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QR hub: diameter of hollow hub axle

Old 07-04-22, 07:51 AM
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QR hub: diameter of hollow hub axle

The skewer of a QR has a diameter of 5mm.
What is the diameter of the hollow hub axle (skewer is inserted into this)? Is this diameter a standard?
Thanks
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Old 07-04-22, 08:28 AM
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The ID of a qr hub is nominally 5mm and allows passage of the skewer. Pretty much all qr hubs are the same.
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Old 07-04-22, 08:30 AM
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I don't think there is a "standard". However since the outer diameter of the axle is somewhat controlled by the slot in the fork ends or drop outs and the skewer has to have room to be installed and removed, that over the many many years skewers have been with us that most holes through axles requiring a skewer will be pretty close to the same. I doubt any manufacturer wanted to risk making a product that wouldn't work with others for this particular application and time period. Might see some differences because of the grade of steel or other material that is used for the axle. But not so much that one skewer won't work with another.
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Old 07-04-22, 08:31 AM
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the shaft of many (most) titanium skewer quick releases measure close to 4mm
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Old 07-04-22, 08:34 AM
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My steel skewers are all 4.5mm in diameter, and the nuts that go on the threaded end are all interchangeable. The bore (inner axle diameter) is 5mm. The conical springs keep the skewer centered.
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Old 07-04-22, 08:35 AM
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Originally Posted by t2p View Post
the shaft of many (most) titanium skewer quick releases measure close to 4mm
Even if they are 4.5mm like steel, they will be significantly weaker at that diameter. That is why I would never use them in applications where failure could kill me.
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Old 07-04-22, 09:49 AM
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Originally Posted by anga View Post
The skewer of a QR has a diameter of 5mm.
What is the diameter of the hollow hub axle (skewer is inserted into this)? Is this diameter a standard?
Thanks
From https://www.bikeradar.com/advice/buy...xle-standards/
A quick release wheel has a hollow axle, 9mm in diameter at the front and 10mm at the rear, with a 5mm diameter skewer that passes through it.
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Old 07-04-22, 10:29 AM
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Originally Posted by Polaris OBark View Post
Even if they are 4.5mm like steel, they will be significantly weaker at that diameter.
I've been riding with titanium skewers for 20+ years. I realize that that doesn't mean they couldn't break next time I ride, but titanium has very nearly the same tensile strength as stainless steel:
"Stensile (sic) strength measures the maximum stress that a structure can sustain. Stainless steel’s tensile strength is 485 MPa versus titanium’s 480 MPa. For some additional perspective, aluminum has an MPa of only 90 and copper’s MPa is only 200."
SOURCE
That's about a 1% decrease in tensile strength.

EDIT: I found a value closer to the one you quoted HERE in Table 1. I can't explain the discrepancy, but I *can* verify that my titanium skewers have held up for over 20 years. I'm not a metallurgist!

Last edited by sweeks; 07-04-22 at 08:48 PM.
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Old 07-05-22, 06:46 AM
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Originally Posted by Polaris OBark View Post
My steel skewers are all 4.5mm in diameter, and the nuts that go on the threaded end are all interchangeable. The bore (inner axle diameter) is 5mm. The conical springs keep the skewer centered.
The shaft is typically about 4.5mm diameter, but the threaded section is created by rolling the threads rather than cutting them, so the diameter of the threaded section ends up 5mm diameter.
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Old 07-05-22, 01:24 PM
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It seems like you’re asking for the diameter of the axle, which should be 10mm for a normal QR rear wheel, or 9mm for a front.
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Old 07-05-22, 03:36 PM
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If the question is what is the axle's through hole, that positions the QR skewer, than I would speculate it's slightly bigger than 5mm to allow for a bit of clearance. I also suspect that different axle manufacturers will have their axle "holes" a tad different but all close to the same dimension. Of course one could measure and then we would not have to wonder which aspect was in question, or what the dimension actually is. Andy
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Old 07-05-22, 03:37 PM
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Originally Posted by bboy314 View Post
It seems like you’re asking for the diameter of the axle, which should be 10mm for a normal QR rear wheel, or 9mm for a front.
There have been 9.5mm (3/8") axles with a QR capacity. I suggest measuring what's actually in play. Andy
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Old 07-05-22, 03:45 PM
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Originally Posted by sweeks View Post
EDIT: I found a value closer to the one you quoted HERE in Table 1. I can't explain the discrepancy, but I *can* verify that my titanium skewers have held up for over 20 years. I'm not a metallurgist!
I deleted my reply because I thought it must be wrong.

Anyway, thanks for that link.

I think the difference must be stainless steel vs. more "normal" alloys of steel. I also discovered one pair of my skewers is indeed Ti.
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Old 07-05-22, 04:12 PM
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There may have been rare exceptions to the use of standard-diameter skewers (and thus hub axle I.D.s). I have a vague memory of Weyless hubs using proprietary dimensions for their hubs. Maybe larger-diameter aluminum skewers. Could easily be wrong, though.
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Old 07-06-22, 05:53 AM
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Originally Posted by Andrew R Stewart View Post
If the question is what is the axle's through hole, that positions the QR skewer, than I would speculate it's slightly bigger than 5mm to allow for a bit of clearance. I also suspect that different axle manufacturers will have their axle "holes" a tad different but all close to the same dimension. Of course one could measure and then we would not have to wonder which aspect was in question, or what the dimension actually is. Andy
I am indeed asking for the inner diameter of the axle's through hole.
Is it possible that 9mm and 10mm are the outer diameters of the hollow tube that is the axle's through hole?
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Old 07-06-22, 06:37 AM
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Originally Posted by anga View Post
I am indeed asking for the inner diameter of the axle's through hole.
Is it possible that 9mm and 10mm are the outer diameters of the hollow tube that is the axle's through hole?
Yes, that is correct.
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Old 07-06-22, 11:33 AM
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Originally Posted by Polaris OBark View Post
Even if they are 4.5mm like steel, they will be significantly weaker at that diameter. That is why I would never use them in applications where failure could kill me.
A Ti fastener will always be weaker than the same fastener in steel, but significantly lighter.
You can have Strong, Light,or Cheap: Pick Two. Lightness generally comes at the expense of Strength.
Nobody is making you put Ti skewers on your LHT.

(Also, if your QR skewer is a weight- bearing element; you're doing something wrong)
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Old 07-06-22, 11:39 AM
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Originally Posted by Ironfish653 View Post
A Ti fastener will always be weaker than the same fastener in steel, but significantly lighter.
You can have Strong, Light,or Cheap: Pick Two. Lightness generally comes at the expense of Strength.
Nobody is making you put Ti skewers on your LHT.

(Also, if your QR skewer is a weight- bearing element; you're doing something wrong)
I would prefer strong >> (light or cheap). I'm using Dura Ace and DT Swiss for that reason.

The usual mode of failure is for the threads to strip out the nut, or to strip off. (I suppose they can also break the spindle from over-stretching while over-tightening, but titanium is actually more able to withstand that than is steel.)

This is probably most important for folks who have disc brakes and quick-release (rather than thru-axle). Because of the downward force during braking, the wheel has a tendency to move within the dropouts of the fork, or will even have a tendency to be ejected from the fork if the dropouts aren't forward-facing. This encourages the user to crank down on them as much as possible. Before I got internal cam Dura Ace and DT Swiss skewers, my front wheel would need to be re-seated after hard braking or I would get a bit of pad rub on the disc. If you are going to crank it down hard, you will want strength.

Thru axles weigh a lot more than quick release skewers and their end-caps, and I have never heard anyone complain about their weight.

Last edited by Polaris OBark; 07-06-22 at 11:45 AM.
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Old 07-06-22, 11:45 AM
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Originally Posted by Trakhak View Post
There may have been rare exceptions to the use of standard-diameter skewers (and thus hub axle I.D.s). I have a vague memory of Weyless hubs using proprietary dimensions for their hubs. Maybe larger-diameter aluminum skewers. Could easily be wrong, though.
Ritchey had a DH MTB hub in the late 90s/early '00s that used a 9mm "skraxle" (9-F/10-R) kinda like a thru-axle, but for QR dropouts.
One of those transition technologies from the end of the 26'er era.
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Old 07-06-22, 12:28 PM
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The outer diameter of the axles on my wheels are either 15mm (6802 or 6902 bearings) or 17 mm (6803 or 6903 bearings).

My old crap with loose balls is 10 mm IIRC
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Old 07-06-22, 12:50 PM
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Originally Posted by Polaris OBark View Post
The usual mode of failure is for the threads to strip out the nut, or to strip off. (I suppose they can also break the spindle from over-stretching while over-tightening, but titanium is actually more able to withstand that than is steel.)
.
I can see, in a QR skewer application, that the 'stretch' inherent in a Ti fastener might be considered beneficial, but it's been my experience that Ti fasteners tend to deform (twist or elongate) at a much lower threshold than the same fastener in steel. One of our manipulator systems uses a lot of Ti M5 fasteners, and we've had enough bolts broken during routine maintenance, that fleetwide standing instruction is that no component installation is to be done on them without a properly set torque wrench (no hand-tightening)

Ti is too finicky, IMHO, for field repairs on something as basic as a bicycle.
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Old 07-06-22, 01:40 PM
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I didn't realize the external cam QR skewers I replaced with internal cam steel skewers (and later, DT Swiss steel skewers) were titanium until a couple of days ago. I had just assumed that the problem was that they were external cams, but it might be the titanium was stretching under load a wee bit.
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Old 07-06-22, 02:59 PM
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Originally Posted by Polaris OBark View Post
I didn't realize the external cam QR skewers I replaced with internal cam steel skewers (and later, DT Swiss steel skewers) were titanium until a couple of days ago. I had just assumed that the problem was that they were external cams, but it might be the titanium was stretching under load a wee bit.
Yes, titanium stretches twice as much as steel for the same force applied. This means the the QR needs to pull the skewer measurably farther. So, either the lever assembly needs to be bigger to keep the hand force needed the same or the tension in the skewer is lower. I like nice clean levers. I also like nice tight skewers that keep rear wheel locked solid in horizontal dropouts and front wheels from ever coming out. (I won't use a disc brake mounted behind the hub because introducing a large lifting force to the fork when braking just seems to me like a really bad idea.)

So, for me - no discs and simple, reliable, all steel (aluminum levers and heads are OK) internal cam QRs of modern design (the new cam shape, not the old Campy NR shape with it's far less secure locking). Good thing is such levers are easy to find. Lesser modern all steel Campy QRs are sweet. So is my Ultegra of the 9-speed era. I have a really cheap modern Shimano that looks its price range with really good action; as good as anything I've used.
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Old 07-15-22, 09:11 AM
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Thread has acquired a life of its own, discussing titanium vs steel skewers
Nothing to do with original topic!
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Old 07-15-22, 09:19 AM
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As the OP topic has been answered by a few here I would not be bothered by continuing blabbing. Andy (who questions the claim of older Campy NR skewers being of poor clamping force)
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