For anyone looking for some 630/27" rims can find current production rims from Velocity. They make their Velocity Synergy and Velocity Aero rims in 630 in a variety of drills. The Aero is available in 32h, 36h, and 40h while the Synergy is available with 32h, 40h, and 48h. The Velocity Dyad is currently out-of-stock for 630/27" but I've heard another production run is being contemplated.

However, most of us don't have any skin in the game of whether the current distribution channel offers a stockists dream of 630/27" rim offerings. The reality is that high quality rims are always available on eBay or via swaps.

You can always find quality Mavic, Weinmann, Ridiga, Exal, Velocity, even sometimes Campagnolo rims in the 630 size, and often NOS. Most of us don't need thousands of rims, just several. There are always high quality tires available.

I've never understood the point of converting to 700c. The bike rides less smooth with the marginally smaller BSD and the frame wasn't built for that wheel size. In terms of giving a smooth ride, 630 will always offer a smoother ride than 622/700c for a given rim/spoke tire model/pressure set-up, when all things are equal. Is not a HUGE difference but its noticeable. Think the difference between a 559/26" mountain bike setup and a 622/29er setup, only on a smaller scale.

If you're building up new ones, might as well go 700c (if brakes will reach, as may others have commented). I wouldn't rebuild to 27" unless you want to keep "original" and you're afraid you'd get booted out of the Original Owners of Vintage Dawes Galaxy Club.

Others have touched on the reason for going from 700c to 650b, typically you have room for much fatter tires + fenders. And that almost always necessitates a brake change.

If you're thinking about getting new hubs, I'd suggest you have the frame spread to 130mm by someone who knows what they're doing. That gives you more and possibly better choices for gearing.

Since the OP is planning on getting new wheels/rims anyway, I see no compelling reason not to switch over to the more popular 700c size. Doing so makes for much better tire availability and the chances for good tire sale prices are greatly improved. In addition there's a bit more frame clearance so you have the option of both narrower tires that are available in 700c and running wider tires than would fit the frame if you stay with 27". That also gives you the option of fitting fenders with a greater range of tire widths. So there are some significant advantages to switching and I can't see a real downside unless possibly if the current frame has a really low bottom bracket and is subject to pedal strike issues when cornering - seems unlikely for the OP's frame.

Again, I'd like to have room for fenders. I'd like to have the ability to be able to ride 35s, 38s or 40s. Sure there's room for a 27 x 1 3/8" tire in there- but when a fender is in there- there's not room- I've got one bike that a 1 1/4" tire fits well with fenders.

As much as people tout the lack of availability of 27" tires- for the most part- people are going to gravitate towards the 28-35 wide tires- all achievable through 1 1/8" - 1 3/8" tires that are available. However, there's not anything that I know of beyond that 1 3/8" tire.

As far as quality of the ride- a few years ago I switched that bike from 700C to 27" and there was a remarkable improvement of the ride of the bike. I thought the difference was in the wheel size, however the overwhelming consensus (to the point of ridicule) here was that it had nothing to do with wheel size.

https://www.bikeforums.net/classic-vi...-4mm-make.html

*shrug*

Something made a difference- it wasn't just the tires.

I do appreciate strong opinions, I put forward quite a few of my own.

Maybe too many parts of the discussion ran by me here though, as I don't recall ever seeing a Campagnolo-branded rim offered in a 630BSD size.

I have long been a proponent of keeping the 27" route viable, and have even horded singles of some of the lauded and/or rare 27" rims in my efforts to match up and build great wheelsets.

I do find it to be overall cheaper and easier to find the tires I am looking for in the 700c size, such as the racing-team leftovers I sometimes buy by the box full. And so many great tires like Continental "4-Seasons" aren't offered in 27" and never were, so my customers end up selecting a 700c rim size for the wheels I might build for them.

I've noticed an increase in braking leverage using canti brakes when switching to the 4mm smaller hoops, but brake pad-dive also increases unless a wider rim is chosen, which is my preference.

The selection of 27" rims is also scant compared to the vast 700c assortment that is commonly available, especially H+SON TB14 rims which are good, good-looking and reasonably priced.

But with handbuilt wheels taking up a smaller and smaller market share, I'll not dismiss 27" wheel builds since they are a piece of the pie.

I do wish there were race-quality 1-1/8" tires available and I don't mean stiff-rolling tires like Zaffiros, which are a quite-decent tire.

I have some 1" Paselas (I bought a large quantity on closeout) that I have yet to install and try, but looking closely at them the casing looks to be of only modest quality.

With wide rims, I like a tire that measures about 26mm inflated, which most 1-1/8" tires (and 1" Paselas) do.
I am rocking on 27mm (actual, inflated) 27x1-1/4" Armadillo tires this month, which ride smooth at 60psi but which feel quite sluggish to me.

The rim size made a 0.013% difference. If you noticed a greater than 0.013% difference (which is perfectly possible), then that something (to which you refer) was something else, whether tail wind, smooth road surface, a good meal the night before, I dunno what. Oh, yes, and the tires.

Tell us how you really feel about it.

The OP asked about changing his bike from 27" to 700c. He got some good answers about the technical pros and cons. He got some good answers about the need for it now vs. desire vs. future considerations, all pertinent to the decision but not necessarily technical in nature. What the industry does or has done and what most cyclists do really don't count for much other than change the availability of tires.

Two 27" bikes have passed through my hands in the past couple years. I converted a Trek 520 to 700c for tire choice, including wider tires and studded tires for winter. Dumping the Helicomatic hubs was a bonus.

The other bike is a Motobecane Grand Prix mixte for my lovely wife. It will just be used around town. Never in the winter. Almost never when wet (only when caught out). A 27" set of Paselas was just what the doctor ordered.

Adaptive reuse - 700c is a good choice.

Restoration- keep those 27's

I have both and enjoy both, each for its own reason. But if I had only one bike, I'd run 700's for tire choice alone.

There is another difference. Steering will be quicker as the trail will have been reduced (assuming the same width tires). Also the tire/rim combo will be lighter with lower rolling inertia with the smaller diameter. But, both of these can be negated by increasing the tire size to beyond what can be done with 27". Any bike has limits to tire size. Fork, seatpost and brake bridge (unless fork/chainstay width limits the tire width). Going to a smaller wheel means a fatter tire can be fitted, offering the same "smoothness" based on tire outside diameter plus more "cush" based on a bigger tire.

I have always liked the quickening of steering when I have gone to 700c. I usually ride those old bike with very long stems which slows steering a lot. Getting some of the quickness back via the wheels is a plus.

If we get down to the math and physics of it, 8mm out of 630mm is about 1.3% linearly, which should approximate the difference in ride quality due to road surface. And it's about 2.5%, when taken to the second power, which should approximate the difference in lateral agility and longitudinal acceleration. The foregoing is speaking for the contribution of the components at the periphery of the wheel only, i.e, rim, tube, tire, tape, and spoke nipples. Obviously, changing the wheel diameter does not affect the contribution of the rest of the bike to ride quality, lateral agility, or longitudinal acceleration, everything else being held equal. So the net contribution of an 8mm change in rim diameter must be somewhat less than 1.3% to ride quality; and somewhat less than 2.5% to lateral agility and longitudinal acceleration.
If the net mass of the rim/tube/tire combination changes significantly when comparing 630 to 622, then all bets are off.

You can really feel the difference between a 32 and 36 spoke front wheel? That's incredible!

why? why is it incredible?

yeah, i can feel the difference between a 32 spoke front wheel and a 36h. that's why i have them on two bikes. and i can easily feel the difference between a db 531 bike and hi-ten. i like the way 23c tires roll uphill. and my rear brakes also help stop the bike.

if you and mtnbke want to get your troll on, do it elsewhere.

Well, in fact, the tire is larger (as is the rim) so it does contribute to a greater mass. The larger air volume changes how the tire responds to bumps.

I've never ridden a bike with one 32 and one 36 spoke wheel, but I've got bikes with both wheels either 32 or 36. I believe I can feel the difference.

I bet you are a joy at parties.

For goodness sake, buy some new wheels. They're GREAT!

Sorry there are so many posts I didn't have time to read them all so if this has been posted just ignore me.

You say you are restoring the bike, moving to 700c makes the bike altered restored not original restored. There are still some very nice 27" tires on the market so just because it's a 27 doesn't mean you can only get cheap Shin or Kenda tires, if you want a nice rolling tire the Conti Grand Sport Race or the Conti Gatorskin if you want a bit more flat protection. There is a wide assortment of tires for 27 rims, and because of that personally I would stay with the 27's. Now having said that I did convert one bike from 27's to 700 and I couldn't tell any difference in the ride. Also most older frames using 27 rims were designed to accept the widest 27" tires made at the time which were 27 3/8 which is darn close to a 700c 34! That's a very wide tire, and that's probably what the Galaxy came with since it was considered to be a touring bike and if you're planning on using it as a touring or commuting bike than Panaracer Pasela TG or the Schwalbe Marathon would be idea, I use the 27" Pasela TG on my touring bike but I only do weekend tours for the time being.

You can also cheaply switch the tubes from a schrader to a presta by getting this: https://www.amazon.com/Wheels-Manufac.../dp/B003UWLWP2 This simply inserts into the Schrader valve hole opening and then put the rim tape back over it to hold it in place. 27" tubes are difficult to find and they're junk now so switching over to presta gets you better quality tubes.

As far as modern rims being more sturdier than older ones is simply not true. I have lots of older rims that I rarely have to true, in fact one of mine has over 30k miles on it and I doubt I had to true them more than three times and then it wasn't much, and these were light weight Torelli Master Series rims, I did have these rims built with DT Revolution spokes on the front and Competition on the rear and they are 36 spoke wheels, but none of my original 27" wheels go out of true much at all. I think the older rims are actually more sturdier! All I hear on forums about rims today is that a rim cracked, a spoke broke and taco'd the rim, this is the problem with higher tensioned spokes and too few spokes use in modern wheels.

Obviously this is all my opinion, in the end you have to do what you want to do to your bike, but there is no reason to shy away from 27" rims and tires.

In my experience, the limiting factor when going from 27" to 700c isn't width, it's height. So you've got a 27x1 1/8" tire (28mm) tire limit. Go to 700c, you can add 4mm in radius, or 8 in diameter. So now you've got a 36mm wide tire (big difference!), and the diameter is the same, so pedal strike isn't an issue.

And it's only money...

OK. On my SS there was a ton of room above the tires, and the limit was the chain stays. I think you'd likely find the same on most recreational bikes with center pulls, because they have fender clearance. On my Paramount, it's at the bridges, but the chain stays don't give you enough more to put a much bigger tire in.

Conversion? My answer would be yes...no... maybe. If you plan to tour, especially on
unimproved or questionable surfaces, The answer is a definite yes to 700s,( at least
if you travel in countries where they are readily available). 700s offer a wider selection
of tread design & quality. They may be hard to come by in many third world countries.
No if you're a serious vintage guy trying to preserve authenticity. I ride both 27s & 700s.
I'm in love with my 40 year old French steel, Rigida/Normandys. It's an aesthetic thing
I can feel when I ride.... BUT I tour on 700s because 27s are about asphalt. There are
a few 'off road 27s', but they're not really, & very poor on asphalt.(bin der)

The 27" Rigida steel rims on Normandy hubs is a favorite wide-rim wheelset of mine when I find a pair with a smooth welded joint (and so smooth braking).

With the 1-1/4" Armadillos at 60psi the ride and handling is a thing to behold, if a bit sluggish, but this setup goes offroad with confidence, even if these 1-1/4" tires measure just 27mm wide on these 25mm-wide rims.

It does seem that wider rims and softer tires are the future, which brings us full circle from the old days as mtnbke did point out earlier.

I don't expect the rim diameter change to make any more difference than the difference in size between some identically size-described tires, which can be several millimeters.
But I do think the tire selection options are hugely better with the 700c size, though I still do about a third of ALL of my riding on 27" rims, including my off-roading!

I'll be putting in another 45 miles on those exact wheels/tires in the morning, chasing the "Fast Fridays" crowd.

No the OP asked:

My thoughts on the industry and obsellesence and paradigm changes were part of those strong feelings. Just my opinions, thoughts and feelings. Worth about what you pay for them. Feel free to use the Ignore function.

I've never seen someone suggest there was such a thing as a 27" tube. If you look on most 622/700c tubes you'll see on the box that they are marked for both the 622/700c size AND the comparable 630/27" size. Tubes stretch and the 8mm variance isn't enough for their to be a difference in what tube to use. Did you intend to state that 700c/27" Schrader tubes were hard to find?

You're right. The Mavic Module 4 rims were some of the best touring rims EVER made, and Mavic certainly doesn't build rims using their special alloy alchemy that they used for the Module 4 rims anymore. Its been stated it was just too expensive. Andrew Muzi at Yellow Jersey loves to explain to people that vintage Mavic Module 4 rims were stronger than anything being offered today.

Also, I've got 630/27" Wolber rims in the garage that were actually Magnesium, believe it or not. Magnesium absorbs shock/vibration better than anything, it has the highest damping capacity of any material. Yet Magnesium is about 1/3 lighter than aluminum and half again lighter than titanium. Sadly, I think I pulled a spoke through those rims, even though Magnesium should have better fatigue resistance than aluminum.

If they are 5-speed axles (120 mm over locknut distance), I could use the wheels on my Peugeot UO-8. Are the rims in true, or are they banged up and wobbly? And what's the condition of the bearings and QRs?

Strong feelings, yes, but on the wrong subjects. However if you don't see that even after I've pointed it out this second time I won't bother to mention it a third.

Back to the original theme...I'm curious how the OP's wheels work out and what motivates his decision. As he wrote, so many options, and he implied, so many considerations.