I was coming down a rather steep grade when the rear end began to fishtail or shimmy back and forth. Can you tell me what might have caused this to happen and what to do to stop it once it starts? Afterward, I had the bike checked over by my mechanic and it was fine. Thanks for any helpful suggestions you may have.

Did you use the brake? As I was informed in a recent thread of mine, using the rear brake at high speeds can cause problems such as locking of brakes, which can lead to fishtail.

Not enough weight on your rear wheel. Slide your rear end back to the back of the saddle.

You have reflectors on your wheels?

As you brake, your weight shifts forward, and more so on a descent. There is a point where the combination of brake pad pressure and lack of weight on the wheel will cause it to break its hold on the road and lock up. You crossed it. Read on and around for proper body position and brake application on descents.

Too much weight on front wheel.

Did this the other day - popped my rear end out sideways at 38mph, bent the rim way over. But held it and didn't go down. Should've died, really. RIP wheel.

When you are braking hard on a descent the weight transfer makes the rear very light. If you hit a small bump the rear wheel will get even lighter. So if you have the rear brake on too hard, you will lock it up.

The solution is to use less rear brake. If you do start locking up the rear, back off the brake.

Where were your hands? drops or hoods? If on the hoods, this would lead to the aforementioned forward weight distributions and hence the fishtail.

Too much rear brake + too much forward position

90% of the time, your rear brake is just something for your right hand to do while your left hand/front brake does the work. It doesn't add any stopping power, and can cause the rear wheel to lose traction. As others have said, shift your weight [what feels like] way back (look at some pictures of DH mountain bikers and how far they get back... clearly you don't need to go to that extreme, but it illustrates the point nicely), and don't touch the rear brake. The exception is that when it is wet or icy and there is a risk of the front wheel skidding. You rarely can recover from a front wheel skid, but if just the rear is skidding you're usually fine, so in these conditions use the rear more.

check for a rear flat....doesn't have to be completely flat but if the tire is losing air it will definitely do this.

Watch the Tour carefully and examine how the pros descend. You'll see them shifted far back on the bikes. Study their body and hand positions.

well without a doubt, the thing NOT to do when the rear is fishtailing is use the rear brake, at all. As mentioned, shift your weight back on the bike when descending, if you start to fishtail and the coast is clear, get off the front brake, and transfer weight to the rear wheel, SLOWLY.

You wrecked a wheel without even coming off? Respect.

Matthew

Forget that the right lever even exists.

but skip the Voight video

Actually, it was the Voigt video that prompted this thread. Scary stuff that. Poor Jens!

Thank you for your help--I know now what I did wrong. Too much back brake, not enough front. I'm new to the drops, and am just now getting used to the difference in pressure on the brake levers. And to make matters worse, I applied more to the rear after it started to skid. (I'm ok on putting weight to the rear, I think.) Your advice might save my skin (literally) on my next attempt. Thank you again.

Any additional advice is most appreciated.

That!

Also, don't watch Zabriskie descend at 45mph on Stage 16 with his ass off the saddle/in the air, and chest on the bars, pulling the peloton... but what does he know?

Also, it looked to me that Voight was on the white line when he lost control- I wonder if he slid out on the paint?

It seemed that he got bounced off the saddle at the same moment he was moving his left hand to the drop. The pressure on the right side of the bars from his right hand caused the bars to turn left.

I did this at 44mph.

Result - Leg broken in three places and a feeling that I was actually bloody lucky.

Check out Sheldon's article: https://sheldonbrown.com/brakturn.html

Did you fishtail like this?

https://www.youtube.com/watch?v=RtZhG2kWVLY

No, no. Poor Beloki. He apparently lost his rear tire and was sliding on the rim.

So am I to understand that the front brake is used exclusively? One bit of information I neglected to include in my original post is that the roads here are in extremely poor condition.

And thank you for the article. It is very informative.

hell no! I paid for it, I'm going to use it.

Used with some discretion, it will help slow you down.