How important is wheel circumference?
 

Hello,

I'm trying to find information about the size of bicycle wheels as it relates to its efficiency. Does wheel circumference factor in how efficient it is? Does it require less muscle power to move a smaller wheel or a larger wheel?

Can you help with some advice?
Thanks

My impression is that you have less rolling resistance and a smoother ride with larger wheels. Less weight, less inertia to get moving with smaller wheels.

I think the problem is that you don't really have a BIG choice in wheel sizes. When you look at bikes that are identically laid out for the same size people, they're all within 2 or 3 inces of the same wheel size as well. To get a lot smaller, you have to change styles as well (BMX, recumbent or whatever) or ditto to get a lot larger (Monster Cruiser) and those changes in style pretty well overwhelm any advantages or disadvantanges of wheel size itself.

Well, some people do claim significant benefits for 29" mountain bike tires, as compared to the "normal" 26" tires.

http://en.wikipedia.org/wiki/29er_(bicycle)

The difference between the wheel size of bikes commonly ridden is just tinkering at the edges. I don't see people riding ordinaries because of their more efficiently sized wheels.

That's actually a very good point! You can't divorce just one part from the rest of the bike when you're discussing efficiency. Everything works together and, what's good in one respect, can be a serious drawback in another.

You also really to define what you are trying to accomplish before you can discuss efficiency. Bike Friday, for example, has carved out a nitch market for bikes with 20" wheels mostly because they are efficient to pack and travel with.

I can't explain the science behind it, but its been my experience that a smaller wheel allows faster acceleration, but it's less efficient once normal riding speed is reached if you only consider the time it takes to go a certain distance. My thinking is that the taller wheel allows the bike to travel farther for each rotation of the wheel.

Also, the smaller wheel seems to take less strength to get up to speed, but requires more effort to maintain the same speed as a bike with taller tires.

I saw a similar effect when I replaced my car tires with lower profile 70s. it took a higher rpm to maintain the same speed in any gear than what the higher profile tires required. The change in tire size affected the gearing ratios.

The smaller wheel, all other things equal, has the advantage in every category except for rolling resistance. However, the tiny difference in rolling resistance is only of importance at low speeds. The faster you go, the better the smaller wheel will be.

This is only valid for typical wheel sizes. A two-inch wheel wouldn't be efficient, and a 200-inch wheel would be highly impractical...

So how were you measuring your speed?

At my LBS yesterday, a young woman pondering a mountain bike purchase first rode a regular bike with 26" wheels, then later took out a 29'er. She came back with the 29'er and was amazed at the difference she felt.

More effort, or a higher pedaling cadence? Folding bikes come with taller gearing (if they're using a different drivetrain at all) to account for their smaller wheels. That way, the rider can travel at similar speeds to their large-wheeled bikes while using a similar cadence.

Unless you're trying to shorten the overall gearing for track use, there's no reason to end up with a smaller tire circumference on a car. Go wider, get a larger wheel, or do both (my car's stock 195/60-15 tires can be replaced with tires & wheels carrying 205/50-16 or 215/40-17 while keeping an identical rolling circumference).

How did you know? The tachometer and the speedometer are effectively geared together. If it took 2500 rpm to produce an indicated speed of 60 mph to begin with, it'd take 2500 rpm to produce an indicated speed of 60 mph no matter what tires you put on the car. By the way, a rule of thumb for changing the size of tires on cars: To go to wider tires, increase the section width by 10 mm, reduce the aspect ratio by 10 points, increase the wheel diameter by 1 inch, and you'll maintain about the same actual tire size and gearing. E.g., my car came with 175/70R13 tires, and I replaced them with 185/60R14. There are calculators available on-line http://www.google.com/search?hl=en&n...or&btnG=Search

It's easy to get close by timing how long it takes to drive a mile. You can also take note of your RPM as you keep up with typical traffic or a friend in another car. You can also watch your fuel consumption go up (although that's not a good measuring method; your wallet will feel it, though).

The first hit in that search is the calculator I used all the time:
http://www.miata.net/garage/tirecalc.html

In looking at the Wikipedia article, I think it shows 2.3" difference between a typical 26" and 29" tire.

You would think that if going from a 26" to a 29" tire made a big difference, then we'd all be riding Coker Monster Cycles, and all the top mountain-bike riders would be using Coker 36" tires on their bikes.

For years, the European standard was 28" tires and the American standard was 26" tires. Maybe the Europeans were stupid for using those big tires. Maybe we were stupid for not using them. Or maybe there's just not really that much difference between the two.

By comparison, unicycles don't have available a cheap gearing method, so increasing the tire size is one way of going faster. Result: Coker 36" tires are very popular there, with several different companies making the unicycles to fit them.

The difference that people feel comes from the angle of approach as the tire hits a bump. A larger wheel hits the same bumps more gradually than a smaller wheel.

I run bikes with six different wheel sizes from 20 inches to 28 inches and would have to say that the 20 by 1.95 semi slick tyres on my folders spin up faster than any other wheels/ tyres I have while the 28 inch wheels on my vintage CCM's and Vintage Peugeot offer an unequalled ride but do take a little more time to spin up.

Climbing is a little easier on my 622 and 630 by 25 tyres (I don't run 23's) as they have the lowest rolling resistance, are the lightest of my wheels/tyres and are very aerodynamic... they also tend to be fitted to much lighter bikes.

Those 20 inch wheels (36 spoke) are probably the strongest wheel sets I have... a 700c would need 44 spokes to come close to their strength.

My 20 inch bikes don't give up much to their larger brothers and sisters in the ride department, are much better at quick manoeuvres, and I expect the fixed gear, being that it's lighter and faster... to stun a few poseurs.

Those 26 inch wheels sit in the middle and offer a nice balance between strength, ride, acceleration, and climbing ability. My double walled mountain bike wheel sets are really light and tough and even with wider slicks, they accellerate very quickly.

Larger wheels do handle bumps better than smaller wheels (it's that angle of approach) and this is why I opted to run 406 bmx wheels with 1.95 tyres on my folders instead of 451 high pressure skinnies...my small increase in speed would be gained at the cost of losing the good ride characteristics of the wider higher volume tyres.

There is so much you have to factor in when it comes to how bikes perform and most critical is the frame design and the type of tyres one uses...if you want to go really fast you give up ride quality, if you like a smooth plush ride then you probably won't be racing that balloon tyred bike.

Most people seem to choose bikes that put them somewhere in the middle of those extremes and I am no exception...even my vintage road bike runs 700:25 tyres at a slightly lower pressure cause if I am going to go fast I also want to be more comfortable doing it.

If you can fit on a 29'er it makes more sense on technical terrain as they can roll over surface irregularities more efficiently than smaller diameter wheels.

Those extremes in wheel size... :)

http://www.ravingbikefiend.com/bikepics/rambler4.jpg

http://www.ravingbikefiend.com/bikep...restfixed6.jpg

What is that top bike??

To the best of my knowledge and according to the serial number and date code... it's a 1940 CCM or a CCM made for another retailer. After stripping and re-painting I weighed it at 5 pounds (with bb cups) which is pretty light for this era.

I only got the frame... the tyres are from a '64 CCM, the cranks are period correct, the stem and fork are modern (needed a stronger front end), the bars are old cruiser bars that have been flipped, and the front brake is a Dia Compe lever mated to a Universal model 77.

I still haven't been able to id the saddle's maker.

You are correct that a car will always give the same speed per rpm in a given gear if the speedometer is hooked into the transmission. Though in my case, the speedometer cable is hooked into the front wheel's grease cap. Its a crazy old VW design. So, the speed reading is independent from the drive train.

I guess you could argue that the speedometer was also affected by the tire size. As the expected distance traveled per rotation of the tire has changed.

Is there a standard format for date codes? I'm still unable to find any info about my bike model. *shrug*

Yes. Let's ignore 24" wheelsizes and below. In fact let's just compare the range between 26" -> 27". Teh smaller the wheel gets, the less practical it gets. The eaiser it is falling into less than perfect pavement.

arnt 29ers not as strong as reg wheels (26)

Got this off the CR list quite some time ago...

1921-1936 - The first character is a letter and has a sequence of a b c d e h k l n p s t v w x z
1937 - 1948 - The second character is a letter and has a sequence of a b c d e h k l n p s t
1949 - 1960 - The last charctewr is a letter and has a sequence of a b c d e h k l n p s t

My frame has a second series coding with a D for 1940.

And as for Operator... you know that if Sheldon was here he would have given you a polite swat for discounting his much beloved Twenty's as being impractical and may have told you about his wife dropping roadies on while riding a Twenty, with a baby seat !

If you said this in the fixed forum they'd also be calling you on your badly mistaken information.

I find my Twenty's to be ideal for urban assaults and even plan on pulling off a century (metrics are too easy) on my fixed Twenty.

Wrong.

Let's not ignore smaller wheel sizes.

The odds of someone's 700:23 catching a bad rut and throwing the rider is far greater than the odds of my 20 by 1.95 wheels catching a rut and being thrown... that... and small wheeled bikes tend to be very recoverable in these situations.

A 20 inch wheel is far stronger than a 700c or 27 inch wheel...the odds of making a wheel taco with a 20 inch is far less and they get even stronger at 18 and 16 inch sizes.

Of course it is affected by the size of the tire/wheel it's connected to. All it's doing is counting the revolutions of the wheel.