MightyLegnano

Hello fellas!

I have a quite old steel mountain bike that runs very smoothly except the violent shakiness/wobblyness it it has when I don't have my hands on the handlebars (the actual wobblyness seems to have the stem as a center). The strange thing is that this behavior started suddenly the previous week.

Do you have any idea what could be the cause of that?

Zef

could possibly be improper headset or hub adjustment.

OR

You have a gremlin living within the tubes of your frame.


On a more serious note:
My left little toe hurts...it just started happenning the other day...can you tell me why?

-j

catonec 

seriously dude? check your head set for proper fit, lubrication, pitting, popped out bearings...... maybe your rim is slightly out of true.

you have 3.5 bikes listed in your heading, maintain them.

MightyLegnano

You obviously didn't understand the problem. When I say I notice shakiness/wobblyness when I cycle without hands, I mean the stem goes left and right rapidly, like shaking. I don't think it has something to do with maintenance.

Bytheway, Greenfieldja, you 're not helping by being sarcastic. If you don't know what I'm talking about, don't reply. I prefer few and serious answers, than more and ridiculous.

Zef

Oh, right....that clears it up for everyone and makes things much more simpler to diagnose.

Take roll of duct tape and cut a 2x2 square piece from the roll. Carefully place the square on the very end of the LEFT side of your handlebar so that the sticky side adheres to the bar. Then take a mallet and gently tap the square of duct tape 5.5 times.

Let us know if that fixes the problem.

-j

catonec 

I repeat check your hardware. something changed, either your wheel or the pivot point or maybe brakes/pads. sorry to come off like an ass, just trying to help troubleshoot. always check the physical components first.

Zef

Stop being a boob and provide more details such as the history and condition of your bike, and the conditions you ride such as road surface, along with what you are doing when the problem happens such as how fast you are going where on the road you are riding as if it is a crowned road or not...etc...so that folks with experience can give you a serious answer. Presently you have given minimal information that is mostly useless to diagnose your problem.

You totally rejected another posters serious response that it could be maintenance related. IF it is not maintenance related then it may possibly have something to do with astrological alignment...but who knows from the lack of deatail you provided.

The sarcasm was an attempt to get you to consider that your request for diagnosis in your post is a bit idiotic, due to the abscence of info, without actually stating that....but since you could not figure that out your continued responses devoid of information hi-lights that for everyoner very clearly.

If you find your audience does not know what you are talking about then perhaps you should not discount their experience but instead think about how you can increase their understanding of your problem.

-j

MightyLegnano

Greenfieldja, since you're asking for more details I will provide anything I can (although I seriously doubt your ability to understand a problem by reading a text and propose something useful).

Here it goes anyway for other people who might want more info on the case. It's an old steel mountain bike from a greek manufacturer (it was an expensive one back then) which I'm certain you don't know anything about but you can learn some useful info in their website: www.idealbikes.net
The problem started to happen 8 days ago when I was riding on slick asphalt with no hands. I didn't do anything, I just started cycling without hands and I've noticed the problem right away. The stem is this kind https://thumbs4.ebaystatic.com/d/l225...uLlbXkTotQ.jpg and it seems quite steardy (no wobble whatsoever when the bicycle is not moving). I was going 30-35 km/hour when it happened the first time, but the speed doesn't seem to play a role in it, because the same shakiness happens even when I go slower.

The bike is well maintained and never had problems with it although it has done thousands of kilometres loaded or not, gravel or asphalt. The color of the frame is blue and I wear a black Gyro helmet.

I hope that will explain everything, if you want more info let me know.

catonec, the brake pads are quite worn out, do you think they might affect it somehow?

Zef

First: Have someone who knows about headset and hub adjustment check for proper bearing adjustment.

Second: A bike with "quite worn out" brake pads is not a bike that is "well maintained", so who knows what else might be out of sorts with your "old steel mountain bike".

Your best bet would be to visit a competent bicycle shop to have them assess the condition of your bike and the components that may be involved with the issue you are experiencing.

-j

MightyLegnano

Who says that you must have only fresh out of the box brake pads on your bike? They are worn out but they still have life in them.

I knew that the easiest route would be to visit my bicycle mechanic, that's common sense, but I wanted to try by myself first.

Zef

Yeah, I am not sure we have the same working definition of "common sense". You have repeatedly missed the mark on this. You seemingly lack the experience to address your issue and at the same time have thrown common sense and logic out the window and continue to reject any notion of sound judgement with regard to taking care of your problem....

...have you tried the duct tape and mallet solution yet? You may be surprised how much it helps. It is about as logical a solution as your common sense approach has been.

Cheers,
-j

MightyLegnano

What was the sound judgement? Your suggestion to try my luck in a bicycle shop? Your whole contribution in this thread was insults and puberty-inspired wisecracks. I will say it again, if you don't know the answer dont bother replying.

MightyLegnano

I found this bike magazine article (Bicycle Quarterly, Volume 6, Number 3) from this forum. The editors couldn't identify what causes the problem. Maintenance doesn't seem to play a role thought.


Curing Shimmy on a Bike

by Jan Heine and Mark Vande Kamp

Some bikes shimmy, others don’t, even if they are made from the same tubes. Some believe that poor frame alignment is the cause for shimmy, but we have ridden modern custom frames from very reputable builders that shimmied, even though they appeared to be aligned very well. Yet many older frames with unknown histories do not shimmy, despite being obviously misaligned.

Looking at the variables involved, Jan noticed that he never had ridden a bike with a Stronglight needle-bearing headset that shimmied, yet similar bikes (from the same maker, with the same tubing and geometry) with ball bearing headsets often shimmied.

Stronglight headsets are different from all others in that the bearings align automatically, and thus compensate for imperfections in the facing of the head tube. On a standard headset, the balls on one side tend to run looser than those on the other, because the top and bottom edges of the head tube never are perfectly parallel. Furthermore, the needle bearings of the Stronglight headset may add a little resistance to the headset, perhaps enough to dampen shimmy, but not enough to change the steering characteristics of the bike.

To see whether a different headset could make a difference in shimmy behavior, we replaced the Chris King headset on Mark’s Ti Cycles, a bike with a very strong shimmy under certain conditions, with a Stronglight needle-bearing headset. Mark rode the bike to the workshop with a load in the handlebar bag, and it was easy to provoke shimmy.

After we replaced the headset, Mark tried to induce shimmy as he had before, but the bike no longer shimmied. After numerous attempts, he finally got the bike to shimmy briefly, but instead of continuing until Mark put his knee on the top tube, the shimmy now attenuated on its own within a few oscillations. We then loaded the handlebar bag with about 4 kg (8.8 lbs.). Still, the bike’s shimmy was gone in most speed ranges. Only when coasting downhill no hands at 40 km/h (25 mph), a violent shimmy occurred that was beyond the capacity of the headset’s dampening. Placing one hand on the handlebars immediately stopped the shimmy. Mark rarely rides no-hands at speeds this high, so the shimmy problem on this bike has been mostly eliminated with a simple headset change.

In conclusion, we still do not know what causes shimmy on a bike. From Mark’s and my experience, it is unrelated to top tube diameter. A handlebar bag does increase the likelihood of shimmy on Mark’s Ti Cycles, but many other bikes with handlebar bags do not shimmy. We found that we could eliminate most of the shimmy on one of the worst bikes we experienced, by replacing the Chris King headset with a needle-bearing Stronglight model. If your bike shimmies, it is worth a try.

catonec 

all right guys give it a rest.

The brake pad issue I was thinking of was if one was loose and vibrating. the amount of material on it shouldnt matter.

if your rim was out of true you would probably feel it even when your hands were on the bars, maybe even more.

since it only happens when your riding no handed its most likely in your bars or stem. Is your stem new?? is it the proper size for your handle bars? yes they come in different diameters. is it snug?

Next I would re-seat the wedge at the bottom of your stem attached to the long bolt that runs the length of the stem. check for tightness. It doesnt need to be gorilla tight. its a soft metal and can break.

there is also a large nut that holds your forks tight at the bottom of you stem, check for proper tightness.

If you pick up your front wheel and move your handlebars back and forth do you feel any resistance or clicking? if not your headset is probably ok. While It is pretty easy to visually check out the upper bearings, the lower bearings require a tiny bit more effort. make sure there is lubrication. look for squared off or split bearings. If they are seated in a ring verify they all move freely.

Make sure your wheel is on correctly and not loose or rubbing a fork. spin your wheel and hold the handlebars. again you are feeling/listening for clicking or resistance of any sort.

The bottom line is, your weight on the handlebars is preventing the vibration.

your problem is probably something minor, something obvious. when you find it you'll smack your forehead and say duh. Im not sure what exactly what it is but I can tell you for sure that the color of your frame or your choice of helmet is not the issue

gluck

MightyLegnano

Thank you alot catonec , I will check all those things out.

Something that just came to me is that the day the wobble started I had taken out the heavy handlebar extentions. But I can't understand why I didn't have the same issue, when the handlebars were extentions free, few years back.

catonec 

a new headset cost money. sometimes as much as $100.

replacing it will probably fix your issue but not because the headset is bad. It will work because everything I mentioned above will done in the process of replacing it.

I have given you multiple ideas to check. it is all free. do what you want w/ my suggestions.

I am done w/ this thread.

MightyLegnano

After doing some "reverse-engineering" I found the cause of the problem.
I 'm writing it here for future reference.

Five or so years back I replaced the original handlebars with a new shorter one. BUT, I added metal extentions (quite heavy) to add extra space for my hands in the case of bike touring. So, although the frame lost some of the original alignment, the heavy extentions added stability, thus I was wobbly-free and didn't notice the difference.

The previous week, when I removed the extentions, the bike was out of the original alignment once more, without the stability they provided this time. So I had a wobbly stem.

Zef

Well well, a plethora of information that was missing from the original post that could have been considered in an assessment of your problem. The reality though is that changing your bars to shorter ones or attaching/removing extensions should have minimal impact on the function of your steering. You should still check out your hubs, wheels, and headset, bar and stem clamp bolts, along with frame alignment to see if any of those are in need of attention and could be causing your problem. Just putting a shorter bar on should not induce violent wobbling/shimmy as you stated you experience.

-j

MightyLegnano

No, I put back the extentions and the bike is shimmy free!