I stored (laid-up) my bike in Poland for 6 months last year. On my return I naturally wanted to check the tyre pressures before the ‘off’ .. in a westerly direction.

When I was digging-out my little electric pump from under the seat, an old-timer at the storage depot gestured to me, as much as to say "No Problem .. no problem", and with that he reeled out the hose from his firm's compressor .. pointed quizzically at the inflator's nozzle gauge with a enquiring look on his face. He couldn’t speak a word of English btw, let alone count numbers in English.

I needed 35 psi in the rear - and 30 psi in the front - and therefore flashed all my fingers+thumbs three time (30) plus again with one hand (5), thinking that this was clearly indicating to him the number 35 [psi].

Trouble is, my Polish friend interpreted this signal to mean 3.5 Bars!

So off I went, not with 35 psi in the rear but with 3.5 Bars, or over 50 psi.
[And 43 psi in the front.]

I know .. I know, should have checked with my own pressure gauge afterwards just to be sure. But I didn’t.

Do you know what? I travelled for more than 2,000 km before checking my tyre pressures again .. and then realised the earlier misunderstanding and mistake. And yet, to me, there was no discernible difference between 35 and 50 psi in the rear – and, in the case of the front: 30 psi (2 Bars) and 43 psi (3 Bars).

--------------------------

On the other hand, of course, I have clearly noticed – as have we all, no doubt - that there is definitely a different feel to a bike's handling when your tyre inflations are significantly lower than the recommended pressures.

--------------------------

Moral of the Story: Do what Ted et al said, as it doesn't matter hugely if your apparent tyre pressures go up or down a little bit with altitude. Ultimately, providing you have enough pressure at the bottom of the tyre .. then it won’t look flat!

__________________
Right Way Round ...

You must have been gliding over the tarmac.


When new bikes were delivered to dealerships, they're inflated to this pressure. They don't set them before posting them off from the factory.

If I'd forget to adjust them, I'd test ride at 60 PSI.

And usually I'd not notice. Even when giving it some beans.

__________________
Did some trips.
Rode some bikes.
Fix them for a living.
Can't say anymore.

I've noticed on some bikes it can be more difficult to "feel" tire pressure differences, especially if just plodding down a straight, dry road on an unfamiliar bike.

But on MOST of my bikes ... I can feel even a 3 to 5 PSI change. My DR650 (Ohlins shock, Race tech forks) is quite sensitive to tire pressure changes. Ride and bump absorption can be harsh if over inflated, and unstable/squirmy if under inflated.

An over inflated front tire can be QUITE dangerous, especially if pushing a bit hard on a twisty WET road on a fully loaded bike. Beware. Also, under hard braking you're more likely to lock up and slide if tires are over inflated and cold.

Under inflation is more obvious .... IF you're well tuned into your bike via "Seat of the Pants" method. Trust your gut, if something does not feel right, check it out!

Just a thought, would it be fair to say that a great percentage of riding at altitude is done on less than perfect roads. If so would one not have lowered pressure anyway?

__________________
Regards Tim

Learning my craft for the big stuff, it won't be long now and it's not that far anyway

Ideally, yes. But plenty of room for variation depending on BIKE weight, luggage weight, pace ... and of course the road itself. How bad is bad? Off road I really prefer to run lower pressures ... but if you go to fast and hit something ... bad news. My last Baja Trip ... riding at night on a remote off road track I hit something ... No flat, not problem, never even knew it happened until next day.

This pic from earlier trip on same road. At night it was a bit crazy but not all that bad. My problem was I was going too fast.


So running low pressures can come with risks in terms of keeping your wheels safe. Go too low ... you risk bungered up wheels .. or worse, broken wheel.

Go too high and you get a horrible, harsh ride and poor traction and even worse control. I go with LOW pressures and just try to be careful.

With all 3 you can have some fun in the global warming debate.

__________________
Dave

As the graph shows, atmospheric pressure at 4,000m is roughly 0.6 of the sea level pressure of 14.7 psi, so if you filled your tires to 30 psi at sea level, the gauge reading at 4,000m would be 30psi + (0.4 x 14.7 psi) = 35.8 psi. Not enough to burst a tire, but plenty to see on a tire gauge.


Think of it this way, if you took your bike to outer space, zero atm, your gauge reading would be one atm (14.7 psi) higher than the sea level reading. That is the most that an altitude change can affect your tires. The change is not a percentage of the initial pressure, but a percentage of the loss of atmospheric pressure. if you started with 100 psi sea level, at 4,000m, you would have 100 + (.4 x 14.7) or 105.8 psi.

__________________
Andy Tiegs
https://new.horizonsunlimited.com/ts...lsouth-america

That's really interesting - thanks all the for responses.

"In 4.000 metres attitude the difference of the pressure will be just 0.600 Bars, or in PSI +/-0.8 so means that a tire at an average of 28 PSI could be 1 PSI more or less, up or down….

Javier...
Dakar Motos


“El mejor remedio para la Boludez, es la Inteligencia…”"


Seems Boludezes rule

In my younger days I did the tyre pressure thing when I was racing, how on different tracks at different altitudes how heat in tyre rise to extreme temperatures so scrubbing rubber, cooking your tyres,,,,,,I can tell you that every thing you read is true it is about all those thing mentioned,
but really come on in the would of touring don't worry it's really not that important, you will know what your bike is doing on Tarmac and on soft ground, in any case you will not be going fast enough to make any serious changes,,,,
As ted said ride your bike and don't get involved in a load of bull.
There is guys much more experienced on here than me that will tell you what tyres and inner tubes to use but I think the same answer will be by most its up to you what you are happy with, as regards pressure guide lines are road 30-40,,,,, off road 15-25,,,,, but it's like every thing m8 it's a guide.

Unlike me I just keep my pressures the same road or off road as its not a race

Totally, I'm riding a 250 around Latin America, I couldn't care less about minor performance quirks. It was just that after coming down in altitude my rear was flat the next day, so it got me thinking how much air pressure can affect tires. That was it really.

I've never suffered from pressure loss,,,,well I don't think I have,,, I don't know if northern Italy qualifies as the same sort of altitude you have done,
It would be interesting to know what your tyre pressure was before you went up and what your pressure was when you come down, did you have a cap on the valve

Could be several things, as discussed in this thread. Could even be someone let air out of your tire? (kids?)
Twice, while traveling in France, had folk flatten my tires because they did not like where I'd parked the bike. (parked it for security). So they let air out. This happened to some of our guys in Mexico as well (vandalism in that case).

But could also be temperature and moisture in air. All affect PSI readings more so than Altitude. Riding hard with loaded bike for hours will raise pressures. Once things cool, PSI drops right off. Learn to do COLD and HOT checks to determine the differential between the two. In my experience moist air in tube has a BAD affect on pressure readings.

Molly thought the same, could have been kids or something. I think the tire was probably low already at altitude but it was dead flat, so maybe it was something else. Valve was definitely capped.