Every day, another mountain biker discovers the relative flat-proof joy of riding tubeless tires. A couple of months later, they discover how much of a pain in the rear tubeless tires are to install onto a rim without the proper equipment. For those without an air compressor and the patience of a monk, what was once a 10-minute job now results in going down some YouTube wormhole on how to McGyver some useless contraption using baking soda, a floor pump, duct tape, and a soda bottle to seat a tire bead. Luckily, the Bontrager Flash Charger came to the rescue. It has its quirks; mainly the way it steals air from tires before asking your triceps to put it back where it belongs. We don't really like the gauge with its broad pressure measurements and small font. The head has a delicate feel to it, but it seals tight and fits any valve without moving around parts. It'll set you back a Benjamin, but it might be the most practical hundo you ever spend.
No outlet? No problem. The FLASHcharger makes tubeless tire installation possible without an air compressor. We weren't crazy about it stealing air from our tires when used as a regular pump though.
Comparatively, this is a big pump. Luckily, it features a metal, 3-legged base wide enough to prevent it from falling over and breaking toes; there is no rubber or plastic on the base where it contacts the ground. Scratching of delicate surfaces is especially likely with this pump because of its significant weight. The polished alloy cylinder and meaty compressor cylinder rest in a plastic cradle atop the base, which is secured by a plastic mounting plate on the underside of the base. Given the significant amount of force it takes to fill the second chamber to 160 psi, metal would have been a more welcome choice for this part. However, the cradle is significantly recessed, allowing the barrels to fit securely and deeply enough to prevent unwanted movement.
Even though you keep your bike in the living room, you should pump up the tires outside and not on the wooden floors.
Ease of Attachment/Detachment
The "auto-select" head fits both Schrader and Presta valves without unthreading or flip-flopping internal pieces around. The head is entirely plastic; although the long lever made it easier to secure the head to the valve, it felt a bit delicate and thin for our liking.
The auto-select head was easy enough to figure out but we would have liked more metal. The thin lever felt especially brittle.
Although we can appreciate the user-friendliness of a single auto-select head, this design may wear out a bit faster than those heads with separate ports for each type of valve. Ours still sealed tight onto valves by the end of our testing period, but it was bit chewed up. Pumps of this sort are still relatively new, and we found ourselves lending it out quite often to friends replacing tires that didn't have access to an air compressor.
Despite the gauge being mounted towards the top of the pump, the minuscule type and brushed metallic background proved difficult to read for many testers. No chronograph dial could be set beforehand if reading the dial is difficult. The diameter of the gauge inside the housing is less than two inches and our biggest gripe was with the spacing. Displayed in increments of 20 psi, this was far too generous to obtain a reading with much accuracy. The red lever that is contoured to the shape of the gauge (and flips up and down to activate the pressurized chamber) is made of plastic and often the first thing to hit the ground when the unit is pushed over.
With pressure measurements labeled every 20 psi, we found getting a precise reading to be very difficult.
The hose on this contender is 42 inches long. It attaches towards the top of the pump, which makes filling both tires possible without moving the pump around. For such a large pump, we expected this to be one of the fastest pumps in the test, and we were surprised when it placed towards the bottom of the barrel in our tests. When connecting the auto-select head to the tire valve, the pump fills with air from inside the tire. The long hose and large barrel suck out a ridiculous amount of air, leaving the tire at a much lower starting pressure. As a result, simply topping off a tire turns into a full-fledged pump fest. Think we're kidding? A road tire starting 100 psi dropped to 40 psi when we hooked up the Flash Charger. It required 35 pumps to get the pressure back to 100 psi where we started! When you disconnect the hose from the tire, all the air escapes from the pump, and the hose hisses at you for 10 seconds like a Cobra poised to strike.
The Flash Charger in normal pump mode on the right. When filling the high-pressure chamber, flip the red handle down and fill to 160 psi.
In everyday use, accuracy is difficult to determine with this pump. Due to the spacing of pressure values on the gauge, readings are often a best guess, especially on road tires. The lower values between 10 and 40 psi typically encountered with mountain bike tires are spaced 10 psi apart (i.e. 10,20,30,40) and can be read with better accuracy. Past 40 psi, pressure values are given in increments of 20 with no intermediate markings. Thankfully, we chose even pressure values for our testing, which were marked on the gauge. This pump was consistently accurate to within a couple psi; however, in the real world, we feel accurate pressure readings will pose a much greater challenge.
This pump's strength lies in the application of seating tubeless tires. We successfully seated numerous tubeless tire combinations, including 27.5 inch, 29 inch, fat bike, plus, and cyclocross tires. If you don't have access to or don't wish to purchase an air compressor, these pumps are the next best choice. On a past mountain biking trip to Gooseberry Mesa, where a buddy blew out the sidewall on his rear tire, having the Flash Charger at camp would have saved him a long drive into town.
At around 120 dollars and recently on sale for 99 dollars on Trek's website, this tubeless-ready pump is significantly cheaper than the other compressor-type pump we tested, the Topeak Joe Blow Booster. The Flash Charger was just as successful at seating the bead on tubeless tires; innovation costs money and Bontrager effectively keeps the cost of this pump down by using plastic parts on the head, handle and compressor chamber lever. Those in the market for a pump that costs 100 plus dollars might be willing to spend a few extra bucks to get more metal on such high-use pieces of the pump.
Our arms were ready to fall off from all the pumping required to test bike pumps. Having already recouped the money on having bike shops install our tubeless tires, we're definitely digging on these style pumps that act as air compressors. With this pump, we really couldn't get over the amount of air drawn out of the tire when attaching the hose. To make matters worse, the extra effort required to regain our starting pressure and fill the tire further was blown in our face when we detached the hose.