A sustainable cure for bike flats?

Bob Forgrave

Imagine if your car tires still required the same level of regular tire maintenance that your bike tires do…

• If you haven’t driven anywhere for a month, you need to stop first and pump up your tires to avoid self-created “pinch flats” between the road and your rim.
• If it’s been at least a week since your last tire fill-up, a top-off is a good idea for maximum efficiency.
• Occasionally, you’ll have to stop your fun, remove a wheel and pull off the tire to fix it.

Even with pneumatic tires, today’s cars have progressed far past these days of high-maintenance activity.

Amazingly, bike tires have not progressed significantly in the past 130 years, even though the pneumatic tube started on the bicycle, invented in 1888 by a veterinarian named John Boyd Dunlop. Perhaps you’ve heard of Dunlop Tyres?

John Boyd Dunlop riding his newfangled pump-up tires.

Nobody wants a great bike trip ruined by flat tires! Clearly, any reduction in flat risk is a good idea. But what’s the best good idea?

Here are four different approaches in order of effectiveness, from least to most:

1. Tire sealants (Tubeless, Slime, or Stan’s No Tubes)

In this method, your tire always is sloshing around a little bit of liquid. When you get a puncture, turn the tire with the puncture down, and the liquid will fill the hole and automatically clog it–maybe even through the simple action of riding. You may have a leak and never know it!

Sounds perfect, right? So what’s the problem? There are four of them, actually:

• Weight. You’ll need enough sloshing slime to move into place when needed. That’s easy on a large mountain bike tire, but not so easy on a road bike wheel, which spins faster and has more rotational weight penalty.
• Tire pressures. Tire pressures above 45 psi are less effective at sealing, and above 60 psi, don’t expect any effectiveness at all. Also below 15 psi on mountain bikes, you are more susceptible to “tire burps”, where your tire separates from the rim, spews liquid everywhere, and needs an air compressor to fix. Always ride with CO2 cartridges.

Oof! The beginning of a very long day. That’s now a front wheel after landing impact, with no tire and no control.

• Clogging. That bit about clogging leak holes? Yep, it can also clog your inbound air hole. Know how to clean out your valve stem.
• Drying out. Slime is liquid only until it dries out. Then it’s halfway between coral and a sponge–and totally useless. Plan to occasionally remove your tire for maintenance, even without a flat.

You could end up with this in your tire–the coral, not the quarter.

If you go with this approach, MTB Action had a tire-sealant shootout, with the wonderful warning, “All tires were harmed during these tests”.

There’s also Slime in a tube, which isn’t really its own thing; It’s Slime…in a tube. Throw out the tubes regularly as they dry out.  

2. Thicker tires or tubes.

It may not be sexy with the vocal cyclerati, but thicker tubes or tires can avoid a lot of pain by stopping glass, sharp rocks, small thorns, and more before they hit your tube.

Thicker tubes are more on the MTB side, for tires 1.5″ and wider. Thicker tires, such as the Continental Gatorskin, are optimized for low-flat road riding. I’ve personally ridden years between flats this way.

My go-to road tire: The Continental Gatorskin.

3. Tire inserts.

Tire inserts are designed to stop any threat that has already penetrated your tire barrier, before it can get to your tube. There are flimsy inserts (semi effective), and the cheapest solution of cutting the edge bead off an entire tire and sticking it inside (thorn-proof but wobbly at high speed)…and then there’s Tannus Armour in a class by itself.

Tannus Armour is thick lightweight solid foam that bogs down even the nastiest goathead thorns. It’s ride-flat capable, so mountain bikers can go as low as they want for maximum grip. If you ever do get flat tires, you can simply ride back home. (Not that we’ve personally heard of that; We know of only one flat in the four years that we’ve sold this, and he already had 1,200 miles on the inserts.)

Sometimes the reason for Tannus Armour isn’t even about flat tires.

4. Airless tires. 

This is the holy grail of cycling–a tire so comfortable that it mimics a pneumatic ride, so efficient that riders don’t notice the difference, and yet solid so you can run over any danger and not care. Zero maintenance. 

It’s also very difficult to achieve. You’d have to be, probably, a chemist and a second-generation tire expert to get it right.

Funny thing… Richard Adams learned the tire business . . . correction…in the UK, it’s the tyre business…from his dad. He’s a chemist. And he’s got a Kickstarter campaign right now for his recently tested next-generation, closed-rubber cell Gecko airless tires for road and gravel bikes.

These are no ordinary airless tires, as this chart shows.

There’s a lot of focus on sustainable manufacturing and recyclability, and I’d like to hear more, but that benefit often depends upon where you live and the systems in place that enable materials recycling. Your recycling and mine may differ.

What got my attention was the installation time. I’ve never gotten an airless tire installed in less than 45 minutes, and this one is supposedly comparable to a pneumatic tire change of 5 minutes? (I’m actually not at 5 minutes there either, more like 7, because I always want to know where the flat came from, and investigation takes time.). Clearly this advancement alone is groundbreaking.

This chart also shows a rather large gap between other airless tires and pneumatic tires in the areas of comfort, rolling properties, grip and wet grip–known gaps that this new tire brand allegedly bridges well. That feedback is apparently the result of UK user group testing:

In the last few weeks, two leading UK cycle dealers and a leading UK bicycle manufacturer have all road tested the prototype Gecko 700 x 43 Tyre and they all agreed they are the best airless bicycle tyres they have tried by a significant margin.

They highlighted that the tyres were ‘remarkably close to the comfort of a pneumatic’ and that ‘most riders would not be able to tell the difference.’

This chart doesn’t mention weight, and that’s important when comparing a solid tire to a hollow tire. The current 700 x 28mm Gecko airless road tire prototype is 400 grams. This compares against 320 grams for my trusty Gatorskin flat-resistant tire, plus a standard Continental 700 x 28 presta valve tube of 135 grams, for a total weight of 455 grams–a full 55g more than a Gecko airless tire! What???

The 700 x 43mm Gecko tire for gravel bikes is 850 grams. I can’t personally speak to this weight vs. typical tires of this dimension, but would be interested in your perspective. Is this size equally competitive?

Let’s go for a ride! Wait a minute. I need to do this again on both our bikes…

One thing is for certain. Ignoring flat tires entirely, I’d really like to stop caring if my tires are adequately pumped every time I ride. Forever. Flatbike will be encouraging this project as a Kickstarter backer, and I personally will be testing these tires in both sizes on my own bikes. If all goes well, I can easily see Flatbike stocking Gecko tires for North American cyclists of all types.

Stay tuned! And if you’d also like to get your hands on an early set of Gecko airless tires, support their Kickstarter project before July 28, 2022.

Happy flat-free biking!

Bob Forgrave is president of Flatbike, an
ecommerce company offering full-size folding bikes
and kits to make any bike take up half the space.

425-985-6219