GUP's Kwiki, a 'Quick-Fix Sealant & Inflator', is precisely that: a 125ml combination of latex sealant and CO2 which works to the 'spare tyre in a can' narrative, theoretically mending the puncture and re-inflating the tyre in one, rather like those kits supplied with some new cars. Performance is pretty good – to a point.
It certainly seals small holes, and managed to raise a flat 700x38 tube to 90psi within 20 seconds. It's vastly superior to similar concepts I've used. However, it's not foolproof and, in common with some sealant-based products in my experience, holes around the millimetre mark are its limit.
Each 125ml canister has a smart head, designed for plug 'n' play convenience with Presta or Schrader valves. Butane propellant works with the CO2 component to deliver the liquid latex sealant and inflate the tyre.
To use, give the GUP a quick shake to agitate and mix the contents, pop the cap and push its yellow connector firmly onto your open valve while pressing the can to deliver. In common with many CO2 cartridges these days, the delivery is very controllable – just back off slightly and it will ease up. This greatly reduces the likelihood of over-inflating or, worse still, blowing the tube to smithereens.
As with other goo-filled products, spin the wheel to traffic that latex where it's needed. All things being equal, you are now ready to scoot off.
Provided you've done the preliminaries and the hole is a reasonable distance from the valve stem, happy days! The contents are pretty generous, so you're good for 90-120psi. Others I've used have managed only around 65, which is adequate for getting home on but optimal pressures are always better. In fact, there was a reasonable bit left over in the can after resuscitating the 38mm Soma.
As an experiment, I delivered the remainder into a pinch flatted but otherwise serviceable spare tube, just to see if the GUP was single use or would self-heal later down the line. Obviously, this resulted in some unwanted pressure and I needed to rotate the tube rapidly. Nonetheless, latex had been delivered and the snake-bite healed.
Several weeks and around 250 miles later, the GUP-treated butyl is serving me very reliably, and the other tube also seems to be holding up.
It's not a magic bullet for all punctures, though, and I'd caution double checking for ruinous holes/damage before use. Having swapped over to my dynamo wheel for nocturnal meandering, I discovered the front tyre (a Panaracer T-Serv Protite) as flat as the proverbial, with nothing obvious embedded in the casing.
Bike hoisted into workstand, valve open, GUP deployed as before... All was going to plan, then 15 seconds in there was an almighty sputtering from the tyre and I was engulfed in a torrent of white goo. Closer investigation revealed the butyl had perished around the valve stem.
In certain contexts, the GUP is super-convenient and a godsend, but it also has some limitations and is expensive compared with alternatives: B'Twin's inflator and CO2 cartridge plus an impregnated latex tube for £12, for example, or a CO2 inflator and sealant for a couple of quid more.
Super-convenient at certain times but not a magic bullet for all punctures, and pricey compared with alternatives
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road.cc test report
Make and model: GUP Kwiki Sealant & Inflator
Size tested: 125ml
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?
GUP Industries says, "Flats are no problem with GÜP. It seals and inflates your tire in seconds. No extra tools needed. No need to remove your wheel. You'll be back on your ride in no time."
It's brilliant in some contexts but not others: punctures bigger than a millimetre, and those close to the valve are two exceptions. In keeping with most sealant-based products, it proved very messy.
Tell us some more about the technical aspects of the product?
125ml Latex sealant, propellant and CO2 mix.
Very effective in certain contexts, and potentially a real godsend, but not a miracle cure.
Convenience aside, a store-branded CO2 inflator, cartridge and spare tube can be had for similar money and are, in my experience, a more dependable solution.
Tell us how the product performed overall when used for its designed purpose
Quite well in some contexts, and in ideal conditions an absolute godsend. However, it's dependent upon the "right" type of puncture. Get one close to the valve, or one that's more savage than first thought and you could be left with a big, sticky mess.
Tell us what you particularly liked about the product
Really convenient, when they work.
Tell us what you particularly disliked about the product
Expensive, not something I'd want to rely (solely) on either.
Did you enjoy using the product? Yes
Would you consider buying the product? No
Would you recommend the product to a friend? In certain contexts, possibly.
Use this box to explain your overall score
It's excellent when it works, but although it's quicker than a tube swap and CO2 inflator, it's also less reliable and expensive for a single-use product.
About the tester
I usually ride: Rough Stuff Tourer Based around 4130 Univega mtb Frameset My best bike is: 1955 Holdsworth Road Path and several others including cross & traditional road
I've been riding for: Over 20 years I ride: Most days I would class myself as: Experienced
I regularly do the following types of riding: cyclo-cross, commuting, touring, fixed/singlespeed, mountain biking
Shaun Audane is a freelance writer/product tester with over twenty-eight years riding experience, the last twelve (120,000 miles) spent putting bikes and kit through their paces for a variety of publications. Previous generations of his family worked at manufacturing's sharp end, thus Shaun can weld, has a sound understanding of frame building practice and a preference for steel or titanium framesets.
Citing Richard Ballantine and an Au pair as his earliest cycling influences, he is presently writing a cycling book with particular focus upon women, families and disabled audiences (Having been a registered care manager and coached children at Herne Hill Velodrome in earlier careers)