Alex carnavas

Is there any real difference between 20, 24, or 26 inch tires ?

Harutz

I believe Physics suggests that the larger circumference tire will travel farther faster with a given gear ratio.
Assuming you're capable of applying the necessary force, which I don't doubt you are.

What are you running 20 inch tires on, a recumbent? Or is it just a general question?

GriddleCakes

Yes, they will only fit on 20, 24, and 26 inch wheels, respectively.

Seriously, larger diameter wheels will accelerate slowly but will maintain momentum and roll farther, whereas smaller wheels will accelerate faster but won't roll as far and require more energy input to travel the same distance. Also, larger wheels will roll over obstacles (like curbs or logs) with more ease than smaller wheels, but smaller wheels are stronger and will take more force to knock out of true.

zeppinger

There is probably a significant difference between the 26 inch wheel and a 20 inch wheel but maybe not so much between a 20 and 24 or a 24 and 26. There is very little difference between a 26 and a 700cc IMHO.

wahoonc

Depends on what you are trying to do with them...

Aaron

Alex carnavas

Its just a general question. I'm Running on 26 x 2.25 I think.

Harutz

I would think you'd get more torque from a smaller wheel (though I can't imagine the inferior gearing on a small bike being anything close to that of a normal sized), but less speed and , like Griddle said, small obstacles would become much bigger.

Caretaker

Size matters.
That's why the 'ordinary' or pennyfarthing had a very large drive wheel. It was fast but very unsafe. Then came the 'safety' and the pneumatic tyre/tire of John Boyd Dunlop. The rest is history.

cooker

I assume you are talking about the size of wheels, not tire width or something like that.

Small wheels ride a bit bumpier on rough roads. I have to run my Bike Friday tires at 70-80 psi to feel as comfortable as I do on my road bike at 100 psi. That causes a very slight increase in rolling resistance, but I don’t notice it.

As already mentioned, smaller wheels are slightly quicker to accelerate, but also hold their speed less well, due to their lower momentum than big wheels, so you tend to repeatedly surge and lag compared to the more steady speed of a larger wheeled bike, but overall it requires about the same expenditure of energy to go a given distance.

The tires wear out slightly faster on smaller wheels since they make more revolutions per kilometer.

To compensate for the faster rotation of the wheels, small-wheel bikes can be fitted with larger chain rings and/or smaller rear cogs, so the rider can pedal at the same cadence as on a large-wheel bike.

Many small-wheel bikes, like most Brompton and Dahon models, are intended for urban utility use, and not designed for speed – they have a more upright rider position, so that makes them slower than a road bike, but it is not due to the wheels. Small-wheel bikes designed for speed, with a forward leaning rider position, like some Bike Friday, Moulton or Swift models, are about as fast as large-wheel bikes.

Smallwheels

For somebody living in a city and riding on streets the small wheels are better. The faster acceleration makes riding fun. The wheels are stiffer and stronger than bigger wheels.

They do not roll over bumps as well as larger diameter wheels. That is why having a suspension helps keep the rider more comfortable. It is for this reason I bought a Dahon Smooth Hound. It has a front suspension. It smoothes out small and large bumps a little. It doesn't jar my wrists when it hits cracks or small holes. I put a Thudbuster seat post suspension on it and have a really comfortable bicycle.

Small wheels are not great for off road usage if having a smooth ride is one's concern. I had a recumbent with dual 20" wheels. When I rode it down a bumpy dirt road it was very uncomfortable because it didn't have a rear suspension. The design of the bicycle prevented me from being able to stand on the pedals to avoid the beating. With a rear suspension a 20" wheel on a recumbent wouldn't be a big deal.

Fatter lower pressure tires roll smoother than skinny tires. The problem with fat tires is their weight. With 20" tires the weight will be much less than 26" tires of the same width. They will still give the cushioning effect but will accelerate faster. This is probably only important with unsuspended bicycles. To me the benefit of having a suspension is to be able to have high pressure tires to roll faster and also have a more comfortable ride.

My Smooth Hound is for sale. (anybody interested?) I don't use it in the winter. Riding on snow is similar to riding off road. Bigger tires do better. I'll keep the big tire bicycle for now. If I move to a non-snowy area I'll switch back to a small wheel bicycle.

prathmann

The ordinary needed a large drive wheel since it was pedaled directly with no intervening gears. A smaller wheel would therefore have required a greater cadence for a given speed. With the advent of chain driven bicycles, there was no longer a need for such a large drive wheel since the chainring and cog sizes could be adjusted to get any desired gearing. Our system of 'gear inches' to designate bike gears still stems from a comparison to the ordinary - i.e. a gearing of 60 gear inches is equivalent to riding an ordinary with a 60" diameter front wheel in terms of the cadence required for a given speed. My 20" wheel folder and my 700c road bike both have the same high gear (109 gear inches) - but the folder uses a 60 tooth chainring and 11 tooth cog to get that compared to 52 and 13 on the road bike.

So gearing can take care of the effect of wheel size on speed vs. cadence, but there are still some other effects. Aerodynamics are better with smaller wheels, but rolling resistance and comfort over bumps are better with larger ones. Smaller tires wear out faster and if you're using rim brakes there are more issues with overheating the rims when they are smaller diameter.

Roody

I think a rough ride also means poorer handling and steering. When the front wheel bounces up into the air, it loses contact with the ground. Therefore it loses steering ability for a time.

I believe 29 inch wheels were first introduced on mountain bikes because they provided both a more comfortable ride and better steering control. Now 29ers are becoming popular for street use.

B. Carfree

Sometimes smaller wheel sizes are dictated by frame design to allow for better (or worse) fitting or ride characteristics. For example, for a typical female (somewhat short with long legs relative to torso), a proper fit often requires a short top tube. However, that short top tube can lead to some issues with pedal/tire overlap. This is often dealt with by using 24 inch wheels.

On the other end, many small bikes like Bike Friday's have a rather small amount of trail (in order to keep the handlebars out of your stomach). While this is not caused by the 20" wheels, the twitchy feel is exacerbated by them. There are a lot of Bike Fridays here in Eugene (they're made here) but I hate riding with people who have them; they are generally too squirelly for my comfort. However, a small number of folks seem to have tamed the little beasties, so it can be done.

Roody

And what about 29"?

Smallwheels

One thing I should have mentioned is that being able to accelerate quickly in traffic is a real benefit and contributes to safety. It's also impressive to see, especially to non-cyclists sitting in their cars.

prathmann

The amount of trail is determined by the geometry of the fork and the headtube angle and has nothing to do with the position of the handlebars relative to the rider. If GreenGear wanted to increase the amount of trail all they'd have to change is to reduce the rake of the fork. In fact, I can put my BF Pocket Rocket together with the front fork reversed to greatly increase the amount of trail - and did so once accidentally. Feels stable but sluggish and is also more prone to flip on hard braking. Assembled properly I find the handling of my Bike Friday to be somewhere in between two of my 700c wheeled bikes - it's a little twitchier than my touring bike but less so than my Cannondale 'crit geometry' bike.

wahoonc

I ride two very similar bikes: one with 20" wheels and one with 26" wheels. Surprisingly they weigh about the same due to the type of construction. The 20'" wheeled bike accelerates quickly and also loses speed quickly when coasting, it is quick handling and easy to mount. The 26" wheeled bike is slower to accelerate but seems to be easier to maintain speed on. It is not as quick handling in close quarters and is harder to mount up on. Also the 20" wheeled bike is easier to transport and store. I also have a 16" wheeled bike but it cannot really be used as a comparison with the other two.

I also have bikes with 700c (28") wheels, they ride similar to the 26" wheeled bikes. Tire choice and frame geometry are going to make more of a difference than wheel size IMHO.

Aaron