Benefits of Solid Tires for Bicycles: Improved Ride & Reduced Wear

[Cyrus]

Some of these postulates are rediculous

How do you figure?

 

[berkeman]

How do you figure?

I think he may have been referring to his own post. Like this part:

Also the logistics of shipping pieces of heavy solid rubber like that would not be feaseable.

J/K

 

[SRode]

Average car tire weight 25lbs. Average truck tire weight 120lbs.

Look at the average sedan tire 205/60/15:
section width 205mm, section height (.6*205) 123mm

Tires are not perfectly cylindrical but you can estimate their volume:
15in = 381mm
(205mm)*pi*((381mm+123mm)^2 - 381mm^2) = .07m^3

A tire is primarily carbon black, synthetic rubber, and natural rubber.
natural rubber has a density of .94 g/cm^3 = 940 kg/m^3
synthetic rubber has a density ~1.2 g/cm^3 = 1200 kg/m^3
Carbon black is just a reinforcement, and becomes neglible when you are talking about filling the entire inner volume with rubber.

You solid rubber car tire (assuming your using the least dense material of natural rubber) now weighs 66kg or 145 lbs.

Now here's the logistic portion of it beakman, you have increased the weight of your tires 5-6 times. Thereby, you have reduced the amount of tires you can ship at any time because you will exceed the gross tonnage capacity of whatever you are transporting your tires with, such as overland freight, 5 times as fast. Your shipping cost would go through the roof, and tires would be rediculously expensive.

Also, you'd never be able to produce solid rubber tires with natural rubber, so your only choice is to use synthetic rubber which is derived from petroleum. Ignoring the peak oil and enviromental footprint aspect of this, your cost would again increase from oil competition so you could produce rubber. That is why the solid tire concept is logistically impossible.

Things are engineered in a way for a reason, instead of insulting someone who is trying to enlighten you, perhaps you should take a minute to think and research before you question their veracity

 

[berkeman]

Things are engineered in a way for a reason,

You are absolutely correct. But tires are not engineered the way they are to minimize shipping weight. Sorry if my post offended you...personal insults are not allowed here on the PF. I'll go back and see if I can tone it down some. Still, as Cyrus pointed out as well, several of us were a bit confused by your post.

 

[FredGarvin]

Look at the average sedan tire 205/60/15:
section width 205mm, section height (.6*205) 123mm

Tires are not perfectly cylindrical but you can estimate their volume:
15in = 381mm
(205mm)*pi*((381mm+123mm)^2 - 381mm^2) = .07m^3

A tire is primarily carbon black, synthetic rubber, and natural rubber.
natural rubber has a density of .94 g/cm^3 = 940 kg/m^3
synthetic rubber has a density ~1.2 g/cm^3 = 1200 kg/m^3
Carbon black is just a reinforcement, and becomes neglible when you are talking about filling the entire inner volume with rubber.

You solid rubber car tire (assuming your using the least dense material of natural rubber) now weighs 66kg or 145 lbs.

You are under the impression that, if tires were solid, they would keep the same geometry. Structurally, I don't think the tire could support itself. It would have to be a much lower profile tire.

 

[SRode]

Ah, well then that's a whole different ball game. If you mean somthing like this:
http://www.speedace.info/speedace_images/michelin_tweek_airless_tire.jpg

There was a reason they haven't started producing them yet tho, I think it was that they transfer too much vibrational energy making them noisy.

 

[russ_watters]

Bad tone or not, SRode, a very good portion of what you have said so far in this thread is wrong, as the others have pointed out.

 

[FredGarvin]

Ah, well then that's a whole different ball game. If you mean somthing like this:
http://www.speedace.info/speedace_images/michelin_tweek_airless_tire.jpg

There was a reason they haven't started producing them yet tho, I think it was that they transfer too much vibrational energy making them noisy.

That is the exact same tire/rim combo I have seen in industry design mags. The rim becomes a compliant part as well as the tire.

 

[Mech_Engineer]

Just to add in my 2 cents...

One of my friends a couple of years ago tried using some off-the-shelf solid foam inserts in his bicycle's tires to replace the tubes because he got sick of getting flats... it was a disaster.

The foam inserts were very difficult to put in (think of trying to mount a tire on a wheel with the tube already inflated), they had terrible vibration transmission AND higher rolling resistance similar to an under-inflated tire, and they were much, much heavier than a tubed tire. He found it much more difficult to ride his bike in all situations, and needless to say went back to tubes immediately.

That has been my one and only experience with "solid" bicycle tires.

 

[LURCH]

"...that vibration will tear things appart and cost money." Speaking of which, wouldn't solid tires cost a lot more?

 

[K.J.Healey]

Just to add my own comments:
1) Concerning the friction:
Theres no reason you can't have a "solid" wheel that can still slightly deform. Imagine a regular car wheel but instead of a whole tire just glue a strip of rubber to the outside. The material itself can have compression and deformation without the need for an air pocket.
I would assume that for a bike you really don't need THAT much friction to get moving/keep moving/change direction.
2) The air pocket provides a localized damping gap. While you could account for the increase in vibration with some expensive suspension, you have the problem of there being no local damping between the ground and the solid tire. This leads to hitting a curb permanently deforming the solid material, where before it would allow a reversable deformation due to the air and flexability.
If you don't plan on hitting anything sharp, or hard, then it could work and avoid this problem.
3) Weight should not be an issue. I imagine that if you removed the air out of a tire, put some glue in it, pressed the rubber flat to the wheel, and trimmed off the excess it would be just as easy to rotate, and would actually be slightly lighter.

I would imagine that you would basically just have such low profile tires that there is no air. That would be the most efficient way.

I'd think its all a matter of what kind of abuse the tire itself could take without the damping.

 

[AlephZero]

Just to add my own comments:
1) ... I would assume that for a bike you really don't need THAT much friction to get moving/keep moving/change direction.

To a first approximation, the friction coefficient limits the maximum accel and decel without wheel spin, independent of the mass of the vehicle.

To produce an acceleration a, you need a driving force = ma.
For a given friction coefficient mu, the maximum frictional force = K. mu.m.g (where K is a constant depending on the weight distribution between the wheels and the number of driven wheels).

So the mass cancels, and a is proportional to mu.

A bike that only accelerates and brakes at the same rate as a 30 ton truck is no fun to ride, so for a marketable bike you need MORE friction.

3) Weight should not be an issue.

High performance vehicle designs minimize the weight on the "undamped" side of the suspension, to improve handling and roadholding. For example steel wheels are replaced by more expensive lightweight alloy wheels. So extra weight on the wheels is definitely an issue.

 

[K.J.Healey]

By saying weight is not an issue, is that you could make the same diameter wheel (for a bike) that weighs the same as current wheels. Thus not an issue as to whether or not the idea would work.

As for the friction:
We're talking mostly about bicycles. People riding bicycles can't provide the same torque as any truck.

And as for the force needed, wouldn't you have:
for Force_Rider > mu_static*m*g : Accel = 0 (spins)
for Force_Rider< mu_static*m*g : Accel = Force/m

We want Force_Rider < mu*m*g
That force has no mass really, its the torque of the pedaler applied at that distance R of the wheel through the gears.
Not the same m.

 

[Innomen]

The main reasons that bikes still have inflatable tires as opposed to a whole new range of materials that addresses all concerns are convention and money.

Status quo defenses aside, I refuse to believe a material can not be developed which would successfully replace air as a filler. Now before you titter with correction pen glee let me make it clear that I mean one possible material for each given purpose. I realize no material can be as versatile or cheap as air, but I could easily see a range of foams to simulate any given psi at acceptable weights for given purposes.

Some bike tires are heavy soft and wide some are narrow hard and thin.

Solution? Different tires for different functions. Dismissing a material solution out of hand simply because its not going to be good in ALL cases is like dismissing the whole concept of a bike because you'd need one for going down steps and one for the Tour de France.

The VAST majority of arguments against puncture proofing systems of this general type (solid tires and foam air replacement) are anecdotal.

Like, "I knew this guy that tried it and it sucked therefor the whole concept is fail."

Please.

The real problem is money/marketing. Some companies currently offer solid tires, but because the tire sizing system for bicycles is a tradition choked byzantine non-standard nightmare a serious problem becomes choosing the right tire for your bike at a distance.

Some sites that sell these have complicated web apps where in you have to take apart your tire and feed in measurements accurate to the millimeter on bead width and depth and even then you are taking your chances, and you have no assurance that a simulated psi for your needs will be available.

Need I mention the money that's made selling replacement tubes and so called puncture resistant tires? Ironically often made of Kevlar as if that's an advantage, knife proof vests are harder to make than bullet proof ones, and a nail or a piece of glass is much closer to a knife than a bullet.

Another set of arguments against solid tires come in a surprisingly personal form. Such as "you are just lazy, man up and learn to change an inner-tube."

This argument is hilarious to me because it assumes the only reason you innovate is less work.

I personally want solid tires because I narrowly avoided death as a result of a blowout once.

I'm willing to pedal a little harder, or pay a little more to permanently close one path to that type of incident. And I'm not alone.

Just wanted to go on record somewhere about this. This debate needs to be had and the technology needs to be developed. The social advantage to tons of people on bikes instead of in cars is hard to over estimate.

I don't think it's too much to ask that we develop the bicycle equivalent of a good pair of walking boots. Something that will only fail when its worn through. Indeed it's tempting to look at the various densities and compositions of shoe rubber.

I think a 27 inch ring shaped Nike would do nicely. :)

 

[Ranger Mike]

all pneumatic tires ( a universal statement) act as SPRINGS. ifin they did not your dentist bill would be expensive. solid wheels are for the Flintsones. solid tires have more moment if inertia and weigh more..exactly what you do not want for performance and economy. years of terch wnet into the current kelvar belt radial tires we use today..ifin firestone and goodyear thought solid was better it would a happened.

 

[xxChrisxx]

Solid tyres do not generate high slip forces beucase they are much much stiffer than pneumatic tyres. This makes turning at anything above walking pace pretty much impossible.

This is basically the primary reason for having air filled tyres.

Historically all wheels were solid, on old prams, stagecoaches, penny farthing. They moved from solid wood with a metal coating to metal with a solid rubber coating.

The secondary reason was ride quality, as many other people have said air acts as a spring to reduce vibrations.

 

[Innomen]

It's funny how whenever this debate crops up, people seem to forget the existence of polymers.

Humanity is capable of producing a substance which is springy and solid.

Seriously, I grow weary of intelligent adults speaking like variable density materials are science fiction, while sitting literally surrounded by them in most cases.

There are other points on the solidity spectrum between gas at one end and steel solid at the other. Even natural rubber's elasticity and density can be tailored to a significant degree.

As to the also all too common ride complaint, again, we clever monkeys have the ability to produce other means of suspension and shock absorption. Indeed, my mountain bike already has a sweet set of examples on both wheels, the seat post, and the seat. Not counting the rubberized handles, padding of the seat, or the shock absorption from my legs since I'm standing most of the time. All of which was there on the bike when it arrived indicating shock was a known issue even with pneumatic tires.

I later put 80 PSI tires on it. They ride like they are solid already and that's part of the point.

The kicker: I already have a solid (low density polymer, not iron clad wood) tire on my electric bike, but the problem is its too soft, and it's the only variety that will fit that rim, which is in turn the only one that will fit that bike.

It rides like a 40 psi, (that's the pressure it was made to emulate) but I want 80. Plus it's knobby, I want a more street and trail tread. But again, no choices.

The question of whether or not this is possible/viable is already answered, and has been for a long long time, the only thing needed now is refinement, distribution, and education.

Continued debate on it in my opinion is like crystal spheres vs elliptical orbits.

The only real problems with a refined solid polymer single pressure tire would be weight if you are a racer type, availability, and variability. Being able to change tire pressure in the field to suit is definitely a huge advantage.

But if your bike has a specific job, such as a commuter bike, choosing an ideal pressure is possible.

years of terch wnet into the current kelvar belt radial tires we use today..ifin firestone and goodyear thought solid was better it would a happened.

(Ifin? Really? I'm from Kentucky and even we don't talk like that. I hope you are kidding and I just missed it.)

1. I'm talking about bikes, not cars. Though I will admit I hold the same opinion for cars. More so actually since as a safety feature its value on cars is much greater. I'm not likely to kill someone else in a bike wreck.

2. Solid tires aren't developed for the same reason GE never made permanent lightbulbs for the mass market, if at all. Planned obsolescence. Would you spend money developing a product that would lose you repeat business?

3. Ironically, Kevlar is one of those magic polymers everyone seems to keen to dismiss, but it was introduced in 65, it's not exactly cutting edge stuff.

 

[xxChrisxx]

.

There certainly are applications where solid tyres are used, solid wheels are used when handling isn't a premium but the likelyhood of a puncture is. Most forklifts use a solid tyre iirc. Suspensions generally aren't tuned to deal with the small undulations of road surfaces. EG running over stones, but cope with larger movements of the geometry. You can't really get a single passive suspension system to cope with both very well giving a perfect ride. Adding a second suspension that takes over the job that the air is doing, is simply adding needelss cost.

It's easy to go far beyond this anyway, Michelins Tweel is a great example. They are able to repicate the effect of pneumatic trail, use minor deflections to rule out small bumps AND it can't get a puncture. It is also more controllable as a suspension component.

They look stupid, but tweels are the future.Bottom line is, pneumatic tyres are used because they are cheap and well understood and work pretty well for the job they are designed for. Therefore there is little urgent need for change. We could do it if the need arises, but lining up a brand new system, literally reinventing the wheel is an unnecessary expense for a questionalble performance increase.

 

[S_Happens]

Sorry, but I'm not going back to read this old thread in entirety.

I'm under the impression that there are bicycles made for industrial use with solid tires (also under the impression that we've been testing some at work for the past few months). I'll look into it and post up some info when I go back next week.

 

[Innomen]

Adding a second suspension that takes over the job that the air is doing, is simply adding needelss cost.

Depends on your definition of needless. But that aside, my contention is that a solid tire can be developed that would do the job the air is doing.

They look stupid, but tweels are the future.

Heh, I think they look awesome, but I don't know about them being the future. Call me cynical but I think it's more a tactical patenting niche market effort. Patent all the roots of the only viable alternative that they can see, license fee it into consumer oblivion, and then sell it to low profit niche markets to defuse claims of anti-innovation practices.

This of course assuming they didn't design the polymer spokes to fail after a given amount of time creating a similar repeat business cycle as conventional tires.

but lining up a brand new system, literally reinventing the wheel is an unnecessary expense for a questionalble performance increase.

It would be but my goal is not a performance increase, indeed I'm willing to accept a performance decrease in exchange for a safety/durability increase.