What effect do bicycle tire sizes have on riding?

[BG213]

Hello all. Am coming back into cycling from a long time "out of the saddle" and have a kind of noob question I cannot really find an answer to. What are the advantages and disadvantages of larger and smaller, thinner and wider tires on a bike? For example smaller 20" or even the 16" tires vs. 26" or larger. Similarly narrow tires below 2" vs. those fat tires of 2.5" or 4" you see. Why would one choose one of these options over another? What is each good for and bad at? Thanks.

 

[Dogtrousers]

Wheel size tends to go with the type of bike. Road bikes tend to standardise on 622mm rims (aka "700c" - don't ask) Mountain bikes tend to have 584mm rims (aka "650B" - no, really, don't ask). I think these are roughly 29" and 26" but don't quote me. Folding bikes and shopper bikes have smaller wheels, for example the Brompton has 349mm rims (16")

Why the different sizes? The wheel size tends to go with the design of the bike and its frame.

The small wheels on a folder like a Brompton are necessitated by the bikes design. They don't cope well with particularly rough surfaces but they need to be small for the bike to fold up small.

I don't know anything about Mountain Bikes but I do know they can come in both 29 and 26 inch and people like to argue/discuss about them.

Road bikes are pretty much universally 700c (622mm) although with the advent of disk brakes there are some gravel bikes that can run both 700c and 650b wheels. With rim brakes you were stuck with one wheel size. Also, smaller riders may prefer smaller wheels as a small frame with big wheels can be unweildy. But this can be a problem for small pro riders as they need access to standard spares during races. Emma Pooley (a small but nonetheless very successful pro rider) talked about this.

That's wheel size, which is one aspect of the size of a tyre

Then there's tyre size, which is how fat the it is. Typically the fatter the tyre, the rougher surfaces it can deal with, and the lower the pressure it can take, and fatter tyres tend to be more comfortable. In an ideal world skinny high pressure tyres are faster - and that's what they use on the almost ideal surface of the velodrome. But on the un-ideal surfaces of real roads this isn't true. The question of tyre size, rolling resistance and pressure gets debated endlessly. Frame design comes into it too. Some frames limit the maximum tyre size because they don't have room ("clearance") for fatter tyres.

Tyres with grippy patterns (eg Mountain bike "knobblies") are for when the surface is softer than the tyre itself (eg grass or mud). Where the surface is harder (eg tarmac) slicks are generally used. There are also half-way tyres for use on tarmac that have grip patterns - about which there are often arguments (they provide grip/no they don't they are purely cosmetic).

Then there's the question of tubed versus tubeless, and you have fuel for endless arguments.

 

[wiggydiggy]

My commuter bike has 45mm tyres on it, mostly for comfort as the larger size helped even out bumps. They are semi slick but have been used off-road withou issues.

https://www.conti-tyres.co.uk/commuting-touring/contact-plus

My MTB (in profile) has 29" wheels as I mostly ride cross country routes on it and I read they were better because they 'rolled' better than the then standard 26". Though chunkier it's still a good tyre to ride on roads as it's a not an out and out MTB tyre for sloppy mud.

https://www.schwalbe.com/en/tour-reader/marathon-plus-mtb

 

[All uphill]

Wheel size tends to go with the type of bike. Road bikes tend to standardise on 622mm rims (aka "700c" - don't ask) Mountain bikes tend to have 584mm rims (aka "650B" - no, really, don't ask). I think these are roughly 29" and 26" but don't quote me. Folding bikes and shopper bikes have smaller wheels, for example the Brompton has 349mm rims (16")

Why the different sizes? The wheel size tends to go with the design of the bike and its frame.

The small wheels on a folder like a Brompton are necessitated by the bikes design. They don't cope well with particularly rough surfaces but they need to be small for the bike to fold up small.

I don't know anything about Mountain Bikes but I do know they can come in both 29 and 26 inch and people like to argue/discuss about them.

Road bikes are pretty much universally 700c (622mm) although with the advent of disk brakes there are some gravel bikes that can run both 700c and 650b wheels. With rim brakes you were stuck with one wheel size. Also, smaller riders may prefer smaller wheels as a small frame with big wheels can be unweildy. But this can be a problem for small pro riders as they need access to standard spares during races. Emma Pooley (a small but nonetheless very successful pro rider) talked about this.

That's wheel size, which is one aspect of the size of a tyre

Then there's tyre size, which is how fat the it is. Typically the fatter the tyre, the rougher surfaces it can deal with, and the lower the pressure it can take, and fatter tyres tend to be more comfortable. In an ideal world skinny high pressure tyres are faster - and that's what they use on the almost ideal surface of the velodrome. But on the un-ideal surfaces of real roads this isn't true. The question of tyre size, rolling resistance and pressure gets debated endlessly. Frame design comes into it too. Some frames limit the maximum tyre size because they don't have room ("clearance") for fatter tyres.

Tyres with grippy patterns (eg Mountain bike "knobblies") are for when the surface is softer than the tyre itself (eg grass or mud). Where the surface is harder (eg tarmac) slicks are generally used. There are also half-way tyres for use on tarmac that have grip patterns - about which there are often arguments (they provide grip/no they don't they are purely cosmetic).

Then there's the question of tubed versus tubeless, and you have fuel for endless arguments.

You deserve a prize for that answer @Dogtrousers

 

[fossyant]

Nah he missed 27.5 (650b) MTB tyres too, but I'll give him that as he said he didn't know.

I won't mention about double and triple compound tyres either - even MTB's have them. Confusion confusion.

 

[Ming the Merciless]

Smaller wheeled bikes accelerate quicker and are more agile. This is great for trips in traffic or around town. The smaller wheels don’t cope so well with potholes and speed humps.

Larger wheeled bikes roll better on rough roads, but are slower to inputs to change direction.

Wider tyres allow more volume and lower pressures for a given wheel size. This allows a comfier ride with much of a roughness of a road filtered out, barring big holes.

Smaller wheels are stronger than big ones.

The best tyres out there, the ones with the most R&D in them, are nearly always available in 622 size, but often are not made for other sizes.

Smaller wheels are more aerodynamic than large ones.

 

[BG213]

I have narrowed down my choice of bike (for now at least) to the Tern Link (20x2" tires) and Node (24x2"). Where I live there is a fair amount of road debris and uneven surfaces and I am looking to ride it for perhaps prolonged distances. So you would say the Node would ride easier than the Link but wouldn't be as nimble and responsiveness to inputs? How much of the disadvantages of a smaller wheel can be offset with an adequately shock absorbing seat post or saddle? Which would be better for mild off-roading? When buying a folder would you follow the rule to "buy the biggest wheels you can get away with carrying folded (on a bus, train, car trunk etc.)"? I know, I know, its all kind of subjective.

 

[BG213]

Oh, I have to ask. Do you end up peddling more with smaller tires to go the same distance and speed?

 

[biggs682]

My favourite wheel size is the good old fashioned 27 X 1 1/4" aka as fitted on majority of British road bikes between the late 60's and 70's .
When fitted with a pr of decent tyres they just seem to roll along so nicely.

Oh, I have to ask. Do you end up peddling more with smaller tires to go the same distance and speed?

As per the above question my answer would be I don't think so as the gearing is normally tailored to suit the bike design and intended use .

So as long as it's an adult sized bike for road use then my guess would be no .

Someone else will be along to say different soon 😉

 

[Dogtrousers]

Oh, I have to ask. Do you end up peddling more with smaller tires to go the same distance and speed?

No. The gears compensate for it.

I sometimes ride a Brompton. When first setting out after not riding it for a while it feels decidedly twitchy but after a few miles I just forget all about it. I've ridden the Brompton (16" wheels) on good but unsurfaced tracks but it really prefers the road. It's fine over longer distances but I don't find it as comfortable - maybe just because it's not what I'm used to for long rides.

Choosing between the bikes you name, I'd have thought that wheel size would be one consideration among many but not a decisive one.

 

[biking_fox]

Wider tyres allow more volume and lower pressures for a given wheel size. This allows a comfier ride with much of a roughness of a road filtered out, barring big holes.

Conversely narrower tyres can be run at a higher pressure giving a faster and more responsive ride with less friction, and more efficiency. Depends on what you prefer and what surfaces you ride on. Narrower tyres tend to have thinner rubber and be more puncture prone than a beefy fat heavy MTB tyre.

IF you ran at the same gear ratio a smaller wheel would need more pedal stokes to achieve the same bike speed (and hence be less efficient, but as above I think the gears sort all of this out. I don't think the efficiency in the end is any different.... mostly dominated by friction at the road surface and air resistance. Maybe a smaller wheel has lower air resistance?

 

[MichaelW2]

When it comes to tyre width, wider tyres are heavier, have more aerodynamic drag but lower rolling resistance. They run at lower air presure. Tyre construction can be tough, heavyweight or more flexible lightweight. Rubber can be soft and grippy or hard and hardwearing All of these variables determine the ride quality and best use.

A thin, light high pressure slick tyre is better for fast riding. A fat, light slick is more efficient at lower cruising speeds.
Tyre tread is required on rough or slippery surfaces
For most general purpose riding, a medium width, medium weight tyres with light tread is usually optimum.
Pro racers are trending to wider tyres. Off roaders are trending to fat tyres.

 

[MichaelW2]

With rim diameter, there is a limit to how many common rim sizes the industry can support. Ideally, there would be small, medium and large diameter rim standards, with tyres from narrow to fat in each size.
In reality, things are more complicated and stupider.
700c can support narrow road racing to fat off road use for small size males and upwards.
650c can support narrow racing tyres for small women and upwards but no support for med or fat tyre.
26MTB could support narrow road to fat tyre for med women/small males upwards but no support for road racing. This global standard is being abandoned in quality bikes.
650b/27.5" can support med road tyres and fat offroad for small males upward and is supposed to replace the 26" . Just different enough from 26" to be stupid.
24" kids bike but lovely size for small women.
20" MTB. Also used in folders
16" as in Brompton folder

Aside from these standards, there are lots of vintage/oddball sizes best avoided due to tyre availability.

 

[Ming the Merciless]

Oh, I have to ask. Do you end up peddling more with smaller tires to go the same distance and speed?

No you don’t need to sell more with smaller tyres. 😁

 

[presta]

Schwalbe Technical Info here.