Wheel and arm bent

[Mark South]

"anonymous coward" <[email protected]> wrote in message
news[email protected]...

> It might pay to check the hub before getting the wheel
> rebuilt. The flanges (that hold the spokes) might have
> cracked, and check the axle moves smoothly.

While checking the hub is a good idea, the failure mode
of collapsing wheels involves the spokes losing tension,
so if there are no snapped spokes the hub will probably
check out fine. In that case, the spokes can probably be
re-used as well.
--

-- M.

 

[Tony Raven]

Doki wrote:
>
> So you mean when I'm bombing down a local lane at 20mph I
> ought to be expecting my front wheel to fold up? It's a
> mountain bike wheel for christ's sake.

It will if you turn it across your direction of travel too
fast which is what happened here when the wheel caught the
kerb obliquely. Try it sometime. Its in the original
Richards Bicycle Book (don't know about the newer
versions) as the quickest way to stop at the expense of
wrecking your wheel.

Tony

 

[Simon Brooke]

in message <[email protected]>, Doki
('[email protected]') wrote:

>
>
> Pete Biggs wrote:
>> paul wrote:
>>
>>> You bought an ATB/MTB whatever, and you can therefore
>>> reasonably expectg it to cope with 2cm bumbs in the
>>> road, no matter that it was a droped kerb, nor what
>>> angle you hit it at.
>>
>> You might expect the wheel not to buckle as it hits a 2
>> cm bump what kind of magic can it have to prevent the
>> rider crashing when he does something stupid? The wheel
>> could have buckled after the initial impact. The wheel
>> wasn't responsible for the crash. The crash could have
>> happened with ANY wheel. You can not reasonably expect an
>> MTB wheel to survive all 20 mph crashes.
>
> So you mean when I'm bombing down a local lane at 20mph I
> ought to be expecting my front wheel to fold up? It's a
> mountain bike wheel for christ's sake.

No. It's virtually impossible to get a bike wheel to fold up
by impacts perpendicular to its axis. It's both incredibly
strong and incredibly springy. That's why I asked if the OP
felt the handlebars jerk round - because, as other people
have said, wheels are very much weaker sideways, so if the
impact with the kerb caused a big, sudden steering
deflection that might cause it.

But mountain biking would be impossible if wheels folded up
when they hit a 1 inch bump at twenty miles an hour.

--
[email protected] (Simon Brooke)
http://www.jasmine.org.uk/~simon/

;; When all else fails, read the
distractions.

 

[Pete Biggs]

Doki wrote:

>> You might expect the wheel not to buckle as it hits a 2
>> cm bump what kind of magic can it have to prevent the
>> rider crashing when he does something stupid? The wheel
>> could have buckled after the initial impact. The wheel
>> wasn't responsible for the crash. The crash could have
>> happened with ANY wheel. You can not reasonably expect an
>> MTB wheel to survive all 20 mph crashes.
>
> So you mean when I'm bombing down a local lane at 20mph I
> ought to be expecting my front wheel to fold up? It's a
> mountain bike wheel for christ's sake.

Read what I wrote please. Can't expect it to survive ALL
20 mph CRASHES. Hitting a 2cm bump doesn't count as a
"crash" but hitting it in such a way that you loose
control and go over the handlebars and your bike hits the
road, does. Get it?

~PB

 

[Anonymous]

Roja Doja posted ...

> "Simon Proven" wrote: [snip]
>> Dropped kerbs can be badly aligned. You described it
>> being up to an inch high, which I reckon's too much for
>> mounting at an oblique angle. If meant for cycling up
>> (i.e. you were joining a cycle path on the pavement) then
>> I'd consider a complaint to the council.
>>
>> I wouldn't ever attempt to ride up such a high kerb
>> at 20mph.
>
> Fair enough, given opinion so far, I forsee I won't be
> attempting to ride up dropped kerbs again.
>
> I don't think I'd like to actually put the bike to its
> supposed use then, and ride it down a mountain, if a 1.5cm-
> 2.5cm lip is enough to cause problems?

It's not just the height of the kerb, it's your manner of
approach that's part of the problem too. In normal
circumstances you can hit rocks etc that are far bigger, but
they'll not be quite as solid as a solid thing and will give
somewhat. A kerb doesn't give ...

I'd say, based upon your descriptions, that it's a
combination of circumstances that led to the wheel buckling
and isn't at all indicative of a particular problem with
the wheel.

Dropped kerbs are mostly fine to ride up, I do it all the
time without thinking, but not when almost parallel, as you
first described ..

--
Paul

(8(|) Homer rocks ..

 

[Tony Raven]

Roja Doja wrote:
>
> Fair enough, given opinion so far, I forsee I won't be
> attempting to ride up dropped kerbs again.
>
> I don't think I'd like to actually put the bike to its
> supposed use then, and ride it down a mountain, if a 1.5cm-
> 2.5cm lip is enough to cause problems?
>

Its a fairly common mistake and its surprising how small a
ridge can catch you out if taken obliquely, especially if
you are not expecting it. Its good practice to approach such
obstacles at as acute an angle as circumstances reasonably
allow. This will also stand you in good stead off-road in
dealing with ruts etc. Often if you try to get out a rut
without helping the wheel with a bit of lifting all that
will happen in the wheel will crab along the side of the
rut. You will need to unweight and lift the wheel to get it
out and then do the same with the rear wheel otherwise it
too will crab. Mountain biking isn't about pointing a bike
down a mountain and letting it go. You need to build up
skills either by trial and error or by reading up about it.
Master those techniques and you may find yourself able to
mount a full height kerb at an oblique angle without
problems on your current bike.

Tony

 

[Mark South]

"Tony Raven" <[email protected]> wrote in message
news:[email protected]...
> Doki wrote:
> >
> > So you mean when I'm bombing down a local lane at 20mph
> > I ought to be expecting my front wheel to fold up? It's
> > a mountain bike wheel for christ's sake.
>
> It will if you turn it across your direction of travel too
> fast which is what happened here when the wheel caught the
> kerb obliquely. Try it sometime. Its in the original
> Richards Bicycle Book (don't know about the newer
> versions) as the quickest way to stop at the expense of
> wrecking your wheel.

Having looked up Jobst's estimates in The Book, he says that
the lateral strength of a wheel is about 10% of its axial
strength, so a relatively small sideways load will fold it.

Basically, Sale of Goods or not, bicycle wheels are not
designed to take sideways loads.
--
Mark South: World Citizen, Net Denizen

 

[Ambrose Nankive]

In news:[email protected],
Tony Raven <[email protected]> typed:
> Doki wrote:
>>
>> So you mean when I'm bombing down a local lane at 20mph I
>> ought to be expecting my front wheel to fold up? It's a
>> mountain bike wheel for christ's sake.
>
> It will if you turn it across your direction of travel too
> fast which is what happened here when the wheel caught the
> kerb obliquely. Try it sometime. Its in the original
> Richards Bicycle Book (don't know about the newer
> versions) as the quickest way to stop at the expense of
> wrecking your wheel.

And presumably wrecking your teeth, too. If I were trying to
avoid a solid object I'd rather take my chance on flying
into it and stopping my body that way than collapsing my
wheel and launching myself headfirst into the obstacle.

A

 

[Doki]

Pete Biggs wrote:
> Doki wrote:
>
>>> You might expect the wheel not to buckle as it hits a 2
>>> cm bump what kind of magic can it have to prevent the
>>> rider crashing when he does something stupid? The wheel
>>> could have buckled after the initial impact. The wheel
>>> wasn't responsible for the crash. The crash could have
>>> happened with ANY wheel. You can not reasonably expect
>>> an MTB wheel to survive all 20 mph crashes.
>>
>> So you mean when I'm bombing down a local lane at 20mph I
>> ought to be expecting my front wheel to fold up? It's a
>> mountain bike wheel for christ's sake.
>
> Read what I wrote please. Can't expect it to survive ALL
> 20 mph CRASHES. Hitting a 2cm bump doesn't count as a
> "crash" but hitting it in such a way that you loose
> control and go over the handlebars and your bike hits the
> road, does. Get it?

Yep. I should have read it rather than skimmed through it
before I replied. I'd expect to be able to ride up kerbs on
my tyres (thought at a relatively steep angle), but I
imagine slicks are rather smaller than my MTB tyres.

 

[Tony Raven]

Doki wrote:
>
> Yep. I should have read it rather than skimmed through it
> before I replied. I'd expect to be able to ride up kerbs
> on my tyres (thought at a relatively steep angle), but I
> imagine slicks are rather smaller than my MTB tyres.

I'm extremely wary of small kerbs at oblique angles -
they've caught me out too often on everything from road
bikes to motorbikes. I always make a point now of crossing
them by turning across them.

Tony

 

[Tony Raven]

Simon Brooke wrote:
>
> A bike which can't cope with that can't really be sold as
> a mountain bike. It is after all, an official government
> owned, government built, government sponsored cycle track:
> <URL:http://www.7stanes.gov.uk>

One The Slab isn't for inexperienced riders. If you
don't know what you are doing it would be very easy to
hurt yourself which is why they have installed the
qualifiers on it.

Second that sort of riding is not for every sort of mountain
bike. Downhill racers and Freeriders break equipment all the
time and they have some of the strongest bikes available.
Does that disqualify them from being mountain bikes?

Third wheels are not designed to withstand sideways loads
very well. Try riding your bike along a tram track and see
how your wheel gets on and then try claiming under the "fit
for purpose" laws that it happened on a government owned,
government built road

Tony

 

[Anonymous]

Simon Brooke posted ...

> ('[email protected]') wrote:
>
>> Roja Doja posted ...
>>
>>> "Simon Proven" wrote: [snip]
>>>> Dropped kerbs can be badly aligned. You described it
>>>> being up to an inch high, which I reckon's too much for
>>>> mounting at an oblique angle. If meant for cycling up
>>>> (i.e. you were joining a cycle path on the pavement)
>>>> then I'd consider a complaint to the council.
>>>>
>>>> I wouldn't ever attempt to ride up such a high kerb at
>>>> 20mph.
>>>
>>> Fair enough, given opinion so far, I forsee I won't be
>>> attempting to ride up dropped kerbs again.
>>>
>>> I don't think I'd like to actually put the bike to its
>>> supposed use then, and ride it down a mountain, if a 1.5cm-
>>> 2.5cm lip is enough to cause problems?
>>
>> It's not just the height of the kerb, it's your manner of
>> approach that's part of the problem too. In normal
>> circumstances you can hit rocks etc that are far bigger,
>> but they'll not be quite as solid as a solid thing and
>> will give somewhat. A kerb doesn't give ...
>
> I've just posted links to two photos of the Slab. Believe
> me, there isn't a kerb - there isn't a building - in the
> whole of Europe as sold as that. London Embankment was
> built with granite from Dalbeattie, but the slab has never
> been cut. It isn't blocks joined together with mortar.
> It's just one solid knobble of the planet's crust. One
> piece of granite, with gnarly big faults in it which run
> across the only track down at about 20 degrees.

Different thing entirely, and normally only used and only
recommended for use by experienced cyclists. This guy's a
novice and simply did it wrong ..

> A bike which can't cope with that can't really be sold as
> a mountain bike.

I guess my mates Santa Cruz Heckler isn't a mountain bike
then ? His rear wheel collapsed on similar steps in the
Derbyshire hills ... The Trek 3500 the OP is talking about
is not a bike marketed and meant for this style of mountain
biking .. it's a £200 'starter' mountain bike. However an
experienced rider would probably easily get it safely down
the steps, but a novice, such as the OP, may easily struggle
with a kerb ..

> It is after all, an official government owned, government
> built, government sponsored cycle track:
> <URL:http://www.7stanes.gov.uk>

That makes it alright to use for anyone then ?

--
Paul

(8(|) Homer rocks ..

 

[psycho.fifer]

I think you must have put your weight on your front wheel during the crash. The kerb cannot have done this to your wheel from what I have read. If the wheel is bent into an s you can bend it back without tighening or loosening any spokes. The wheel has warped due to the weight it has endured laterally. Next time this happens make sure your tyre is rock hard, take the wheel in both hands and wallop the tyre hard off the ground at the appropriate location(s). The wheel will (probably!) spring back into shape and be nearly true. I've done this many times and it is a good fix if you're miles from home. Depending on the wheel you may still need a replacement after this type of action and I wouldn't recommend it if your riding down a mountain! To my knowledge, there is one other way of bending a wheel into an s and that is to overtighten the spokes. I am speaking from experience here and with this particular wheel all I had to do was loosen all the spokes. Wheel building is good clean fun!
I regularly go up larger kerbs on my racer with skinny rims and tyres (700x23C). It is risky at small angles but again if you slightly lift your front wheel and then your back wheel using your feet (all cyclist's sould be physically attached to their pedals) it's no problem and I've easily done this on my racer at 20mph+

Good luck and please don't sue me if anyone injures themselves taking my advice!