Alan Ardizone

What's the most aggravating and common thing that plagues us riders ?

It's not the wise-guy mechanic at the LBS. It's not your significant other saying, "You're not spending more money on your bike, are you ?"

No, it's that effing flat tire !

Ever notice that a tire never goes flat at an opportune time? Not in the garage when you have all day to fix it, but when you're pedaling to the group ride or to work and you're already 3 minutes late.

There is a solution. Well, sort of. Several companies put weird goop inside tubes that will automatically "patch" punctures up to 1/8 inch (3 mm). Because most punctures are caused by tiny glass cuts or thorns, that's a huge boost to your odds of getting where you're going on time.

All sealants work similarly -- the stuff plugs small holes the instant a puncture takes place, hopefully. This is done by strange hairy fibers or little platelets contained in the liquid inside the tube. As the goo tries to seep through a hole, the solids jam like the unlucky people fleeing a burning nightclub.

In most cases you'll never know you just punctured. If the tube does go soft before the air leak stops, find the culprit in the tire tread, pull it out and reinflate. If that doesn't give you a hard tire, the hole is too big for the sealant to work. Nothing is perfect.

The downside of sealants is weight right where you don't want it -- out there in that spin zone where the faster you go, the heavier it gets. If you've spent a thousand bucks for lightweight wonderwheels, you'll probably prefer to fix flats.

But if you tend to flat a lot or can't afford delays -- say, because you ride to your job, school or appointments -- tubes with a sealant might be worth the extra rotating weight. The same goes if you dread fixing flats on the roadside for safety reasons or because you find the job dirty or difficult. Maybe you don't even ride alone for fear of puncturing.

I won't pass judgment on that, but I will pass along the following info about companies that produce sealant tubes with presta valves (the thin type with the little screw cap) that are found on almost all better road bikes.

� Slime. This is probably the most recognized brand with its florescent green sealant. The weight range goes from as low as 117 grams for a 700x20-28 Lite tube ($12) to 220g for a 700x28-35 standard tube ($9). Only one valve stem length, 39mm, is offered. See all of Slime's bike products, including Schrader valve tubes (like on a car tire) at Slime website

� Bontrager. This Trek affiliate offers 2 tubes with Slime sealant. Both 700x18-25 (180g) and 700x28-32 (220g) have 48-mm valve stems. This longer size is a great idea if you have medium-deep rims, and it works fine for lower profile rims too. These tubes cost about $12.

� Specialized Airlock. Two sizes (700x20-28 and 700x28-38), each with a 36-mm valve stem. Specialized does not list weights but they're in the range of comparably sized Slime and Bontrager tubes. The dull yellow sealant is like Slime in consistency. About $15. Specialized Airlock

� True Goo. This stuff rocks! It's a MIC (made in Colorado) product manufactured by a cool guy named Glen True (no lie). His Goo is much thinner than other sealants and has a nasty beige-gray color. It works extremely fast, being full of minute little discs that plug punctures and, as an added bonus, balance a spinning wheel.

True offers 700x20-28 tubes with valve lengths of 36, 48 and 60 mm and weights between 176 and 183 grams. Plus, there is an extralight version -- 145g with a 48-mm stem (add 3g for a 60 mm). The company's 700x28-38 tube comes only with a 48-mm valve and weighs 250g.

True Goo is the sealant my shop uses for our customers, literally by the gallon. It's the best we've found and we have tried them all. Tubes range in price from $8 to $12 and can be bought through the website at truegoo.com

For those who use Schrader valves and feel jilted by this article, I apologize. The cool thing is, you can buy these same sealants, unscrew the valve cores, pump in 4 oz. and off you go -- flat free and clam happy. Sealant also can be added through presta valves, but it's a pain and messes with your mind and the floor. Trust me on that.

Remember two things : Sitting by the side of the road patching a flat does nothing to improve your timeliness or your mood. And I'm not recommending sealant tubes for racing, where weight does matter. But do consider using them for training, recreational riding and, for sure, on your commuter bike.

Oh, one more thing: Forget the stuff in the aerosol can you get at places like Wally World. It's toxic as hell and doesn't work for bicycles, period.

13 novembre 2008

RBR's Comments page just got "slimed" by feedback about tube sealants, the subject of Uncle Al's column last week. We're passing along a couple of first-hand experiences as well as advice directly from Slime, the best known of the anti-puncture companies.

� "Slime, which is the only brand of goo I've ever tried, works great in mountain bike tires or tires needing less then 60 psi. There's a problem, though, with higher pressure road tires. Slime will not stop a high-pressure leak, no matter how small the hole, until the pressure drops below 65 psi." -- Froze

� "I always carry a spare tube even when using slimed tubes. If you get a large hole (like the time I found a golf tee in my tire !) the slime will make it impossible to apply a patch. Sealants work really well on vine thorns, which is how I used to get my flats." -- Bob near Berkeley

� A Canadian roadie who signed on as Energizer says he asked the Slime company 2 key questions. Here are the replies he received :
How do you keep Slime from getting into the pump or plugging the valve stem ? "Before inflating or deflating a pre-Slimed tube, it is important to rotate the tire so the valve stem is in the 10 or 2 o'clock position. Let the bike stand like this for 20-30 seconds. The sealant will slide away from the stem and pool at the base of the tube, preventing it from blowing up and out of the stem where it can either clog the valve or your pump."

How do you keep Slime from freezing ? "The main ingredient in Slime is propylene glycol, which is a food-grade anti-freeze (non-toxic, non-flammable and non-hazardous). This ingredient helps maintain the product's consistency in both extreme heat and freezing cold. Slime will not freeze solid, but can become a bit thick as temperatures drop; however, it will regain its normal viscosity as soon as the tire is in rotation and the tire begins to heat from the friction."

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