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Old 02-06-06, 08:41 PM   #1
dbmcclus
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Bike Control / Fast Speed

I have only been riding a rode bike for about a month now. Before that, I was on a comfort bike. I have a new Trek Pilot. Up until last week, my fastest speed was 28 mph on a flat stretch in the drops. This past week, I did something really stupid! I climbed a fairly large paved hill in my sub-division and then started back down. Instead of placing my hands on the hoods so that I could reach the brakes, I placed my hands on the top of my drop bars. Big Mistake! Before I knew it, I was doing 37 mph and the bike was getting very unstable. I had a very difficult time controlling the front end. It was shaking badly. I have been told that probably there is nothing loose in my fork/headset, but that by holding on at the tops, I had very little control of the bike. I was also told, that a very small movement on the top could translate to a large movement on the bike.

I am now afraid to go down steep hills. I know I will never go down hills w/o my hands on the hoods in case I need to break, but do you think if I hold on to the hoods next time, my bike will be much more stable at 35+ mph?

Thanks.
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Old 02-06-06, 08:54 PM   #2
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30+ mph is intimidating for most new riders. Bicycle stability at these speeds is highly variable due to a number of factors related to the geometry of your ride. Riding down hill with your hands on the hoods allows your upper body to provide more "sail" area creating drag that will slow you down. So take it easy and slowly build up to speeds you are comfortable with. Stay in control and enjoy it -- crashing at that speed is not an option!
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Old 02-06-06, 10:44 PM   #3
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Yes, I believe placing your hands on the hoods will add greatly to stability as compared to where you had them. It will give you a wider stance and give you immediate access to the brakes. Also, a new bike, especially a higher performance one may take a bit of getting used to. Even if I've been off of my half bike because I had been on the tandem for perhaps a few weeks, it feels real squirley. It takes me a few miles to regain my confidence. Take it easy and build up your speed little by little, pretty soon you'll feel comfortable at higher speeds.
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Old 02-07-06, 02:35 AM   #4
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Check your wheels, make sure they are true both front and back. Also check the tires and tubes for any informities. Small incognizant movements of your hands could also introduce instability when placed near the center. Putting your hands away from the center will obviously reduce instability, however, there shouldn't be any in the first place.
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Old 02-07-06, 05:59 AM   #5
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Quote:
Originally Posted by dbmcclus
Before I knew it, I was doing 37 mph and the bike was getting very unstable. I had a very difficult time controlling the front end. It was shaking badly. I have been told that probably there is nothing loose in my fork/headset...
Thanks.
Did you remove the reflectors from the wheels? If not, this could explain why the bike is stable at lower speeds and unstable at higher speeds. Wheel reflectors are installed by law on all new road bikes, but are of little safety value for most of us (after all, they're only effective if you're crossing perpendicular in front of the path of a vehicle at night), and definitely can cause instability at higher speeds.
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Old 02-07-06, 06:35 AM   #6
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See 55/rad's recent thread about shimmy. There's a good discussion on pages 2 and 3 there.
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Old 02-07-06, 07:36 AM   #7
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OR--- Do as I do; say a prayer, tuck in tight, keep the head down, losely grip the drops, and let her rip! Flying down hills (on a bike or skis) is the only dangerous living I do. ENJOY!

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Old 02-07-06, 11:58 AM   #8
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Relax. Wobbling for no apparant reason is usually caused by the rider's hands being "white knuckled"
on the bars. This could be magnified by being on the tops of the bars. I quite often have my hands on the hoods on decents and can brake quite heavily.
With the hills up here and my mass I can exceed 40 mph on downhills with no wobbles.

Good luck
John
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Old 02-07-06, 12:19 PM   #9
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There's been a ton of stuff written about that, most of which you'll probably find with the links you already have. I used to have a Motobecane that ALWAYS did it at speeds above about 38mph. Fortunately, I don't go that fast very often, so it wasn't a big problem.
All the advice about checking balance, bearing adjustment etc is good, but don't be surprised if it doesn't fix things. I tried everything on the Moto, even had it checked by a former Olympic team mechanic who used to run a bike shop here, and nobody ever found a cause.
One thing often suggested to control the bike is to grab the top tube with your thighs, to damp the vibrations. Never helped me much. Riding in the drops may help, too, but usually I just slow down.
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Old 02-07-06, 02:03 PM   #10
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I ride a mountain bike so not much help on this problem- Or is it? I ride with a wide handlebar-27"- and obviously am always covering the brakes. There has never been an occasion on the road when that bike has felt unsteady. (Offroad gets a bit hairy but how else can I catch the others Up?) Whether it is the stiffer frame- wide bars or the thought that the brakes are always to hand- I do not know. Then there is the Tandem- but this is inherrantly stable at high speed. The long wheelbase, wide bars and the top rate brakes on this thing all add up to a bike that handles and you have confidence in when gravity takes over.

I think that is the point- Confidence. That has to be gained by experience. One thing for certain is that you will always be covering the brakes when momentum builds up- Experience gained. Then again there are points such as putting weight back on the saddle, which brake to use when,(Rear initially at first to stop front wheel skids)And other items such as sitting up to slow down a bit and get a better view of the road. Speed is not a problem- Its how quick or sudden you stop that causes the problems.

Then as to high speed- the hills vary- not only on steepness but quality of the surface. That will affect confidence a lot and handling. Back to that Tandem again- Top speed was 53.8 mph---Offroad. Highest speed on the road with slicks fitted--52.8mph. If you have confidence- speed will come with ease. However with us, we just haven't found a steep enough road to beat our offroad speed.
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Old 02-07-06, 03:34 PM   #11
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Quote:
Originally Posted by rm -rf
See 55/rad's recent thread about shimmy. There's a good discussion on pages 2 and 3 there.
around
This is the definitive response!!!!! Dave Moulton's explanation of your problem is right on!!!! I have (3) road bikes and one of them does the same thing but very mildly. I find that if I keep the weight forward it doesnt do it but if I sit up and transfer the weight aft then I will start experiencing instabilty at about 35 mph.
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Old 02-07-06, 03:41 PM   #12
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I think Bearbig hit the nail on the head. Sounds to me like you must have a death grip on the bars causing every movement you make to be transferred to the front wheel. Once you get more comfortable on the bike and gain more confidence, you will find that a light grip works much better. If you find youself in a situation where your hands are in the wrong position on the bar, move them. You won't fly off into outer space if you release your grip to move your hand along the bar to a new position. Relax!
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Old 02-07-06, 06:00 PM   #13
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Jiggling handle bars like that at high speed downhill has to be the most frightening was to ride a bike. Unlike other posters, I have no instability problems with the reflector on my front wheel. Perhaps they have a very light wheels.

Does your bike track okay at low speed? Can you ride it hands off at low speed? If so, the bike should be okay.

Perhaps you may want to check either the alignment of your front fork, or make sure that the bearing race at the crown of the fork is perpendicular to the fork. Sometimes they are a tiny bit off. Make sure your wheels are well attached and that the the bearings and bearing races are in good shape.

I've got one steep hill on my morning commute, it gets me up in the upper 30s daily. It's straight, so I put the pedals level with each other and slide back on my seat. This moves my center of gravity back to between the wheels. This adds noticeably to how stable my bike feels. I extend my arms and hold the bars firm but not tight. The handlebar doesn't have too much latitude to jiggle.

The best way to approach the hill is just go up part way. Turn around, cross the highway and go back down. When you are confident there, go up farther.

Have fun.
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