R1100RT Pull To The Right

[Joe Frickin' Friday]

Late to the discussion here, but nrp and dirtrider are absolutely correct: assuming constant RPM, driveline torque is not at all responsible for PTTR.

 

Only the component of engine torque used to accelerate the flywheel and other driveline elements will show as a roll moment to the M/C chassis. This torque will be much less than the rated torque of the engine.

 

A special circumstance (which is still consistent with your first sentence):

Suppose we have the transmission in neutral and snap the throttle wide-open. Then the full torque of the engine is accelerating the crank/flywheel, and an equal/opposite reaction torque would be directed toward leaning the bike to the right. If the bike is in motion it will tend to initiate a right turn; if stopped, the rider would have to resist this with his right foot (or lean the bike to the left). In practice, the engine revs up to redline so rapidly that there isn't really time to develop that turn (or feel much of that effect in your right foot if stopped).

 

 

[dirtrider]

Afternoon Roger

 

No valid idea why the 1100/1150 went to market with the weight offset. I seriously doubt that it was originally designed that way or that the engineering department just screwed up. My guess it was a last minute forced issue.

 

I work in engineering for a motor company & have seen lots & lots of vehicles go to market with issues that were not originally designed in or that engineering fully approved of.

 

Marketing & financial basically rules the roost when it comes to what goes out the door as the end product.

 

Who knows on the BMW boxers. Maybe a last minute demand by marketing to get an extra gallon of gasoline in the thing to meet competition of similar vehicles.

 

I doubt that rear wheel to final drive was originally designed with that spacer so that might have been a last minute thing to get tire clearance for all tires in the size range available aftermarket. Or to prevent possible tire rub if the final drive spool position went to max stack-up in the wrong direction. Or maybe to prevent tire rub if the swing arm casting grew to max dimensions.

 

Obviously there is a possible (& known to BMW) stack up issue in the rear wheel/final drive areas as the rear wheel has a +/- 9mm lateral variance & still be within specifications.(so much for precise)

 

I'm sure engineering had to (or were forced to) OK any last minute changes but as long as it was safe to ride & stopped in a straight line they (engineering) probably reluctantly bought off on the changes. (Been there many times myself)

 

[roger 04 rt]

JFF,

 

I was the hold-out on the possibility that there was lateral axis torque ... but it only took me about 24 hrs. and some spoon feeding to see very clearly that the only lateral moments were from changes to rotational inertia (i.e. snapping the throttle) in the front to rear axis.

 

DR et al,

Since the bike has a longitudinal center of mass that is right of center due mainly to the fuel loading, the question becomes what to do about that. I see three choices.

 

1) Leave it like it is: Understand that it's the case and ride and enjoy the bike. It only takes about a 0.5 degree of lean which I don't even feel. The usual method of supporting a motorcycle at a stop light is with the right foot on the brake and the left foot down. Perhaps a right-hand bias is a good thing.

 

2) Rebalance the load: Put 50% of the unbalanced weight on the right hand side such that with a full tank the weight bias is, say, 10 lbs. to the right, and then near empty, there is a 10 pound bias to the left. But who wants to add weight to the bike, and ideally it would be laterally opposite the fuel not in the rear case.

 

3) Offset the rear wheel: Create a driveline bias that reduces the 0.5 degree lean to a 0.25 right lean with full tank and a 0.25 degree left bias at near empty tank.

 

All things considered wouldn't the handling be more predictable with a zero to 0.5 degree lean?

 

 

[Joe Frickin' Friday]

1) Leave it like it is: Understand that it's the case and ride and enjoy the bike. It only takes about a 0.5 degree of lean which I don't even feel. The usual method of supporting a motorcycle at a stop light is with the right foot on the brake and the left foot down. Perhaps a right-hand bias is a good thing.

 

The chief complaint regarding PTTR was the constant corrective force one had to apply to the handlebars to travel in a straight line. Not a major issue on a jaunt through the twisties, but when trying to cover 500+ miles in a day, some of us ended up with a sore shoulder.

 

 

[dirtrider]

Afternoon Roger

 

Personally I have visited most all of what you have suggested with past 1100/1150RT boxers. The final cure was to buy 1200 hexheads.

 

The PTTR never bothered me for local riding or even for spirited riding. I did have one old 1100 that had severe PTTR & on that I moved the rear wheel as well as put all my tools, jumper cables, & tire repair stuff as far left as possible. Even that bike didn't bother me too much while riding (mostly commuting) but seeing as it was a commuter bike I seemed to always be using my two hands off the bars to zip up my jacket, fool with my helmet, or change gloves, or dig something out of my tank bag. To do that I had to almost sit side saddle to keep the bike from going right.

 

Otherwise the only time PTTR really bothered me was on long trips where I occasionally like to ride no hands on bars to relax & change up my riding position, or get a drink, etc. It is difficult to move left on the seat or stick your left knee way out at 90mph to keep the bike in-lane.

 

[breyfogle]

After we settle PTTR, can we open a thread on "Is counter steering real?

[Paul Mihalka]

Just a quick rehash of what I did on my R1100RT with significant PTTR. First a note: You can remove the shim between wheel and rear drive without touching brake stuff. The disk and ABS sensor is attached to the rear drive and not to the wheel.

So: First step, remove the shim between wheel and rear drive. I have not read any good explanation why that shim is there anyways. Some improvement of PTTR, but still there. Next: Remove right hand swing arm pivot bolt and reinstall with a 2mm shim/washer. 2mm is max, with more you cannot adjust enough the bearing play. After the 2mm shim installed, adjust the play with the left hand pivot bolt. With this adjustment on that bike PTTR was completely gone, and the front tire wore even and not excessive on the left. Sold the bike with 175K, no problems.

 

[roger 04 rt]

So the relocation of the rear wheel to the right, if I'm understanding you correctly results in the frame and front wheel running in its original track and alignment and the rear wheel running in an offset-to-the-right parallel-to-the-direction-of-front-wheel's-travel alignment. Before running the numbers for myself I want to make sure I've got it right.

 

If that's correct, among other things, it has the effect of moving the center of mass of the motorcycle to the left of the rear wheel.

[dirtrider]

Afternoon Roger

 

Maybe yes maybe no, depends. Might just move it to center behind the front.

 

Nominal rear wheel position is +3.5mm (or 3.5mm right of center).

 

But there is an acceptable (per BMW anyway) +/- 9mm position variance (from that nominal +3.5mm).

 

So if it (rear wheel) is now 5.5mm left of center & you move it 5mm right it will still be .5mm left of center.

 

Get a couple of long straight bars (8' florescent tubes work good) then check the rear track vs front wheel.(don't forget the tire/rim width difference). Some use a couple of strings but I haven't found that to be nearly as accurate as long straight bars.

 

[dirtrider]

Afternoon Roger

 

Something I always wanted to do but never got around to was to strap the front wheel in the straight ahead position.

 

Then place an inclinometer on the bike the lean it over 5° with a pull scale hooked to the frame (parallel to the ground) in the seat area. (use the scale to allow the bike to lean)

 

Was always curious as to what the difference in 5°lean weight was between 5° right vs 5° left lean.

 

[roger 04 rt]

Pardon me for a moment while I become boring.

 

--Estimating that the right-side offset weight of the fuel is 20 lbs. with a full tank and 0 lbs. with an empty tank. The best you can hope to achieve is 10 lbs right with a full tank and 10 lbs. left with an empty tank.

 

--To achieve that you need 5 lbs. taken from the right side moved to the left side for a 10 lb. bias to the left.

 

--Estimating the weight of the motorcycle and rider at 800 lbs. distributed over roughly 200 mm left and right of center. Which results in a lateral weight of 2 lbs. per mm.

 

--going back to that 5 lbs. to be moved, it takes a shift then of 2.5 mm of the entire centerline to the right.

 

--Each 1 mm the rear wheel is moved right, shifts the effective centerline 0.5 mm (triangular line movement).

 

--Therefore, in my back of the napkin calculation, every 1mm rear wheel shift right moves 1 lb. to the left. We want 5 lbs., so we need the rear wheel 5 mm right of center in this example I've just made up.

 

So to me it looks as if BMW (who has the real weight and balance data as opposed to what I've estimated) offset the rear wheel by the 3.5 mm to half offset the fuel imbalance.

 

Unfortunately the +- 9 mm tolerance might lead to 18 lbs. shifting side to side which creates a 36 lb. weight differential. Yikes.

 

[tallman]

So, on my GT the front wheel is offset an inch to the left because...

[dirtrider]

Evening Roger

 

A couple of points-

 

The rider sits behind the fore/aft centerline so moving the rear wheel gets more weight shift per mm of movement than averaged.

 

There is more to the weight offset than just gasoline in that tank wing. The majority of the internal transmission weight is right of center (see pix)

 

 

[roger 04 rt]

So, on my GT the front wheel is offset an inch to the left because...

 

Because you had a crash? Seriously, what GT, and is it really an inch?

 

Evening Roger

 

A couple of points-

 

The rider sits behind the fore/aft centerline so moving the rear wheel gets more weight shift per mm of movement than averaged.

 

There is more to the weight offset than just gasoline in that tank wing. The majority of the internal transmission weight is right of center (see pix)

 

 

 

DR,

That's a fair point but as you know the moment arm is weight time distance from the center line and even if the gears are heavy they're only a few inches off center. Not saying they're not there, but my Kentucky-windage estimate put the transmission vs exhaust and starter at about a quarter of the fuel moment. The fuel is relatively heavy and 9 inches or so off center. Btw, how much do you think a gear stack weighs?

 

(A rough estimate looks like if the battery (15 lbs?) were mounted in the radio box there would be a good counter to half the fuel.)

 

The longitudinal aspect of weight distribution counts too as you said and accounts for some of the in accuracy of measurement.

 

What surprised me really was how much 5 mm could do to the lateral balance calculation. The numbers being used, mms here and there seem surprisingly close to my rudimentary model above.

 

These calculations are not so different from fore-aft weight and balance calculations. There you can take off with CG forward of the wing and land with the CG almost in the back seat. There, you run out of elevator travel and the main wing stalls--not pretty.

 

Regarding the weight at the handle bars for 5 degree left and right lean. I figured the force to be about 50 lbs. nominally. Then if you add a 20 lb. fuel imbalance I get a 8 lb. addition leaned right and an 8 lb. subtraction on the left lean. Those numbers were before accounting for wheel offset.

 

Anyway, I try the calculations to see if the explanations stand the test of putting numbers to them. At first blush a few mm of rear wheel offset might not sound like enough to shift the CG. But after some analysis, it seems like the idea stands up.

 

RB

[tallman]

Roger,

What we were told when bike debuted in '03 to best of memory.

No crash.

I've used a laser under rear wheel and seen where it hit the front.

There seems to be offset but I'd need to use real accuracy/levels etc before assuring the amount.

 

The GT's motor is longitudinally mounted and not sure of weight bias.

But y'all talking boxers so forget the hijack.

[roger 04 rt]

Roger,

What we were told when bike debuted in '03 to best of memory.

No crash.

I've used a laser under rear wheel and seen where it hit the front.

There seems to be offset but I'd need to use real accuracy/levels etc before assuring the amount.

 

The GT's motor is longitudinally mounted and not sure of weight bias.

But y'all talking boxers so forget the hijack.

 

I just went and searched for the K1200GT tracking specs. You've got a good memory. Here's what I found:

 

Permissible Wheel Track Offset: +14 mm to -5 mm, or about 0.75 inches total range

 

For the K1200GT plus means offset to the LEFT, where on the Oilheads a plus offset means to the RIGHT.

 

So that means the nominal position of the rear wheel is 4.5 mm to the left or about 0.18 inches.

 

What I find interesting is the word Permissable. I wonder if it's there to tell you it's okay to shift the wheel to balance the bike. A 19 mm range is far too big to be a manufacturing tolerance.

 

R1150

Range is 18 mm and is called Permissable Wheel Offset, a total range of 0.7 inches! More than enough to balance the bike. Range is therefore from 0.2 inches left of center to 0.5 inches right of center.

 

I know you can remove the shim between the rear wheel and FD, but I'm wondering what mechanisms BMW had in mind for moving the rear wheel to the right or the front wheel to the left.

 

Ideas?

 

From the Manual

Key to measurement result:

Wheel track offset “S” is the distance to left or right of the longitudinal axis of the rear wheel from that of the front wheel.

Negative sign = wheel track offset to left Positive sign = wheel track offset to right

Permissible wheel track offset (S)[/b):

...±9 mm (±0.3543 in); datum is +3.5 mm (+0.1378 in)

[dirtrider]

 

I know you can remove the shim between the rear wheel and FD, but I'm wondering what mechanisms BMW had in mind for moving the rear wheel to the right or the front wheel to the left.

 

Ideas?

 

 

Morning Roger

 

BMW probably has NO (official) means to move the rear wheel (therefore the large lateral tolerance).

 

There is the possibility of a rather large stack up of things that can effect rear wheel position.

 

Everything from trans casting/machining of the pivot bolt holes to bearing bore machining, to (fixed) pivot bolt machining to engine position in the chassis, to deformation of the thin aluminum trans & swing arm parts, to final drive machining & position on the swing arm, to final drive ring gear (spool) position for gear set mesh, to rear wheel machining, to even the front wheel position being out of position slightly (rear off-set is based against the front wheel position).

 

The only selective shimming I have seen from BMW is the crown bearing shims & those are determined by ring/pinion mesh not as a rear wheel off-set positioning shim.

 

With that +/- 9mm (based on +3.5mm nominal) it looks like BMW is saying unless something bent, broken, mis cast/ mis machined all is good-to-go from their aspect.

 

From the German standpoint if it PTTR then it must be American riders riding it incorrectly!

 

[dirtrider]

know you can remove the shim between the rear wheel and FD, but I'm wondering what mechanisms BMW had in mind for moving the rear wheel to the right or the front wheel to the left.

 

Morning Roger

 

You can "just" remove that wheel shim on the 1100 as the rear brake rotor is mounted to the final drive axle so stays in OEM position.

 

On the 1150 the rear brake rotor & tone ring are bolted to the wheel itself so removing that shim moves the brake rotor & tone ring over. Seeing as the brake caliper & speed sensor pick-up are final drive mounted that has to be addressed when moving the rear wheel over to the right.

 

[roger 04 rt]

Afternoon DR,

I hear you but nearly 3/4" is a huge allowance. Looking at the parts list and repair manual, as you said, there is no provision for adjustment. I think I'll measure mine and see what the offset is.

 

All that effort on their part to center the 15 lb. battery ... could have been used as a counter to the fuel.

 

There's always ride it as is, or 10-15 lbs. of lead somewhere ...

[Boffin]

I wonder if the weight offset is due to the need to provide a battery location for the authorities version. You can then bet that the accountants would veto having two tank designs which would re-balance the bike. Not to mention the opportunity to put a radio in the battery slot.

 

Andy

[Boffin]

Is there adjustment possible in the swing-arm bearings? a shim on one side compensated by the adjustable pivot? Just a thought.

 

Andy

[Paul Mihalka]

Is there adjustment possible in the swing-arm bearings? a shim on one side compensated by the adjustable pivot? Just a thought.

 

Andy

If you read my post, that is exactly what I did.

[Boffin]

Is there adjustment possible in the swing-arm bearings? a shim on one side compensated by the adjustable pivot? Just a thought.

 

Andy

If you read my post, that is exactly what I did.

 

Oops, Sorry Paul, i missed that post.

 

Andy

[roger 04 rt]

I wonder if the weight offset is due to the need to provide a battery location for the authorities version. You can then bet that the accountants would veto having two tank designs which would re-balance the bike. Not to mention the opportunity to put a radio in the battery slot.

 

Andy

 

Given that a battery located in the storage compartment is almost exactly the correct countering weight, it seems like a pretty good explanation.

 

Does a second battery sit it the plastic compartment or is there a special frame that goes along with it?

 

Paul,

Will a 2 mm shim fit on an 1150RT.

 

RB

[Boffin]

The extra battery has a simple arrangement of two pads and a retaining frame.

Real OEM

 

Andy

[roger 04 rt]

Thanks. I couldn't find it on the 1150 parts drawing. The weight 14 lbs. and position are right on for a balance. I'm going to try 14 lbs. of lead shot there once we lose the hurricane that's passing by us.

[Right Turn]

This is simple mechanics its called alignment you move the rear wheel to the right if the bike is pulling to the right. I don't know why BMW didn't engineer some kind of adjustment in these bikes and its not just the R bikes that have this problem. I can't believe all this discussion over simple mechanics and some of the people that are suppose to know better.

[dirtrider]

This is simple mechanics its called alignment you move the rear wheel to the right if the bike is pulling to the right. I don't know why BMW didn't engineer some kind of adjustment in these bikes and its not just the R bikes that have this problem. I can't believe all this discussion over simple mechanics and some of the people that are suppose to know better.

 

 

Evening Right Turn

 

On a single track vehicle it isn't that simple, it's more of a weight offset issue than an alignment issue. Lots of motorcycles have offset rear tracking & none that I know of have a pull to one side like BMW does.

 

If it was just a simple alignment issue then adding weight to the L/H side wouldn't improve the PTTR.

 

[tallman]

DR

I don't think you are one of those who "are suppose to know better."

 

 

[roger 04 rt]

Whether DR was one of the targets of "those who should know better or not" (he shouldn't be), DR's point, and I agree, is that moving the rear wheel for PTTR isn't about its alignment effect, rather it is about the movement of CG. It would be great to have some adjustment range for the rear wheel.

 

After all our discussion, it seems that BMW located the wheel for a loaded Authority bike, but left it out of balance when the second battery and associated gear was not included.

[Right Turn]

NGM Insurance

I finally found some BMW people that acknowledge this problem I was beginning to think I was the only one. I've ridden 7 different BMW's all of them pulled the R1200RT I rode pulled to the left. I've also ridden 1 Harley that pulled left 1 Valkyrie that pulled right and most recently a 2012 Concours, I thought I was riding my 03 K12GT. Now how do you get BMW to acknowledge the problem and do something about it. You can say it’s dangerous to ride with no hands on, you don't have to do it it’s just a safety check to assure things are going well and how safe is it to ride a bike that wants to run out of the road with yea and blisters the left side of the front tire.

 

[roger 04 rt]

With the large fuel tank concentrated on the right hand side of the motorcycle, there will always be a fuel level where the motorcycle is out of balance. I guess we just keep both hands on the wheel.

[Right Turn]

This is alittle extreme, but this guy claims he fixed his run out of the road BMW.

 

http://robertsilas.com/documents/35.html

[dirtrider]

Afternoon Right Turn

 

Seems like a lot of work not to mention destroying a good factory wheel & needing to repaint it as well as possibly having a tire clearance issue with some tire brands.

 

Most riders that move the rear wheel over just remove the wheel shim then simply shim the rear swing arm over a few more millimeters. That gets it close enough to remove most of the PTTR.

 

[roger 04 rt]

It is extreme but is an example of using a shift of the wheel to move the Center of Gravity to compensate for fuel and other imbalances. Not all the fuel is on the right but the capacity is about 6.7 gallons or about 40 lbs., 20-25 lbs of which I estimate is concentrated on the right (should weigh it sometime). Since that 25 lb. imbalance will be there when the tank is full and not be there when empty, there is only so much you can do about it. You can take half of the 25 lbs. and put it on the right or move the wheel a couple millimeters. Or some combination of both.

 

Even though I notice it when I take my hands of the handlebars, I don't really notice it in normal driving.

[roger 04 rt]

... You can take half of the 25 lbs. and put it on the right or move the wheel a couple millimeters. Or some combination of both. ...

 

I meant put half on the left hand side. Of course all this is if it matters ...

[Right Turn]

That's what I did remove the shim and make sure the tires are aired up. How do you (shim the rear swing arm over) I have though of doing this just don't know where to start.

[dirtrider]

--

How do you (shim the rear swing arm over) I have though of doing this just don't know where to start.

 

Morning Right Turn

 

It sounds like you haven't read all the posts in this thread.

 

Moving the swing arm over & what thickness shim (max movement) is clearly pointed out in one of the posts above in this thread.

 

[Right Turn]

No I haven't read all the post until now pages 5 & 6 tell the story, I had researched this a couple of years ago and thought what needed to be done but was unsure about how much shim would work, I had even though about moving the front wheel don't think that would be a good idea thou. One thing that scared be away was seems like the maintenance manual said you have to heat the connections to break the bolts loose. I found this site a couple of years ago and was unable to get a login until this month.

 

Once again glad I found some BMW people that will talk about this issue.

 

I belong to 3 other BMW sites, have mentioned it to numerus other BMW riders/shops and they don't want to talk about it and or they blame it on the camber in the road you know the scenario.

 

[dirtrider]

Morning Right Turn

 

Yes, you have to (should anyhow) heat those pivot bolts to 148°f before removing. If you don't there is a good chance that the LocTite will pull the threads out of the aluminum.

 

You can use a small industrial heat gun or some just use a cheap little pin point torch & play the heat into the center of the pivot bolt hex hole.

 

If you have a lot of miles on your bike those pivot bolts should be re-greased or replaced anyhow.

 

[Right Turn]

You mean replaced with new ones. I have 2 bikes 1 with 86,000 and 1 with 49,000 miles.

[roger 04 rt]

No I haven't read all the post until now pages 5 & 6 tell the story, I had researched this a couple of years ago and thought what needed to be done but was unsure about how much shim would work, I had even though about moving the front wheel don't think that would be a good idea thou. One thing that scared be away was seems like the maintenance manual said you have to heat the connections to break the bolts loose. I found this site a couple of years ago and was unable to get a login until this month.

 

Once again glad I found some BMW people that will talk about this issue.

 

I belong to 3 other BMW sites, have mentioned it to numerus other BMW riders/shops and they don't want to talk about it and or they blame it on the camber in the road you know the scenario.

 

Reflecting on this, I find it interesting that I'm riding a motorcycle that requires a constant 1.5 degree left hand turn, which also means to make a 1.5 degree left turn you have to make a 3 degree input. When I balanced it with weights, it felt more responsive. When I offset it by 20 lbs. on the left it felt weird, needing a 1.5 degree RIGHT turn all the time; I guess that's a good indication of how used to the constant left turn I've become. Interesting ...

[Dave Parry]

I think this is all a massive fuss over nothing! After all we don't change our riding style or position every time we fill the tank or go onto a road with a slightly different camber do we.

We just adapt accordingly using control inputs as necessary to keep the bike straight or to negotiate bends or corners, it's just an instinctive reaction that we all have otherwise we wouldn't be able to control the bike at all!

 

Dave.

[Right Turn]

You say you ride with your left hand on your thigh and the right on the handlebars what happens with no hand on the handlebars.

[Boxerdad]

Wow..I didn't intend this to go quite this crazy. I understand the 1100RT pulls to the right, I've since taken a ride on a friend's 1150RT. Alas..It also pulled to the right.

 

I'm really a little afraid to ask this. Sigh...Do 1200RTs pull to the right also, or did BMW finally get their RTs to track straight?

 

My 1100RT is getting long in the tooth, and I'd like to replace it with an RT that does not pull to the right. I just don't know if that animal exists. Thoughts?

[Don M]

The RT pulls to the right because it's design places more weight on the right side. The drive line and differential are on the right and more gas is carried in the right side of the tank because the glove box reduces volume on the left side. If you put weight in the glove box or the left side case the problem goes away. You can also reduce the problem on the 1100 RT by removing the shim between the rear wheel and the final drive, allowing the wheel to sit farther to the right.

[dirtrider]

Afternoon Boxerdad

 

The 1200RT is pretty good for not pulling either direction. For one thing the 1200RT has the air intake on the other (R/H) side so the fuel tank has that larger ear that holds more fuel on the L/H side.

 

[Boxerdad]

Thank you!

Afternoon Boxerdad

 

The 1200RT is pretty good for not pulling either direction. For one thing the 1200RT has the air intake on the other (R/H) side so the fuel tank has that larger ear that holds more fuel on the L/H side.

[roger 04 rt]

Has anyone ridden an RTP with a second battery and radios? That should be closer to balanced.

[biometrics]

My first ride on my 1999 R1100RT-P was 300 miles of interstate highway to get it home. I would have to say that I did not feel any tendency to pull in either direction. The second battery was still installed for the ride, but no radios. I pulled the battery when I got it home because it was dead... I still don't feel a pull to the right when riding...