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Folding Bikes Discuss the unique features and issues of folding bikes. Also a great place to learn what folding bike will work best for your needs.

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Old 10-27-07, 09:04 AM   #1
ShinyBiker
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Folding bikes more efficient?

I came across this Raleigh 20 page:

http://www.rhizomes.nl/twenty.html

The author contends that folding bikes are more efficient than larger wheeled bikes. Smaller wheels are better for climbing up hills, better for accelerating, and better overall when doing speeds up to 16 mph. He didn't really cite any studies to back this up.

Wanted to know if this was your experience? I've commuted with my folder sometimes and I've felt slightly more exerted than I have with my large 700c bike. It could have been just the weather or conditions. Haven't really tested this theory out.
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Old 10-27-07, 09:14 AM   #2
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Well, the rotational moment of inertia may be smaller for a 20" wheel compared to a 27" ot 700 cm wheel.

But unless you are accelerating VERY quickly, this wouldn't be noticeable. On the same token, a larger wheel increases the "flywheel effect", and smooths out the power pulses in your pedalling.

Get closer for better drafting? Well, OK, but I don't see too many other cyclists out when I leave for work at 3:30 in the morning.

Gyroscopic effect? Not sure what this means.

Any bearing drag would have more of an effect with smaller wheels. However, it may not be measureable, but not noticeable by the rider.

Frontal area? for a 20" wheel at 1.75" wide, I have a frontal area of 35 in^2. a 27" wheel, 1" wide has a frontal area of 27 in^2. Hmmm.

With proper gearing, a 20" wheel is still very effective and comfortable. I ride my 20" wheel folder to work every day. I've taken it on 50 mile rides and it is perfectly comfortable.

I WOULD NOT ride a 20" wheel off road. I would think it takes a much smaller rut to get airborne on 20" wheels!
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Old 10-27-07, 09:29 AM   #3
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Well, for some reason I got bumped off my edit, so here's more:

Manouverability? Sure winner are 20" wheels. I'm amazed at how manouverable my folder is!

Be sure your tires are up to maximum pressure. I notice the extra drag when the tires are low much more on 20" wheels than the 26" wheels on my MTB.
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Old 10-27-07, 09:41 AM   #4
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I agree with you eubi. I think Alex Moulton claims his studies have identified small differences in efficiency that put his suspended, high pressure tyre, small wheelers ahead of all other bikes, but I don't know the figures. What I would say is that a well designed 20 inch bike is as efficient with narrow high pressure tyres and good geometry, including stretching out the rider as any bike on good paved roads. Even I can almost average 19 mph on a forty mile ride on my Pashley Moulton TSR30 and I'm almost 57 years old.

A lot of small wheelers have the rider sitting upright, some of them run softer inefficient tyres, and some have inappropriate gearing for efficient travel at speed. They may though be very comfortable, collapsible and have incredibly ingenious folds that make them VERY suitable for local, daily travel, and utility use.
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Old 10-27-07, 10:28 AM   #5
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My folder is a 1971 Phillips that has seen a few modifications like upgraded wheels and tires and a gearing reduction to allow for climbing and towing...



I am running 20 by 1.75 wheels and tires and a reduced gearing so I can't compare it to my road bikes but it does compare quite nicely with my full size 3 speeds and my mtbs and I don't feel like I am riding a lesser bike when I hop on the Twenty.

It also dial up faster than anything I ride and is extremely nimble and stable at speed... my (reduced) gearing allows for a top speed of 25 mph which is good since the riding position is very upright.

The Twenty is also tough enough to handle some off road usage and I would guess that at some point I will build another, albeit in a fixed gear road version, and would expect similar performance to my fixed gear road bikes.
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Old 10-27-07, 10:31 AM   #6
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From what I can tell, the alleged "higher efficiency" of 20" wheels, especially for folding bike designs, is pretty much a wash.

Many folding bikes have relaxed geometries and wide tires, which will balance out most of the performance advantages. This is not to mention that most folders lack either a top tube or a downtube -- and are "one size fits all" -- which will clearly impact performance.

By the way, if it was in fact proven that 20" wheels were more efficient than 700c, I think you'd see them more frequently in non-UCI events like triathlons. Oh, and the tri riders? There was a huge fad for 650c wheels a few years back, which quietly faded when the riders concluded that the slightly smaller wheel gave no advantage -- and this is for a group that is exceptionally sensitive to minute advantages.

Last but not least, 20" wheels are less comfortable than 26", 650 or 700 sized wheels, not just in terms of bumps but also the extra fatigue due to the oversteer. So in many instances, you will have to do some sort of performance compromise (usually suspension) to make it feel as comfy as 700c, and will just have to put up with extra upper body fatigue. It's not a problem with 30, 40 or even 50 mile rides, but after that it can be an issue.
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Old 10-27-07, 10:38 AM   #7
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Originally Posted by ShinyBiker View Post
I came across this Raleigh 20 page:

http://www.rhizomes.nl/twenty.html
It might interest you to know that the owner of that page posts here.
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Old 10-27-07, 11:10 AM   #8
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yes - his username is v1nce and a top fella to boot.
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Old 10-27-07, 11:18 AM   #9
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I dont worry about studies or any of that stuff,
only real life experience. On my second post to this
forum I explained how I was blown away by how the
folder accelerates and converts wattage. I beleive the
diameter and rotaional mass stuff makes them quicker.
Once a 700x23 bike gets rolling it has an advantage,
but for shooting in and out of traffic like a stealthy ninja
the folder wins hands down !
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Old 10-27-07, 11:19 AM   #10
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Originally Posted by -=Ģem in Pa=- View Post
I dont worry about studies or any of that stuff,
only real life experience. On my second post to this
forum I explained how I was blown away by how the
folder accelerates and converts wattage. I beleive the
diameter and rotaional mass stuff makes them quicker.
Once a 700x23 bike gets rolling it has an advantage,
but for shooting in and out of traffic like a stealthy ninja
the folder wins hands down !
Plus 1000 on that.
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Old 10-27-07, 11:31 AM   #11
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(...)
but for shooting in and out of traffic like a stealthy ninja
the folder wins hands down !
Add to this the amazing travelling capabilities, and I can assure you I have no desire to own big wheeled bicycles anymore.

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Old 10-27-07, 11:35 AM   #12
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My hi blown-away factor even has me
wondering if cycling hadnt progressed into the
image based phase it is in currently, how many
more people would be riding the 'funny little bikes'
over the NASCAR type superbikes that are promoted
now ? I say a whole lot more !
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Old 10-27-07, 02:31 PM   #13
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Well folders are generally a touch heavier, but there is evidence that smaller wheels are equal to or more efficient than big wheels. Virtually all world records are held by small wheeled bikes from recumbant HPVs up to upright Moultons. So, that should be evidence enough.
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Old 10-27-07, 05:53 PM   #14
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Virtually all world records are held by small wheeled bikes from recumbant HPVs up to upright Moultons.
Not under real world conditions.
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Old 10-27-07, 06:05 PM   #15
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>Folding bikes more efficient? <
Probably not but they are fun.
I was out this morn going down hill on a tight narrow rough dirt track... letting her rip... when a guy on a fully suspended MTB passed me [not another person in miles] and he did hit the bottom maybe 2 sec before me.
But then I'm 62 and he was 18,
I'm chicken and he has no fear,
He had big dirt 26"tyers and I had smooth 20" ones.
But I think I was having as much fun if not more then him
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Old 10-27-07, 07:18 PM   #16
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I suspect that wheel size has a negligible effect on efficiency either way. Just as there are proponents of 700c wheels, there are for 20" wheels.

Alex Moulton has found that wheel inflation pressure is dominant on rolling resistance. Unfortunately his tests were done on a roller about 30cm-40cm in diameter so are IMHO not a perfect representation of road conditions. But neither is Alex Moulton a fool so his results are telling at least to some extent.

Smaller wheels by virtue of pure geometry ride over bumps with a sharper profile compared to 700c wheels. Many contend this translates to a harsher ride. I think this is also BS as in general a rider is actively steering to avoid as many irregularities as possible and the size of irregularities encountered on the road are primarily absorbed by the tyres and not acutely transmitted to the rider. Added to that that road tyres are typically inflated to higher pressures than 20" tyres and so would transmit bumps harsher.

The dominant factor on efficiency after wind resistance must be drive train efficiency and tyre rolling resistance. Drive train efficiency does not care about wheels size. Tyre size must have some influence but debate continues to rage so it can't be easy to determine. Actual measurements (on too small rollers) favour smaller tyres.

Small wheels have one advantage - they are easily lighter while being stronger. This advantage is lost to some degree due to lack of rim and tyre choices.

Long bendy stalks are not good - such as seat post and steering stem riser. There you lose out if these are flexy - effort goes into bending them and it is not clear that the energy that goes into bending them ends up as forward motion. I think it mostly ends up in heating up muscles.

Comparing my own bikes, I am slowest on my new 16" Mini, about 5% faster on my 20" Raleigh 20 and another 10% faster on my 20" Swift which is indistinguishable from my 700c bike (no longer in my stable). But I am quite sure the 16" Mini is the hardest of all my bikes to pedal along, and I intend to find out why.

Last edited by jur; 10-27-07 at 07:24 PM.
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Old 10-27-07, 08:49 PM   #17
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You don't see many 16" wheels in the Tour de France, do you? I like my folder. It can turn on a dime and it's a good little piece of kit. Don't try to sell it for more than it is, though. For a similar level of exertion, I'm about 6 mph faster on my road bike. Yes there are other concerns than just tire size, but the simple fact is that tire size often dictates some of the other concerns (gearing, aerodynamics, etc.).
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Old 10-27-07, 09:33 PM   #18
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You don't see many 16" wheels in the Tour de France, do you?
When Alex Moulton's bikes began to win in races, they were eventually banned because organisers wanted to pit men, not machines against each other. A pity since to a certain extent it stifled innovation. Especially on track racing, Moultons were unbeatable.
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... but the simple fact is that tire size often dictates some of the other concerns (gearing, aerodynamics, etc.).
I don't see how tyre size dictates gearing wrt efficiency? If you kept the back cogs the same, and upsized the chainring to compensate, you probably end up with improved efficiency, due to larger cogs being more efficient.

Wrt aerodynamics, I must confess I don't see how that relates to tyre size, unless you mean it's better due to shorter spokes and therefore less spoke turbulence.
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Old 10-27-07, 10:05 PM   #19
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If you take a pendulum and swing it on the end of a string
it will take less rotations on a short string to get to a
specific rpm than on a long string. The momentum once built
though, will take less on the long string to maintain......(??)
And I have no idea where Im going with this
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Old 10-28-07, 02:43 AM   #20
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Based purely on personal observation, I like 700c bikes better for daily riding, but in traffic, nothing beats small wheels. If you weave in and out of cars etc, the agility of a small wheeler is awesome.
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Old 10-28-07, 08:27 AM   #21
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Long bendy stalks are not good - such as seat post and steering stem riser. There you lose out if these are flexy - effort goes into bending them and it is not clear that the energy that goes into bending them ends up as forward motion. I think it mostly ends up in heating up muscles.
True story, jur. I ride my folder much more gently that I would ride my MTB. On my folder, I can feel a lot of flex in the frame, seatpost and stem. For full disclosure, I am at the top of the weight limit recommended for my folder!

So, I have modified my pedalling slightly to depend more on power from my legs than honking on the handlebars.

Most of my riding is uphill (it figures). Depending on the handlbars as a solid base for your power stroke is probably not the best idea for your folder.
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Old 10-28-07, 08:35 AM   #22
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Oh yeah...regarding tires...My bike came with 1.50" tires. I was amazed at how fast and smooth they rode (I had been riding my MTB with knobbies). However, I was disappointed with the 1.50"'s durability, and switched to 2.00" on the back and 1.75" on the front.

They seemed a bit harder to pedal at first, but my muscles got used to them quickly.

They are much better for the less-than-pristine roads on my commute!
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Old 10-28-07, 10:31 AM   #23
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well heck,

If only Lance Armstrong had known about these amazing folding bikes he might of had a worthwhile career.
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Old 10-28-07, 12:54 PM   #24
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True story, jur. I ride my folder much more gently that I would ride my MTB. On my folder, I can feel a lot of flex in the frame, seatpost and stem. For full disclosure, I am at the top of the weight limit recommended for my folder!

So, I have modified my pedalling slightly to depend more on power from my legs than honking on the handlebars.

Most of my riding is uphill (it figures). Depending on the handlbars as a solid base for your power stroke is probably not the best idea for your folder.

These are probably issues relating to the design of your particular make though. Some are well known to have very flexible handlbar posts.


On the general question, my Pashley Moulton is a few miles an hour faster than my Merc. I reckon the average speed of the Moulton is about 20 - 25% faster. The pashley has 406 wheels, the Merc 349. I don't think the issue is the wheels though. The whole geometry is different, the Moulton is much more stretched out, has a different gearing system and a much wider range of ratios to choose from. All of these contribute to a more efficient ride and for a longer trip, or one where speed is an issue, the Moulton is the business. On the other hand though, the Merc is a little beauty, and even though I haven't had the Moulton more than about six weeks, I've already stopped riding it around on errands. the Merc is the business for that. On a longer faster ride, I get the rather pretty Moulton out.

The compromises forced on designers in pursuit of a tight fold can probably account for 95% of the performance loss in a folder - not the wheels.

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Old 10-28-07, 01:04 PM   #25
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Oh yeah...regarding tires...My bike came with 1.50" tires. I was amazed at how fast and smooth they rode (I had been riding my MTB with knobbies). However, I was disappointed with the 1.50"'s durability, and switched to 2.00" on the back and 1.75" on the front.

They seemed a bit harder to pedal at first, but my muscles got used to them quickly.

They are much better for the less-than-pristine roads on my commute!
Moulton has shown how very high pressure tyres make for much lower rolling resistance and more efficient riding. Of course, with small wheels this can be incredibly harsh on the rider, which was why he developed the suspension systems which are probably the key feature of all his bike designs. You can ride rock hard, very efficient tyres in comfort even with small wheels as long as you have decent lightweight suspension systems.

On the MTB thing, I have a nice Scott Aspen mountain bike, but its tyres make it a far less efficient ride than either of my small wheeled bikes. It really is like riding a tank in comparison. You can feel the loss of power as the fat soft tyres soak up the watts. I once put some high pressure slightly fat road tyres on an MTB - it transformed it for road riding - turned it into a rocket by comparison, but the gearing was too low obviously for fast road work.

Tyres and bike geometry are key issues for efficiency.

Last edited by EvilV; 10-28-07 at 01:13 PM.
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