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Challenge Smart Tubeless Sealant



Works on a range of tyres and pressures, while lasting for months at a time
Quick sealing
Works on large cuts too
Cheaper solutions out there that work well

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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The Challenge Smart Tubeless Tyre Sealant works well on a whole range of tyres, from high-pressure road hoops to big, low-pressure gravel rubber, and seals cuts big and small. It doesn't seem affected by temperature changes either.

Challenge has developed its Smart Sealant to work with both vulcanised and handmade tubeless tyres, and I tested it on both with no setup issues. With a pair of Challenge's handmade gravel open clinchers I had to ride a few miles to get the sealant to completely coat the tyre and fully seal, and while that's due to the construction of the sidewall, it does demonstrate that the sealant works.

Have a stab at it

Challenge claims it can seal cuts up to 6mm, which I'd say is realistic. As is often the way I didn't puncture naturally, so instead I used a knife to cut the tyre with slits of various sizes. I found the sealant worked quickly, even on road tyres running pressures up around 70psi.

Some sealants can struggle at anything above 50psi, but there were no issues here.

Challenge doesn't go into detail about what is actually in this stuff (although they do say want isn't – like ammonia), but by the looks of it there are small particles in there too, which most likely join together to seal larger gaps.

I've used Challenge's Smart Sealant before so I can vouch for its longevity. They say six months and I'd say that's about right. Obviously it depends somewhat on the ambient temperature, and I was using it during the record temperatures of summer 2022, which meant it did dry out a bit quicker than expected.

You can top it up through the valve though, which you can with sealants featuring large particles for sealing holes.


A 250ml bottle costs £15, which works out at 6p per millilitre. That's cheaper than the Pirelli Cinturato Sealant, and Challenge doesn't stain everything yellow when you spill it, either.

The Finish Line FibreLink Tubeless sealant is similarly priced at 5.4p per millimetre, and Steve was impressed overall with its performance.


Smart Sealant does exactly what it claims to, offering good sealing against punctures and a good service life too.


Works on a range of tyres and pressures, while lasting for months at a time

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Make and model: Challenge Smart Tubeless Sealant

Size tested: 250 ml

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?

Challenge says, "High performance tubeless systems deserve high-performance tubeless sealants. The SMART Sealant was designed to work with both vulcanized and handmade TLR and Tubeless tires. This non-allergenic, ammonia-free formula can seal up to 6mm cuts, remains liquid in the tire for up to 6 months, doesn't coagulate with Co2 use, and doesn't damage rims or tires with extended use. Installation is straightforward using the application tip and there is no need to shake the bottle. Available in a 250ml/8.5oz bottle."

It works efficiently and is reasonably priced.

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

Seals up to 6mm cuts

Doesn't damage rims or tires

No need to shake

Remains liquid in the tire for ~ 6 months

Keep adding as needed through the valve

Doesn't coagulate with Co2 use


Rate the product for performance:
Rate the product for durability:
Rate the product for value:

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

It sealed a range of hole sizes, at varying pressures.

Tell us what you particularly liked about the product

Works at higher pressures, unlike some.

Tell us what you particularly disliked about the product

Nothing really stands out.

How does the price compare to that of similar products in the market, including ones recently tested on

It sits somewhere in the mid-range when compared to others we've reviewed.

Did you enjoy using the product? Yes

Would you consider buying the product? Yes

Would you recommend the product to a friend? Yes

Use this box to explain your overall score

It works effectively and achieves the claims on the bottle, for a decent price.

Overall rating: 7/10

About the tester

Age: 44  Height: 180cm  Weight: 76kg

I usually ride: This month's test bike  My best bike is: B'Twin Ultra CF draped in the latest bling test components

I've been riding for: Over 20 years  I ride: Every day  I would class myself as: Expert

I regularly do the following types of riding: time trialling, commuting, club rides, sportives, fixed/singlespeed,

With 20 years of road cycling and over 150,000 miles in his legs it's safe to say Stu is happiest when on the bike whatever the weather. Since writing his first review for back in 2009 he has also had a career in engineering including 3D-CAD design and product development, so has a real passion for all of the latest technology coming through in the industry but is also a sucker for a classic steel frame, skinny tyres, rim brakes and a damn good paintjob.
His fascination with gravel bikes is getting out of control too!

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