^ Sorry, the biggest difference will probably be tire pressure, then width and compound.

I ride all of my vintage Cannondale ST bikes with 630 (27") wheelsets.

My bikes are 27" frames (~68.5cm) and I think that 622 (700c) wheelsets make them look more ridiculously out of proportion than they really are. Additionally, I think all the inanity in cycling that 622 is "new" and "better" and 630 is "old" is freakin' idiotic. I ride 630 as a protest vote as much as anything. I can get any type of tire I need in 630. However, it is funny how many people try to encourage me to actually NOT have 630 bikes. The usual argument is tire availability, followed closely by it being "old." What is really funny is usually these same people have a 584 bike (650B) that they insist is "best" for touring. I try to explain that no wheelset is best for all frame sizes large and small, for whatever intended application. What might make 584 appeal to someone on a 57cm frame is not the same as 584 wheelset on a 49cm or a 68cm bike. What really cracks me up is how I'll have my half of the conversation identifying the size as 584, and they'll typically respond with 650B. Tells me what I already knew, that their investment in 584 is as much emotional in validating some sense of being an esoteric european touring size. I'm serious. Start calling it 584 and watch 'em twitch. It's funny.

There is no one "best" road tire for a Fiat 500 and a Cadillac. There is no "best" light truck tire for plain jane 2wd toyota mini truck and a Ford F350 dualie. C'mon people, stop reading Jan's blather in between reprinted images of Robeur's art. Think for yourselves.

All that being said if you think you can tell the difference between the marginal 4mm difference in radius from the 630 to the 622 you're kidding yourself. You're noticing the difference in tire construction (tpi), the crafstmanship of the wheel build, anything but you're NOT noticing any fundamental difference in how the wheels roll. You might be noticing the differences in gain ratios.

If you really want to compare, compare identical tires/tubes and wheelbuilds (have Peter White build you up a set of Phil Wood/Velocity wheels in 630 and 622 with identical spokes). You won't notice the difference. If you think you can, I'd say you're kidding yourself. Then again, maybe I'm wrong.

Long have I wondered about the gyroscopic impact of the bicycle's wheels.

I firmly believe that the wheels on a bike act as gyroscopes. And, the heavier the gyroscope, the greater the gyroscopic effect. The further the weight is away from the rotational center, the greater the gyroscopic effect. Remember, this is just a theory I have long held and I welcome the opportunity to discuss it.

Pick up a front wheel you know to be true. With no tire or tube mounted, give the wheel a good spin, hold the wheel by the axle ends and you will immediately feel the gyroscope at work. As you try to tip the wheel from side to side, while the wheel is spinning, you will feel it want to resist any form of lateral movement.

Now, install a tube and tire. Repeat the above test and, in your mind, try to compare the feel to an unclad rim. I feel a distinct difference, in the amount of resistance imparted, by the addition of the tire and tube. The wheel, with tire and tube mounted, will offer resist movement, from side to side, more than the unclad example.

Translate that phenomenon to the bicycle and think about what two gyroscopes, working together, will do to the feel of the bike. The bike will feel more stable, marginally so, to be sure, but different, none the less.

With that in mind, it seems possible that the increase in the gyroscopic impact will manifest itself as increased stability, hence making the no hands thing seem better.

A bicycle, standing still, will fall over immediately. A bicycle, rolling down a hill, sans rider, will fall over eventually.

Now keep in mind, this is just my theory and I could well be wrong. But think about it.

So, the differences between 27 and 700 wheels are many and each factor, (tire pressure, wheel diameter, rotational weight, rotational speed and other things mentioned in this thread) must be taken into account.

And Lance Armstrong has considered them all. He goes with 700c wheels every time, does he not? That might be a clue right there.

I probably should just keep my mouth shut, but I would like to hear what others have to say about my theory.

27's being a larger diameter are inherently smoother due to a slight difference in approach angle when hitting objects. Its the reason why 29'r (700c) mtb's were invented*. Granted the difference between the 700c/26" combo difference (32mm) is greater than the 700c/27" (8mm).

Yeah, right, since the 27" rim has a larger diameter than the 700c rim it will, in theory, roll over objects more smoothly. Putting a fatter tire on the 27" rim and a thinner tire on the 700c rim will increase this effect, while putting a thinner tire on 27" and the fatter tire on the 700c will decrease it. In theory.

But let's not confuse the theoretical issue with reality. In reality, if we are talking about different bikes with different geometries and different tires, it is just silliness to pick one of many minor differences --in this case a difference of under 1.5%-- and say "I can feel the difference!" I'm sure you can feel a difference, but the diameter of the rim has nothing to do with it. The frame geometry and the specifics of the tires (dimensions, thread count, pressure, &c) have a much greater effect.

I usually ride a bike with 20" wheels, and it has a much smoother ride than my bikes with larger wheels.

I would throw this out there: There is virtually NO difference between a 700 C rim (622 bead diameter, 311 radius from fork to ground) and a 27" rim (630 bead diameter, 315 radius). The difference is 1.5%. I'm pretty sure I could not detect a difference, and confident that that vast majority people, perhaps all, could not. I think the differences that people are talking about come from wider tires that are common with 27s that look like racing bikes.

Right.

Exactly.

Wait a second, isn't that just what I said, not to mention many of the previous posters?

Well, it's what I meant to say anyway.

I think this response is pretty much spot on. In regards to wheel size it's basically what Lennard Zinn stated in Zinn and the Art of Road Bike Maintenance, that in an ideal world wheel size would be proportional to frame size (ie. the size of the rider).

I know, but I felt if *I* said it, it would settle the matter once for all.



Guess not.

Hey... you want my ol' B72 yet? Just let me know.

The difference between the wheels is 8mm, that is just over 1% of the total wheel diameter, that's not likely to make much difference, but there are other factors that can make a huge difference, the first is the tire, a 25mm wide tire is only 80% of the width of a 1 1/4" wide tire (~32mm), it's likely to be at a much higher pressure as well. The actual wheel build, different rims, different spokes, different hubs, possibly low vs. high flange hubs.

I ditched the 27" wheels and don't miss them, one of the issues with 27" wheels is tires, there seem to only be 2 or 3 tires available in 27", either the cheapest you can find or the most expensive you can find,

Anybody else going to say the same thing?

There are only a few tires available for my 27" wheels, but I have yet to find a way to run any more than one kind at at time. Asuming that I run the same kind front and rear, of course. Well, I guess I could run two different tires at a time.

On the other hand, I don't change tires very often.

That's my point, I don't need to be convinced that there is no subjectively discernible difference between wheels 1% different in diameter while the same in every other physical respect. So I'm not interested in performing the controlled experiment; I'm just outlining how the experiment would have to be configured, to be meaningful. :thumb:

Ok, 8mm is only 1% of the diameter of the rim but it's also like 75% of the distance between the tire and the fender. Those little 700s just don't fill the fenders right and they end up looking kind of pansified.
And a better looking bike rides better.

Bend some 26's a bit, looks great on my 700x38's

but 700c rims look sooo much cooler

http://t2.gstatic.com/images?q=tbn:A...3HW78o6FVsE-wA

A lot of bikes that were sold in this country with 27" wheels were not designed for 27" wheels, but for 700c. Some American and British made bikes may have been designed for 27" wheels, but French and Italian made bikes were not. I wonder about Japanese bikes. I was looking at my old Bridgestone 400, and thinking about converting to 650B. It originally had 27" wheels; I put on 700cs and it barely has clearance for 700x32 tires with a fender. but looking at the chainstays, I noticed that the indentations are perfect for a 650A or 650B tire. I'm wondering if a lot of Japanese bikes weren't originally designed for smaller wheels.

I'm intrigued by Leonard Zinn's idea that bicycles and wheels should be proportional to the bike and the rider. Rivendell does that for smaller bikes, that is it puts 650Bs or 26" wheels on smaller frames.