Tank Slapper

[jsmx9014]

Guys 'n Gals, this one scared the *&*7! out of me. Here's what happened. I was riding along on dry pavement, warm day, nothing out of the ordinary, speed was about 20mph in a residential neighborhood. My right glove had slipped down and I momentarily let go of both handlebar grips to pull the glove up. In an instant, the handlebars started to wobble back and forth and get progressively worse. By the time I could grab them, I was almost in a full blown "tank slapper". Now, the instant I gripped the bars, the wobble stopped and immediately smoothed out. But, I can just imagine this happening at 70mph. And, I don't know if I could stop it.

Anybody got any ideas what the heck would cause this? I've checked the forks, triple tree and steering head. Everything seems to be tight, without any obvious play. And, I recently replaced both tires and replaced fork oil, etc. Any suggestions? Thanks! John

[Rat]

Welcome, if it hasn't been said.

The dreaded wobble is much discussed, on many bikes, not just these.

Sounds like you've covered the obvious bases, but don't forget the back end can contribute.

Try a search here and on the Saunders Forum.

You'll be reading for a week.

Gord

[boneyard]

its your knees. tank slap occurs when the knees are loose. if you allow your knees to slacken and cannot compensate with your arms then you get tank slap. knee hip action will control the direction of the main body of the bike the arms control the steering. the dynamics of motorcycle riding are learned generally through experience and you never think about what is really going on. Think about it tank slap never happens to a rider who is standing up with heels dug in and hands gripped strong. It does happen when there is a front back action such as moguls to a seated rider. Your tank slap occured when there was probably a bend either at your knees or hip causeing the bike to bend at the steering head this caused an angle between the front and rear wheel with over compensation by your knee hip action. The irony of the whole situation is that if you were at speed say 45 or 50 the gyroscopic action of the wheels would have prevented the whole event. There is a wonderful film clip of a rider at the isle of man back in the 1960's With a terminal tank slap event that is wonderful tool for teaching. Tank slap is relatively short with a very violent end. but this event filmed is perfect you see the begining and end at about 80 miles an hour. in slow motion you see the rider over compensate about 10 times each one getting worst and worst till the tumble and the rider is thrown. The only true way to over com tank slap is to bear down on the pegs and pull back on the bars and hope that one of the wheels digs in.