Strange 'knocks' from pedals/crank area

Hi,

I don't know much about cycles and if the following 'problems'
indicate that only my gears need adjusting (which I hope is the case -
rather than anything more serious!) then please lemme know 'bout any
online 'tutorials' that'll talk me thru it!

I have a 21-speed twist-grip all-suspension bike (Boss Reflex from
Argos) and for the last few days this has been happening:

I get a lot of 'knocks' and 'thumps' which appear to be all coming
from the pedal area but they don't happen all of the time. On occasion
its as though something has given the bike a sharp rap on the pedal
shaft which I can feel thru my foot.

Sometimes it feels as though the pedal has 'jumped' forward a fraction
or two.

Other times (only a few though) there's a 'graunching' noise as though
something's trying to mesh (or perhaps unmesh!).

Something that appears to be independent to the above is a regular
knocking noise which is 'sound only' (can't feel it thru my foot).

The above is not an exhaustive description but I'm not at all
confident about being able to describe 'strange noises' - I hope what
I've written means something to someone who will then be able to help!

Regards,

--

John Latter

Model of an Internal Evolutionary Mechanism (based on an extension to homeostasis) linking Stationary-Phase Mutations to the Baldwin Effect.
http://members.aol.com/jorolat/TEM.html

'Where Darwin meets Lamarck?' Discussion Egroup
http://groups.yahoo.com/group/evomech

John Latter writes:

Hi,

I don't know much about cycles and if the following 'problems'
indicate that only my gears need adjusting (which I hope is the case -
rather than anything more serious!) then please lemme know 'bout any
online 'tutorials' that'll talk me thru it!

I have a 21-speed twist-grip all-suspension bike (Boss Reflex from
Argos) and for the last few days this has been happening:

I get a lot of 'knocks' and 'thumps' which appear to be all coming
from the pedal area but they don't happen all of the time. On occasion
its as though something has given the bike a sharp rap on the pedal
shaft which I can feel thru my foot.

The diagnosis of these depends on their frequency. If you get one
'thump' per crank revolution that's either the pedals or (more
probably, because what you're describing is quite a big bump) the
bottom bracket. If once per wheel revolution, then it's a wheel
bearing. If once per chain revolution, it's a stuck link.

Sometimes it feels as though the pedal has 'jumped' forward a fraction
or two.

That sounds like a loose crank. Turn the bike upside down, take one
crank in each hand, and with all your strength push down on both. Then
rotate the cranks through 180 degrees and try again. If you get a
click your cranks need tightening. There are a number of different
crank attachment mechanisms but many have a simple bolt coaxial with
the bottom bracket shaft which goes into the end of the bottom bracket
shaft. There may be a little cover set into the crank which covers
this bolt. If you have this sort, the bolt can simply be tightened
with a socket wrench while holding the crank.

Other times (only a few though) there's a 'graunching' noise as though
something's trying to mesh (or perhaps unmesh!).

That sounded more like a bearing, which was my first guess. Turn the
bike upside down, hold a crank firmly with one hand to stop it moving,
and with the other hand turn each pedal through it's full revolution
(*without* the crank moving). If you feel a click, you've found the
problem. Most good quality pedals can be stripped and serviced, but
those on an Argos bike may not be worth servicing. Remember that the
left hand pedal has a left hand thread!

If you can't feel a click from either pedal, take one pedal in each
hand and rotate the cranks slowly, putting all your weight on. If you
feel a click, that's a dodgy bottom bracket bearing. Most bottom
bracket bearings these days are cartridge type and cheap ones are not
servicable. In any case removing and replacing bottom bracket bearings
of most types is a bit of an art, so unless you're used to tinkering
with things I'd take it to your LBS.

--
(Simon Brooke) http://www.jasmine.org.uk/~simon/
,/| _.--''^``-...___.._.,;
/, \'. _-' ,--,,,--'''
{ \ `_-'' ' /
`;;' ; ; ;
._..--'' ._,,, _..' .;.'
(,_....----''' (,..--''

On Thu, 05 Feb 2004 19:35:04 GMT, Simon Brooke
wrote:

John Latter writes:

Hi,

I don't know much about cycles and if the following 'problems'
indicate that only my gears need adjusting (which I hope is the case -
rather than anything more serious!) then please lemme know 'bout any
online 'tutorials' that'll talk me thru it!

I have a 21-speed twist-grip all-suspension bike (Boss Reflex from
Argos) and for the last few days this has been happening:

I get a lot of 'knocks' and 'thumps' which appear to be all coming
from the pedal area but they don't happen all of the time. On occasion
its as though something has given the bike a sharp rap on the pedal
shaft which I can feel thru my foot.

The diagnosis of these depends on their frequency. If you get one
'thump' per crank revolution that's either the pedals or (more
probably, because what you're describing is quite a big bump) the
bottom bracket. If once per wheel revolution, then it's a wheel
bearing. If once per chain revolution, it's a stuck link.

Sometimes it feels as though the pedal has 'jumped' forward a fraction
or two.

That sounds like a loose crank. Turn the bike upside down, take one
crank in each hand, and with all your strength push down on both. Then
rotate the cranks through 180 degrees and try again. If you get a
click your cranks need tightening. There are a number of different
crank attachment mechanisms but many have a simple bolt coaxial with
the bottom bracket shaft which goes into the end of the bottom bracket
shaft. There may be a little cover set into the crank which covers
this bolt. If you have this sort, the bolt can simply be tightened
with a socket wrench while holding the crank.

Other times (only a few though) there's a 'graunching' noise as though
something's trying to mesh (or perhaps unmesh!).

That sounded more like a bearing, which was my first guess. Turn the
bike upside down, hold a crank firmly with one hand to stop it moving,
and with the other hand turn each pedal through it's full revolution
(*without* the crank moving). If you feel a click, you've found the
problem. Most good quality pedals can be stripped and serviced, but
those on an Argos bike may not be worth servicing. Remember that the
left hand pedal has a left hand thread!

If you can't feel a click from either pedal, take one pedal in each
hand and rotate the cranks slowly, putting all your weight on. If you
feel a click, that's a dodgy bottom bracket bearing. Most bottom
bracket bearings these days are cartridge type and cheap ones are not
servicable. In any case removing and replacing bottom bracket bearings
of most types is a bit of an art, so unless you're used to tinkering
with things I'd take it to your LBS.

Thanks Simon! I've had a quick read thru your advice, but as I've only
got a few minutes, I'll have to come back & digest it later - I
haven't time to reply just now (nor look at my bike), but apart from
the apparently 'independent' regular noise, everything else is
non-rythmmic.

Just hope there's nothing seriously wrong, that my attempts to
'fix-it' don't make things worse, and that it doesn't cost me too
much!

I appreciate your help - thankyou

--

John Latter

Model of an Internal Evolutionary Mechanism (based on an extension to homeostasis) linking Stationary-Phase Mutations to the Baldwin Effect.
http://members.aol.com/jorolat/TEM.html

'Where Darwin meets Lamarck?' Discussion Egroup
http://groups.yahoo.com/group/evomech

On Thu, 05 Feb 2004 20:43:37 +0000, John Latter
wrote:

On Thu, 05 Feb 2004 19:35:04 GMT, Simon Brooke
wrote:

John Latter writes:

Hi,

I don't know much about cycles and if the following 'problems'
indicate that only my gears need adjusting (which I hope is the case -
rather than anything more serious!) then please lemme know 'bout any
online 'tutorials' that'll talk me thru it!

I have a 21-speed twist-grip all-suspension bike (Boss Reflex from
Argos) and for the last few days this has been happening:

I get a lot of 'knocks' and 'thumps' which appear to be all coming
from the pedal area but they don't happen all of the time. On occasion
its as though something has given the bike a sharp rap on the pedal
shaft which I can feel thru my foot.

The diagnosis of these depends on their frequency. If you get one
'thump' per crank revolution that's either the pedals or (more
probably, because what you're describing is quite a big bump) the
bottom bracket. If once per wheel revolution, then it's a wheel
bearing. If once per chain revolution, it's a stuck link.

Sometimes it feels as though the pedal has 'jumped' forward a fraction
or two.

That sounds like a loose crank. Turn the bike upside down, take one
crank in each hand, and with all your strength push down on both. Then
rotate the cranks through 180 degrees and try again. If you get a
click your cranks need tightening. There are a number of different
crank attachment mechanisms but many have a simple bolt coaxial with
the bottom bracket shaft which goes into the end of the bottom bracket
shaft. There may be a little cover set into the crank which covers
this bolt. If you have this sort, the bolt can simply be tightened
with a socket wrench while holding the crank.

Other times (only a few though) there's a 'graunching' noise as though
something's trying to mesh (or perhaps unmesh!).

That sounded more like a bearing, which was my first guess. Turn the
bike upside down, hold a crank firmly with one hand to stop it moving,
and with the other hand turn each pedal through it's full revolution
(*without* the crank moving). If you feel a click, you've found the
problem. Most good quality pedals can be stripped and serviced, but
those on an Argos bike may not be worth servicing. Remember that the
left hand pedal has a left hand thread!

If you can't feel a click from either pedal, take one pedal in each
hand and rotate the cranks slowly, putting all your weight on. If you
feel a click, that's a dodgy bottom bracket bearing. Most bottom
bracket bearings these days are cartridge type and cheap ones are not
servicable. In any case removing and replacing bottom bracket bearings
of most types is a bit of an art, so unless you're used to tinkering
with things I'd take it to your LBS.

After a quick look at my bike I've found that the left-hand pedal
casing is cracked - could this be the cause of some of the problems?

I can't get the pedal off 'til I borrow some spanners off of my
brother so I thought I would ask in the meantime!

Regards,

--

John Latter

Model of an Internal Evolutionary Mechanism (based on an extension to homeostasis) linking Stationary-Phase Mutations to the Baldwin Effect.
http://members.aol.com/jorolat/TEM.html

'Where Darwin meets Lamarck?' Discussion Egroup
http://groups.yahoo.com/group/evomech

John Latter writes:

On Thu, 05 Feb 2004 20:43:37 +0000, John Latter
wrote:

On Thu, 05 Feb 2004 19:35:04 GMT, Simon Brooke
wrote:

John Latter writes:

I don't know much about cycles and if the following 'problems'
indicate that only my gears need adjusting (which I hope is the case -
rather than anything more serious!) then please lemme know 'bout any
online 'tutorials' that'll talk me thru it!

I get a lot of 'knocks' and 'thumps' which appear to be all coming
from the pedal area but they don't happen all of the time. On occasion
its as though something has given the bike a sharp rap on the pedal
shaft which I can feel thru my foot.

The diagnosis of these depends on their frequency. If you get one
'thump' per crank revolution that's either the pedals or (more
probably, because what you're describing is quite a big bump) the
bottom bracket. If once per wheel revolution, then it's a wheel
bearing. If once per chain revolution, it's a stuck link.

After a quick look at my bike I've found that the left-hand pedal
casing is cracked - could this be the cause of some of the problems?

Depends how far the crack goes and whether the casing is integral with
the race, but on a bike of this quality it sounds probable.

I can't get the pedal off 'til I borrow some spanners off of my
brother so I thought I would ask in the meantime!

Remember that the left pedal has a left-hand thread.

--
(Simon Brooke) http://www.jasmine.org.uk/~simon/
; ... of course nothing said here will be taken notice of by
; the W3C. The official place to be ignored is on www-style or
; www-html. -- George Lund

On Fri, 06 Feb 2004 16:35:06 GMT, Simon Brooke
wrote:

John Latter writes:

On Thu, 05 Feb 2004 20:43:37 +0000, John Latter
wrote:

On Thu, 05 Feb 2004 19:35:04 GMT, Simon Brooke
wrote:

John Latter writes:

I don't know much about cycles and if the following 'problems'
indicate that only my gears need adjusting (which I hope is the case -
rather than anything more serious!) then please lemme know 'bout any
online 'tutorials' that'll talk me thru it!

I get a lot of 'knocks' and 'thumps' which appear to be all coming
from the pedal area but they don't happen all of the time. On occasion
its as though something has given the bike a sharp rap on the pedal
shaft which I can feel thru my foot.

The diagnosis of these depends on their frequency. If you get one
'thump' per crank revolution that's either the pedals or (more
probably, because what you're describing is quite a big bump) the
bottom bracket. If once per wheel revolution, then it's a wheel
bearing. If once per chain revolution, it's a stuck link.

After a quick look at my bike I've found that the left-hand pedal
casing is cracked - could this be the cause of some of the problems?

Depends how far the crack goes and whether the casing is integral with
the race, but on a bike of this quality it sounds probable.


Thanks for replying Simon, the 'stopper' that covers the nut on the
pedal had disappeared & when I tried to fit one from another bike the
moulded casing of the pedal began to split in two!

I'm too much a newbie (although advanced in years!) to understand
exactly "casing is integral with the race" means but I'm gonna borrow
some tools off of my brother tomorrow (the multi-purpose spanner which
came with the bike is no good), change the pedal, & see what happens -
and I will (try to) remember about the thread!

John

I can't get the pedal off 'til I borrow some spanners off of my
brother so I thought I would ask in the meantime!

Remember that the left pedal has a left-hand thread.

--

John Latter

Model of an Internal Evolutionary Mechanism (based on an extension to homeostasis) linking Stationary-Phase Mutations to the Baldwin Effect.
http://members.aol.com/jorolat/TEM.html

'Where Darwin meets Lamarck?' Discussion Egroup
http://groups.yahoo.com/group/evomech