wannabe mechanic question

"cold [censored] action" <[email hidden]> wrote in message news:[email hidden]...

Quoted message said:

treat me gently, i've decided to move into the oily world of repairing my own bike so sorry if this is a basic question

i've inherited a zaskar with XTR hubs front and rear. When i peddle fast, the rear wheel feels like it's off balance and has a
strong up and down vertical shaking movement. This increases with speed.There is no shaking on the horizontal plane. This
description is all i could think of but it's along the lines of if you imagine putting a weight on a part of the rim then
spinning the wheel, you've feel the weight knocking the smooth equal wheel motion off balance.

The wheel is securely in place and tight. The skewer isn't buckled neither are the actual rims or spokes. If i take the wheel
off and turn the axle,i can't feel any play at all but i'm wondering if i can hear a slight crunchy bearing sound .

is the vertical movement down to damaged or worn bearings ? I don't want to strip it down if it's not that dept. I have also
re-seated the tyre and tube just in case but no change..

any ideas ?

thanks

oops forgot, 'cause this bike has XTR stuff, i want to keep any equipment i add to in in that quality range so, what's the best
quality bearings to use. I only really do XC so i don't need any downhill monster stuff

cold censored action said:

i've inherited a zaskar with XTR hubs front and rear. When i peddle
fast, the rear wheel feels like it's off balance and has a strong up
and down vertical shaking movement.

This increases with speed.There
is no shaking on the horizontal plane. This description is all i
could think of but it's along the lines of if you imagine putting a
weight on a part of the rim then spinning the wheel, you've feel the
weight knocking the smooth equal wheel motion off balance.

The wheel could be off balance (heavier at one part than another) but that
doesn't really matter for bicycle wheels, and you're unlikely to notice it
when riding. But maybe you do, or something else could be wrong.

Quoted message said:

The wheel is securely in place and tight. The skewer isn't buckled
neither are the actual rims or spokes.

If i take the wheel off and
turn the axle,i can't feel any play at all but i'm wondering if i can
hear a slight crunchy bearing sound .

is the vertical movement down to damaged or worn bearings ? I don't
want to strip it down if it's not that dept. I have also re-seated
the tyre and tube just in case but no change..

I can't see how the bearings could be /that/ bad... to cause the bike to
go up and down! At worst, the hubs will be stiff/rough or have some
lateral play.

I would have suspected an ill-fitting tyre or buckled wheel, too, but it
looks like you've eliminated those.

~PB

"Pete Biggs" <p@honeydewbiggs{remove_melon}.tc> wrote in message news:[email hidden]...

Quoted message said:

cold censored action said:

i've inherited a zaskar with XTR hubs front and rear. When i peddle
fast, the rear wheel feels like it's off balance and has a strong up
and down vertical shaking movement.

This increases with speed.There
is no shaking on the horizontal plane. This description is all i
could think of but it's along the lines of if you imagine putting a
weight on a part of the rim then spinning the wheel, you've feel the
weight knocking the smooth equal wheel motion off balance.

The wheel could be off balance (heavier at one part than another) but that
doesn't really matter for bicycle wheels, and you're unlikely to notice it
when riding. But maybe you do, or something else could be wrong.

alright Pete,
that is exactly how it feels - heavier in one part than another. It's most definately off balanced, How does this happen, what's
likely to have caused it and what's the cure ?

cheers

On Wed, 25 May 2005 07:00:47 GMT, "cold [censored] action" <[email hidden]>

Quoted message said:

"Pete Biggs"

Quoted message said:

Quoted message said:

The wheel could be off balance (heavier at one part than another) but that
doesn't really matter for bicycle wheels, and you're unlikely to notice it
when riding. But maybe you do, or something else could be wrong.

alright Pete,
that is exactly how it feels - heavier in one part than another. It's most definately off balanced, How does this happen, what's
likely to have caused it and what's the cure ?

<speculation>
Has it had slime (puncture self repair goo) fitted to the tubes?
Could this have pooled in one place.

<\speculation>

Tim

in message <[email hidden]>, cold [censored] action

(') said:

treat me gently, i've decided to move into the oily world of repairing
my own bike so sorry if this is a basic question

i've inherited a zaskar with XTR hubs front and rear. When i peddle
fast, the rear wheel feels like it's off balance and has a strong up
and down vertical shaking movement. This increases with speed.There is
no shaking on the horizontal plane. This
description is all i could think of but it's along the lines of if
you imagine putting a weight on a part of the rim then spinning the
wheel, you've feel the weight knocking the smooth equal wheel motion
off balance.

Sounds as if the wheel is out of round and needs retrueing. You can do
this yourself; it's not desperately hard but takes patience,
particularly the first time you do it.

<URL:http://sheldonbrown.com/wheelbuild.html#tensioning>

Quoted message said:

The wheel is securely in place and tight. The skewer isn't buckled
neither are the actual rims or spokes. If i take the wheel off and
turn the axle,i can't feel any play at all but i'm wondering if i can
hear a slight crunchy bearing sound .

A bearing problem wouldn't cause the symptoms you have. That doesn't
prove you haven't got a bearing problem, of course, but I wouldn't
worry about it on the evidence you've given.

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

:: Wisdom is better than weapons of war ::
:: Ecclesiastes 9:18 ::

Following on from cold [censored] action's message. . .

Quoted message said:

that is exactly how it feels - heavier in one part than another. It's most definately off
balanced, How does this happen, what's
likely to have caused it and what's the cure ?

Umm. Sounds like you've done the obvious.

(1) Either there is
(a) a geometrical eccentricity
or
(b) a weight imbalance

(2) Either the problem is
(a) with the hub-spokes-rim
or
(b) tyre-tube

Subject to the proviso that the wheel is not behaving differently under
load to being spun by hand:- Which of the items of (1) is easy to
determine ... if neither then either the spokes are not doing their job
or there is something wrong with the tyre/tube - I would have thought
the latter would have been a regular 'bump' rather than a cyclic wobble.

--
PETER FOX Not the same since the bookshop idea was shelved
[email hidden]
www.eminent.demon.co.uk - Lots for cyclists

cold censored action said:

treat me gently, i've decided to move into the oily world of repairing my own bike so sorry if this is a basic question

i've inherited a zaskar with XTR hubs front and rear. When i peddle fast, the rear wheel feels like it's off balance and has a
strong up and down vertical shaking movement. This increases with speed.There is no shaking on the horizontal plane. This
description is all i could think of but it's along the lines of if you imagine putting a weight on a part of the rim then
spinning the wheel, you've feel the weight knocking the smooth equal wheel motion off balance.

Check the tyre is evenly in the rim all the way round.

I've seen an inner tube that's too long folded over and squashed into
the outer. You definitely need to look at the inner tube.

If you lift the wheel off the ground, does it rotate so that the same
part is always at the bottom? If the valve isn't near the bottom,
there's some other eccentric weight.

Colin McKenzie

"Colin McKenzie" <[email hidden]> wrote in message news:[email hidden]...

Quoted message said:

cold censored action said:

treat me gently, i've decided to move into the oily world of repairing my own bike so sorry if this is a basic question

i've inherited a zaskar with XTR hubs front and rear. When i peddle fast, the rear wheel feels like it's off balance and has a
strong up and down vertical shaking movement. This increases with speed.There is no shaking on the horizontal plane. This
description is all i could think of but it's along the lines of if you imagine putting a weight on a part of the rim then
spinning the wheel, you've feel the weight knocking the smooth equal wheel motion off balance.

Quoted message said:

If you lift the wheel off the ground, does it rotate so that the same part is always at the bottom? If the valve isn't near the
bottom, there's some other eccentric weight.

Colin McKenzie

cheers for your advice all...very much appreciated. I'm having this problem without the tyre or tube on the wheel although no as
bad. If i lift the wheel,it does rotate so the same part is near the bottom which is why i automatically assumed ( wrongly) the
bearings had shot.

i'm dead interested in any more advice. Does this help with anything Colin in reference to your posting ??

Tim Hall said:

<speculation>
Has it had slime (puncture self repair goo) fitted to the tubes?
Could this have pooled in one place.

<\speculation>

Or heavy ornamental valve caps perhaps?

d.

cold censored action said:

alright Pete,
that is exactly how it feels - heavier in one part than another. It's
most definately off balanced, How does this happen, what's likely to
have caused it and what's the cure ?

A lot of rims are heavier at the join due to extra bits in there. This
point can be heavier than the valve opposite. There might be other
reasons as well (reflector?, magnet?), but in any case a wheel can be
re-balanced by adding weight(s). You'd have to experiment. Try placing
bike in a stand or turn it upside down, spin the wheel fast, and add
whatever weights you like to spokes near rim end. Also try removing the
reflector if you have one (or any other removable junk).

Note that this isn't normally necessary. Jobst Brand, author of The
Bicycle Wheel says it's never necessary.

Personally, I have noticed wheels being off balance when spinning them at
home (sometimes quite badly) but never out on the road while riding
because they then have my weight on them. Buckled wheels, faulty/damaged
tyres and ill-fitting tyres have caused the up & down sensation, but it
looks like you've checked for those things already. It'll be worth double
checking, though.

~PB

I said:

Try placing bike in a stand or turn it upside down, spin the wheel
fast, and add whatever weights you like to spokes near rim end.

On second thoughts, upside down would be better for this particular job as
it leaves the bike free to bounce, wobble and vibrate.

(Again, I don't think this matters but there's no harm in balancing the
wheel if you want to).

~PB

In article <[email hidden]>,

cold censored action said:

i'm dead interested in any more advice.

The only bit you don't seem to have checked is the hub and bearings?
Check for wear on the cones and bearing surfaces and if the balls
are/were in races replace with a full set of balls.

--
A T (Sandy) Morton
on the Bicycle Island
In the Global Village
http://www.millport.net

Sandy Morton said:

The only bit you don't seem to have checked is the hub and bearings?
Check for wear on the cones and bearing surfaces and if the balls
are/were in races replace with a full set of balls.

Bad bearings wouldn't cause *vertical* play, would they?

~PB

In article <[email hidden]>, Pete Biggs

p@honeydewbiggs{remove_melon}.tc said:

Quoted message said:

The only bit you don't seem to have checked is the hub and
bearings? Check for wear on the cones and bearing surfaces and if
the balls are/were in races replace with a full set of balls.

Quoted message said:

Bad bearings wouldn't cause *vertical* play, would they?

They shouldn't but the OP seems to have tried everything else. Badly
worn races could cause the problem but probably only under load.

--
A T (Sandy) Morton
on the Bicycle Island
In the Global Village
http://www.millport.net