gpsblake

Someone asked me this today and I didn't have an answer. Probably a stupid question but oh well, let me ask it.

Why don't they make bikes with tires larger than 27"? I would think someone in great condition would go faster on a 31" tire with the same gear ratios and such. I'm just curious the reason why tires pretty much stopped at 27 inches.

roadfix

Or, someone in great condition can go faster on a smaller set of wheels with a higher gear ratio.

khuon

Perhaps you could go back to the reason why the concept of the safety bicycle was invented in the first place.

Seriously though, the limits on the number of popular tyre sizes is basically one governed by the industry and the manufacturers. There is a lot of under-the-cover costs associated with maintaining many different sizes of tyres. Standardising on a couple keeps production and inventory costs down. It's all about economics.

lz4005

They do. The link below has cruisers with 36" wheels.

https://www.unicycle.com/shopping/shopexd.asp?id=435

Dahon.Steve

I like the idea of a larger size wheel for touring. Those cruisers are probably very comfortable. The larger the wheel, the more plush the ride. It's unfortunate the only bike in production with a larger wheel is a beach cruiser.

alanbikehouston

Bikes have been made with wheels ranging from about size 16 to size 70 inches. Today, in the USA, most wheels use tires sized at about 20 inches, 24 inches, 26 inches, and 27 inches.

But, without doubt, 28 inch tires have been the best seller. Around 1900, Raleigh began making the DL-1 with 28 inch tires. Until around 1970, that model, and its clones, were best sellers both and in the USA. That British three-speed bike that Americans called "an English Racer".

And, today, in India and Africa, hundreds of millions of people contine to ride the DL-1. Available new in India for around $50. Available new in the USA from "Yellow Jersey" for around $300.

From a pure "theory" point of view, twenty inch wheels are the best. A BMX wheel with 48 spokes, and wide, beefy 20 inch rim ain't NEVER going out of true. People ride these wheels off a twenty foot high roof, and land on concrete - neither their "IQ", nor the rim has gotten any smaller. Both are quite small, before, and after.

Dahon builds folding bikes for folks were are NBA height using these wheels. They can fold-up small enough to put your bike in a suitcase or in a backpack. Bents using these wheels would leave Lance in their dust.

But, sheep are sheep. Mountain bikes will continue to use 26 inch tires. Road bikes will use 27 inch/700c whees. Logic has nothing to do with how people spend their money.

lz4005

The down side would be that they will be more difficult to stop, what with the added rolling momentum of more tire farther away from the hub. Which is another consideration for wheels in general not being larger than they are.

Dahon.Steve

You should never mountain bike with a 20 inch wheel which is why Dahon never made one that size. It's too dangerous and uncomfortable for mountain biking. I have a 20 inch wheel bike and it's less comfortable than a 26' or 27' inch tire by far. Furthermore, the smaller tires slips into cracks and pot holes which makes riding more dangerous at night or even during the day. Trust me.. I have a battle scars from falling off my folding bikes. Last, the smaller tire (especially the rear wheel) wears out faster than a 700 cc tire.

The 20' inch wheel is far from perfect.

randya

I thought there were some mountain bikes being made with 29" front wheels and 26" rear wheels, similar to the wheel size ratio of off road motorcyles.

khuon

I don't know of any MTBs that have mixed size 29"/26" wheels. However, also bear in mind that 29" wheels is a marketting term for 700c sized MTB wheels. A 29" MTB wheel uses a standard 622mm rim size.

alanbikehouston

I gave my eight year old nephew a nice BMX bike with HUGE tires on wide 20 inch rims. He doesn't like "to share", but I take it for short rides. The seatpost and stem work for him, and not for me. But the wheels and tires could go anywhere, anytime, with any rider.

I have waaay too many bike with umpteen gears and 26 inch and 27 inch tires. I envy my nephew's joy in riding his one speed BMX bike with those "go anywhere" wheels and tires. His bike can take anything an eight year old boy can imagine (and they can imagine doing stuff that gives adults nightmares). Some of my road bike wheels could go "out of true" if I just THINK about the stuff BMX riders get away with.

Bekologist

Umm, Gary Fisher makes some mountain bikes with 29" wheels and has been for a few years. Edited to say, why doesn't he just call these 700c mountain bikes, maybe they'd catch on better?

gpsblake

Radical! I hate to have to find tubes or tires for that thing though.

Cheers,
Blake

khuon

Because then the "hardcore" MTBers would just cry, "d00d... that's a cyclocross bike with straight handlebars and I'm too manly for that!"

PWRDbyTRD

maybe 26" or 700c wheels are a good medium between size and weight. Bigger wheels will weigh more, right?

Maelstrom 

Wow, thats a well thought out statement. I can think of many reasons bigger wheels make no sense. Sheep nothing, bigger wheels don't make sense in dh, fr, street and a lot of xc. They have a place but a small one. Heck I run a 24" wheel on my one bike for strength and acceleration purposes.

Why does everyone believe there should be one way, variety, especially in the case of wheels, makes the most sense.

That and I would probably fold the wheel in 2 on my first 7 ft drop.

MichaelW

Ever since the Rover Safety Bicycle, wheel diameter has been separated from gear size, so it is really an issue of what size will fit the frame. You use the largest size possible to reduce rolling resistance. the limit being the length of the head tube and toe clip overlap
The 700c/27" size is the largest wheel that can be fitted into a normal size frame. There has been some rationalisation, so all the various 27" sizes are now reduced to a standard 700c .
700c does not work in the smaller sizes of road frame, hence the need for 26" wheels (650c).

With MTBs, the 26" was a historical accident. I dont see how it can be the ideal wheel size for every off-road rider. A 6'6" rider could use fat tyre 700c (29"), and a very small rider could use 24" and they would both have a wheel which sits happily in their frame with plenty of clearance. Small kids use 26" MTbs off road, and they are using big wheels for their size.

lz4005

The bikes are made by/for a sub-division of car tire manufacturer Coker, which also sells the tires, rims and tubes. I have no idea why they started making them, but the bikes do look cool. Unicyclers like using the big wheels on their touring rigs because that is the only way for them to get (what we would call) a higher gear ratio. Also, unicyclers are...different.

Retro Grouch 

I think there are a number of considerations.

The first has to do with building the rest of the bike. With larger tires you will encounter toe overlap with the front wheel sooner and have to do all of the things that manufacturers do today in order to avoid that on bikes with very small frames.

So far as using smaller wheels is concerned, I heard somewhere that rolling resistance starts going up rapidly when wheel size drops below about 24 inches.