Tankslap caused by windshield?

[Texan]

Last week I was riding some backroads and came upon one of those reeeealllly looong straight and slightly downhill stretches of road that just beg for a downshift and right wrist. You known the kind. You can see the whole road, no inlets or outlets, and no cars for miles.

I had the stock windshield all the way up and when I hit about 128 I started to get the beginnings of tank slap. The speed was measured after the fact by GPS. As soon as the wobble started, I braked to a safer speed.

There were some winds that day and I don't known if they were head, tail or cross winds.

Could the fully raised windshield be the cause or part of the cause of the dreaded wobble?

 

[FJRay]

Last week I was riding some backroads and came upon one of those reeeealllly looong straight and slightly downhill stretches of road that just beg for a downshift and right wrist. You known the kind. You can see the whole road, no inlets or outlets, and no cars for miles.
I had the stock windshield all the way up and when I hit about 128 I started to get the beginnings of tank slap. The speed was measured after the fact by GPS. As soon as the wobble started, I braked to a safer speed.

There were some winds that day and I don't known if they were head, tail or cross winds.

Could the fully raised windshield be the cause or part of the cause of the dreaded wobble?

Never happened on mine reguardless of shield or position and it has seen excess speed more than a few times. Did 156 through the traps at Bonneville .

 

[escapefjrtist]

Never have had a hit of a wobble at speeds I won't admit to. Several different shields from stock to CB 4/3. With the rake and trail we have, the FJR is pretty darn stable at (any) speed.

--G

 

[JDog]

That seems a rather odd theory. I was out "exercising" my FJR today. Since it is new to me I was experimenting with windshield heights, speeds etc.... not a huge fan of having the screen all the way up but I did have it fully extended doing 145mph today....moderate back pressure but the bike was solid as can be. Can't imagine the screen height causing such an issue. Time to do a top to bottom inspection.

Good luck

 

[RsvlFeej]

Could the fully raised windshield be the cause or part of the cause of the dreaded wobble?

Trunks/top boxes have been known to cause high-speed wobble. Do you have one?

 

[FJRBluesman]

Never heard of the widescreen starting a tank slapper.

BTW - Maybe it's just me, but at higher speeds (lets leave it at that), I'd have the windscreen in the fully down position. Those poor cheap pot metal parts can only take so much, and holding up that big front door at that speed is stressing those poor little guys IMO.

Maybe your tires are at issue (low pressure, cupped, etc). That's what I would first suspect for a high speed wobble, that and chassis set up.

Good luck.

 

[marcusorelius]

2nd day I had my ole connie was going downhill at 120 with a cross wind, developed a high speed wobble, never got one after so i think a down hill angle & cross wind may be the cause.

 

[Wee Willy]

Tire and front suspension reaction (from steering head bearings all the way down the dynamics chain to tire pressure) drive this dynamic behavior. Tire characteristics have the biggest impact under "usual" conditions. There are a lot of links in that chain too. I suspect windscreen position is not a primary culprit...but remember that it ony takes a few flakes to start an avalanche.

Changing front tire from OEM Bridgestone POS to Michelin PR2 has completely cured my ride of this characteristic.

YMMV.

Cheers,

W2

 

[wfooshee]

+1 on the front tire. Tire wear can induce steering wobble at really low speeds, too.

 

[majicmaker]

+1 on the front tire. Tire wear can induce steering wobble at really low speeds, too.

This is Soooooo True. At higher Speeds too. Don't ask me how I know that!

 

[BanjoBoy]

Last week I was riding some backroads and came upon one of those reeeealllly looong straight and slightly downhill stretches of road that just beg for a downshift and right wrist. You known the kind. You can see the whole road, no inlets or outlets, and no cars for miles.
I had the stock windshield all the way up and when I hit about 128 I started to get the beginnings of tank slap. The speed was measured after the fact by GPS. As soon as the wobble started, I braked to a safer speed.

There were some winds that day and I don't known if they were head, tail or cross winds.

Could the fully raised windshield be the cause or part of the cause of the dreaded wobble?

Bet that got yer attention! Isn't the national speed limit like 75?

Doubt it's the windshield, like others, I'd suspect the front tire first. The short time I've been on this fine forum, I've heard a few tales where a bike feels like crap then the front tire is changed out, and it feels great again.

I had a low speed tank slapper yesterday myself.

My wife/sister and I were coming back from a little weekend jaunt up the coast. (Had fully loaded bags and top case on) At about 50 mph while coming to a stop sign I took my hands off the bars to stretch my arms, and this always rock solid FJR, went into a violent head shake. I tried it another time and it did the same thing. What a rush!

I checked the tire before we left and it had 41 psi, but it's getting a little worn, (About 5,500 on an Z6) and It feels kind of funky.

Guess I'll check the forks, and steering head bearings today, and maybe try to re-enact the crime with out all the bags, top case, wife/sister on back. But I'm 80% sure it's the funky-ass front tire.

Good luck,

 

[bikerkash]

If it was caused by the windshield I guess it's just another good reason to lower the windshield and tuck youself when you crank it up.

 

[Ed_Grant]

Only time I've had a high speed wobble on the FJR was fully loaded w/Tanji tank & large MotoFizz seat bag at about 130 mph. Let off the gas and the bike calmed down. The day before I did a max speed run with no problems w/o all that weight on the back.

 

[painman]

Personally suspect wind as the culprit if bike is in good working order and the front forks are at the same settings. Agree with Wee Willy but when I installed the PR2's new before leaving to WFO-8, I experienced not a high speed front end wobble but a series of wobbles of the whole bike at normal speed that just felt "very" unstable. But I believe those three instances were due to high side winds and the fact the bike was loaded for the trip. Hope you get it figured out. PM. <><

 

[FJRless]

Are you sure you're not confusing a wobble or vibration with a tankslap? The only tankslapping I've ever experienced riding, with or without a steering damper, was on a sportbike (which has much more steeply raked forks) with the bike leaned way over, hitting an uneven surface in the road. In any case, I don't think any body parts on the FJR would cause or contribute to a tankslap.

 

[SwollenRaccoon]

+1 on the tire issue. Front tire wear will cause this. I've had it happen on the FJR as well as my old SuperHawk.

 

[BwanaDik]

[My wife/sister and I were coming back from a little weekend jaunt up the coast. (Had fully loaded bags and top case on)

Jeeze, so you really do look like the guy in your avatar?

 

[Carmine]

I used to have a mean wobble on decel with my old front tire ,CHANGED IT AND MY FRONT BEARINGS. Wobble all gone> I have a barn door for a windshield and ride with it up almost all the way at speeds i would never admit to typically faster than most would consider sane , also riding darkside with boxes bags and junk galore!!!!!! Front tire is the key CHANGE IT they are cheap enough when compared to the cost of say major surgery or the price of a new TITANIUM HIP... just saying.

 

[Jim Heinz]

Both of my tankslapping episodes were from defective tires

Could the fully raised windshield be the cause or part of the cause of the dreaded wobble?