r1150rt 40 mph wobble

[bvaughan]

my '04 rt has a front wheel wobble at 40 mph. short story long, i had the use of a wing for a few thousand miles and was surprised by a 35-40 mph wobble when no hand coasting. told myself it was the inferior japanese design. then experienced the same thing on the 1150. the shop said is was tire scallop, so i replaced the tire and no wobble. then 10k miles later, another wobble on the rt. replaced the tire thinking that was the fix. but no change: still the same amount of wobble.

 

shop says it could be bearings, but i don't think so; i know what bad/loose bearing feel/sound like and this ain't it. i think it could be balance, but shop says bad balance doesn't cause wobble, but some other kind of shimmy.

 

this only happens with no hands, 40 mph. decelerating from 50 to 30 the wobble will begin around 45 and build to max at 40, when the hadlebars are tweaking through about a 10-15 or so degree arc, and then reduces to zero about 35.

 

anybody else experience this? know what the cause is? know how to fix?

[flyingreg]

I would have to agree on the information you have been told. The steering head bearings may be loose (not worn) and the tire may be scalloped. I have experienced this problem on the wing as well, but not on the RT.

 

There are folks on this list that have considerable experience/knowledge and hopefully they will chime in.

[Rider1200RT]

Although I never experienced this on my 04 RT, the 05 LT I had was very sensitive to wheel balance and would shimmy at 40 without hands on the handlebars.(I know, I know you're not suposed to, but hey who doesn't?? ) The remedy was to re-balance the front wheel every 5K. I would check the head bearing as I don't know how many miles you have on your bike. The wheel bearings would be next and than the rim itself could be slightly warped. Did you hit anything???

Just my 0.02 cts..

[Harvey_Harrison]

The front end wobbles on my 05 RT, but the front tire is about worn out. I'll let you know if a new tire corrects the problem soon.

[UberXY]

Check the front tire pressure. My airhead has done this for 20 years, and when it does, the air pressure has always been low. A little air and it went away. Hope this works for you.

[Clive Liddell]

With 65000km on the RT is on it's 5th new BT54 all fitted and balanced to exactly the same standards by myself.

 

No 1 (Original) No wobble

No 2 Wobble at 60 - 80 km/h

No 3 Very slight wobble at 60 - 80 km/h

No 4 No wobble at all

No 5 No wobble at all

 

IMO it's something to do with the tire...

[Pictou]

I would look at the tire as well. I had a 99 VFR and tire choices could cause a head shake in the front end especially on deceleration from about 80 to 50kms (50 to 30 mph). Change the tire and the headshake went away. That isn't to say it isn't bearings but tires can definitely do it. Some bike and tire combinations just don't work well.

 

 

With 65000km on the RT is on it's 5th new BT54 all fitted and balanced to exactly the same standards by myself.

 

No 1 (Original) No wobble

No 2 Wobble at 60 - 80 km/h

No 3 Very slight wobble at 60 - 80 km/h

No 4 No wobble at all

No 5 No wobble at all

 

IMO it's something to do with the tire...

[SWB]

Pretty much "ditto" to everything everyone else has said. Air pressure, tire condition, tire balance, wheel damage, wheel bearings, steering head bearings, in that order I believe, is your check list. Maybe bent forks might be a concern, too, if you're bike's been involved in any front end "trama", but that'd probably be noticable earlier than 40mph. The new tire could be a lemon, i.e. really WAY out of round, making balancing difficult.

 

I've read before that at times a bike shop with a spin balance machine may not keep the calibration checks current. Your new tire may be slightly out of balance. This guy markets a nifty looking balancing tool, which is on my tool-shopping list for "some day". If I static balance it myself, then I'll know it's balanced.

[ShovelStrokeEd]

It's partially tire related, partialy steering head bearings and a goodly part, they all do that. Has to do with tiny road irregularities and tire irregularities causing the wheel to devieate from the straight and true. The geometry of the front suspension wants to correct this and then proceeds to overcorrect. For some reason, the mechanics of the matter are pretty complex, it occurs on almost any bike. I would suggest that it is somewhat related to wheel diameter, tire width and rake angle as neither my old chopper with a 40 degree rake angle and 21" wheel nor my Ducati 906 Paso with a 16" wheel did it.

 

For clarity sake, it is neither a wobble nor is it a head shake, as neither of those respond to the minimal damping (one hand lightly on the bars) required to remove it. Nothing is really "wrong", it is just part of the mix. Don't make yourself nutz. Just ride along and enjoy, hopefully with at least one hand on the bars.

[Wooster]

....

Nothing is really "wrong", it is just part of the mix. Don't make yourself nutz. Just ride along and enjoy, hopefully with at least one hand on the bars.

 

Ditto. Many bikes experience a slite wobble, "hand free" deccelerating thru 50 to 40 mph. The usual suspects include most of what's been listed in prior posts (though "bent forks" would be extreme, IMO). In addition to tire wear and airpreasure is the combination of front & rear tire "newness" for want of a better term. A new front paired with old rear can cause this decceleration wobble, in my experience.

Funny, we (includes me) want our bikes to be steady in all conditions, even w/o hands on bars. When I first noticed this decceleration wobble, a bmw mechanic looked at me as if I broke wind in church and said something to the effect, "you're crazy to ride w/o hands on bars": I had no retort as it is crazy (perhaps better stated as "illogical") to ride w/o hands on bars. After all, what are we doing, riding a bike or knitting a sweater ?

So, while Ed's post (only partially quoted here) has many good points, I find his ending, i.e., "just ride along and enjoy hopefully with at least one hand on the bars" to be most relevant.

 

Wooster

 

BTW, traditional method of checking for loose steering bearings is to have friend push/pull front wheel w/bike on center stand, while you place finger under top triple clamp, just where steering head meets clamp, checking for perceptible movement there; wheel bearings check has you trying to rock front wheel w/hands at 12 & 6 o'clock checking for noticable lateral movement, with bike on center stand.

[Harvey_Harrison]

Just had a new Z6 put on the front of my R12RT, and guess what? The 45 mph wobble is gone.

[PhillyFlash]

I have to disagree with most of the ideas, but only based on my own experience. I had the same problem with my 2000 RT, and it turned out that it was not just the tire, but the brand of tire. I had put BT-54's on my RT a few years ago, and loved the feel of them, as many others had, too. That RT got totaled in a very slow speed wreck, with no damage to the wheels. I bought another 2000 RT with very low miles on it (2058) that also had BT-54's. This one had a front end wobble, on both acceleration and deceleration, between 46 and 49 mph, consistently, with hand off the grips. I had kept my wheels and tire from the other RT, so I put them on this one. Same exact problem. We took all the wheels and rebalanced them. Same problem. The dealer tried replacing the telelever. Same problem. Even though I couldn't really feel the wobble with my hands on the grips, the bike just never felt quite as stable, and I didn't have the confidence to push it through the corners. The bike just seemed looser, like I was riding on ice. Went to Torrey, had lots of wear and tear on the rear tire, and ended up riding to Grand Junction with Bynum to get a new tire, MEZ4. Riding back, I found the bike much more stable, but still some front end wobble. When I got home, I changed the front to a MEZ4, and the wobble disappeared. Put the other set of BT-54's on it, and the wobble was back. Got rid of the BT-54's, and 60,000 miles later, I have never had a wobble again.

 

I think that for some reason, even with the exact same year and model bike, different tires seem to have a different feel. You didn't say what tires you have, but I'd suggest trying a different brand. That would be the easiest solution. Of course, if you switch brands and still have the same wobble, something else is probably causing it. For me, the cause of the problem was clear, and the difference in handling the difference between night and day. Good luck.

[chrisstroh]

[then experienced the same thing on the 1150. the shop said is was tire scallop, so i replaced the tire and no wobble. then 10k miles later, another wobble on the rt. replaced the tire thinking that was the fix. but no change: still the same amount of wobble.]

 

 

I'm just a back yard mechanic, but what about the shock? Bad struts will cause cupping on the tire and therefore wobble, just a thought.

Chris