Tank Slapper WTF?

[Jack D]

I have seen this problem mentioned on every forum on every bike I have owned since internet forums started. Everyone has an opinion on what causes it as do I. I have had it happen with new tires of different brands, tapered headstock bearings and fork braces. But it only happens when decelerating. It never happened to me on my GL1800 when the cruise control was engaged, it has never happened on my FJR when the throttle lock is engaged. It never happened to me on my GL1800 again once I installed higher rate fork springs. I no longer take both hands off of the bars when decelerating on any bike.

 

[Graham Downunder]

Deceleration is no time to take both hands off . Gyroscopic effects of rotating wheels slowing down on a pivoting system with varying rake , trail and of course weight transfer on a system designed change direction quickly that you remove the stabilising effects of your arms ,then moving the mass ( your body) around even slightly I would have to say is asking a bit much . Worn tires add to the problem

First up check tire type and pressure I run 42 psi in front and back as I have found the front tire is less likely to cup and any slow leak over a few days will just reduce it a bit . Road Pilot 3 are great as most will testify .

 

[bgross]

I have seen this problem mentioned on every forum on every bike I have owned since internet forums started. Everyone has an opinion on what causes it as do I. I have had it happen with new tires of different brands, tapered headstock bearings and fork braces. But it only happens when decelerating. It never happened to me on my GL1800 when the cruise control was engaged, it has never happened on my FJR when the throttle lock is engaged. It never happened to me on my GL1800 again once I installed higher rate fork springs. I no longer take both hands off of the bars when decelerating on any bike.

BINGO!

As the post above mentions, the dreaded decel-wobble is not at all uncommon. Many of my fellow Wingabago owners report the phenomenon, and the common denominator is... Taking both hands off the bars while decelerating.

Once you've eliminated the possibility of bent frame, mis-aligned forks, etc., and replaced that worn tire, just remember to keep at least one hand on the bars.

Patient: "Doc, it hurts when I do THIS."

Doctor: "Well then, don't do THAT."

 

[KTMRIDER]

PO offered to send me a check for 75 bucks to go towards a new tire. That was nice of him.

FYI. Been riding since 1977 and never had a bike that did this

Now onto new tires. It has PR2s now. When I was at Iron Pony a few weeks ago and had a set of Conti Motions in my cart and ended up putting them back. I assume the general consensus is to stear clear of them? Hard to pass up $157.00 a set tires when they get great reviews everwhere but on this site.

 

[El Toro Joe]

PO offered to send me a check for 75 bucks to go towards a new tire. That was nice of him. FYI. Been riding since 1977 and never had a bike that did this Now onto new tires. It has PR2s now. When I was at Iron Pony a few weeks ago and had a set of Conti Motions in my cart and ended up putting them back. I assume the general consensus is to stear clear of them? Hard to pass up $157.00 a set tires when they get great reviews everwhere but on this site.

Oh, you can use the Conti Motions...just don't expect to get very many miles out of them

 

[radiummadman]

Go get yerself some new tires...
I believe this place this has the best prices on PR2's...

https://stores.sportbiketrackgear.com/Categories.bok?category=Motorcycle+Tires%3AMichelin+Tires

Murph's Kits has a set for FJR 260.00, ordered and received in 3 days.. Plus he is a nice guy & independent.

 

[Bounce]

And up the PSI above factory since you're not running factory rubber any more. A lot of people have found that 41/41 on the PRs (as well as a smooth application of the right wrist) can extend the life of your tires significantly.

 

[art miller]

+1 on the PR2's. I just changed out my rear PR2 with 15,528 miles on it. The tire still had 2.5 32nd of tread. I run 42psi.

 

[KTMRIDER]

Got a front pr2 for 128 locally. Not too bad I guess. Test it out tomarrow

 

[ShowMeMo]

KTM... don't overthink it. This is simply the FJR kicking you in the balls for trying to ride no handed...

Yamaha put that in as an early warning detection system.... a safety feature that can't be ignored!

 

[KTMRIDER]

Pleased to report my front end issues appear to be resolved with a new PR2 mounted up front. As an added bonus by the high speed smoothness the old tire was out of balance too.I will say kinda surprised the tires were installed as a matched set by the previous owner and the rear outlasted the front?

 

[russperry]

My '08 has the same tendency - increasing amplitude bar shake in the 20-50mph range. Observations;

1) New tire helps but does not eliminate entirely

2) Steering stem bearing have been torqued to factory spec - no change in behavior

3) Decelerating is the worst, but with cruise engaged in the bad zone the wobble is there, just not as pronounced

4) Never have had this happen on another bike (owned 7 others), and there are enough records in the forum here to make me think it pretty common on these bikes, moreso than others.

My prediction - new tires will help reduce but not eliminate your bar shake.

Good luck

 

[Nanahanman]

I have seen this problem mentioned on every forum on every bike I have owned since internet forums started.

Went through this with an ST1100 and tried all the tricks..and I mean ALL.

Was using Avon Storm tires for years and as soon as I changed to a Pilot 2...gone...totally and completely gone.

It seemed, generally, to be more of an issue with Avon in the US as compared to Europe. Different tire manufacturing facility, we figured.

It would be interesting to poll users on magnitude of problem and tire brand.

 

[lnewlf]

once all the bases have been covered, including and especially a good front tire, revisit the steering head bearings..IMHO the factory torque specs are low..I forget about the torque wrench and raise the wheel off the ground-then tighten the bearings until the bars slowly rotate to the stop on either side with a gentle nudge..If the bars flop to the side the bearings are to loose..never mind the torque reading..You will know if you have torqued the bearings to much as you will have a slow weave when riding..

 

[dcarver]

No problems at all since replacing steering head roller bearings with tapered..

 

[HotRodZilla]

No problems since I don't see the need to let go of my bars while I'm slowing. Duh!

 

[CAJW]

You guys are all missing the real factor here. The DOT years ago, while developing standards for Modular helmets knew this might become an issue and mandated all Modulars be designed to exhibit ALSIIS (aerodynamic low speed induced instability syndrome). That way when the rider attempts to ride above 7.5 mph without the chinbar in the down and locked position, the aerodynamic flow is disrupted in such a way that the oscillations from the turbulent airflow of the raised chinbar are transferred via a vortex generator built into the helmet and sets the front end awash to alert the rider that he forgot to lower and lock the chinbar. I do not believe this syndrome has ever been reported by female riders, as I understand it (from my wife!) that women are, "ahem" smarter than that! That is why I do not advocate riding with a Modular helmet, too damn dangerous! So..... there you have it.

 

[LAF]

once all the bases have been covered, including and especially a good front tire, revisit the steering head bearings..IMHO the factory torque specs are low..I forget about the torque wrench and raise the wheel off the ground-then tighten the bearings until the bars slowly rotate to the stop on either side with a gentle nudge..If the bars flop to the side the bearings are to loose..never mind the torque reading..You will know if you have torqued the bearings to much as you will have a slow weave when riding.

We did this on our Harley s as it was the only way to adjust them. It was called "fall away". If they slammed over you tightened them, if it was slow or bound you would loosen them. After a time or two you could tell when fall away was good.

Not sure if it applies but it was how we did it on them.

The procedure on the FJR seems like a strait forward way with torque as the value but fall away does tell the true story. I set mine at 0 miles on my 10 and have not touched it since.

I have no issues but have had a decel head shake no hands trying to get a damn glove on but it was on end of life of the tire also. I just do not ride no hands. On the K1200 LT I could ride miles and miles no hands and never an issue.

As the doctor said "just stop doing that".

 

[TwoWhldTerror]

My FJR has always had a wobble when the front tire gets worn down. Only occurs at around 40-50mph and replacing the tire improves it (but it never really goes away). Only occurs when I take my hands off the handle bars at that low speed.
Replace the front tire and you should be good.

Same here