I have long been a fan of the original Gravelking SK in 700x38c. They provide good traction on everything but mud and are pretty much indestructible. The only downsides were that they make a lot of noise and feel like slugs on pavement. I recently built up a frame that has room for 50mm tires, so I entered the massive cloudy world of gravel tire choices. For a few weeks, I had so many tires rotate in and out of my cart, I read and watched reviews, asked friends, etc. I went the low weight route, I went the heavy duty route, I went the low rolling resistance route, then finally returned to my senses and asked myself what was important in a tire. I wanted a robust tire that performed well on and off road, looked nice, and wasn't going to leave me on the side of the road fitting a tube into a tire full of snot.
Enter the Gravelking X1 in 700x45c. These things are excellent! Mounting happened with my thumbs, bead seating happened with a floor pump, and they hold air forever. They roll very very well on pavement - a very noticeable improvement over their SK predecessor, they grip chunky gravel beautifully, they're wide (48mm on 26mm internal rims) so they do well in sugar sand so long as you maintain power, and they are quiet! Weight is fine. They aren't light, but they aren't dogs either. I've driven these things over all types of surfaces while not being too picky in line selection, and they look damn near brand new. I can't comment on mud yet, but judging by the tread, I can't imagine they're much better than the SK.
If you run these tires, you have to get the pressure right. After a bunch of trial and error, a good starting point would be to take the pressure you run now and let out a heap of air. I weigh 195 lbs and run the 700x38 SKs at 30-35. The 700x45 X1s are happy at 16-20. Any more than that and they aren't comfortable at all - like full of concrete feeling.
Buy these if you want a tire that performs pretty much perfectly which you don't have to worry about.
When Silca first release this it was met with some blowback based on the price, especially compared to brand x options at roughly 20% the price. Might as well compare Dura Ace to Sora. This is priced at the higher end of any TPU tube but there are design/quality/performance benefits and you may appreciate or discount those values accordingly.
I've tried TPU tubes over the years and generally found found issues that prevent me from being comfortable using them. #1 is flimsy/cheap plastic valve, poorly bonded to the tube. This makes them prone to to leaks and without a retaining nut even the simple act of pressing on a pump head to top off before a ride stresses that valve/tube and can lead to failure. #2 is that the valve itself is often bonded instead of threaded and therefore opening/closing can break that bond.
The Silca design addresses every issue I've ever had (and they have a nifty intro video on YouTube covering this). The valve stem is full metal, threaded. If you're familiar with tubeless, you realize that itself is roughly half the selling price of this tube. It's also got a metal reinforcement plate against the inside of the rim and a retaining nut for the outside to secure the tube. Silca additionally uses a special (patented) welding process for the tube seam that appears to be more reliable than competitor's designs.
There's also one "marginal gain" aspect of the design I was not aware of until I researched it more - the tube color (or lack thereof). Those low price brand-x tubes come in varying bright/obnoxious colors, which I'd considered harmless since the tube is hidden inside the tire. That color comes by adding powder to the TPU mix (which is, at base, colorless). That additive actually reduces the performance of the TPU, making it stiffer, less expansive when inflating, and adds rolling resistance. You'll likely never notice the difference, but it does make one wonder why the manufacturer would be adding cost to the product and process that serves no functional purpose and actually hurts performance a bit.
So haters can hate, but I've finally found a TPU tube that's high performance, high quality, easy/reliable, and I'm actually converting all my bikes BACK from tubeless to using these TPU tubes. The higher price, to me, is consistent with the higher quality and performance that I consider necessary. I will concede, though, that I think these may be overkill/overpriced for carrying as a spare tube whose primary purpose is to get me back home, which seems like a perfectly fine scenario for those brand-x options (even if it means I carry 2 in order to be assured that one will hopefully work).
Excellent tires- I opted for the 50mm size and couldn't be happier. Have about 500mi on mine, so time will tell about durability, but they seem great so far. Supple, very quick rolling, and reasonably grippy on all but singletrack/loose leaves/super chunky gravel.
I raced these in a gravel race where numerous folks running the G-One RS flatted, and I had absolutely no issues, so I have to believe the added center knobs help slightly with puncture resistance on sharper gravel.
I didn't buy a 40mm endurance tire expecting them to be fast but these things are brutally slower than the Conti All Seasons I traded them for. Only inflated up to about 38mm so for only an extra 3mm and all that extra rolling resistance and weight, I think going back to 35 All Seasons may be in my future. That said, these things might go great on my fully commuter rig if I want a slick for the city since they feel bomb proof and can't be much slower than the Cinturato M knobbies I have on it now.
