Silca Ultimate Tubeless Sealant 16oz

Silca Ultimate Tubeless Sealant delivers something that not all sealants can - the ability to cope with the high pressures used in road tyres. It works quickly and effectively, blocking holes before much air escapes so you shouldn't need to pump at the side of the road.

Over the past few years, I've tried all kinds of sealants in a lot of tyre and wheel combinations, and thankfully the majority have been very good. Probably the only thing that lets quite a few down is their inability to be able to cope with higher road pressures. Many are fine up until 50psi to 60psi, but above that the sealant can keep blowing out.

I tend to run my tyres at around 90-100psi for 25mm or 28mm and, if I'm honest, I find punctures rare - purely because very few things can force their way in. But if you do want to run tubeless at those pressures, I highly recommend this Silca stuff.

As expected, I didn't puncture throughout the test period so with various household items (drawing pins, nails, scalpel blades and so on) I cut through a test tyre. I found the Silca Ultimate fixed holes up to around 6mm - the company claims 7.5mm, but that's dependant on the width of the slash.

The largest I made was 6mm long with the scalpel blade and 0.5mm wide. The sealant bubbled up and had it sealed within about 30 seconds. Not much air escaped either - starting off at 100psi, it only dropped to 85psi.

Pumping more air back in, I found the sealant could cope with just under 95psi on the gauge before it started to leak again.

Foamy latex

It works, according to Silca, by using a foaming latex that carries a mixed blend of 6mm, 9mm and 12mm carbon fibre strands. The latex bubbles up, forcing the carbon fibre strands to block the hole.

Silca recommends pouring it directly into the tyre before popping it onto the rim, as its fast-drying formula will start to activate if you syringe it in through the valve, apparently. After all, it can seal holes bigger than your valve.

> Buyer's guide to tubeless tyres - find out all about new technology rubber

To be honest, I always empty the contents into the tyre before fitting, rather than going for the valve option anyway. The Silca Ultimate has been in my tyres now for around six weeks and is showing no signs of drying up yet, which to be fair is expected.

Silca recommends using its 4oz Replenisher (£12) after three months to give the Ultimate sealant a top up, so I'll be checking on it in about six weeks time to see how much is still liquid. Then I'll test the Replenisher.

Value

This bottle I'm testing here contains 473ml (16oz) of sealant at a cost of £24, which works out at just over £50 per litre. If you are using it on road tyres up to 30mm, this should be enough to fill eight tyres; alternatively, it's enough for about five gravel tyres of 30-45mm.

A lot of the sealant I get sent to test is in much smaller containers of around 100ml-250ml, so that affects price comparisons, like for like.

The CST Tubeless Tyre Sealant is £10 for 250ml, so £40 per litre. A good chunk cheaper, but it didn't work so well on bigger cuts.

Muc-Off's No Puncture Hassle Tubeless Sealant can be bought in a litre bottle for £29.99. I was impressed with it, but you definitely need to buy it in bulk for it to be cost effective.

Overall

Silca Ultimate is a very impressive sealant, and it copes well with the high pressures used in road tyres. It's not that extreme price-wise either - at least not when buying in this larger container.

Verdict

Works very well on high pressures, and quickly too