not a great option at all. Every bike shop I've gone to said they won't do the procedure, because it simply isn't safe or reliable (when you change a 6-speed freehweel to single speed, you have to "re-dish" the wheel, which with that drastic of a change isn't good)
-buy a new rear wheel, keep front. There are two problems here. If you buy a 27" rear singlspeed wheel, well, they don't exist. The only place I've seen them is on the same site mentioned earlier, however I wonder if they have any in stock. YOu could also replace rear 27 with 700c, but then your tire sizes will be different and your bicycle will handle differently.
-get a new wheelset, 700c, singlespeed. This is obviously the better option here, and you have quite a choice with types of rearwheels (single-sided SS, free/free, free/fixed, fixed/fixed, single-sided fixed). You can buy the wheels, or make them yourself. I've seen wheelsets as low as 100, which is fairly cheap (questionable reliability)?

Let me know what you come up with, cause like I said, I'm in the same boat!

Those are great suggestions, and the more I research and talk to other people, the more I feel I should just buy a new 700c wheelset. I still don't understand the measurments, as I mentioned in an above post:
I'd still like to know why that is. Any ideas?

Just sounds scary to me, and needlessly complicated. It's very easy to file a little bit out of the bottom of the caliper slots, and it's not really dangerous since the bottom of the slot isn't really under any stress anyways.

tire/wheel sizes are confusing- you're better off not looking at the "common" name for a size and just looking at the ISO designation. You'll notice on Sheldon's chart that 700c, some 28x sizes, and 29'er are all actually just ISO 622. Of course they're applications and available tires are different.

My conversion worked ok with brakes. The diacompe 610 that was on the front (bike was missing the rear when I got it) was able to reach a 700 in the rear. I had to buy a diacompe 750 for the front though because the 610 just barely didn't reach.

$3 in the used shop parts bin. Spent some time polishing it and it looks brand new (and even better, I painted the space the logo sticker used to be with the frame color paint).

Back in the day, the size of the tire/wheel was actually "theoretically" the diameter of the tire (not the wheel)...

Now with the ISO measurements, they are measuring the rim, not the tire...

Who the heck knows.

Well the 2mm wasn't really that much material, and the entire process consisted of removing the front wheel and filing. I'm pretty sure my bike is going to be okay, but if my fork fails and I die, I will definitely let you know.

It's not just failure but getting each side of the dropout even so that the wheel stays straight. In the rear it's not much of an issue as you take material off from the bottom of the drop.

That is confusing, lol. So how is 28" smaller than 27"? I guess if you all say 700c is in fact smaller than the old 27" wheels I'll just leave it at that.

I understand that, which is why I did it pretty carefully and did make sure that I took the same amount of material off both sides of the fork. My front wheel is aligned.