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Discussion Starter · #1 · (Edited)
We were out yesterday in grotty conditions - cold wet and windy. Descending at about 35mph on a poor road surface my mate in front of me on his carbon Giant developed a bad wobble. He rides Spinergy Xaero lites with those yellow plastic PBO spokes. He had a wet weather jkt rolled up in a bag, fastened on top of h/bars which he suspects may have set up the wobble.

Has anyone experienced a speed wobble on one of these Giants or can anyone come up with an explanation? Your comments would be welcome.

As it was a wet day, it was impossible to say whether this incident caused a damp patch on my mate's bottoms, but it was a scary incident - for me watching as well.

The Flying Bean
 

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Certainly could be one of any factors that caused the wobble. My guess is a combination of poor conditions and the possibility of a loose part or two, maybe the headset or a wheel... I can say that the TCR's are a bit more "twitchy" than other bikes I've rode due to their compact geometry, and this only gets exasperated with adverse conditions. I've found that wobbles often happen when the rider is trying too hard to control the bike-hands clenched on the bars, stiff elbows... this compared to a relaxed position. Luckily he pulled out of it...
 

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Not the first report I have seen...

the flying bean said:
We were out yesterday in grotty conditions - cold wet and windy. Descending at about 35mph on a poor road surface my mate in front of me on his carbon Giant developed a bad wobble. He rides Spinergy Xaero lites with those yellow plastic PBO spokes. He had a wet weather jkt rolled up in a bag, fastened on top of h/bars which he suspects may have set up the wobble.

Has anyone experienced a speed wobble on one of these Giants or can anyone come up with an explanation? Your comments would be welcome.

As it was a wet day, it was impossible to say whether this incident caused a damp patch on my mate's bottoms, but it was a scary incident - for me watching as well.

The Flying Bean
Your friend needs to report this to Giant. This is not the first or second report I have heard about Giant TCR speed wobble. Theories range as to what causes it. It could be the geometry of bike coupled with a lack of appropriate lateral stiffness. The front fork could be playing a role in this.

I would be very disappointed to have spent that kind of money and have a bike that does this. Caveat emptor.

-PV
 

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My TCR wobbled like a....

i dunno something that wobbles lots :)
Cross winds and poor road conditions are the usual culprits. It's more than likely due to a rider (in this case me) clutching too tightly... The TCR doesn't help matters due to what ever it is geometrically or whatever that makes it more prone to wobbles but ultimitely it's a rider problem. I've since learned some tricks (from this board) that have got the problem under control.. I haven't had a wobble in quite a long time now.
All speed wobbles are initiated by the rider... some bikes and some conditions exentuate the problem.
 

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Strange........

the flying bean said:
We were out yesterday in grotty conditions - cold wet and windy. Descending at about 35mph on a poor road surface my mate in front of me on his carbon Giant developed a bad wobble. He rides Spinergy Xaero lites with those yellow plastic PBO spokes. He had a wet weather jkt rolled up in a bag, fastened on top of h/bars which he suspects may have set up the wobble.

Has anyone experienced a speed wobble on one of these Giants or can anyone come up with an explanation? Your comments would be welcome.

As it was a wet day, it was impossible to say whether this incident caused a damp patch on my mate's bottoms, but it was a scary incident - for me watching as well.

The Flying Bean
Being the owner of a alloy TCR (but the fork, seatpost, seatframe and stem is carbon)
and having descended in somewhat normal conditions at over 40 mph and not experienced
anything like he describes I'd say it could be a number of things.

To test this, have him descend on a dry road on a good condition day without the wet
weather jacket strapped to his bars to see if this condition persists or if it doesn not
occur. My guess is a jack strapped to the bars could act like a pretty good sail in
windy weather.....possibly.
 

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Sounds like rider error.

Are those wheels flexy? Is he heavy? Gripping the bars too tight?

There is no real reason to be gripping the bars much at all. It's a total waste of energy and really hurts your handling.

Maybe the headset is loose? I have the same bike, my headset wasn't quite tight enough when I picked it up and it seemed like the front end shook a lot when I hit a bump at speed.

Ben
 

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Wobble/shimmy

Frith said:
i dunno something that wobbles lots :)
Cross winds and poor road conditions are the usual culprits. It's more than likely due to a rider (in this case me) clutching too tightly... The TCR doesn't help matters due to what ever it is geometrically or whatever that makes it more prone to wobbles but ultimitely it's a rider problem. I've since learned some tricks (from this board) that have got the problem under control.. I haven't had a wobble in quite a long time now.
All speed wobbles are initiated by the rider... some bikes and some conditions exentuate the problem.
There has been a great deal written on the subject of bike (and motorcycle) high speed wobbling. With a little time dedicated to research, you could learn a thing or two. I must be blunt: your post above is all over the place. First, wobble is caused by rough roads and cross winds. Next, you say that "all speed wobbles are initiated by the rider". Do you really know about this subject?

A very knowledgeable bicycle expert/guru (I will not name him) has written extensively about the causes of high speed shimmy/wobble. That is the research that you need to do.

Wobble/ shimmy relates to the frame and its natural resonace frequency. The Giant TCR model is not he only bicycle known to have demonstrated this very frightening wobble, but it is certainly gaining a reputation for it. There are numerous reports of the this model exhibiting high speed wobble. Not a good thing for a racing bike.

If I had spent big bucks on a racing bike and, upon informing the retailer who sold it to me that it had a very dangerous shimmy/wobble, the last thing he needs to tell me is that it is my fault. That's just silly.

It is not a rider problem; it is a frame problem (a characteristic, really). There are ways that a rider can deal with it, but it is certainly not the fault of the rider.
 

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plus_vite said:
There has been a great deal written on the subject of bike (and motorcycle) high speed wobbling. With a little time dedicated to research, you could learn a thing or two. I must be blunt: your post above is all over the place. First, wobble is caused by rough roads and cross winds. Next, you say that "all speed wobbles are initiated by the rider". Do you really know about this subject?

A very knowledgeable bicycle expert/guru (I will not name him) has written extensively about the causes of high speed shimmy/wobble. That is the research that you need to do.

Wobble/ shimmy relates to the frame and its natural resonace frequency. The Giant TCR model is not he only bicycle known to have demonstrated this very frightening wobble, but it is certainly gaining a reputation for it. There are numerous reports of the this model exhibiting high speed wobble. Not a good thing for a racing bike.

If I had spent big bucks on a racing bike and, upon informing the retailer who sold it to me that it had a very dangerous shimmy/wobble, the last thing he needs to tell me is that it is my fault. That's just silly.

It is not a rider problem; it is a frame problem (a characteristic, really). There are ways that a rider can deal with it, but it is certainly not the fault of the rider.
However, that same expert/guru has written that the resonant frequency of bike shimmy is close to that of human shivering, and in cold conditions, the shivering can initiate or exacerbate the wobble. Not exactly the rider's fault, but the rider may be contributing in this way.
 

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plus_vite said:
Wobble/ shimmy relates to the frame and its natural resonace frequency. The Giant TCR model is not he only bicycle known to have demonstrated this very frightening wobble, but it is certainly gaining a reputation for it. There are numerous reports of the this model exhibiting high speed wobble. Not a good thing for a racing bike.

If I had spent big bucks on a racing bike and, upon informing the retailer who sold it to me that it had a very dangerous shimmy/wobble, the last thing he needs to tell me is that it is my fault. That's just silly.

It is not a rider problem; it is a frame problem (a characteristic, really). There are ways that a rider can deal with it, but it is certainly not the fault of the rider.
You seem really intent on wanting to place the blame on the frame and none on the rider, when in reality there really is some blame on the rider.

If the giant frames were really that bad we'd have seen a tragic accident in a major race that would have been all over the news. But we don't, because rider technique is a big part of it. The fit of the bike, the riders weight, the riders technique, etc.. all effect it.

Unless the bike is incredibly horrible the rider is partly to blame. This frame is not that bad. No one in the motorcycle world will blame it all on the bike either, the rider can make big effects to how it happens, and a motorcycle weighs a whole lot more than a bicycle and is a whole lot less responsive to rider input.

Caveat: I have not had this happen on a bicycle despite plenty of high speed descending, I have experienced mild cases on a motorcycle and recovered from it pretty easily.

Ben
 

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plus_vite said:
First, wobble is caused by rough roads and cross winds. Next, you say that "all speed wobbles are initiated by the rider". Do you really know about this subject?
Having experienced it first hand I will say yes, I know more than I'd like to about this. Let me put it simply for you as you seem to be having trouble with this.

Condition A:
1. Road conditions and wind cause rider to be extra cautious.
2. Cautious/inexpereinced rider grips bars tightly and tries to keep wheel straight often over compensating for problem.
3. Bike with certain properties (very likely properties found in this particular bike) exentuate rider induced problem.
RESULT: The above conditions are combined and wobble occurs.

Condition B:
1. Road conditions and wind cause rider to be extra cautious.
2. Expereinced rider recognizes the conditions under which wobble may occur and take steps necessary to prevent it (I can go into this further if you require)
4. Bike with certain properties which under some circumstances contribute to wobble still present.
RESULT: rider able to maintain stable ride.

I hope this clarifies things for you.
 

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Rider Error is 99.9% the Problem

Saying it's the bike frame is stupid. You should look first at rider error, and second look at things like loose headset, or wheel issues. :rolleyes:

The Giant TCR Composite was used by ONCE in the 2003 TDF. I'm sure LOTS of those guys went over 40mph. .And if all had wobbles, the mechanics would have been going ape trying to find out what's the deal!

I saw a guy on a TCR in the 2002 Giro, and he was hitting 60 on a twisty road. .These are VERY WELL proven race bikes ;)
 

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KATZRKOL said:
Saying it's the bike frame is stupid. You should look first at rider error, and second look at things like loose headset, or wheel issues. :rolleyes:
I agree- and 35 mph isn't even that fast- certainly not fast enough to cause resonance issues. A bunch of riding friends and I were discussing this phenomenon regarding a hill with very wavy pavement- and how it really was rider error on our part, since the waves and ridges in the pavement would battle the will of the rider, so we would overcompensate and hence the entire bike felt like jelly. Again, it was just that one hill. I think most people are "too cool" to admit they had the bars in a death grip, and they themselves literally shook their bike into a noodle. Lateral stiffness? I don't think so. I've had wheels way out of true that wouldn't even cause a wobble to the degree I myself could create.

BTW- high speed wobble on a motorcycle? Only time it ever happened to me was at very high speed on spoked wheels.
 

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I have over 10,000 miles on my giant TCR composite and have yet to experience anything but great handling from it. I regularly descend at 45-55mph and get no speed wobbles whatsover. As previous posters have said it's all to do with natural resonance frequency and harmonics - but what you must look at is the bike and the rider as a whole unit as they both interact with each other plus the external environmental influences i.e. wind direction/strength, road surface etc.
How do you position yourself on a fast descent? Tuck down legs grip the top tube or one leg pressed against it, relaxed grip on the bars, don't fight the bike, go with flow. All comes from experience and is just second nature.
I do know that if I am going 50mph and you stand up, hands on the drops and move the bike about below you then you soon set up an unstable bike. Similarly if you have the bars in a death grip and are too rigid and fight the bike then you are going to have problem descending at speed.
 

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The only wobble I get on my TCR is when I have a nasty cross wind other than that I have no wobble at 40+ mph decents.
 

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What Wobble?

I've ridden over 4000 miles on my TCR composite and so far havent experienced any wobble. The fastest I've ridden it is 45mph and travel at 40mph quite regularly downhill. Wobbling can be attributed to many variables like, wheel alignment and trueness, tyre/road condition etc. I have to agree with other writers that it's extremely unlikely the frame or forks are to blame since they are 'stiff' and not susceptible to resonant vibrations low enough to cause 'wobble' when riding. It could well have been the road surface which was causing his tyres to track one way and then the other as it happened to me on my motorbike once on a bridge that was being resurfaced.
 

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When you start to wobble, get your weight back over the rear wheel. You can induce shimmy at anything over about 25mph by leaning out over your front wheel. As you go faster the shimmy begins with less weight on the front wheel. Just slide your butt of the back of the saddle and watch the shakes subside!

Yes, it is rider-influenced, but shimmy is largely dependant on frame/fork/wheel/road surface harmonics, which may be damped out by pressing a leg against the top tube and adjusting your fore-aft weight distribution. Oh, and tell your friend to stow his jumper somewhere else! Less weight/inertia on the front of the bike will be be very helpful!

I used to ride a Kawasaki Z-1 900 that felt like it was hinged in the middle in curves - ain't no feeling like the beginnings of a tank-slapper at 95mph in a tight, rough corner. I learned pretty quickly how to drag a knee on the inside of the corner!
 

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Thoughts..........

I looked at my riding logs for the last season or so and found this:

(statistics are good for something eh?)

Rides: 150

Rides above 30+ mph: 22
Rides above 35 mph: 10
Rides above 40 mph: 2
Rides above 45 mph: 2
Rides above 50 mph: 1

There weren't any wobbles, shimmies, wipe-outs or other stuff, just smooth riding.

I don't ride super fast a lot, but when I do the bike is more than able to deal with it.
 
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