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Old 05-12-14, 10:18 AM   #1
FenderTL5
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Q: What happens if you screw the plastic cap on a presta valve..

Question: What happens if you screw the plastic cap on a presta valve without closing the stem completely?
Has anyone done this?
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Old 05-12-14, 10:20 AM   #2
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If you have carbon rims they will asplode.
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Old 05-12-14, 10:35 AM   #3
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Nope, they're not carbon rims (whew!!!) they're Bontrager Nebula 32-hole rims
I'm Just looking for a possible explanation for a weird occurrence. This crossed my mind as a possibility.
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Old 05-12-14, 10:54 AM   #4
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Nope, they're not carbon rims (whew!!!) they're Bontrager Nebula 32-hole rims
I'm Just looking for a possible explanation for a weird occurrence. This crossed my mind as a possibility.
weird occurrences are often supernatural in cause
so i would contact a priest or shaman who has experience with bicycles and pressure vessels
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Old 05-12-14, 11:00 AM   #5
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Nope, they're not carbon rims (whew!!!) they're Bontrager Nebula 32-hole rims
I'm Just looking for a possible explanation for a weird occurrence. This crossed my mind as a possibility.
Bontrager is just code for Trek so even if they're not carbon they'll likely asplode. Just be safe and throw that little plastic cap away!
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Old 05-12-14, 11:02 AM   #6
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weird occurrences are often supernatural in cause
so i would contact a priest or shaman who has experience with bicycles and pressure vessels
Agreed!
I think my garage is a natural habitat for bike gnomes, who like to mess with bicycles when no one is around and/or the lights are out.
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Old 05-12-14, 11:05 AM   #7
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Bontrager is just code for Trek so even if they're not carbon they'll likely asplode. Just be safe and throw that little plastic cap away!
It's hard to tell if you're serious.. how would the rim explode? The pressure point for the air doesn't change. It would still be coming out of the valve. I think it could blow the little plastic cap off.. possibly?
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Old 05-12-14, 11:09 AM   #8
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It's hard to tell if you're serious.. how would the rim explode? The pressure point for the air doesn't change. It would still be coming out of the valve. I think it could blow the little plastic cap off.. possibly?
i am sure rpk79 would never joke about the ongoing scourge of
asploding carbon rims
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Old 05-12-14, 11:10 AM   #9
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It's hard to tell if you're serious.. how would the rim explode? The pressure point for the air doesn't change. It would still be coming out of the valve. I think it could blow the little plastic cap off.. possibly?
It's physics. Don't worry though so long as you don't have crabon fibber wheels and you replace your trek rims you won't have to worry about asplosions.
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Old 05-12-14, 11:13 AM   #10
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i am sure rpk79 would never joke about the ongoing scourge of
asploding carbon rims
Never. It's serious business.



This was caused by leaving the valve open and putting a plastic cap on.
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Old 05-12-14, 11:19 AM   #11
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I suppose it's possible the cap could depress the valve and let out the air.
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Old 05-12-14, 11:21 AM   #12
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Quote:
Originally Posted by FenderTL5 View Post
Question: What happens if you screw the plastic cap on a presta valve without closing the stem completely?
Has anyone done this?
Try it and see. Depending on clearance, it is possible the cap would push down & release air. The manufacturer should make the caps tall enough to prevent it, but who knows ?
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Old 05-12-14, 11:23 AM   #13
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Try it and see. Depending on clearance, it is possible the cap would push down & release air. The manufacturer should make the caps tall enough to prevent it, but who knows ?
Wear safety glasses though.
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Old 05-12-14, 11:40 AM   #14
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Quote:
Originally Posted by J.C. Koto View Post
I suppose it's possible the cap could depress the valve and let out the air.
Quote:
Originally Posted by Homebrew01 View Post
Try it and see. Depending on clearance, it is possible the cap would push down & release air. The manufacturer should make the caps tall enough to prevent it, but who knows ?
This what I'm thinking happened. Tire was at half pressure (50lbs +/-) and the plastic cap gone. I'm thinking it released air until the cap finally launched.
Possible, you think?
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Old 05-12-14, 11:45 AM   #15
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Now that you know the evils of the plastic cap, you can pump up your tire without it and see what happens.
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Old 05-12-14, 12:44 PM   #16
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Quote:
Originally Posted by FenderTL5 View Post
Question: What happens if you screw the plastic cap on a presta valve without closing the stem completely?
Has anyone done this?
Quote:
Originally Posted by J.C. Koto View Post
I suppose it's possible the cap could depress the valve and let out the air.
I've done this on my rear tire. My tire went flat. That is all.

Pumped it up the next morning and it was fine.
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Old 05-12-14, 08:49 PM   #17
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Quote:
Originally Posted by FenderTL5 View Post
Question: What happens if you screw the plastic cap on a presta valve without closing the stem completely?
Has anyone done this?
Can't say I ever have, myself. Mainly because of what I do with the stupid thing the minute I take a new tube out of the box.
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Old 05-12-14, 09:06 PM   #18
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Now that you know the evils of the plastic cap, you can pump up your tire without it and see what happens.
I guess I've been left behind, again. I always pump up my tires with the cap off.
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Old 05-12-14, 09:12 PM   #19
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Never. It's serious business.



This was caused by leaving the valve open and putting a plastic cap on.
nonsense!

it's obvious that the front wheel is in quicksand.
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Old 05-13-14, 05:20 AM   #20
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Just a point of information. The plastic cap's only purpose is to protect the valve from puncturing the tube during shipping and while it's in storage It looks good on our bikes but once the tube is installed, the valve cap serves no purpose and is not necessary.
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Old 05-13-14, 06:11 AM   #21
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Never. It's serious business.


I've done that before when I droped the hammer and cranked it up to 300 watts. Drove the front wheel 6 inches into the pavement. It had to be jackhammered out.
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Old 05-13-14, 07:48 AM   #22
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Originally Posted by RPK79 View Post
Never. It's serious business.



This was caused by leaving the valve open and putting a plastic cap on.

Heeey... That rim didn't asplode; it just went flat.

I think Koto has the correct answer.
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Old 05-13-14, 07:54 AM   #23
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Heeey... That rim didn't asplode; it just went flat.

It's a classic snake-bite puncture.
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Old 05-13-14, 08:50 AM   #24
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the other half went pan-dimensional ..
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Old 05-13-14, 09:21 AM   #25
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Never. It's serious business.



This was caused by leaving the valve open and putting a plastic cap on.

This accident wouldn't have happened if the rider wasn't using clipless pedals!

/I'm a jerk!
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