GeoKrpan

A couple of weeks ago I crashed after hitting a pine cone. The front wheel pulled out of the fork on the drive side.
I would not have crashed otherwise. This was the first time in 30 years of riding that this happened, a freak accident.

The front wheel is thru axle with an adapter for use in a standard 9mm dropout with standard quick release. I was using a Shimano XT MTB skewer tightened tight, tight.

I just bought this adapter that uses bolts intead of a QR. I am certain that the wheel would not have come out with this adapter.

ckindt

ok, well I hope it works for you. Sorry to hear about your accident.

GeoKrpan

Thanks, I've been hurtin' these last two weeks.

ckindt

After re-reading your post, I still don't understand what caused the accident; the pine cone or the axle loosening.

wheelsmcgee

I think he's saying the (already loosened) QR caused the wheel to pop off from the act of hitting a simple pinecone.

Sorry to hear that Geokrpan, I hope you recover soon. That bolt on axle looks pretty solid, but I'd consider putting a lock washer on those hex bolts. I've had fork mounted bottle cage bolts loosen up on long gravel rides.

Spoonrobot 

FWIW, proper quick-release is going to have more clamping force than either 15mm bolts or 6mm hex head screws.

So far the limited info on your accident is a real head scratcher. Tight, tight quick-release fails after pine cone collision?

I'm wondering if this was an issue with the wrong size adapter since you are using a T/A hub with 9mm QR front adapter and are now going to a screw on 9mm adapter?

Why not just use the proper Thru-axle and fork? This would appear to be the safest option?

chaadster

I wouldn't tell people that.

Hiro11

I've never heard of or seen a properly tightened QR spontaneously opening.

dabac

I'd be fairly inclined to trust a Shimano XT QR.
But I wouldn't trust a noname, external cam QR on a disc brake front.

wschruba

Spontaneously opening, no, but stripping out the nut, yes. Of course, to do so, it would already have to be on the brink of too tight (so, not properly tightened), and then receive a levering force of some sort that stressed the dropouts sideways. Based on the OP's post, this is a plausible explanation to me.

Just a couple of other thoughts to add: clamping force should be largely independent of the method of attachment, thread size being equal. So, if a 5mm bolt with a washer the same diameter/design of the QR's clamping face is used, they will have the same clamping force, in ideal conditions (after all, a QR's threads are 5mm...). Of course, that assumes that the QR's cam design can achieve optimal tension in real-world conditions, the clamping surfaces are steel, etc, etc.

Axle nuts are in another realm altogether--simply, the nut has far larger thread diameter, so can take more tension; for any given diameter of washer (from the QR/bolt problem), it will be able to develop more clamping force. That said, axle nuts are over-kill except in specific cases (IGHs, BMX, track nuts).

Through-axles make clamping force mostly irrelevant, since it isn't relied on to hold the wheel in the dropout, just to keep the wheel in place, and from knocking side-to-side.

One thing that bolts/axle nuts do that QRs (and most bicycle through-axle designs!) cannot: in a case of fastener failure, both sides need to fail for the wheel to be able to detach itself from the frame

GeoKrpan

The pine cone was of the variety that's as hard as a rock and nearly as heavy.

GeoKrpan

A quick release clamps very well on one side and not as well on the other.

GeoKrpan

True, axle nuts are in another realm.

dabac

Generally, no.

How do you think that is achieved?

The skewer is free to move through the axle.
So the pull you create when you close the lever is immediately transmitted to the other end, pulling just as hard there.
Unless you have the skewer anchored in the middle, the forces exerted at both ends will be balanced and equal, there's no way around that.

There are things that would make the ends clamp differently:
- one axle end protruding longer, making the lever or nut bottom out against the axle or the conical spring before tightening against the dropout face
- the nut and the lever clamping face might not have the same machining/ material, making one end bite better.
- the locknut clamping faces might not be equally grippy.
- the dropouts might not be in the same condition. If one is more worn, it might not offer the same grip.

chas58

There was that TREK recall in 2015, because apparently a lot of people don't really know how to use a QR. Seriously, that kind of stuff does a lot to push the sales of through axles with disks because companies don't want that liability.

dabac

Wasn't that about levers overextending, swinging so far in they could snag the rotor/spokes?

Maybe they should start putting some safety-oriented effort into the original engineering then.
Whether TA or QR, the engineering is pitiful. Embarrassing even.

Despite being safety critical, the industry has gone for a design that at best might have been mistaken for "good enough". Then, as events proved them wrong they went for another round of "good enough".
It wouldn't surprise me in the least if we eventually get to see a 3rd round of "good enough" before someone is finally asked to do some proper analysis and engineering.

Spoonrobot 

The issue with the trek recall was people using the quick-release skewer handle, in the open position, as a lever to tighten the wheel into place like a screw instead of clamping it down. Then when it inevitably loosened up while riding it would flop into the rotor causing catastrophic front wheel stoppage.

https://s7d4.scene7.com/is/content/Tr...otice_USEN.pdf

I do not disagree with the safety oriented design comments.

OP has a thread over at MTBR as well. It has more info but is not any more illuminating. This really seems like an issue related to using an adapter of dubious manufacture to use a thru-axle wheel in a QR fork.