I think I've decided...(kind of long-ish)

[smilingcat]

+1 with Lunacycle regarding 650c/700c wheel.

[Tri Girl]

I am no slower on my 650's than I was on my 700's. I find that I have a quicker acceleration on my 650's than my "big wheels."
I do think, however, that I'm slower on my 20" folding bike wheels. Maybe it's just that my little legs are turning more revolutions so they get more tired quickly.

[TxDoc]

I am no slower on my 650's than I was on my 700's.

Yes, I do believe that - I am sure that we can reach the same speed regardless of the bike.
What I am saying is that if you change wheel size you will have to change something else (power output, gear ratio, cadence...) in order to reach the exact same speed.
If you do not change enything else, only the wheel size - well, the 650 wheel is smaller so in one revolution my guess is that it will cover less distance than the 700.
Maybe I just don't know how it works - as I said I'm not a mechanic - but if I try to just make a few calculations, simple physics says that to reach the same speed with 650's you would have to use the same power output, which on a smaller wheel means higher revolutions or different gear ratio.
Correct?
I am definitely confused
Wisdom from the mechanics/framebuilders/engineers needed please...

[lunacycles]

700c wheels have a longer circumference than 650c wheels. So, if you pedal at the exact same cadence and use the same exact gear ratio, and all other factors being equal, when you use 700c wheels you will cover a longer distance for each revolution than you would cover with 650c.

Yes, you are right. If you are in a 53x16 gear using a 700c wheel, pedaling at the same revolutions per minute, you will indeed be going a bit faster and covering a bit more ground than if you were riding that gear with a smaller diameter (e.g., 650c) wheel. However, if you are that same strong rider wanting to go the same speed using a slightly smaller diameter wheel (like 650c), you can simply just shift up a gear, say a 53x14, and you will be able to attain the same speed.

If you want to calculate gear inches, e.g., how far you are traveling per revolution of the wheel, you take the number of the teeth of the rear cog (say 13) and divide it into the number of teeth of your front chainring (say 52 teeth) and multiply it by the inch diameter of the wheel. I don't have my little metric conversion chart handy at home on a Sunday evening, but the point is, you can achieve the same speed regardless of wheel size by simply choosing a slightly bigger gear.

So, for a smaller wheeled bike, your largest gear, assuming you have the same drivetrain set up as you would on a 700c wheeld bike, will indeed be a bit smaller. If you are regularly spinning out on your 53 x 11 gear (ha ha) then, yes, your smaller wheels are "interfering with your speed." But for such phenoms/freaks of nature, this can be remedied by putting a larger gear on your bike, whether it is a bigger chainring or smaller rear cog.

If we were regularly spinning out our 53 x 11 gears on our 650c wheeled bikes, I would say, yes, the wheel diameter is affecting our speed (or, just as true, our gear choice/set up is affecting our speed). But I don't believe I have ever found a racer or all-around rider who ever is spinning out their biggest gear unless they are in an insane, suicidal mood descending a plus 10 degree descent and going for some speed record.

It just isn't an issue in real-world cycling.

Seriously: How often are you spinning out your biggest gear?

Does this make sense?

The argument for wheel resistance being higher for a smaller wheel has to do with the amount of wheel contacting the ground, the "tire patch" that makes contact with the road. It is a miniscule (MINISCULE) amount less for a smaller diameter wheel. Over really long distances this will translate into a tiny, tiny difference, speed-wise. But for 99.7 percent of us, with the riding we like to do, even at a very high level, even if we are very fit, we will never notice the difference. And, for the smaller folks, if our frame fits us better--as it is not being compromised by being stretched and contorted around giant wheels--the fact that we can attain a more efficient and balanced position with the geometries possible using a smaller wheel, this will make us much faster, and that miniscule speed difference will be beyond negligible given the benefits of achieving a better fit and weight distribution over both wheels.

[TxDoc]

Does this make sense?

Yes, thanks!
I was only looking at gear inches - but yes, the whole story does make sense

[Catrin]

Thanks for this in-depth discussion. Someone was trying to tell me that I was wrong for going for the Long Haul Trucker with the 26 inch wheels rather than the Jamis or 520 with their larger wheels. I did not know enough to have an answer for him, though I suspect that he knew that before the conversation started...

[moderncyclista]

This isn't based on science - but some bikes just feel slower. Why is this? My Aurora is lighter than my 520 and doesn't have a rack (the 520 does.) The geometry? The gearing? I can't put my finger on it. I took the Aurora out for a spin today and yeah, I'm definitely moving slower. Speed isn't my primary concern - but why don't they perform the same? What is making that difference? The 520 has lower gearing even - but I move tons faster on it. I'm not concerned about 26 inch wheels, I'm actually kind of leaning away from the LHT. I know the components are supposed to be good - but unless I can ride one in my size - then it's a no go.

[Cataboo]

It could be the tires or the hubs on your aurora. I don't know what the trek 520 has on it stock. It could be the seat tube angle, crank length something like that. It could be that you're not using the gearing as efficiently, the aurora has larger gears, so are you hanging out in bigger gears and not spinning as efficiently as you do on your 520?

I don't think you should buy a surly long haul trucker without test riding one - because I don't imagine that it's going to be faster than the aurora.

I haven't really ridden an aurora much - I test rode Zen's around a parking lot once, and it seemed like a really nice ride. But I can't say that it felt slower than my surly pacer.

[MartianDestiny]

Do they both have the same tire on them? If not switch the tires and see what happens.

Geo plays a part, any weight difference in the wheelsets might (rotating weight is what you feel more than overall bike weight), a difference in your position (if you aren't at optimal efficiency and are closer on one bike than the other you may be noticing a power difference), some would claim build type (some bikes are built "stiff" and take all that power to your back tire and some are built softer which can be more comfortable but may loose you power from pedals to wheel in flex).

Lots of science crap goes into that unfortunately. Pinning down exactly why would be difficult.

[moderncyclista]

Well. I've got alot to think about and possibly research - but I'm giving the Aurora six months - I want to get some more use out of it. Catriona: Yeah, I think I mash gears on the Aurora but spin on the 520 now that I think about it. Also, yeah I think it would be slow and steady on the LHT (which it is built for.) I've just had some say it's the "bike to get." I like to find what fits. MartianDestiny: They don't have the same tires. The 520 has Race Lite Hardcase 32's and the Aurora has some Vittoria (spelling is prob. bad sorry) Randonneurs 32's. I do think the Aurora flexes quite a bit. The other bike seeming stiffer. You gals have helped me peg what I do and don't like in a bike in general. It seems silly. I've been riding for years but never really thought about why I liked some bikes and disliked others. I'm going to give it some thought and do some more research. Thanks for the advice on all counts ladies. You're wonderful.