Bicycle Mechanics - Flat tire virgin can't find culprit!
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04-15-12, 10:08 PM
Sorry for the newbie question, but my wonderful sunday ride was rudely interrupted by my first flat tire, and now i have a couple of questions for you guys:
a.after inspecting my rear flat tire, and not finding any glass and just a couple of marks on the outside of the tire, i continue to remove the tire and the punctured tube - i spent the next 5 minutes looking/feeling for the culprit on the inside and outside of the tire, and couldn't find anything - now i am freaking out, that i will get another flat soon since i couldn't remove a microscopic piece of glass from the tire - FYI, the old tube has a "silver circle" mark around the puncture - does this mean it was some sort of pinch flat?!
b. after inserting my new tube, i REALLY struggled clinching the last 4 inches of the tire back into the wheel - since the tire was wet, i even got blisters on my hand - here is my question: i was taught to "roll" the tire back into the wheel from the side - a good samaritan stopped by, and instead of rolling, he "pinched" the tire (best way that i can describe) and with 2 pinches, the tired snapped into the wheel with no struggle! is there something i am missing here? some secret technique? am i just a whimp?
any help is appreciated - i am also ready to tolerate any abuse due to my "newbie" questions!!! cheers!
04-15-12, 10:28 PM
if you spent 5 minutes feeling around and didn't slice the tip of your finger open, the cause has probably left the building. it's good to be thorough and cautious.
as to question b, I find no shame in using a tire lever. some tires are easier than others and levers aren't needed.
Best way to check the tyre is lay the tube against it as you pump in some air to locate the leak. When you find the leak in the tube, you've narrowed down where to look on the tyre.
As for fitting a tyre...
1. Get one bead on the rim.
2. Lightly inflate the tube (just enough to fill it without stretching it); this makes inserting it easier and prevents it getting pinched under the bead.
3. Push the valve partway in (to prevent its base being caught under the bead) and start getting the other bead on the rim from the valve area.
4. When it starts getting tough to continue, deflate the tube, and you may need to pinch the bead together around the rim in order to get it loose enough (most rims are smaller in the centre). You may also need to stand on the rim and pull up on the tyre to loosen the bead.
5. It should now be possible to force in the rest of the bead with your thumbs. Any tyre that doesn't respond to all these tricks and still requires a tyre lever (unless you're female) is a PITA and should probably be burnt in disgust as an offering to the gods of fine tolerances.
That last doesn't really apply to getting the tyre off, but I can still get most decent tyres off the rim without a lever... you just need to do what it takes to loosen the bead. Then put the heel of your hand against the side of the tyre, grip it with your fingers and press the tyre against the rim, twisting the tyre to stretch the bead over it. As you maintain the pressure, it should be possible to make more of the bead rest on top of the rim until you can pop a section of it over. Then you're home free.
04-16-12, 12:07 AM
+1 I always carry a spare tube but try to repair the old tube first. After feeling around for the object that caused the flat (about 50% of time it's already gone), I inflate the tube and to find the hole. Once I do I hold it up to the tire and rim to see where the object that flattened the tube, punctured the tire (at this point, since I already know where the hole in the tube is, I usually just patch it). After re-checking the area of the wheel that lines up with the hole in the tube, I just put the tube back in. Learning how to R&R (Remove and Re-install) a tire without levers just takes experience; sometimes it's an issue with the rim that makes the tire hard to mount, sometimes it's the tire and sometime both. I push the bead of the tire with my thumbs as I pinch the top of the tire and roll it away from me with my fingers. Mount the tire a little at a time; 5-10mm at a time. New wire bead tires are the most difficult to mount and rims with tall sidewalls like Sun rims also make the job more difficult.
As far as your puncture, I'm guessing the rim liner is not covering a spoke hole and the tube pressure pushed it into the hole (leaving a round impression) and punctured the tube, possibly with a protruding spoke..I'd advise you remove the tire again and make sure the liner is covering all the spoke holes. You'll also find that the more you R&R a tire, the more it gets stretched out and it easier it is to R&R;
As far as your puncture, I'm guessing the rim liner is not covering a spoke hole and the tube pressure pushed it into the hole (leaving a round impression) and punctured the tube, possibly with a protruding spoke.
04-17-12, 10:40 AM
thanks for the help/advice everyone! looked at some youtube videos, and apparently leaving the area closest to the valve to clinch last didn't help the situation - the wet tire i am sure didn't help either!
I am waiting for the blisters to heal before giving it another go at R&R to check the protruding spoke theory - (while changing the tire, it seemed to be pretty thoroughly placed at the rim, although i did not check the rim liner throughout ); i did have to true the wheel myself a few weeks ago since the LBS quoted me 4 weeks for the job, so although i was very careful adjusting the spokes tension, i wonder if i could've done something wrong at that time!!
also, looking at the punctured tube again last night, the puncture was aligend to the outside of the tube (opposite to the valve) - does that negate the protruding spoke theory or can the tube rotate as it is inserted into the tire?
gotta a group ride tonight so i might find out the hard way, but took the bike for a quick ride last night to test it out and the tire is still inflated - hope it's all in my head!
It is a good practice to always put the tyre on the rim in the same position (always align the same marking from the sidewall of tyre with the valve). Also always install the tubes in the same way (usually there are some markings on the tube). By following this rules, after you find the puncture in the tube, you will know where to check the tyre for the foreign object which caused that puncture.
Also check all around the tyre, just in case there are other sharp objects inserted in the tyre, but not yet deep enough to puncture the tube.
04-17-12, 04:00 PM
Ive had the Continental Gatorskins for 5 years now and not a single flat. Touchwood!!!!
04-20-12, 12:28 PM
update: went on a couple of longer rides and the tire is holding up alright (knock on wood!) - i've also read that my michelin krylions are known for being tough to install (lots of threads and/reviews include adventures similar to mine); next time will carefully use a lever if i encounter too much resistance!
next time i do get a flat, i will make sure to inspect the strip on the rim to make sure it is not a spoke, but since the puncture was on the opposite side of the valve, i am thinking i am good (for now!)
thnks again for all the input -
04-20-12, 12:42 PM
Common causes of punctures and the location to check for them:
Puncture on bottom/side of tube---foreign object.
Puncture on top of tube (ie, valve side)---inadequate or worn rim tape.
"Snake bite"----pinch flat---not enough tire pressure.
04-20-12, 05:43 PM
Yeah, at least half the time I can't find what caused the flat (I figure there are times when something pierces the tire and then, for a number of reasons, doesn't attach or continue with the tire to be found later) ...other times I begin to see a pattern and what was not immediately obvious becomes apparent, like a tire just wearing thin and having small holes in it or (I should have found this immediately but I wasn't expecting it in a Marathon Plus tire) a wire protruding inside the tire (I would repair and pump up the tire and it held air for a ride but the the tube would slowly leak out the air overnight.
All you can do it inspect everything after a flat (sometimes you might be in a hurry or it might be getting dark etc. so that is going to work against a good inspection) fix it, and see if it stays fixed (and I've found it usually does).
04-20-12, 08:10 PM
I had some Continental Contacts on my road bike. I got three flats in the first 600 miles. I was not happy about it and could not find anything in the tire. All the flats were in the same place on the tube so the same place on the tire. After the third flat, I never got another flat in that place and only had one more flat on those tires for the rest of the tire life. Strange thing but still wonder what caused the flats. The leak was actually pretty fast so I should have been able to find whatever it was but didn't.
Just thought I'd share my flat story.
04-20-12, 08:29 PM
+1 on Kimmo's points.
Key things: inflate the tube slightly before stuffing it in and start at the valve area seating the bead first and partial push the valve in to make sure the bead gets past the thicker tubing that the valve attaches to.
04-21-12, 04:10 PM
thanks for the help/advice everyone! looked at some youtube videos, and apparently leaving the area closest to the valve to clinch last didn't help the situation....
I disagree. I have changed thousands of tires/tubes, and a significant amount of those were before I learned to end near the valve, not on the opposite side. It is indeed much easier to end near the valve. In fact, but using a variation on the install technique I can remove many tires without tools.
You will notice above that one step is to push the beads to the center of the rim well. That can't be done around the valve, so ending at the valve gives you more slack. There is no reason for the valve to intefere with mounting next to it - you just push the stem up into the tire.
04-21-12, 10:56 PM
I'll add a bit more...
Be real careful looking for what may have caused the puncture feeling around with your fingers inside the tire. After a few holes in my fingers, I deecided using a glove was much more comfortable! Cny-bikeman pointed out to have the bead in the CENTER of the rim and not sitting on the outside as you work it over the rim. I found that out mounting motorcycle tires. Even my dad told me you should always put the tire on using your hands. I've never had a tough bicycle tire that I couldnt do this to.
ALWAYS inspect the wheel for potential problems. I have even had rust on a rim puncture a tube.
Work smart so you only do it once!
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