Weird Instability Problem When Putting The Power Down...

"Christopher Harrison" wrote in message
ups.com...
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.

I watched a guy leaving a bike shop get hit by a car. Though the rider was
unhurt the car owner immediately had him take the bike into the shop who
declared it fine. After the driver left I looked at the bike and the seat
tube was broken at the bottom bracket.

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.

From one Trek owner with a possible busted-up frame, that's
encouraging to hear!

On Aug 3, 11:31 am, Christopher Harrison
wrote:
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

I put my money on the headset. I had something very similar. The
bearings were pressed on the steering tube and would occasionally move
out of plane with the cups in the headset. If I checked the movement
of the handlebar, stop to stop, it would sometimes slightly bind, but
not always. When I rode, it would almost feel like someone was pulling
the bars from my hands and it would cause me to veer. The problem
erratic and only showed up at speed. Had to replace the fork, headset
and cups. JC

Christopher Harrison wrote:

snip
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


My money is on the rear stays or rear dropouts. Also, the rear axle
can be busted but still simi-functioning via the quick release (I've
busted three rear axles in my 40,000+ miles and each time the cycle
shop sales idiot said, "Oh that's normal flex", only to have the shop
mechanic disassemble the rear hub and have the axle come out in
pieces).

Have someone mount the bike, hold strong front wheel brake, and
repeatedly torque-untorque the rear wheel by pressing and releasing
hard on the crank (crank approx parallel to ground), first on the
right side and then on the left. While that is being done you closely
observe the rear stays and dropout area.

David

On Aug 3, 1:34 pm, holdmybeerandwatchthis
wrote:

I put my money on the headset. I had something very similar. The
bearings were pressed on the steering tube and would occasionally move
out of plane with the cups in the headset. If I checked the movement
of the handlebar, stop to stop, it would sometimes slightly bind, but
not always. When I rode, it would almost feel like someone was pulling
the bars from my hands and it would cause me to veer. The problem
erratic and only showed up at speed. Had to replace the fork, headset
and cups. JC

I once had a bike start to handle badly and be
scary to impossible to ride no-hands. It turned out
that I had messed with the front fender mounting
bracket and it was rubbing (not even fully binding)
on the lower headset cup.

It's sometimes easier to detect headset problems if
you take the front wheel off and just try turning
the fork, since it has much less inertia to overcome
headset irregularities.

Ben

In article
. com,
Christopher Harrison
wrote:

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

That sounds exactly as if the down-tube/head-tube joint
is compromised. I had that once. The steering is not
crisp. The bicycle wallows with excessive over-steer.

--
Michael Press

Christopher Harrison wrote:
Just recently my bike has suffered from a weird problem whereby it
will suddenly lurch to the right

Perhaps its a Habanero
http://groups.google.com/group/rec.b...27763212909680

in message . com,
Christopher Harrison ') wrote:

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

Aluminium cracks. Check in the weld areas, particularly. liquid ink will
flow into and along cracks, making them more visible.

Someone else's suggestion of checking you don't have a broken rear axle is
a good one, simply because it's a cheaper and simpler fix... but my money
is on a cracked or broken frame or fork. And I really, really wouldn't
ride that bike again until you've established where the problem is - a
broken frame rarely causes a bad crash, but a broken fork almost always
does.

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 I'm worried about the fork.

--
(Simon Brooke) http://www.jasmine.org.uk/~simon/

[ This .sig subject to change without notice ]

Many thanks again, guys, for all your suggestions... I've given my
bike a good, thorough looking-over today and what I found was that all
tubes and stays are straight and uncracked, as are the forks; and no
joints are compromised. As far as I can tell, the frame is in good
condition and in proper alignment.
What I did notice, however, was that when I rotated the headset, a
"clicky" noise emanated from the head tube. It moved freely, but you
could tell that there was something amiss... So I took the headset
apart as much as I dared/could [my mechanical skills are limited!] and
cleaned-up what I could see and got some oil in there. When I put it
back together, the headset moved more freely, but the clicky noise
turned into a consistent, and rather unpleasant, grinding sound.

You may have heard about the excessive-flooding in England, just
recently, on the news. I live in the affected region and, whilst my
bike wasn't directly involved, it's taken-on a lot more water and dirt
than usual just lately -- and I haven't been able to clean it (until
today)... As such, my best guess would be that perhaps the bearings in
the headset have become compromised (that is, water-logged!).
Would anyone concur: i.e. Given that, despite my lack of experience,
the frame looks fine to me and the horrible noise coming from the head
tube, would that be enough to cause this lurching problem?

I don't have the skills to fix it, so I'll book it back into the shop
(and tell them to give it a really thorough check, in case I did miss
something). Even if it's not the headset, I know it shouldn't be
making that noise... And, yes: I'll definitely stay off it. Even when
pushing it I can feel that it's unstable!
All I can say is that at least it's clean now: So it's got some
dignity... Poor bike

Oh, sorry... I should add: both axles are fine. I forgot to check the
bottom bracket -- bugger...