Tyre Sizes

I've just been deliberating the way tyres are measured.


My back tyre is 180-55/17 the 180 is the width in millimetres and the 17 is the rim diameter in inches.

I'm sure this is typical Canberra thinking. I know as I used to be part of it.

Yep that is correct, and the 55 is a % of the tyre width not height in mm/cm or inches. So it is 55% of 180mm = 99mm. Makes sense doesn't it?  

So, what pressure do you run them at?
Psi, Bar or Kpa?

I think metric air (KPa) gives me a much better ride.

BTW I was talking to the local Yamaha dealer prior to buying the CBR650 and he told me that his deal comes with unlimited refills of nitrogen gas as opposed to ait refills for your tyres.

He also told me that nitrogen fills would in all probability not suffer the same pressure loss as does air.

Now, we know that air consists of around 80% nitrogen and 20% oxygen making the molecule larger than the nitrogen atom. As it is larger we should have less loss than nitrogen for a given hole size. How can it be claimed that nitrogen fills will last longer than air.

I think he is talking a whole heap of crap, however, I will accept that nitrogen will result in less corrosion so that may be an advantage.

What say you??

Michelin (who invented the steel belt radial in 1946) tried to change the world and go with a metric wheel-tire combination.  It was not interchangeable with conventional wheels and tires and although technically a much better ride than convential wheels especially with the lower profiles as the sidewalls weren't as stiff, the concept did not take off and was eventually shunned by the car manufacturers.


Note how the Flange is not as deep as a convential rim and is angled out slightly.  The TRD version also included a limited run flat capability.

The only Australian based vehicle it came out on as far as I know was the 1982–1984 Ford FD LTD (the centre "hubcap" of these wheels were dished as opposed to the flat FE model).  They were a 390/55/220 wheel and last I saw were about $2000 a set.  As most FD LTDs are going for $600 with 12 months rego, not too many have the original metric rims on them anymore.



And there is no truth to the rumor metric tyres are not used because tyre fitters can't count up that high - 15" vs 390mm   

On the Nitrogen side of things BD, I've heard a few people talking that have had it in their tyres saying that there was very little pressure loss as compared to air filled tyres

My daughter just bought a 1980s corolla with 50,000km on it some old lady had from new .............and always used nitrogen in the tires , so I Googled it .

                                                                                                                                            http://greggsauto.net/2013/05/6-facts-about-nitrogen-filled-car-tires/
                                                                                                                             


                                                                                                                                            http://www.bankrate.com/brm/news/car-advice/20070714_driving_dollars_tires_nitrogen_a1.asp

Also on the subject of nitrogen in tyres, is that all caravans & camper trailers made by Jayco come with tyres filled with nitrogen, including the spare!

They say that because 'van tyre pressures are neglected by a lot of owners, they do it because the tyres don't loose as much pressure as with air. Also, they don't over heat as much either.

What an interesting debate.

This is a paragraph from Paul's post

6 Facts about Nitrogen Filled Car Tires

1. All aircraft, military, heavy duty vehicle and road equipment are required to use nitrogen in their tires.

2. Nitrogen is a drier, inert gas that does not allow water to form.

3. Nitrogen molecules are larger than the oxygen or atmospheric air making it less likely to leak through rubber.
This statement does not make sense to me. My understanding of chemistry, which could be way off track   is that the Nitrogen atom with an atomic number of 7 and an atomic weight of 14 is smaller than Oxygen atom with an atomic number of 8 and an atomic weight of 16.
As a molecule of air consists of Nitrogen and Oxygen atoms they are heavier than Nitrogen alone.
I also understand that heavier means larger in size and harder to get through a given hole size

IS EVERYBODY STILL AWAKE      


The only way I can understand this is if Nitrogen for use in tyres is not pure but is Nitrogen and something else with a larger atomic weight.


4. Michelin Tire Co. states that tires filled with pure nitrogen loses pressure 30% slower than tires filled with compressed air.

5. Nitrogen is non-corrosive because of its molecular structure.

6. Nitrogen is a cooler gas that reduces the heat generated within the tire, thus keeping the integrity of the rubber in the tires at its best.

I'm keen to try nitrogen to see if I can get to work quicker due to the lower temps.
I Metter put the same amount in each tyre because I don't want the rear getting there 5 minutes before the front. 

If it doesn't work I'll stick with good old fashioned compressed air and checking every week and before each ride because that's what I'd be doing if using nitrogen anyway.

Maybe this explains it Dave

http://periodictable.com/Properties/A/AtomicRadius.v.html

BanditDave wrote:What an interesting debate.



3. Nitrogen molecules are larger than the oxygen or atmospheric air making it less likely to leak through rubber.
This statement does not make sense to me. My understanding of chemistry, which could be way off track   is that the Nitrogen atom with an atomic number of 7 and an atomic weight of 14 is smaller than Oxygen atom with an atomic number of 8 and an atomic weight of 16.
As a molecule of air consists of Nitrogen and Oxygen atoms they are heavier than Nitrogen alone.
I also understand that heavier means larger in size and harder to get through a given hole size

IS EVERYBODY STILL AWAKE      


The only way I can understand this is if Nitrogen for use in tyres is not pure but is Nitrogen and something else with a larger atomic weight.

Just to clear up one misunderstanding, air is not a molecule. Air is just a mixture of gasses, the nitrogen and oxygen are not chemically bonded. Usually they both naturally form molecules of 2 atoms. So O2 and N2 there are also some small amounts of other gasses, I agree, you would think both of these molecules would be a similar size. Oxygen is a much more reactive molecule, I don't know if this is the difference.

Its all a load of bs. I've tried it and it's just a rip off. Bob Jane gave me 4 red dust caps for $8 each. Just use air and a good quality gauge

I think MadMax wins the prize for the most obscure reason yet. Atomic Radius.

I had to look it up and I have to admit it sounds like a plausible explanation.

I can hear Maxwell Smart saying "Of course, the atomic radius of the atom trick"

I'll have to visit my local Yamaha dealer and offer him an apology. Fancy me doubting him when all he was trying to do was expand my knowledge with some understanding of atomic physics.

Can you imagine any other motorcycle forum where atomic physics is discussed?

I think enough has been said about these basic topics. Tomorrow we should extend ourselves to Quantum Mechanics and Special Relativity

Re-Cycled wrote:

BanditDave wrote:What an interesting debate.



3. Nitrogen molecules are larger than the oxygen or atmospheric air making it less likely to leak through rubber.
This statement does not make sense to me. My understanding of chemistry, which could be way off track   is that the Nitrogen atom with an atomic number of 7 and an atomic weight of 14 is smaller than Oxygen atom with an atomic number of 8 and an atomic weight of 16.
As a molecule of air consists of Nitrogen and Oxygen atoms they are heavier than Nitrogen alone.
I also understand that heavier means larger in size and harder to get through a given hole size

IS EVERYBODY STILL AWAKE      


The only way I can understand this is if Nitrogen for use in tyres is not pure but is Nitrogen and something else with a larger atomic weight.

Just to clear up one misunderstanding, air is not a molecule. Air is just a mixture of gasses, the nitrogen and oxygen are not chemically bonded. Usually they both naturally form molecules of 2 atoms. So O2 and N2 there are also some small amounts of other gasses, I agree, you would think both of these molecules would be a similar size. Oxygen is a much more reactive molecule, I don't know if this is the difference.

WOW!!!
If they are not chemically bonded does that mean the smaller atom Nitrogen leaks out leaving behind the Oxygen atom??


Actually, I think I have got it all figured out now.

When they claim to be putting Nitrogen in your tyre they are actually using Nitrous Oxide. That explains the big smile on their faces when they take your money.

2wheelsagain wrote:

If it doesn't work I'll stick with good old fashioned compressed air and checking every week and before each ride because that's what I'd be doing if using nitrogen anyway.

There in is another problem ........I couldn't just leave it  & not check my tyres .......then what about that bit of nitrogen you lose when you check them   

LOL on another point , who prefers tire , & who prefers tyre & where do " YOU " put the cap while you check them  

I always remove the cap when I check them. I tried not doing so once and the gauge would not fit no matter how hard I pushed.  

BanditDave wrote:I always remove the cap when I check them. I tried not doing so once and the gauge would not fit no matter how hard I pushed.  

   

2wheelsagain:

You've misunderstood the principle. Banditdave noted that special relativity applies with nitrogen not general relativity.
Both of your wheels will arrive at work before you leave (and you'll feel more spethial).
The tread depth will increase instead of decreasing. Let us know how many ks you get out of the tyres before they jam inside the mudguards and have to be replaced.

BanditDave wrote:

Re-Cycled wrote:

BanditDave wrote:What an interesting debate.



3. Nitrogen molecules are larger than the oxygen or atmospheric air making it less likely to leak through rubber.
This statement does not make sense to me. My understanding of chemistry, which could be way off track   is that the Nitrogen atom with an atomic number of 7 and an atomic weight of 14 is smaller than Oxygen atom with an atomic number of 8 and an atomic weight of 16.
As a molecule of air consists of Nitrogen and Oxygen atoms they are heavier than Nitrogen alone.
I also understand that heavier means larger in size and harder to get through a given hole size

IS EVERYBODY STILL AWAKE      


The only way I can understand this is if Nitrogen for use in tyres is not pure but is Nitrogen and something else with a larger atomic weight.

Just to clear up one misunderstanding, air is not a molecule. Air is just a mixture of gasses, the nitrogen and oxygen are not chemically bonded. Usually they both naturally form molecules of 2 atoms. So O2 and N2 there are also some small amounts of other gasses, I agree, you would think both of these molecules would be a similar size. Oxygen is a much more reactive molecule, I don't know if this is the difference.

WOW!!!
If they are not chemically bonded does that mean the smaller atom Nitrogen leaks out leaving behind the Oxygen atom??


Actually, I think I have got it all figured out now.

When they claim to be putting Nitrogen in your tyre they are actually using Nitrous Oxide. That explains the big smile on their faces when they take your money.

Well it appears the Oxygen is more massive but smaller in diameter so it would have more momentum to get through a semi-permiable medium.

Personally I think it's for racing but I'll just stick to air for the convenience.

Besides if you keep topping up with air you should eventually end up with Nitrogen in there anyway. (and water) ;(

You guys have not allowed for the copious amounts of moisture that compressed air can contain when you check/inflate your tyres at the servo.!!!

spanna wrote:You guys have not allowed for the copious amounts of moisture that compressed air can contain when you check/inflate your tyres at the servo.!!!

Cause I do it at home       

Yes me too, half the time the servo pressure gauge is inaccurate as well

paul wrote:

spanna wrote:You guys have not allowed for the copious amounts of moisture that compressed air can contain when you check/inflate your tyres at the servo.!!!

Cause I do it at home       

Me too

The last time I ever used servo air was at 7-11, they had one of those automatic "idiot proof" units.
I set the pressure to 38psi plugged her into the front tyre and let it do its thing, didn't notice it actually let air out, it beeped to indicate at pressure so I removed the hose. I didn't do the rear as I was in a hurry as I was riding with a group.
I went to hang a right turn out of the servo and the bike almost went straight, I managed to pull up safely but what a scare.