Hardrock23

Iv been messing around with the fit on my bike recently and iv slightly raised my seat post, and really lowered my stem. The saddle to bar height is almost even, with the saddle being ever so slightly still lower than the bars. Anyway, after lowering the stem the first time, the ride went as usual. The second time i lowered the stem more, raised the seat about 2mm or so, and went for another ride - everything was going well until i would stand up, the bike started to wobble back and forth/become very unsteady - even worse when going fast, downhill.

its the stem being too low right? There is still exactly 1 inch of stem showing, so i thought it would be fine at this height, and its the stock stem if that matters.

Edit- To change "wiggle" to "wobble", as that seems more accurate, really.

RonH

What do you mean by "there is still 1 inch of stem showing"? Got pics?

Maelochs

Maybe he has a quill stem? All I can figure is he has shifted his center of gravity far enough forward to change the handling, but I don't see where just changing bar height would introduce any kind of serious shimmy. Interesting issue.

Slash5

Do you have a threadless headset and stem? If so, did you adjust the preload after moving the stem?
If you have a threaded headset then not sure what the issue is - maybe just need to get used to the new position.

dprayvd

Deflate (of course) your front tire, then rotate/index the tire a quarter-turn/whatever-it-takes on the rim. Rebalance the gyro after a cg change.

Knee to the top-tube technique is also handy.

canklecat

Adjusting the seat and handlebar heights affect our balance on the bike, not so much the bike itself. I made the same adjustments to my bike a couple of weeks ago, although being a comfort hybrid the fully lowered handlebars are still above the seat. With my weight now more forward it felt a wee bit twitchier on gravel and loose dirt. But I'll get accustomed to it as muscle memory kicks in and conditioning improves so I'm better able to support more weight on my legs over rough stuff.

FWIW, the bike felt twitchier climbing out of the saddle on uphills when the handlebars were fully elevated. But the bike felt twitchy overall to me for the first couple of weeks after I got it. I was accustomed to drop bars and the upright, swept back bars and wider stance took some getting used to. Easier on my back than drops though. Everything felt nicely centered and balanced for leisurely riding on level ground with no headwind, but it became a bit of a chore in less leisurely conditions. I rode it that way for a couple of months before lowering the bar, which makes it easier on uphills and into headwinds.

CrippledKonaBoy

You just answered your own question. You said the bike was squirrelly when you first got it, but you got used to it. Now, you've made fit changes -- you have to get used to it all over again.

I am going though much the same thing, after a MAJOR change to my bike.

Hardrock23

The bike was completely fine until i just made this final change on the last ride. I never felt the bike wobble so much that i thought id lose control, or wobble at all for that matter.

The steering remained the same, no twitchy-ness or anything. I mean, the ENTIRE bike wobbled side to side very fast. I shouldve been more clear lol Sorry!

I have a stock quill stem. Ill add a picture.

Hardrock23

Its possible its the balance, since it happened while standing...ill try a few more times as is, then i suppose raise it again if it doesnt change. It only happened when standing going downhill, not pedaling. Not when i stood and pedaled on the flats. I guess i can just not stand while going downhill, since it IS unnecessary and i dont do it often lol Point being - it shouldnt wobble at all and i thought id ask why it would, i guess.

Maelochs

I think what you have is what is called "speed wobble" or something like that ... when for some unknown reason all the different vibrations of your bicycle resonate and the whole things starts vibrating. Check the headset, would be my first thought ... if you moved your stem, you might have loosened it a little.See if your wheels wobble much. Otherwise ... talk to someone smarter than I.

randomgear

Is your seatpost raised above the minimum insertion mark? If it is, lower it. - Sorry, I thought pics were of the OP's bike.

Other than that, it might just be the change in weight distribution that's making it noticeable, now. Occasionally, there is a need to stand or unweight your seat while riding downhill when going over rough pavement for instance.

I've had my commuter bike start shimmying on me when riding downhill with a very heavy load, had to slow down to stop it from happening; it was disconcerting... But since I don't normally ride fast downhill with a very heavy load on that bike, it's a condition that's easy to avoid.

Hardrock23

Ignore the half hung frame bag lol

Hardrock23

my stem is almost all the way in, with an inch to spare. I just posted pics. It did stop wobbling when i applied the brakes, i remember now that youve said similar. It was just, well, scary...how violently it was wobbling lol But yes, the paved trail i ride does need repaving, so i do need to stand sometimes during those rough spots - unfortunately some rougher areas are on the hills, ofcourse.

Hardrock23

Yes, it happened when at the highest speed. Going down smaller hills with less speed, I didnt much experience the wobbling. I did promptly hop off and check each wheel, made sure the stem was tight and straight, and even checked the brakes and cranks just in case. Everything seems right. Ill just have another few go's of it, at this point...see if its just me or if its the bike, and go from there again

Sy Reene

This was my first guess as well... fwiw.

ltxi

Sometimes all the planets align and harmonics just be to biting you in the ass.

Fastfingaz

I don't see how adjusting stem and seat post will make the bike wiggle or wobble,,,, so check your wheels

canklecat

Nice bike. Worth getting accustomed to the adjustments until you feel stable and confident.

Besides lowering the handlebar height, it's also placing the bar slightly more forward due to the angle of the headset. So your upper body is lower and farther forward. More weight forward now. That'll affect your balance. Any slight input from your hands will feel exaggerated. If you find yourself with a death grip on the bars, practice relaxing and loosening up a bit on the grips. Trust the bike - it'll find its center, so just let your hands follow along. It's like dancing - even when you're leading, you're not shoving your partner around but guiding, indicating (unless you're really Irene Adler in disguise!).

When you climb out of the saddle you're putting even more weight forward, so your balance and grip on the bars are even more sensitive.

I've had to recite the same mantra to myself recently after lowering my bars and riding on some rough gravel trails. It'll come with practice, but after 30 years away until three months ago, for now I'm having to consciously tell my body to behave. I've practiced on a rural route with rough pavement and gravel 2-3 times a week the past couple of weeks to get accustomed to this stuff and it's becoming muscle memory. Feels much more secure than back in August-Sept when everything felt twitchy because my body wasn't balanced.

BTW, you mentioned feeling that instability while cruising downhill, not pedaling. This is possibly the trickiest posture. Your legs aren't cycling to offset slight imbalances. Be sure to keep that classic 3-and-9-o'clock position on the pedals, but you'll need to choose which foot goes forward - for me the left usually goes forward, mostly a habit ingrained from boxing. A natural southpaw might feel more secure with the right foot forward. And eye dominance is also a subtle factor (I'm left eye dominant).

Hardrock23

This makes sense, thank you. Im still learning so much. I started riding again back in july, but I was a teen last i rode and didnt know anything back then. I started with the basics of fit, thought i had everything right, and moved over to just learning how to work on the bike. I didnt know until recently anything about weight distribution - even still, i didnt even think of that when this happened, and im still trying to figure it all out lol

Gweedo1

A few thoughts:

Raising the seat moves your butt further back. Did you readjust your saddle to get knee over pedal spindle after you raised the seat? If not, the front end could be even lighter after the second adjustment, and feel less planted.

Perhaps the bar, (and or seat which you could tell by feel/pedaling action) is not aligned, and your steering is off line. The bike, through the contact patch of the tires, (yours are large) will try and go straight, especially at higher speeds, and may be producing the head shake.

The head set bearings are too loose, or too tight.

Good luck.

Gweedo1

Sorry, I don't follow that at all. Could you please elaborate how the tire's position on the rim will have any effect, or be related to riding position?

If the wheel is out of balance due to the tire's location, and I don't know how one could tell that in the first place, one could not put it *in* balance by changing riding position, so how could changing riding position put it *out* of balance?

I don't see any connection between the two.

Thanks.

Looigi

I haven't read all the posts so it might have been asked already, but when you lowered your stem did you properly adjust the headset? Too tight or too loose can lead to wobbles.

Maelochs

it's a fishing reference. The gentleman is using the specific fishing style called "trolling."

DorkDisk

I'm thinking its a balance/positioning issue and not a speed wobble. OP might be having problems redistributing weight transitioning from saddle to out of saddle.

Possibly too much weight on arms and too much forward weight? The arms should always be loose and limber, with a constant bent elbow. Transfer all weight down to the pedals. On downhills, just hover your butt over the seat, a bit back to unweigh the front.

dprayvd

It's like this: the rim is pinned--therefore not balanced; the tube is valved--therefore not balanced; Tires, no matter their level of lightness, have areas that may have more mass than other areas. Combine these three factors and one can have a assembled wheel (aka a gyroscope) with a heavy spot, sometimes very much so. Spin at a certain frequency gets the wobble, sometimes very much so. Toss-in a position refit and here's Wobble (in this case). The tire is the most easily adjustable factor (I suppose one can add ballast also.) I've produced the wobble just by adding a nightlight to my bars (aka a center of gravity alteration.)

Next time your sled is upside-down, make the front so the valve is at 4 or 8, let go, and wait. Where the wheel finally settles the 6 position is the heavyspot.

ihth & ymmv

And poster #23 , I've been here a bit too long to troll, however, thank you for your tactful consideration regarding my gentlemanliness.