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High speed safety(16 posts)

High speed safetyContinental
Dec 4, 2002 10:42 AM
I've been riding on and off since 1975, but have always lived in the flatlands or avoided hills. The past few weekends I've done some hill work and hit 48 mph on the descent. That's at least 10 mph faster than I've ever ridden. It was a rush, but I'd like advice on how to do this as safely as reasonable. I have a 2002 Fuji Finest, everything stock except the pedals which are Shimano SPD road. I'm 43 and in good shape, but don't think that my body would stand up too well to an intimate relationship with asphalt. My only safety lesson so far is not to tell my wife how fast I ride.
tell her, but...merckx56
Dec 4, 2002 11:05 AM
don't show her. Coming down off of Caesar's Head in NC one year, my (now) wife was following us in the car. It's a pretty big descent and gets twisty in places. I hit just under 60 mph with her following and then lost her in a twisty section. We loaded up to come home and her general opinion of everyone who rode that day was one of both admiration and thinking we all had a deathwish! Tell her to hang her head out the open car window at about 45mph!
Think about it this way; if you do come off at 50mph, you'll probably pass out from the pain anyhow!
Let's face itColnagoFE
Dec 4, 2002 11:11 AM
If you biff at 50MPH you might well buy the farm. There is no way to do this with total safety, but keeping the speed to something that you feel confortable with is a good rule of thumb. If the road is really wet, debris laden or twisty then keep the speed down some. Pretty much just common sense. I've gotten up to about 60 before but that was in good conditions, fairly straight steep and clean road. If a front tire blows at that speed all bets are off, but this isn't a risk-free sport. If you want more safety just don't ever go that fast.
Like running a red light in your mother's car....grzy
Dec 4, 2002 11:27 AM
You know you shouldn't do it, it scares the hell out of you at the time, but you just know you'll do it a again for the endorphin rush.
good luck with thatmohair_chair
Dec 4, 2002 11:33 AM
You can't ride a bike at that speed safely. All you can do is risk management. Lots of things can take you down that you can't even prepare for, so mostly it isn't worth worrying about.

In terms of risk management, it's best to let if fly only on roads you know, or at least have ridden up first. Also, if you are going as fast or faster than traffic, take the lane. Don't ride the shoulder where all the crap is.

High speed is a rush, but I get a bigger rush doing 35 mph around a tight curve where there is a big sign that says 20. Leaning the bike way over in a turn is great fun. There are many descents around here where you can leave the cars following you in the dust doing stuff like that.
Press knees against top tube...biknben
Dec 4, 2002 11:41 AM
The bike becomes much more stable if you level your pedals and press your knees against top tube. It adds another point of contact between you and the bike.
A fast bike is a stable bikePODIUMBOUNDdotCA
Dec 4, 2002 11:51 AM
Its true that a fast bike is a stable bike. This is why its easier to go no hands at higher speeds. When your descending though you just have to make sure to ride within your limits when cornering but the thing is losing traction on a road with no gravel or debris is very very hard so just relax and be confident.

You must be kidding...VertAddict
Dec 4, 2002 7:57 PM
Your statement that a fast bike is a stable bike is only true within a relatively narrow band of speed. Once you exceed a modest speed, your chances of getting a high-speed wobble go up with every mph you add. And just try letting go of the handle bars at over 45 mph, and give Darwin's law a chance to work. I was just moving my hands into the drops on a fast descent and got a high speed wobble I'll never forget and never want to experience again. I had to change my shorts after that one.

You need to be careful dispensing this crap, you're going to get someone killed.
You're the joker!grzy
Dec 4, 2002 8:19 PM
First, stability and manauverability are inversely related, by defintition. One increases, then the other decreases. A more stable bike is always a more stable bike regardless of the speed, but at the price of cornering. There's no "chance" involved in a speed wobble it's strictly a function of bike design, riding conditions and rider skill, mostly rider skill or lack thereof. The trick to keeping the speed wobble at bay is to maintain a loose grip on the bar and keeping a light touch as it were. If you try and strangle the bars then you're much more likely to setup the speed wobble conditions - it's becomes a dynamically unstable system due to the rider input being out of phase. A bike doesn't get the speed wobbles by itself.

If you find yourself needing to change you shorts frequnetly then it's probably best if you slow down and stay to the right while descending. Life begins at 50 mph.
How about those low-speed wobbles?VertAddict
Dec 4, 2002 9:04 PM
I won't disagree with you that I should keep my speed under 50, I do that already, but the fact is it's easier to get the wobble at high speeds - that's why there's no low speed wobble.

I've experienced a wobble twice on a motorcycle as well, and in both cases the bike was at a steady (but high) speed and on a straight road, and the wobble was induced by a rut in the road. Clearly, the unstable system you mention was caused by something other than rider input, and the speed helped create that signature harmonic vibration of high speed wobbles.

I appreciate your point about gripping the handlebars too tight, I'll watch for that in the future. However, the point Podium's original post seemed to be making was: the higher the speed, the more stable the bike, and that is just not true. Your own response proves it: the fact that my "rider error" of gripping the handlebars too tight causes problems at high speeds which are not evident at lower speeds shows that the bike is more susceptible to small variances in pressure etc. at higher speeds, Q.E.D. more unstable.

I'm perfectly willing to leave you to your macho world of life over 50; I'm not in this sport for near-death experiences. However, I would advise you to stay to the right on the uphills... that's where I'll be passing you.
Out of phase motion is out of phase motionniteschaos
Dec 5, 2002 8:18 AM
On a motorcycle especially, the heavier wheels generate incredible gyroscopic forces to stabalize the bike. If you've ever seen someone drop their motorcycle in a parking lot, then you know that out of phase rider input can occur at any speed, even zero, hence trackstands are so tough.

the world record speed for a motorcycle is well over 360mph. I know that this was a specifically engineered bike with two motors and long wheelbase, but the longer wheelbase was used cheifly to increase the period of motion of direction change, making it easier for the operator to stay in rythm.
Perhaps it was operator errorniteschaos
Dec 5, 2002 8:10 AM
I've ridden all the way up to 63 mph and never experienced a wobble. If I were you I'd check my frame and wheels out, or have a pro do it for me before something bad happens to you.
Calculations while ridingbigrider
Dec 4, 2002 1:25 PM
If you are NOT calculating how bad you would get jammed up IF you bit the pavement, you're not going fast enough.
Dec 4, 2002 2:05 PM
IF you are calculating how much skin you'll lose WHEN you wreck at your current speed THEN you're going too fast.

I guess the operating assumption would have to be that ignorance is bliss.
whatever you do, don't tell your wifeDougSloan
Dec 4, 2002 2:23 PM
I told my wife I hit 64 mph in the dark. Not good.

Recommendations from a downhill speed freak:

1. Eye the road ahead like an F16 fighter pilot in a dog fight. Do not hit anything.

2. Listen for sand or gravel under the tires. If you hear it, don't turn or brake any more than you have to, and then very gently.

3. Keep your weight balanced fore/aft.

4. If there is any turning, braking, or rough road, get your butt off the saddle. You have much better balance and control with suspended by your arms and legs.

5. Don't do anything sudden.

6. If you have a blowout, first, remain calm; then figure out which tire it is -- this is not as obvious as you might think; then, slow down using the brake on the other wheel; keep the bike vertical, and unweight the blown tire; do not try to turn (short of going off a cliff or under a car)!

7. Wear glasses so you can keep your eyes and reduce watering from the wind.

8. Use the drops for better balance.

9. Pull your knees in against the top tube, except when unweighting the saddle.

10. If you are around other riders, don't touch any wheels, and don't swerve around -- two very bad things.

First and foremost though, and worth repeating, watch the road. Hitting a 2x4 at 50 mph is really scary (done it).
The only thing I would add is don't use worn out tiresChainstay
Dec 4, 2002 4:26 PM
Especially on the front