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Discussion Starter · #1 ·
A couple of weeks ago I had a case of wobbles while opening it up on a fast decent. I consider myself very lucky that I didn't crash. Suffice to say, it unnerved me big time. From the research I have done, there doesn't seem to be any one thing that I can point to or fix and be all set - sh*t happens...

With that said however, I don't want to go there again so I have a couple of thoughts I would like to put out for peoples' comment/feedback on.

FORKS.
When I read reviews and company literature, I often see the phrase "improved stability". While I understand the concept of rake as a way of affecting a bike's handling (40mm rake is good for crits and quick handling, 45mm is good for touring), what are the other aspects of fork design that can affect overall bike stability. Or, to put it another way, what are the characteristics of a "stable" fork so I can get one?

COMPACT CRANK VS. TRADITIONAL CRANK
I often spin out of my highest gear on my compact cranks (50x11 or 12?) when descending. With respect to stability, I find having even a little pressure on cranks when pedaling contributes to stability. But when I spin out of the highest gear (35+/- mph) the opposite occurs.

While the compact crank has been great for climbing, I'm thinking the trade-off of spinning out at moderate speeds and reduced stability may not be worth it. Have others with compact cranks found spinning out to contribute to loss of stability? Have people gone back to traditional cranks as a way to improve stability?

Thanks for sharing your thoughts.
 

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info...

Check your headset and wheels bearings for proper adjustment first. Speed wobble in usually attributed to frame/fork flexure and is most often seen on larger frames that may not be as stiff as small frames.

Reducing fork rake to increase trail and slow the steering might help, but it's unlikely.

Be sure you're not pedaling wildly and moving the handlebars in the process. Grip the bars lightly and don't move you upper body when pedaling at high speed.

Cranks and pedaling have nothing to do with speed wobble. You should be able to coast with just as much stability as you can while pedaling. Before considering a switch from the compact crank, be sure to see if you have an 11T or 12T smallest cog. A 12T would be easy to spin out, but an 11T will give you about 4mph more speed, before you're spun out. A lot of people just can't spin the 120 rpm cadence it takes to achieve 43mph with a 50/11.
 

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Wobble used to be a pretty common problem, though I haven't heard many complaints about it in the last few years. C-40's suggestions are good, and like him, I'm sure the crankset has nothing to do with it (pedaling may help with stability, but it's not addressing the cause). Check the headset and other things he mentioned, and ask at a good bike shop for suggestions, but sometimes no cause is found. I had a Motobecane years ago, my first "real" bike, that occasionally would go into a violent wobble at about 35mph, and I never did find a reason (fortunately I don't go 35 very often...). Light application of the front brake may help, and an old remedy used to be to grip the top tube firmly with your thighs until things settle down.
 

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RoadLoad said:
A couple of weeks ago I had a case of wobbles while opening it up on a fast decent. I consider myself very lucky that I didn't crash. Suffice to say, it unnerved me big time. From the research I have done, there doesn't seem to be any one thing that I can point to or fix and be all set - sh*t happens...

With that said however, I don't want to go there again so I have a couple of thoughts I would like to put out for peoples' comment/feedback on.

FORKS.
When I read reviews and company literature, I often see the phrase "improved stability". While I understand the concept of rake as a way of affecting a bike's handling (40mm rake is good for crits and quick handling, 45mm is good for touring), what are the other aspects of fork design that can affect overall bike stability. Or, to put it another way, what are the characteristics of a "stable" fork so I can get one?

COMPACT CRANK VS. TRADITIONAL CRANK
I often spin out of my highest gear on my compact cranks (50x11 or 12?) when descending. With respect to stability, I find having even a little pressure on cranks when pedaling contributes to stability. But when I spin out of the highest gear (35+/- mph) the opposite occurs.

While the compact crank has been great for climbing, I'm thinking the trade-off of spinning out at moderate speeds and reduced stability may not be worth it. Have others with compact cranks found spinning out to contribute to loss of stability? Have people gone back to traditional cranks as a way to improve stability?

Thanks for sharing your thoughts.
I've ocassionally had this happen also on a couple of different wheel sets. In all cases it was desending around 40mph when extremely tired (late in long ride with lots of climbing). I'm a little suspicious that it may be me that is causing it as the last time it happened when an idiot with a big travel trailer was passing me on a winding mountain decent. I was plenty scared when the wobble started and terrified by the time I got it shut down.

Does this only happen when you are tired?
 

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I wouldn't think the crankset/spinning out would have much to do with it unless the road was extremely crappy. Like on choppy dirt roads or singletrack where it's better to stand and mash a bigger gear to smooth things out. On a recent ride, I was spinning 52x15 @ 140RPMs down a hill and felt very stable. I would check the wheel bearings. A few weeks ago my rear wheel felt squirmy, and once I adjusted the cones it went away. Just a thought.
 

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Discussion Starter · #10 ·
I have a 2005 54cm Scattante CFR. Its full carbon with Easton Temepest II wheels. I hadn't experience any wobbles before my recent "moment of terror" which occurred in the early afternoon after a lot of climbing, but I wouldn't say I was particularly tired. We had gone about 45 miles at that point.

The bike weight thought had occurred to me. I weigh 185lbs and have wondered if that's too much weight for a 17lbs bike?
 

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No...

RoadLoad said:
I have a 2005 54cm Scattante CFR. Its full carbon with Easton Temepest II wheels. I hadn't experience any wobbles before my recent "moment of terror" which occurred in the early afternoon after a lot of climbing, but I wouldn't say I was particularly tired. We had gone about 45 miles at that point.

The bike weight thought had occurred to me. I weigh 185lbs and have wondered if that's too much weight for a 17lbs bike?
Well, you're riding a seriously low budget bike there first of all. The Scattante's are not built so good from what my friends who work for Performance tell me, and the geometry of the frames are usually a little more "different" than standard road bikes out there (racing style).

No, 185 pounds isn't too much for a 17 pound bike.

Check all your wheels, bearings, headsets, and other things that people said. Check for cracks in your head tube, and fork, like get in there with a bright flashlight and really look just to make sure.

That being said, if it wobbles again, pinch the top tube with your knees, that will smooth things out.
 

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I had a case of the wobbles too desending at ~40mph.. turned out my rear wheel bearings were just a tad loose and needed to be adjusted.. I haven't been able to test it out again but i'd assume it'll be gone now that the rear wheel is tight again.

take it into a shop for a quick check up if you're unsure.. better safe then sorry with a ton of road rash on ya.
 

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Discussion Starter · #13 ·
magnolialover said:
Well, you're riding a seriously low budget bike there first of all. The Scattante's are not built so good from what my friends who work for Performance tell me, and the geometry of the frames are usually a little more "different" than standard road bikes out there (racing style).

I think doubts about the quality Scattante frames is the stuff of cyclist legend. It starts with the name and goes downhill from there. At the time I bought it I learned that the frames are built in the same factory in Taiwan as other "name" frames. Also, think of the logic of having a "a little more different" frame from Performance's perspective - they are selling to the masses, think most common. It doesn't make sense on a host of levels that they would go fabricate a whole unique frame for themselves.

Anyway, going with the idea that the frame is "low budget" and "a little more different", what are the tangible characteristics that I can look at or have looked at that are low budget or different so I can avoid them, if, in fact you are right?
 

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RoadLoad said:
When I read reviews and company literature, I often see the phrase "improved stability". While I understand the concept of rake as a way of affecting a bike's handling (40mm rake is good for crits and quick handling, 45mm is good for touring), what are the other aspects of fork design that can affect overall bike stability. Or, to put it another way, what are the characteristics of a "stable" fork so I can get one?

If you do get another fork, make sure you go in the right direction with rake. As said in another post, less rake = slower steering. You have it reversed in your original post.
 

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Agree with all the checks suggested by others. You dont want to ride with a mechanical problem.

This last winter I had multiple problems with high speed wobbles. Always above 35 mph. Here is the kicker, never found any problem.

Rode that same 3.5 mile downhill twice this weekend above 40 mph and the bike was great.

I believe a combination of road condition, temp and rider input created my problems.
 

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Speed has never made me wobble.. my bike actually feels like it stiffens up a lot when i get moving faster.

Are you staying loose?
Are you staying balanced over the bike?
Look further ahead and not at the front tire?


Of course the headset might be wacky like already mentioned.

Good luck!
 

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Discussion Starter · #19 ·
I believe the Tempest II wheels I have, use sealed bearings in the hubs, not the older cone style. In this respect, is there the same opportunity for the bearings to come out of adjustment? Thanks for all the discussion, I'm very appreciative.
 

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No one has mentioned tires. If you have been up to similar speeds on the same bike without problems, I'd take a serious look at the condition of the tires. If they are worn to where they are a bit flat down the middle, that can make a tire unstable as you go from the flat spot to the ridge where the tire starts to round out.

Also look at your fore/aft position. If you don't have enough weight on the front wheel, it's get more squirrely. Try putting more weight on the pedals and handle bars. Not a LOT of weight, but don't sit back on the saddle and let your weight move too far back. You need to have some weight on the front wheel to keep it tracking properly.
 
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