Do MTB Thru-Axles Need an Upgrade? Robert Axle Project Makes the Case

Robert Axle Project King Thru Axles are lightweight and simple, plus they add a pop of color to any build.

To be honest, I haven’t paid much attention to thru axles. Up until this point I’ve just used whatever came attached to my bike and fork.

Of course everything can be upgraded, from your morning coffee to the pillow you lay on at night, and MTB axles are no different. There are thru axles, and then there are Robert Axle Project King Thru Axles. Priced at $65 each, these aren’t cheap, but as I’ve found, there is a case to be made for an upgrade.

Robert Axle Project King Thru Axle specs

  • Front: 15x158mm with M15x1.5mm thread
  • Rear: 12×167mm or 12x172mm with 1.0mm thread
  • Weight: 47.6g (front), 39.1g (rear)
  • Colors: Black, 3D Violet, and Turquoise
  • Price: $65 each
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A low-profile axle

Many of the mountain bike axles that come with forks and frames feature a quick-release lever which makes for a handy, tool-free way to remove a wheel. However those levers stick out and can get snagged on the trail. The Robert Axle Project King Thru Axle utilizes a much simpler design with a flat head and zero moving parts.

Both the front and rear axle can be removed using a 6mm hex tool. On my other bike, a hardtail, one of my axles needs a 5mm, and the other needs a 6mm, and I can never remember which is which. For that reason it’s nice to have matching hardware.

They could save weight

Depending on the axle(s) you’re upgrading, a Robert Axle Project King Thru Axle could save weight. Obviously QR-style axles and axles with built-in handles like the Canyon Quixle I replaced have more parts and are therefore heavier. How much heavier? The Quixle on my Canyon Neuron weighs 54.3g compared to 39.1g for the Robert Axle Project King Thru Axle, which is about 30% less.

My Rockshox Pike Ultimate fork, however, uses a Maxle Stealth axle that weighs several grams less than the Robert Axle Project replacement. For those who are running a quality fork with a lever-free axle, the weight savings (or lack thereof) probably aren’t compelling enough to swap. While my Pike has a nice lightweight axle already, another RockShox fork I own came with an axle that weighs 73.5g compared to the 47.6g King Thru Axle.

I haven’t snapped or bent an axle since the days of 9mm QR axles, so I don’t think there’s necessarily a need for a more robust thru axle, though the 7075 aluminum Robert Axle Project offerings do appear to be very well made and are confidence inspiring. My last thru axle got stripped (uh, by me) and I don’t think that will happen with these. They’re clearly machined to a precise degree, and looking at one straight on is like staring down the barrel of a high-quality rifle.

Two things make these Robert Axle Project axles “Kings”: the color and the shape. On the color front, I was curious whether the anodized coating would scratch but after a couple hundred miles of off-road riding I haven’t found any blemishes on the caps or even the axle itself. I tested both axles with two different wheelsets and to no one’s surprise, I had zero issues.

I don’t own any Chris King components, but I do like being able to add pops of color to my build in unexpected (and subtle) places. I chose the Turquoise color shown here to match a prized Snake Creek Gap Time Trial stem cap.

As far as the shape goes, I guess I didn’t realize Chris King had such a distinctive stem cap style but apparently they do. The raised center is a subtle touch and one that clearly shows an attention to detail.

Now, about the price. Unless you’ve lost an axle, you probably have no idea what they cost. My good friend Jim Hodgson lost his axle once and had to pay $75 for one while he waited weeks for it to be delivered just so he could ride his bike. (Similarly the Canyon Quixle axle I stripped has been “out of stock” for months.) Replacement axles from RockShox and Fox go for about $40 to $60, so the $65 Robert Axle Project does represent a price premium. For some I suspect the look alone is worth spending a few bucks extra.

The Robert Axle Project website has a convenient online tool that makes it easy to find the axle that fits your bike or fork. In addition to regular MTB thru axles like the ones I tested, they also offer a number of specialty axles for attaching bike trailers, tandems, and trainers.

Pros and cons of the Robert Axle Project King Thru Axle


  • Saves weight over an axle with built-in lever
  • No moving parts to break or snag
  • Works with a simple 6mm hex tool
  • Nice way to add color to a build


  • Expensive

Bottom line

The Robert Axle Project King Thru Axle is a colorful, quality upgrade that’s a good choice if you’re replacing a lost axle and is also worth a look if you want to save weight and simplify your bike at the same time.