smallwheeler

this thread took a weird turn.

pinholecam

This thread seems to have taken a direction of attacking anyone who claims that a small wheel bike is slower (even when they have ridden both and often in group rides).

We can compare with some ideal 'racer' mini velo in the sky or we can compare with whats available out there bought with real budgets and real money.
If we claim every bit part as different and not ideal for comparison, then why do we even compare at all?
After all, one will be some sort of 16-20" wheel and the other 700c.


We can however say that in the context of a rather good off the shelf small wheeled bike, with reasonably good parts, its just not going to be as fast as 700c bike of about the same vein (ie.off the shelf bike, with decent parts).
Oh.... with the same decent rider too.



Many also forget that the Moulton records were in the context of its time.
Steel moultons and steel bikes and old wheel tech/types, old gearing (eg. limited choices and hard/easy?).
Whatever British rules of gentlemanly competition and all that too (Eg. no over taking if someone is ahead for example) (obviously I made that one up)

berlinonaut

It is not at all about attacking, it is just about not frivolously creating a general rule from a very limited set of correlations noticed by some people within an area of huge complexity (as correlation is not the same as causality).

In my opinion wheel size is just one of many many factors that may influence bike speed (many addtional of them with the tire alone). And all the factors together create complexity. Comparing two very different systems (bikes) by example (just two "random" bikes of the many that are possible candidates) in my eyes just does not create enough momentum for a proof of evidence fort the claim that small wheels are always and absolutely slower than bigger ones. The more as there's also proof for the opposite view. I do not know what is right - I'm just saying you do not have enough evidence for an absolute claim.

True, but you ignore the fact that 1.) small wheelers were forbidden in official races a long time ago (which has an effect on the amount of small wheelers used for racing in our days, even in not so official races as well as on the material that is available) and 2.) there are the records that were achieved on Moultons as long as 30 years ago and still have not been beaten. Should not be the case if the Moulton's success was just in the context of it's time - with modern material it should then be easy to beat them - did not happen until now. Plus if small wheelers are absolutely slower than big wheelers (due to the laws of physics) the records should not have been possible back then as the laws of physics possibly did not change much over the course of the last 30 years.


So what you are basically saying is that with equal material and equal state of development (back in the 80ties) small wheelers (in this case Moultons) were not slower than big wheelers by principle. However, as technology has evolved with the bigger wheeled bikes but not so much with small wheelers this is different today? This may be true (I don't know) but would not be an absolute law but "just" the current situation today, obviously on the first hand caused by a lack of investment an interest in small wheelers for racing purposes. We cannot say if with the same amount of investment small wheelers would have achieved the same amount of progress i.e. in weight and performance as the big wheelers or not. Exactly what I was saying.

invisiblehand

FWIW, it seems to be about the evidence by my take.

It depends on the question. Are folks asking about the effect of wheel size or a folding frame or bike fit or so on? I understood the question to be about wheel size. I assume most folks here agree that tire quality, weight, frame and fit matter holding the rider constant.

You'd expect a smaller wheel to have more rolling resistance in an all things equal comparison. But as you write, what is the correct comparison? That's what (I think) folks are debating.

desastar

That is true. Smaller wheels does require more effort. Nothing currently is as effortless as my 700c carbon roadbike. My Moulton is heavy and and it is now rideable (just) after a weight reduction program. My 9 speed Birdy is lighter and is more effortless than my BF Tikit dual drive and the slowest is my 3sp Brompton. I have pretty fast small wheeled bikes but only when comparing to other 16-20" wheels.

fietsbob

451 narrow high pressure wheel and tire ? same width and type of tire in 622 ?

you turn over a bigger gear to maintain the same speed, because the wheel circumference is smaller.

the biggest air resistance is the body of the rider. that is also the engine..


No Free Lunch..





....

smallwheeler

it only took 81 posts for someone to say the obvious - it's about gearing.

fietsbob

Yup, Gearing...

Have 2 Rohloff bikes, 16t cog on hubs ; chainring 53t on 20" 38t on 26"
gear range nearly identical on both bikes..

Rick Imby

So is your 20" er running the same quality and width tires and wheels as the road bike? My 20" er is running wider heavy cheap tires. I'm about to swap over some really light wheels and tires onto it.

badmother

Never heard anybody claim that a car with smaller wheels need a bigger engine and/or more fuel than a big wheeled car- or that it is slower becouse of the wheel size...

pinholecam

For the faster small bikes, I have a Raleigh MV, Moulton TSR, Tyrell IVE.
The Raleigh either uses Kenda Kriterium 1.25" or Schwalbe Durano (was on Panaracer Minits once too).
The Moulton has been on Continental Contact Sports as well as Durano (1.25").
The IVE, has used Kenda Kriterium, though now the Marathon Racer 1.5" lives on it

All said, the tires are not some dumpy 2" width, heavy stuff.


Lighter Wheels do make a difference (esp with good hubs); though all these are up to a point where diminishing returns start to creep in.
The stock tires that came with my Raleigh was really slow and dumpy in ride quality (some no brand China made ones).
Pick up was slow and did not roll as well.
The heaviness of the tire was apparent once I took them off and changed them.
On the hand, the tires were heavy and felt like just pure heavy rubber w/o the benefit of a good/light protection layer.


Panaracer Minits might be the one that rode the smoothest on good roads and the lightest.
But the front tire got a puncture within 2 months; and I do thing that the protection layer is thinner for the more supple tires.
Kenda Kriterium are good in most cases (being very cheap on Taobao). Not as smooth as Minits, but that difference goes away on regular roads (ie. not newly paved ones).
Durano seems more like the Kenda, and I can get them for about the same as the Kenda via Bike24, so they are becoming the standard ones I use.
Continental Sports Contact, had a seal (side wall) failure between stitching and tire; The only one I have ever had over 10yrs of riding; So I'm won't be buying any again.
Marathon Racers is a good balance of long distance ride comfort, ability to traverse tracks/gravel, puncture resistance and speed for 18" wheels.

Rick Imby

Interesting you say this as the tires on the Toyota Prius and on the earlier Honda Hybrids were much smaller than their other cars.

badmother

I used to have a small Toyota. I joked it had wheelbarrow wheels 1,3 petrol engine. Fastes (snappyest) car I ever owned. No problem "diving" into traffic with it during rush hours. My present Skoda with much bigger tyres (and a 1,4 diesel) is hard to wake up. Good enough for my use but there is no "diving" into traffic with this one.

Top speed is a different matter. No idea what new and old car can/could do for top speed. gearing and engine is what made them different.

Rick Imby

With a 700 vs 20" going the same speed in the same overall gear ratio(this is what we are trying to compare). It seems the 20" takes more energy.

The rider, frame, pedals, crank, chain, frame, seat and seatpost and also the tires, rims, on both bikes are going the same speed. The only difference on the two bikes are the cassette, hubs and spokes are rotating faster on the 20" bike.

The pedal and crank bearings should have exactly the same energy loss--they are rotating at the same RPM on both bikes.

The wheel bearings and cassette to chain mechanical resistance will be higher on the 20" as they are moving faster. The tire to road contact patch will be different since the tires have different amounts of air to be compressed and the wheels are different.

The rider wind resistance should be close to the same as the rider is in close to the same position. Generally this is considered the main resistance we are fighting at 20 MPh---the wind resistance of the rider.

So it seems our conclusion is the faster rotating 20" wheel takes significantly more energy than the 700c. I can fully accept the 20" wheel bearings taking more energy but I don't think that is significant. (significant in this comparison means noticeably slower)

Interesting ...

Rick
I am just trying to think this through....

prathmann

The smaller wheel will be rotating 'faster' if you're expressing the speed in terms of rpm - but the actual physical speed of the tires & rims in mph will be exactly the same as for the larger wheel when both bikes are traveling at the same speed. I.e. relative to the bike frame the tire&rim will be moving at 20 mph if the bike is going 20 mph relative to the road.
So to accelerate the bikes you need to expend an amount of energy necessary to get these wheel components up to exactly the same speed. If the masses were equal then the energy requirement would also be equal, but if similar quality components are used, the smaller tire and rim would also have less mass than their larger equivalents and would therefore require less energy to accelerate. But note that this only applies to the energy needed to initially get the bike up to speed and is very minor compared to the continuing energy to keep the bike moving at high speed against the drag of air and rolling resistance (and gravity if going uphill).

If other factors are kept equal then rolling resistance of a smaller diameter tire would be a bit greater, but the air resistance of the smaller wheel would be a bit less (assuming other parts of the bike & rider continue to have the same aerodynamics). On that basis I'd expect the speed of an ideal, optimized small wheel bike to be a little less than with a larger wheel when powered at relatively slow speeds by a weak rider where rolling resistance is significant. But conversely, that idealized small wheel bike should have a slight advantage at higher speeds where aerodynamics dominates when powered by a stronger rider.

HighValleyRanch

A 90" gear is the same distance traveled, no matter what wheel or bike size, gearing combination, cassette or freewheel combination. Therefore, if the cadence is exactly the same, both bikes travel at the same speed.
The difference then, can only be pointed to the rider's energy change, not the bike.

fietsbob

Development is the gear ratio x the wheel circumference, or how far down the road you go
with each pedal rotation .

multiply cadence rate, and you get 'speed'

little.old.lady

I had a folding bike in college, when I was young and strong, and I could go faster on it back then than I would probably do now on a regular bike. Some of it is the rider lol

berlinonaut

Again: Your small wheelers may bel slower as your big-wheeled bike - but not necessarily because of the wheel-SIZE... So you have proof about your special bikes being slower than your special big-wheeler, but no evidence for the reason. Especially not that small tires are in general slower than bigger ones.
Weight, component quality, frame stiffness, riding position, tire width and type of tire, speed etc. all play together along with the wheel size they may or may be not factors. On the very same bike different tires alone can make a big difference. Guess what happens if you bring a lot of different factors into play (as it is the case with comparing totally different bikes).

For a relevant experiment one would have to eliminate all factors aside of the wheel size. I.e. fit different sized wheels (with the same type of tires, hubs, spokes and rims) on the very same bike (should - while looking funny - theoretically be possible on a bike with disc brakes), install power cranks and then measure what speed is possible with which amount of power. Still it would be a small disadvantage for the smaller wheels because obviously in this experiment the frame would have to be designed for the bigger wheels.

Rick Imby

No way is it possible to run 20" and 700c on the same bike. The BB height with 700c would be so high....

jur

@berlinonaut: You're right, there are too many variables, and the combined effect of all variables can't be placed at the wheel size's door.

Because speed record velomobiles routinely use small wheels, we can reasonably dismiss the dominance of wheel size on the overall equation. I would call wind resistance first because it becomes completely dominant at peloton speeds, and frame stiffness second. I had a Birdy and though it is a superb folding bike, it is FAR from stiff. You can take the handlebars and twist the whole frame while seated by pushing sideways. It is astounding how much it will flex. Not to mention the suspension.

Rick Imby

A fairly even comparison would be Jur on his Titanium Swift vs Jur on the Road bike he used to ride. Both are /were Tricked out to the max.

There are easy roll out comparison plans that could compare two maxed out road bikes. We just need to find one guy with both a really nice 20" and a really nice 700c that wants to spend significant time riding both bikes.--

Steamer

One data point (earlier in this thread):


https://www.bikeforums.net/19175376-post52.html
https://www.bikeforums.net/19175923-post54.html

Steamer

Ok, but what about when wheel size is the primary difference between two machines that you are comparing? At that point the small difference in Crr you might see due to wheel size becomes all of the difference to consider.


As for how significant Crr is, that's more complicated and depends on the terrain and the rider.


The velonaughts I know spend a lot of time obsessing over tires because they know that rolling resistance is the one place where velos don't shine (that, and overall weight).

berlinonaut

Not really. Additionally you have i.e. rotating mass (lower with smaller wheels and therefor better) and - as jur said - aerodynamics (again better with smaller wheels). The question is wether these factors overrule the no doubt slightly higher rolling resistance or not. Not an easy case and I'd assume there exists no general rule here.