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Blackburn Chamber Tubeless Pump use question

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Blackburn Chamber Tubeless Pump use question

Old 03-22-21, 10:44 AM
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pbass
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Blackburn Chamber Tubeless Pump use question

Waiting on some new tires and about to do my first tubeless tire install on my gravel bike (LBS did it previously). I have one of these Blackburn Chamber pumps:

https://www.blackburndesign.com/p/ch...ke-floor-pump/

How do I determine how far to load up the chamber for my tires (max psi 45) when seating the bead? Do I just max it out to 160psi and let 'er rip? Or is it possible to overdo it?
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Old 03-22-21, 01:24 PM
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For a fat bike, you can probably just load it up to whatever is comfortable pumping it up to. The pressure will go down when it expands to the volume of the tire. I'd go to at least to about 120psi to give it a good chance of succeeding.
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Old 03-22-21, 01:35 PM
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Originally Posted by gsa103 View Post
For a fat bike, you can probably just load it up to whatever is comfortable pumping it up to. The pressure will go down when it expands to the volume of the tire. I'd go to at least to about 120psi to give it a good chance of succeeding.
It's a 650Bx47 gravel bike tire. I just saw a couple videos where people are maxing it out to 160psi - one for a road bike and one for a 29'r MTB. I failed physics so I guess I wasn't getting my head around how the pressure is going to behave with the tire and the pump chamber essentially "sharing" the air space in this case. I guess you can't overdo it!
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Old 03-22-21, 02:52 PM
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Originally Posted by pbass View Post
It's a 650Bx47 gravel bike tire. I just saw a couple videos where people are maxing it out to 160psi - one for a road bike and one for a 29'r MTB. I failed physics so I guess I wasn't getting my head around how the pressure is going to behave with the tire and the pump chamber essentially "sharing" the air space in this case. I guess you can't overdo it!
It's pretty simple. If the tire has the same volume as the air chamber, the new pressure will be half 1/(1+1). If the tire is 2x the volume of the chamber it will be 1/3 the pressure after 1/(1+2). You can basically eyeball it. Additionally, you usually get some losses from seating.
In practice, it's very difficult to overdo, because small tires are usually rated for higher pressure. For example, 650x47 Specialized tires are rated to 65 psi, and likely have a similar diameter as the pump chamber, but twice the length, so twice the volume.
Start by pumping it up to about 100psi and let'er rip. Ideally, you'll wind up with the tires seated and just below your target pressure. If you're still well-below your target pressure, next time you can start higher.

The only real way to screw up is to charge the pump and fire it into a partially inflated tire. If you're inflating an already seated tire, don't charge the pump to more than your target pressure.
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Old 03-22-21, 03:49 PM
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Originally Posted by gsa103 View Post
It's pretty simple. If the tire has the same volume as the air chamber, the new pressure will be half 1/(1+1). If the tire is 2x the volume of the chamber it will be 1/3 the pressure after 1/(1+2). You can basically eyeball it. Additionally, you usually get some losses from seating.
In practice, it's very difficult to overdo, because small tires are usually rated for higher pressure. For example, 650x47 Specialized tires are rated to 65 psi, and likely have a similar diameter as the pump chamber, but twice the length, so twice the volume.
Start by pumping it up to about 100psi and let'er rip. Ideally, you'll wind up with the tires seated and just below your target pressure. If you're still well-below your target pressure, next time you can start higher.

The only real way to screw up is to charge the pump and fire it into a partially inflated tire. If you're inflating an already seated tire, don't charge the pump to more than your target pressure.
Thanks. Good info. And I never use the chamber for regular inflation anyway, I just use the normal pump function.
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Old 03-23-21, 05:30 AM
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Nice looking product!

This is the bit from their site that I like: ...all that air floods the tire, giving it no option but to seal and air up.

No option? In what kind of magical kingdom do they live? I had a tire come partly off the rim just last week, just using a footpump.

Try to avoid standing beside the tire when you let her go, especially if the wheel is not on the bike.
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