Pedal Falls Off

[Elisa Francesca Roselli]

So here I am with my beloved Flyzipper, a Dahon Impulse P21, at the
doctor's because I didn't know how to change an inner tube (put the
wheel on backwards). I resumed my commute to work with Behemoth, a
monstrous Dutch bike.

As some may recall, the last we heard from Behemoth was when I had some
strapless mini clips fitted to the pedals to help me get her lumbersome
weight up the many hills surrounding Paris (which is why, incidentally,
so few people have Dutch bikes here, as I now know from hindsight).
Although everyone encouraged me to persist with the mini-clips, I found
that they made a difficult bike even more unrideable. Behemoth has
always been very hard to start. The added conundrum of having to thread
my feet into clips caused a few near-accidents at intersections.

So I gave up on the clips. Since I no longer have an LBS worthy of the
name, I simply bought a new pair of pedals and attempted to screw them
on myself. They are mountain bike pedals and much easier to use, with
their toothed metal structure, than the awful, eel-slippery sugarloaf
rubber pedals Behemoth was born with.

Today is the second time I ride out with Beth since I changed the
pedals. Puffing up a hill in first gear, I find the going harder and
harder, and the right pedal showing a sort of assymetric grind, twisting
my foot a few degrees at every revolution. I carry on, past the top of
the hill and coast down into a village. Right there in the center of
town, with a considerate motorist behind me, I abruptly lose the pedal,
which clatters off onto the pavement. Motorist stops in time not to
back-end me or crush the pedal, and waits patiently while I gather up
pedal and Behemoth splattered clear across the road with all the
contents of her basket.

Stopped nearby is a builder with a pickup truck and some wrenches of
appropriate size, who helps me screw the pedal on again. He tightens it
as much as he can.

I resume my route but after only a few hundred yards, I can feel the
pedal going wobbly again. Not wanting to trust indefinitely to the
kindness of motorists, I decide to walk the remaining 7 km to work.

Now what? I realize I cannot trust that pedal. By and by, I see no
reason to trust the other pedal either. Is it that the thread where it
screws in is shot, due to my inability to screw it on straight in the
first place? (For I am constitutionally incapable of screwing straight.
Read into that whatever you please.) Does this mean replacement of not
just pedals but also pedal cranks? Or is there any endemic reason why
one cannot have steel MTB pedals on a aluminum cranks?

Evidently not my week for cycling.

Elisa Francesca Roselli
Ile de France

[David Martin]

On 16/5/05 8:22 am, in article ,
"Elisa Francesca Roselli" > wrote:

> Now what? I realize I cannot trust that pedal. By and by, I see no
> reason to trust the other pedal either. Is it that the thread where it
> screws in is shot, due to my inability to screw it on straight in the
> first place? (For I am constitutionally incapable of screwing straight.
> Read into that whatever you please.) Does this mean replacement of not
> just pedals but also pedal cranks? Or is there any endemic reason why
> one cannot have steel MTB pedals on a aluminum cranks?

Sounds like you cross threaded the pedal first time and stripped the
threads. Was it hard to put on the first time you did it?
Did you screw it in the right way (the right hand pedal screws in the other
way than the left hand one.)

...d

[Elisa Francesca Roselli]

David Martin a écrit :
> On 16/5/05 8:22 am, in article ,
> "Elisa Francesca Roselli" > wrote:

> Sounds like you cross threaded the pedal first time and stripped the
> threads. Was it hard to put on the first time you did it?

Yes, that's probably it. I did have a hard time screwing them in.

Can a pedal that has been cross-threaded and ridden (further damaging
the thread) still be used safely?

Elisa Francesca Roselli
Ile de France

[Peter Clinch]

Elisa Francesca Roselli wrote:

> Now what? I realize I cannot trust that pedal. By and by, I see no
> reason to trust the other pedal either. Is it that the thread where it
> screws in is shot, due to my inability to screw it on straight in the
> first place?

Sounds entirely possible from the description, so you'll quite possibly
need a new crank arm on the wobbly side, but to check that use the old
pedal for a few circuits of the block where you live and see if that's
okay. If it is then just a new pedal should suffice.

> Or is there any endemic reason why
> one cannot have steel MTB pedals on a aluminum cranks?

No, pedals are pretty much freely interchangeable.

The only Sneaky Bit is that the left pedal has a reversed thread, so
tightens up anticlockwise. There is often, but not always, a G/D or R/L
indicator, but otherwise it's a case that if it won't go on, you've got
the wrong one... It's best to put a little grease on the threads before
putting the pedals on, as that way they'll come off again when you want
without requiring two days of penetrating oil, a ******* Size pedal
spanner and a team of trained body builders. The reason for the
reversed LH thread is that the act of pedalling should naturally tighten
both sides, so you don't have to worry about the grease making them
spontaneously fall off.

Pete.
--
Peter Clinch Medical Physics IT Officer
Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital
Fax 44 1382 640177 Dundee DD1 9SY Scotland UK
net http://www.dundee.ac.uk/~pjclinch/

[Chris Eilbeck]

Elisa Francesca Roselli > writes:

> David Martin a écrit :
>> On 16/5/05 8:22 am, in article ,
>> "Elisa Francesca Roselli" > wrote:
>
>> Sounds like you cross threaded the pedal first time and stripped the
>> threads. Was it hard to put on the first time you did it?
>
> Yes, that's probably it. I did have a hard time screwing them in.
>
> Can a pedal that has been cross-threaded and ridden (further damaging
> the thread) still be used safely?

If the thread is trashed then you'll probably have to replace the
crank or get a helicoil (thread repair) fitted to it. Depends how
much you'd like to keep the original crank in the future but I'd be
tempted to bond the pedal in to the crank using JB Weld seeing as it's
pretty much a write-off in any case.

Chris
--
Chris Eilbeck
MARS Flight Crew http://www.mars.org.uk/
UKRA #1108 Level 2 UYB
Tripoli UK Member #9527 LSMR

[Jim Smith]

Elisa Francesca Roselli > writes:

> David Martin a écrit :
>> On 16/5/05 8:22 am, in article ,
>> "Elisa Francesca Roselli" > wrote:
>
>> Sounds like you cross threaded the pedal first time and stripped the
>> threads. Was it hard to put on the first time you did it?
>
> Yes, that's probably it. I did have a hard time screwing them in.
>
> Can a pedal that has been cross-threaded and ridden (further damaging
> the thread) still be used safely?

I wonder if you some how got the pedals switched. The right pedal
should screw in clockwise, and the left pedal should screw in
counterclockwise.

[David Martin]

>> Can a pedal that has been cross-threaded and ridden (further damaging
>> the thread) still be used safely?

As a paperweight? Or as something to throw at errant dogs/taxi drivers?

Typically the pedal will suffer no damage through being cross threaded but
the crank will be shot. This is in accordance with murphy's law of
engineering maintenance:

"If two components are assembled incorrectly, the cheaper and easiset to
replace will be undamaged but the more expensive and harder to replace will
be a write-off."

...d

[Elisa Francesca Roselli]

David Martin a écrit :

> "If two components are assembled incorrectly, the cheaper and easiset to
> replace will be undamaged but the more expensive and harder to replace will
> be a write-off."

Oh dear. They may have trouble finding a replacement crank for this rare
imported bike. And walking her back to her dealer in the 16th
arrondissment will take the better part of an afternoon.

At least I had the sense to wear my pedometre this morning. So I can
still quantify the exercize.

EFR
Ile de France

[Peter Clinch]

Elisa Francesca Roselli wrote:

> Oh dear. They may have trouble finding a replacement crank for this rare
> imported bike.

No, cycle transmissions, and especially bits of them like crank arms,
are interchangeable to quite a high degree. Much like wheels, tyres, etc.

There shouldn't be any trouble getting it replaced at any bike shop that
has heard of spare parts.

Pete.
--
Peter Clinch Medical Physics IT Officer
Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital
Fax 44 1382 640177 Dundee DD1 9SY Scotland UK
net http://www.dundee.ac.uk/~pjclinch/

[dkahn400]

Jim Smith wrote:
> Elisa Francesca Roselli > writes:
>
> > David Martin a =E9crit :
> >> On 16/5/05 8:22 am, in article
,
> >> "Elisa Francesca Roselli" > wrote:
> >
> >> Sounds like you cross threaded the pedal first time and stripped
> >> the threads. Was it hard to put on the first time you did it?
> >
> > Yes, that's probably it. I did have a hard time screwing them in.
> >
> > Can a pedal that has been cross-threaded and ridden (further
> > damaging the thread) still be used safely?
>
> I wonder if you some how got the pedals switched. The right pedal
> should screw in clockwise, and the left pedal should screw in
> counterclockwise.

Cross-threading is one thing, but if the pedals were offered up on the
wrong side I don't see how Elisa Francesca would have got them to go on
at all.

--=20
Dave...

[David Martin]

On 16/5/05 12:22 pm, in article
om, "dkahn400"
> wrote:

> Jim Smith wrote:
>> Elisa Francesca Roselli > writes:
>>
>>> David Martin a écrit :
>>>> On 16/5/05 8:22 am, in article
> ,
>>>> "Elisa Francesca Roselli" > wrote:
>>>
>>>> Sounds like you cross threaded the pedal first time and stripped
>>>> the threads. Was it hard to put on the first time you did it?
>>>
>>> Yes, that's probably it. I did have a hard time screwing them in.
>>>
>>> Can a pedal that has been cross-threaded and ridden (further
>>> damaging the thread) still be used safely?
>>
>> I wonder if you some how got the pedals switched. The right pedal
>> should screw in clockwise, and the left pedal should screw in
>> counterclockwise.
>
> Cross-threading is one thing, but if the pedals were offered up on the
> wrong side I don't see how Elisa Francesca would have got them to go on
> at all.

My guess would be a slightly undersized pedal thread and oversized crank
thread, cross threading and hence stripping of the crank thread.

...d

[Tony Raven]

dkahn400 wrote:
>
> Cross-threading is one thing, but if the pedals were offered up on the
> wrong side I don't see how Elisa Francesca would have got them to go on
> at all.
>

You are forgetting that the designers of foolproof systems always
underestimate the ingenuity of fools ;-)

--
Tony

"A facility for quotation covers the absence of original thought" Lord
Peter Wimsey (Dorothy L. Sayers)

[Jim Smith]

"dkahn400" > writes:

> Jim Smith wrote:
>> Elisa Francesca Roselli > writes:
>>
>> > David Martin a écrit :
>> >> On 16/5/05 8:22 am, in article
> ,
>> >> "Elisa Francesca Roselli" > wrote:
>> >
>> >> Sounds like you cross threaded the pedal first time and stripped
>> >> the threads. Was it hard to put on the first time you did it?
>> >
>> > Yes, that's probably it. I did have a hard time screwing them in.
>> >
>> > Can a pedal that has been cross-threaded and ridden (further
>> > damaging the thread) still be used safely?
>>
>> I wonder if you some how got the pedals switched. The right pedal
>> should screw in clockwise, and the left pedal should screw in
>> counterclockwise.
>
> Cross-threading is one thing, but if the pedals were offered up on the
> wrong side I don't see how Elisa Francesca would have got them to go on
> at all.

Unlikely, yes. However, I just recently took an old frame I had just
acquired to the local bike shop to have the bottom bracket threads
chased. I decided to have the work done because the BB didn't want to
screw in easily, and some of the threads looked a bit funky. The work
was completed as I wandered around the shop, and I took the frame
home. Sure enough, the frame had nice clean right hand threads on the
right side, and nice clean left hand threads on the left side. The
kid who had screwed the taps in and the frame up had nothing to offer
in his defense other than his adamant claim that the taps screwed in
with very little resistance.

[[email protected]]

Elisa,

I expect when you replaced the pedal you did not tighten it
sufficiently. As you pedalled precession served to work the pedal
loose. Unfortunately as the pedal became very loose the axis it rotated
on becomes magnified (forms a cone) and it efficiently strips the
threads in the crank (the pedal axle is steel and the crank soft
alloy). Then the pedal drops off (or comes away with your foot if
clipless). When you come to replace it there isn't enough thread and
the pedal won't tighten onto the crank.

Repair of the crank requires a Helicoil to be fitted. This is a big
thick washer which is threaded on the outer and inner surfaces. A
competent bike shop should be able to fit this by drilling and
threading a larger hole for the helicoil and screwing the pedal into
the new thread. The final repair will be indistinguishable from new and
next time be sure to tighten the pedal with a longer spanner.

Although pedals are reverse threaded to tighten onto the crank when
pedalling, they need to be pretty tight to start with, otherwise the
above can happen.

This gem of information was brought to from the encyclopaedia of
cycling (ahem) experience...Took 6 miles and a stronglight 80 crank (if
anyone is interested)
..
Kind regards,

Daren
--
remove outer garment for reply

[Elisa Francesca Roselli]

a écrit :

> I expect when you replaced the pedal you did not tighten it
> sufficiently. As you pedalled precession served to work the pedal
> loose. Unfortunately as the pedal became very loose the axis it rotated
> on becomes magnified (forms a cone) and it efficiently strips the
> threads in the crank (the pedal axle is steel and the crank soft
> alloy). Then the pedal drops off (or comes away with your foot if
> clipless). When you come to replace it there isn't enough thread and
> the pedal won't tighten onto the crank.

I believe it was exactly so. There is a luxury LBS just at the bottom of
the hill on my way home from work, about 2 kms from here. I will walk
Behemoth there tomorrow (bike shops in France rarely open Mondays) and
nab a lift home from a cager colleague this evening.

I hope the people at the shop, which sells Cannondales and such like,
will understand the term helicoil.

EFR
Ile de France

[Peter Clinch]

Elisa Francesca Roselli wrote:

> I hope the people at the shop, which sells Cannondales and such like,
> will understand the term helicoil.

Say what the problem is, ask them to fix it. Don't worry about exactly
*how*, especially as they can assess it first hand and transatlantic
jargon may not be the same.

Pete.
--
Peter Clinch Medical Physics IT Officer
Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital
Fax 44 1382 640177 Dundee DD1 9SY Scotland UK
net http://www.dundee.ac.uk/~pjclinch/

[di]

"Elisa Francesca Roselli" > wrote in message
...
> a écrit :

> I believe it was exactly so. There is a luxury LBS just at the bottom of
> the hill on my way home from work, about 2 kms from here. I will walk
> Behemoth there tomorrow (bike shops in France rarely open Mondays) and nab
> a lift home from a cager colleague this evening.
>
> I hope the people at the shop, which sells Cannondales and such like, will
> understand the term helicoil.
>
> EFR
> Ile de France




The kits to install a Helicoil thread repair are expensive, so unless a shop
already has a kit the cost will probably be more than a new crank arm would
be. For reference of what a Helicoil is see:

http://www.emhart.com/products/helicoil.html

By the way, Helicoil is a brand name, the process may be known by another
name in France.

[Alan Braggins]

In article >, Tony Raven wrote:
>dkahn400 wrote:
>>
>> Cross-threading is one thing, but if the pedals were offered up on the
>> wrong side I don't see how Elisa Francesca would have got them to go on
>> at all.
>
>You are forgetting that the designers of foolproof systems always
>underestimate the ingenuity of fools ;-)

In the case of a self-tapping pedal, I think it's not so much the
ingenuity as the torque required. I once undid a bearing retainer
on a car part by having two of us jumping on six foot scaffold poles,
but not many pedal spanners would take that.

(I recently tore a pedal out of a bike in a LBS because it hadn't been
put in properly, but since it hadn't been put in properly, only a few
threads were damaged. Still a bit embarrassing though (and, as it happens,
a Dahon - pedal had no flats for a spanner, and appeared to need to be done
up with an Allen key from the other side of the crank).)

[Alan Braggins]

In article >, Peter Clinch wrote:
>Elisa Francesca Roselli wrote:
>
>> I hope the people at the shop, which sells Cannondales and such like,
>> will understand the term helicoil.
>
>Say what the problem is, ask them to fix it. Don't worry about exactly
>*how*, especially as they can assess it first hand and transatlantic
>jargon may not be the same.

And a new crank may well be cheaper than having the old crank tapped and
an insert put in. Which pedal was it?

(Though if you have managed to get the pedals the wrong way around, you
will almost certainly have damaged both cranks, even if only one pedal has
precessed loose.)

[Bill Sornson]

Elisa Francesca Roselli wrote:

> (For I am constitutionally incapable of screwing
> straight. Read into that whatever you please.)

Thank you for a wonderful line. (Will leave others to attend to your pedal
woes.)

Bill "familiar with the phrase" S.

[Leo Lichtman]

I doubt that even a mechanic could get a left-hand thread to start into a
right hand. That's very unlikely to be it.

I see nothing wrong with substituting a similar used crank arm for the
stripped one, even if it's not a perfect match, appearance-wise.

As a temporary repair, it should be possible to use a product that's
intended for restoring stripped threads. It's a two-part epoxy system, made
by Lok-tite or Permatex, and maybe others. I wouldn't trust this for
long-term use, because I don't think it would hold up to the side loads that
a pedal gets.

How about cutting back a little on the thickness of the crank arm, and
putting on a thin nut? (Also temporary.)

[Zog The Undeniable]

Elisa Francesca Roselli wrote:

> Now what? I realize I cannot trust that pedal. By and by, I see no
> reason to trust the other pedal either. Is it that the thread where it
> screws in is shot, due to my inability to screw it on straight in the
> first place? (For I am constitutionally incapable of screwing straight.
> Read into that whatever you please.) Does this mean replacement of not
> just pedals but also pedal cranks? Or is there any endemic reason why
> one cannot have steel MTB pedals on a aluminum cranks?

The pedal thread is virtually indestructible. Unfortunately it sounds
like the crank thread is gone, and RH cranks are rarely sold singly.
The upshot is you need a new pair of cranks.