First impressions: Panaracer Gravel King SK tires, 700C x 38 mm

After having ridden at my familiar southern stomping grounds for years, it’s funny that I had never properly discovered the hidden trail network that ran through it and clandestinely intersected the roads I’d spent so much time on. An opportunity to ride with folks who knew about these ribbons of singletrack finally popped up, and so I felt I needed to prepare for it.

That preparation means more suitable rubber. As good as my American Classic Timekeepers are, they simply aren’t cut out for taking on trails. With my last set of knobby tires long since disintegrated, and with so many more options available in light of the gravel cycling boom, I thought I should sample one of them to get my trail-riding feet wet again.

With my budget a little tight and me unwilling to spend obscene amounts on tires I might not end up using frequently, I went with Panaracer’s long-running Gravel King SKs. I got my pair from online seller/importer Cycle Meeting for PhP3,800, or about PhP1,900 (~US$35) apiece, which is not too shabby considering many other gravel tire options go for PhP4,000 on their own. The 700C x 38 mm advertised size (which, strangely, differs from the ISO/ETRTO listed size of “40-622”) should fit into Hyro’s frame and fork. These newer gravel tires seem to have better reconciled the differing demands of riding on the road and grip on the rough stuff, although due to the word “gravel” really meaning different surfaces to different people and locations, no single tire will work for everyone’s riding as it’s all points on a fairly wide spectrum.

This is not my first dance with Panaracer rubber. Previously I had a pair of Fairweather For Traveller tires, which they produced in collaboration with Tokyo bike shop Blue Lug, and are basically the herringbone-tread Gravel King slick tires in disguise. These, however, are tubeless compatible, and have a tread pattern made up of square knobs and ridges – hence the “SK” designation, to differentiate them from the four other tread patterns in the Gravel King lineup.

True to Panaracer’s reputation and my previous experience, these tires were a pain to mount to my wheels and set up tubeless. Like the Fairweather tires before them, the SKs had tough, stubborn beads that made hoiking them over my rims a chore – slightly less so than the Fairweathers, but nowhere near as easy as with the Timekeepers. Worse, when they were finally inside the rim bed, they were a baggy fit, which undermined their tubeless set-up capability. I charged up my Bontrager Flash Charger pump to 160 psi about four or five times to seat them, only to be greeted with just a hiss of leaking air. When the sweet pops of success came, it was only after I had laid down five or six layers of tubeless rim tape, as opposed to the two or three the Timekeepers needed. As this is only my second rodeo with tubeless bike tires, this added setup length may have been due to the much larger volume on these 38 mm rubbers.

Fresh Orange Seal Endurance sealant injected and 42 psi of air pumped in, I rode them around the village for two laps to saturate the SKs’ tire carcasses with sealant, and to get a few ride impressions on pavement.

Hyro’s original footwear: Schwalbe Super Swan 700C x 35 mm mud knobbies. Photo circa 2016

For my ride impressions to have sufficient context, I feel like I have to make comparisons with Hyro’s original tires. They were Schwalbe Super Swan 700C x 35 mm knobbies meant for use in the mud – and they themselves are simply a narrow-carcass variant of the Rocket Ron mountain bike tire. Hyro is a cyclocross bike, after all – essentially the prototypical gravel bike when the gravel bike category was just a pipe dream.

In the few times I rode them on pavement and asphalt, they were not my favorite. The steam-roller effect of the larger tire size was an interesting novelty compared to the 28 mm slicks I usually ride, simply rolling over ruts and road acne, but everything else about the Super Swans was terrible away from the trails. Steering response felt sluggish and ponderous, and the wide voids in between tread blocks meant I couldn’t really lean into turns and shift my weight very well. Inertia from a standing start was rather bad, too. Away from the mud, the Super Swans gave Hyro a distinctly “straight and upright is best” riding style that felt very alien to me and my roadie predilections.

By comparison, the SKs benefit from almost ten years of gravel tire refinement over the Super Swans, and they feel like a much better dual-purpose tire. The design trend towards a dense center tread, combined with more aggressive lugs toward the tread shoulders, makes for much better steering response on the street. Tubeless tire technology finally delivers on the promises the Super Swan’s 35 mm width simply hinted at; where those tires couldn’t be run below 60 psi, at 42 psi the SKs deliver a distinctly more balloon-like cushiony ride quality.

The jury’s out on how much heavier these will be to spin up, as the SK’s much larger carcass compared to a 28 mm slick also means the whole bike has larger tire circumference and is effectively geared harder like-for-like. It also remains to be seen how well these tires will behave on that long-hidden singletrack. I’ll have two upcoming rides to see for myself. In the meantime, I am mildly impressed so far.

The tubeless transition: Some months after

About five months after committing to tubeless tire tech and making the conversion, I decided to top up the sealant in the American Classic Timekeeper tires. It was also a good time to address the little annoyances I had with the entire tubeless setup thus far, and evaluate the technology as a whole.

As far as tire pressures go, I started with the ETRTO’s 73 psi maximum prescribed for tubeless wheels without rim hooks, even though my H Plus Son The Hydra rims come with them. I simply figured it would be a good start point. With more rides under my belt, I’ve brought my tire pressures down to the 60-65 psi level, which introduces more ride comfort without any other vices. I might still experiment with lower pressures, but this is good for me.

In the interim, I grabbed a pair of longer 45 mm tubeless valves from WTB, and swapped out the old Stan’s 35 mm units. Removing the old valves and getting them unseated from their holes was a slight chore, but it also meant that they were as airtight as could be.

With the tire bead popped off the wheels to swap valves, I took a cursory glance at the inside of the tires. They were lined with sticky, dried-up Orange Seal Endurance sealant. I didn’t do any cleanup of old sealant; I peeled off only a little from the tire just to see how sticky it was. There was none of the problems Shane Miller had with the tire beads sticking to themselves due to the sealant. I injected another 40 mL of Orange Seal Endurance per tire, charged up my Bontrager TLR Flash Charger 2.0 pump to 160 psi, then let rip.

The added 10 mm of Presta valve length meant the pump had much better purchase on it for inflation, lessening the chances of its valve chuck spontaneously blowing itself off the valve. The front tire seated and successfully held air the first time. The rear, I had to seat twice after a slow leak, but otherwise went just as well.

All this is to say – I’m now a firm believer in tubeless tires for road bicycles. A lot of it is investing in the right tools and supplies, and part of it is also how well your tires and wheels play with each other. I have not yet suffered a puncture on this setup (touch wood), and the sealant maintenance aspect is a bit of a downer, but I suppose that’s also going to encourage me to ride outdoors more often.

Review: Bontrager TLR Flash Charger 2.0 track pump and tubeless inflator

A while back, I documented my dalliances with tubeless tires and my transition over to them. As with many new technologies, sometimes an investment in new tools is needed for the best chances of success. One of the tools I went with for my tubeless experiment, and perhaps the costliest of them all, is Bontrager’s TLR Flash Charger 2.0 track pump. I went over its use a little in a previous post, but today I’ll give you a more in-depth look of this thing.


  • Dual-chamber design
    • “Charge” setting stores a 160 psi burst of air for seating tubeless tires onto wheels
    • “Inflate” setting works like a normal track pump
  • Digital pressure gauge, max reading 160 psi, blue backlight, powered by one CR2032 battery
  • Pressure display switchable between psi and bar
  • Valve chuck compatible with both Presta and Schrader valves
  • Inflation accessories for balls and inflatables stored in handle
  • Solid metal tripod base and overall construction
  • Retail price: US$155


Dispelling any doubts as to who made this mammajamma…

One look at this thing tells you this really isn’t your typical plastic floor pump. That impression is reinforced when you hold it and lift it off the ground. The Flash Charger is reassuringly heavy. I’ve had a Giyo GF-42G for a few years now, and that looks and feels like a toy compared to this honker. Carelessly swinging it around overhead, the Flash Charger could double as some sort of blunt trauma melee weapon which wouldn’t break in half at the first strike.

The Flash Charger has to do the basic boring floor pump jobs first, so let’s talk about those. If you have basketballs, footballs, or an inflatable you or your kid(s) use by the pool, Bontrager has you covered. The needle and cone adapters for inflating those are included, and they live in a neat gray caddy that hides away inside the handle. This comes out a little too readily for my liking, but it’s the best way I’ve seen so far to have these adapters easily on hand and not lose them or forget where they are.

The Flash Charger 2.0 comes with a digital pressure gauge, an upgrade from the now-discontinued original. Bontrager thoughtfully bestowed the gauge resolution down to 0.1 psi, which is great for low-pressure, high-volume applications such as fat bikes, mountain bikes, and cyclocross. On the barrel of the pump just above the gauge is a bleed valve button, and the gauge can be used to fine-tune the pressure this way. The blue backlight is annoying, but that’s a personal nitpick. The way you use the lone button also takes a bit of getting used to. You press and hold it in to turn it on, then once you are done you press it again until the gauge says “OFF” – then leave it. If you press the button again while it says “OFF” it will switch units from psi to bar.

The special sauce of the Flash Charger 2.0 is in its dual-barrel construction. One barrel is for inflation, while the other is for holding up to 160 psi of air. This can then be released in a single burst to instantaneously push tubeless tire beads against their wheel rims and seat them. Bontrager touts that this does away with the need for an air compressor, and they were one of the first to market with this concept with the original Flash Charger.

You charge up the secondary barrel by flipping this shorter switch on the left to the “Charge” position. On the other side of the barrel, the longer switch on the right should be set to “Fill Tank,” then pump away. It’ll take me about 60 strokes to get the barrel charged to 160 psi, which says quite a bit about how much air this pump moves and how efficiently it does so.

The 0.1 psi resolution goes away once you pass 100 psi; at that point you don’t need it anymore.

Once pressurized, press the valve chuck onto the wheel’s valve and lock it in. On a Presta valve application, I had greater chances of successfully seating a tubeless tire if I removed the valve core beforehand. Then flip that big red lever on the right to “Release Pressure.”

Having had tire blowouts at home before, I was a little scared of this part of the operation because high-pressure tire blowouts sound remarkably like gunshots. But no, this was more uneventful than I thought. The Flash Charger itself exhibited no signs of creaking, straining, or other funny noises – just the whoosh of a lot of air once the big red lever is flicked open. You will slowly lose a bit of that charged-up air inside the pump if you wait around for too long before you release it, though. That lack of drama was reassuring because I had to repeat this charging and releasing of 160 psi air multiple times to get my tires to seat properly.

If there is one weakness to this pump, perhaps it’s in the valve chuck. Like many modern pumps, it will automatically accept both Presta and Schrader valves, which is a huge usability advantage over the Giyo GF-42G. On that pump, you need to basically disassemble the valve chuck, flip around two pieces according to which valve you’re inflating, and rebuild it. On this, I just push it on and flip the lever up.

Unfortunately the valve chuck’s ultimate grip on the valve leaves something to be desired. This is especially apparent on my 35 mm Stan’s tubeless Presta valves, which admittedly might be on the short side. The valve chuck has trouble staying on those by itself, needing a helping hand especially when I reinflate my tubeless tires to about 73 psi. Without assistance, the valve chuck literally blows off the valve at 63-65 psi. It does work better on the valves on inner tubes; my indoor training wheel has a Continental inner tube with a 45 mm Presta valve, and it holds on well enough on that as I pump it up to 100 psi. Your mileage may vary, perhaps, with the valves you use this pump with.


There’s no getting around it – $155 (PhP7,955) is a luxurious price for a track pump, especially when Chris Sports can now sell you a similar Beto tubeless track pump for a fraction of the price. That said, Bontrager’s TLR Flash Charger 2.0 does feel like a high-quality item, going quite a ways into justifying its cost by its sheer solidity and well-throught-out features (that higher-resolution digital pressure gauge is hard to beat). It’s easier to rationalize its purchase as a home mechanic’s shop tool expected to last years. I’m fairly confident this will last me quite a while – and that may be money well spent.