18 replies to this topic

[simplepeachyme]

I'm going on my very first flight next month to vegas. (woop!) I was wondering if I needed to deflate my high pressure tires a bit before boarding the plane? I don't want to meet my chair after the flight and find that the tubes burst because of the pressure. I'll probably bring my travel pump and an extra tube just in case...

thanks!
amanda

[LeahC]

simplepeachyme, on Jan 20 2010, 08:42 PM, said:

I'm going on my very first flight next month to vegas. (woop!) I was wondering if I needed to deflate my high pressure tires a bit before boarding the plane? I don't want to meet my chair after the flight and find that the tubes burst because of the pressure. I'll probably bring my travel pump and an extra tube just in case...

thanks!
amanda

You should take an extra tube and pump anyway but no your tyres won't burst (lol sorry I had to laugh) xxx

[Tinbasher]

I understand where your coming from but aircraft holds are pressurised these days otherwise bottles in baggage would explode and cuddles the poodle would be DOA

Tin

[jass1]

you should deflate your tires a little bit only if the tires at max,the cargo hold is not pressurised except for animals area

[simplepeachyme]

shveet. thanks guys!

[dangerousdave]

To be honest - never thought about it - wheelchair has always been ok

Ops...silly me....I use solids

[Rotarymotion]

dangerousdave, on Jan 21 2010, 11:03 AM, said:

To be honest - never thought about it - wheelchair has always been ok

Ops...silly me....I use solids

Sorry - pressed wrong button. Reply follows in next post.

Edited by Rotarymotion, 21 January 2010 - 08:27 PM.

[Rotarymotion]

This is an interesting question, and the answers are not entirely obvious. In fact high-pressure tyres are likely to suffer less than tyres rated at a much lower pressure.

As has been pointed out, the cargo hold isn't pressurised, and even the passenger cabin is only pressurised to an equivalent height of between 8000' and 10,000' to enable the aircraft fuselage to be made lighter, and thus save fuel and money.

In the worse-case senario, of an aircraft cruising at FL 400 ( about 40,000 feet) the effect of the unpressurised hold will be the same as putting under 15psi extra into your tyres. I pump my tyres up to 130 psi, and they are rated to 145 psi (Schwalbe Marathon Plus) so even at 40,000 feet they are within the tyre limits. The increase in pressure is only about 11 %.

However, many mobility scooter tyres are rated at 20 psi max and the handbook sometimes suggests running at around this pressure. In the same aircraft the effective pressure would now be something approaching 35 psi, which is a percentage increase of 75%, which could cause problems.

So just don't bother pumping up your chair tyres for a week before you fly. I always take two spare tubes with me wherever I go anyway. I believe they ward off punctures !

[edlee]

Excuse me for my ignorance,,, and my high school physics teacher would be ashamed of me,,, but why would the high pressure tires change by 11% but low pressure tires by 75%? .

Since the pressure inside the tires decreases slightly because the tires expand a bit more,, there wouldn't be any problems unless the tire itself popped,, and I don't see that happening.
ed

[jules]

I personally have never let my tyres down prior to a flight, but always travel with 2 spare inner tubes and puncture repair kit just in case.

[Rotarymotion]

edlee, on Jan 22 2010, 08:56 PM, said:

Excuse me for my ignorance,,, and my high school physics teacher would be ashamed of me,,, but why would the high pressure tires change by 11% but low pressure tires by 75%? .

Since the pressure inside the tires decreases slightly because the tires expand a bit more,, there wouldn't be any problems unless the tire itself popped,, and I don't see that happening.
ed

Hi Edlee,

Yes it does sound counter-intuitive at first. I'll see if I can describe it another way....

What you are measuring when you put a tyre gauge on the valve is the difference between the inside pressure of the tyre (say 130 psi for high pressure wheelchair tyre and say, 20 psi for a scooter tyre) and the atmospheric pressure which is roughly 15 psi at sea level (varies from day to day).

Now, take away the atmospheric pressure, ( i.e. consider a vacuum ) and the pressure inside the tyre remains the same unless the tyre can expand, (and the extra expansion available is very small) but the pressure difference between inside and outside has now risen to 130 + 15 psi = 145 psi.

Obviously, even at 40,000 feet in an aircraft hold, there is not a total vacuum, so the 15 psi rise is quoted as a limiting value that won't be exceeded, no matter how high the aircraft (or rocket!) flies.

Now consider the scooter tyre under the same change of conditions; take away the atmosphere outside, and unless the tyre can expand significantly, the pressure difference between inside and outside ( i.e. the force that will stress and possibly burst the tyre ) increases by 15 psi to 35 psi.

20 to 35 is a much larger percentage increase than 130 to 145, even though the pressure values have both increased by the same (15psi).

Hope this helps. I'm not noted for my clear explanations, as you have spotted!

Of course, aircraft take their own tyres with them into the sky. I don't want to put anyone off flying by saying what pressures aircraft tyres use..... but they are much higher than my wheelchair tyres!

NB for other scientists and engineers: I am aware of the second-order effects I have ignored in the above explanation.

[Ches]

Wow the nerds came out for this one.


Hey seriously, my tires get a lil low after a flight.. hardly enough to notice. I did 3 flights in 24 hrs not to long ago and could tell a difference by the third. But if youre doing one round trip it shouldnt matter. If you dont want to take a pump, just look up a local bicycle shop in advance, just in case.

[edlee]

Given what you say about the relative pressures,Rotator,,, I still have a problem believing that either tire is likely to pop. In fact,,, I would think that the high pressure tire is closer to it's structural limits than is the low pressure one mentioned.

As Ches has evidenced,, the only difference the altitude would make is that the natural pressure loss in ANY tire,, however slight that is,, would be only slightly increased. Perhaps a week's loss instead of six days loss.

But the idea of carrying spare tubes when in a place with which you aren't familiar,, is, frankly, a nobrainer. Simply good judgement.
ed

[E-DOG]

No, yer tyres wont burst.
But, if the pilot gets the plane too close to the sun, it could melt them.
If I were you, I'd get in the compartment where the wheelchair is with a bucket of cold water and keep the tyres nice n' wet n' cool for the duration of the flight.
E-dog

[qbounce]

I have these plastic rims called X-CORE that have an occasion to break on planes. So, when I ever get the opportunity to travel, I'll be sure to buy different rims for traveling.

Also, traveling with kick tyres will aleviate all pressure problems.

[WildKat]

simplepeachyme, on Jan 20 2010, 06:12 PM, said:

I'm going on my very first flight next month to vegas. (woop!) I was wondering if I needed to deflate my high pressure tires a bit before boarding the plane? I don't want to meet my chair after the flight and find that the tubes burst because of the pressure. I'll probably bring my travel pump and an extra tube just in case...

thanks!
amanda

I fly quite a bit and I've only had a flat once. My tube was deflated a bit during a stop over, and by the time I was ready to catch my next flight it was completely flat and my tire was almost coming off my rim. My small hand pump was in my luggage so I just took it very easy until we were at the hotel. I pumped it up and never had a problem with it after. I usually make sure my tires aren't inflated fully before flying just in case. instead of 145psi I'll leave around 115-120psi in them. I usually take my small pump and and extra tube along with me too just in case. I wouldn't worry too much about it! Enjoy your trip!

[twisted_ophelia]

Mine have never burst. They will probably deflate, yeah, but if there is an issue (especially if you're traveling to widely traveled place like Vegas), take them right to a bike shop and have them fill them up. Do NOT use the air pump at a gas station. There is actually more risk for a blow-up at the gas station air pumps than anywhere else.

[Beautiful]

Ive flown over 15 times and have never had a problem. I'm flying to Colorado then Georgia next month, and I know it won't be an issue for my tires :], even if it was, I know that the place I am going has the tools I need to make sure my wheels are okay.