Pneumatic Tyre Replacement

Where have you been?

N² lasts longer than air in tyres, and tires, but costs more because you can't dispense N² at home.

Solid tires build up too much heat.

These are still inflates. I was looking more for what Metalsmith posted. Now I have to find some for me vehicles!

A lady at my work boasted about getting pure nitrogen in her new tires. I held out my hand and said "This is 78% Nitrogen. That's good enough for me!"

There are some compelling reasons to use nitrogen gas. I had a car with aluminum rims but they kept deflating due to corrosion around the rims. They ran fine once I used N2 for convenience and safety. Even the little oxygen content in air is enough to produce corrosion. But air is cheap.

It's not the oxygen in air that causes corrosion. It's the water vapor which will condense in cool weather and screw things up. Air is cheap and so is nitrogen. A 300 ft*3 tank of either runs us about $15 US and lasts for a long time. You can also obtain a gas drier and make your own.

It is most likely the Oxygen.....so you are wrong. Though other things can also do it like some acids for example.

It is a combination of things, air (oxygen/Nitrogen/Carbon dioxide being the main constituents) being one of them.

Air usually has moisture in it except in a desert maybe....but Oxygen can react with many things all on its own......so the previous statement was mostly correct.

Also, water is composed of Hydrogen and Oxygen in a pure state, but is not in itself dangerous to most metals.

A simple experiment using pieces of clean (unpainted and not greasy) iron and/or steel, placed in water, then the water is then boiled to drive off any absorbed gases and something like paraffin wax or Vaseline jelly is added, to make a thick film on top while still hot, as sealing out the atmospheric Oxygen, will prevent any rust (corrosion) forming on the metal forever, or as long as the seal remains fully intact.

A test tube is a good container to use....

Break the seal and rust forms within the first 24 hours as atmospheric Oxygen absorbs quickly into the (previously) Oxygen free (boiled) water.....

The Oxygen is the most "active" major part of the air as far as I am aware, but my chemistry lies about 50 years ago in the school.....there can be tiny amounts of other gases that are fairly active, but most are cleared away by sunlight I believe....

Try the experiment, it will change your opinion.....Aluminium (wheels) will corrode under the same conditions )if the metal is unprotected for some reason), but will take longer than steel/iron and the corrosion tends to seal further corrosion out or at least slow it down....

A careful cleaning of the area of corrosion on the wheel, plus a quality wheel paint being baked on, would have fixed the air loss problem of the previous poster.

With all due respect, my advice was correct. Oxygen will not corrode aluminum. In fact the previous poster illustrated the chemistry that shows that oxygen is responsible for forming the corrosion resistant layer of Al2O3 that passivates aluminum and protects it from corrosion. The air in most compressor tanks is saturated with water vapor and when the tires are inflated, the expansion of the saturated air, results in liquid water condensing out from the gas. This water is reasonably pure and not corrosive by itself however, impurities (mainly salts) on the surface of the aluminum are dissolved by the liquid water to form corrosive chemical mixtures. This is responsible for aluminum wheel corrosion. No water - no corrosion. Now on to your steel experiment; the answer is the same; no water - no corrosion.

You are clever, but not clever enough, you forget that what are called "Aluminium Wheels", are NOT in fact pure Aluminium as that is far too soft.Which makes them even more easily damaged and would also make them far too thick to be attractive!

There are many additives to make the metal hard and strong enough to use as wheel metal. Which is why the wheels are fully coated, all over, to stop any corrosion happening shortly after manufacture, before corrosion starts.

By the way, just to help you to fully understand the chemical reaction, the chemical name for Aluminion corrosion is AL(OH)3. The question now is, do you understand what the "O" means in the chemical formula? If not, I may tell you that it refers to Oxygen! WOW!!!

If the "O" was not there, you would not have corrosion.

Also, as Oxygen is a given component of water, your original statements are also false as if Oxygen was not present, NEITHER WAS AND CAN WATER/MOISTURE!!!

Now do you believe me that Oxygen plays a LEADING role in Alumium corrosion? (as well as corrosion of many other metals too! I cannot say ALL as I am not a good chemist, but maybe someone else can!!)

A good web page to read I find is here:-

Aluminium hydroxide

I have not forgotten that aluminum wheels are not made from pure aluminum. Each aluminum alloy has its uses and individual corrosion resistance properties. That's not really the point here.

The point is that you appear to believe that because the chemical formula for a material contains oxygen, that it will react with oxygen.That is a false chemical assumption. The molecules Quartz (SiO2) and Sapphire (AL203) also contain oxygen, but are not soluble in, or corroded by water or oxygen. Just because an element appears in a molecular formula does not mean that the molecule will be attacked by that element.

You can store aluminum or its alloys in a tank of oxygen for centuries and not detect any change. When it comes to corrosion of aluminum alloy or steel wheels, liquid water is the culprit.

Unconvincing.

Aluminium is a metal that is chemically very reactive, you could say that is it's major problem, it can combine easily not only with Oxygen but several other chemicals as well, which is why its only found mixed in with various other chemicals and never pure in nature, even though it forms 8% of the world's crust by weight.

Strangely it is not "used" by any known plant or animal in spite of it being widely distributed in its various forms....but is tolerated by most, if not all.

Many years ago it was a component of medicines for people with gastric problems, but is thought to have some negative effects on parts of the brain cells in old age, Alzheimer's disease for example, though I personally have not seen it mentioned recently for that...I believe that Hysteria has died a death.

Look, the topic was corrosion of aluminum alloy wheels, not its use by plants or animals, or its use in medications. You are correct that aluminum reacts with atmospheric oxygen to form a thin tenacious skin of aluminum oxide. This skin forms the basis for the corrosion resistance of aluminum and its alloys. It is also the reason that aluminum must be arc welded in a neutral atmosphere such as helium or argon. So atmospheric oxygen protects aluminum, it does not corrode it. Corrosion is almost always electrolytic in nature and the electrolyte is almost alway water based.

4Al + 3O₂ ---> 2Al₂O_{3
So there will be a reaction with oxygen. Other factors such as moisture content with air can produce many other corrosive situations. Including a reaction with CO2 to form weak acids. An initial new tire installed with N2 is often provided with the install at very minimum cost. This was provided by the seller (if available). Subsequent refills with nitrogen to top up or adjust is usually about $3/tire, My service guy provided a thorough cleaning of the rims and sprayed an inhibitor of some sort on the inside. Still with temperature changes (as much as 50 degrees C) the aluminum rims were problematic with air. Went to N2 and service problems seemed to disappear. My car is equipped with tire inflation warnings. Every little bit of under or over inflation can add to the lifetime cost, so N2 is worth it in my opinion.}

As far as I know, oxigen molucules are so small that it leaks through tyres...to my mind filling a tyre with nitrogen is a waste of money. Even if you pump tyres with nitrogen, the tyre had normal air in it before you let the N in....so the tyre will not be filled fully by N.

When fitting a tyre, over inflate it with 20%....that 20% oxygen will leak out in a month or two and then most of the air in the tyre will be nitrogen. [See why a tyre loose pressure when pumped with air?]

I'm right even if I'm wrong aint I?

Jurie

Interesting post.

20% over filling might be more than the pressure recommended as a maximum when loaded by the vehicle manufacturer, BUT, the theory is good as far as I can tell.

If as you say basically only the Oxygen leaks out (from only some tyres as far as I can tell, not all!), then over say a period of a year, occasional checks with topping up with air will eventually only leave Nitrogen in the tyre at almost no cost to the owner.....

I have never ever had a Nitrogen fill, but as I never ever use cheap tyres (though I get them at trade prices due to a friend of mine), I have never seen the need.....

I just remembered, a Mazda 323 I bought about 1976 DID lose air once I had the original tubed tyres replaced with tubeless. It was assumed by the tyre replacement company to be a wheel problem, rather than a tyre problem. I simply bought a canister of tyre reseal/refill for when you get a puncture, shot a bit of that in each and every tyre (one can divided by 4) and the problem was fixed forever.

And as my ex drove the car and replaced the tyres several times over several years, (before she was my ex) with Tubeless tyres, I have always assumed that the wheels were the problem, but a 100% guarantee is not given....l

But nitrogen molecules are small as well! Atomic mass of N₂ is 14, of O₂ it's 16, so in theory N₂ should leak quicker, though I doubt there's a noticeable difference in practice.

Here a Google image link for Non Pneumatic tires. Looks like there making in roads.

Yenra no air tire.

Thats it! Too easy! Anyone with experience on this?

Seems there was some military research for this.

You are going to leave the ground with every revolution when you get back up to speed, if you get bogged & half the space fills up with mud.

The latest on airless tires can be found at http://www.caranddriver.com/features/tech-dept-the-latest-on-the-airless-tire-and-wheel-combo-tech-dept

There are no D.O.T approved non-pneumatic tires for highway use available on the market yet. What you see in those pictures are development and experimental only. You can get similar types for forklifts and some off-road only vehicles but regular passenger car versions are about 10 yrs away.

Google will find anything you ask it to...doesn't mean it's available or even real.

This from Yenra.

Amerityre's no-air passenger car tire had passed standards testing. The non-pneumatic tire, made from a proprietary polyurethane elastomer compound, has been developed by Amerityre for prospective use as a temporary/spare tire for compact to mid-size vehicles.

"This is a major breakthrough in tire technology," said Richard Steinke of Amerityre. "Over the past several years, a lot of companies have attempted to make a non-pneumatic tire for passenger vehicles. Those attempts fell short, in large part, because they didn't have the compounds to do it. To the best of our knowledge, we are the first company to have a tire that completely meets the standard," he added.

Amerityre has focused its development of the no-air tire technology initially on spare tires for small and mid-size vehicles (tires that carry a load up to 1,250 lbs) because those tires comprise a significant portion of the temporary/spare marketplace. For 2005, small and mid-size passenger car production worldwide is estimated to be approximately 20 million units, with a corresponding number of temporary/spare tires required.

With the successful testing achieved, Amerityre intends to initiate discussions with the automobile manufacturers about making the product available to their customers as an original equipment temporary/spare tire. In addition, Amerityre will continue testing prototype designs of the temporary/spare tire for full-size vehicles, light truck and SUV applications.

Amerityre believes the newly developed tires will provide consumers with a more reliable temporary/spare tire. "Drivers won't need to worry about losing air pressure in these tires. They will always be ready in the event of a flat tire," said Steinke.

April 27, 2005

That's from 2005 and Amerityre still has nothing on the market for passenger car use at highway speeds that's D.O.T approved. Like I said...10 years at least before you can actually buy any of this technology for your car. There's some availability now for off-highway, industrial, and recreational vehichles.

Here a link for DOT.

§571.129 Standard No. 129; New non-pneumatic tires for passenger cars.

YouTube link.

another YouTube link.

I believe the tire companies will come out with a spare tire design for the autos. Military development will offshoot into the aftermarket off road tires. Then at some point you will start seeing them on the roads. It also looks like DOT has some design requirements in play now. Polaris could be coming out soon with an airless tire.

It may not be quite correct to post about "Run-Flat" (subsequently only called "RF" here) tyres (and the required suspension changes) are in use on BMW and some other cars for some years now, but they do need air for normal usage as well.....

But they are fitted to millions of cars nowadays.....

I can only say that BMWs with worn but legal RF Tyres are bad news to drive fast with on even dry autobahns. I would even say dangerous, directional stability is awful. If you drive legally, say in the USA, you may never notice these problems. I drive at sometimes 240 KMH (almost 150MPH) fully legally here, I notice such problems.....

So you must either replace only half worn RF tyres with new ones (expensive), or just use standard (far cheaper here) tyres of the correct size and type and enjoy the car to its full potential for mmore kilometer/miles per tyre set!

I apologise for posting if anyone here thinks that these tyres have no place here, but they are probably the most installed alternative to normal tyres on new cars that can run without air...

For at least the last 5 years, Corvettes have been factory equipped with run flat (RF) tires. These tires require pressurized gas to function properly. The run flat feature is only intended to be used for short low speed trips to the tire store to have the punctured tire replaced. The car owner is cautioned against attempting to use a punctured RF tire as a normal road tire. An imprtant feature of RF tires is that one does not need to carry a spare. This provides extra interior space in a small car like a Corvette

I knew this would come up as I did a little research in Run Flats before posting my question. But since these are still inflateable tires I do not consider those a pneumatic replacement.

Then you must wait an estimated 10 years or so (estimated by someone else here).........Your choice.

Well, will keep on pumping!

As posted by others here, if you buy quality tyres and rims (mine are all OEM), there is very little need to pump.

I check my tyres optically each time I drive, I have a good eye I believe and they get checked with a pressure gauge before each long drive, rarely do they need any extra air....maybe once a year a small amount.....I do run them at the max load pressure for my car which reduces roll resistance, reduces tyre wear therefore giving them a far longer lifespan....

Anyone buying cheap stuff must do much more and I do believe that cheap tyres and rims actually cost more over say 5 years than quality ones. They certainly have a far shorter life span mileage wise.....OK if you do not use your car much maybe.....but not for me....

If there were a tryre (TIRE) that would do all of these things well. The racing industry would be testing and using them.

Assuming that the other technology are still a long time in the future, Run Flat appears to be the best current option, though expensive.....and I believe, not all cars can be fitted with it.....

Other similar systems need special wheels, Run Flats use normal wheels, which will reduce costs a bit....

For more information about RF Tyres, I found this website:-

http://www.bridgestone.com/sc/runflat-system/technology/

Best of luck.

Do you have a problem with foam filled tires?

In a pneumatic tyre, the load gets evenly distributed by the air inside all across the inner surface which is not possible with foam.

Interesting point!

Interesting concept but I was unable to find out whether it is "Road Legal" in some countries (not that a Policeman will be able to judge that on the road without using a knife!!!)

If it is road legal, has it got speed/load restrictions and does it warm up with long journeys at high speed?

Also, will customs and excise assume that a user is smuggling drugs over borders and state boundaries? Losing a tyre or two in the middle of the night to a DEA man on the Mexican/US border will be most annoying!!!! Who will find new ones? Who will pay for them (they appear to search and damage cars on the TV progs and do nothing to help the motorist further, nasty boys Customs!)?

Lots of negatives I feel......

Also, do these "filled" tyres ever need topping up or is this a one time fill that never needs "touching" in any way shape or form?

I personally accept the negative side of modern air filled tyres because I know I am getting the best road holding and braking under most conditions, whereas RF Tyres are simply not as good in terms of ride or roadholding (except when new), price and life.

Most punctures (I have had four in almost 50 years of driving) are repairable if in the tread area, most are in my experience.

So I don't get worried personally (I always carry a spare tyre!) as air filled tyres are long lasting, give a comfortable ride and more affordable.

Also the technology is understood in just about every country around the world, especially the ones I visit from time to time with Caravan and car.......plus Wife and Weimaraner!

Oh, I agree. Not really good for high speed...certainly not autobahn speeds, not now, and not likely in the future. But there was one which struck my eye...it was a tread mounted on a single stiff sidewall...very light and open. but that might have been a concept tire. Can't seem to find it again on google.

The OP wanted to know if there was a tire different from air filled tires... foam filled are different!

Foam filled tires are not going to be high speed for a dozen perfectly good reasons, and they will not be used on the highway anytime soon! But they are perfectly good for low speed applications. Lawn tractor foam filled tires are already in the aftermarket stores here, so they DO exist! (I have to get one of those...my lawn tractor tires are flat in the garage right now! Long winter just sitting there!) Foam filled spare tires are a fine idea...if you consider the purpose of a "spare" tire is to get you off the highway to a garage, even if you have to go fairly slowly to do so. I myself have had the spare blow on me inside of 10 kilometers! And more times than I can count, I have found my spare to be low, or even flat. Out of sight, out of mind! Personally, I always wondered why nobody ever built a coil spring to fit into the tire to prevent it from going really flat.

However, the question of "high speed tires". Well, what do you mean by "high speed" Certainly commuting down town here in Ottawa is not by ANY stretch of the imagination "high speed". And what about bicycles? They can go pretty fast! A bicycle is a superb commuter vehicle, when it works! According to this fellow the expense and slightly slower commute resulting from foam filled tires were more than worth it to not be late for work. It ended up being much less expensive in the long haul because he was not replacing tires every month or two, the tire was actually lighter than a comparable tire and tube assembly, especially considering you don't need that easily stolen pump and patch kit. Most reviews stress that the ride is a "little" harder, but not much, that the expense was high, but in the long run less due to fewer replacement tubes, but MUCH more reliable. I remember once getting a flat tire a good 6 miles away from home....a not bad ride on a bike, but a drag when walking along side one so I sympathize. (in fairness, he DID point out that the ride was harsher...and might be a little harder on the frame and your body...so some suspension might be in order. Some people's bikes are really engineered down to the bone, and they won't like foam filled tires! This fellow didn't!)

But we may see structural tires in a few years...those are tires which...how to describe it... they would be tread rings supported by sidewalls that flex like air cushions. But they are not air cushions. Bicycle tires are built this way now, and winning races now! Where the winners go, the rest of us follow.

Another type uses nanotubes flexing and rebounding....providing a very springy ride. Seems needlessly complicated, but, hey, thats just my sour grapes for not thinking of it first. This might well be the future of tires.

There seem to be many solid tires with holes in them. This one....which is in service, Bridgestone's concept tire (very pretty!) the ERW company's production tires (they hold some crucial patents) Military tires go where civilian tires follow. Michelin's Tweel Tire. I don't know why these things are not being used. Any ideas? Is the pneumatic tire like the qwerty keyboard...just too widespread to allow for improvement?

So all in all, a very good topic.

Foam filled tyres are used for extreme loads at relatively low speed only. We use them all the time on heavy equipment. It also makes the tyre puncture proof. You can't drive on them at highway speed due to heat build up.

I think most of it comes down to what you pay for. You buy a cheap tire you get a cheap tire that doesn't perform well or hold air well.

I have aluminum rims on almost all of my vehicles and rarely have ever put air in them unless I had something stuck through the tire causing a leak or had a valve stem go bad.

Then again I have strong suspicions that it may be because the tires I buy are towards the top end of the price and durability range not at the bottom. I have ran two sets of tires over 110,000 miles before needing to replace them in my life and both sets typically went several years between needing any air added.

I think one set made it the whole way without ever getting flat or needing repair too!

That's what I know about the differences between a $50 - $75 tire and a $200 - $300+ tire.

In my younger years I used to buy the cheapest tires I could find. I got used to seeing treadwear mileage only around 30k miles. Lately, I've shopped around to find tires that give longer treadwear and better traction. Tirerack.com is great for comparing tires even if I don't buy through the site. I'll spend a little more but the results have been great. 45-50k miles and they still have plenty of tread.

Another suggestion is to rotate the tires regularly.

As for aluminum rims, I'll second tcmtech's experience, I've had three cars with stock alloy rims and have never had an issue that I could attribute to the rims.

You wrote:-

Another suggestion is to rotate the tires regularly.

Has to be done carefully nowadays, many tyres (here at least in Europe) are made to rotate (as in spinning round while being driven) only in one direction, so you may only change them from front to back ON THE SAME SIDE OF THE VEHICLE!

Everyone must "read" the sidewall carefully.

PUTTING THEM ON THE WRONG WAY ROUND CAN CAUSE EARLY AQUAPLANING AND POSSIBLE LOSS OF CONTROL.

It's still a great way to even out wear.

BUT, rotation can mean that you replace 4 tyres at the same time, when without rotation, only the driven wheels may need to be changed first.....a question of money for some people 2 against 4.......

If replacing drive tyres on rwd, suggest front tyres go to rear and new tyres on front. Drive with caution first couple of thousand km.

A front tyre blowout is usually more serious than rear - keeping new (lowest miles) on front should reduce chance of front tyre blowout. AFAIK.

Grateful for any 'informed' opinion!

I have only had two blowouts, both at the rear, the car needed heavy steering control to keep it (both times) on a 2 lane highway. It used the complete two lanes each time, swerving all over the place. I did not risk braking as recommended......but still very scary.

I am reliably informed that a front tyre blowout is more easily controlled as you have the steering on those wheels.....though some don't agree and I can say only that I can understand that a front blowout as it only pulls to one side, still scary, is still easier to control, but I have had no personal experience, .....

I looked quickly on the web and found here:-

http://www.nzta.govt.nz/resources/roadcode/about-driving/tips-for-handling-driving-emergencies.html

This info:-

Tyre blowouts

Tyre blowouts can be dangerous, especially if you are driving fast, because they can cause your vehicle to lose control.

A front-tyre blowout will usually cause the vehicle to 'pull' towards the side with the blowout. A rear-tyre blowout will usually cause the vehicle to sway from side to side.

You can try to avoid having a blowout by checking your tyres regularly. It's important to have correct tyre pressure. If a tyre has a large cut or bulge, or is very worn, it needs to be replaced.

If you do have a blowout while driving, you should:

• grip the steering wheel tightly
• ease off the accelerator
• try to keep the vehicle on its path
• signal and steer to the side of the road once you've reduced speed.

Similar tips can be found here:-

http://www.smartdriving.co.uk/Driving/Driving_emergencies/blowout.htm

Do remember that usually you don't have a choice as to which one actually blows......front or back.....

My gut feeling is that a rear blowout would be more stable than a front. (but I could be wrong, I was wrong once before - to paraphrase my ex F.I.L. ;-)

This vid appears to support your position Andy - but not for weak stomachs -

http://www.youtube.com/watch?v=rSVu5fetGDI

Can anybody make out which (or if any) tyre blew?)

That is the perfect example of a rear tyre blowout and the subsequent loss of stability. You don't dare brake and getting the speed off safely is very difficult.....You can see that it was the RH rear tyre that deflated.

Probably it was so horrific because it looked to be overloaded as well, but even without overloading, they are still enough to freeze your blood.

I thank you kind Sir for the video post.

PS.Someone looks like they died there under that vehicle.....terrible.....

If the tyre was even slightly under inflated AND it had heated up with driving, any tyre can suddenly burst, another reason I keep mine on the maximum allowed pressure and when loaded, I check tyre temperatures with the back of my hand. Warmer than my blood and more air goes in.......works well.

Many forget, tyre blowouts are usually as a result of overloading and/or under inflation. Its a killer.

The it would seem that the argument for run flat tyres is blowouts? Do run flats maintain stability in a blowout?

Last time I had a catastrophic blow out on the highway, it was at 100 kmh, in fairly dense traffic. I slammed on the brakes very hard, but not skidding hard. This lifted the back wheels off enough that the car did not squirrel all over the road. When we were almost stopped, I took it over to the shoulder of the road. This last caused the rim to be damaged beyond repair, but I didn't care since by then we were almost stopped.

It was the only way I could think of at the time to prevent the fishtailing that was threatening to throw us into on coming traffic. It seemed to have worked.

Wow, great post. Well done.

I am guessing, but was it a rear end blow out (Fishtailing!)?......

Yes, it was the right rear tire. I am not sure if it was the "approved" thing to do...braking hard like that...but it seemed to work at the time. It straightened me out instantly. When I eased off briefly, I started to drift, so I kept on braking. Not "emergency stop" braking, but "keep the front end diving" braking. Hard but not skidding. It was the only blow out I ever had on the highway in...what...50 years of driving! Usually my flat tires happen in the driveway. I had two extra people, big people, in the back, and that no doubt contributed to the stability....

Its not like you have any time to think when something like this happens.

To add insult to injury, the "doughut" spare blew ten kilometers later. At least that was on a much slower back road. (Don't ask me my opinions of teensy little doughut spare tires! The spare is too often overlooked in these days of (mostly) ultra reliable tires. From this incident comes my interest in an airless spare... This was not so long ago, but there were no cell phones in the car, and Murphy's law dictated it happened along on a stretch of highway which can only be found in Canada. No habitation within 25 kilometers! (Between Gananoque and Malloytown. for Canadians who know! Just took a look at it on Google Earth, and it looks pretty lonely even now!)

Interesting post, thanks (Again )

Just a guess, you put the spare on the rear, with hindsight, it might have been better on the front, where if it deflated, control would have been easier and it might even have been less stressed....who knows?

Also many tyres nowadays have inside/outside on the wall, so with that type you can put them on either side of the car, but you can't reverse them on the wheel.

I thought unidirectional was less to do with tread pattern than the way the tyre's made, it might come apart if going the wrong way, but I could be wrong. The only one I've had was on a full-size steel wheel from a breaker I bought to replace the "space-saver" (ie money-saver) spare provided. The tyre was a Linglow from China, who I'd never heard of, so I asked on CR4 if anybody knew them, and got some scathing comments! I didn't notice any difference driving it, but as it wasn't strictly suitable as a spare I fitted it and tried to wear it out. It did about 20k miles and still looked the same as when I got it. I changed it for an ordinary tyre as I'd got tired of trying, and the wheel didn't match the 3 alloys.

Tyres fitted wrongly that are directional will aquaplan very, very early when it rains as they will force the water to the middle of the tyre instead of forcing it to the outside edges and getting rid of it...

I looked around on the web and found the following:-

Rib shape:- As the name implies the design of this pattern is like a rib shape with the grooves running from the centre to the edges like a rib pattern. The pattern aids faster water drainage and hence gives good traction on wet roads. This pattern is commonly found on most tyres and in today's high speed driving is suitable for all car types. The disadvantage of this type of design is that it is rotational pattern meaning the direction has to be set when mounting the tyre. A tyre mounted on the left can not be mounted on the right, you have to actually demount the tyre from the rim and swap in the inside to face the outside to set the direction right.

with this picture:-

you can read it firsthand here:-

http://www.ctyres.co.uk/tyre_info/tyretreaddesign.html

I hope this post fully explains the problems and advantages of this type of tyre, I love them! Once you have had them, you don't want to change to anything else.....