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Discussion Starter #1 (Edited)
How is through axle stiffer than QR?

Through axle is an idiotic design - one of several that have become popular in bicycles over the last two decades.

People talk about the stiffness of the through-axle system because it's thicker. That's horseshit. Such arguments show a complete lack of understanding of the forces involved. Every Tom Dick and Harry who builds products for bikes assumes that bigger diameter automatically equates to greater stiffness. This is reliably true for tubes. But not everything else.

First, the skinny quick release skewer doesn't support any weight to begin with. Its sole purpose is to squeeze the hub and dropouts together and keep everything in place via friction, hence, it need only have significant tensile strength, not stiffness. The hub itself has an axle of its own on which the dropout sits. It supports the dropouts vertically. While this QR axle is still narrower than the through-axle skewer, it also does not dictate the stiffness of the hub-dropout connection. When squeezed together with the skewer, the larger face of the hub's axle pressed against the inner surface of the dropout is large, as are the faces of the skewer's cam and acorn nut. The SURFACE AREA being squeezed against the dropouts is what ensures that the hub is held in place and unable to move relative to the dropouts, and vice versa. This is what dictates the stiffness of the system. It has absolutely nothing to do with the diameter of the axle traversing the dropouts.

Furthermore, thru axles must be screwed into place. And anyone with two connecting neurons knows that a cam is a vastly more secure method of maintaining tightness than a screw. The through axle by definition depends on screwing the thing tight enough to create significant friction between the axle and the dropout, which is more difficult to do. It also will produce more damage to the dropout each time it's screwed and unscrewed. A cam merely presses against the dropout.
 

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Adorable Furry Hombre
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People talk about the stiffness of the through-axle system because it's thicker. I don't get it. It doesn't make sense.
The quick release skewer doesn't support any weight to begin with. Its sole purpose is to squeeze the hub and dropouts together and keep everything in place via friction. The hub itself has an axle of its own, on which the deop


Short answer: it isn't just the axle, it is how the system interlocks the frame which results in a stronger system....which becomes a bigger deal as you do rougher terrain. Of course, the simple-stupid disc-brake alignment is a nice thing as well.

Everything you need to know about Thru Axles - The Buzz
 

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I have two very similar bikes. BMC Gran Fondo GF-01 (QR) and BMC RoadMachine RM-01 (12mm Thru Axles).

I'm a big guy (6' 5", 225lbs). I have an otherwise identical set of wheels for each bike (HED Belgium Plus on White Industries hubs, 25mm GP4000IIs tires, same inflation). I think the most obvious place I notice the thru-axles is in tracking on the high speed corners. I'm not sure I can explain why exactly, and some of it could be down to (very minor) geometry differences, but the Road Machine just feels much more locked in and steady on a high speed descending corner, and it's very noticeable.
 

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Discussion Starter #6 (Edited)
My through axles don't have cams.

But even if they did, my point would remain the same.

Think about the connection points between the axle and dropout.

The actual axle of a QR hub (ie the center around which the hub/spoke/wheel rotates) is actually quite large, and this is what is pressed tightly against the inner surface of the dropout. The small extension that sits in the dropout merely suspends the dropout on the hub. But The stiffness comes from the large area of interface between the face of the hub axle and faces of the dropout.

Does anyone have any PROOF that through axle is stiffer? Research?
 

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Adorable Furry Hombre
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Through axle is an idiotic design - one of several that have become popular in bicycles over the last two decades.

People talk about the stiffness of the through-axle system because it's thicker. That's horseshit. Such arguments show a complete lack of understanding of the forces involved. Every Tom Dick and Harry who builds products for bikes assumes that bigger diameter automatically equates to greater stiffness. This is reliably true for tubes. But not everything else.

First, the skinny quick release skewer doesn't support any weight to begin with. Its sole purpose is to squeeze the hub and dropouts together and keep everything in place via friction, hence, it need only have significant tensile strength, not stiffness. The hub itself has an axle of its own on which the dropout sits. It supports the dropouts vertically. While this QR axle is still narrower than the through-axle skewer, it also does not dictate the stiffness of the hub-dropout connection. When squeezed together with the skewer, the larger face of the hub's axle pressed against the inner surface of the dropout is large, as are the faces of the skewer's cam and acorn nut. The SURFACE AREA being squeezed against the dropouts is what ensures that the hub is held in place and unable to move relative to the dropouts, and vice versa. This is what dictates the stiffness of the system. It has absolutely nothing to do with the diameter of the axle traversing the dropouts.

Furthermore, thru axles must be screwed into place. And anyone with two connecting neurons knows that a cam is a vastly more secure method of maintaining tightness than a screw. The through axle by definition depends on screwing the thing tight enough to create significant friction between the axle and the dropout, which is more difficult to do. It also will produce more damage to the dropout each time it's screwed and unscrewed. A cam merely presses against the dropout.

Lastly, need I even mention the issue of the threads in the opp
A) No. It isn't.

2) It is horseshit to claim the axle diameter is why it is stiffer (in all but extreme 15mm+ TA diameter and XC/MTB riding). BUT...your POV is horseshit that QR is just as stiff...because clearly you don't understand why thru-axle is the way it is.


In the last 1-2 hours you went from not knowing why TA was stiffer than QR...to suddenly being an expert. I'm sure I speak for the entire internet, in that we all bow to your superior wisdom and knowledge gained in the last hour.



And, quoted for posterity.
 

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Model T was actually a pretty good car, and most folks could figure our how to use it eventually. No need to change the whole way we shift the gears on an automobile like 3 pedal 1916 Cadillac wanted us to do

And really flip flop rear wheels enabled racers to complete many Tours de France just fine. Ridiculous idea to give them more gears with a derailleur to shift them.

Heck toe clips and straps were highly favoured by many pros after the clipless Looks appeared .. Heck Roche stuck with clips and did the triple crown. No one since has matched that feat ... must be because they are all on this clipless pedal nonsense.

;)

I half agree with the OP. It is a very subtle advantage having thru axles on a road bike. It is a major difference on a mountain bike. I am more than happy with QR on my road bikes. for now. and yes one of my road bikes has disc brakes (well it is a gravel bike)
 

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One advantage to through axle setups is that the wheel will always be correctly aligned - which will help prevent the rotor from rubbing against the brake caliper or pads.
 

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One advantage to through axle setups is that the wheel will always be correctly aligned - which will help prevent the rotor from rubbing against the brake caliper or pads.
Disc/wheel alignment isn't an issue with good QRs. The issue is that most bikes don't have good QRs (the closed cam Shimano or DT Swiss style, not the exposed plastic/aluminum setups). I ran my disc MTB with f/r regular QRs for years without issue, at least once I put XT skewers on it.

My road bike has regular QRs, but one of my MTBs has Boost thru-axles front and rear, and the other a 15x100 up front ('upgraded' from a regular QR). There's no tangible advantage to any of it. Sure, like BB30, it's technically stiffer. The issue is that 9/10mm QRs are plenty stiff already, especially for a road bike. I file this in "new and improved, but really to sell more things".
 

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Since you're not backing up your stuff with scientific facts I will answer with a non scientific reply,just a very practical one. I love my TAs, my bike is a lot stiffer and an 83kg guy like me can totally feel the difference. And yes I run discs too.
 

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Perhaps my two neurons have disconnected but I'm pretty sure a quick releases has a cam AND screw holding it tight.

Excellent rant though.
Both thru axles and standard QRs have cams and threads. In addition to just being thicker, a thru axle replaces the nut on the end of a regular skewer with threads in a frame fork. They're functionally pretty much identical; one is just bigger and beefier than the other. The only real difference that I've noticed is that thru axles (at least the half-dozen that I've owned) have a tension adjustment as well, be it an allen screw on the lever side or something built in to the threaded side of the fork.

I guess one safety advantage of a thru axle is that it can't really drop out of a dropout like a loose QR can. If I recall correctly, this was the main reason why DH MTBers started using these things years ago. It's also supposed to stiffen up suspension systems (which makes sense), though I've never been able to tell a difference. Again, I'm sure it's measurably stiffer in a lab and probably more durable under extreme DH MTB race conditions. On a fully rigid, stiff-as-hell road bike that rides on mostly smooth surfaces though? Meh.
 

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Through axle is an idiotic design - one of several that have become popular in bicycles over the last two decades.

People talk about the stiffness of the through-axle system because it's thicker. That's horseshit. Such arguments show a complete lack of understanding of the forces involved.
Sigh.
No need to read beyond here. Cause you clearly CLEARLY have no comprehension of the forces involved or reasons for the stiffness.

I have no dog in the fight. I'm an engineer. I have MTB & Cross bikes with Disc and QR's. They're fine for me and the majority of the population.... BUT there's no question that Through Axle is a superior design.
The only issue with Through Axle is standardization... but that's a different topic.
 

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Sunday morning after Derby, saw two bikes chained to poles with the front wheels stolen.
QR invites theft. Axles needing tools are too complicated for thieves. I threw the QR hardware away from my bikes, and carry wrenches, tubes, a pump. Thieves can't be bothered to break into my tool kit to remove stuff.
I use a 10-32 x 5" SS cap screw through the axle with washers & elastic stop nut. Replaced the weird thread QR nut that fell off & required me to gingerly pedal home with a loose front axle, dodging holes and stopping for railroad tracks.
On the *****y supply front, ordered some weird thread axle nuts from an internet supplier a week ago and still don't have a shipper tracking e-mail. They were allegedly in stock. Pay pal was debited right away. Mcmaster.com the industrial screw supplier doesn't debit until the box ships.
 
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