Toyo Atlantis Shimmy ???

[Tony McG]

From the beginning: The original owner purchased it as a frameset in '99 because at the time, the future of the Atlantis was questionable. He built the bike and never rode it because he found a Waterford that he liked better. I bought it barely used a few years ago and have put a few thousand miles (mostly gravel) on it. The headset would never stay tight no matter how hard I dared wrench on the locknut. I took it to a LBS and they removed the headset and machined the frame so that the headset would fit better. I rode it for a year, and I still had problems with it loosening. I then took it to another LBS and they installed a spacer (seems like the headset might have bottomed out on the threads???). I now have a tight headset, but I also have a shimmy when I let go of the handlebars. I used to be able to ride this bike without hands at any speed, but now it wobbles, even at 10 mph. I don't have any load on the bike except a small seatbag for tubes/tools, and the tires are the same Soma Cazadero from last year.

Any suggestions on what might be causing the shimmy or how to fix it? Shall I replace it with a NeedleBlasteur from the Riv site and see what happens?

[Sky Coulter]

Tony,

Don't know how helpful this might be but I was experiencing shimmy on my 60cm saluki, I tried a number of things to fix it, including a needlebearing headset (which helped i think). But the biggest change was when i swapped out the cockpit from a 90mm stem to a 100mm stem. Shifting a bit of my weight (240lbs) forward over the front wheel reduced the hands on shimmy more than anything else.  With a load in the front basket and hands off, there is still a bit of wagging from the handlebars, but more like the wagging of a dog getting petted, than oone being taken outside for a walk.

Sky in New west 

On Tuesday, August 23, 2016 at 9:46:05 AM UTC-7, Trenker wrote:

Last summer I was on a short bike trip thinking to myself, during that time on the bike when you have lots of time to think, that I have never been bothered by shimmy on any bike that I could remember. The same morning I kept hearing a knocking sound while pedaling or gliding at low speed, which went away when I put both hands lightly on the handlebar. I gradually figured out it was the fender knocking against the tire, and I realized that I had always experienced shimmy, but never realized it or been bothered much by it. This is on a 66 cm Toyo Atlantis with rear panniers and a front basket. The same morning I was having the prolonged impression of how much I liked this bike for touring.

During that trip I had enough time to experiment and ponder the shimmy, and I realized that it only happened at low speed, and that at higher speeds, eg. descending on asphalt or gravel, the bike was rock solid. Which is a nice concession.

I think shimmy can be finely tuned in or out of a bike. Going to a slightly narrower tire can improve things, as can pumping up the front tire to the same adequate pressure as the back; it isn’t written in stone that the front tire has to be at a lower pressure.

Even the road surface can affect or initiate shimmy: it looks flat but there are subtle undulations caused by car tires; they are a lot more obvious on gravel roads, before or after intersections.

If you are tweaking your setup to reduce shimmy, you can test it at home by standing beside the bike and rapping the side of the handlebar with the heel of your hand: you will be able to see if the vibrations focus on the front end ( shimmy ) or condense around the back end of the bike ( ideal, which I now have with a small basket on front and saddlebag tied to a small home-made rear rack.) Tomorrow morning I head out on another short trip and I’ll have plenty of time to see how I like this setup.

I suspect that tall riders on big bikes probably always experience a certain amount of shimmy, as well as a certain amount of frame flex, but we are used to it and don’t know any different. I wonder what size your Atlantis is?

[dougP]

Tony:

I've had a 58 cm Atlantis since '03.  With only a light load as you describe it never shimmied. 

My first experience with shimmy was the first time I had it loaded for a tour, and all of the weight was on the rear.  Others suggested getting some weight forward, so after that I started experimenting with loading.  Eventually I came to the conclusion that some front bias was preferable. 

While the above doesn't seem applicable to your situation,  I suggest moving your rear bag load to the front.  At one point in my experiments, I was able to induce shimmy with only a small rear saddlebag with tools, tubes, etc.  A specific set of conditions was req'd as well as me sitting bolt upright on the bike.  Simply moving that bag (<3 lbs?) to the handlebars solved the problem.  Simple experiment to try.

The needle bearing headset may be beneficial but I don't recall anyone claiming it to be "the cure" for all shimmies.  Shimmy seems to be an elusive problem with lots of possible sources, so tough to ID a single source in a specific case. 

dougP 

[Steve Palincsar]

So it's not the bike, it's how the load was distributed.

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[Deacon Patrick]

To second this, my Hunq shimmies with too much up front (making it unridable on pavement, let alone single track), but handles more total weight amazingly well with all but a wee bit in the rear and the rest in the front. Others love their Hunqapillars loaded in the front, with just a wee bit in the back, so rider differences seem to play a part as well. Play with the load, how secure it is, riding technique (which necessarily changes with more weight), load balance front/rear and side to side, how far up and/or out the load is (especially on the front. Tighter and lower and centered/balanced side to side is more solid).

With abandon,

Patrick

[Bill Lindsay]

Unfortunately, nobody knows what causes shimmy.  What I mean by that, is that there is not a human being on earth that look at your bike and say "your bike shimmies and here's why".  If we took 9 bikes that don't shimmy and 1 that does and put them in a lineup, there is no human that can look them over and pick out the shimmying bike.  If we took a non-shimmying bike to the workshop there is no mechanic that can do work on it to cause it to shimmy.  

What we do know is that shimmy is a resonant oscillation, and everybody who knows anything about resonsance knows that if it is resonating, then everything that is important is just right in that oscillating mechanical system.  To stop it, you change something that is important.  How do you know what's important?  Take a guess and start changing things.  If it helped, it was important.  If it doesn't, either it wasn't important or you didn't change it enough.  

A needlebearing headset has proven to be effective because it adds damping to the oscillating mechanical system.  It's still resonating, but the amplitude gets scrubbed off and the self-amplifying part of the resonance fades away.  (for electronics geeks, damping reduces the Q of the system).  The damping from a needlebearing headset is from friction.  A needlebearing headset does not turn as freely.  

Weight distribution on the bike can be quite important, and is the only thing you can easily make major changes to.  Some people guess that tire width and tire pressure can effect shimmy.  Some speculate that frame stiffness and steering geometry influence whether or not a bike will shimmy, but you are stuck with those things.  

Bill Lindsay

El Cerrito, CA 

On Tuesday, August 23, 2016 at 9:02:58 AM UTC-7, Tony McG wrote:

[René Sterental]

All fair and savvy points. It all depends on how far you're willing to go to address it. 

I had the same issues and ordered a low trail fork that addressed it. Ordering a custom fork is not expensive, especially if you don't mind having it painted a different color than your frame. 

Other simpler solutions presented can he tried first. 

I cannot guarantee it will fix it for you, but it did for me. 

René 

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[Tony McG]

This is a 61 cm Atlantis. The tire pressure looks like a good place to start experimenting. I have been running the Cazadero at about 30-35 psi on the front because of our chunky gravel roads. The seatbag and contents probably weigh less than a pound, but I may try to see how a handlebar bag affects the shimmy. Thanks for your replies!

[Steve Palincsar]

There are many different things that can cause a vibration that some
will call "shimmy" (and that in some cases, others will call "speed
wobble"). Some of them are various kinds of rider behavior, that can't
properly be blamed on the bike at all. Cases in point: shivering.
Holding on to the bars too tight. I even recall one case (on a mailing
list) of a guy who would smack the top tube to initiate a vibration and
then complain if the bike shimmied.

Well said, Bill.

[Steve Palincsar]

Certainly cheap enough to try.  Right there on a par with messing around with the bags and the load.  When you start changing things like bars and stems to vary rider weight distribution it starts to get more expensive.  (I mention those because in 1972, my P15 Paramount exhibited a truly terrifying speed wobble.  Sometime between then and 1976, a time when I messed around a lot with bars and stems, trying to get a better fit on a bike that was an inch and a half too small for me, I changed something -- never did find out what -- that made the speed wobble stop happening.  And during that time period, the only other components I changed were front and rear derailleurs, and nobody's ever suggested they play a role in speed wobble.

[Bill Lindsay]

Steve pointed out:  "some 

will call "shimmy" (and that in some cases, others will call "speed 
wobble"

That is an important distinction.  I've never experienced the "hands on the bars" version and I've never experienced the "ultra-high speed wobble" variant where you have to be going 40mph to have it happen.  I've only experienced the no hands riding variant. 

[Steve Palincsar]

Be happy.  The "hands on the bars at 20+" version is about the most terrifying thing you can experience.  Car crash - not even close, because you're too busy to feel any emotion.  Bike crash - over in an instant, much too fast to feel any emotion.  Being shot at - not even close, it's mostly a "WFT???" of puzzlement (at least, it was for me, in RVN).  But with speed wobble you feel it - your emotions wash over you - you can see your life flashing before your eyes.

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[Tony McG]

This bike has descended hills on SE Minnesota and NE Iowa gravel roads at over 40 mph with no problems, but I haven't had a chance to try those hills since the spacer was put in last Winter. It is the low speed without hands wobble that Bill describes that is bothering me. Since the needle bearing headset appears to be more of a band aide than a cure, I am going to hold off throwing parts at the bike until I try changing tire pressures or even swap out the Cazaderos for  a set of Schwalbe Dureme that I have laying around. Thanks again everyone!

[John Bokman]

I had frustrations with shimmy at low to moderate speed (10-15 MPH) while sitting upright cruising along a flat road on my Sam. Couldn't figure it out. Had the LBS check it out: wheels, frame alignment, etc. They found nothing. Tightened the headset to offer more friction and that didn't help. What did help was sliding my saddle just a fraction forward toward the bottom bracket. Just a smidge. I had the saddle all the way back on the rails (a Berthoud saddle, don't know how long the rails are offhand). Just  a nudge forward did the trick.

[dougP]

Load placement seems to be a major factor in whether a bike shimmies or not, and your experience with moving your position slightly is interesting.  I noticed I could induce shimmy at a specific speed coasting downhill while sitting bolt upright, and it would go away as soon as I leaned slightly forward.  When you think about it, the human head weighs roughly as much as a bicycle, and it's on a long lever arm.  Granted, our body is an automatic damping mechanism, but WE just may be the cause of our own shimmies. 

dougP

[Stephen Kemp]

Steve said "Bike crash - over in an instant, much too fast to feel any emotion."

I crashed last week. There was a slight rustling from the back of the bike, like a leaf or something brushing the wheel. I looked down to check it out, then when I looked up again I was heading for the kerb! I had enough time to think "idiot, you know this road has a curve in it, you ride it every day, never do that again!" I remember thinking the ground looked a long way down. Then bang, crack, expletive! I got up and checked myself over - no damage to me or the bike. And the rustling noise? Never found out - it was gone when I remounted...

[Tony McG]

John's post just reminded me that I swapped the Sele Anatomica for a Brooks Cambium. There is a big difference in rail lengths on these saddles and that would certainly change how the frame is loaded.

[Alex Wirth- Owner, Yellow Haus Bicycles]

If it were me, I would dissassemble the headset and inspect not only the cups/headtube but also the fork crown/crown race.  Dollars to donuts, based on your description, one or both of those surfaces isn't mating correctly.

[iamkeith]

I'm with Alex - that, based on your description, the problem is still likely in the headset.  Except I'd go a step further.   When you said "they added a spacer because the headset had bottomed out on the threads," did you mean they added a spacer between the locknut and the threaded top race cap?   Because, if so, that won't solve anything!   If you're running out of threads, then the threaded top cap is the part that isn't getting tightened down far enough - not the lock nut.   I  would expect the mechanic to know this but I suppose that if they're strictly from the threadless headset generation, it could be an oversight on their part.

Likely what happened is that, when they faced the headtube earlier, they removed just enough material to change the length to where it mattered.  Being a Rivendell, the steerer tube was probably sized to put as many threads as possible ABOVE the headtube/headset, to allow for extra spacers and increased handlebar height.   (the threads that fall internal to the headtube are basically "wasted".)  

What you may need is a new headset with a taller stack height at the bottom race/cup portion.   Worst case scenario, you may need an extended crown race - though it sounds like you're "barely" out of threads, so you'll likely be able to find something that works.  Might be an excuse to get a King, which are pretty tall.  Or, you could kill two birds with one stone, and look for a tall needle bearing option, instead.

just a theory, but looking forward to hearing what you figure out in the end

[Clayton]

I have a Toyo Atlantis and had shimmy with a rear biased load. Once I put a little more weight on the front, it went away. I used Tubus low riders with a small Nitto mini rack on the front and had horrible shimmy when loaded. When I went to a Nitto big front rack, it went away.  Currently I am running the Nitto M-12 mini rack, with my Stuinniker bag, and with King Kage " Anything" cages on my fork, which works great for my bikepacking needs (but lousy for groceries)....There is enough load on the front to prevent shimmy, and light enough steering to feel like a bicycle and not a semi truck. 

Clayton (Bend)

[masmojo]

Not Atlantis related, but maybe relevant none the less. I had an XO-1 until several months ago. When it was new I rode it around no hands all the time fast forward to a few years ago, I had not ridden it for some time & I am enjoying it. Turned to go down a small hill, sat back on the seat with my hands off the bars as I'd done thousands of times before and the front end started wobbling violently! I was able to quickly grab the handlebars, but it rattled me a little.
The questions go through your head, what was that? Everything with the bike was fine, the only thing that had changed in the equation was ME! When I bought the bike & rode it a lot I weighed 175lbs. When I rode it again!? 240!!
So adding weight up front might solve the problem, but I think maybe your weight may be effecting the handling? The XO-1 has very slender seat stays, they probably were not designed for someone my weight, I surmise the frame was flexing more under the increased load! :-(

[Ryan Fleming]

yes it does and it has quite small diameter tubing....Ishiwata .022 and takes a 27mm diameter seatpost...still have mine and still enjoy it and alas I am quite a bit heavier than I was when I bought it in September of 1993... but I'd prefer not to quantify how much heavier :)

[Tony McG]

-

I am a bicycle rider, not mechanic, so I may have misunderstood when I was told about the spacer being installed. My mechanical skills are limited to basic maintenance and adjustments and I usually let the pros do the complicated stuff. I am going to try and attach a photo of the headset and maybe one of you can tell me which spacer was installed. The mechanic that installed it had the day off when I picked up the bike so he wasn't able to point it out to me. If I get all of my chores done today, I may get a chance to ride the Atlantis tomorrow and play with tire pressures and saddle adjustments. I have a Velo-Orange seatpost that is setback further than the Nitto that I may swap out and see if it helps.

[iamkeith]

Looks like there may be a spacer between the top cup and headtube? (Looks like a small gap/shadow line to me) If so, that's pretty unusual and the likely culprit. Easy to get things crooked as you add more pieces and interfaces. Show us a pic of the bottom, too. After my last post, i started wondering if maybe they tried to shim the crown race upward?

[iamkeith]

Before i forget, another way to solve the "running out of threads" issue is to cut more threads. Since you only need a few, it's not a big deal to do this with the thread chasing tool, if the mechanic is willing. The lock nut and most of the threaded top cap will still engage the stronger, factory- formed threads. This would allow you to keep the same headset.

On the other hand, if you spent years with that inexpensive headset repeatedly working loose on you as you mention, its likely worn and it's time for a new one anywar

[iamkeith]

Tony,

I think I may retract some of what I've said above.  I always stress out about being an arm-chair mechanic and giving bad advice so, once I've said something, I keep going over it in my head and thinking about how I might have been wrong.  In this case, I think the added shim is NOT where I thought it might be from looking your picture.

I just took a look at my daughter's bike which has the same headset.   Here's a shot from a slightly different angle than yours, which shows the race fully inserted into the headtube.   Viewed from the angle of your photo, it does give the appearance of there being a "gap," which I took to be a spacer.

So, if they had to add a spacer in order to be able to  tighten the locknut, what I'm now thinking is simply that the upper lip of the locknut was contacting the top of the steerer tube.   This was probably happening all along but, after facing the headtube and removing material, it just got worse.   So one of those regular spacers needed to be thicker.  With some locknut designs (this one included), there is a pretty small margin of error in terms of necessary spacer height:  too many spacers and not enough threads will be engaged;  too few spacers, and the locknut will bottom out before tightening against the upper cap.     Easiest way to figure out how many spacers you need is to tighten the locknut without spacers, measure the gap, and then add spacers that total a couple of mm MORE than that.

Still....  If that headset was repeatedly coming loose on you for years, then it was likely damaged, and you really should replace it before trying anything else.   If it was ovalized or distorted, that could make your steering want to "index" to a certain point, which would make it very hard to ride no-hands.

Similarly:  This is counter-intuitive but I've heard it mentioned enough times that I think there must be something to it:  If a headset is tightened slightly TOO MUCH, it will actually make it harder to ride no-hands.  You should try loosening it just a bit and experimenting.

[Lungimsam]

Don't fret over it.

80$ Tange RollerDrive + 40$ LBS install+10minutes wait while they do it = you are all set. 

[masmojo]

Having a bunch of spacers is probably contributing to the headset coming loose issue, but it should not be causing a shimmy. I do agree that sometimes over tighting fan be worse than too loose; too tight & thebearing races can get dimpled, once this happens, you will basically have indexed steering and riding no hands will be, difficult if not impossible.

[Tony McG]

Wednesday night I was riding with the local club road ride and I sat up and let go of the bars at about 19 mph, and the bars wobbled like crazy. Today I was riding gravel at about 15 mph, and there wasn't a hint of shimmy when I sat up and let go of the bars. I ride lower tire pressure on gravel than pavement, so I think I will watch it closer if the new parts don't cure the problem. I ordered an IRD RollerDrive headset from Soma and it will replace the current headset as soon as my Fargo is back on the road.

[Evan Baird]

In 100% of shimmy incidents it's down to Huldufólk distribution.