Hey all,

I took my ST on a descent for the first time (new ride) at 32mph and the front end wobbled. Needless to say, I slowed down. I had some pretty good side winds at the time. Do you think it's due to the down tube/forks acting as a sail in the wind?

Were you in the drops? Did you have your weight on the pedals, not the saddle?

Regardless, that seems awfully slow to be getting a wobble. You might want to check that there's no play in your headset, and that your wheels are all the way into their drop-outs and clamped tightly by correctly adjusted skewers. This might be worth a trip to the shop to have them check out that everything with the wheels and handlebars is adjusted correctly. Even pros miss something sometimes.

Yup, I was in the drops and my weight was in the saddle. I'm guessing I should be off the saddle.. I'll tighten the headseat and try the hill again.

Yup, I was in the drops and my weight was in the saddle. I'm guessing I should be off the saddle.. I'll tighten the headseat and try the hill again.

You don't want to be off the saddle- it raises your center of gravity, just push down so your butt is about to lift off.

Tighten the headset if it's loose, not otherwise. If there's no play (none) then it doesn't need to be tightened. You don't want it to bind. If it does need to be tightened then remember to loosen the stem bolts first- (edit) and re-tighten them last.

I'd be more concerned with a loose wheel- axles all the way in the drop-outs and clamped tight- the quick release should mark your hand when you close it. If the axle is too long and extends beyond the drop-out not only will it never be tight, it will always be suicidally loose.

All this stuff has to do with your safety riding. I see you don't have a lot of posts so I don't know how experienced you are with checking these things. If you're new to cycling it might just be best to have the dealer check it for you. The dealer should be more than happy to give it a once over, and if you've put 50 to 100 miles on it it's probably time to have the cables adjusted anyway (they stretch when they're new).

I fail to see how center of gravity (vertically) has anything to do with this. I often will sit up to slow myself without braking.

My guess is that if the OP relaxed, maybe placed his knee along the top tube, the whole thing would just go away. If it were mechanical, there would be all sorts of symptoms at ALL speeds.

You don't want to be off the saddle- it raises your center of gravity, just push down so your butt is about to lift off.

Tighten the headset if it's loose, not otherwise. If there's no play (none) then it doesn't need to be tightened. You don't want it to bind. If it does need to be tightened then remember to loosen the stem bolts first- (edit) and re-tighten them last.

I'd be more concerned with a loose wheel- axles all the way in the drop-outs and clamped tight- the quick release should mark your hand when you close it. If the axle is too long and extends beyond the drop-out not only will it never be tight, it will always be suicidally loose.

All this stuff has to do with your safety riding. I see you don't have a lot of posts so I don't know how experienced you are with checking these things. If you're new to cycling it might just be best to have the dealer check it for you. The dealer should be more than happy to give it a once over, and if you've put 50 to 100 miles on it it's probably time to have the cables adjusted anyway (they stretch when they're new).

All this stuff has to do with your safety riding. I see you don't have a lot of posts so I don't know how experienced you are with checking these things. If you're new to cycling it might just be best to have the dealer check it for you. The dealer should be more than happy to give it a once over, and if you've put 50 to 100 miles on it it's probably time to have the cables adjusted anyway (they stretch when they're new).

I'm not new to road riding. I have almost 4400 miles on the road this year (slacked off for almost a month). But it was on a hardtail with slicks. :mad:

But I will take the bike in in a few days and see what the shop says.

Thanks

I tightened up the headset a little and went for another ride. I ended it with the same descent (32mph the first time) that gave me the front end wobble the other day. I stayed in the drops and in the saddle again to see if anything changed. I got to 34mph (very little wind, not sure if that mattered in this case) and I had nothing but smooth steering. I guess the headset needed a little tightening. I'm still gong to swing by the shop so they can check the bike over anyway since I've got about 90 miles on her.

Thanks for the tip, California L33.

I fail to see how center of gravity (vertically) has anything to do with this. I often will sit up to slow myself without braking.


In practical terms you may be right- trying to do a though experiment and it's just not working :idea: but I'm not going to induce shimmy in a bike and stand out of the saddle to see what happens if I really raise the center of gravity. Leaning forward and loading the BB both transfer weight to the front wheel which may be more important.

I tightened up the headset a little and went for another ride. I ended it with the same descent (32mph the first time) that gave me the front end wobble the other day. I stayed in the drops and in the saddle again to see if anything changed. I got to 34mph (very little wind, not sure if that mattered in this case) and I had nothing but smooth steering. I guess the headset needed a little tightening. I'm still gong to swing by the shop so they can check the bike over anyway since I've got about 90 miles on her.

Thanks for the tip, California L33.

Remember you won't be really sure until you get the same cross wind conditions, so take it easy. Nobody wants to go down at that kind of speed.

When you had your first wobble, were you riding the front brake for an extended period of time to control your speed? That'll load the front wheel heavily and can cause speed wobbles (or a nasty tank slapper if you've ever done one (or four) on a motorcycle).

I've seen just a hair over 100 KPH (62 MPH) on my Soloist Carbon, and I made the mistake to ride the front brake a little too long, and I had a pretty heart stopping wobble. I got off the front brake, shifted my weight back, and was able to ride it out.

I usually find that riding over a series of bumps with the front brake on, or immediately punching the brake RIGHT after the bumps can trigger instabilities.

On motorcycles, I've had tank slappers on both motocross and sport bikes. The motocross bikes usually happen so fast that you hit the ground pretty hard (and it's always the same situation, me braking into a high speed downhill corner that is FULL of ruts and braking bumps). On the sportbikes you usually gas it pretty hard to lighten up the load on the front tire and you just have to ride it out. I've been lucky there.

Chris.

Loading the BB makes your body act like a spring, and can cause the rider to literally shake the bike (if grabbing the bars in a death grip). It is better to unload the BB or pedal through it. I have almost never heard anyone describe wobble while pedaling.

In practical terms you may be right- trying to do a though experiment and it's just not working :idea: but I'm not going to induce shimmy in a bike and stand out of the saddle to see what happens if I really raise the center of gravity. Leaning forward and loading the BB both transfer weight to the front wheel which may be more important.

From what I read here, it sounds like these shimmies are not the result of bike design or materials, but rather improperly adjusted components, excessive front brake use and/or poor road conditions - am I right in my understanding?

There was a discussion about the Scattante line of Performance bicycles recently where shimmying came up a number of times. From that thread, it sounded like a design/ materials issue (I'm not sure which or if anyone actually said that but that's what I read between the lines).

So I think what I want to know is that shimmying can be managed by good riding skills, technique, experience - its not a result of poor frame design? But if frame design is an element, what should I be looking for in a frame, or, inversely, avoiding?

I have ridden for over 30 yrs on many different frames and on alot of hills. Luckily i have only encountered the dreaded front wheel wobble once, it occured last year - at 85kph! I was desccending a steep hill and was passed by a semi going quite a bit faster. I was buffeted by the wind as it passed and made the mistake of grabbing the bars with a strong grib at which point my R3 began vibrate like it was on a paint shaker. I was able to ride it out, and focused on relaxing, yup hard to do. I believe it was the combination of the blast of wind and my "death" grip on the bars which set up the vibration. Like many of you, i have read a great deal about this topic in an effort to prevent it from repeating. On relection, I have come to the conclusion that riding technique is the most important component in avoiding the wobble. Specifically, relaxed hands, weight on the pedals, and knees pressing against the top tube. I think this is especially true with light weight exotic bikes.

Hey all,
I just got a 2008 Cannondale Synapse 7 and I'm experiencing the same thing. Relatively low speed, no death grip, weight on the pedals and bam! Speed wobbles.
So if this a technique issue where should my weight be? Forward? Backward?

Wobble at these speeds is most likely the result if the front wheel being improperly tensioned, tire issue, headset issue, fork issue. First thing I would suggest is to try a different wheel. Make sure your wheel is properly installed! Second thing would (as you already checked your headset) would be a trip to a good shop and have the check the frame for alienment.
I have decended at 55mph in and out of the saddle and hard braking both ahve never givin me a wobble, Strong side wind will give you more of a shove, again no wobble.