airing up with a compressor
 

Hey I have an air compressor under the carport. Right now I have a brass presta adaptor and a mini frame pump. My tires call for 100 psi.

Can I power up the compressor until it hits 90 psi, shut it off, then air up my tires?

Logic says, 90psi is 90psi, so it won't hurt anything and would be perfect. But then again, there may be something I haven't accounted for and will pop my tube and burst my tire.

Air from a compressor is the same as air from a pump. Just make sure the tire is seated properly so you don't accidentally herniate the tube.

if the compressor has a storage tank then yes - you can do that. but one can also inflate tires with a higher pressure tank or device. you just have to remove the connector when you reach the desired pressure. this is airing up tires 101. you might have someone show you how at a local gas station. there's some technique to it.

my compressor has an adjustable regulator and an automatic shutoff. I bought it at Home Depot. it is quite sweet.

The problem is not just the top pressure, it's the high volume of air going in very quickly. That being said bike shops air tires all day long without a problem. When using any high pressure/volume source you just need to air for a second or so at a time, checking seating as you go. If the tire's bead line (raised ridge near the rim) starts to move further away from the rim in one area, deflate the tire and check for seating problems such as tube or rims trip out of place or a tire defect.

The above advice is all good. Air compressors work fine if the tire and tube are seated properly and the pressure is regulated to not exceed the pressure you want.

The only problem with using them is if the tire is not seated correctly. They fill the tire so fast you won't have any warning if it starts to blow off. A hand pump is slow enough that you will have a chance to watch the tire as the pressure increases and stop if something is wrong before the tube ruptures.

I have a similar unit, but mine has a tank, with a 3 gallon capacity. It works fine, too.

I think you may be on to something, though - pressurize it to 90psi with the compressor and hit it a few final licks on the manual pump to get to 100 psi.

Now, I dont go too much by absolute pressures and rarely actually measure the fill... I go by feel and I take it slow. The reasons why are explained above.
But, I'm guessing you are following manufacturers recommendations for the tire and/or bike, and want to be precise?

PS - What I do is just "air it up," a little at a time, until the tires are really hard or haven't popped/herniated, etc. Then I test 'em on the road. If it feels like it aint right, I air it up some more. Repeat as necessary. I'll use a tire guage if I have any doubts... and if I can find one around the shop.
(It aint scientific I know, but thass' kinda how we do things in my part of the South ;) )

Whaddya mean your "tires call for 100 psi"? They talk? Or are you reading the Max PSI tag on the sidewall?

Max PSI is rarely the proper pressure.

It's not that hard to modulate how fast air goes into a tire from a tank or even directly from a compressor even on a low volume road bike tire. And pressure is pressure regardless if it comes from a tank or from your arm sweat. The only part I can see that is a concern is the bit about MAYBE catching a herniating tube before it blows. But even then a quick jab from an air line off the tank will put 10 to 20 psi in the tube and then you can inspect the bead seat for signs of any issues. We do this with a hand pump as well, no? And once you know it's good just go ahead and jam the air chuck onto the stem. The restriction of the stem is enough to ensure that the tire isn't "shocked" in any possible manner. And if you want 100 psi you can get the 100 right from the tank. There's nothing to be gained by topping up with a floor pump.

I guess to some it sounds harsh but I think it's only because we are so used to pampering the tires with a hand or floor pump. But let's not forget that we bash and bang these same tires through potholes and over road debris regularly and they don't cry for mercy. There's nothing at all we can do with a pressure limited air source even at the max pressure that will in any way come close to matching the torture that we give the tires out on the road or trail.

I don't have the 'feel' yet. I just pumped it up with the frame pump until I couldn't push the tire in 'too much' with my thumb.

The bike road fine to me, but if it calls for more pressure and it will roll easier that way then adding more pressure seems smart.


The Bontrager sidewall states 'inflate to 100 psi'. So I thought I should at least try to come close. My last road bike (el cheapo) stated, 40-65psi. So I had a range to go by there.

still, I have no idea what 100 psi feels like so I cant go by that. Just trying to set everything up the right way.