Friday, November 27, 2015

Part Three of a Trilogy on Flat Tires: How to prevent those pesky flat tires from happening in the first place!

There are some things that can be done to reduce your chance of getting a flat while out riding.  Some of these will increase your wheel weight slightly, but the amount of time you lose due to the increased wheel weight is much less than the time spent fixing a flat!

One of the first things you can do to stop possible future problems with flat tires is to replace the original plastic rim strip with a quality rim tape such as the one made by Velox.  The original plastic strip is slippery and has no glue so it will tend to slide to the side over time and expose the spoke holes in the rim.  A quality rim tape like Velox or Zefal will have adhesive that will hold it in place.  Just be sure to get the correct width for your rims.  A typical 700C 23/25 tire sits on a wheel that will use a 16mm rim tape.  The tape is easy to install.  If it has a valve stem hole in it, just line that up with the valve stem hole in the rim and start going around the rim.  I used the handle of a pair of pliers to press the tape into the groove of the rim since they were smooth and about the right diameter.  There is some debate as to whether or not to overlap the ends of the tape or butt them together.  Frankly, either way works so long as the butt joint is between spoke holes.  I used the overlap and did it opposite of the valve stem for weight balance across the rim.

Next, you have the option of installing a liner in your existing tire or upgrading your tire to a puncture resistant tire, or both if you live in a particularly bad area for punctures.  The tire my LBS recommends is the Continental Gator Hardshell DuraSkin Folding Tire as being the best tire out there for preventing puncture flats.  It is not the lowest rolling resistance tire.  The Bicycle Rolling Resistance blog has performed testing on various tires, including an earlier version of the Gator Hardshell that showed rolling resistance at 19.3 watts to be significantly higher than the lowest rolling resistance tires such as the Continental Grand Prix 4000 S II at 12.2 watts.  The Grand Prix 4000 S II does have some puncture protection, but its puncture resistance score is 11 vs. the 19 of the Gator Hardshell.  So it is a trade off of puncture resistance for rolling resistance.  For the liners I could find no scientific tests on the increase in rolling resistance, but the general consensus is that the liners do add rolling resistance on the order of 10%.  I will have to do some coasting tests on some local hills to see if I come up with the same conclusions.

Preventing of pinch flats is done by maintaining adequate pressure in your tires.  For most road tires this means 90-110 psi.  You also want to avoid the potholes and sharp curbs.  A wider tire will give better pinch flat resistance as well.  A 25mm tire is better than a 23 mm tire and a 28mm tire is better yet.  You are limited by your rim width and the clearance available at your forks and frame tubes.

Finally, you can use tubes with sealant in them.  The most well known brand for tire sealant is Slime and you can buy the Slime in a bottle or in a Slime pre-filled tube.  Frankly, for Presta valve tubes I prefer the pre-filled tubes as it is much less hassle.  Testing on rolling resistance show minimal impact due to the sealant in the tube.  There is a small weight penalty at the worst place, the outside edge of the wheel where the inertial forces are highest.  But this penalty should be no more than that of a liner or a puncture resistant tire.

So which should you use?  It all depends on your aversion to flats.  If you ride with the Oakdale Bike Shop rides and you have the awesome ride leader Ed along he will change the flat for you!  No problem, you get to rest up from the thrashing you have been receiving while you tube is changed out! Then again if you ride out by yourself or are on a drop ride then you want to minimize those flats.  Do you have goat head thorns like we do, or is it more glass and man-made sharp objects that cause the flats?  Hard to say what the perfect balance is.  For me I will ride with liners and Slime during goat head thorn season (summer in California) but will be looking to pull out the liners, keep the Slime and go to the Continental Grand Prix 4000 S II during the winter for a low rolling resistance combination.

Please comment on this post.  I would love to hear what works for you out there on the roads.  Also, see my related posts on The Causes of Flat Tires and How to Repair Flat Tires.


Monday, November 23, 2015

Part Two of a Trilogy on Flat Tires: Some tips on fixing those pesky flat tires when out on a bike ride!

In my previous post I covered the four main causes of flat tires for road bikes.  In this post I will talk about fixing flat tires.  The best way to fix a flat tire is to get someone else to change it for you!  Just kidding, but that is what happens if you go on group rides with an awesome local bike shop like Oakdale Bike Shop.  Your ride leader can have that tube changed out in a jiffy.  Of course, not every shop has a great ride leader like Ed!  So then, unfortunately, you have to change the tube yourself.

When you have a flat you need to remove the tube.  To do this you will need a tire lever. Some good tire levers are shown in the picture and include ones made by Pedro's, Crank Brothers and Avenir.  There are advantages and disadvantages to each one, but the general favorite/standard is the Pedro's levers.  The Crank Brothers Speedier lever has some features designed to make it more ergonomic and easier to use but it hasn't quite worked out to be easier for me.  Some people swear by the Speedier lever and others swear at them!  Fortunately the levers are cheap and you can find them online or at your local bike shop for very similar prices.

inner tube replacement on your bikeUsing the tire levers to pop the bead of the tire over the rim will make it possible to remove the tube for inspection and repair or replacement.  You may need to pop the tire bead away from the rim by pressing with your thumbs as you go around the rim.  I have to do this with my Giant's rims because the bead locks in place.  On other rims this is not an issue and you can just use the tire lever to pry up the bead over the edge of the rim while being careful to not pinch the tube (if you want to save it) and then slide the tire lever around the rim to bring one side of the tire over the edge.  You can now remove the tube.  I usually start at the valve stem and simply move the tire over so I can slide the valve stem out of the rim.  Don't forget to remove the stem nut if you use one, though according to my weight weenie friends you shouldn't use it because it is just extra weight!

Once the tube is out locate the hole(s) causing the leak.  This is important especially if you don't know what caused the flat.  If you know it was a pinch flat caused by hitting a pothole or you pulled the thorn out of the tire that caused the flat you can skip this part and go straight to replacing the tube.  When you are on a ride it is just quicker to replace the tube with a spare tube and then you don't have to worry about whether the repair will hold.  You can then repair the tube later with a good quality patch kit like the one manufactured by Rema.  If it was not a pinch flat you will want to run your fingers along the inside of the tire before installing the new tube.  Even if you pulled out the thorn, there may be other thorns in the tire ready to puncture that brand new tube 10 minutes down the road!

If the tube failure was caused by a hole in the tire you need to locate the hole in the tire and reinforce it with a tire boot.  For this you can use the official tire boot such as the one by Park Tool, or a thin piece of cardboard or even a dollar bill!  The advantage of the tire boot is that it is adhesive backed so that it will stay in place better than a dollar bill.

Once you have made sure there are no sharp objects still sticking through your tube and taken care of any holes in the tire you are ready to install the new tube you were carrying with you.  First step is to put a little air in the tube to give it some shape.  This will make it much easier to put back into the tire, but it will also reduce the chance that you will have a twist in the tube that could cause it to fail when you inflate it up to pressure (pow!).  Insert the valve stem first and then work your way around the tire sliding the tube into place and working it back onto the rim.  Now it is time to re-seat the tire bead.  You can do this by hand or use the tire lever.  I usually start it by hand and then use the tire lever to finish popping the bead over the rim by sliding the lever around the wheel.

You are now ready to inflate the tube using either a CO2 cartridge powered inflator or a frame pump.  Just take one final look at the tire as it sits on the wheel to make sure the beads are where they belong and there are no funny bulges where the tube is wadded up!  You should begin by partially inflating the tube and checking again to make sure the tube isn't folded inside the tire.  Just last week a fellow rider blew his brand new tube at this point in the replacement because of a kink in the tube. After verifying the tube is not kinked inflate the tire to full pressure and reinstall it on the bike.  You will get faster with experience, but it is better to take the time to do it right rather than have that tube blow out on you a few miles down the road.  Also, see my next blog where I talk about steps you can take to avoid getting the flat in the first place!

Please see my earlier post, Part One of a Trilogy on Flat tires, What Causes Them? for information on the causes of your cycling flat tires,  Thanks for reading, and as always I look forward to your comments.


Tuesday, November 10, 2015

Part One of a Trilogy on Flat tires: First, what causes them. Second,how to fix them. Third, how to prevent them.

There are three givens in life: death, taxes and if you ride a bike....FLATS!  Flat tires never happen at a good time, but the chance of having a flat while cycling can be greatly reduced with some careful attention paid to your bike's wheels, inner tubes and tires.

cycling through thorns causes flat tire due to punctures
So, what causes bicycle tires to go flat?  If you have the tire in the picture to the left it is an obvious answer, but there are at least four distinct types of flat tires.  Each type has its distinct personality and appearance.  Full anointment in the brotherhood of cycling happens when you have had the joy of experiencing them all!

First is the puncture/cut flat, which is the one we think of most often when we think of a flat.  A thorn, a piece of wire, glass or other sharp object on the road punctures or cuts through the tire and inner tube leaving you on the side of the road disassembling your bike so you can fix the flat.  This flat can take some time before it is noticed if the puncture is small, or it can be as long as a day or two before it goes flat.  Sometimes the hole is so small it is hard to find.  I have had to resort to dunking the tube in a bucket of water and watching for air bubbles to find these holes.

cycling rim tape spokes cause flat tiresThe second type, the pinch flat is the scariest flat because it often occurs when you are going fast, there is a loud pop and the tire goes flat immediately!  It happens when you hit a pothole or other sharp edge and the tube gets pinched between this edge and the two side of the rim.  For this reason this flat typically looks like a snake bite on the inner-tube with two punctures spaced apart from each other by the width of the rim.

Another type of flat happens when the rim tape moves over enough to expose one of the spoke holes in the rim.  This one can happen while riding, or even when the bike is just sitting there!  Notice in the picture how the green plastic rim tape has moved over and exposed the hole for the spoke nipple where the screwdriver tip is pointing.  That small amount of spoke hole showing was enough to cause me a flat!  This flat occurs because the rim tape fails to support the tube over the spoke nipple hole and the tube ruptures in a blowout.  It will be a large enough hole that you can't pump the tube backup with a floor pump.  The air will leak out as fast as you pump it in and the hole will be on the rim side of the tube.

The fourth type of flat is related to the cut tire, only this time the tire wall is weakened enough that the tube pokes out through it and ruptures.  This could be caused by a brake pad pivoting and rubbing on the tires sidewall until it gets so thin that it give way, or a piece of glass or metal on the road side. With this type of flat, if you don't have a spare tire you will have to line the tire with something in order to get home.  You can use a section of old inner tube, a large patch, a pre-trimmed piece of thin cardboard, a Park Tool emergency tire boot or a dollar bill placed inside the tire so you can get home.  The Park Tool emergency tire boot takes up very little room in your emergency kit, see below for a link to buy or check with your local bike shop for availability.

What should you carry with you on your ride?  At a minimum you should carry a spare tube, a tire lever and a CO2 inflator.  This can fit in you jersey pocket or in a saddle bag and will be enough to for shorter rides, group rides where people are willing to share, and supported rides that have spare tubes and flat repair as part of the ride service.  If you go out on longer rides by yourself, then you may want to include two tubes, a patch kit and either multiple CO2 cartridges or a frame pump. Crank Brothers makes a great CO2 inflator and the Topeak Road Morph G is a road pump that actually works as a pump.  There are smaller and lighter pumps but I highly recommend actually trying them before buying to see if the amount of work it takes to pump up the tire to a ride-able pressure is acceptable to you. You should also consider the emergency tire boot mentioned above.  If you are really out on your own a chain break is also a good idea.  This can be a separate Park Tool chain break or one that is part of a multi-tool such as the ones made by Crank Brothers.  Examples of both are listed below.

In my next post I will talk about how to fix the tires, and then I will follow that up with another post giving you some tips from the bike shop pros on how to prevent the flats in the first place.  Please comment on this post.  I would love to hear from you about the kind of flats you have experienced and what is in your emergency kit.