Silca Ultimate Tubeless Sealant 1L

Silca Ultimate Tyre Sealant has been updated, and comes with some bold claims of over six months’ longevity and the ability to seal punctures up to 6mm. After months in the tyre, it’s clear longevity has improved significantly, but puncture protection lags behind the best.

The original Ultimate Tubeless Sealant stood out for its use of recycled carbon fibre strands, designed to form a plug inside the tyre in the event of a puncture. While Stu reported good performance, my experience while reviewing it for off.road.cc was that it was inconsistent, with poor sealing, clumping fibres, and a tendency to dry out quickly.

I found the long carbon strands would often clump together after just a few weeks, limiting performance over time. And despite bold claims of sealing holes up to 7.5mm, which was bigger than any other sealant at the time, it dried out quickly, and Silca introduced a replenisher to help it last longer.

> 9 things they don’t tell you about tubeless tyres

The original sealant also couldn’t be injected through a valve because of the strand length, and while this isn’t a dealbreaker for everyone, many find it a quicker and cleaner method.

Silca has now updated the formula, retaining the carbon strands but introducing a revised latex blend made from both natural and synthetic ingredients. It’s billed as the world’s first hybrid blend of natural and synthetic latex, is ammonia free, safe to use with CO2 canisters in an emergency, and has a freezing point of -15°C. It’s also claimed to last over six months inside a tyre.

Performance

I used the new sealant in both road and off-road tyres. It remained inside the road bike tyres for five months before I began writing this review. Following Silca’s recommended quantity, I used 55ml of sealant in a 700x28mm tyre, and ran them at 65-75psi, depending on the ride and location.

Injecting was straightforward, though with a maximum capacity of 60ml the injector – not included, but available for an extra £9.95 – is small and makes filling larger gravel or mountain bike tyres a longer process. Also, the valves I used are standard tubeless types and I had no issues, but if you’re using valves designed for tyre inserts you might struggle to inject the sealant because of the smaller internal openings.

Initially, the sealant appeared to be working well. At the four-month mark, I removed one side of the tyre carcass to inspect it, and the sealant was still fluid with no clumping of the carbon strands, which was promising. Up to that point, I hadn’t noticed any punctures while riding, and there was no visible evidence inside the tyre either.

Unfortunately, I later experienced a puncture mid-ride, which led to a quick but not instant loss of air. The sealant sprayed out, with some visible bubbling, but despite holding the puncture at the bottom to encourage sealing, it failed to plug the hole. After fitting a tube to get home, I inspected the tyre and found the puncture to be relatively small, just a few millimetres in diameter, though there was no sign of what caused it.

A few weeks later, the front tyre suffered a second puncture, this time from a thorn lodged in the carcass. I removed the thorn and saw the sealant bubbling, but again it did not form an immediate seal, which I would have expected for a hole of that size. I was able to leave the bike stationary to allow a seal to form, but the tyre had lost almost all air and needed reinflating. The seal did hold afterwards, and it has remained airtight since.

While it’s possible there were other punctures that sealed without my knowledge, based on Silca’s bold claims I would have expected both of these known punctures to seal quickly. Both fell within the guidelines suggested by Silca. Silca doesn’t specify any pressure limits, but 60-65psi should be within its parameters for performing reliably.

One area where the sealant did deliver was clean-up time. After removing the tyre, the liquid washed out easily, leaving no dried residue or staining, which is common with latex-based sealants. If the sealant sprays out during a puncture, it also washes off the frame and components with minimal effort.

Value

Silca Ultimate Tyre Sealant is available in 65ml (£6) and 500ml (£24) bottles, as well as the 1-litre helping on test (and a 12x65ml multipack for £69). And while the new formula is now injectable, as I said above, the injector is sold separately, at £9.95.

The most cost-effective way to buy the sealant is in the 1-litre bottle. At £42 it’s among the more expensive options, although Dynamic Barkeeper Pro is higher still at £50 for the same amount.

One of the best sealants I’ve used is Peaty’s Holeshot, which costs £29.99 for a 1-litre bottle, lasts well, and has consistently performed across various punctures.

Conclusion

This updated Silca Ultimate Sealant has clearly improved in longevity and when cleaning up, with fluid that stays in the tyre for months and washes out easily. However, it failed to seal punctures that were well within its claimed limits. While it’s not a total write-off and does show some sealing ability, the overall performance falls short of the best alternatives.

Verdict

Impressive longevity, but below-par sealing performance

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