Bicycle Mechanics - Flat Inspection

I should get it by now, at least to the extent that I've developed expertise in fixing flats. (I can do it in under 5 minutes front or rear) I never know the cause of my flats, never observe a thing beyond them being flat and the necessity of fixing them - always using a new tube.

Usually my flats are found the next morning or later in the evening - so clearly a leakage rather than an impact/blow out. But from where, I never seem to locate the compromised spot, despite putting them re-inflated under water or using my ear up close.

Then the other day I was starting out, fully inflated, as I pump them to max pressure everyday, a couple blocks away, I hear Psssst and my rear is flat. I didn't hit a bump or ride over a pot hole or anything at all. (the valve was closed) Don't have a clue what happened here.

Later I got another one in front - but after a lot of riding, but still don't know the cause.

I always check the inside of the tire as well as the rim for protrusions. I use good, thick rim tape.

I'm not necessarily complaining that I get flats, or get them too often (Of course I'd rather not!) but I'd like to get better at identifying a cause.

There is a seasonal pattern I've identified, I get more flats in the warmer weather but do not do much more riding than in the winter (I'm a stalwart year round cyclist!)

Probably punctures from glass or thorns and such. If the leak is so slow you only notice it the next day, then you can only find it by inflating the tube until it's 2-3x fatter than the tyre it's designed for. Then submerge it in water and watch closely. Maybe only a 1mm bubble will surface every second or two. With the one you could hear hissing, just pump it up and you'll find it with you ear and eye. Hold it close to your cheek so you can feel the where the air comes from if you can't see the hole.

To solve the mystery, it'll help if you know where exactly the tube was in the tyre
(Line up the valve with the pressure indication or such) and which way it was turned. Then find the hole. See if the the hole faces the rim or the tread. If there are two holes side by side, it's a snakebite (too low pressure+pothole). Inspect the culprit area, pass your fingers along the interior of the tyre.

I have seen very small foreign matter inside tires that will eventually make a small hole in the tube. Don't let the tube touch the ground or the shop floor when you put it all back together. If you see any dust like particles blow them out. Flat tires on a ride are a fact of life but I believe in doing everything I can to minimize the chances, good tires, inspection of the exterior before each ride, scratch out small angular pieces of gravel that may imbed themselves into the tread, rotate front to back (and replace the rear tire) as needed. Some people use a liner (Spin Skins??) between the tube and tire but that is extra rotational weight and I have not seen the need for that much protection. Good Luck.

Don't let the tube touch the ground or the shop floor when you put it all back together.

Good call!

What kind of tires do you run? Schwalbe Marathon Pluses are famous for their protection. I can't remember the last time I got a flat. Oh yeah, I do remember. It was the time I was touring, changed my worn out tire and couldn't get a replacement Mara +. Then I got 5 flats in a week! :mad:

Sounds like you're very proficient at replacing tubes, but if you do it in 5 minutes every time, I'm thinking you're not taking the time to check to make sure the tube isn't pinched under the tire bead.


I usually inflate the tire just one or two pumps, so I can check around the bead to make sure the tube isn't under it. Then I'll either deflate it and fix, or inflate all the way, depending on what my first inpection found.

I used to have to do this with my older bike quite a bit since the trails that I ride have a lot of thorny plants.
Slime solved that problem good and proper and that bike (now my dad's) has been on the same set of tubes for over a year now (running on those same trails).

Having had experienced the blow outs from getting the tube pinched under the tire bead, I do what you do along with pumping the tire up, releasing the pressure than filling it up to max pressure. I've gotten fast, but also pretty thorough, including running the tube through my fingers while applying talc thereby removing any unwanted matter on the tube itself prior to putting it on.

I use Michelin Pro Race tires, currently, but have certainly gotten many flats prior to them with more puncture resistant and wider tires.

It's more that I'd like to be better at determining the cause(s)

I have experienced five flats :( on my last five rides (slow leak). The hole looked the same on every tube, just a tiny puncture on the top of the tube. Took the bike to three shops and they all said "get a new tube". After the last flat (on my way home from Bike to Work, btw), I decided to get new tires instead, Armadillo Elites. Last night I took the old front tire and went through it inch by inch and found a small slender wedge of glass lodged deep in the tread, it was not easy to see. My guess is it was puncturing the tube ever so slightly ! but not showing through to the inside of the tire.

Anyways, I've easily spent $40 on new tubes in the last couple weeks. There's a lot of "stuff" on the roads where I ride so I'll see how the Elites hold up.

Cheers

It's also important to make sure that your valve is properly lined up in the hole--any angle on it, and your rim could be slicing a little hole into the valve stem. I had a problem with a bunch of sudden punctures and I finally realized that my tubes were too big for my tire. Sounds dumb, but even things like that can happen more frequently than you'd think.

And you're using good rim tape, right?

To solve the mystery, it'll help if you know where exactly the tube was in the tyre
(Line up the valve with the pressure indication or such) and which way it was turned. Then find the hole. See if the the hole faces the rim or the tread. If there are two holes side by side, it's a snakebite (too low pressure+pothole). Inspect the culprit area, pass your fingers along the interior of the tyre.

LoFarkas knows what he's talking about. The first thing you do to diagnose flats should happen when you mount the tire (i.e. before any puncture ever occurs). Just about every tire has a colored label on at least one side. When you mount the tire on the rim make sure that this label is centered over the valve hole. Then, when you get a flat you just yank out the tube, inflate it and find the puncture hole. Now, lay the still leaking tube over the tire (using the valve_to_tire_lable relationship to align them to each other) and then you know exactly where on the tire to look for the cause of the puncture.

The next time you look at a bicycling magazine or catalog be sure an notice how all of the valves line up with the tire lables. Any wrench worth his, or her, salt instinctively mounts tires in this manner. Probably the most important part of fixing a puncture is determining what caused it.

This is a little aside, but I have started noticing lately that a lot of people don't pay any attention to the road ahead. I started watching people in the group rides I do and many of them just drive right through bits of broken glass instead of around it. I figured this was just common sense, but I guess not. Obviously, you don't swerve into traffic to avoid a tire hazzard, but by looking at the road surface ahead you can eliminate a lot of punctures. Good group riders will point out the sharps to the riders behind them. May your next ride be flat free ;-)

This is unlikely, but look at it anyway - Where the tire bead starts & stops, there is a small section of overlap. Tire manufacturers seal this with rubber. If the rubber is worn, the wire bead of the tire itself can protrude enough to puncture the tube, eventually. I've had this problem with a pair of Continental tires, but only once. It took the LBS some serious detective work to find the flaw. Maybe worth looking at...

You guy's haven't told me anything I don't already know on this. Says alot about BF, as You BF guys have taught me just about everything I know about bike mechanics!

Thanks!

This last week I had two flats. Both were caused by the rimstrip shifting/deforming enough under the 120-130 psi I run on that bike's IRC Paperlite tires.



I saw an ad for some plugs used to fill the spoke holes, to use in lieu of rimtape. Does anybody have any experience with these sorts of things?

You guy's haven't told me anything I don't already know on this. Says alot about BF, as You BF guys have taught me just about everything I know about bike mechanics!

Thanks!

WTF is this all about? Lofarkes and Orange gave you a couple simple tips that would be helpful to you since you didnt mention every step you take to identify the causes of your repeated flats. BF can't teach you common sense and expirience. Sorry you didnt get the GeeWhiz answer you were lookin for.

You guy's haven't told me anything I don't already know on this. Says alot about BF, as You BF guys have taught me just about everything I know about bike mechanics!

Thanks!
I know this was intended as a compliment to the experts of BF, who have taught me as well. Of course, one problem (for me, anyway) is that knowing and doing are not always the same. From time to time I've had to fix problems that occurred due to my laziness or impatience or inattention, not my ignorance.

How important is it to you to be able to fix a flat in 5 minutes?
I take whatever time is needed to make sure I understand what has caused the problem. I always take the tube home and analyze it thoroughly.
Careful installation is critical.
Velox rim tape goes on all of my rims.
I use ultralite tubes and light weight tires no liners or puncture resistant tires, the performance cost is too great.

Al

WTF is this all about? Lofarkes and Orange gave you a couple simple tips that would be helpful to you since you didnt mention every step you take to identify the causes of your repeated flats. BF can't teach you common sense and expirience. Sorry you didnt get the GeeWhiz answer you were lookin for.

Sorry if my compliment was out of line!

We could go on forever discussing every angle of a flat tire- my problem not being repeated flats, more a curiosity than a problem. I chose to end my involvement with this particular thread with a nice word about you guys and allow more experience to lead to a better sense of this issue.

Lighten the F up and learn to better decipher a good word!

Two things I didn't see.

Are you using new tubes or patched tubes? I've had a problem with slow leaks from the patches, especially the glueless ones.

Are the tubes the proper size for your tire? This is another problem I had I was using 18-20c tubes on 23c tires.

Have you tried running your fingers along the inside of the tire? That's the first thing I do, before I look at the outside. You may get a little prick from the thorn or glass, but you'll find the offending hole-poker.

I'm not going to berate you on this b/c you can do whatever you want, but why don't you patch your tubes? Maybe I'm just cheap, but I get tired of buying new tubes all the time. A mechanic friend of mine once put 20+ patches on a mountain tube just to see how long he could keep a single pair of tubes.

Sorry if my compliment was out of line!

We could go on forever discussing every angle of a flat tire- my problem not being repeated flats, more a curiosity than a problem. I chose to end my involvement with this particular thread with a nice word about you guys and allow more experience to lead to a better sense of this issue.

Lighten the F up and learn to better decipher a good word!

Ooooh riiight, telling these guys you havent learned anything new from them in one phrase, then saying you learn all you know from them is such a backhanded compliment...:) Its all good, tho. Maybe my initial thought upon reading that was a bit kneejerk, but I can't decipher yer "good word" if it appears at 1st, 2nd, and 3rd read to be couched in sarcasm.

I had a problem with a bunch of sudden punctures and I finally realized that my tubes were too big for my tire.

+1 on this. I usually use a tube that's one size smaller than the "rated" size. I have less problems, especially with pinch flats, a real problem on tandems. The way tires are made, some (many?) are undersized anyway. I've yet to have a problem because the tube was too small.

Ooooh riiight, telling these guys you havent learned anything new from them in one phrase, then saying you learn all you know from them is such a backhanded compliment...:) Its all good, tho. Maybe my initial thought upon reading that was a bit kneejerk, but I can't decipher yer "good word" if it appears at 1st, 2nd, and 3rd read to be couched in sarcasm.

Try reading it again, you might get it right on the 4th try! Better yet move on to what you know, bikes and cycling. Leave alone what you don't know, the spirit of my comment and my character.

An easy way to find the source of a flat is to run a dryer sheet (those little pieces of paper you throw in the dryer to elim.static or whatever) around the inside of the tire. They will snag on anything.

Here's an idea... To localize where the flat is, I pull the tire/tube off together and reinflate and listen for the hisses. You can hear escaping air from punctures even on the tire side unless its a really small hole in which case I pull the tube a bit at a time til I find the location of the failure. As for causes, the type of failure is usually readily apparent. Leaving the works together makes this all much easier to line up the tire/tube/rim combo to find what's causing yer headache.

All good info that will serve me (and anyone) well.

Much has been made of my stating proudly my speed of fixing flats ...and I am proud about this recalling the first time I changed a rear flat that took me about an hour and a half, afterwards covered in grease, sweating, bleeding, finally to hop on and blow the tire cause I didn't work out the kinks in the tube. This was after taking way too long learning the function of the presta valve so I can actually pump some air into my tires!

I've come a long way, thanks to you guys... and I do mean that in the best possible way MTK;)