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Slime Smart Tube Self-healing inner tube



Inner-tubes to help reduce the chance of punctures. Ideal in winter, but they're not featherlight

At every product is thoroughly tested for as long as it takes to get a proper insight into how well it works. Our reviewers are experienced cyclists that we trust to be objective. While we strive to ensure that opinions expressed are backed up by facts, reviews are by their nature an informed opinion, not a definitive verdict. We don't intentionally try to break anything (except locks) but we do try to look for weak points in any design. The overall score is not just an average of the other scores: it reflects both a product's function and value – with value determined by how a product compares with items of similar spec, quality, and price.

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Slime Smart Tubes are inner-tubes containing a thick liquid which instantly repairs punctures. They work well, and are a very handy option for winter riding, but there is a weight penalty.

This kind of inner-tube is well known in the mountain-bike world, but Slime Smart Tubes are also available for road bikes in two sizes: 700c x 19-25mm and 700c x 28-35mm, both with presta valves.

Here’s the theory: you get a thorn or flint in your tyre and it makes a hole in the inner-tube. As the air starts to escape, a bit of the thick liquid (aka slime) comes out too and then solidifies, instantly sealing the hole.

In practice, these Smart Tubes seem to work. I’ve been testing a pair in my winter training bike for a couple of months and haven’t had a puncture yet.

Fitting is exactly as usual, and you can pump up the tyre to your usual pressure: in my case that's 100psi inside 700x23 tyres.

The Slime Smart Tubes weighed in at 170g each on the scales, so there is some extra weight to consider (50 to 100g more than usual, depending what you usually use), but this is no problem on a winter training bike.

I didn’t notice a major difference in ride ‘feel’ –  just a tad less lively – but once again no big problem on a winter training bike. If it makes you work harder now, you’ll go even faster in the summer, right?

For the first few hundred miles I was running the tubes inside some reasonably heavy tyres (Bontrager All Weathers) which obviously provided some additional outer protection. Later I tried the tubes inside a lighter pair of tyres (Schwalbe Duranos); still puncture free.

Of course, maybe I would’ve been lucky anyway, so after the road-trials it was time for some further testing.

First test: I deliberately rode over a drawing pin and kept going along the road. I could hear the clicking of the metal on the tarmac as the tyre went round, and there was a slight drop in pressure, but I could keep going without trouble. Back at the lab, the gauge revealed a fall from 100psi to stabilise at 80psi.  

Second test: Take the pin out, and immediately ride down the road again. There was a sound of escaping air for a few seconds, and there was another drop in pressure, but once again I could keep riding. Back at the lab the gauge showed the pressure had fallen again from 80psi to stabilise at 60psi.

Third test: Drawing pin in, then out straight away, then ride down the road. This time the pressure fell from 100psi to stabilise at 70psi.

(Incidentally, the self-healing does not seem to work if the bike is stationery. I assume the spinning wheel needs to spread the slime around, and centrifugal force may play a part too.)

So, on the road, these tubes seem to work (although maybe I was lucky), and this performance seems to be backed up by my drawing-pin lab tests. It seems that the slime works better if the object causing the puncture stays in the tyre (which is often the case in the real world, as anyone who’s struggled to pull out a thorn from the inner casing at the side of the road will tell you).

If you’re a tourist encountering flints and thorny hedge cuttings, or a commuter dealing with glass and those tiny bits of metal that come off worn car tyres, then these tubes are worth considering. If you’re riding on good roads in clean conditions, and like to keep the weight down, or if you’re happy to ride heavier tyres in the first place, then they’re something you may not need.

On cost, the tubes recommended retail is £9.99 each, though you can find them for a few quid less on-line. Obviously more than a normal tube, but for a better chance of puncture-free cycling this might be a price you’re happy to pay.




Inner-tubes to help reduce the chance of punctures. A handy option in winter, but they're not featherlight. test report

Make and model: Slime Smart Tube Self-healing inner tube

Size tested: 700 x 19/25c

Tell us what the product is for, and who it's aimed at. What do the manufacturers say about it? How does that compare to your own feelings about it?

Slime smart tubes are designed to help prevent you suffering punctures. To be precise, you'll still get the punctures, but the slime is designed mend the holes as you're going along.

The manufacturer's website says: "All SLiME Smart Tubes are factory-filled with a precise volume of Slime Tube Sealant. Smart Tubes instantly seek out and seal punctures as they occur, preventing flats, repeatedly and continuously for up to two years."

This is a fair claim, although the website doesn't mention the fall in pressure. However, this is not a major issue. You can ride on on slightly podgier tyres, or stop and pump them back up to your usual pressure. Either way, it's better than fixing a flat at the side of the road.

The manufacturer's website also emphasises that Slime works only on punctures less than 3mm, and only in the tread area, not the side wall.

Tell us some more about the technical aspects of the product?

Under 'How does slime work?' the manufacturer's website goes onto say: "Slime coats the inside of the tire within the tread area, allowing the product to seal tread area punctures. When the tire is punctured, the escaping air carries the sealant to the puncture. The liquid portion of the sealant escapes and the fibers and binders build-up and intertwine to form a flexible plug. This will allow the product to instantly seal any puncture that may occur.

Rate the product for quality of construction:

Construction seems very good. No blemishes in the tube which might develop into weak patches in future.

Rate the product for performance:

Performance is very good. No punctures in a few hundred miles of winter riding on dirty Cotswold lanes. Deliberate punctures in test conditions show the slime quickly repairs holes, with or without sharp object remaining in the tyre, although there is a drop in pressure.

Rate the product for weight, if applicable:


These tubes weigh more than a normal tube, but this might be a penalty you're happy to have for fewer punctures and peace of mind.

Rate the product for comfort, if applicable:

No major difference in ride 'feel' – maybe just a tad less lively – but this was no problem on a winter training bike.

Rate the product for value:

On cost, the tubes recommended retail price is £9.99 each, though you can find them for a few quid less on-line. This is on a par with similar products from other manufacturers. Obviously more than a normal tube, but for a much better chance of puncture-free cycling this might be a price you're happy to pay.

Tell us how the product performed overall when used for its designed purpose

These tubes worked well. I've been running a pair of these tubes in my winter training bike for a couple of months and haven't had a puncture yet - although I might have been lucky. Lab tests with deliberate puncures show the slime repairs holes, although there is a drop in tyre pressure. These tubes won't prevent every puncture, but they'll definitely reduce the chances of having to stop and repair a flat at the side of the road.

Tell us what you particularly liked about the product

Easy to fit. Puncture-free riding at best. Reduced chance of puncture at worse. Peace of mind either way.

Tell us what you particularly disliked about the product

Slightly heavier than normal tubes. Slightly less lively ride.

Did you enjoy using the product? yes

Would you consider buying the product? yes

Would you recommend the product to a friend? yes, especially for winter riding.

Anything further to say about the product in conclusion?

Overall, these tubes do the the job as claimed by the manufacturer, so on that level they score 10. They're not cheap, and not as light as normal tubes, so that knocks a point off - giving an overall score of 9.

Overall rating: 9/10

About the tester

Age: 51  Height: 5ft 10 / 178cm  Weight: 11 stone / 70kg

I usually ride: an old Marin Alp, or an old steel classic  My best bike is: an old Giant Cadex (can you see a theme here?)

I've been riding for: Over 20 years  I ride: A few times a week  I would class myself as: Experienced

I regularly do the following types of riding: touring, club rides, sportives, general fitness riding,


Add new comment


KiwiMike | 10 years ago
1 like

Wow, so many negative comments. Living in the North Hampshire Downs, we are surrounded by thorny hedges and fields full of flint shards getting washed onto the roads year-round. The people in our club running Gatorskins *and* Slime tubes just don't get flats. Ever. Those of us running just Gatorskins get maybe 3-4 a year.

We have banned people not using either as a liability on club runs, as it's almost guaranteed they will flat and hold us all up.

This is after years of experimenting with what does and doesn't work. No, even a Gatorskin and Slime tube won't save you from a 5mm+ sidewall slash - but that's what a spare tube and tyre boot are for, isn't it? So people saying you can't repair large cuts in slime tubes are being unfair. Take it home, use some isoalcohol to clean up the tube properly, then a decent vulcanising patch like a Tip-Top does the job.

We are making Slime tubes compulsory for our 100-mile+ runs.

Nick T | 11 years ago

This winter I've ridden the mean streets of london on Open Corsa CX's exclusively. 3 punctures. I can live with that when I get to enjoy all they have to offer.

David Else | 11 years ago

Thanks for the comments, folks.

Regarding 'goo' escaping or valves blocking up: – I have not encountered this problem. Yes, a smidge of slime comes out when pressing the valve-head to let a bit of air out before fitting the pump, but it’s very minimal.

Regarding deliberate punctures: – I have updated the main review to show the results of my tests in this area.

Regarding puncture patching: – Fair point. If you get a big hole in the tube that won’t self-heal then, yes, lots of slime will come out, cover the outside of the tube, and make patching very tricky or impossible. As I say in the review, these tubes won’t prevent *every* puncture (eg, big cuts or sidewalls) but they will reduce your chances of having to stop and fix a flat. Even though I had the self-healing tubes in my tyres, I still carried my normal spare inner tube/s when out on my bike.

IanD replied to David Else | 11 years ago

Didn't get the valves gunging up initially and thought they were quite a good idea. Took several months before the problem started to show and eventually rendered them useless.

Was pleased when I chucked them out and went back to normal tubes.

Your tests show that they will work in certain circumstances, but unfortunately I found they just failed completely and made a huge mess as a result. That was then compounded by them being impossible to repair.

Would be interested in an update if you keep using them for a year or so to see if you get the valve gunging up problem.

Lungsofa74yearold | 11 years ago

Ha ha - methinks lots of people are due some punctures  19

hounslowrob | 11 years ago

When people tried to buy these in the Halfords i worked in we would advise them to just buy regular tubes and save their money. Not worth the mess or weight.

themartincox | 11 years ago

go on, stab the tyre with a knife and see how it goes!

sorebones | 11 years ago

Agree with earlier comments - how strange to review this product, award a high score but not actually confirm if it works by deliberately getting a puncture?! It looked great until I read the reports from others above using it with less success, it sounds easier to live with the odd puncture (I've only had one in 3 winters).

What Mid Life Crisis | 11 years ago

+1 for avoiding the hassle of leaking goo. Last winter went through with no punctures on Schwalbe Marathon Plus. Change of bike with less clearance - just done 9 months on Conti Four Seasons with no punctures either.

mikeprytherch | 11 years ago

I agree with the comments, the valve always gets gunged up and makes topping up hard and on one wheel impossible, I had to throw the tube away.

This winter, Ultra Gatorskin tyres used... zero punctures, maybe I got lucky, but as I've never gone through a winter without a puncture before they get my vote.

Northernbikeguy | 11 years ago

I ran these on my winter bike and I found they constantly lost pressure above 65PSI. They're not very good for high pressure tyres.

Better off getting tyres with puncture protection.

Oh and to agree with IanD, these things sprayed green gunge all over my rims every time I deflated them to swap tyres (for my turbo).

IanD | 11 years ago

Found these to be a nightmare. Valves constantly getting gunged up both with Presta and Schraeder types.

Even worse when I did puncture. Green gunge everywhere and apart from totally failing to retain pressure, it made it impossible to patch the tube.

Haven't tried any other brands, but have reverted to normal (lighter) tubes and haven't found any increase in the number of punctures I have.

Thought they seemed a good idea, but the constant need to strip down valves, vibration caused by the sealant and mess made when punctured has been enough to dissuade me from using them again.

neil b | 11 years ago

I had these in my mountain bike a few years ago. Not only did it not seal the hole very well, but it then coated everything in green goo, and made patching the tube nigh on impossible.

Stans fluid squirted inside a tube before inflating has a good reputation, if you happen to have some of that lying around, I've used this tubeless on the MTB, and that really does work! Not tried it on the road bike, but it was something recommended to me for tubular tyres too.

badkneestom | 11 years ago

When I saw 4.5 I expected assurance. Why wouldn't you purposely run over a thorn to truly test the product?
For all I know, you got lucky and didn't hit anything that could puncture your tire.

localsurfer | 11 years ago

I've used these and the halfords own-brand version, and I think the Halfords ones are actually better. The goo in the slime tubes doesn't always clot, and tends to bung up the valve. The Halfords ones are a bit lighter, the goo is less viscous, and they just seem to work a bit better. Cheaper too.

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