How widespread is (poor) knowledge of wheel Q/Rs

[Brucey]

.......... During a hard stop with a disc brake the front wheel sees about 500kgf pulling the wheel downwards out of the dropouts.

Carrying a spanner is no great hardship I agree but wheel changes are not fast enough for racing.

Wing nuts don't really offer enough purchase to get the wheels properly tight; rear wheels in horizontal dropouts tend to pull over too easily IME. Several patterns of wingnut will actually bend or break before they are ever tight enough to stop the wheel from pulling over.

1. During hard braking, the front wheel is pushed hard INTO the dropouts.

not with a disc brake using conventional caliper mountings. If you analyse the forces involved you will soon see that. As I mentioned previously I certainly don't recommend that you try it out.

3. Never had a problem with the wheel pulling over, or ever had one break. Sold that bike with all four wingnuts on, and intact too.

not everyone pushes as hard on the pedals as everyone else. 'Tight enough for some folk' is not the same thing as 'stopping the wheel from pulling over'. If you can explain to me how you might, by hand, be able to get ~30ftlbs onto a wing nut that is ~2-1/2" long I shall be interested to hear it.

Misunderstandings are alive and well!

cheers

[reohn2]

Front dropouts facing forward eliminate wheel ejection due to disc brake forces,all my bikes,two Genesis and one Salsa have such dropouts.
Our Cannondale tandem had conventional dropouts but they were socketed and we never had problems.

Vertical rear droputs eliminate wheels pulling over.

[PH]

1. During hard braking, the front wheel is pushed hard INTO the dropouts.

Through axles are the latest thing in response to this issue. Before that there's been some other ideas, such as forks with forward facing dropouts (Edit - reohn2 beat me to that one) or brake fitting on the front of the forks.
It isn't a question of only doing the QR up properly, but of also frequently checking it, the force can be enough to cause it to unscrew. Plenty of real life examples if you google for them, it's more than just theory, though if you do want the theory, google - Annan theory disc brake

[peetee]

Another often misunderstood bike feature is the QR on caliper brakes, I've come across lots of people who have adjusted the brakes in the open position, if I know them I'll ask why.

I asked this of one rider and he said it can save an almighty tangle at the cafe stop. The geometry of some bikes is such that, when parked, the steering can turn and the front wheel run out tipping the bike over. Closing down the brake QR stops this.

[Brucey]

shows roughly (*) how forward-facing dropouts help stop wheel ejection under braking. In order to be effective the dropout slots need to be in line with the disc pads or (in the view above) rotated further CW than that. Since many disc calipers end up being further down/backwards than as drawn, disc brake forks with better dropout designs tend to have the slots facing forwards, horizontally more or less.

(*) Strictly speaking the reaction load on the axle arising from the brake is parallel to the tangent of the disc where the pads are biting. In this situation there is no such thing as a curved force vector, hence the red arrows in the diagram above are inaccurate and misleading.

With disc brakes, downwards facing dropouts with no LL are a liability.

cheers

[Mick F]

With disc brakes, downwards facing dropouts with no LL are a liability.

Thanks for your alarming diagram.
No mention of weight pushing downwards under heavy braking though.

Also, QR's in general, are a liability ............... hence this thread.

............... and I agree with R2.
No need for QRs at all out of racing circles. LLs aren't an issue with track nuts either.

[recumbentpanda]

Well, I thought I knew enough about qrs until I discovered my back wheel had been shifting under load sufficiently to mash the drive side downward facing drop out! This was even with the qr done up as tight as I could get it.

Trying to resolve this, I discovered the difference in efficiency between old school internal cam qrs (good), and modern external cam type (not so good).

I threw on some old Shimano internal cam skewers. These solved the problem, but not, as it turned out, because of improved efficiency. Turned out my axle ends were fractionally too long for the thickness of the drop outs and were sticking out a millimetre or so either side. The old style qrs had a deep recess in the knurled washer that presses against the drop out face. This more than accommodated the extra axle length. The ones I replaced had a much shallower recess, and had actually been bearing on the axle end and not really gripping the drop out faces properly no matter how tight I did them up!

After that I thought I knew it all, then I got righteously ‘Sheldon Browned’ by someone (I think it was on here -thanks!) on how qrs compress a hollow axle fractionally and that wheel bearings need to be set up with a little slack to accommodate this.

People think a bike is simple because you can see through it!!

[Tiberius]

My son has just bought a bike with through axels - not the ones that have a QR type release, the axels on his bike unscrew with an allen key. When those wheels are in they are going absolutely nowhere. I don't know if they have a downside or if they are considered 'heavy' but I do know that when they're in they're in.

[Jdsk]

Thank you very much for the diagram. I hadn't understood the discussion before that.

(*) Strictly speaking the reaction load on the axle arising from the brake is parallel to the tangent of the disc where the pads are biting. In this situation there is no such thing as a curved force vector, hence the red arrows in the diagram above are inaccurate and misleading.

Yes. And momentum hasn't been a force since about 1687 at the latest. ; - )

It would be great to see a version of the diagram making the same point without those problems...

Jonathan

[Brucey]

With disc brakes, downwards facing dropouts with no LL are a liability.

Thanks for your alarming diagram.
No mention of weight pushing downwards under heavy braking though.

this force is small by comparison with the brake force. Suppose the bike and rider weight 100kg; the highest the vertical force component can be is 100kg. However the brake disc (working diameter i.e. at the middle of the pads) is ~1/5th the wheel diameter (700C wheels) so the reaction loads on it are ~x5 higher. So if you somehow manage a ~1G stop then you are looking at 500kgf reaction loads on the fork ends arising from the brake torque.

Note that, momentarily, the forces may exceed what is possible using a static analysis too.

….. LLs aren't an issue with track nuts either.

with disc brakes you should have secondary wheel retention on the front wheel whether you are using QR skewers or track nuts. Inexpensive bikes with rim brakes are fitted with washers with tangs on; IME these tangs are not strong enough for disc brake use.

cheers

[Samuel D]

But why,outside racing,do bikes need quick release wheels?
It's nothing only psuedo racing wannabe attire.
I have Halo hex bolt skewers on all my bikes because like almost everyone else I don't need quick release wheels

Can’t agree. I like being able to quickly remove a wheel without tools, whether to fix a puncture, load the bicycle into a car, or just wash the frame more easily. It’s not a race, but I remove the wheels often enough to enjoy the convenience.

Besides, what’s the downside? I have rim brakes, so no worries about wheel ejection or brake rub from imprecise axle location.

The only thing that bothers me about quick-release skewers is the need to think about bearing preload, and your hex-bolt skewers wouldn’t change that. To solve that I’d have to go with solid axles, which would mean the additional inconvenience of carrying a 15 mm spanner everywhere … while not racing.

[Samuel D]

People think a bike is simple because you can see through it!!

That’s it.

Meanwhile, the people who ride bicycles today are less likely than their predecessors to know about mechanical things. When factory workers commuted by bicycle and farmers’ kids were road racers, the lowest common denominator of basic mechanical knowledge was higher (at the expense of other knowledge, naturally).

No-one who grew up around machinery would try to close a quick-release skewer by screwing the handle. It’s obvious from the nature of the mechanism that that’s not how it works. But if you grow up playing computer games and send emails for a job, well, maybe.

[reohn2]

But why,outside racing,do bikes need quick release wheels?
It's nothing only psuedo racing wannabe attire.
I have Halo hex bolt skewers on all my bikes because like almost everyone else I don't need quick release wheels

Can’t agree. I like being able to quickly remove a wheel without tools, whether to fix a puncture, load the bicycle into a car, or just wash the frame more easily. It’s not a race, but I remove the wheels often enough to enjoy the convenience.

Besides, what’s the downside? I have rim brakes, so no worries about wheel ejection or brake rub from imprecise axle location.

The only thing that bothers me about quick-release skewers is the need to think about bearing preload, and your hex-bolt skewers wouldn’t change that. To solve that I’d have to go with solid axles, which would mean the additional inconvenience of carrying a 15 mm spanner everywhere … while not racing.

What sold me on hexbolt skewers,which I've posted before,is the ease with which a qr lever can be inadvertantly flicked open if caught on another bike at say a cafe stop when bikes are stacked,or on wire fencing where I may stop to view the scenary or to slow down or stop an opportunist thief from stealing a wheel or the idiot who may think it a wheeze to open the qr's on my wheels when the bike's left unattended
The 'inconvenience' of hexbolt skewers are no inconvenience to me,I rarely puncture(approx twice a year) and the extra 30 seconds at most of undoing the skewers is insignificant at such times.
Wheel ejection with discs isn't a problem with properly set skewers hexbolt or qr cam,though could be with an open qr lever.
Servicing isn't a rushed affair,so again the extra minute at most isn't a problem when taking wheels out,similarly so loading a bike into a car.
I ride a lot off road so call me cautious if you will,but it's one less thing to check or be concerned about in the rough and tumble of the places I like to ride.
There' a difference between need and want
To each his own as they say

[reohn2]

People think a bike is simple because you can see through it!!

That’s it.

Meanwhile, the people who ride bicycles today are less likely than their predecessors to know about mechanical things. When factory workers commuted by bicycle and farmers’ kids were road racers, the lowest common denominator of basic mechanical knowledge was higher (at the expense of other knowledge, naturally).

No-one who grew up around machinery would try to close a quick-release skewer by screwing the handle. It’s obvious from the nature of the mechanism that that’s not how it works. But if you grow up playing computer games and send emails for a job, well, maybe.

Spot on!
The lack of mechanical aptitude of the 3 SinL's within my own family ranges from total to not very good,and these are not stupid people,but put a bike in front of them and set of tools and they don't know where start despite being coached they find simple bike mechanics hard work
Two of them commute by bike and the state of their bikes when they need work on beggars belief

[Mick F]

I have QRs on both the hubs on Mercian, and the Moulton came with two too.

Since then, Moulton has a SA3sp rear hub with nuts, and the front hub - although still QR - is a dyno-hub and is a bit of a fiddle to get back in and connected.
Therefore, if I need to get either wheel out, it's not as quick or simple as Mercian's is.

........ but what the heck?
Does it matter?
Not in the slightest.

If the SP dyno-hub had come with track nuts instead of QR I wouldn't be complaining. It comes out quick enough now that I've filed off the LLs, but to get it back in, you have to rotate the connection ring so the connector lines up with the cable.