Wheel and arm bent

[Roja Doja]

Hello again,

I posted here about a month ago, enquiring about how much I should spend on
a new bike. After reading the many helpful responses, I bought a new Trek
3500 with semi-slick tyres and was happily riding it to work and back every
day.

On Tuesday, I was almost home, cycled off the road onto the pavement near my
house, and before I knew it I'd gone over the front and hit the ground, the
bike flipped over once and then stopped. When I picked myself and the bike
up, I noticed I couldn't push the bike as the wheel was bent quite badly.
Since the bike didn't hit anything else after I fell off, I can only assume
that the wheel must've bent as I hit the kerb, and the bent wheel was what
caused me to crash (it's a perfectly straight bit of road pavement, not the
sort of place where you think anyone could have an accident). In the fall I
fractured my radius near the elbow, which is proving to be a considerable
nuisance!

I hit the kerb between pavement and road where the pavement ramps down to
the road, so the kerb was not more than 2 or 3 cm high. It was at quite an
oblique angle (i.e. I went up the kerb almost parallel to it , not straight
at it) and I was doing about 20mph or less. Should this cause a MTB wheel
to fail?

I took it back to the shop today, expecting sympathy, explanations, a
replacement wheel and perhaps apologies. I didn't get any of that. Looking
at the wheel, they agreed it must've been some sideways force that bent the
wheel, as there were no marks on the rim that would've indicated a big
impact from the front, they looked at it in more detail the workshop, then
said it was too bent to repair and suggested I buy a new one. I was pretty
incensed at this, and suggested that a 3 week old mountain bike wheel should
not be expected to fail going over a 3cm kerb at 20 mph, and that as such it
wasn't fit for its purpose. They looked at me with disbelief, shrugged and
said the only other thing they could do was send it back to Trek for
analysis and see what Trek had to say, so I agreed to that.

Am I going mad? Assuming you believe I'm telling the truth, and that I
really didn't ride it into a wall at 50mph or something similary stupid,
shouldn't a mountain bike wheel take a bit more stick than this? Doesn't the
fact that the wheel is badly bent indicate that it's failed? Shouldn't the
shop be a bit more sympathetic??

Roger

 

[Pete Biggs]

Roja Doja wrote:
...............
> I hit the kerb between pavement and road where the pavement ramps
> down to the road, so the kerb was not more than 2 or 3 cm high.

Can you go back and measure the exact height to check?

> It was at quite an oblique angle (i.e. I went up the kerb almost
> parallel to it , not straight at it) and I was doing about 20mph or
> less. Should this cause a MTB wheel to fail?

First of all, regardless of wheel strength, it's really dangerous to go up
a kerb at an oblique angle, full stop. You can loose control all too
easily, as you've found. Always take any kerbs straight on and at low
speed, easing your weight off the wheels.

Wheels aren't always built very well (in terms of spoke tension) but it's
highly unlikely that the *rim* was not of "merchantable quality" or "fit
for the purpose" when you bought it. Even the cheapest rims tend to stand
up to all normal use ok in this respect.

If the rim is actually dented in (with a distinct dent in the sidewall
edge) then it's probably entirely your fault. That usually means the tyre
was soo soft or you had a severe impact. A minor bump couldn't do that.

If not dented but the wheel is buckled, again that could just be from the
impact, but poor building can contribute: by spokes being under, over or
unevenly tensioned. The supplier could possibly be to blame then, but I
think it's unlikely.

Another very real possibility (especially if no distinct dent in rim) is
that you lost control because of the oblique angle and the wheel buckled
*after* the initial impact. That would definitely be entirely your fault.

Anyway, hope the injury heals quickly (that's more important).

Note: Wheel can be rebuilt using existing hub and spokes. Don't need a
whole new wheel.

~PB

 

[Paul - xxx]

Roja Doja posted ...

> Am I going mad? Assuming you believe I'm telling the truth, and that
> I really didn't ride it into a wall at 50mph or something similary
> stupid, shouldn't a mountain bike wheel take a bit more stick than
> this?

Riding up a kerb is a big no-no .. especially on a cycle. If you kit a kerb
square, or nearly square on, then you can sometimes get away with it, but
more often than not you'll hit at an angle, as you describe, and the tyre
simply won't be able to grip enough to go over the kerb, so 'slips off'
sideways, probably buckling the wheel - this sounds exactly what you've
done. Whenever I go up a kerb I lean way back and lift the front wheel up,
then bunny-hop the rear over the lip, as though it's a jump lip .. I rarely
do this at a very (nearly parallel you said) oblique angle, unless I'm doing
a full bunny-hop, the tyres simply can't cope .. and neither can _any_ wheel
...

> Doesn't the fact that the wheel is badly bent indicate that
> it's failed?

Depends how badly bent badly bent is. If the rim has _any_ kinks or steps,
or dents in it then I'd never use it again. If it's bent further than, say,
30 degrees from straight then again I'd never use it again except in an
emergency, though a lot depends on exactly how it's bent, and is hard to
describe adequately without a picture ..

In the situation you have described the wheel isn't being used in any
'normal' manner of riding, including competition riding, and is almost
definitely unlikely to be covered by any potential warranty.

> Shouldn't the shop be a bit more sympathetic??

Why ? If you ran up a kerb without un-weighting the front-end then you
possibly deserve all you get .. and have been very lucky to get away so
lightly.

PS Get well soon ..


--
Paul

(8(|) Homer rocks ..

 

[Roja Doja]

"Pete Biggs" <pclemantine{remove_fruit}@biggs.tc> wrote in message
news:[email protected]...
> Roja Doja wrote:
> ..............
> > I hit the kerb between pavement and road where the pavement ramps
> > down to the road, so the kerb was not more than 2 or 3 cm high.
>
> Can you go back and measure the exact height to check?

As it's just outside, yes! It varies between about 1.5 to 2.5 cm (which
seems almost nothing kerb-wise)

> > It was at quite an oblique angle (i.e. I went up the kerb almost
> > parallel to it , not straight at it) and I was doing about 20mph or
> > less. Should this cause a MTB wheel to fail?
>
> First of all, regardless of wheel strength, it's really dangerous to go up
> a kerb at an oblique angle, full stop. You can loose control all too
> easily, as you've found. Always take any kerbs straight on and at low
> speed, easing your weight off the wheels.

Easy if you're crossing a road, but I guess if you're coming off a busy
road, you can't really pull out into the middle of the road so you can turn
towards the kerb straight-on can you? At least I've never seen anyone
attempt that! Perhaps I should've pulled over and got off, then lifted the
bike onto the pavement, maybe if I had a race bike with super skinny wheels
I'd have been more inclined to do that, but I assumed it wouldn't be a
problem riding a mountain bike with bit fat tyres, it's never been a problem
before. My arm tells me I was wrong though!

Perhaps the rock-hard tyre pressures and aluminium frame make the new bike
more of a precision-machine, and maybe it's more unforgiving than the ****
old bikes with half-inflated tyres I was used to riding.

> Wheels aren't always built very well (in terms of spoke tension) but it's
> highly unlikely that the *rim* was not of "merchantable quality" or "fit
> for the purpose" when you bought it. Even the cheapest rims tend to stand
> up to all normal use ok in this respect.
>
> If the rim is actually dented in (with a distinct dent in the sidewall
> edge) then it's probably entirely your fault. That usually means the tyre
> was soo soft or you had a severe impact. A minor bump couldn't do that.

No dents, and the tires (and ride) are rock hard, as supplied by the shop.

> If not dented but the wheel is buckled, again that could just be from the
> impact, but poor building can contribute: by spokes being under, over or
> unevenly tensioned. The supplier could possibly be to blame then, but I
> think it's unlikely.

Buckled is probably the word, looking along the line of wheel, it's
bent/warped into a kind of s shape, but looks otherwise ok, no dents, tyres
still pumped up and OK.

> Another very real possibility (especially if no distinct dent in rim) is
> that you lost control because of the oblique angle and the wheel buckled
> *after* the initial impact. That would definitely be entirely your fault.

I'd concede this is a possibility, I'm just not sure how my losing control
and then falling off could cause the wheel to buckle? The bike didn't hit
anything, I had my hands on the handlebars, it just kind of wobbled,
stopped, I went over, the bike tipped over and then hit the ground. Without
my weight on it, I'd have thought that was even less likely to be the cause
of wheel buckling?

> Anyway, hope the injury heals quickly (that's more important).

Thanks.

> Note: Wheel can be rebuilt using existing hub and spokes. Don't need a
> whole new wheel.

Yes, I guess that was what they meant when they talked about a buying a new
one (new rim?). To be honest at that point I was a bit miffed and not
listening attentively. Because of my injury I can't ride it for a few weeks
anyway, so it'll do no harm sending the wheel back to Trek. If they say
there was nothing wrong with it, and I have to buy a new rim and have it
rebuilt, it won't be the end of the world, I guess I'll just learn to
appreciate that wheels can be fragile, and approach kerbs with more caution
in future.

Cheers,
Roger

 

[Roja Doja]

"Paul - ***" <[email protected]> wrote in message
news:[email protected]...
[snip]
> In the situation you have described the wheel isn't being used in any
> 'normal' manner of riding, including competition riding, and is almost
> definitely unlikely to be covered by any potential warranty.

If I was taking about mounting a full kerb, then maybe I'd agree, but I'm
talking about the bit where the pavement ramps down to the road, I mean,
it's almost dead level with the road. I've never before felt I shouldn't
ride up or down these on a bike, (well perhaps other than normally one
wouldn't be on the pavement anyway, but I was outside my own house...) so if
this is really not 'normal' riding, then perhaps they should give some sort
of warning to new riders?

> PS Get well soon ..

Thanks!

Roger

 

[Simon Proven]

Roja Doja wrote:

> "Paul - ***" <[email protected]> wrote in message
> news:[email protected]...
> [snip]
>
>>In the situation you have described the wheel isn't being used in any
>>'normal' manner of riding, including competition riding, and is almost
>>definitely unlikely to be covered by any potential warranty.
>
>
> If I was taking about mounting a full kerb, then maybe I'd agree, but I'm
> talking about the bit where the pavement ramps down to the road, I mean,
> it's almost dead level with the road. I've never before felt I shouldn't
> ride up or down these on a bike, (well perhaps other than normally one
> wouldn't be on the pavement anyway, but I was outside my own house...) so if
> this is really not 'normal' riding, then perhaps they should give some sort
> of warning to new riders?

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.

Simon

 

[Roja Doja]

"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?

Roger

 

[Call me Bob]

On Fri, 28 May 2004 18:26:09 +0000 (UTC), "Roja Doja"
<[email protected]> wrote:


>If I was taking about mounting a full kerb, then maybe I'd agree, but I'm
>talking about the bit where the pavement ramps down to the road, I mean,
>it's almost dead level with the road. I've never before felt I shouldn't
>ride up or down these on a bike, (well perhaps other than normally one
>wouldn't be on the pavement anyway, but I was outside my own house...) so if
>this is really not 'normal' riding, then perhaps they should give some sort
>of warning to new riders?

I'm with you Roja, riding up the dropped part of the kerb that you
described (1.5 - 2.5cm) really isn't dangerous at all IMHO. It
certainly shouldn't be enough of a hazard to threaten the integrity of
your front wheel. I'm a pretty hefty bloke myself and I often clatter
up and down kerbs. This is full kerbs too, not just dropped sections,
and I have no trouble. Granted I don't do this when out on my "best"
bike, delicate wheels and all that, but on either of the hacks I don't
give it a second thought.

The point that has been made about being careful when tackling the
kerb at a shallow angle is valid, but as long as you are aware of the
danger this shouldn't cause a problem. Unweight each wheel as it
passes over the kerb and be positive in your steering. You can improve
the angle of "attack" without needing to sweep out and ride full on at
90 degrees - just a small lean and swerve at the appropriate (last!)
moment will help a lot.

You said you went over the handlebars which means the bike must have
stopped pretty darned sharpish. This isn't what would happen if you'd
just buggered up mounting the kerb at a narrow angle. If it had been
that then your front wheel would have slipped sideways along the edge
of the kerb and your balance would have been thrown off line. You'd
have gone down more sideways onto the kerb than over the bars.

Given how you described the incident I'm at a loss to understand how
the wheel was buckled so badly.

As Pete said, hope the elbow heals fast and you can get back to riding
soon.

Chin up
--

"Bob"

'The people have spoken, the bastards'

Email address is spam trapped.
To reply directly remove the beverage.

 

[Simon Brooke]

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

> Hello again,
>
> I posted here about a month ago, enquiring about how much I should
> spend on
> a new bike. After reading the many helpful responses, I bought a new
> Trek 3500 with semi-slick tyres and was happily riding it to work and
> back every day.
>
> On Tuesday, I was almost home, cycled off the road onto the pavement
> near my house, and before I knew it I'd gone over the front and hit
> the ground, the
> bike flipped over once and then stopped. When I picked myself and the
> bike up, I noticed I couldn't push the bike as the wheel was bent
> quite badly. Since the bike didn't hit anything else after I fell off,
> I can only assume that the wheel must've bent as I hit the kerb, and
> the bent wheel was what caused me to crash (it's a perfectly straight
> bit of road pavement, not the
> sort of place where you think anyone could have an accident). In the
> fall I fractured my radius near the elbow, which is proving to be a
> considerable nuisance!
>
> I hit the kerb between pavement and road where the pavement ramps down
> to
> the road, so the kerb was not more than 2 or 3 cm high. It was at
> quite an oblique angle (i.e. I went up the kerb almost parallel to it
> , not straight
> at it) and I was doing about 20mph or less. Should this cause a MTB
> wheel to fail?

It most certainly should not do. I assume it was the front wheel which
bent? Was your tyre reasonably hard? Had you had any problems with
broken spokes before? Did you break any spokes in this incident? Do you
have any memory of the handlebars twisting round violently in the
incident (wheels are much less strong laterally than they are to forces
perpendicular to their axis)?

The oblique angle may have something to do with it (not generally a good
idea if you can avoid it) but given the very small size of the bump I'm
surprised.

> I was
> pretty incensed at this, and suggested that a 3 week old mountain bike
> wheel should not be expected to fail going over a 3cm kerb at 20 mph,
> and that as such it
> wasn't fit for its purpose.

I'd agree with that.

> Am I going mad? Assuming you believe I'm telling the truth, and that
> I really didn't ride it into a wall at 50mph or something similary
> stupid, shouldn't a mountain bike wheel take a bit more stick than
> this?

Yes. It _must_ do, otherwise it isn't safe. Even quite ordinary off-road
cycling involves hitting things a lot bigger than 3cm at 20mph and
more. One of my regular runs involves coming down a stone chute with
rocks the size of turnips[1] and I must hit them at at least twenty.

> Doesn't the
> fact that the wheel is badly bent indicate that it's failed?
> Shouldn't the shop be a bit more sympathetic??

Yes. But I have some sympathy for them, too. People do do ridiculously
silly things on bikes. Still, in this incident, with a near new bike I
would have thought a free replacement or rebuild would be the least
they could do.

[1] Not your namby pamby little white English turnips.

--
[email protected] (Simon Brooke) http://www.jasmine.org.uk/~simon/
;; Skill without imagination is craftsmanship and gives us
;; many useful objects such as wickerwork picnic baskets.
;; Imagination without skill gives us modern art.
;; Tom Stoppard, Artist Descending A Staircase

 

[Paul - xxx]

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

 

[Andy]

"Roja Doja" <[email protected]> wrote in message
news:[email protected]...
> Hello again,
>
> I posted here about a month ago, enquiring about how much I should spend
on
> a new bike. After reading the many helpful responses, I bought a new Trek
> 3500 with semi-slick tyres and was happily riding it to work and back
every
> day.
>
> On Tuesday, I was almost home, cycled off the road onto the pavement near
my
> house, and before I knew it I'd gone over the front and hit the ground,
the
> bike flipped over once and then stopped. When I picked myself and the
bike
> up, I noticed I couldn't push the bike as the wheel was bent quite badly.
> Since the bike didn't hit anything else after I fell off, I can only
assume
> that the wheel must've bent as I hit the kerb, and the bent wheel was what
> caused me to crash (it's a perfectly straight bit of road pavement, not
the
> sort of place where you think anyone could have an accident). In the fall
I
> fractured my radius near the elbow, which is proving to be a considerable
> nuisance!
>
> I hit the kerb between pavement and road where the pavement ramps down to
> the road, so the kerb was not more than 2 or 3 cm high. It was at quite
an
> oblique angle (i.e. I went up the kerb almost parallel to it , not
straight
> at it) and I was doing about 20mph or less. Should this cause a MTB wheel
> to fail?
>
> I took it back to the shop today, expecting sympathy, explanations, a
> replacement wheel and perhaps apologies. I didn't get any of that.
Looking
> at the wheel, they agreed it must've been some sideways force that bent
the
> wheel, as there were no marks on the rim that would've indicated a big
> impact from the front, they looked at it in more detail the workshop, then
> said it was too bent to repair and suggested I buy a new one. I was
pretty
> incensed at this, and suggested that a 3 week old mountain bike wheel
should
> not be expected to fail going over a 3cm kerb at 20 mph, and that as such
it
> wasn't fit for its purpose. They looked at me with disbelief, shrugged
and
> said the only other thing they could do was send it back to Trek for
> analysis and see what Trek had to say, so I agreed to that.
>
> Am I going mad? Assuming you believe I'm telling the truth, and that I
> really didn't ride it into a wall at 50mph or something similary stupid,
> shouldn't a mountain bike wheel take a bit more stick than this? Doesn't
the
> fact that the wheel is badly bent indicate that it's failed? Shouldn't
the
> shop be a bit more sympathetic??
>
> Roger
>
>


I've "pringled" a front wheel in an offroad crash doing much less than
20mph.
A 20mph impact is pretty heavy duty!

 

[Simon Brooke]

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

>
> "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?

Here we're into terminological problems. A lot of bikes are sold as
'mountain bikes' which aren't expected to do anything more severe than
a sedate amble through the woods. However, a bike that is sold as a
'mountain bike' ought to be able to cope with 'mountain bike'
conditions, and that definitely involves hitting things like tree
roots, broken rock surfaces, faulted surfaces, boulder fields and so
on.

The faults in the Dalbeattie slab are a lot bigger than two centimetres
and you *have* to cross them at a very oblique angle because there's no
other way down:
<URL:http://www.doubleard.co.uk/gallery/Dalbeattie/chipps_slab.html>
<URL:http://www.c8h10n4o2.org/content/mtb/dalbeattie/pages/page8.html>
Nor, on that slope, can you effectively or safely 'unweight' the wheel
or bunny-hop. If your wheel collapsed halfway down that, you'd be
*very* lucky to get away with just a broken arm.

So no, I stick to my opinion. A mountain bike wheel *has* to cope with
more than that.

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

' ' <------- this blank intentionally spaced left

 

[paul]

In article <[email protected]>, [email protected]
says...
> They looked at me with disbelief, shrugged and
> said the only other thing they could do was send it back to Trek for
> analysis and see what Trek had to say, so I agreed to that.
>
IANAL but
Sale of goods act is your friend. 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.
The wheel was NOT fit for purpose, Wheels are meant to be round, yours
isn't any more, ergo it failed under conditions that could reasonalbe be
expected to be encountered. Secondly, your contract is with the retailer
not the manufacture, it is their responsibility to refund or replace.

Steps to take, read this
http://www.dti.gov.uk/ccp/topics1/facts/salegoodsact.htm points one to
five inc are the pertenent ones
go back to the shop and ask for are fund in accordance with the sale of
goods act
right it all down and visit the shop again giving them a copy. tell them
that your next step will be to contact the tradign standards office
contact TS, and also get a small claims court claim form
SUE the bastards.
Main problmes I see are a) you've already let them have the wheel,
b)It's your word that you didn.t do a drop off from the top of your
house

Good luck.

oh and I hope your arm heals soon.
--
..paul

If at first you don't succeed...
Skydiving is probably not the sport for you.

 

[Simon Brooke]

in message <[email protected]>, Paul - *** ('[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.

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>

--
[email protected] (Simon Brooke) http://www.jasmine.org.uk/~simon/
There's nae Gods, an there's precious few heroes
but there's plenty on the dole in th Land o th Leal;
And it's time now, tae sweep the future clear o
th lies o a past that we know wis never real.

 

[Doki]

Roja Doja wrote:

> Am I going mad? Assuming you believe I'm telling the truth, and that
> I really didn't ride it into a wall at 50mph or something similary
> stupid, shouldn't a mountain bike wheel take a bit more stick than
> this? Doesn't the fact that the wheel is badly bent indicate that
> it's failed? Shouldn't the shop be a bit more sympathetic??

I'd say it's a dodgy wheel, or that it's not been built quite right and has
started to go slightly out of true then buckled as you hit the kerb. FWIW,
as a kid I once had a new front wheel after buckling the old one (probably
from riding straight up normal 6" kerbs), and whilst riding down the street
the new rim gave up, splitting at the dowelled section where it's joined.
Bike shop bloke had never seen it happen before, and he's been around a
while.

 

[Eatmorepies]

> Riding up a kerb is a big no-no .. especially on a cycle. If you kit a
kerb
> square, or nearly square on, then you can sometimes get away with it, but
> more often than not you'll hit at an angle, as you describe, and the tyre
> simply won't be able to grip enough to go over the kerb, so 'slips off'
> sideways, probably buckling the wheel - this sounds exactly what you've
> done. Whenever I go up a kerb I lean way back and lift the front wheel
up,
> then bunny-hop the rear over the lip, as though it's a jump lip .. I
rarely
> do this at a very (nearly parallel you said) oblique angle, unless I'm
doing
> a full bunny-hop, the tyres simply can't cope .. and neither can _any_
wheel

No it's not.

A well built wheel with a decent rim will laugh off curbs. I use Mavic 517
(or their modern equivalent) rims and double butted SS spokes. I then bash
them about over sticks and stones, perpendicular and at oblique angles.

I agree that you need to engage in weight transfer - but for a 1" curb?

John

 

[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

 

[Pete Biggs]

Roja Doja wrote:

>>> I hit the kerb between pavement and road where the pavement ramps
>>> down to the road, so the kerb was not more than 2 or 3 cm high.
>>
>> Can you go back and measure the exact height to check?
>
> As it's just outside, yes! It varies between about 1.5 to 2.5 cm
> (which seems almost nothing kerb-wise)

I agree that's pretty shallow (I wouldn't normally expect that to damage a
wheel) but 20 mph was a bit fast for it.

>>> It was at quite an oblique angle (i.e. I went up the kerb almost
>>> parallel to it , not straight at it) and I was doing about 20mph or
>>> less. Should this cause a MTB wheel to fail?
>>
>> First of all, regardless of wheel strength, it's really dangerous to
>> go up a kerb at an oblique angle, full stop. You can loose control
>> all too easily, as you've found. Always take any kerbs straight on
>> and at low speed, easing your weight off the wheels.
>
> Easy if you're crossing a road, but I guess if you're coming off a
> busy road, you can't really pull out into the middle of the road so
> you can turn towards the kerb straight-on can you?

Just out to the middle of the inside lane would do if speed is low enough.
I do it all the time. If you can't do that, yes, get off the bike! ...or
stop and lift front wheel up, etc.

> At least I've
> never seen anyone attempt that! Perhaps I should've pulled over and
> got off, then lifted the bike onto the pavement, maybe if I had a
> race bike with super skinny wheels I'd have been more inclined to do
> that, but I assumed it wouldn't be a problem riding a mountain bike
> with bit fat tyres, it's never been a problem before. My arm tells
> me I was wrong though!
>
> Perhaps the rock-hard tyre pressures and aluminium frame make the new
> bike more of a precision-machine, and maybe it's more unforgiving
> than the **** old bikes with half-inflated tyres I was used to riding.

Hard tyres actually protect the rim in the worst impacts (because they
don't compress all the way to rim), hence you didn't get a dent, but wider
softer tyres will increase grip and traction at least.

>> Another very real possibility (especially if no distinct dent in
>> rim) is that you lost control because of the oblique angle and the
>> wheel buckled
>> *after* the initial impact. That would definitely be entirely your
>> fault.
>
> I'd concede this is a possibility, I'm just not sure how my losing
> control and then falling off could cause the wheel to buckle? The
> bike didn't hit anything, I had my hands on the handlebars, it just
> kind of wobbled, stopped, I went over, the bike tipped over and then
> hit the ground. Without my weight on it, I'd have thought that was
> even less likely to be the cause of wheel buckling?

Your weight might have been on it for a moment but all sorts of crashes
and falls can result in a buckled a wheel. Just the bike's own weight
even just the wheel's weight can be enough if impact with object/ground is
fast or awkward enough.

Frankly, I don't know how wheels get buckled *exactly*. It's a highly
technical subject, but I know there's a lot of luck involved. Perhaps the
wheel would have survived in another incident just like it if only one
variable was slightly different: maybe just 0.2mph different, 1 degree
different, etc. I've survived some massive impacts with no damage at all,
yet had rims written off by what seemed like a minor bump.

As I mentioned, the wheel could have been built poorly but that's
virtually impossible to prove now. Wheels with optimum spoke tension
survive this kind of thing better, even with super-light rims.

You could try the rec.bicycles.tech newsgroup. Jobst Brandt, author of
the world famous The Bicycle Wheel book, will answer with a bit of luck
(if he's not away on holiday). Plenty of other wheel experts there as
well. But don't expect any sympathy there: they're a hard bunch!

~PB

 

[Dave Kahn]

On Fri, 28 May 2004 18:10:03 +0000 (UTC), "Roja Doja"
<[email protected]> wrote:

>> Another very real possibility (especially if no distinct dent in rim) is
>> that you lost control because of the oblique angle and the wheel buckled
>> *after* the initial impact. That would definitely be entirely your fault.
>
>I'd concede this is a possibility, I'm just not sure how my losing control
>and then falling off could cause the wheel to buckle? The bike didn't hit
>anything, I had my hands on the handlebars, it just kind of wobbled,
>stopped, I went over, the bike tipped over and then hit the ground. Without
>my weight on it, I'd have thought that was even less likely to be the cause
>of wheel buckling?

Bicycle wheels are amazingly strong for their weight, but only in one
plane. Even the best wheels are not designed to withstand large side
loads. From your description of the accident I think the most likely
explanation is that you lost control from mounting the kerb and the
steering turned enough that the wheel stopped rotating. This could
easily have been enough both to buckle it and to throw you over the
top.

>> Anyway, hope the injury heals quickly (that's more important).

Seconded. When you're riding again you should either take kerbs
(gently) at 90 degrees, or for real street cred learn to bunny hop
onto them. As others have said you do not need a complete new wheel,
just a rim. The spokes can be safely re-used except for any that have
got kinks in them.

--
Dave...

Get a bicycle. You will not regret it. If you live. - Mark Twain