Weird Instability Problem When Putting The Power Down...

Hi all,

Just recently my bike has suffered from a weird problem whereby it
will suddenly lurch to the right if you're leaning on that side, when
rocking to-and-fro for leverage (e.g. climbing or sprinting). It means
you have to react by quickly shifting to the left to avoid toppling
over (into the road, as we drive on the left here).

Whenever it happens, it seems to stem from the front wheel -- possibly
the tyre's sidewall. I've taken a look at both wheels and they seem to
be true (as far as I can tell) and there is no damage to either tyre
(700x23) that I can see... I've been told that it could just be that
I'm putting too much power down (i.e. the drive train is on the right
and the increased torque causes the instability). However, it
sometimes happens at low speeds (even when I'm not out of the saddle);
also, whilst it's possible that my power may have increased just
recently, I don't think it would have that significantly!
My only other line of enquiry is checking the stem and handlebars, to
make sure they're even. However, I'm pretty sure they a I had my
bike serviced and checked-over just a few weeks ago after being hit by
a car. Things couldn't have got out of alignment so soon.

Any advice would be most gratefully received! At the moment, it's kind
of a problem: I'm not confident in riding at normal speed (and
especially not high speed or up a hard climb)...

Many thanks
Christopher Harrison

Check for a broken chain stay.

"Christopher Harrison" wrote in message
oups.com...
Hi all,

Just recently my bike has suffered from a weird problem whereby it
will suddenly lurch to the right if you're leaning on that side, when
rocking to-and-fro for leverage (e.g. climbing or sprinting). It means
you have to react by quickly shifting to the left to avoid toppling
over (into the road, as we drive on the left here).

Whenever it happens, it seems to stem from the front wheel -- possibly
the tyre's sidewall. I've taken a look at both wheels and they seem to
be true (as far as I can tell) and there is no damage to either tyre
(700x23) that I can see... I've been told that it could just be that
I'm putting too much power down (i.e. the drive train is on the right
and the increased torque causes the instability). However, it
sometimes happens at low speeds (even when I'm not out of the saddle);
also, whilst it's possible that my power may have increased just
recently, I don't think it would have that significantly!
My only other line of enquiry is checking the stem and handlebars, to
make sure they're even. However, I'm pretty sure they a I had my
bike serviced and checked-over just a few weeks ago after being hit by
a car. Things couldn't have got out of alignment so soon.

Any advice would be most gratefully received! At the moment, it's kind
of a problem: I'm not confident in riding at normal speed (and
especially not high speed or up a hard climb)...

Many thanks
Christopher Harrison

Christopher Harrison wrote:

Just recently my bike has suffered from a weird problem whereby it
will suddenly lurch to the right if you're leaning on that side, when
rocking to-and-fro for leverage (e.g. climbing or sprinting). It means
you have to react by quickly shifting to the left to avoid toppling
over (into the road, as we drive on the left here).


[snip]

However, I'm pretty sure they a I had my
bike serviced and checked-over just a few weeks ago after being hit by
a car. Things couldn't have got out of alignment so soon.

Any advice would be most gratefully received! At the moment, it's kind
of a problem: I'm not confident in riding at normal speed (and
especially not high speed or up a hard climb)...


OK - so your bike was hit by a car and now, only now?, is suffering from
a strange problem. lol my guess is they are related.


Sounds like a case of frame or component damage to me. But a *lot* more
details would be required to narrow that down. But I'd carefully inspect
the chainstays and seatstays, and the bottom bracket and see if it might
be cracked. You could also flex things carefully and see if there are
differences between the right and left side while doing so.


*excessive movement of the bike to one side while under power isn't normal*

Regards

Bill

William R. Mattil wrote:
Christopher Harrison wrote:
Just recently my bike has suffered from a weird problem whereby it
will suddenly lurch to the right if you're leaning on that side,

Sounds like a case of frame or component damage to me.

Yeah. Could be that the wheels are out of alignment (front fork bent
to the left).


--
E. Dronkert

Thanks guys

When I had it serviced, after my little accident, they gave it the all-
clear and deemed it road-worthy -- and I trust them on experience...
However, I shall check these things out.

In article . com,
Christopher Harrison wrote:
Thanks guys

When I had it serviced, after my little accident, they gave it the all-
clear and deemed it road-worthy -- and I trust them on experience...
However, I shall check these things out.


This is just a shot in the dark, but if everything else checks
out, see if the headset is turning completely freely. Even a
minor bind can cause very strange handling effects.

_ Booker C. Bense

On Fri, 03 Aug 2007 14:54:45 -0000, Christopher Harrison
wrote:

Thanks guys

When I had it serviced, after my little accident, they gave it the all-
clear and deemed it road-worthy -- and I trust them on experience...
However, I shall check these things out.

A good idea.

A couple quick and dirty aligment tests: a) loop a string from one
rear dropout, around the headtube to the opposite dropout, then
measure the clearance on either side of the seattube; b) when riding
no-hands does the bike have a tendency to veer to one side?

In article
.com
,
Christopher Harrison
wrote:

Hi all,

Just recently my bike has suffered from a weird problem whereby it
will suddenly lurch to the right if you're leaning on that side, when
rocking to-and-fro for leverage (e.g. climbing or sprinting). It means
you have to react by quickly shifting to the left to avoid toppling
over (into the road, as we drive on the left here).

Whenever it happens, it seems to stem from the front wheel -- possibly
the tyre's sidewall. I've taken a look at both wheels and they seem to
be true (as far as I can tell) and there is no damage to either tyre
(700x23) that I can see... I've been told that it could just be that
I'm putting too much power down (i.e. the drive train is on the right
and the increased torque causes the instability). However, it
sometimes happens at low speeds (even when I'm not out of the saddle);
also, whilst it's possible that my power may have increased just
recently, I don't think it would have that significantly!
My only other line of enquiry is checking the stem and handlebars, to
make sure they're even. However, I'm pretty sure they a I had my
bike serviced and checked-over just a few weeks ago after being hit by
a car. Things couldn't have got out of alignment so soon.

Any advice would be most gratefully received! At the moment, it's kind
of a problem: I'm not confident in riding at normal speed (and
especially not high speed or up a hard climb)...

Get off that bicycle immediately!
Now examine all joints and tubes minutely.
It is most likely the frame is broken,
probably a joint at the head-tube.
What is the frame material?

As for some bicycle shop checking it, they cannot be
trusted since they have not reproduced the problem you
experience.

--
Michael Press

when riding no-hands does the bike have a tendency to veer to one
side?

I wouldn't say so, no. However, it's hard to tell: the camber of the
road will make it pull to the left naturally, but I would compensate
for that by shifting my weight to the right without thinking about
it... When I'm down on my aerobars -- which, granted, is still
steerable; but close to no-hands -- there's no appreciable veering to
either side.

It is most likely the frame is broken,
probably a joint at the head-tube.
What is the frame material?

Ouch... I hope not That sounds expensive... It's aluminium -- so I
guess that would bend, rather than shatter (a la carbon fibre).
I did have a quick look just now and everything seems fine: all the
tubes look straight (didn't note the joints). However, I'll check it
out thoroughly on Sunday, along with all other suggestions...
Thanks

If it's helpful: When it happens, it feels like (if you use your
imagination) the sidewall of the front tyre, on the right side,
suddenly collapses. Almost like going into an endo before the lurching
to the right... That's why my first investigation was the front tyre.
I'll give my innertubes a good looking at, too.

Thanks again, guys -- it's really appreciated

On Aug 3, 2:06 pm, Michael Press wrote:
In article
.com
,
Christopher Harrison





wrote:
Hi all,

Just recently my bike has suffered from a weird problem whereby it
will suddenly lurch to the right if you're leaning on that side, when
rocking to-and-fro for leverage (e.g. climbing or sprinting). It means
you have to react by quickly shifting to the left to avoid toppling
over (into the road, as we drive on the left here).

Whenever it happens, it seems to stem from the front wheel -- possibly
the tyre's sidewall. I've taken a look at both wheels and they seem to
be true (as far as I can tell) and there is no damage to either tyre
(700x23) that I can see... I've been told that it could just be that
I'm putting too much power down (i.e. the drive train is on the right
and the increased torque causes the instability). However, it
sometimes happens at low speeds (even when I'm not out of the saddle);
also, whilst it's possible that my power may have increased just
recently, I don't think it would have that significantly!
My only other line of enquiry is checking the stem and handlebars, to
make sure they're even. However, I'm pretty sure they a I had my
bike serviced and checked-over just a few weeks ago after being hit by
a car. Things couldn't have got out of alignment so soon.

Any advice would be most gratefully received! At the moment, it's kind
of a problem: I'm not confident in riding at normal speed (and
especially not high speed or up a hard climb)...

Get off that bicycle immediately!
Now examine all joints and tubes minutely.
It is most likely the frame is broken,
probably a joint at the head-tube.
What is the frame material?

As for some bicycle shop checking it, they cannot be
trusted since they have not reproduced the problem you
experience.

--
Michael Press- Hide quoted text -

- Show quoted text -

Mike
My thought was that the damage was there when the shop examined it,
but not visible to the eye. Additional riding may well have caused it
to fail in a more noticeable way, but I agree that getting off it
immediately is great advice.
The only frame we had break was a Trek and they, through our local
shop, handled it in a very satisfactory way with an upgraded frame for
a minimal charge.
Bill C