A friend mentioned that traveling with your disc brake bike on a plane may cause air gaps and need bleeding. I had not heard that.
Anyone experience this of gave knowledge one way or another? Thanks!
Your friend has lost his mind.
Nope. Travelled with hydraulic brakes for years without issue.
I was just watching a video on Youtube yesterday about this. They said when traveling, take off the rotors. I think it was GCN or GTN
maybe about traveling on planes with disc brake bikes.
Thanks. I figured if it were a thing I would have heard about it.
A friend mentioned that traveling with your disc brake bike on a plane may cause air gaps and need bleeding. I had not heard that.
Anyone experience this of gave knowledge one way or another? Thanks!
I have no real experience with hydraulic brakes but I’ll give you an opinion anyway.
The most important characteristic of hydraulic fluid is that it remain essentially incompressible.
So I can’t see how variations in pressure within normal operational range could be a problem.
The hold of an airliner is maintained at a pressure equivalent to atmospheric pressure at an altitude of 2400m (8000ft) or less. If that’s low enough to allow hydraulic fluid contained in brake lines to become a problem by boiling or some such, then I’m glad I wasn’t using hydraulic brakes descending off Col du Galibier.
I can’t see any reason travel in an airplane would cause air in your brake lines unless it’s caused by something you did to the brake system while packing the bike for transit.
A friend mentioned that traveling with your disc brake bike on a plane may cause air gaps and need bleeding. I had not heard that.
Anyone experience this of gave knowledge one way or another? Thanks!
I have no real experience with hydraulic brakes but I’ll give you an opinion anyway.
The most important characteristic of hydraulic fluid is that it remain essentially incompressible.
So I can’t see how variations in pressure within normal operational range could be a problem.
The hold of an airliner is maintained at a pressure equivalent to atmospheric pressure at an altitude of 2400m (8000ft) or less. If that’s low enough to allow hydraulic fluid contained in brake lines to become a problem by boiling or some such, then I’m glad I wasn’t using hydraulic brakes descending off Col du Galibier.
I can’t see any reason travel in an airplane would cause air in your brake lines unless it’s caused by something you did to the brake system while packing the bike for transit.
Are you certain that the cargo area is pressurized? my understanding was that only the passenger cabin was pressurized and that it was not equivalent to sea level pressure.
the so called air gaps could be due to degassing of the fluid, if the cargo area is not pressurized. If the fluid contained air dissolved in it at sea level then went to 30,000 ft the air that was dissolved would bubble out. However upon returning to sea level again most if not all of the air would dissolve back into solution. Any air that did not dissolve back into solution would do so quickly once pressure was applied. I don’t see this as a real problem, more an urban myth? This is similar to the bends in diving and why they pressurize the victim back to depth pressure so that the air bubbles go back into solution then gradually depressurize to allow the gas to come out of solution more slowly therefore avoiding the bubbles forming.
I have a P5 w the magura brakes and I’ve read that before. Some people traveling to races would get air in the lines.
It makes sense this could happen. Hydraulic oil contains dissolved air. Seems like there can be quite a bit of it actually, up to 10%, or so I’ve read. You can easily see this when you pump it in a syringe, block the tip with your finger then pull a vacuum with the plunger. I do that all the time to pull as much air out of the oil before I put new fluid in the system.
Based on the mention above the cargo haul of a plane can reach the equivalent of 2400m, that’s around a 4 psi vacuum from sea level.
The surrounding vacuum is pulling on the system’s pistons. The lever piston is normally fully retracted so the vacuum would normally pull from the caliper piston, just like the syringe example above. This would effectively be closing the brake, ever so slightly. It seems to me one way to prevent it would be to lock the caliper piston, so add a shim between pads and rotor. The GCN advice doesn’t make sense to me.
So yes, this could happen if the fluid had a lot of dissolved air to start with.
Yes, 110% sure the cargo area on a passenger jet is pressurized.
But like someone said, it’s not pressurized to sea level, it’s pressurized to 8000ft.
A friend mentioned that traveling with your disc brake bike on a plane may cause air gaps and need bleeding. I had not heard that.
Anyone experience this of gave knowledge one way or another? Thanks!
I have no real experience with hydraulic brakes but I’ll give you an opinion anyway.
The most important characteristic of hydraulic fluid is that it remain essentially incompressible.
So I can’t see how variations in pressure within normal operational range could be a problem.
The hold of an airliner is maintained at a pressure equivalent to atmospheric pressure at an altitude of 2400m (8000ft) or less. If that’s low enough to allow hydraulic fluid contained in brake lines to become a problem by boiling or some such, then I’m glad I wasn’t using hydraulic brakes descending off Col du Galibier.
I can’t see any reason travel in an airplane would cause air in your brake lines unless it’s caused by something you did to the brake system while packing the bike for transit.
Are you certain that the cargo area is pressurized? my understanding was that only the passenger cabin was pressurized and that it was not equivalent to sea level pressure.
the so called air gaps could be due to degassing of the fluid, if the cargo area is not pressurized. If the fluid contained air dissolved in it at sea level then went to 30,000 ft the air that was dissolved would bubble out. However upon returning to sea level again most if not all of the air would dissolve back into solution. Any air that did not dissolve back into solution would do so quickly once pressure was applied. I don’t see this as a real problem, more an urban myth? This is similar to the bends in diving and why they pressurize the victim back to depth pressure so that the air bubbles go back into solution then gradually depressurize to allow the gas to come out of solution more slowly therefore avoiding the bubbles forming.
The cargo hold is pressurised. From a structural perspective it would be counterproductive to pressurise only the passenger and crew areas. A cylindrical fuselage is a far stronger pressure vessel than if you were to insert a bulkhead between the cargo hold and the inhabited space. Also, if it weren’t pressurised, it would make it impossible to carry pets in the cargo hold (and keep them alive at 10km+ altitude) and you would likely have much more difficulty with sealed containers in people’s baggage too.
Airliner fuselages are maintained at or above a pressure equivalent to atmospheric at 2400m (8000ft). That would be around 75kPa. People can manage just fine (usually) at this pressure, when not doing anything energetic, so it’s considered a good compromise between comfort and performance. Aircraft are not pressurised to sea level atmospheric pressure (approx 101kPa) because it the fuselage would have to be stronger and thus heavier and the aircraft would be giving up significant payload capacity/fuel efficiency/performance. This is why you feel a pressure change via your ears when taking off and landing, but don’t notice altitude changes when you’re already cruising above 2400m or so.
My biggest concern when traveling with discs is getting the disc bent. As someone already noted it is best practice to remove the disc when possible to avoid them getting bent. For center lock rotors its not ideal that you have to take an additional special tool with you but riding around on a bent disc really sucks.
I have no doubt there will have been instances where leaky hydraulic seals have leaked a bit more due to the changes in pressure. A worn seal may just start leaking for a similar reason but this is really a general maintenance/wear and tear things. If perfectly good seals failed with any regularity you would definitely know about it.
My biggest concern when traveling with discs is getting the disc bent. As someone already noted it is best practice to remove the disc when possible to avoid them getting bent. For center lock rotors its not ideal that you have to take an additional special tool with you but riding around on a bent disc really sucks.
I have no doubt there will have been instances where leaky hydraulic seals have leaked a bit more due to the changes in pressure. A worn seal may just start leaking for a similar reason but this is really a general maintenance/wear and tear things. If perfectly good seals failed with any regularity you would definitely know about it.
I leave my discs on. Too much of a pain to remove and install again.
I have an EVOC bag and the discs sit between two plastic pillars that generally keep the rotors from bending.
Only my last trip in July one of them went slightly out of true.
I used my adjustable spanner (aka crescent wrench I also use for pedals) with a piece of facial tissue to prevent metal to metal contact and trued it easily.
I should probably buy a disc truing tool though.
I have a P5 w the magura brakes and I’ve read that before. Some people traveling to races would get air in the lines.
It makes sense this could happen. Hydraulic oil contains dissolved air. Seems like there can be quite a bit of it actually, up to 10%, or so I’ve read. You can easily see this when you pump it in a syringe, block the tip with your finger then pull a vacuum with the plunger. I do that all the time to pull as much air out of the oil before I put new fluid in the system.
Based on the mention above the cargo haul of a plane can reach the equivalent of 2400m, that’s around a 4 psi vacuum from sea level.
The surrounding vacuum is pulling on the system’s pistons. The lever piston is normally fully retracted so the vacuum would normally pull from the caliper piston, just like the syringe example above. This would effectively be closing the brake, ever so slightly. It seems to me one way to prevent it would be to lock the caliper piston, so add a shim between pads and rotor. The GCN advice doesn’t make sense to me.
So yes, this could happen if the fluid had a lot of dissolved air to start with.
i was on a plane with my P5, hydraulic brakes, several times. never any issue.
i only apply the neoprene disc brakes protections and thats it
on a BikeBoxAlan triathlon version
My biggest concern when traveling with discs is getting the disc bent. As someone already noted it is best practice to remove the disc when possible to avoid them getting bent. For center lock rotors its not ideal that you have to take an additional special tool with you but riding around on a bent disc really sucks.
My disc rotor looked like a taco when i shipped my bike with bikeflights. It was my own fault since i packed the bike myself and didn’t take the rotor off. Thankfully it was on the way home from the race and not on the way to the race. I will gladly take my rotors off from now on and bring a lockring tool with me.