Author Topic: Front wheel falling out of forks?  (Read 3522 times)

Andyb1

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Front wheel falling out of forks?
« on: October 02, 2023, 06:53:22 pm »
Hi,
I have not had the front wheel fall off (yet) but the fork drop outs on my Sherpa are flat steel and would not retain the ends of the Q/R skewer if it came loose (and it is probably the same at the rear dropouts).
On other forks there is often a raised ridge around the skewer ends so that the skewer has to be undone a few turns in order to remove the wheel rather than just being loosened.
I am probably just being paranoid, but is this a potential problem or not?


JohnR

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Re: Front wheel falling out of forks?
« Reply #1 on: October 02, 2023, 08:15:55 pm »
See "lawyer lips" at https://www.sheldonbrown.com/gloss_l.html .

"The introduction of disc brakes has caused increased vulnerability of the front axle and skewer, due to the disc brake applying an ejection force that tends to pull the axle out of the fork." If you've got rim brakes then the risk of a slightly loose wheel self-ejecting is much lower. If it's loose enough to be able to fall out then you should notice.

Andyb1

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Re: Front wheel falling out of forks?
« Reply #2 on: October 02, 2023, 10:11:12 pm »
Thanks John, those Sheldon Brown articles made interesting reading.
My Sherpa has rim brakes and enclosed type over-centre locks - so should be OK - but something to keep an eye on.

Andyb1

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Re: Front wheel falling out of forks?
« Reply #3 on: October 04, 2023, 08:57:51 am »
What was at the back of my mind was that I did have a rear wheel loosen last year.    The bike had security skewer ends which are done up with an allan key, and about 15 miles earlier I had swopped innertubes at the roadside after a puncture.   Probably I did not tighten the skewer enough when I replaced the wheel, but I got rid of the security skewer ends and fitted conventional over centre skewer ends which I am more used to.

Has anyone else had any problems with the allan key type skewer ends, or was it just me not tightening it enough?

PH

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Re: Front wheel falling out of forks?
« Reply #4 on: October 04, 2023, 12:06:13 pm »
Has anyone else had any problems with the allan key type skewer ends, or was it just me not tightening it enough?
Disc brakes or rim?  Sorry, but I think that was almost certainly user error, very slightly less certain with discs.  I've never heard of any wheel popping out of the rear dropout, it just isn't subjected to the same forces.
I use the security version of hex key skewers on all QR wheels, including two front discs.  Depending on the design of the cam, they can be better than QR levers, they're at least as secure as the best. Even so, I check mine whenever I'm also checking tyre pressures, so that's at least once a week on my most used bike. just back it off a turn, check the wheel is correctly seated and re-tighten.  I'm in no hurry so haven't put a stopwatch to it, but I'd be surprised if checking pressures, skewers and brake blocks takes more than five minutes.   
The examples of wheels coming out of the dropout are rare, but the idea has rightly gained a lot of publicity due to the potential consequences.  We have the development of thru axles thanks to that publicity and IMO they're a better design all round. Enough of an improvement that I wouldn't buy another QR fork, but not so much that I'd consider swapping the current ones.


Andyb1

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Re: Front wheel falling out of forks?
« Reply #5 on: October 04, 2023, 01:37:31 pm »
Hi PH,
The problem I had was on a disc braked rear wheel - when I lifted the bike the wheel fell out!   It had been holding OK in the dropout when riding before that.  I agree that it was probably my fault and that I had under-tightened it.   But at least with an over-centre lever you can easily see if it has loosened.

What sort of torque do you tighten yours to?   I think the figure I had was 9NM which is really quite low but with a short allan key is attainable.

mickeg

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Re: Front wheel falling out of forks?
« Reply #6 on: October 04, 2023, 01:38:20 pm »
When touring, I use skewers that use a 5mm allen wrench, not one that use a special key.  And for riding near home (not touring) I use that type of skewer on my dynohub wheels but quick release on my other wheels.  And to avert problems later, I carry a spare 5mm allen wrench with my spare inner tubes.

I do this solely because I suspect that most thieves are opportunists, do not carry around an allen wrench or multitool in their pocket.  Thus, I do not want them to steal a wheel. 

Never had a problem with a wheel coming out.

All my other wheels use a conventional quick release.

That said, my only disc brake is on the rear on my titanium bike, the front brake on that bike is a rim brake.  The disc brake unit is on the chainstay, not seat stay, thus any forces on the axle from braking would only push the axle further into the dropouts, not out.

I had problems half a century ago with rear wheels slipping in the horizontal dropouts on the drive side if I was pedaling hard on a bike with nutted axles, that was from not tightening it enough and the chain tension could pull the wheel forward on the drive side.  If you are many miles from home and your axle slips in the dropout far enough that the tire rubs on the chainstay and you do not have a wrench with you, you remember that problem for a long time.  So, yes, I remember that happening a few times.

mickeg

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Re: Front wheel falling out of forks?
« Reply #7 on: October 04, 2023, 01:43:52 pm »
Hi PH,
The problem I had was on a disc braked rear wheel - when I lifted the bike the wheel fell out!   It had been holding OK in the dropout when riding before that.  I agree that it was probably my fault and that I had under-tightened it.   But at least with an over-centre lever you can easily see if it has loosened.

What sort of torque do you tighten yours to?   I think the figure I had was 9NM which is really quite low but with a short allan key is attainable.

I am not Ph, but I will comment on torque. 

I have no clue what torque I use, but I think that the skewer nuts on my allen wrench type skewers are aluminum, not steel.  Thus, I am fearful of stripping the threads, which would be very bad if I do not have a spare skewer with me.  So, I do not use a lot of force.  I am quite sure it is less than 9 nm.

I think I heard at one time that a problem with allen wrench type skewers and Rohloff hubs is that if you overtighten the skewer, you can have problems, but I am not sure about that.  I just don't over-tighten them because of fear of stripping the threads.
 

PH

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Re: Front wheel falling out of forks?
« Reply #8 on: October 04, 2023, 03:44:02 pm »
Hi PH,
What sort of torque do you tighten yours to?   I think the figure I had was 9NM which is really quite low but with a short allan key is attainable.
Interesting question, I don't know, I've never considered it, pretty tight!
The security version comes with a small tool, about 60mm leverage, there's a limit to how tight that can get them, 9Nm would usually require something longer, so I'm  guessing it's probably more like 6-7.

Andyb1

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Re: Front wheel falling out of forks?
« Reply #9 on: October 10, 2023, 06:30:26 pm »
I found the Rohloff instructions which say no more than 7nm torque on the skewer.
If my allen key is 100mm and I am 75kg then all of my weight on the allen key is only 7.5Nm - so as PH has said, with a 100mm allen key the max torque is will be low, more like 3 or 4nm with about half my weight on the allen key!

mickeg

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Re: Front wheel falling out of forks?
« Reply #10 on: October 15, 2023, 08:08:05 pm »
I found the Rohloff instructions which say no more than 7nm torque on the skewer.
If my allen key is 100mm and I am 75kg then all of my weight on the allen key is only 7.5Nm - so as PH has said, with a 100mm allen key the max torque is will be low, more like 3 or 4nm with about half my weight on the allen key!

I have not done those calculations since I was in college, and I am retired now so I have no interest in learning them again.

But I think you are way off.

I bought one of these to make sure I do not over-torque my Ritchey Break Away couplers.
https://www.amazon.com/IceToolz-Multitool-Ergonomic-Automotive-Maintenance/dp/B015DJGECA

I can easily with one hand put 7 nm of torque on something with it.


Andyb1

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Re: Front wheel falling out of forks?
« Reply #11 on: October 15, 2023, 08:50:16 pm »
Mick, you are right.
1N is 1kg x g (where g = 9.81)
So 7NM is 0.7kg at 1m leverage, or 7kg at 10cm leverage.
Which sounds a lot more sensible.
I was a factor of 10 out.

JohnR

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Re: Front wheel falling out of forks?
« Reply #12 on: October 15, 2023, 10:25:15 pm »
Mick, you are right.
1N is 1kg x g (where g = 9.81)
So 7NM is 0.7kg at 1m leverage, or 7kg at 10cm leverage.
Which sounds a lot more sensible.
I was a factor of 10 out.
If you remember that one newton ~ one small apple then it becomes easy to visualise newton-metres.

mickeg

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Re: Front wheel falling out of forks?
« Reply #13 on: October 15, 2023, 11:47:07 pm »
Mick, you are right.
1N is 1kg x g (where g = 9.81)
So 7NM is 0.7kg at 1m leverage, or 7kg at 10cm leverage.
Which sounds a lot more sensible.
I was a factor of 10 out.

Since you were basing that on your weight, you just became the most successful person in history at dieting.

mickeg

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Re: Front wheel falling out of forks?
« Reply #14 on: October 15, 2023, 11:48:48 pm »
Mick, you are right.
1N is 1kg x g (where g = 9.81)
So 7NM is 0.7kg at 1m leverage, or 7kg at 10cm leverage.
Which sounds a lot more sensible.
I was a factor of 10 out.
If you remember that one newton ~ one small apple then it becomes easy to visualise newton-metres.

I wish you were around to instruct me when I was a student in engineering classes.