Why we recommend 26" wheels for touring.
By Andy Blance, designer of the Thorn range of bikes, Dec 2005

There are very many different sizes of 26” wheel; there is the French 650c size (571) which was also used for British butchers’ bikes, there is the French 650B size (584), there is the traditional British roadster… 26 x one and three eighths(590) and the sportier British 26 x one and a quarter (597). At one time, during the “Golden age of cycling”, when the roads were rougher, most bikes, throughout the world, used 26” wheels.
Now, at the start of the new “Golden age of cycling” (platinum age?), as these smooth roads get busier and the traffic moves yet faster, many of us seek out alternative routes; many of these alternative routes (and some city centres!) have surfaces which are inferior to those of yesteryear, doesn’t it make sense to re-visit the 26” wheel? At Thorn cycles, we have been championing the 26” wheel (for most usages) for over a decade.
Throughout this document, whenever I am talking of a 26” wheel, I am considering only one size… the American 26” size, which began to be propelled, in 1977, from the relative obscurity of an American beach cruiser (Schwinn Excelsior with Uniroyal knobby 26 x 2.125” tyres) into what was soon to be the limelight and glitz of Mountainbiking, by the early pioneers of the sport; Joe Breeze, Tom Richey, Gary Fisher and Charlie Kelly). In the last two decades this size has become known (literally) throughout the word. The variety of different widths and tread patterns available that fit this same size rim, (and indeed, the variety of different rims available) far exceeds anything available in any other wheel size. This size has (as do all other wheel sizes) its own international designation… in this 26” size, the designation is 559.

Statement
At Thorn cycles, we believe that, carefully weighing the pros and cons, there are probable overall advantages, for most cyclists, with 26” wheels on a lightweight sports touring solo.
We are certain that there are overall advantages to 26” wheels, for all cyclists, on a general touring solo.
We know, beyond all doubt, that there are overwhelming advantages to having 26” wheels on a tandem or heavy touring solo!

We believe that there are only a few disciplines where a 700c wheel should be considered, these are: - time trialing, road racing, track racing, triathlons, cyclosportif events, specific training for the previously listed disciplines and possibly some audax riding & very fast touring.

A little about my background.
I left school and went to Art College, I soon dropped out and worked for the Scientific Civil Service for the next four years, during which time I was trained to carefully observe and analyse materials and explosives, I attended specialist courses at the Royal Military College of Science at Shrivenham, where I was taught to firstly predict outcomes and then to devise experiments to observe, verify and record the actual results.

I have worked for Robin at SJS Cycles continuously since 1988; I have always applied the methodology I learned at RMCS, to check whether ideas actually work.
Although I have owned (amongst many other cycles) a mountainbike (but not the same one!) since 1985, I first started using 26” wheels seriously (with road-going tyres) in 1993, on a lightweight tandem that I designed (and had built) for grimpeurs (grueling ultra-hilly audax events, usually over poorly surfaced mountain roads and lanes. I was Audax UK’s AAA secretary (Audax Altitude Award) at the time and I also organised many such “sporting” rides each year) Club mates of ours had crashed their runaway tandem, on a particularly wet “Exmoor grimpeur”, injuring themselves badly. The accident happened when, on an extremely steep and twisty descent, the road suddenly turned into a stream…they had been just ten minutes behind us…I decided that I wanted better brakes, which were obtained by using Mavic ceramic rims and better grip on these (frequently experienced) slippery surfaces. I already had, what may well have been, the finest tandem in the country at that time, a silver-brazed, double marathon 753 Argos, built to my exact design and running on 700 x 32c tyres. Whilst I was certain that the new machine would be safer, I was also expecting it to be slower… but, as I soon found out…it wasn’t!
I have great confidence in my bike handling ability and, being (at that time) keen club cyclists, we knew exactly, by how much, we would leave the others behind (or catch them up by) on every descent (and, as well as the solos, there were 5 tandems in our club at the time) to my surprise the new tandem (with identical hubs, riding positions and luggage to the 753) was actually quicker. This was observed over literally hundreds of descents with our club mates using their same bikes in each case…which obviously acts as a very effective control. To be absolutely clear, the 26” wheel machine, with high quality 1.5” tyres and moderate pressures (Rear 75psi front 70psi), simply “rolled away” from our club mates much more rapidly than the 700c machine had done, it not only felt safer, it was far more comfortable. In an attempt to redress the balance the 753 was fitted with tyres which measured 25mm and the pressures were increased to 130 psi rear 115psi front, the 753 became a delight to use on short sections of very smooth dry tarmac but it became far less comfortable and slower still, on the poorly surfaced lanes, which we liked to ride. (The 753 tandem saw very little use after this)
Very shortly afterwards, using a Cannondale MTB frame (and a very ugly stem), I built myself a “winter evening bike” for the club’s hilly and often slippery, Wednesday evening rides around the Quantock lanes, I was still expecting this to be slower than my 700c touring bike…but this too was not the case, the handling, particularly when climbing steep lanes, was not exactly as I would have wished however and I experimented…
The Thorn range of 26” wheeled touring bikes and tandems owes its inception to my experiences, over many tens of thousands of miles with the Bridgwater section of the CTC, on our club runs and audax rides and it owes its refinement to the work carried out by Fiona (my partner) and me, whilst pursuing our varied cycling interests.
These days I frequently commute by bike, Fiona and I regularly take recreational and social rides around our locality and we ride some Enduros and hilly audax rides, but our passion is for cycle camping…long weekends in Wales and Adventure touring…during our long, annual holidays, spent south of the equator. I would not consider using anything other than 26” wheels for any of these pursuits; I shall attempt to explain why.



At the beginning of what threatens to be a lengthy document, I’d like to list the four key factors to consider, which dictate the performance of a wheel, I can’t imagine that there will be any disagreement with these:

[1] Frictional losses
[2] Rolling resistance
[3] Aerodynamics
[4] Weight

I will then list and talk briefly about considerations which impact upon these four key factors, some are specific to individual cyclist’s physical attributes and their individual cycling preferences and choices… I call these individual considerations. I make some general recommendations about tyre size in the sub-section within the section titled “Application”.
There are another set of factors at work, which are often surrounded by cycling lore, but are nonetheless, bound by the laws of physics, these are, to a greater or lesser extent, a consequence of the choices made in individual considerations… I call these physical properties and characteristics. Sometimes the boundaries are blurred between these two sections.

Individual considerations
There are many variables to consider, when deciding upon the ideal wheel package, for each customer’s requirements.

[A] Application…type of cycle touring
[B] Conditions…road surface or condition of trails
[C] Weight and experience of rider(s)
[D] Weight of equipment carried
[E] Intensity of athletic endeavor.
[F] Comfort
[G] Reliability

Let’s look at these factors in a little more detail.

[A] Application… type of cycle touring, obviously tyres should be chosen to allow you to gain the maximum advantage for the type of cycling that interests you the most (these advantages could be performance related (including comfort), reliability related or simply advantages in value for money!) If you have multiple road based interests, you should either; change the tyres for each separate sub category or (within reason) you should use tyres that are suitable for the heaviest duty sub category you have chosen to participate in (obviously you would be seriously disadvantaged if you used alpine touring tyres for cyclosportif events) In my opinion, the sub categories of touring may be considered as follows; -



Road based applications
[i] Cyclosportif events. These are essentially like Audax rides but with much bigger fields and usually involve traveling with the minimum of kit…at close to racing speeds.
Most participants would use 700 x 23mm or, more sensibly, 700 x 25mm. A very carefully chosen 26” wheel setup could be used, especially where a bit of speed could be sacrificed in order to gain a little comfort, or in some cases, to enable a small enough frame to be produced.
[ii] Audax events. It is much easier to make a case for an ultra-lightweight 26 x 1.50” tyre set up because of the lower average speeds, the likelihood of a bit more luggage being carried and probably worse road surfaces than would be expected in a Cyclosportif event. The only available back up is usually your fellow participants, so 26” reliability begins to make more sense…especially if you know that there will be few riders behind you!
[iii] Lightweight day rides and/or sport touring. Lightweight day rides usually involve carrying some luggage (sport touring is sometimes called fast touring or credit card touring) Typically sport touring involves staying at B+B’s or hostels but some people like to rough it, in a bivvy bag, especially in conducive climates. As you are much more likely to choose your own route, you can decide whether to use (in the UK) sustrans routes, country lanes, B roads or A roads. Choose for yourself but I would never choose A roads. The extra reliability required, now makes a strong case for 26 x 1.5” (lightweight 26 x 1.75” tyres are probably a better choice if mostly sustrans routes and/or country lanes are chosen.)
[iv] General touring. This can be anything from day rides to light camping, perhaps with an evening change into casual clothes, possibly combined with some B+B’s. General touring bikes make absolutely perfect commuting bikes, which are easily capable of the weekly shop. Here we really are looking for great reliability, whilst carrying some weight…26 x 1.75 is probably the best compromise for day in day out use.
[v] Heavy touring. This is often cycle camping…with the wonderful capacity to be totally self-sufficient in terms of mobility, food and shelter, but some people like to carry lots of clothes and equipment, whilst staying in hotels at night. Others like to plan around staying in accommodation but they like to take a lightweight tent, just in case. No matter what it comprises of, more weight requires sturdier tyres and rims, 26 x 1.75” is fine for road use but, if some tracks are involved, 26 x 2.0” is probably a better choice.
[vi] Expedition touring. Expedition touring can be considered to be like heavy touring or adventure touring (see below) but, as there is an implication of great distance and time involved, it is prudent to use the strongest and most reliable wheels and tyres possible. If the trip is not only very long but it also entails long stretches of paved road and long stretches of track, it may be sensible to take two pairs of tyres…you will find it difficult (sometimes impossible) to obtain high quality tyres on your journey…so spares are desirable, given that, it makes sense to carry optimum tyres for both types of surface probably 26 x 1.75”road tyres and 26 x 2.25”expedition (or alpine touring) tyres.


Off road (or unsurfaced road) applications
[vii] Enduro Mountainbiking. These well attended events are supposed to be non competitive…there is certainly a very convivial atmosphere in the lower half of the field…I can’t vouch for the first half! Can riding Enduros be considered to be touring? If Audax rides can be considered to be touring rides, then I do think that Enduros can be considered as such…I know that I carry waterproofs, a space blanket, a warm top, tools and some emergency food. For participation in these events, certainly very few people would ride anything other than a fat 26” tyre.
[viii] Trekking. Trekking is very popular in Northern Europe; it could be described as self sufficient, gentle, low impact, mountainbiking. The bikes usually have very wide 700c tyres…these are so heavy, that they really are very hard work. Trekking rides can sometimes involve overnight stays. A properly designed and equipped “touring mountainbike” would be so much easier to ride…this would have 26 x 1.9” or 26 x 2.1” tyres and it would have the opportunity of using much higher quality and better value, suspension forks than those currently available for 700c
[ix] Adventure touring. Adventure touring can be considered as heavy cycle camping in remote areas, probably on gravel roads and tracks…it is the ultimate antidote to the 21st century’s pressures but full kit and a week or ten day’s food can weigh 40Kg or more…especially if you carry wine for dinner! Strong wheels and sturdy tyres are sensible and indeed necessary! 26 x 2.25” is an ideal size.
[x] Alpine touring. Alpine touring is cycle camping on terrain usually traversed on mountainbikes. The extra weight involved places more stress on wheels and tyres, therefore off-road tyres with thicker carcasses and proper tyre & rim interface protection (anti-chaffing strip) are desirable…and over long distances they are essential. Given the extra weight a fatter tyre, than that which would be used unladen, is an advantage…26 x 2.25” (or even 26 x 2.4”) is optimal.

As a rule of thumb, tandems are best specified with the recommended tyres and rims from the next road based sub category up i.e. a fast touring tandem would be perfectly specified with the tyres and rims recommended for general touring on a solo in the case of expedition tandems, there is no “next sub category up” so you should choose the heaviest duty wheels and tyres available.

[B] Conditions… road surface or condition of trails…the smoother the surface, the narrower and/or lighter the tyres can be…there will be fewer things to cause punctures and fewer bumps mean that there is less need to have a big air pocket for comfort…this does mean that higher pressures need to be used to avoid damage to tyre, tube or rim when you hit the inevitable pot hole.

[C] Weight and experience of rider(s)… the lighter the rider(s) the narrower and/or lighter the tyre can be, as they are subjected to fewer stresses, any impacts are bound to be smaller than they would be with heavier (or less experienced) riders.

[D] Weight of equipment carried… the more kit that is carried, the thicker the carcass and side walls need to be…anti-chaffing strips are absolutely necessary to prevent the side walls failing at the rim (due to chafing). Without such a strip, the transportation of heavy loads can cause this kind of failure to happen relatively quickly after purchase… …especially on rough surfaces.

[E] Intensity of athletic endeavor… the harder you push on the pedals, the more weight is taken through your legs and off your backside…this vastly increases comfort; the harder you push, the more endorphins you will produce and the less you will notice being uncomfortable. So, the harder you push the less need you have for the air-cushioning of fatter tyres, or to put it another way…the more gently you take your cycling, the more you will need and benefit from having (comfortable) fat tyres.

[F] Comfort… is a major consideration for all but the most hardened mile-eaters. In my own case, I know that neither my legs nor my lungs are the absolute limiting factors in determining how long I can keep cycling for, or how much I enjoy it…it is entirely down to how comfortable I am. The air in your tyres is suspension in its cheapest, simplest and most reliable form. A 700 x 25c tyre has about 12mm of active suspension travel…25mm of suspension travel and the rim is damaged (or it damages the tube and/or tyre). A 700 x 32c tyre has about 18mm of active travel (leaving 14mm in reserve) Whereas a 26 x 1.75” tyre has about 28mm of active travel (leaving 16mm in reserve)…no wonder it is so much more comfortable!

[G] Reliability… this is often most noticeable in its absence! The shorter spokes required by 26” wheels not only save weight, they are stronger. The air cushion, that provides you with comfort, dissipates huge stresses before they reach the spokes…these two factors add significantly to the reliability of the wheels. The shock absorption also means that there is a reduced likelihood of components becoming loose.


Physical properties and characteristics
OK, so far I have outlined the different individual factors that come into play when selecting wheel size and tyre size. I would now like to go on to discuss various physical properties of wheels and tyres, I hope that you will soon see that there is no such thing as a perfect tyre size, only “the best possible compromise”. The things that make a difference are:

[1] Wheel diameter
[2] Width and model of rim.
[3] Make and model of tyre
[4] Tyre width
[5] Thickness of tread cap, carcass and side walls
[6] Tread pattern
[7] Air pressure
[8] Road surface
[9] Spokes

Let’s look at these properties and see how they affect each other and your cycling.

[1] Wheel diameter… as a wheel increases in diameter, it rolls more easily over obstacles; this is a good argument for 700c wheels…but as the wheel increases in diameter it gets considerably heavier and it becomes less strong…this is a good argument for smaller wheels.

[2] Width and model of rim. All other things being equal, a wider rim is heavier than a narrow rim…the things that are “not equal” are functions of the particular model of rim. Rims can vary in thickness…the thicker the rim the heavier it is…but (if the quality of the material is the same) the stronger and more long-lasting it is. V section rims are more aerodynamic and stronger (which means that they can use fewer spokes, which further increases their aerodynamic qualities and saves some of the extra weight that their section adds…but they are heavier than flatter section rims and the rigid triangular section means that they really are noticeably far less comfortable.

[3] Make and model of tyre. Different tyres may have the same stated size…this does not guarantee that they will be the same width…even tyres with the same measured width may vary considerably in performance. Apart from the other factors listed below, some tyres are poorly made and fail quickly (at the side walls). Whilst there are certainly uses for a heavy tyre which is strong and durable, a tyre which is heavy and inherently weak is a waste of both our money and the Earth’s resources.

[4] Tyre width… the wider the tyre the more easily it rolls…yes, that’s right, in the real world of imperfect road surfaces, given the correct inflation pressure and with all other things being equal, the fatter it is, the more easily it rolls! I believe that this is the most generally misunderstood fact in cycling! A fatter tyre can deform more easily over surface irregularities…this makes its resistance to rolling lower. However the fatter the tyre, the less aerodynamic it is and the heavier it is. Also beyond doubt, is the fact that the fatter a tyre is, the more comfortable it is, especially when road surfaces deteriorate (or disappear)

[5] Thickness of tread cap, carcass and side walls. The thicker the tread cap, carcass or side walls are, the more the tyre weighs. The thicker they are the less easily the tyre rolls…especially in the case of the thickness of the side walls. The thicker the tread cap, the longer the tyre will last (as long as the sides don’t fail before you wear it out!) Thick tread caps and puncture resisting belts prevent the tyre from deforming as easily and therefore increase rolling resistance. A thick carcass can give great structural integrity but certainly increases rolling resistance. The narrower a tyre is, the more these thicknesses (or the inclusion of a puncture resisting belt) adversely affect performance.

[6] Tread pattern. The size and depth of the gaps between tread blocks (or knobbles) makes significant differences to the performance of a tyre. These differences depend upon the road surface.
On smooth surfaces there is no need for any tread pattern at all to provide grip (or to channel water to prevent aquaplaning….which can not occur on a bicycle) If any tread pattern exists, there will be a greater or lesser tendency (depending upon the width and depth of these gaps and of the density of the rubber compound) for the raised part of the tread to be displaced towards these gaps…this displacement wastes energy, this is a root cause of higher resistance to rolling.
When the gaps between tread bocks become sufficiently large the wheel can be felt rising and falling, into and out of, these gaps…this wastes significantly more energy.
On rougher surfaces (and especially on rougher greasy surfaces) small, shallow gaps between the tread blocks, do give improved grip which is a very positive benefit, which in my opinion, outweighs the slight increase in rolling resistance.
However, when soft, loose or rocky conditions are encountered your ability to obtain traction or to change (or maintain) direction, is entirely dependant upon having a sufficient depth of knobble and a sufficient gap between the knobbles, to obtain the desired maximum angle of bite (leverage against the terrain).
It becomes immediately apparent why the Schwalbe Marathon XR tyre is so well suited to mixed conditions; the small, shallow gaps between the central tread blocks give good grip on rough surfaces but do not allow much displacement of tread. The overlapping chevron pattern of the tread blocks means that the gaps can not be felt whilst riding on smooth roads and the deeper side lugs and wider gaps between them, are not normally in contact with tarmac but they give a far greater degree of control, when steering in loose surfaces, than tyres without them.
On the severely rough and loose surfaces of some gravel roads, such as the infamous “ripio” of South America, there is a need for even more pronounced side lugs, particularly on the front wheel, a tyre, such as Schwalbe’s 2.25 ”Alpen Cross” version of their Smart Sam should be considered.

[7] Air pressure. There is an optimum air pressure for each tyre…this varies with the weight of the rider and luggage and the condition of the (road) surface. On any surface a tyre will become increasingly easier to roll as the pressure increases…up to that tyre’s optimum inflation pressure for that surface. If you think that it is always the case that the more air a tyre contains the easier it is to roll, you are gravely mistaken…if you could put enough air into a tyre it would then behave exactly as a solid tyre (assuming it didn’t blow off (or collapse) the rim or puncture). When pneumatic tyres were first used, the End to End record (Land’s end to John O’ Groats) was slashed by 3 days, all other record attempts have “merely” sliced hours or minutes off the previous best time.
Yes, on a perfectly smooth surface, such as a velodrome, 200psi may be desirable but, on very rough off road conditions, 35psi may give the lowest resistance to rolling. Too low a pressure for each situation will waste energy by bouncing vertically with each pedal stroke, as well as increasing the likelihood of impact punctures. The owning of (and the using of) a pressure gauge will allow you to rapidly optimise your efficiency over any terrain.

[8] Road surface… the smoother the road, the progressively less the advantage there is in having a tyre which can be greatly deformed to accommodate large surface irregularities…thus narrower tyres (with the necessary higher pressures) become more advantageous because they are more aerodynamic and smaller, thinner, lighter tyres become more advantageous in all smooth road situations, except on flat roads at constant speed (see flywheel effect in “[4] Weight” below).

Let’s look at two extremes of surface. The smoothest surface we can ride on, is the carefully contoured, planed, sanded and polished maple surface of an Olympic quality velodrome. Track riders can measure (to a thousandth of a second) the advantages of any item of kit…I doubt if any of us are surprised to find that they use very narrow, very thin walled, very high pressure, ultra lightweight, hand made silk tubs (tubular tyres) when they are up against competition. I feel that this is well documented enough to submit as evidence that these tyres are the most efficient for their purpose.
The other extreme, that I wish to contrast, is riding off road on hard dirt tracks, soft muddy tracks or rocky cross country courses, in his thesis “Road Rolling Resistance” sports scientist Peter Nilges, was able to demonstrate, through meticulous measurements with SRM cranks (which record power input) that fatter tyres and lower pressures used less significantly less energy in these conditions…even though they weighed more!

These two extremes of surface require extremes of tyre design.
Are the roads that you ride more like velodromes, or are they more like mountainbike routes?
I’d bet that they are somewhere in between…does 26 x 1.75” seem to make more sense now?

[9] Spokes. Selecting the optimum spokes (in “touring” wheels) can save a little weight, add some strength, marginally enhance aerodynamics, slightly increase comfort or extend reliability…sometimes they can achieve several of the above advantages simultaneously…for dishless wheels (as produced by the Rohloff hub) the best balance, of all the above, is usually obtained by the use of 14/16g double butted spokes, whereas dished (derailleur) wheels are best built with thicker spokes on the RHS to enable enough tension to be applied to the LHS spokes to prevent them from becoming loose


Now I’d like to revisit the four factors which I stated, at the beginning of this document, dictated the performance of a wheel…these factors are: -

[1] Frictional losses
[2] Rolling resistance
[3] Aerodynamics
[4] Weight

Let’s look at these factors one at a time. Let’s also compare two alternative, high quality set ups for general touring…26 x 1.75” versus 700 x 32c.… In each case (to minimize differences between manufacturers) the tyre is a Panaracer Pasela, mounted to a suitable, medium weight, decent quality rim.
(We like 26 x 1.75” for general touring…the classic British touring bikes, of the 50’s, 60’s, 70’s and for most of the 80’s, were almost always fitted with 27 x 1.25”tyres, the 700 x 32c tyres, which superseded them, are almost identical in diameter and are identical in width).
Note: The above comparison of tyres threads through the following paragraphs in green print.

[1] Frictional losses… there are three sources of frictional loss that may be considered in the case of a wheel fitted with pneumatic tyres these losses are:-
[i] Losses due to friction within the hub, in the case of bicycle wheels, these can be considered to be low or very low (depending upon bearing quality) there is no discernable difference (in these losses) when the difference in diameter between 26” and 700c wheels is considered.
[ii] There are very small frictional losses between the tube and the tyre…this small amount of energy is dissipated as heat (a slight warmness!)
[iii] Some people think that there are significant frictional losses between the tyre and the road surface… but this is not the case…the only time that the frictional losses are high is when the wheel stops rotating and the tyre skids…at these times we may be very glad that the losses are significant (!!!)…this is another good safety reason to run fatter tyres. These small losses, due to friction, are again lost as heat. (The minute advantage of a narrower tyre is more than compensated for by the benefit of extra braking capability but let’s call it a “no score draw”)

[2] Rolling resistance… as speed increases there is a linear increase in rolling resistance (it increase as a straight line graph). At touring speeds, of the four listed factors, rolling resistance is the most significant factor. I hope that you will have seen that, being tourists, we do not (often) ride on perfectly smooth surfaces, therefore a fatter tyre rolls more easily than a narrow one and that a larger diameter wheel rolls more easily than a smaller one (let’s call it a draw and give 2 points each for the 26 x 1.5” and the 700 x 32c)

[3] Aerodynamics… as speed increases air resistance rises as the function of a square, which means it is insignificant at walking pace yet it rapidly becomes the limiting factor for maximum speed on a bicycle for all cyclists…that might be 15mph for an elderly tourist or 35mph for a motivated TDF rider.

The American institute of aeronautics and astronautics says that, of the total drag created by the rider and machine, the rider causes 66.6% of the drag and the machine causes 33.3%
.
In another study, Jim Martin PhD, Associate Professor at the University of Utah, has conducted many wind tunnel tests using the finest facilities available. The tests were oriented towards triathletes, but he gives data for four separate groups of cyclists; elite, well trained, trained and recreational riders…I will just quote some of his figures for recreational riders…he tested these recreational cyclists over a 10Km trial and he found that the average constant output of the group was 154W. Professor Martin thus defines a recreational cyclist, as being a cyclist who can maintain a constant output of 154W for 10Km. Professor Martin then studied the effect of riding position, he defined three different riding positions;
(i) A typical racing position gave a coefficient of drag of 8.0lbs at 30mph.
(ii) A lower position gave a Cd. of 7.0lbs at 30mph.
(iii) And an excellent position, with the back horizontal to the ground (!) gave a Cd. of 6.0lbs.
Using these three positions (with the 154W available) gave the following times for a 40Km flat time trial in still air conditions:- 76min 01sec, 72min 57sec and 69min 47sec.
When the most aerodynamic wheels obtainable were used, these times reduced to: - 74.39, 71.23 and 67.47.
It can be seen that the aero wheels produce a time saving of 1 min 22 sec when used with the typical position, this time saving rises to 2min when used with an excellent position. But, without the aero wheels, changing from the typical position to the excellent position alone gave 6min 14sec. Interestingly, when Francesco Moser set the hour record at 51.151Km in 1984, he worked at a power output of 446W; when Chris Boardman took the record in 1996 with 56.375Km his power output was 445W…Boardman probably had the “flattest” position of any professional rider.

Don’t forget, we are considering only the aerodynamics of the wheels…the difference that a sharp leading edge (the 700 x 32c tyre) at the front or a very un-aerodynamic object (the rest of the bike, bags and rider), compared to a not-quite-so-sharp leading edge (the 26 x 1.75” tyre) in front of the same bike, bags and rider is very, very small, especially at touring speeds. The 700c wheel is narrower so it does just beat the 26 x 1.75” (Therefore let’s just give the 700c 1 point…that’s 3 to 2 to the 700c)

[4] Weight. As the weight of a wheel increases it becomes more difficult to accelerate (but it also becomes easier to maintain its rotation at a constant speed…once that speed has been achieved) This flywheel effect was used by Francesco Moser to take his 1984 hour record (he used weights that slid on his spokes which reached the rim as he reached the speed necessary for the record!) Heavy wheels dull the traffic light accelerations of commuters; they make it a chore to change pace on a climb….lighter weight wheels are desirable. Our 700 x 32c Pasela shod front wheel weighs 1700g…the 26 x 1.75” Pasela shod front wheel weighs 1620g…(This is a small win for the 26”…let’s just give it 1 point…that’s 3 all…we have a draw!) Well, no actually…the 26 x 1.75” wheel is significantly stronger; it is also significantly more comfortable! As reliability and comfort are fundamental requirements of general touring bikes (well, they are for me…I feel confident in assuming that they are for you too!) then I’d say that this is a clear win for 26 x 1.75” that’s why we prefer 26” wheels for our general touring bikes!

If you were to compare a 700 x 28c Pasela and a 26 x 1.5” Hi road folding you’d get a similar result...these sizes are frequently used on our 700c Audax and 26” Raven Sport Tour and xTc fast touring machines.
You would also get a similar result contrasting 700 x 25c and 26 x 1.3” but, in this case, the 26” wheel becomes 24.5” in diameter and the ride becomes quite “choppy” especially with the higher pressures required and we therefore favor the 700 x 25c above the 26 x 1.3”.
As you increase the fatness of the 700c wheel’s tyres, the weight gain, compared to 26 x 2.25”, is considerable and for heavy touring, adventure touring, expedition and tandem usages the lack of strength (compared to a 26” wheel) is a fundamental cause of concern! In other words the 26” wheel wins, in these situations, by a knockout!
For general touring a 700 x 44c wheel and tyre set up that was as strong as and weighed the same as, a 26 x 1.75” would undoubtedly give the ultimate ride…but such a wheel (although a remote possibility) would require a quantum leap forward in material technology…which would undoubtedly be applied to 26 x 1.75” first! This size is, after all, the most readily available size on the planet and, as I hope I have demonstrated, it deserves to be!

I know I have been talking about touring and, as a result, it is just remotely possible that you may think that real speed is not possible with the 26” wheel but the current mixed Land’s End to John O’ Groats tandem record (847 miles in 2 days 3 hours 19 minutes and 23 seconds) was set on 26” MTB wheels (and straight bars too, for that matter!)…how much faster than that do you want to go?