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Instability on highway over 75mph


bobdc

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New RT owner. Got my bike 3 weeks ago and love it. Have been riding for years, Harleys and Hondas. Sport bikes and cruisers. Very happy with the bike, but with about 1100 miles on the bike, I find I am being tossed about on the highway at high speed. Further, the front end feels very light at speed, as though the front wheel was wondering between the fork legs(everything visibly looks OK). Although I wouldn't call it severe, it can be somewhat disconcerting at times. Anyone have any thoughts? Has anyone experienced the same thing? Did it go away over time?

 

The dealer is telling me that maybe the tires need more scrubbing in, and that this may take a couple/few thousand miles to get better. They also reminded how light the bike is, and that this would also contribute to some of the consequences of wind and turbulence from trucks on the highway.

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cannot say I have noticed this myself but my bike was purchased with 2k on the clock (now 6k). What tyres are on the bike? Mine are BT020's. I have heard it said that all the forward facing parts of the rt are pointed downward including the panniers, and that this creates a downforce effect at speed? I've had my bike up to 3 figures without ill effect but it was on a calmish day. I find large vans worse than lorries.

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I have a 12RT with 14K+ on the odometer. I run 38 psi front and 40 psi rear solo. Whenever I'm in traffic at freeway speeds, 65-80 mph, the bike moves around quite a bit due to wind turbulance. As soon as I get into clear air it settles down. If you are used to a heavier cruiser style bike it is a little disconcerting until you get used to it.

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ShovelStrokeEd

One need only look at the RT from both head on and in profile to realize that aerodymanic preference has been given to rider protection rather than to stability in turbulent or semi-turbulent air. The bike is/was designed in Europe where typically, following distances at speed are much different than they are over here. They have the sense to keep away and keep right, and, as I recall, they don't allow their big trucks to run as fast as we do here.

 

Now add an upright riding position and relativly wide bars such that any wind that reaches your shoulders/upper body, unless you are really relaxed on the bars, gets translated into a rider input and you have the formula for some wiggles and nervous feeling.

 

Back when I rode big touring bikes, I would notice the same kind of thing. Increase your following distance a bit, relax on the bars and just let the bike do its thing. It won't do anything evil, just dance around a bit.

 

That said, I don't envy anybody who has to ride one of those in severe, gusting cross winds.

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The steering was quickened on the 1200RT which results in improved slow-speed handling, but as a natural consequence also results in somewhat less stable high speed operation than the earlier bikes. Suspensions settings are always a compromise, you pays your money and you makes your choice...

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What Ed said...

 

When I got my RT I felt the same way...it never gets better you just get used to it....The telelever front end is part of what your feeling it's not as stable as the other bikes you mentioned...also if you have the ESA system try cranking all the way up to two passengers and sport..it may get a little better....if you don't have the ESA stiffen up everything you can....and then you may want to get ready to buy some better shocks....I don't think the ESA will allow you to add enough damping....I really don't know about the non ESA bikes...

 

Good Luck

Whip

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I have no problems with stability while cruising at 120km/hr. I find the R1200RT far superior in this respect to the R1100RT.

 

Following other vehicles too close will result in buffeting as you a riding in the dirty air from the front vehicle. This dirty air will adversely affect the aerodyamics of the motrocycle.

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I'm not on an R12RT however, this has been an issue for many on the R12GS.

 

In addition to what others have suggested, be sure your tire pressures are correct for the RT and most importantly, when faced with a lot of turbulence from large vehicles or strong cross-winds, be careful to not apply your death-grip to the bars. You need to relax -- big time. The bike needs to be able to move around a bit and if you're fighting it, you will wear yourself out and will make the feeling worse than it really is.

 

You will get used to it.

 

Now, go out and find lots of big trucks and practice at, oh, let's say, around 80mph! wink.gif

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I have found the R12RT to be quite stable at speed.

You should try following trucks at 80mph an a Kawasaki Concours with a large Givi trunk! Mind you the turbulance behind large trucks will upset most bikes, maybe 1000lb tourers fair better but I'm not old enough for one of those yet!

I have found that riding without the trunk makes the bike much more stable behind those trucks (the connie was a totally different bike without the trunk).

You did not mention if you have a trunk or not. If you do leave it at home if you don't need the room.

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Some do it, some don't. I've never been able to find out the reason why.

 

Mine does it. Suspension settings, tyre pressures, whether the fuel is full or empty, how you are riding that day and different tyres can all affect it.

 

But there are still some that do it and some that don't! confused.gif

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Thanks all for the input. Putting all the thoughts together from experienced RT riders really helps.

 

Bottom line; I need to ride more and get used it! Of course riding more is a good thing!

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Once I experienced this feeling on my '98 R1100RT after a tire change. After putting more miles on, the front tire started to shed rubber and what was underneath obviously had hardened too much in the manufacturing process.

Long story short...there was almost no visible sign of a tire defect, but the front tire had a manufacturing defect of some kind and suddenly changed my extremely stable bike into one that drifted and just didn't feel right. If I hadn't noticed the slight shedding of rubber and looked farther I would never have known what was causing the instability.

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For what it is worth, I found the R1200RT a total different highway animal than the 1150.. the R1200

 

1) the overall position of the bike and rider are higher

 

2) the body panels on the R1200 are not as "integrated" for wind/turbulence than the 1150

 

3) the pre-load on the shocks is more important on the R1200 than the 1150.

 

4) the size of the top rear bag does matter

 

Basically, it boiled down to this with me.

 

I was used to riding my 1150 anywhere at anytime with all the boxes.. whether or not they were full or empty.

 

On my R1200, after adjusting the pre-load, if I am running empty side boxes, I take them off intentionally.. I do not run my R1200 around town with empty boxes, since if I go up to highway speeds and a cross wind the R1200 with empty boxes will get sketchy.

 

If I have a passenger, I can ride with empty side boxes no problem.

 

I do have the large top rear box, and I do keep that on full or empty (great box for my XXXL helmet).

 

Loaded boxes, with or without a passenger, I have no problem.

 

Next week I am going to bar setbacks (Surburban Machinery) as well as lowered rider pegs - my choice at 30" inseam to be more comfortable.

 

This is the 1st BMW I have owned where I have considered lowered Ohlins for long term comfort, I will settle that debate in my head after I have some miles on the setback bars and new lowered pegs.

 

RT's.... 1100-1150 then the 1200... the 1200 a WHOLE different animal..

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Fabbrisd makes a good point about the boxes. I personally don't notice a great deal of difference with/without the panniers. But the (large) top box when on and riding solo is VERY prone to turbulence from lorries, etc. Consequently I never put it on except when the load demands it or if I am riding 2 up.

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Richard_Spag

My RT has always been prone to instability at higher speeds. I found that two approaches have brought things to an acceptable level of stability. 1) don't adopt a "death grip" on the bars at speed, just relax and let the geometry take over, 2) increase the rear reload and damping. My RT's stability has improved since it passed the 20,000 mile mark - so perhaps it is also a case of the suspension bedding in / wearing out that improves things also! grin.gif

 

Cheers

 

Richard

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My RT wiggles at high speed also (100+) but not something I'm concerned about. I feel it, but it doesn't really bother me.

 

The Honda also wiggles, (120+). It really doesn't like "dirty wind" and I'd say it wiggles more then the RT.

 

Severity of the wiggle is affected by the position of the wind screen. A high screen will affect the Honda around 85 mph, as does truck turbulence.

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The first thing I noticed--apart from the difference in the power/weight ratio--when I traded my R11RT for an R12ST was the difference in buffeting. The RT presents a fairly large "sail," especially for its weight, so you're going to be more affected by crosswinds and buffeting from other vehicles.

 

That said, it's worth playing around with your suspension and tire pressure settings (within manufacturer's limits, of course). In my admittedly limited experience with the previous-generation RT, too much preload seemed to exacerbate the problem. Dialing it down a bit seemed to help.

 

Also, though I've never felt this was a problem, some folks feel that BMW's telelever front suspension delivers less road feel, the "light" feeling you were describing. This is something that will remain a constant, but you'll ultimately find that the RT has great handling, good compliance, and high levels of adhesion. It's a different feeling, but one that you'll come to trust.

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I am curious if anyone else has tried both a CeeBailey and Aeroflow windshield and how they think the two shields affected stability at speed. I have a medium height Aeroflow and a CeeBailey +3 and I think the CeeBailey shield provides more wind protection but affects the bikes stability at speed much more that the Aeroflow. Especially when in the wind turbulance behind a semi truck it seems the bike moves around considerably more with the CeeBaily. Have any of you noticed the same thing or is it just my imagination?

 

 

Dan Forker

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Dan, to address your question about windscreens...I have the Ztechic on my RT and am very happy with it. I have tried all others on 'other' bikes with mostly mixed results.

 

The handling issue on the RT is pretty much as described by others above, much to my suprise as I didn't expect this on the 12RT as NOT ONE of the many many reviews nor any threads on this forum suggested there could be an issue here. So I bought the bike, trailered it to Daytona, climbed on with 2kms on the clock and was promply subjected to the laughing and pointing by my fellow riders who just couldn't believe how I was wobbling around behind the heavy traffic on the superslab. I was not impressed. Called BMW Canada who of course had never heard of such a thing. They suggested I relax my grip...after 43 years of riding, (4 yrs of track time...) I didn't need to hear that as a solution.

 

All suggestions above are valid. I have Metzler Z6's which seem to be a big part of the problem until they have about 2,000kms on them. Of course the big top case, one up, is a REALLY BAD thing. Loaded on not. I run 41 psi front and 42 rear, helps. The 2 'helmets' showing on the preload and 'sport' on the ESA also helps.

 

I am thinking Coni Sport Attacks next...

 

Jim

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Funny I should read this thread today.

 

Just came back from the weekly trip to the other side of the state and coming back, I decided to "let her rip" and wicked it on up to 130 mph while dicing with a Lamborghini something or other. It was a beautiful car for sure and we were just having quite a good time at these speeds for at least 20 minutes on the quieter part of Alligator Alley.

 

I never notice any particular instability with the R12T and was running with the windscreen about a third of the way up. Stock Michelin Road Pilots for the tires. Normal for the suspension and "rider/luggage" for the rear. No tour pack but both stock side bags were on.

 

Granted, I don't particularly approved of these types of speeds, but I did notice that the bike really smoothed out above 110 mph.

 

When I left the interstate at my exit, both me and the Lambo waved at each other saying "thanks" for the temporary good time.

 

AD

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I trade off between the CeeBaily 2+2 windscreen and stock. Except for gas milage, no noticable difference in handling. My 05 R1200RT has been one of the most STABLE bikes I ever had - and at any speed. This bike is extremely stable, never had a wobble or even a loose front end with either stock or 2+2 windscreens. This includes up to 130 (just once) to shut my brother up on his Honda. Passing trucks, cars, in wind, or in on-coming traffic, this bike has instilled in me new security in regards to predictability and stability. Don't mean to sound like an advertisement but I think this thread only has people with problem bikes responding? Of the people I run with that also have R1200RTs, they pretty well share my sentiment. Great bike, though I think the rubber mounting the handlebars would be a great last touch to finish a good bike.

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In my books the RT is a great handling bike and I have never had a moments thought about it being unstable at any speed. When I think its safe to do so I often cruise for extended periods at 140 to 160kph (about 80 to 100 mph). I can't say I have ever felt the bike was unstable. You will always get buffeting on a bike at times but in my books the RT handles it all very well.

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In my books the RT is a great handling bike and I have never had a moments thought about it being unstable at any speed ... ... I can't say I have ever felt the bike was unstable. You will always get buffeting on a bike at times but in my books the RT handles it all very well.

 

I'll agree when the air is still the bike is handling great at any speed to red-line in 6th. As the tires wear in, the nervous jumping around in turbulent air has mostly gone away (plus I have got used to it). On my initial 700km break-in ride I was so surprised by the jumpiness of the RT in turbulent air from a cube-van ahead next lane over - at 90kmh (55mph) - I pulled off the road to see if I had a flat. JAKFROST's describes it well in his post here http://bmwsporttouring.com/ubbthreads/showflat.php/Cat/0/Number/729723/page/0/fpart/4/vc/1

 

Now with 4000km on the Michelin Pilots (I run 32/26 psi with ESA set for normal/sport 1-helmet, no topcase, bags on all the time) I don't even think about it. Prior bike was the 99R1100S (on Michelin Pilots) and nothing knocked it silly, ever, so any comments about Telever or stock shocks causing this are BS.

 

Soon as the RT's Pilots are done I'm switching to Conti Attacks based on the reports here and elsewhere. Hope the nervous jumping around does not start all over until the tires bed in.

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Well I'm really happy for Tom and Andrew who report their bikes are rock solid at all speeds, in all configurations and under all conditions.

 

BUT this only furthers the concern...why are some bikes so loose and some not.

 

The reason for the discussion is, in my view, to see if there is a common thread which could lead to a resolution of the problem for those of us so unlucky as to own a 'loose' bike...

 

I am still thinking it is a tire issue, but until I wear out the new Z6 and try something else I won't know for sure.

 

Jim

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My '06 RT has the Z6's and I only really notice handling issuses when I have the top box on and no passanger or when I hit a tar strip on the road. I do get some buffeting when I'm behind a minivan but if you let up on the grip or backoff it goes away.

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It seems to be a variation between bikes not tyres.

 

I agree with the above - instability is probably a strong word but some bikes certainly "notice" turbulence, etc more than others. And it would be good to know why.

 

It seems bizarre because as far as I can tell it is an aerodynamic issue.

 

I rode a loan bike from my local dealer the other day. It was an identical specification in every respect to my own bike even down to the tyres and colour. I also checked that tyre pressures were identical. I rode them back to back. Mine moved around (a bit; its not scary) the other was rock solid. Odd.

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My '06 RT has the Z6's and I only really notice handling issuses when I have the top box on and no passanger or when I hit a tar strip on the road. I do get some buffeting when I'm behind a minivan but if you let up on the grip or backoff it goes away.

Same here, 06 with Z6s, 11,000kms and I find it very stable. No top box and always solo, although I just did a 1500km trip with my son on the back and again rock solid. I too notice the Z6s don't like the tar snakes either, I never even noticed the tar snakes on my meanstreak with Bridgestone Excedra's but I get a definite slipping out on the RT, otherwise no complaints at speed or in the wind. I run my tires at 36/42.

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It seems to be a variation between bikes not tyres.

 

I agree with the above ... but some bikes certainly "notice" turbulence, etc more than others. And it would be good to know why.

 

I rode a loan bike from my local dealer the other day. It was an identical specification in every respect to my own bike even down to the tyres and colour. I also checked that tyre pressures were identical. I rode them back to back. Mine moved around (a bit; its not scary) the other was rock solid. Odd.

I agree - response in turbulent air seems to be bike releated. 05 Dealer demo I rode before buying was rock solid. Same tyres, ESA... Got my 06 and it moved around so much the first day I took it back to have them check everything was tight. Just had the bike taken into many pieces and reassembled for the clutch recall. Haven't had enough ride yet to see if anything is better or worse. I'll report when I know more

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42psi front seems awfully high. I run with 36 psi in the front and have no stability problems even with Z6's.

Didn't like the Z6's though and have replaced them with BT020's.

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It seems to be a variation between bikes not tyres.

 

I agree with the above ... but some bikes certainly "notice" turbulence, etc more than others. And it would be good to know why.

 

I rode a loan bike from my local dealer the other day. It was an identical specification in every respect to my own bike even down to the tyres and colour. I also checked that tyre pressures were identical. I rode them back to back. Mine moved around (a bit; its not scary) the other was rock solid. Odd.

I agree - response in turbulent air seems to be bike releated. 05 Dealer demo I rode before buying was rock solid. Same tyres, ESA... Got my 06 and it moved around so much the first day I took it back to have them check everything was tight. Just had the bike taken into many pieces and reassembled for the clutch recall. Haven't had enough ride yet to see if anything is better or worse. I'll report when I know more

I'd be seriously suprised if there were any real difference between two comparably prepared R12RT's under similar air turbulence conditions. I believe if you noted the conditions, you would see a high correlation between air turbulence and bike "wobble."

 

All recent RT's (last ten years) have a lot of "sail" area on each side of the bike, making them more sensitive to buffeting in turbulent air - like right behind an eighteen-wheeler. They also can be a handful in gusty cross-winds, but the R12 doesn't seem as sensitive as earlier versions. I remember my R11RT being much worse when running behind semis and other large trucks, but the feeling is very similar on either bike.

 

I'm curious to hear how the new K12GT's are in turbulence. They also seem to have a lot of lateral surface area. I would expect them to have some of the same manners in dirty air.

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I'd be seriously suprised if there were any real difference between two comparably prepared R12RT's under similar air turbulence conditions. I believe if you noted the conditions, you would see a high correlation between air turbulence and bike "wobble."

 

I am surprised too but the comparisons I have done have been as scientific as possible. Within 1/2 hour of each other, over the same roads, in the same weather conditions, same traffic conditions, same speeds, following at the same distances, etc.

 

Clearly the conditions at any time have a greater or lesser effect (crosswinds, size & speed of trucks, top box on or not, riding speed; all of which make me think this is inherently an aerodynamic issue) but there is a clear difference between some bikes in as near identical conditions as possible. Mustn't let this get out of proportion - I'm not talking of something dangerous but more a feeling of "uncertainty".

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I suspect the stock windscreen has much to do with the bikes instability. To me it always felt like the bike was being buffeted on the highway at speed, especially by semis and buses, the buffeting could be felt several semi or bus lengths behind the offending vehicle.

Several months ago I installed a Ztechnik screen on my 1200 RT, and I notice the bike is much less affected at speed by the above referenced vehicles, while not totally gone, there is a marked difference between the stock and replacement screen. The wind blast in the face from the stock screen in the down position is also totally reduced. I always rode with the stock screen up on the highway to prevent being beat up up the wind blast from the windscreen in the down position.

 

Just my 2 cents worth.

Fran

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Not that 1 psi makes any difference...I try to keep the front at 40-41. It is a result of many attempts to mitigate the inherent instability that seems to plague my particular bike, (and a few others...). The increased psi is a trade off between cornering ability and straight line stability.

 

Since the majority of my riding is pretty much straight up, 70% slab, solo with top case, (my commute requires the storage space and hey, it comes from BMW as a factory accessory for christs sake!!), I am willing to accept the loss in the last 2% of my cornering ability.

 

The bright side is by running the higher pressure after 14,500kms there is no sign of the dreaded 'cupping' tongue.gif.

 

Jim

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ShovelStrokeEd

One of the keys here is - solo with top case.

 

Pay a bit of attention to how the air is moving around you at speed. You will find that the air wants to close up and fill the gap between you and the top case. You can usually feel this as a bit of forward pressure on your back or breeze blowing up the back of your riding jacket.

 

That air is extremely turbulent. Now, give it something to push against, like a large top case, and it gains leverage and wants to move the bike around. Add a large truck, whose wake turbulance can easily extend 100 feet behind the truck at speed and things just worsen.

 

To those who ride solo with top case, try it with a passenger or a large duffel strpped across the pillion seat. You'll find the bike to be much more stable. Strange, huh? Not really, it is just aerodynamics coming into play.

 

My Blackbird is a really slippery beast. It has to be to attain near 180 mph top speeds with only 140 or so RWHP. When I mount my Givi E460 top case it becomes sensitive to wake turbulance and will wiggle a little bit if I approach a large truck too closely. When on a trip, I often use a waterproof duffel with my overnight necessities in there so I don't have to do much carrying of luggage into the hotel. With the bag strapped on across the pillion, the instabilty is greatly reduced. Don't mean to call anyone's pillion passenger a bag, but the effect is the same. grin.gif

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42psi front seems awfully high. I run with 36 psi in the front and have no stability problems even with Z6's.

Didn't like the Z6's though and have replaced them with BT020's.

 

According to the Metzeler fitment chart for Z6s on the R12RT, they recommend 36 (2.5 bar) front and 42 (2.9 bar)rear.

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Now with 4000km on the Michelin Pilots (I run 32/26 psi with ESA set for normal/sport 1-helmet, no topcase, bags on all the time) I don't even think about it. Prior bike was the 99R1100S (on Michelin Pilots) and nothing knocked it silly, ever, so any comments about Telever or stock shocks causing this are BS.

 

you must be kidding about pressure so low, do you mean 3.2 and 2.6 ATU?

 

I was told 38/42 PSI should be right.

 

And to the original question I find the bike stable but it still does at times take turbulence in an odd way.

 

h

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ShovelStrokeEd

Unfortunate that you can't just slack the jib sheet, or in this case spinnaker, to compensate for the gusts.

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Now with 4000km on the Michelin Pilots (I run 32/26 psi with ESA set for normal/sport 1-helmet, no topcase, bags on all the time)....

 

you must be kidding about pressure so low, do you mean 3.2 and 2.6 ATU?

 

I was told 38/42 PSI should be right.

 

oops

I meant 32/36. Right out of the manual (2.2/2.5bar) for one-up. 36/42 (2.5/2.9bar) for two-up or when I load the bags with more than my briefcase,

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