mschwett 

I’ve had a slow leak in my rear tire for a while (-20psi a day) so I decided to put in a new tube. roval alpinist clx rim, specialized turbo cotton 26mm tire. wheel off, tire off, tube out, a little air in the new tube, tube in. tire was pretty easy to get back on the rim with my bare hands. massaged it around, tube definitely down in the channel, put a bit of air, squished it around some more…. But every time I got it towards 40 or 50 psi at least one section of the tire would not be seated quite right, not tucked under the lip and clearly taller. deflate, try again. deflate, try again.

finally gave up and took it to the LBS, they looked at it, plugged in the compressor, POP POP it’s seated at 100psi.

I was leery of pumping it up that high when it wasn’t seated right, but I’m gathering that’s what you do to seat it, and as long as the tube isn’t pinched in there (it wasn’t) it’s safe to do so? so, next time I just wail on it with my floor pump?

Canker

eh not a problem. Only a problem if you they are going way over the max psi. It is more of a problem with tubeless mountain bike tires since they have a much lower max PSI and people use compressors to set them up. They will throw 100psi at them and blow them off the bead getting tubeless goo everywhere.

Andrew R Stewart 

When I see a tire bead sitting high at moderate pressures the last thing ai will do is double the pressure w/o further understanding or look see done.

Not being there I can't say what went on by who but a real common reason for a tire bead to sit too high in a spot is from the tube being caught under the bead. Often simple deflation and minor tire/rim manipulation then reinflation will correct this. To an inexperienced eye watching a pro handle the wheel might not seem like a "repair". BTW was that portion of the bead that wasn't seating properly also right at the valve?

Another seemingly minor difference between using a floor pump and a compressor is how the wheel/tire is being supported. With a floor pump the wheel is generally placed on the floor and the pump's chuck attached. then the pumping is started. With very flexible or loose fitting tires the mere weight of the wheel will push the bottom of the tire deeper into the rim and the top of the tire might also be raised out of the rim a bit. With a compressor the wheel is often hand held while the air chuck is applied. One can also manipulate the tire and valve with the holding hand to keep the valve from being pushed into the rim. This manipulation can help both the valve standing proud enough for the chuck and feel for the valve base being fully "above" the tire's beads. Again this handling while using the compressor can be hard to note if one doesn't know what to look for.

Of course there's always asking the person who just inflated the tire with good tire seating. Did you ask them? Andy

mschwett 

haha, yeah i’ve seen that. 100 isn’t over the max in this case.

yeah, my thinking too - if it’s not right, don’t add more pressure. that said, the tube definitely wasn’t between the tire and the rim; i could clearly see all the way around the gap between the tire bead and the edge of the rim; but no amount of squeezing or massaging the tire was going to “push” the bead down into the lip. i did ask the tech at the shop, she just said “those wheels are sometimes fussy and need more pressure to seat.”

of the 6 or so times i tried, maybe four times there was a high spot at the valve. 4 or 5 times there was one somewhere else. once there was only one, not at the valve.

the whole rim-tire-tube system seems really ******, but i guess people acquire some sort of diffuse experience/knowledge about it that makes it less of a PITA.

Camilo

Was it "too tall" on one side, or just right on that side and too low on the other? That's the way it usually is for me. It's not that the tire bead is not properly in the rim on the "high" area, it's that it is too low in the rim in the "low" area. If that makes sense. I was told early in the game, and have always pumped it up to at least the maximum on the side wall, or a bit above that, to get those low areas to pop up in the rim. Just did it with some tires last night. I think if you search the web for how to deal with this, that is one of the typical suggestions, along with manipulating the bead as you go along.

mschwett 

definitely too tall in localized spots, a couple inches across. too tall by perhaps 3-4mm.

when uninflated, the bead of the tire would sit in the deep trough in the middle of the rim, next to the tube. it can’t be pulled “out” under the hook since there’s nothing to pull it by, or keep it out there - naturally it wants to return to the middle. orange profile doodle below.

for 80% of the circumference, inflating the tube pushed the bead into the correct position, from the orange at-rest position to the correct grey spot under the hook. for a little bit, different spots each time, inflating the tube partially pushed it into the red position.

hitting it to 100psi from a compressor instantly popped it into the correct position…. but it’s not like i could do that roadside with a hand pump. at least i don’t think i could.

SoSmellyAir

Maybe I have been lucky with my wheel, tire, and tube combinations, but I have always managed to seat the tire beads at well below (e.g., 50 PSI) my riding pressure (i.e., 80-90 PSI). I do not ever recall hearing the popping sounds a tire makes to seat the beads beyond 50 PSI. But, as a pressure test before my first ride, I still inflate to 100 PSI, which is well below the respective maximum pressure of the tire and wheel.

Iride01 

Road side with a frame pump you might not get too high a PSI. However with my floor pump, I can get way higher than the 125 PSI my air compressor will put out.

I'm of the opinion you aren't going to hurt the tire itself very much with too high a PSI, but you do risk it blowing off your rim if you don't reduce the PSI to within limits. And if it blows off the rim while you are filling the tire, you better hope your hand isn't right there where it blows off. Hurts like heck, and you'll be wondering briefly if you need an ambulance.

ThermionicScott 

It wouldn't hurt to use a little soapy water on the rim to help things slide into place. Of course, that doesn't help you on the side of the road, either, unless you pack children's bubble toys...

Those of us who have installed tires on old straight-sided steel rims naturally get nervous at the thought of just adding a bit more air to even out a crooked tire. But with good hooked rims, especially tubeless-compatible ones, it seems that the bead that's a little high will reach a point at the hook where its progress slows, and it becomes easier for the incoming air to push the tire into place where it's still low. Those popping sounds that make you jump at first become a reassuring sign that everything is snapping into place.

SoSmellyAir

This applies only to an alloy rim? On a carbon fiber rim, overinflation also risks separating the side wall(s) of the rim from the bed.

Iride01 

I can't say for carbon rims, but for the steel rims and alloy rims including the lower end Mavic Open Pro UST and Open Elite that I've had, I think without a doubt, they'd withstand the pressure. From my experiences most tires 27" and 700C's in the 23 mm range blew off the rims about 150 to 165 PSI. The only thing that didn't survive was the tube.

Did my tires have a shorter life from that after blowing off? Not that I could tell. I have problems believing that carbon rims wouldn't also handle the brief overpressure. But I've never owned carbon rims.

Camilo

When I was in college riding a "10 speed" (mid-70s), my friend who was much larger and fitter than me could get 100lbs with his full-length frame pump. I don't know if he could still. But I was just thinking, what would a large CO2 inflator do? It pops up a tubed flat pretty quickly.