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We know, there’s no such thing as a stupid question. But there are some questions you might not want to ask your local shop or riding buddies. AASQ is our weekly series where we get to the bottom of your questions – serious or otherwise. This one discusses the pros and cons (are there any?) of bolt thru-axles, floating axles, self-aligning axles and proper old school skewers. Hit the link at the bottom of the post to submit your own question.
The axle is an often over-looked bicycle component. It holds your wheels in, right? What else is there to know? Quite a lot, actually. First of all, axles comes in a tonne of different shapes and sizes to suit different spacing standards and bike designs. Tyler tells you everything you need to know about one type of axle, the thru-axle, in this video.
The price of axles can vary considerably too. What are you actually paying for? Are there performance advantages to be had with a more expensive axle? Now you hear there are ones that float too. And self-align. What do these things even mean? We sent these questions and more to the good guys at The Robert Axle Project and Burgtec to get some insight on the topic.
How does a floating axle work?
Robert Axle Project: I believe this is referring to the new Fox suspension lowers. Basically, the lowers on the fork can float (be adjusted) on the axle before being secured. The reason for this is to make up for manufacturing differences in what the industry used to call outer (over) lock nut dimensions.
So, long story short, the axle is not really floating at all. The fork lowers just allow for minor adjustments to make up for hub manufacturers being a little inconsistent. The only time you would do this with these new Fox forks is when you get a new hub.
There is no reason you would have to do it every time you removed your wheel. Once the fork is set for the given hub you are using you are good to go.
Burgtec: In essence it works exactly like any other axle. The slight difference is using a floating sleeve to achieve the spacing which is claimed to allow wheel removal and re-installation in the exact same spot.
Fox: The guys at Fox were a little too busy to send us an answer, but that’s OK. Their website has this explanation.
Floating axles might look similar to other axles, but in fact they offer a distinct performance advantage due to their unique ability to match the exact width of the fork’s wheel mounting surface precisely to the front hub flange spacing, thus creating perfect chassis alignment and eliminating unwanted friction between the upper and lower fork legs.
Floating axle on the new Fox 36 and Fox 38 enduro forks
Floating axles provide much smoother suspension movement throughout the entire range of the fork’s travel, notably improving sensitivity and overall ride quality.
The all-new 36 and 38 come equipped with a new quick-release lever operated patent-pending floating axle system, combining the benefit of a floating axle with the ease of a tool-free quick-release.
Fox offer the Kabolt-X floating axle system on their new enduro and DH forks
With this system, spacing is locked in via a floating sleeve, allowing repeated front wheel removal and re-installation while maintaining perfect fork alignment.
What is a self-aligning thru-axle, and do I really need one for enduro?
Burgtec: It’s definitely not essential for Enduro. Some brands use it and others don’t. If you’re changing wheels it’s always good practice to make sure your wheel spins properly with minimal friction and the brakes aren’t rubbing.
Enduro pro Mark Scott runs Burgtec thru-axles on his Santa Cruz Megatower – Pro Bike Check here. Photo by Sven Martin.
Robert Axle Project: I think this “self-aligning” thru-axle is referring to Syntace style axles that use a taper on the axle that meets a taper on the fork or frame. The industry markets this as a self-aligning axle but really it is not.
Tune showed a prototype self-aligning thru-axle at Eurobike in 2018
The only way it can truly be a self-aligning axle is if the drive side nut can float. Currently, most brands that use this style of axle do not use a floating nut on the drive side of the bike (Specialized). So, the axle is not truly self aligning. And no, this has not nothing to do with what the bike can be used for.
Why do enduro forks clamp just one side of the axle? Why isn’t there a clamp on both legs?
Burgtec: Clamps on Both legs is more of a DH thing where bikes always go back to the pits to be worked on. Enduro bikes are out in the hills all day and less bolts means less faff and more ride time.
The floating axle system on a Fox 40 downhill fork
Why did some early disc brake setups cause skewers to drop out? Was it a hub design issue or faulty skewers?
Burgtec: I think this was probably down to vibration. The most probable cause of these coming loose would be people not tightening them enough. That definitely happened to me a few times!
Bolt through systems that have been commonplace the last 10-15 years are a significant improvement to stiffness but can still come loose if not tightened appropriately.
Robert Axle Project: This comes down to a few different reasons. But, the big one is that folks really did not know how cam-actuated QRs really worked. If the lever is not all the way closed the cam is not doing its job.
When you grab a handful of brake it grabs the rotor which puts a ton of (rotating) downward force on the wheel. This action is what tries to pull the wheel out of the open dropout and why thru-axles are so important with disc brakes and make all the difference.
At the same time disc brakes were coming to market and bikes where getting bulkier which made it even harder for folks to work the QR lever correctly. Things like breezer-style dropouts and big bulky chainstays contributed to this.
People would close the QR lever and it would bottom out on the fork or frame not allowing the cam to close all the way. And of course there were variations in QR lever designs and quality which also played a role in this issue.
How much stiffer is a thru axle setup compared to a skewer axle?
Robert Axle Project: 1000%. But, really we have not measured this but I am sure some bigger companies have. We did not set out to replace the QR as the bike industry had already done that. Our goal was to make thru-axles easy to understand and compatible with your bike!
Check out how Steve saved 72g on his Trek Remedy by switching to Robert Axle Project thru-axles
We have tested our axles against most OEM and other aftermarket axles on the market currently. We currently meet or exceed all the parameters of thru-axles on the market. We do have customers report all the time that our thru-axle is stiffer than their stock thru-axle.
Customers report that brake rub on road bikes goes away after they switch to our axles. The constant outside diameter of our axles is stiffer than those designs which use a step down in the diameter to reduce weight, which is a weaker design.
Do XC racers still prefer skewers over thru axles? Seems to me it would take much longer to change a wheel with a thru axle.
Robert Axle Project: Are we talking real pros or just weekend racers? Pros race whatever they are paid to race to an extent. The time difference to change a wheel is very minimal and with tire plugs and tubeless setups this is not really a concern in XC racing.
A funky red, white and blue quick release skewer from Paul Components
The racing times are just too close for wheel changes as you would not be able to do it quick enough. Right? In pro road racing it definitely is and that is why you see axles like the Mavic Speed Release.
The Mavic Speed Release road bike thru-axle system is secure like a thru-axle but quick like a skewer
Sag cars are now carrying whole bikes to swap in the case of a mechanical or flat tire as they feel this is faster than doing a wheel swap with disc bikes that have thru axles. There is more of an issue with wheel compatibility and brake rotor alignment for wheel swaps to be viable in pro racing scenarios.
The Robert Axle Project make replacement thru-axles for Mavic Speed Release and Cervelo R.A.T. axles
Got a question of your own? Click here to use the AASQ form to submit questions on any cycling-related topic of your choice, and we’ll get the experts to answer them for you!
Jessie-May Morgan is the UK & Ireland Tech Editor of Bikerumor. She has been writing about Mountain Bike Riding and Racing, and all its weird and wonderful technology for 4 years. Prior to that, she was an Intern at the Mountain Bike Center of Scotland, and a Mountain Bike Coach and Leader in the Tweed Valley.
Based in Innerleithen, Scotland, Jessie-May can often be seen riding the Glentress Trail Center, and its neighboring Enduro and Downhill Tracks. She regularly competes in Enduro at a national level, and has recently competed on the World Stage at a handful of Enduro World Series events.
For Bikerumor, Jessie-May is testing the latest mountain bikes, equipment and kit, letting readers know what’s hot and what’s not.
For context, she weighs 60kg and stands at 5ft 4″ tall (163cm).
at no point does the article address the buoyance of axles. Tape up both ends and toss that thing in some water!!!
carlos
4 years ago
If you want a stiffer axle then machine it out of steel. Guess what? You won’t feel increased stiffness because that’s not a thru axles’s job. If you did feel increased stiffness then the hub and fork dropouts are underbuilt and you should buy something better.
Daniel M
4 years ago
Still getting by with 100/135 hub spacing and old-school QR axles on my disc brake bikes. If you know what you’re doing they work just fine.
Any time anyone makes a post about through axles or more gears, there’s always gotta be that one guy who says that they’ve still got the old version of whatever the article is about, and it works just fine. Thanks for your contribution.
Seraph, before drop outs, bikes had solid ends.
Forks and chain stays had holes in them just like a thru-axle fork.
You would spread the fork and pop the wheel in,
then do up the bolts. Hub axles had threads on them.
Just plain holes in the frame and fork, no threads to mess up.
Steel fork and bolted on rear triangles, made it possible.
Bicycles have gone to hell since the introduction of the pneumatic tyre.
Harummphhhh.
Frank
4 years ago
Make that two guys. I too still use a disc bike with quick-release and 135mm rear. Works fine and gives better chain alighment with the narrow Q-factor cranks I prefer.
Older stuff does not become suddenly unusable when something new shows up. If you are an engineer or designer you will understand that product design always involves compromises, you gain something but also lose something with each evolution of a product. Hopefully products hit a balance that satisfies most of the target demographic but each of us is different and an individual may not be well served by a newer product compared to its predecessor. This is especially the case if one has been in this for a long time and has developed a mature understanding of their needs and of how innovation tends to play out long term.
Nickolas
3 years ago
I feel that two points about quick releases and disc brakes were omitted here. Those being the popularity of lightweight external-cam quick release levers and the geometry of the dropout opening when road disc but the scene.
External cam quick release levers often used a nylon cam that was easy to deform if overtightened and was not capable of the same clamping force as all-metal cams at proper torque.
Braking forces will push the axle in the opposite direction to which the rotor enters the caliper. On many frames and forks, that interaction resulted in the axle being pushed towards the opening in the dropouts.
A good quick release, dropout selection, and caliper location does much to mitigate these issues. However, all of the above may slow down wheel changes, mitigating the benefits of QR, and require more knowledge by the end user to give wheel security. For these reasons thru axles have become more common.
I’ll save comments on floating axles for another time.
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