Weldtite Dr Sludge Puncture Protection Sealant

Weldtite Dr Sludge tyre protection sealant does the job it's claimed to, sealing small holes up to 3mm with the minimum of fuss. If you're already running stout tyres and thorn-resistant tubes then it adds extra protection, but I'd suggest tougher tyres/tubes as first measures. Also, don't expect it to mend rips/punctures along seams or bigger holes – and do expect things to get messy in such scenarios.

The sealant has been around in this form for quite some time, although Weldtite has recently brought out a tubeless-ready version. This one is designed for inner tubes, including golf carts, wheelbarrows and so on, and is best suited to bikes with Schrader or Woods valves.

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Weldtite describes Dr Sludge as an 'environmentally friendly, water based formula'; judging by the smell, texture and consistency, I'd say it was some form of liquid latex. Its ability to fill cuts up to 3mm in diameter is quite impressive given most factory-filled tubes claim and seal those around 1mm. That said, they do all work to the same basic science. In the event of glass or similar sharps piercing the tube, centrifugal forces propel the goo, which, when exposed to air, cures on contact, with minimal loss of pressure.

There are some limitations, though. Specifically, tube seam punctures will mean a new tube, plus a big, sticky mess. I speak from previous experience, using a different brand's ready-filled tubes, in the middle of winter, with a small child cruising behind on the tag-along...

Fill your butes

Our 250ml test bottle is sufficient for two 700C or 26 inch tubes. While it can be delivered with the wheels in situ, I erred on the side of caution, introducing it to fresh tubes over the kitchen sink. Either way, give the bottle a brief shake and remove the top. This comes with a valve core remover, and you'll need to extract those from your tubes first.

Next, attach the flexible hose over the valve stem and squeeze the bottle gradually until you've released half the contents. Once the valve has 'burped', distribute the sealant evenly by simultaneously rotating and squeezing the inner tube.

Clean any excess from the valve stem, reintroduce the core, refit and inflate.

To evaluate the formula's prowess, I opted to share the bottle between my fixed-gear winter trainer and my mountain bike-derived rough stuff tourer, which was sporting some sprightly but puncture-prone rubber.

There's a slight weight penalty, which is noticeable during reinstatement and when running a lightweight folding tyre – but you wouldn't be running goo-filled tubes on a TT missile. It's quickly forgotten anyway, given a few miles, especially if you're running heavier duty touring/commuting rubber.

Performance

Since I was retiring the Univega's lightweight trail tyres I purposely delivered a stout tack through the front's casing. There was a brief pregnant pause then an audible hiss, but within a few rotations the goo did its thing. I checked using my SKS digital gauge and 6psi was the total loss, plus there was no further leakage or loss some 25 mixed terrain miles later.

With hedge-cutting season in full flow, lanes carpeted in vicious thorns, a couple struck lucky – the rear succumbing twice along the same stretch, demanding I stop, extract the offenders, and brush the casings again before continuing. This time 12psi bled out, but that's a minor inconvenience on a commute compared with flatting, especially at night and along unlit roads.

Using a decent quality middleweight butyl tube on my fixed gear winter trainer and alternating between Clement Xplor USH and Maxxis Roamer tyres, I've had a couple of flints pierce the casing, nicking the tube. Each time I lost 8psi, but again, provided you check and reinflate your tyres regularly, this isn't much of an impairment.

> Regular pre-ride checks

Tube quality is another factor to consider. I'm quite partial to bulk buying budget butyl, primarily as wedge pack staples, but the thinner walls mean they're trickier to patch. Bombing along a stretch of wet, silty unmade road on my tubby tourer, a flint became embedded in the shoulders and my ear-to-ear grin was displaced by that sinking feeling. Unfortunately, the seam had been nicked and Dr Sludge couldn't keep pace. Long story short, the clear-up was messy, involving foliage and a new tube.

By contrast, I've had no such problem on the fixed, although – in keeping with this genre – the sealant has tended to clog the valve, requiring occasional stripping and cleaning. This is also true of ready-prepared models, including BTwin's self-sealing tube, which is still going strong on my traditional road bike.

Conclusion

Ultimately, Dr Sludge genuinely does what it says and is reasonably priced. Big sharps at the right (wrong) angle can render them useless. Those seeking some additional protection on their winter training bikes might find something like the BTwin sealant-filled model mentioned above a more practical option, though.

I have to say, though, decent tyres with aramid casings are my first defence. Going the belt 'n' braces route with a cross/gravel build, I'd opt for something like Kenda thorn resistant inner tubes. These do add a fair bit of weight, relative to a standard or even sealant-filled model, but are ultra-dependable and easy to patch.

Verdict

Offers reasonable puncture protection, but blowouts can be extremely messy