Slime Pro Tubeless Ready Kit

When it comes to tyres, it's now accepted wisdom that softer and wider is faster for a number of reasons, including a shorter, fatter contact patch giving lower rolling resistance and better grip. The Slime Pro Tubeless Kit lets you ditch your clincher combination for a fatigue-reducing, smooth-rolling silky setup. It has clear instructions, it's reasonable value, and – with the right tyre and wheel combination – still working for me 2,000km later.

In the UK a major benefit – possibly the major benefit – of going tubeless is puncture resistance. A tubeless tyre is inherently stronger and more puncture-resistant than a normal clincher or tubular. There's no inner tube to pinch flat against the rim should you hit a pothole, and the sealant should fill any small cuts that do occur.

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The kit consists of an 8oz bottle of Slime Pro sealant, a roll of black Gorilla fabric tape, two 40mm tubeless valves with a valve core tool, a Microflate Nano CO2 inflator with two 20g cartridges, two Genuine Innovations tyre levers and a Presta-Schrader valve adapter if you need to use a compressor.

The kit is intended for mountain bike as well as road use, hence the wide tape and inclusion of a large-volume CO2/Schrader compressor adapter – you're much more likely to be needing CO2 or compressed air to seat a large-volume mountain bike tyre than a smaller, tighter-fitting road tyre.

Given the warnings on the packaging you'd have hoped for some rubber gloves as well – make sure some are to hand for fitting. Half the sealants' ingredients are of 'unknown acute toxicity', while three-quarters pose 'unknown hazards to the aquatic environment'.

The instructions clearly state 'NOT FOR USE TO CONVERT NON-TUBELESS SYSTEMS TO TUBELESS'. Fortunately here at road.cc we drop icecubes down the vest of all-caps bolded instructions.

While you can bodge the rest of a tubeless road setup, there's one thing you have to use: a proper tubeless tyre. This is a must. In the mountain bike world, people repurposed tubed tyres for years, but on a road bike this is a total no-go that could get you killed or worse.

The issue is 'burping'. As you roll over into a corner the tyre deforms and eventually the looser-fitting or more elastic bead unseats from the outside edge of the rim, allowing some air to escape. Road tubeless tyres have much stronger beads (usually carbon fibre) and tougher sidewalls to prevent this.

On a slow dirt track a burp is usually recoverable and you just pop some more air in. If it happens in the apex of a 70kph Alpine hairpin the consequences would be injurious at the least. Don't even think about it. Get yourself a decent tubeless tyre such as the Schwalbe One, and be confident that it's probably going to be a tight bugger to fit.

Setup

I started off with a set of standard Shimano RS500 wheels and a pair of Hutchinson Sector 28 tubeless tyres.

The instructions are pretty good – non-mechanically-minded persons shouldn't have a problem.

I cleaned the rim with a cloth and iso alcohol to ensure best possible tape adherence. The tape needs cutting down to your rim's internal width plus 3mm. Fortunately it rips along its length beautifully: just measure the right width, make a small cut, rip a bit along and start taping, pausing to rip the excess tape off as you go. Some tension is needed to 'walk' the tape down between the rim walls and onto the bed – it quickly becomes both intuitive and strangely pleasurable.

After two laps of the rim (see later comments regarding one layer vs two), seat the tape down well with a cloth and carefully get the edges done with a plastic tyre lever. Poke the valve through the tape and tighten it down hard.

Fitting the tyre is fun – the thicker bead makes for a squeeze between the protruding valve block and rim, with the tight tolerances meaning getting the bead over the whole rim is quite a battle.

Both GI tyre levers snapped immediately. Note: take great care not to damage the new tape.

Finally, tipping 1.5oz of Slime in using the cup provided was easy. Rotate the wheel and fit the rest of the tyre.

The point of including the Microflate Nano CO2 inflator (and the compressor-friendly Schrader adapter) is to seat the tyre the first time. GI advise that Slime Pro is the first sealant to be both CO2-compatible and to contain an antifreeze – both important issues if you use CO2 for installing tyres or reinflating on the road, and ride in cold weather.

Getting the Sector 28s to seat on the RS500s required a whole cartridge for the first wheel. The second one went on with a trackpump. Unfortunately, after about two or three hours the tyres were down to about 20psi. There were no evident leaks around the tyre bead or valve – it turned out to be micro-leaks through the Sector tyre wall. The Sector doesn't have a Butyl liner in the sidewall, and the combination of that plus the latex-free Slime Pro sealant means an airtight system couldn't be established. This is no slight on either product - the Sector 28 is a highly-regarded tubeless tyre that got 4 stars from road.cc. Rather, the lesson is that this combination is to be avoided.

The next combination I tried was a pair of Schwalbe One tyres on a new pair of Cero AR24 wheels, which needed some encouragement with decent levers to go on but nothing unseemly. This time one wheel held air from the start – 100psi, well over the likely user pressure. The other was down to 20psi after a few hours, but no sidewall leaks at all.

After a bit of investigation I came to the conclusion that it must be the Gorilla tape leaking in some way, so added another layer. This time the wheel held air fine.

After a week the first wheel started losing air, so I added another tape layer. Again, success. The tape had some marks where I hadn't been careful enough with the tyre lever, the second was unmarked – so the only conclusion I could draw was that after a few days of air pressure bulging the Gorilla tape into the spoke holes, there were enough micro-leaks in a single layer to make a difference.

On the road

The ride of the Cero/One combo is nothing short of a revelation, running what most would consider to be barmy pressures of 70psi rear/40psi front. My rider + bike combo weighs 83kg, with the recommended pressure for 28mm tyres being 80 rear, 50 front for a 15 per cent tyre drop.

The stiffer sidewalls of the tubeless One made for a harsher ride than the same size clincher + tube at these lowish pressures, but going 10psi lower still transformed the ride into smooth, fast, comfortable and grippy. This is comparing them with the class-leading puncture-resistant Continental GP 4 Seasons 28mm – so high praise.

Rural Hampshire roads being what they are, a few decent potholes were whanged – the sort that would have you wincing and then stopping to repair the inevitable double snakebite – but such outcomes were non-existent with this tubeless setup.

I tried the same taping and sealing on a pair of Raleigh Probuild wheels with Alex CX28 rims. Again, two layers of tape and the system held air just fine.

As a process for converting to tubeless, the Slime Pro kit works. It was even easier with a pair of Mavic Ksyrium SLR alloy clinchers, as they feature a rim/spoke design where the rim is sealed – no spoke holes needed taping. So a short strip of tape over the valve hole to assist the rubber valve block in achieving airtightness, Schwalbe Ones on with a reasonable but not outrageous use of levers and, hey presto, fat and comfy rubber on a nice light wheelset.

Long-term maintenance

I've been running the Schwalbe One + Cero AR24 setup for about three months and around 1,500 fast, hilly, flinty kilometres with no problems at all. Once a week 10psi or so needs adding, but nowhere near what was needed using a standard clincher/tube setup, which had to be topped up every few days.

The only maintenance issue I struck was after a month or so the valves started to get a bit clogged. When topping up with air, if there's even a drop of sealant inside the valve, undoing it to add more almost inevitably requires a press on the valve core – which then sprays a tiny bit of sealant through the valve itself. Over time this solidifies, eventually blocking the valve – hardly surprising, it is a coagulant, after all.

The sealant does such a good job it's impossible to unblock the valve using wire or high-pressure air. The solution is to unscrew the valve core completely once a month using the included valve tool, remove it, and unscrew the small knurled head off the valve completely (this requires pliers the first time as it's peened over to prevent it falling off when unscrewed).

Once you've removed the head you can take the core of the valve right out and get rid of the offending plug of solidified sealant. Your valve core is now as-new and can be re-installed – just don't unwind the head too far when out and about. Although if you do it's not the end of the world, as air pressure will hold the valve closed. Considering the benefits tubeless brings, as an extra maintenance step it's not onerous – just remember to do the knurled-head-peening-removal when you first install the valve, and take the tiny valve tool along so you can remove any blockage when out in the wilds.

When the (almost) inevitable happens

Slime appear to be correct with their 'seals cuts up to 3mm' advice. A 3mm-wide cut right on the centreline of the rear Schwalbe One on the Mavic Ksyrium SLR resulted in a flat tyre and all the sealant leaking out. Turning the cut to the lowest point and inflating the tyre predictably resulted in a loss of sealant, then a seal holding air at around 50psi, but the plug of green rubber in the cut couldn't withstand higher pressures. Adding another 1.5oz of sealant and a bit of spinning the system held air overnight, including a nocturnal test ride, but the next morning a slight top-up of air resulted in a catherine-wheel of green spray as the bung failed again.

After some research on tubeless repair I opted for a traditional self-vulcanising Tip-Top patch from Rema. It was a new one on me, cleaning the inside of a tyre with iso alcohol then buffing, gluing and applying a patch, but there was a minimum of mess and the end result held air.

Arguably you could perform this repair on the road if you carried a sealed alcohol swab, patches, buffer and tube of glue – properly old-school and funny how things come full-circle. Given how rare actual punctures to tubeless tyres are, though, I think I'd prefer carrying and using a small puncture kit as opposed to a full inner tube. To fit a tube you'd have to remove the tubeless system valve as well as lose all your sealant, then still have to repair it back at home. Faff.

Both Slime and Schwalbe confirmed that so long as the area to be patched is clean, there's no reason using a normal inner tube vulcanised patch shouldn't be a permanent repair. You could possibly use a self-adhesive patch in a pinch, but I've never found these to hold air long-term and there's no guarantee the adhesive would play nicely with the Slime sealant.

In the round

Slime has made a specific design choice to put in less latex to keep the sealant fluid over time and CO2/freeze-proof, so a tyre that suits that design is needed – hence the One worked, the Sector didn't. If you've invested in a pair of Sectors you could use the Slime kit and add a bottle of latex-based sealant instead. The kit includes enough Slime Pro sealant to do four wheels, or two wheels twice. There's enough tape to do four wheels with one layer, but as above you really need two layers to be guaranteed a good seal.

So really, the kit is good for one set of wheels, done properly, with spare sealant left over for next year or a tyre change. You may well wear the tyre out before the sealant needs replacing – there's no definitive lifespan for the Slime Pro liquid. With latex-based sealants you can tell it's time after about three months as the fluid has dried into an unholy mess.

At £49.99 the kit brings together everything you need to go tubeless, if you have a tubeless tyre handy. Arguably you could source the valves, tape, sealant and inflators separately – but you won't save much if anything (you can buy the kit for around £40 if you shop around). And you won't know whether you need the CO2 canister until you do. The Microflate Nano is a very nice, small inflator in its own right, for which you twist the canister to turn the gas on/off. After half-using a canister two months ago, it's still charged.

The Slime Pro Tubeless kit is sensible money with clear instructions and still working (for me) perfectly 2,000km later. I'm now at the point of not taking pump/inner tube/levers on all but the longest of rides.

Just be aware of using a tyre without a butyl liner that then requires a different latex-based sealant. And consider taking a traditional patch kit and alcohol swab on expeditions. And pre-unpeen your valve cores.

Caveat everything.

Verdict

A sensible way to convert normal rims for tubeless use, with a few caveats and the right tyre.