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Old 06-05-10, 05:51 PM   #1
mjoekingz28
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presta valves

First drop bars road bike here, just looked it up...its a Trek 1200 from 1991.

Went to check it out today and could not get the tires to hold air. Bought it anyway ($100).

Got it home and I can get the rear to hold air because it has this brass colored (presta valve?) spring inside. When I touch it it lets air out. I miss schrader valves already......again, why did they invent the presta?

Anyhow, the front has the fitting coming through the rim, but no brass colored flexible looking spring. Can I just drop by the bike shop and pick one up or do I need a special tool to insert it. Maybe it just screws in by hand, but like a schrader it needs a tool to apply force to seat it.

And another one, there was this part that I pulled out, it was essentially a brass colored nut that was on the valve that I cannot get back on (but I see no reason for it) because the presta valve is slightly bent. But Im sure I can get some pliers on it and thread it on if neccessary.

The bike is in pretty good shape but I wont know until I can get that front tire to hold air.
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Old 06-05-10, 05:57 PM   #2
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There are no springs on presta valves. Hard to tell from your description (pics would help) but sounds like you may be better off buying new tubes and reading up on how a presta valve works before installing and inflating the. I was leary of them at first but they are easy to deal with once you understand them.
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Old 06-05-10, 05:58 PM   #3
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Sounds like you need a new tube. No removable parts to a presta valve

http://www.sheldonbrown.com/brandt/presta-schrader.html
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Old 06-05-10, 06:09 PM   #4
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It's fairly common for the valve portion to blow out of presta valves. All you'll see is a hole...They are not repairable.
They are not hard to use; you need a proper pump head of course. Unscrew the little lock ring all the way, give it a little tap to break the seal, and fit the head carefully over the valve.
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Old 06-05-10, 06:30 PM   #5
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.....again, why did they invent the presta?
Because they don't leak air back out when you're pumping them up.
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Old 06-05-10, 06:32 PM   #6
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I was leary of them at first but they are easy to deal with once you understand them.
I hate, hate, HATE them. They are far more prone to accidental damage while airing them up than Schraders.
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Old 06-05-10, 06:48 PM   #7
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I hate, hate, HATE them. They are far more prone to accidental damage while airing them up than Schraders.
How do you damage a stem when pumping up a tire?
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Old 06-05-10, 07:50 PM   #8
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My problem lately is finding tubes locally that don't have stems 2" long!
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Old 06-05-10, 08:05 PM   #9
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Originally Posted by mjoekingz28 View Post
......again, why did they invent the presta?
Because Presta valves are lighter, simpler, and narrower, so the rim can be very light and narrow and not have its strength compromised as much as it would if it were drilled for a Schrader.
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Old 06-05-10, 08:59 PM   #10
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How do you damage a stem when pumping up a tire?
I wish I knew. I only have one bike that has Presta and I'm fixing to sell it so I'm not going to worry about it.
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Old 06-05-10, 09:11 PM   #11
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I haven't damaged a presta tube by inflating it. I have, however, damaged a tube trying to pull the pump head from the valve. Most presta tubes are threaded all the way. I like the stems with no threads. It is easier to remove the pump head without damaging the tube. They are also more aerodynamic, but I am not sure if I could notice that difference.
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Old 06-05-10, 10:16 PM   #12
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I love presta valves...buy decent quality tubes (I get the cheapest ones from Jensonusa.com or Pricepoint.com, they are heavy but durable) and have had ONE valve rip out, entirely my fault for not being more...gentle I have been using them for 9 years now, and only like them more each time. Just push in the valve core first before pumping to break the valve seal so you dont break a pump (I love lifetime warranties on pumps!).

I actually hate schrader valves on bikes now. I have one bike that takes them and it will be given to my dad if he wants it.
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Old 06-05-10, 11:01 PM   #13
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Originally Posted by dedhed View Post
Sounds like you need a new tube. No removable parts to a presta valve

http://www.sheldonbrown.com/brandt/presta-schrader.html
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Originally Posted by Bikewer View Post
It's fairly common for the valve portion to blow out of presta valves. All you'll see is a hole...They are not repairable.
Not true. There are presta valves with replaceable cores, and, they do make the cores for sale.
http://www.biketiresdirect.com/ptuvc...ve_core/pp.htm
http://www.ebikestop.com/kenda_prest...ten-TU6010.php
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Old 06-06-10, 04:16 AM   #14
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I would have gotten you a pic, but I was pumping up the tire and finally got it to work. See I took off the locknut and then it began to pump easier and I got the pressure I wanted. After that I released the pump and I guess it shot out of there because the air rushed out and nothing but a hole there now.

So I thought I just needed two valves, but it seems I need two tubes now.

The spring I was referencing to is I guess the valve core (as it would be on a schrader). I bent it back straight and then the locknut would thread by hand. Now its gone, wonder where it ended up!?
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Old 06-06-10, 06:39 AM   #15
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How do you damage a stem when pumping up a tire?
Poor technique. People can break the valves by sloppy, rushed, overly forceful pumping. (I've used presta for years and I don't think I've ever broken a valve.)
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Old 06-06-10, 08:14 AM   #16
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I have broken a presta stem when using a mini pump. But then again as far as Im concerned mini pumps suck. Two of them broke when I needed them most. I now carry cartridges with an inflator head. Light and reliable.
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Old 06-06-10, 09:03 AM   #17
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Quote:
Originally Posted by mjoekingz28 View Post
I would have gotten you a pic, but I was pumping up the tire and finally got it to work. See I took off the locknut and then it began to pump easier and I got the pressure I wanted. After that I released the pump and I guess it shot out of there because the air rushed out and nothing but a hole there now.

So I thought I just needed two valves, but it seems I need two tubes now.

The spring I was referencing to is I guess the valve core (as it would be on a schrader). I bent it back straight and then the locknut would thread by hand. Now its gone, wonder where it ended up!?
You should never remove the nut at the top of the presta valve. You loosen it until you feel the resistance from it hitting the top of the threads and then fill the tire/tube. When you are done you hand tighten it down, which prevents accidental losing of air. The valve is held closed by air pressure in the tube, no spring involved. It's essentially a plug at the end of the threaded portion. If you remove the locknut the rest may fall into the tube. I would guess that's why you got the rush of air when you released the hose. The pump has it's own check valve that prevents the air coming back out until you release the head.
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Old 06-06-10, 10:49 AM   #18
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Originally Posted by mjoekingz28 View Post

The spring I was referencing to is I guess the valve core (as it would be on a schrader). I bent it back straight and then the locknut would thread by hand. Now its gone, wonder where it ended up!?
Try not to bend the valve core, while sometimes you can straighten them sometimes they break off where the metal's fatigued. Stick with the prestas, they're superior for bikes in a couple of ways. Just need to be more careful when airing up and do things a little differently than with a schrader. What are you using to pump them up with?
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Old 06-06-10, 11:05 AM   #19
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Quote:
Originally Posted by mjoekingz28 View Post
I would have gotten you a pic, but I was pumping up the tire and finally got it to work. See I took off the locknut and then it began to pump easier and I got the pressure I wanted. After that I released the pump and I guess it shot out of there because the air rushed out and nothing but a hole there now.

So I thought I just needed two valves, but it seems I need two tubes now.

The spring I was referencing to is I guess the valve core (as it would be on a schrader). I bent it back straight and then the locknut would thread by hand. Now its gone, wonder where it ended up!?
Bernoulli's principle in action It's inside the tube. The air rushing into the tube as you removed the pump head forced the stem back not the tube. Don't remove the knurled nut as someone else mentioned. Here's a handy, step-by-step guide I've put together for you Presta newbies and Presta abusers

1. Remove the cap and unscrew the knurled nut. You already know not to remove it



2. Burp the valve...just a little...to get it free in the stem



3. Use the small opening on your pump head. If you have a frame pump you may have to make some modifications by turning the grommet around



4. Put the pump head onto the stem and lift the thumb-lock





5. Pump.

6. Remove the pump head




There will be a rush of air but that's just the pump line emptying. You aren't losing air from the tire. The valve closes because the air inside the tube keeps the valve closed. Very simple mechanism.
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Old 06-06-10, 11:16 AM   #20
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Presta's are where it's at. they hold high pressure 10x better than schrader valves. You'll learn to love them.
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Old 06-06-10, 12:24 PM   #21
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I stopped by Walmart early this morning since I was ready to ride and all the shops are closed today. My tires are 23c and the best I could find there was 25-34c so I got two of them and a lever/patch kit all for <$10. All went pretty well. I tucked the tubes the best I could and they've held for 10 miles so far. Just getting the last section of tire back on the rim has my fingers still hurting.

The bike came with a Trek mini/frame pump and even has Trek brand water cages.

Thanks for the tutorial. I finally got most of it figured out ever since it was said that my tubes were crap. I kept expecting something to unscrew in the valve like in a scrader.

Now I have to visit the LBS and get a presta valve air gauge.......or can I use the adapter instead, hmm


thanks guys, Im riding now and feel like a big boy and not some unfortunate soul riding a MTB on the streets. Need to get a computer now to monitor any progress I may make.

Peace


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Old 06-06-10, 03:48 PM   #22
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You need to lean that blue bike over a little more. The rear tire is still new on the sides.
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Old 06-06-10, 11:01 PM   #23
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You need to lean that blue bike over a little more. The rear tire is still new on the sides.
Don't worry dvs. I has just started riding then and that was my first set of new tires coupled with too much chain lube. Granted, I dont have the roads here you do in Socal (palomar, mountain passes, canyon roads) I found a nice 4 lane frontage road that allowed me to get a knee down and eliminate the strips. However, it wasn't with the M1s pictured, it was with some Z6s. YZF600R btw
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Old 06-07-10, 01:24 AM   #24
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Presta's are where it's at. they hold high pressure 10x better than schrader valves. You'll learn to love them.
This is why they use Presta's on 747 tyres and on high psi compressor tanks...

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Old 06-07-10, 01:37 AM   #25
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"again, why did they invent the presta?"

It's smaller diameter works on very narrow rims where increased strength is needed and on some very narrow rims a Shraeder stem would interfere with the tyre bead.
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