Did you happen to check the wheel alignment before you started using the string or clamped straightedge methods? Just curious. Does the change you made mean that the front wheel is no longer vertical since you shifted only the upper A-arm?

I'm sure this is obvious, but why doesn't moving the contact patch to the right cause even more weight imbalance to the left, worsening the overall problem? I must be missing something.

 

Did you happen to check the wheel alignment before you started using the string or clamped straightedge methods?

No, my experience with the R11RT and a bit of thought about the mechanics/physics gave me sufficient confidence in the likely source of the problem.

Does the change you made mean that the front wheel is no longer vertical since you shifted only the upper A-arm?

That assumes the front wheel was truly vertical before I began. As it is, the change is small and not visually evident.

I'm sure this is obvious, but why doesn't moving the contact patch to the right cause even more weight imbalance to the left, worsening the overall problem? I must be missing something.

With a pull to the left, the CG is not over the thrust line, it is sitting off to the left. (The pull is the result of the moment generated by the offset CG -- a constant force trying to lay the bike over to the left, which the bike responds to by trying to turn to move the thrust line back under the CG. This is why a constant countersteering pressure must be maintained to actually ride in a straight line.)

If the CG is not too far out, you can move the thrust line to align with the CG. For a left pull, you can move the rear wheel to the left relative to the front wheel. Alternatively, you can move the front wheel to the right. With the Duolever, to move the front wheel to the right you can either move the lower A-arm to the right, to the upper A-arm to the left.

Did it fix the problem?

Yep -- if I cared to take the bike apart again (not!) I might add another 1/2 mm shim to 5.5 mm, but it's now close enough that how I load the saddlebags will have a greater effect on whether the bike pulls left or right.

Perhaps your fix, once it's been shared with BMW Motorrad, might result in a TSB so the dealers will correct this for us? One can only hope!

I'd like to think so, but it's not clear to me that they would be willing to pay for the 2-4 hours of shop labor that would be allowed for the job, particularly where the variations in upper A-arm position across different bikes is unknown, and thus there is no way to tell how much shimming is needed for each bike. The trial-and-re-shim approach I used is hardly a cost-effective way to deal with the issue. BMW would need to develop a way to ballpark assess the amount of correction needed before starting on each bike. I could theorize a couple ways, but I'm out of time for typing for now.

 

Being a relative idiot when it comes to wrenching, all I can say is.. wow.

Thanks for the play-by-play. I hope that my bike doesn't have this issue when I finally get it in the next couple of weeks. But, if it does, I'm sure glad you figured out a fix!

 

Color me impressed. Did it fix the problem?

My Goldwing pulled left terrible. It didn't go away untill a forks rebuild with new springs, valving, and ADV disablement.

 

Impressive work Mark - and you explained it really well too. That said, I'm not sure I'm willing to tackle this particular job right at the moment. Perhaps your fix, once it's been shared with BMW Motorrad, might result in a TSB so the dealers will correct this for us? One can only hope!

 

Mark,

It sounds like much more of a job than I am willing to undertake but I might take your post and show it to my dealer to see if he can do something like it.

A couple of things I don't understand are:-

1. If the bike has any means of adjustment to ensure that the wheels are in line.
2. With your fix, the front wheel is presumably not running in a vertical plane any more - how will this affect tyre wear and handling?

 

1. If the bike has any means of adjustment to ensure that the wheels are in line.

None that I am aware of -- from what I can see in the drawings both the front and rear pivots rely on a fixed pivot on one side of the arm, with an adjustable pivot on the other side which is adjustable only to push the arm over against the fixed pivot. If the pivot is the wrong length, the frame is mis-machined, the arm itself is inaccurately dimensioned, whatever, there's no left/right adjustability I see in any of the three primary locations. And given what I had to go to with the shimming, I assure you that I looked for a built-in alternative first!

2. With your fix, the front wheel is presumably not running in a vertical plane any more - how will this affect tyre wear and handling?

That assumes the wheel was aligned in the vertical plane in the first place -- something I have every reason to doubt is the case. These bikes are assembled from parts on the shelf -- whatever their as-delivered dimensions -- with no provision for assembly-line adjustment that I can see (i.e., the line workers install the fixed pivot, install the A-arm, and push it over to the fixed pivot with the right pivot pin). I suspect that the varying levels of left pull are due to stack-up of tolerances in all the parts, and there is no checking of F/R alignment anywhere in the process. If I am correct, I would expect the wheel carrier to be *not* in the vertical plane from the factory more often than straight up and down.

As to tire wear, if anything I expect it to be better, as the front tire is no longer being scrubbed sideways by the constant countersteering required to keep the bike going straight. Handling is still superb; rock solid.

Mine pulls slightly to the left, but it is only noticeable when your hands are off of the handlebars.

Hi, Dan -- I suspect that if your bike "only pulls when the hands are off the bars" it actually pulls 100% of the time, and you are not noticing that you are actually using a constant light amount of countersteering pressure to go straight when you hands are on the bars . In fact, as a matter of machanics and physics, this has to be true -- these conditions cannot, not mutually exist.

Just something to consider on your next ride.

 

Great write up Mark. I am lucky that I do not have this problem, but if I did it would be up to BMW or the dealer to fix it.

 

Mark, Thanks for the amazing detailed research and write up. Mine pulls slightly to the left, but it is only noticeable when your hands are off of the handlebars. It's going to be interesting when I bring it up to the local dealer this Wednesday. They have asked me to write down everything that need to be adjusted!

I'm going to have a copy of your report available.

 

Exceptional and very hard work! Exceptional explanation! Excepcional working mind! Many, many thanks!

 

I took my GTL to the dealer in Daytona yesterday, described the issue and provided them with your write-up. They verified the pull to the left with my bike and also with a brand new GTL on the show-room floor. With that they filed an email report to BMW and we are awaiting a response. I will keep you updated on the result.

 

Don't know about the US but in the UK such a modification would be classed as a significant modification from manufacturers specification and would require notification to and approval by your insurer, at the risk of invalidating the cover if not approved. Assuming of course they could find the mod after any claim!

 

Which is why I left Old Blighty and moved to the Colonies.

 

My GTL is dead nuts on money no pull but if it did pull that would be BMW,s problem.

 

I agree -- but what do you do when you're told by a BMW Rep (as I was in 1999): "The bike pulls to the right when you take your hands off the handlebars -- don't take your hands off the handlebars"??? The old BMWNA washed their hands of it, i.e., it "wasn't a problem" so no effort to fix was forthcoming. Hopefully today's BMWNA will be more responsive/proactive with BMWAG to address the growing number of complaints on this.

 

I wonder if the brand of tires has anything to do with the pulling left. I don't know how to set up a poll, but it would be interesting to see the brand of tires used by those with the left pull.

 

I wonder if the brand of tires has anything to do with the pulling left. I don't know how to set up a poll, but it would be interesting to see the brand of tires used by those with the left pull.

I had assumed everyone had Z8's -- anyone have something different?

 

My GTL has Bridgestones and it pulls to the left.

 

Mine has Bridgestones and it pull to the left too.

 

My GTL has Bridgestones and it pulls to the left.

 

Metzeler straight as an arrow!

 

Thank you for taking the time to post such a thorough write-up. Much appreciated.

My 1600 GT at a month old and now 3,800 miles has just the same 'left hand pull'. It never seemed quite right from day one and an extended jaunt into France has confirmed it..... it pulls to the left, period.

I dropped the bike off at a large central London dealer's on Tuesday for them to have a look at. Yup, they have confirmed it, too. They have also now replicated the same leftwards pull on:

(a) Their demo bike

(b) A brand new machine, with zero miles, fresh out of the crate

Bike (b) at least negated the possible effect of tyre wear and / or something untoward having happened to either my bike or their demo over the proceeding five or so weeks. It also confirmed that it must be present 'from new' ie. an assembly / manufacturing / design problem of some sort.

So, that is three new or newish bikes, all with the exact same problem which cannot be simple coincidence.

The dealer has flagged the issue with BMW (UK) via the official chanels, so let's see what happens next.

In the meantime, it's a great bike..... despite the pull and the USB glitch.... not least as at makes petrol, if the average MPG readout is to be believed....

PS Tyres are Metzlers, if anyone is vaguely interested.

 

You are the first with Metzlers to report the left pull.

 

Metzlers; weak pull to left (as previously described in this thread).

 

I have Metzlers and my bike has a slight pull to the left.

 

Pretty much confirms my initial thought that this is tire-independent.

A brief follow-up: Over the past week I noticed that there was a slight amount of indefiniteness building in the steering, which was not a surprise and has now been addressed.

When I did the original shimming work, I was *very* light on the torque applied to the pivot pin 5, as I preferred to err on the side of too little pre-loading of the bearings than too much, knowing I could always go back in and tighten down more if needed.

That is exactly what I had to do -- after a few days of getting beaten up by Wash., DC potholes, the suspension settled with just a little bit of slack at the left end of the upper arm. After going back in and snugging the pivot pin down a bit more, after two day's further commuting it appears everything is back to as tight as it should be.

One additional thought: Don't be put off by the apparent complexity of the bike if you want to do under-the-skin work -- the K16 is definitely easier to get the tank off than a K12LT.

Having now done it a couple times, on this go-round I had the tank sitting on the ground a hair over 20 minutes after starting to remove the tupperware. The total time for the work, including the time to adjust the pivot and do a bit of other work (zip-tie a wire in a couple places, chase the threads of a hole in the magnesium fairing carrier, etc.), was a little over 1 3/4 hr from the time I removed the first screw to the time the last screw was back in.

 

My bike came with the Metzlers and it pull left
Gene

 

Metzlers, left pull.

But... I've almost sorted it by transferring the tool bag from the left to the right pannier, and adjusting my seating position. I've been looking through the left of the screen inverted "V", but by making a conscious effort to be in the middle of the seat and thus lined up with the "V", I can ride 'hands off' without a problem

 

Metzlers....left pull. Bike #2 pulls to the left a lot less than bike #1. I can actually keep it upright with enough body "english" towards the right side. So, I'll register the issue with BMWNA and see if we can prod them into a fix.

Folks, I can't stress enough that everyone that has a pull to the left, no matter how slight, needs to log the issue with their dealer AND call BMWNA (800-831-1117) to report the problem. Make sure the BMWNA folks get your VIN number and log the issue against it. If nothing else, they may correct it for future buyers.

 

Pull

Slight pull to the left here too; can manage easily by shifting my weight. Metzeler Z8s. I plan on changing from the Z8s to PR3s in the next 2,000-3,000 miles (I am at ~3,900 miles now). Doubt that'll change the pull, but I keep an open mind

Dealer is aware, and a report (PUMA) was sent.

 

Great Work

A truly magnificent piece of work Mark, but perhaps like others, wonder why it should (not is) be happening in the first place? 5.5 mm of shims is a significant amount of adjustment, which concerns me even more why some adjustment has not been built in the bike (notice I didn't know how that adjustment would be designed). Also, what kind of poor engineering or manufacturing job tolerates a 5.5 mm margin of error? I may never take my hands off of the bars again because I can see my tendencies toward OC immediately trying to determine if road camber, alignment, tires, etc.

 

but perhaps like others, wonder why it should (not is) be happening in the first place?

No comment (other than to note that it is likely lower cost to procure one fixed pivot than a separate pivot pin and lock nut, and lower cost to assemble as no fitting/adjusting is required).

5.5 mm of shims is a significant amount of adjustment

no argument (a little less than a 1/4", the installed stack height is probably a hair under 5 mm).

(notice I didn't know how that adjustment would be designed).

Easily done, with existing parts (assuming the rlght and left angular contact ball bearings have the same inner diameter): replace the fixed left pivot bolt with the right side's pivot pin and lock nut -- note: this assumes the thread diameter of the left fixed pivot and the right pivot pin are the same, which is how I recall things; if not, it is still relatively simple to do -- either: (i) a small change to the frame machining (the left frame ear would have to be drilled/threaded to the smaller right pivot pin's size); or (ii) for field modification/repairs, installing a diameter-reducing threaded sleeve in the frame's left pivot ear.

Also, what kind of poor engineering or manufacturing job tolerates a 5.5 mm margin of error?

I suspect there's a bit of expectation that the parts will be sufficiently precisely made so that the actual vehicles will all match the design, so there would be no need for adjustment (a justification for designing in this way could be pressure to reduce assembly costs, i.e., if everything is made right, we can eliminate an adjustment step in assembly). The trouble is, of course, that there is no tolerance for error in such a design.


Of course, all this may be completely wrong, and the bike is perfectly designed -- if my bike's front end was somehow damaged (it's currently in for loose upper ball joint replacement, which implies damage), then there's an explanation which does not require our casting aspersions on BMW's engineering prowess.