Slimy on the inside

review from – think I might get these …

Slime Pro Pre-filled Lite inner tube 1

These Slime Lite Smart tubes are effectively the same as the regular Smart tubes reviewed previously on, but they address the weight criticism with a lighter inner tube. On our scales this 19/25c inner tube weighed 102g, a 68g saving.

Using a lightweight butyl tube has allowed Slime to reduce the weight. Inside is the same green fluid that is claimed to be able to seal a puncture up to 3mm. I’ve seen a demonstration with a nail and it’s highly impressive, but that’s nothing compared to real-world testing. I’ve had them fitted to my steel touring/training bike, a bike that gets some seriously heavy miles on rough rides, and in three months haven’t had one flat.

To thoroughly test the tubes, I’ve been taking to gravelled byways and bridleways, deliberately trying to inflict harm on the inner tubes. Despite trying, I’ve not managed to run out of luck yet. Tyre choice and pressure is a factor, and for the record I was using Hutchinson Fusion 3 x-Light tyres with 90/95 psi front/rear.

With the weight penalty over a regular inner tube it’s no surprise there is a slight difference in ride performance compared to the previous setup with normal butyl inner tubes. The difference with these new lighter Slime tubes is much smaller and you’ll be hard-pressed to notice the difference, unless you really search for it on climbs and hard accelerations. There’s little difference in ride feel too.

You might not want to fit them to your race bike, but for commuting and training purposes they’re fit for purpose. The small weight increase is offset by the reduced possibility of puncturing, and as we head into autumn with the higher risk of flat tyres – due to more frequent rain washing glass and crap into the road and water acting as a particularly good lubricant for sharp flints to penetrate rubber – they could be worth fitting to your bike.

The reason for buying these inner tubes is obviously to avoid punctures, but unfortunately I haven’t yet suffered a flat in my time testing them. So it was into the garage that I went to conduct a workshop test to find out how they handle being punctured. With the bike in a stand, I pushed a drawing pin through both front and rear tyres. Nothing happened. Pulling the drawing pins out and giving the wheels a spin, then stopping them, the green goo visibly bubbled out through the holes. Then stopped. A couple more revolutions. The Slime had sealed the holes. A pressure gauge revealed the tyres had dropped just 15 psi during this process, from 100 to 85 psi.

I then went for a one hour bike ride, without incident. With the pressure gauge out again once I was back home, the tyres were holding the same 85 psi. That’s a small enough pressure drop that you could puncture during a ride and not even realise.


The upfront cost is higher than a regular inner tube, but you should see a reduction in punctures.


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