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.

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