Beware of your QR



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Nelson Binch

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"Carla A-G" <[email protected]> wrote in message news:[email protected]...
| http://www.ne.jp/asahi/julesandjames/home/disk_and_quick_release/
|
| - CA-G
|
| Canadian Girls Kick Ass!

I wonder how widespread this article has become and if it will impact a lawsuit in the future.

Kind of makes me glad I use rim brakes (even on my tandem!)

---
__o _`\(,_ Cycling is life, (_)/ (_) all the rest, just details. Nelson Binch =^o.o^=
http://intergalax.com

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Mark Hickey

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"Nelson Binch" <[email protected]> wrote:

>"Carla A-G" <[email protected]> wrote in message news:[email protected]...
>| http://www.ne.jp/asahi/julesandjames/home/disk_and_quick_release/
>
>I wonder how widespread this article has become and if it will impact a lawsuit in the future.
>
>Kind of makes me glad I use rim brakes (even on my tandem!)

I thought a lot of it was pretty good too, but do have a question (or three).

The article claims that the skewer can deform enough to clear the "lawyer lips" on the fork. That
seems pretty unlikely to me, at least with a properly-tightened QR. Slip, sure... I can believe
that can happen. But the forces that would be required to stretch a steel QR shaft enough to get
either end of the skewer over the lawyer lips would also break - or at least permanently stretch -
the QR skewer shaft. Or more likely, strip the threads on the nutted end if the nut is aluminum
(and most are).

Besides, the top end of most lawyer lips are "squarish" which makes the whole prospect of forcing
the wheel down over them even more difficult. Plus, I suspect you're going to have to actually force
the QR down over both sets of lawyer lips simultaneously to get the wheel to fully disengage (read,
fall off).

If this were really likely, for every "total wheel disengagement", you'd see dozens of "near
disengagements" which would result in one end of the QR skewer ending up perched on top the lip -
and as far as I know, that simply doesn't happen.

Make sense?

Mark Hickey Habanero Cycles http://www.habcycles.com Home of the $695 ti frame
 
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Michael Dart

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N

Nelson Binch

Guest
"Mark Hickey" <[email protected]> wrote in message
news:[email protected]...
| "Nelson Binch" <[email protected]> wrote:
|
| >"Carla A-G" <[email protected]> wrote in message news:[email protected]...
| >| http://www.ne.jp/asahi/julesandjames/home/disk_and_quick_release/
| >
| >I wonder how widespread this article has become and if it will impact a lawsuit in the future.
| >
| >Kind of makes me glad I use rim brakes (even on my tandem!)
|
| I thought a lot of it was pretty good too, but do have a question (or three).
|
| The article claims that the skewer can deform enough to clear the "lawyer lips" on the fork. That
| seems pretty unlikely to me, at least with a properly-tightened QR. Slip, sure... I can believe
| that can happen. But the forces that would be required to stretch a steel QR shaft enough to get
| either end of the skewer over the lawyer lips would also break - or at least permanently stretch -
| the QR skewer shaft. Or more likely, strip the threads on the nutted end if the nut is aluminum
| (and most are).
|
| Besides, the top end of most lawyer lips are "squarish" which makes the whole prospect of forcing
| the wheel down over them even more difficult. Plus, I suspect you're going to have to actually
| force the QR down over both sets of lawyer lips simultaneously to get the wheel to fully disengage
| (read, fall off).
|
| If this were really likely, for every "total wheel disengagement", you'd see dozens of "near
| disengagements" which would result in one end of the QR skewer ending up perched on top the lip -
| and as far as I know, that simply doesn't happen.
|
| Make sense?

Very much so. I think if this were a real widespread problem, we would have heard about it a lot
more by now. Somebody with a modicum of engineering ability can make very believable arguments for
both sides of an issue like this (much like another issue!) so I come back to the first thing that
pops into my mind; if this was a real problem, somebody would be sued by now, period.

From a layman's perspective (I studied engineering in the 80s, but went into retail afterwards) I
don't see why there is a real different *at the hub* between rim and disk brakes since both are
applying torque in the opposite direction at about the same area of the hub (the bolt hole circle of
a disk compared to the spoke hole circle) with the main different that the disk applies more to one
side than the rim brake (if you really think about it, a rim brake is still a disk brake!)

Looking at the pictures in the article, it looks a lot more to me like *the skewer was not applied
properly* IMHO of course.

---
__o _`\(,_ Cycling is life, (_)/ (_) all the rest, just details. Nelson Binch =^o.o^=
http://intergalax.com

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S

Slacker

Guest
> From a layman's perspective (I studied engineering in the 80s, but went into retail afterwards) I
> don't see why there is a real different *at the hub* between rim and disk brakes since both are
> applying torque in the opposite direction at about the same area of the hub (the bolt hole circle
> of a disk compared to the spoke hole circle) with the main different that the disk applies more to
> one side than the rim brake (if you really think about it, a rim brake is still a disk brake!)

> Nelson Binch =^o.o^=

And now we know why you went into retail.

--
Slacker
 
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Michael Paul

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"Nelson Binch" <[email protected]> wrote in message
news:[email protected]...
> "Mark Hickey" <[email protected]> wrote in message
> news:[email protected]...
> | "Nelson Binch" <[email protected]> wrote:
> |
><snip>

>Very much so. I think if this were a real widespread problem, we would
have
> heard about it a lot more by now.

I agree 100%. it probably happens, but not often enough to be an issue adn when it does happen who's
to say that it wasn't due to an improperly installed QR or worn down bushings preventing the QR from
clamping properly.

> From a layman's perspective (I studied engineering in the 80s, but went
into
> retail afterwards) I don't see why there is a real different *at the hub* between rim and disk
> brakes since both are applying torque in the opposite direction at about the same area of the hub

the disc is vertically mounted resulting in a downward force on the QR when stopping. with rim
brakes, the pads are horizontal resulting in a more horizontal force on the QR.

What the article is pointing out is that with discs, the QR will pivot about the caliper and since
the momentum is coutterclockwise, the tendancy is for the QR to want to rotate in an arc with the
disc caliper as the center. With the rim brakes, the pads become the center of the circle that the
QR will swing around but the natural arc swings right into the rear of the dropouts so not only is
the QR clamping force keeping the wheel in place, but the rear of the dropouts is absorbing some of
that force as well.

(the bolt hole circle of a disk
> compared to the spoke hole circle) with the main different that the disk applies more to one side
> than the rim brake (if you really think about it,
a
> rim brake is still a disk brake!)

Yes, but the centers are in different locations and that is the difference.

Michael
 
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