Another Shraeder/Presta question, briefly

Discussion in 'Cycling Equipment' started by tripp013, Mar 31, 2006.

  1. hd reynolds

    hd reynolds New Member

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    Inconclusive groucho. Your argument is always flawed. Millions of hi pres bike tires are sold per year and an incident like that does not point to anything.
     


  2. tripp013

    tripp013 New Member

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    OK. Went out and bought two 700 Presta tubes at $8.00 per tube. The result? BOTH tubes are now history. The first time around, I had a pump with a cheap Presta adapter that was clinging to the valve. When I pulled it off, the tube ripped right at the valve. SECOND time around: got the air pressure to 80 (out of 120 max) and POP. Ripped about an inch long hole on the OPPOSITE side of the valve (the side that makes contact with the tire itself). Checked the tire and tube; no burrs that I can see, and besides, all was well before I ripped a hole in the tube that started this whole mess.

    Anyone got any more suggestions before I go completely insane from bike withdrawal? How about some affordable tubeless tires? Anything???
     
  3. fish156

    fish156 New Member

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    Hmmmm, there are several issues in play here. First, $8 for a tube is outrageous. You should be able to get them for $5, or less. I would avoid any retailer charging that much. Next (and please don't get me wrong), it sounds like it might be a good idea for you to have someone show you how to change a tube. When I am dealing with a new person to fix their bike, the first thing I ask them is "Can you fix a flat tire?"
    And, by this, I mean:
    Can you remove and reinstall a front and rear wheel?
    Can you remove a tire and reinstall it?
    Can you remove a tube, patch it, and reinstall it?

    My mailman was telling me that he brings his bike to the LBS anytime he gets a rear flat because he does not know how to "get the rear wheel off and back on again". He is not an unusual story. Fixing a flat is not an intuitive process and it's not necessarily something that you can learn by reading about it. There is no shame in getting a lesson on how to correctly and easily accomplish this most basic of all maintenance tasks. The local LBS has a one hour lesson (free!) twice a month to teach this basic.

    Not a month goes by on this forum where someone does not show up with basic problems about how to mount a tube, tire, and just getting it pumped up to pressure. I strongly recommend finding someone to show you how to do this. Ask your LBS if they will show you. If they won't, find another LBS (also, one that does not charge $8 for a tube - yikes!).
     
  4. tyler12

    tyler12 New Member

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    Am I missing something guys? Its all about Standard vs. Metric. 1 inch is equal to 2.54 cm. 1 cm is equal to 10 mm. 700 mm/10=70 cm. 70 cm / 2.54 = 27.56 inches. I think this explanation makes alot more sense, don't you?
     
  5. hd reynolds

    hd reynolds New Member

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    The original post was - can he use schraeder tube specc'd for a 27x1 tire in place of a presta tube 700x18/25?
    It is plausible because 27" tube will fit a 700c (27.56" if converted to English) and 1" equates to 2.54cm or 25.4mm. These inner tubes are flexible enuf to fit those dimensions no problem. But the trick is in the valve coz his rims are presta fittings and he must open up the hole to accommodate the schreader which is larger in diameter.

    On a different note, I agree with fish156 that $8 is way too much coz I pay only $1.75 for 700c chen shin tubes. Also the valve tube hole can be a bain of frustration and a source of countless flats for hi pressure tires. Even a slightly sharp edge on this hole can cut a tube.
     
  6. Al R 1955

    Al R 1955 New Member

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    I have had the occasional hole develop where the valve stem is moulded to the tube,maybe caused when pushing/ pulling as I am inserting/ removing the tube or wriggling a little when pumping or maybe the edge of the hole in the rim.

    Regarless of the cause I make a washer, from an old tube,which I place over the valve stem. Now, I never insert a tube without the washer in place. Simple insurance which costs nothing. I put a nick for the washer hole which streches firmly over the valve.
     
  7. fish156

    fish156 New Member

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    Yes, tyler12, you ARE missing something. It's NOT about standard vs. metric in a lot of cases. Please don't get me wrong. I am not picking on you or anything of the sort. Your question is classic and there IS a very good reason for asking it. If you take a few minutes and read the Sheldon Brown article that I referred to earlier, he explains why (for example):

    (26x1.75) DOES NOT EQUAL (26x1 3/4), as far as bicycle tires are concerned.

    Unless you grew up in the bicycle business, you will never understand some of the quirks of bicycle measurements without referring to some of the articles written by those who "know". Sheldon Brown's site is loaded with sage advice about cycling's oddities. If it were as simple as "standard vs. metric" then why do are just about all new bikes all metric, except, of course for the bottom brackets and headsets, and head tubes? Why aren't they just all metric? It's a perplexing and often confusing issue of legacies. Tires are amongst the most confusing of all (lack of consistent) measurement standards. Fortunately, Sheldon has taken pity on people that have not made the mistakes enough times to learn the hard way and has published a very nice compilation of what tire size markings really mean. Here's the link again:

    http://www.sheldonbrown.com/tire_sizing.html

    I can tell you, from personal experience, that the example I used above does not work. I was helping a friend with his bike and he says "I need a new tire". So, we go off to Wallyworld and get him a 26 x 1 3/4" tire. Well, we fought that damn thing for an hour and could not get it on his 26 x 1.50" rim (you should always be able to go a size, or two bigger with the tire, right?). In this case, it was not a "metric vs. English" issue, but a "decimal vs. fractional" issue. Arrrgh!!! Now, thanks to Sheldon Brown, I understand why this does not work.

    If you want to understand bikes, sometimes you have to just accept the fact that things don't necessarily make sense and refer to the experts. Life gets easier once you do.
     
  8. Retro Grouch

    Retro Grouch New Member

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    Now you've gone and done it! I'm about to be taken to task by the evil Presta valve police again.

    Schrader valves are much easier to inflate than Presta valves. With a Schrader valve, at least if you have a compressor, you just push the air hose against the valve and it inflates. With a Presta valve you have to push the air chuck over the valve. That requires a little bit of technique and a feel for not abusing the base of the valve stem too much. Otherwise it tears at the base as you have found out. The pump chucks aren't all the same either so you have to refine your technique depending on what you have to work with.

    Drilling out your rim to accept a Schrader valve may be a solution, but it comes with its own perils. First of all, you are removing material which may weaken the rim so I don't like to drill out narrow road rims. Secondly, if you decide to do it, you have to do a workmanlike job. Make sure you don't leave any burrs or sharp edges.

    The other technique issue that you have discovered is the same whether Schrader or Presta. When replacing a tire with a new tube onto the rim, you have to be very careful not to let any part of the tube get caught between the tire bead and the rim. If you do, the air pressure will blow that part of the tire off of the rim and ruin your brand new tube. It helps if you put just enough air into the tube to give it shape before trying to remount the tire.
     
  9. tripp013

    tripp013 New Member

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    This much I know too well. The third tube now that I've blown was due to the pump and the valve. The pump chuck holds on to that damn valve like it was welded on. The only way I could get it off after inflating was to pull so hard the tube ripped at the valve. Not so for Shrader. Even now that I've gotten a new Presta tube on successfully, I still have to hold onto the base of the valve and pull the chuck off, usually ripping my knuckles on spokes and gears when the chuck finally releases the valve, to prevent it from ripping the tube (and yes, I remembered unlock the chuck in case anyone's wondering. . .lol)

    I finally got a pro to put the tube in; he says the rims are a bit out of whack, but I can get away with it for now, but to check out new rims in the near future.
     
  10. heavy

    heavy New Member

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    An old bike wrench once advised me to keep the nut on the presta stem between the rim and the tube. That eliminated the possibility of pulling out the stem. Seemed counter- intuitive, and I like the nut on the outside so the valve doesn't push in when I'm inflating the tire. My compromise is to be very cautious when disengaging the pump chuck. I flip the lever to release the air pressure in the chuck, then remove it carefully. If the chuck or head still clings tenaciously, grab the stem below and hang on while you rock the chuck off. Then either hog out the head or apply a bit of silicone grease to relax the hold a bit.

    Maybe the solution is to take an extra stem nut off an old tube, and use them on both sides of the wheel. Meanwhile, we have lots of thorns in these parts, so I buy in bulk from my LBS. Ten std tubes cost me $25 or $27.
     
  11. alienator

    alienator Well-Known Member

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    You might be pushing the pump chuck on too far. Still, to be safe you can line the valve hole, in the rim, with tape to be sure that's not the source of your problem. File the edge of the valve hole, on the inside of the rim, if you like. However, if you're blowing tubes by pulling the chuck off it sounds like either your pushing the chuck on too far or you've got OACRS: Over-Agressive Chuck Remover Syndrome.

    Get some new tubes, swallow a bit of pride, and ask an LBS wrench to show you where you're going wrong. Everyone's new to something at somepoint, so asking for help is not a bad thing.;)

    And for God's sake, find some place else to buy tubes: you're paying at least 2x more than you should be.

    JUST ADDED: are you using that damned nut on the valve stem? If so, STOP!!!!! Way too often people put those nuts on screw 'em down way too tight and end up damaging the tube. You don't need that nut.
     
  12. tripp013

    tripp013 New Member

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    Haha! As far as the tube prices are concerned, friggin' a. Way high. I'll order online from now on.

    If by "nut" you mean the valve adapters, then no, I'm not using those.
     
  13. alienator

    alienator Well-Known Member

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    No. Presta tubes come with a round nut that spins down the stem to secure against the rim. People way too often tighten these nuts too tight. The nuts aren't even necessary, as evidenced by Michelin tubes which don't even have threads for a nut.
     
  14. tripp013

    tripp013 New Member

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    Ah! Gotcha. OK, I'll give it a try.
     
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