Folding Bikes - Two very different manufacturer's views of small wheels

I was going through the Dahon website and found the following description of their HammerHead's small wheels:

"Small wheels are slightly higher in rolling resistance, but they are also inherently lighter, faster to accelerate, and most importantly, more aerodynamically efficient. Compared to the fastest 700c race bikes, the Hammerhead gives up a bit of speed but oh my, is this bike ever easy to transport."

But the whole premise of Alex Moulton's research is that high pressure small wheel offer less rolling resistance and are more efficient. Not to mention less inertia and less wind resistance.

So, given these two very contradictory positions made by prominent small-wheel bike manufacturers, what's a poor layman folding bike fan supposed to believe?

Discuss....

...positions made by prominent small-wheel bike manufacturers, what's a poor layman folding bike fan supposed to believe?

not either one of them, because they lack objectivity.

I'd want to see data, not opinions. And not theoretical data on wheels, but actual data from complete bikes.

But I'm too lazy to look it up, so I'll go with my opinion that small wheels are bad (including the one one front of my V-Rex).

Tony Hadland's book the Moulton Bicycle includes the comparative testing of full sized wheels and small 16 inch ones using identical pressure and tire type. These lengthy tests led to the Moulton view of small wheels listed in their Q&A section quoted below:

1. Why the small wheels? The small wheels are an essential feature of the Moulton concept. They offer many advantages.
With only half the rotating mass of the wheels on a 'conventional' bicycle, it is possible to accelerate faster.
They are extremely stiff and much stronger than larger wheels because of the short spokes.
The aerodynamic drag is lower; there is less frontal area and less spoke area causing turbulence to slow you down.
The centre of gravity is lowered, resulting in improved stability.
The small wheels free up space normally occupied by large wheels, allowing luggage to be carried lower. 2. Aren't smaller wheels harder to pedal?
No, because:-
The gears are chosen so that they correspond to pedalling a bicycle with large wheels.
The smaller frontal area results in less aerodynamic drag.
The lower inertia means that you can accelerate faster.
If you are still doubtful, consider the HPVs (Human Powered Vehicles) developed for the ultimate performance - many
of these use the unique 17" Moulton wheels and tyres fitted to the AM series bicycles. 3. Why the space frame?
The construction makes it far stiffer and stronger than conventional frames.
The weight is similar to that of the best conventional touring bicycles - and the Speed model is comparable with the
lightest racing frames. In conjunction with the small wheels it results in a low centre of gravity.
The standard frame size can be ridden by cyclists of almost any size.
The low top tube leads to improved safety and controllability.
The low top tube allows it to be ridden equally easily by men and women; it is also a major advantage for elderly or
disabled riders, who cannot easily ride conventional bicycles. 4. Why suspension?
It allows the advantages of the very rigid small wheels, high pressure tyres and space frame to be enjoyed while giving
a much more comfortable ride than a conventional large-wheeled bicycle. The road shocks experienced on a conventional bicycle are dramatically reduced.
It is a light, simple, maintenance free system.
Improved traction - the wheels do not bounce going through corners or on rough surfaces.
Reduced strain on the wheels - the wheels stay true, spoke nipples stay tight and spoke breakages are extremely
rare. 5. Does it fold?
No - this is a no-compromise high-performance bike, quite unlike any folding bicycle.
But ...
The frame does separate into two parts.
This does not affect the frame rigidity - tests on a brazed-up version of the frame against the normal separable version
showed no difference in rigidity. When separated into the two parts, it easily fits into the boot of a car.
When placed in the carry bag, it can be carried on a train as hand luggage, rather than needing to be placed in the
luggage van of the train - a big advantage given the restrictions on some train services. Users have also transported their AMs as normal luggage on aircraft flights. 6. Is it as good as a conventional bicycle?
It's not just as good as a conventional bicycle, it's better:-
Owners of Moulton bicycles report that after using the Moulton for a week, they never want to ride conventional
bicycles again. Just look at the specification and the performance details. 7. How well does it perform?
An AM bicycle holds the world speed record for bicycles of conventional riding position at 51mph, fully faired.
The AM bicycle has successfully completed the Race Across America (RAAM) - finishing the course of 3117 miles in
10 days 15 hours and 1 minute. Owners of AM bicycles use them successfully for commuting, touring the world and for racing. The APB bicycles are
ideal for commuting, touring and use off-road.
My own real world experience over 20 years of owning several F frame Moultons, an ATB and a Mark 3 seems to confirm at least equal rolling resistance. I do also confess to riding and owning full size bicycles-a touring bike and a mountain and road tandem.

I was going through the Dahon website and found the following description of their HammerHead's small wheels:

"Small wheels are slightly higher in rolling resistance, but they are also inherently lighter, faster to accelerate, and most importantly, more aerodynamically efficient. Compared to the fastest 700c race bikes, the Hammerhead gives up a bit of speed but oh my, is this bike ever easy to transport."

But the whole premise of Alex Moulton's research is that high pressure small wheel offer less rolling resistance and are more efficient. Not to mention less inertia and less wind resistance.

So, given these two very contradictory positions made by prominent small-wheel bike manufacturers, what's a poor layman folding bike fan supposed to believe?

Discuss....

Two things:
1. I don't think Alex Moulton purports that small wheels have less rolling resistance. It's that small wheels are lighter and more aerodynamic, while suspension provides low rolling resistance.
2. Dahon doesn't specifically say that the Hammerhead's small wheels are what makes it slower than the fastest 700c race bike. Moultons are also slower than the fastest 700c race bikes and the fastest 700c race bikes are slower than the fastest small wheeled recumbent bikes. Aside from being visually striking, wheel diameter is a minor factor in all respects.

I think the entire concept of one bike being unequivocally faster than another is hogwash. It's a case of horses for courses and a 700c race bike will always be faster than a small wheeled bike in a UCI race because small wheels aren't UCI legal.

suspension provides low rolling resistance.

Close. Suspension lets your run narrow, high pressure tires with low rolling resistance without sacrificing comfort. You could run the same tires with no suspension, but it would be a rough ride.

Tony Hadland's book the Moulton Bicycle includes the comparative testing of full sized wheels and small 16 inch ones using identical pressure and tire type. These lengthy tests led to the Moulton view of small wheels listed in their Q&A section quoted below:


I think that all of that was born out by my experience of owning and riding the TSR30 that Sesamicrunch now owns and rides. I found that the bike did what Moulton says on the tin - I rode faster and longer than on my other folding bike, and the suspension not only made the bike more comfortable, but the road holding had to be experienced to be believed. It would literally fly over the bumps and I could pedal through the roughest of normal roads with absolute confidence at speeds I wouldn't have expected.

Sesami will no doubt say what he thinks about the arrangement. He has a much wider experience of bikes than I have, but I never felt that bike was slow.


Close. Suspension lets your run narrow, high pressure tires with low rolling resistance without sacrificing comfort. You could run the same tires with no suspension, but it would be a rough ride.

I agree completely.

Close. Suspension lets your run narrow, high pressure tires with low rolling resistance without sacrificing comfort. You could run the same tires with no suspension, but it would be a rough ride.

It's the same thing really. All rolling resistance is theoretically due to surface roughness. So it shouldn't be surprising that if a ride is too rough your tires get bounced backwards, thus, increasing rolling resistance. The only way around it (literally) is for the wheel to go up, which can be accomplished with either a larger diameter wheel or a wheel with some give. The former is heavy and has poor aerodynamics, while the latter needs to flex. Since tires have conflicting demands of traction, wear, etc, they cannot be completely optimized for low hysteresis and, thus, waste a lot of energy flexing. A dedicated suspension, however, can flex with minimal losses.

So suspension lets you achieve low rolling resistance without sacrificing weight and aerodynamics.

I have this differently: The wheel size is negligible in rolling resistance (Moulton's findings), the tyre pressure dominates. But the smaller wheel is harsher, so enter suspension to counter that.

But now, another parameter enters the equation - rolling resistance is now actually decreased due to the lessened effect of rolling over small bumps - instead of the whole bike+rider being lifted over a bump, the suspension flexes and just the wheel has to go over.

Excellent explanation Jur - and brief too.

Tires with a smaller diameter have a higher rolling resistance [than tires with a larger diameter] with the same tire pressure, because tire deformation is proportionally greater. In other words the tire is “less round”.

But the site goes on to show how rolling resistance is negligible in relation to other resistances.

Also, wider tires have less rolling resistance than narrow tires...when both are inflated to the same pressure. But narrow tires can be inflated to higher pressure.

From the Schwalbe site (http://www.schwalbe.com/gbl/en/tech_info/rollwiderstand/).

I, too, tend toward the Moulton theory (but that may just be cognitive dissonance, since I own two Moulton bikes :o). The mystery to me is why Dahon's official website would concede that small tires are intrinsically inferior in rolling resistance? What studies have they done, I wonder? Pretty poor marketing, I'd say....and I'm a SmoothHound/Hammerhead fan!
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On a totally different topic (is it kosher to hijack your own thread? :innocent:) While I was changing over to the Capreo setup on my SmoothHound, I took a ride with the stock 55t chainring and the 9-26 Capreo cassette. I had the bike over 41mph (downhill) and was still pushing gears with the 55/9 combination and 20" wheels. It was exhilarating to say the least! I had to quit at 41mph because of road conditions, but there was still room to go on the gearing! Crazy fast. Now I have a very happy setup with 53/39 in the front.

not either one of them, because they lack objectivity.

I'd want to see data, not opinions. And not theoretical data on wheels, but actual data from complete bikes.

But I'm too lazy to look it up, so I'll go with my opinion that small wheels are bad (including the one one front of my V-Rex).
and that's why a Rocket is faster :D

The mystery to me is why Dahon's official website would concede that small tires are intrinsically inferior in rolling resistance? What studies have they done, I wonder? Pretty poor marketing, I'd say....and I'm a SmoothHound/Hammerhead fan!
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The Schwalbe site explains such an assertion: given the same inflation pressure, a tire of a specified diameter will be less out-of-round than a tire whose diameter is smaller. The absolute "squish" or deformation area is the same for both tires, but the tire with the larger diameter, and thus having the greater circumference, has proportionally less deformation, i.e. is less out-of-round than the smaller. The more out of round, the greater the resistance. The larger the circumference, the more gradual the ascending arc of the tire; the smaller the circumference, the more abrupt the arc. To state the thing in extreme terms, if you had to fashion a wheel made out of wood in a polygonal shape, would you rather ride a small pentagon or a larger duodecahedron?

Let's say the rims are the same width, and that we have two wheels, one 700mm Ø and the other 305mm Ø. We will ignore the tire wall height for the sake of simplicity. The circumference (Π * Ø) of the larger is 700 * 3.14 = 2200 (roughly) and the circumference of the smaller is 305 * 3.14 = 958. If there's a 25mm deformation along the tire surface, on the larger that is 25/2200 (.011) and on the smaller it is 25/958 (0.2), about double.

Regards
T
P.S. But again, as was mentioned on the Schwalbe site and by others earlier in the thread, at higher speeds, air resistance is far more important than rolling resistance, and smaller narrower tires offer less air resistance, so what little the small wheel loses in rolling resistance it more than makes up for in large reductions in air resistance -- if it's a narrow tire.

P.P.S. But none of these nuances makes any meaningful difference unless you're racing.

The Schwalbe site explains such an assertion: given the same inflation pressure, a tire of a specified diameter will be less out-of-round than a tire whose diameter is smaller. The absolute "squish" or deformation area is the same for both tires, but the tire with the larger diameter, and thus having the greater circumference, has proportionally less deformation, i.e. is less out-of-round than the smaller. The more out of round, the greater the resistance. The larger the circumference, the more gradual the ascending arc of the tire; the smaller the circumference, the more abrupt the arc. To state the thing in extreme terms, if you had to fashion a wheel made out of wood in a polygonal shape, would you rather ride a small pentagon or a larger duodecahedron?

Let's say the rims are the same width, and that we have two wheels, one 700mm Ø and the other 305mm Ø. We will ignore the tire wall height for the sake of simplicity. The circumference (Π * Ø) of the larger is 700 * 3.14 = 2200 (roughly) and the circumference of the smaller is 305 * 3.14 = 958. If there's a 25mm deformation along the tire surface, on the larger that is 25/2200 (.011) and on the smaller it is 25/958 (0.2), about double.

Regards
T
But Moulton proved through more than 500 test cycles with actual bikes that his 16" wheels rolled better. I'd take that empirical evidence over some theoretical calculation of deformity.

Has winter come early??? It's too early for the fear and self-loathing threads.

I still need to see this mythical TSR and challenge it to a race.

Sir, the gauntlet has been thrown.

Has winter come early??? It's too early for the fear and self-loathing threads.

I still need to see this mythical TSR and challenge it to a race.

Sir, the gauntlet has been thrown.Or, I'll see your TSR and raise you a Swift. :D

Or, I'll see your TSR and raise you a Swift. :D

I have a R20 three of a kind...that beats the lot of you. ;)

Has winter come early??? It's too early for the fear and self-loathing threads.

I still need to see this mythical TSR and challenge it to a race.

Sir, the gauntlet has been thrown.

But would you be testing the bike or the man who was riding it?

But Moulton proved through more than 500 test cycles with actual bikes that his 16" wheels rolled better. I'd take that empirical evidence over some theoretical calculation of deformity.

Could you provide a citation/link? I am under the impression that what Moulton showed is that smaller-diameter wheels with narrow high-psi tires have less air resistance, not that they have less rolling resistance. Predications involving two variables may lead to some confusion: larger wheels with low-pressure tires have more rolling resistance than smaller wheels with high-pressure tires. But if the tires are inflated to the same pressure, the larger wheel wins but only with respect to rolling resistance. The small wheel wins with respect to air resistance.

If you'll consult the Schwalbe site, you'll see from their graph (http://www.schwalbe.com/gbl/script/allgemein/file/showImage.php5?dateiID=2187) that rolling resistance is by far the least important of the various resistances: air, gradient, and rolling. [Not much friction resistance in a properly maintained bike.] The smaller wheel's aerodynamic benefits at speeds above 20 km/h are far more significant to overall performance at speed than the slowing effect of its greater rolling resistance, vis-a-vis a larger wheel with tires inflated to the same pressure. Below 20km/h, air resistance and rolling resistance are of roughly equal importance (see where lines 1 and 3 cross).

Key to Schwalbe graph (x-axis shows speed, y-axis shows resistance):
1 Rolling resistance
2 Gradient resistance
3 Air resistance
4 Total resistance (1+2+3)

Regards
T

I have a R20 three of a kind...that beats the lot of you. ;)
How about a Mini, R20, Yeah, Birdy and Swift full-garage? :D

Has winter come early??? It's too early for the fear and self-loathing threads.

I still need to see this mythical TSR and challenge it to a race.

Sir, the gauntlet has been thrown.

Challenge accepted! :twitchy:

Me on the TSR and you on the XtraCycle with the two kids, right?

The winner would definitively prove whether small wheels are faster or not (I think).;)

But Moulton proved through more than 500 test cycles with actual bikes that his 16" wheels rolled better. I'd take that empirical evidence over some theoretical calculation of deformity.

The problem with trying to test it empirically is that the premise is false. That is, the definition of rolling resistance precludes a single configuration from having lower rolling resistance over all terrain. So if you try to interpret the results of an experiment as determining whether one size is inherently superior to another you can always conduct another experiment over different terrain which gives you a contradictory result.

You see, rolling resistance is defined by the force which pushes backwards from the road surface as a wheel rolls forwards. There are two ways for this to happen:
1. If you're rolling over a surface which suddenly turns up 90 degrees and becomes a wall then the force of rolling resistance will be whatever force necessary to stop a mass moving at your velocity as you hit the wall. Wheel size, tire material, tire pressure, etc, won't have anything to do with it.
2. If you're rolling over a perfectly flat, perfectly smooth surface then the tire and surface will both deform into little bumps (ie miniature walls) which, in turn, push back against you as you crash into them.

Rolling resistance on real surfaces will obviously be a combination of the two. A soft wheel reduces #1 and a hard wheel reduces #2. So the configuration with the lowest rolling resistance on real surfaces will depend on the smoothness of the surface and shape of its permanent bumps.

That being said, I think the key to the Moulton concept is that both a large wheel and a suspended wheel reduce both #1 and #2 and since adding a suspension is both lighter and more aerodynamic than enlarging a wheel, small suspended wheels involve fewer compromises on typical road surfaces (although one can still find scenarios/experiments for which another configuration is better).

Could you provide a citation/link? I am under the impression that what Moulton showed is that smaller-diameter wheels with narrow high-psi tires have less air resistance, not that they have less rolling resistance.

I heard that reference in a Youtube video with Dr. Moulton that was about 10 minutes long. A quick search just now didn't yield it. I'll see if I can't find it later.

Regardless of whether the claim of faster small wheels is due to lower rolling resistance or other factors, I am still mystified as to why Dahon would say that small wheels are slower in their marketing pieces....

Regardless of whether the claim of faster small wheels is due to lower rolling resistance or other factors, I am still mystified as to why Dahon would say that small wheels are slower in their marketing pieces....

Well, they also sell a number of bikes with "full size" wheels.

I heard that reference in a Youtube video with Dr. Moulton that was about 10 minutes long. A quick search just now didn't yield it. I'll see if I can't find it later.

Regardless of whether the claim of faster small wheels is due to lower rolling resistance or other factors, I am still mystified as to why Dahon would say that small wheels are slower in their marketing pieces....

Mystified because you'd expect advertising hype never to include such a comment :) ... or mystified for technical reasons? Also, they don't say it as bluntly as you do. They say the Hammerhead gives up a bit of speed to the fastest 700c racing bikes. And they make up for that with an "oh my".

Regards
T

I heard that reference in a Youtube video with Dr. Moulton that was about 10 minutes long. A quick search just now didn't yield it. I'll see if I can't find it later.

Regardless of whether the claim of faster small wheels is due to lower rolling resistance or other factors, I am still mystified as to why Dahon would say that small wheels are slower in their marketing pieces....

I think this may be the video you speak of Sesamicrunch. It is on Google Video not Youtube.

http://video.google.com/videoplay?docid=-8522870086389552343&q=moulton

Watching that was what drove me to buy the TSR and then tempt you with it.

Anyone watching will have to be grown up and ignore the atrociously boring lecturer's voice over. It looks like some Engineering Prof voiced it (very tediously) but it refers to this subject as I recall.

Could you provide a citation/link? I am under the impression that what Moulton showed is that smaller-diameter wheels with narrow high-psi tires have less air resistance, not that they have less rolling resistance. Predications involving two variables may lead to some confusion: larger wheels with low-pressure tires have more rolling resistance than smaller wheels with high-pressure tires. But if the tires are inflated to the same pressure, the larger wheel wins but only with respect to rolling resistance. The small wheel wins with respect to air resistance.

If you'll consult the Schwalbe site, you'll see from their graph (http://www.schwalbe.com/gbl/script/allgemein/file/showImage.php5?dateiID=2187) that rolling resistance is by far the least important of the various resistances: air, friction, gradient, and rolling. The smaller wheel's aerodynamic benefits at speeds above 20 km/h are far more significant to overall performance at speed than the slowing effect of its greater rolling resistance, vis-a-vis a larger wheel with tires inflated to the same pressure. Below 20km/h, air resistance and rolling resistance are of roughly equal importance (see where lines 1 and 3 cross).

Key to Schwalbe graph (x-axis shows speed, y-axis shows resistance):
1 Rolling resistance
2 Gradient resistance
3 Air resistance
4 Total resistance (1+2+3)

Regards
T

I always thought that the Schwalbe website was quite good.

One problem with saying that air resistance is most important is that for many people, they can't make their aerodynamics much better. That is, if a person is concerned about speed, chances are they have already optimized -- to some extent -- their riding position and left the panniers at home. From what I gather, past that, the biggest improvement one can make concerns rolling resistance.

I think this may be the video you speak of Sesamicrunch. It is on Google Video not Youtube.

http://video.google.com/videoplay?docid=-8522870086389552343&q=moulton


Yup, that was it. In it, Dr. Moulton clearly states that his test yielded that small, high pressure tires offered the best rolling characteristics. Then, he designed the suspension to smooth out the ride.

Thanks, EvilV. I watched the whole thing again. Interesting video.

Mystified because you'd expect advertising hype never to include such a comment :) ... or mystified for technical reasons? Also, they don't say it as bluntly as you do. They say the Hammerhead gives up a bit of speed to the fastest 700c racing bikes. And they make up for that with an "oh my".

Regards
T

I'm mystified for technical reasons. Having drunk the Moulton Kool-Aid, and knowing that he's a quintessential engineer, I trust his analysis. On the other hand, Dahon completely concedes that small tires are inferior without offering any analysis behind it.

Moulton spoke of small wheeled bikes using a couple of percent less energy. I got the feeling that he did live tests with a rider. I'm envisaging some dude riding along wearing some kind of breathing apparatus to measure his oxygen burn. It would be just about the only way to do it I think - but then; a) I'm using my imagination and not engineering expertise, and, b) I'm as far from being an engineer as being a space man,

Yup, that was it. In it, Dr. Moulton clearly states that his test yielded that small, high pressure tires offered the best rolling characteristics. Then, he designed the suspension to smooth out the ride.

Thanks, EvilV. I watched the whole thing again. Interesting video.

I just watched the video as well. At what point does he actually say that smaller wheels offered better rolling characteristics?

At 2:00 he says "the inflation pressue really dominated the rolling resistance, not the size"
He goes on to mention that smaller wheels would be bumpier, and needed suspension to smooth it out.

I just watched the video as well. At what point does he actually say that smaller wheels offered better rolling characteristics?

At 2:00 he says "the inflation pressue really dominated the rolling resistance, not the size"
He goes on to mention that smaller wheels would be bumpier, and needed suspension to smooth it out.

starting at 3:50.

I'm mystified for technical reasons. Having drunk the Moulton Kool-Aid, and knowing that he's a quintessential engineer, I trust his analysis. On the other hand, Dahon completely concedes that small tires are inferior without offering any analysis behind it.

Tire technology might have been different at the time of testing. From what I recall of the video, Moulton talks about historical tests as opposed to what is currently available. It may be the case that small thin tread and supple sidewall tires were easier to make the big ones. Things might have changed since those tests.

I'm mystified for technical reasons. Having drunk the Moulton Kool-Aid, and knowing that he's a quintessential engineer, I trust his analysis. On the other hand, Dahon completely concedes that small tires are inferior without offering any analysis behind it.

It's a beautiful bike but the Kool-Aid isn't as delicious as you remember, and I think you're conflating a couple of different factors.

Rolling resistance, air resistance, gradient resistance, and friction add up to overall resistance. Schwalbe identifies air resistance as the dominant factor in overall resistance, about 14:1 relative to rolling resistance (at speeds in excess of 20km/h).

Moulton identifies inflation-pressure and wheel size as factors that contribute to rolling resistance, and says that the wheel size is by far the less important of the two; inflation pressure "dominates".

What I think Moulton's saying in the video is this: coupled with suspension, the little Moulton wheels may do slightly better than a high-inflation-pressure 700c tire on wheels without suspension. There he's talking about the overall design, not about the wheels alone.

Regards
T

P.S. Nor is Dahon referring necessarily to the wheels alone when they say the Hammerhead would be edged out by a fast 700c racing bike.

I agree with Timo, at 3:50 he's saying that in tests his bicycle was faster than standard bikes. He's not saying that smaller wheels have lower rolling resistance. It's the combination of small wheels, high pressure and suspension that gave the bike the edge, not just the small wheels alone.

"the inflation pressue really dominated the rolling resistance, not the size"

I think I have more experience with a greater range of wheel sizes than most around here (most folks think 30% smaller than standard is small, but my 8 inch wheels are 70% smaller than standard) and have no problem believing this statement.

On smoothly paved roads the effect of wheel diameter on rolling resistance seems to be greatly exaggerated and can easily be compensated for by higher pressures. On the other hand, road imperfections seem to make high pressure tires have higher rolling resistance, so increasing pressure doesn't solve everything. Suspension can give the best of both worlds and large diameter wheels are a type of suspension. However, like itsajustme said, a dedicated suspension system is more aerodynamic than a large-wheel suspension.

I agree with Timo, at 3:50 he's saying that in tests his bicycle was faster than standard bikes. He's not saying that smaller wheels have lower rolling resistance. It's the combination

I have a hard time visually believing this (his bike tests faster than larger bike) that seeing the rider in his video bobbing around with every single pedal stroke. There's no way that this can't contribute to a significant cumulative loss of energy.

It's difficult doing an apples:apples comparison - there are not many models of high pressure tires at 16/20" in comparison to 700c.

There is no doubt that by getting out of the saddle and hammering at the pedals the TSR30 will bob up and down a bit. I suppose that this is why in the New Series £4000 bikes, they include a device to lock out the front suspension when riders feel that they need it. However, even at 56 years old, the summer before last, I was able to maintain an average speed of 19 miles an hour for two hours without feeling totally done in. That bike was pretty quick and in the hands of a stronger rider it would have gone faster.

I have a hard time visually believing this (his bike tests faster than larger bike) that seeing the rider in his video bobbing around with every single pedal stroke. There's no way that this can't contribute to a significant cumulative loss of energy.

It's difficult doing an apples:apples comparison - there are not many models of high pressure tires at 16/20" in comparison to 700c.In the Moulton flash booklet, there is more on this subject, not enough, but more nevertheless. The tests were done on dynamometers. A link to that booklet can be found in this (http://www.bikeforums.net/showthread.php?t=329697) thread.

I dont see what you guys are arguing over. The smaller wheel will be faster if everything else is the same. else ordinaries would rule the speed category. We accepted that the world was indeed not flat, we can accept this too.

I don't care anyway. THANK YOU ALL FOR THIS THREAD. This is what I want. You guys are great. Thank you for exposing me to this type of bicycle. Thank you for linking the video EvilV, that did it for me.

We fellows of the folding world still have some room for discussions around wheel sizes. No dough a 700 C wheel is bigger than a 20" wheel, not to say a 16" wheel. Undoubtedly smaller wheels can be store and carried easier and that's the main objective of a folding bicycle. If I hijack the wheel size discussion to the MTB world now there is the 29" wheel trend that is not so different from a 26" wheel. And to spice a bit more the MTB wheel size discussion and because of historical reasons the 650 B size is gaining momento in the MTB arena. AS you can see, the difference in sizes of these three wheels is minimal and riders report wonderful improvements (psychologically, no dough!) in performance as the wheel size increases. Please what are your opinions about this MTB wheel size increase and increase in off road performance, when compared with the small wheel big wheel discussion we are having here for folding bicycles.

It's difficult doing an apples:apples comparison - there are not many models of high pressure tires at 16/20" in comparison to 700c.

What about the Greenspeed study? I'm surprised no one has cited that yet:

http://www.legslarry.beerdrinkers.co.uk/tech/GS.htm

The table lists the Comet Primo in three different diameters in the 37mm width. Assuming that the tires are made of the same material, the smaller diameter tire appears to have less rolling resistance. Although this could be just off-set by the advantage of a relatively wider width for a smaller diameter.

The problem with Ian Sims' study is too small a drum was used (see bottom of that page). This was was also the case for Moulton tests (from that film clip), so the results are in doubt.

And to spice a bit more the MTB wheel size discussion and because of historical reasons the 650 B size is gaining momento in the MTB arena. AS you can see, the difference in sizes of these three wheels is minimal and riders report wonderful improvements (psychologically, no dough!) in performance as the wheel size increases. Please what are your opinions about this MTB wheel size increase and increase in off road performance, when compared with the small wheel big wheel discussion we are having here for folding bicycles.

A small wheel on a well paved road, with hard tyres may well perform slightly better than a large wheel, but if the quality of the road is rough, it will be at a disadvantage because it can not so easily roll over the bumps. For an off-road bike, the whole game is about the wheel's ability to roll over bumps, and we are talking bumps of four and five inches at times, sometimes with a vertical face. Larger wheels would obviously smooth these out for the rider and would probably roll over them with less chance of smashing the wheel. You could go at them faster and harder too without so much risk of going over the bars.

Of course, almost all folder use is on well made roads. I once ran out of decent road on a little coastal tour I was doing and came across a three mile stretch which was covered with flints about an inch and sometimes two in diameter. The sixteen inch wheeled bike was able to accommodate the surface, but slowly and painfully at about five miles an hour. An ATB would have romped across that - large soft tyres, big wheels, perfectly at home.

The problem with Ian Sims' study is too small a drum was used (see bottom of that page). This was was also the case for Moulton tests (from that film clip), so the results are in doubt.

I remember that you said this before once upon a time, but as long as the drum is large enough to replicate the same size tyre contact patch as a flat road would, what's the problem? Are you saying that Moulton's drum was smaller than that? Maybe it is, but my impression of the contact patch size is that with a high pressure tyre and a thin wheel, the length of the contact patch is maybe less than 1.5 cm. How large a drum would be needed to ensure that? Given that real world roads are less than perfectly smooth, maybe in practice the contact patch is dictated by minor irregularities in the road surface anyway. There are a couple of places I ride where there is a thin strip of perfect bitumen where utilities people have dug up pipes and then repaired the road, so I have a length of a couple of hundred yards of perfectly smooth surface. I really notice the luxurious quality and speed of that strip as I ride on and off it.

I remember that you said this before once upon a time, but as long as the drum is large enough to replicate the same size tyre contact patch as a flat road would, what's the problem?

You've asked Jur EvilV, and he may answer differently, but here's how I would critique Moulton's results...or our use of them.

Moulton's lab simulations are a real-world approximation, and the margin-of-error or margin-of-unreality in the approximation may be as great as or greater than the margin-of-victory of one bike over another. Paris-Dakar ain't Daytona. Itsajustme made a similar point earlier.

In a field-test with fewer and/or smaller bumps, the margin-of-difference may diminish, or with more and larger bumps it may increase. The bikes may even swap places on the winner's stand depending on the exigencies of the real road ... and on other factors such as design-induced rider fatigue.

So, when the differences in unmanned machine performance are only a few percentage points, I would shift the focus away from absolute measurements of maximum machine performance to ergonomic concerns. What happens to the rider's body when riding? Which design is optimal? That is, which does many different things very well, rather than one thing excellently and another poorly? I wonder why The Optimal receives so little attention? Is it because it's much harder to define a multi-faceted concept? And because the human system is harder to measure, there being so much variation from person to person?

Regards
T

P.S. I don't mean to imply that Moulton is neglecting ergonomic concerns. Just the opposite. His design emerged from ergonomic meditation.
P.P.S. Because there are so damned many efficiency weenies in the bicycle world, I have very few front-suspension choices for my Swift.

A small wheel on a well paved road, with hard tyres may well perform slightly better than a large wheel, but if the quality of the road is rough, it will be at a disadvantage because it can not so easily roll over the bumps. For an off-road bike, the whole game is about the wheel's ability to roll over bumps, and we are talking bumps of four and five inches at times, sometimes with a vertical face. Larger wheels would obviously smooth these out for the rider and would probably roll over them with less chance of smashing the wheel. You could go at them faster and harder too without so much risk of going over the bars.

Of course, almost all folder use is on well made roads. I once ran out of decent road on a little coastal tour I was doing and came across a three mile stretch which was covered with flints about an inch and sometimes two in diameter. The sixteen inch wheeled bike was able to accommodate the surface, but slowly and painfully at about five miles an hour. An ATB would have romped across that - large soft tyres, big wheels, perfectly at home.

EvilV, I completely agree with your remarks. The point in the folding bicycle is that we want a compact package to carry around, that will be as small as the wheels allow. If small wheels have other advantages over big wheels in addition to compactness, we have further gains. That's what we are discussing here. Most of the folding bicycles have 406 mm wheels or smaller. Comparing to 622 mm wheels, the jump in size from ordinary road wheels to folding bicycle wheels is quite big.
On the case of a mountain bicycle the jump from a 559 mm wheel to 622 mm is not so big and I believe that the improvements in riding quality that many riders state are too small to be noticed (hence, "psychological") and are under the influence of a good marketing strategy from the companies that sell 29" ATB.

Both Timo88 and Caotropheus are pointing out the very minor differences that some of these design differences impart to the real world equation. Since we all know that by far the biggest factor in real cycling efficiency is wind resistance at realistic speeds, we really are wringing our hands over the last percentage point of the effort we put into riding. If I was an Olympic pursuit cyclist, I might need to worry about wheels size, tyre pressure and bike weight, but I'd be an idiot and a non-medalist if I didn't pay far more attention to decreasing the wind resistance issues, like clothing, helmet fairing, shaving legs and presumably my face.

The joke is that cycling with a baggy jacket or flapping trouser legs, being an ectomorph rather than an endomorph in body type almost certainly make much more difference to the energy required to complete a journey by bicycle than any of the things we are arguing about. Also, while the weight weenies worry about an ounce here or there, some of us are riding around with twenty pounds of extra flesh upon their bodies - I know I am.

Also, while the weight weenies worry about an ounce here or there, some of us are riding around with twenty pounds of extra flesh upon their bodies - I know I am.

I know I am not...lucky little me, 52 kg ! :wtf::D

I know I am not...lucky little me, 52 kg ! :wtf::D

That's because the bar you're pressing has no weights on it.

Regards
T