R1100RT Pull To The Right

[Right Turn]

Did you take both hands off the handle bars.

[biometrics]

I have but not too long because of the deceleration. New tires can make a significant difference in the ride and tracking of your cycle too.

[roger 04 rt]

Today I took a ride over to Mass Diving in Natick. I wanted to see how big a three pound nylon pack of lead diving pellets were--about 3" X 4" X 3/4". I bought 4 and fit them easily in the bottom inch or so of the "glove compartment" on the left hand side of the fuel tank. So i now have 12 lbs. lead shot exactly opposite the unbalanced fuel. It's hard to tell they're there.

 

Rode home with the throttle lock on. Bike is balanced enough to ride and make left/right turns handsfree. It may be my imagination but the bike now seems more agile.

 

[cruisin]

Without getting heavily involved in the "why" debate, let me just add; I have now owned two 1100RTs ('98 & '00) with accumulated mileage of over 120K. Both of them pulled badly to the right upon purchase. I cured PTTR in both 100% simply by removing the 2mm shim Paul metioned a few pages back. Since (as Paul stated) there has never been an official explanation for the shim, I have this theory. Some BMW engineer saw that there was potential for a misalignment to the left during assembly but not to the right. He therefore designed the shim in so the end consumer would have an option for correcting PTTR. OK, I'm done.

[breyfogle]

Use of the rear wheel shim pre-dates R11xx bikes. My 1988 K75S has the same 2mm shim. Seems unlikely that two so different designs over such a long period of time would have the same weight distribution "problem" ... Curious !

[nrp]

Use of the rear wheel shim pre-dates R11xx bikes. My 1988 K75S has the same 2mm shim. Seems unlikely that two so different designs over such a long period of time would have the same weight distribution "problem" ... Curious !

or just shifting our precision butts a couple of millimeters laterally on the seat should do the same thing.............

[dirtrider]

Use of the rear wheel shim pre-dates R11xx bikes. My 1988 K75S has the same 2mm shim. Seems unlikely that two so different designs over such a long period of time would have the same weight distribution "problem" ... Curious !

 

Afternoon breyfogle

 

Commonsense tells us that the shim wasn't put there by BMW to adjust the PTTR out of the bike.

 

First off- all the BMW 1100/1150's pull to the right so why would BMW install that shim to make the pull to the right worse? Be much more logical that BMW would NOT install that shim as it cost them extra money & manpower to install then offer it as a service part to add in if there EVER was a bike that pulled to the left (I haven't ever seen one pull to the left though).

 

Next common sense filter to pass through-- If that shim was an added expense to BMW & added as a removable shim then why would there be no service procedure to remove that shim if the rear wheel offset was too far left? Or why no service bulletin (ever) to remove it to correct all the warranty PTTR complaints?

 

Finally-- BMW is not noted to look that far ahead to make anything easier for the end user to remove their screw ups. Heck, they won’t even acknowledge their screw ups let alone forecast their future.

 

[roger 04 rt]

Use of the rear wheel shim pre-dates R11xx bikes. My 1988 K75S has the same 2mm shim. Seems unlikely that two so different designs over such a long period of time would have the same weight distribution "problem" ... Curious !

or just shifting our precision butts a couple of millimeters laterally on the seat should do the same thing.............

 

If you wanted to do it by shifting your precision butt and you weighed 180 lbs, you'd have to shift it left 3.5" ...

[cruisin]

Like I said it's MY theory; no one has to accept it. Keep in mind though that I had 100% success in curing PTTR in not one but two 1100RTs simply by removing that 2mm shim. Maybe the engineer that designed it in was drunk at the time and forgot to tell anyone what he had done--or not.

[dirtrider]

Evening Cruisin

 

Even if the engineer (more likely a designer though) was drunk & didn't tell anyone---

 

Someone had to OK the part for production, someone had to approve the expenditure of money to produce it, someone had to make the part & assign it a part number, someone(s) had to run long term durability & testing on the part & it's interface with the brake & wheel, & someone had to approve an assembly line installation timing & place as well as the part handling procedure to get it there.

 

Then this would have had to have been carried through an entire model & into the new model with a different brake rotor mounting & wheel design.

 

Though this entire multi model process many engineers, assembly engineers, & bean counters would have been trying their darndest to remove that part from the system as a cost savings, a time savings, a parts handling savings, & a weight savings.

 

What do you think the chances of that part just slipping through the system for all those years? Yep, not a chance.

 

[cruisin]

dude, it (the theory) was all in levity--lighten up already.

[cruisin]

for those of you with PTTR and a shim; remove it, test ride it. If PTTR is gone you are done and it was free. If it is not gone, put it back and find another way -- still all for free.

 

btw: there has still not been an official explanation from BMW or anyone else what the purpose of the shim is.

[dirtrider]

---

 

btw: there has still not been an official explanation from BMW or anyone else what the purpose of the shim is.

 

Evening cruisin

 

Who knows why BMW requires that shim (washer).

 

The 1150R ONLY required it for bikes with the I-ABS antilock system so that might tell us something.

 

As far as I know it wasn't used on the GS with spoke wheels either.

 

In about every case I can think of that we have used a wheel spacer shim in the auto industry it has been to correct a stack up clearance issue wheel or tire clearance issue.

 

[nrp]

Use of the rear wheel shim pre-dates R11xx bikes. My 1988 K75S has the same 2mm shim. Seems unlikely that two so different designs over such a long period of time would have the same weight distribution "problem" ... Curious !

or just shifting our precision butts a couple of millimeters laterally on the seat should do the same thing.............

 

If you wanted to do it by shifting your precision butt and you weighed 180 lbs, you'd have to shift it left 3.5" ...

How did you come up with that figure? That would be an incredible moment. I looked at the moment generated by a typical rear wheel vertical force with the tire patch running out-of the CG plane.

 

I have trouble with these small shims etc in that years ago I had ridden my R100/7 with only one bag on one side, and was amazed a how little steer torque was required.

[roger 04 rt]

How did you come up with that figure? That would be an incredible moment. I looked at the moment generated by a typical rear wheel vertical force with the tire patch running out-of the CG plane.

 

I have trouble with these small shims etc in that years ago I had ridden my R100/7 with only one bag on one side, and was amazed a how little steer torque was required.

 

I'll do the math slowly.

 

...

Here are some back of the napkin calculations and estimates. They're not exact but are in the right ballpark.

 

1) With a full tank there is about 20 lbs weight at 28" off the ground and about 9" right of center.

 

2) 10 lbs of unbalanced driveshaft on the right versus exhaust on the left that's 15" off the ground and about 6" right of center.

 

1) Arm for fuel is 29.5". Angle is 18 degrees. Perpendicular force for 20 lbs. fuel is 6.18 lbs. moment in in.-lbs is 182.

 

2) Arm for driveshaft is 16". Angle is 22 degrees. Perpendicular force is 4 lbs. Moment is 64 in.-lbs.

 

Total moment is 246 in.- lbs. toward the right.

 

Rider weighs 180 lbs. height from ground is 28". To overcome 246 in-lbs need 8.78 lbs at 28 inches. Sin(x)=8.78/180=0.049 therefore x=3 degrees. Tan(3 degrees)=0.052 therefore shift is 1.5" but that would only be true if all 180 lbs. could be shifted. My guess would be that half your body weight can move, not arms and legs. So double the shift and you arrive at 3 inches.

 

So my quick calc of 3.5 inches was about right. The 3" shift is about 76 mm a lot more than the "couple" of millimeters you guessed at first. And that 3 inch shift is a lot more than you can comfortably make.

 

The reason the left shift needed by the rider is so large compared to moving the rear wheel is that the rear wheel offset gets to use nearly the whole 800 lb. total weight of the bike & rider; while the 180 lb. rider shifting his butt only has 90 lb. of body to work with. The rest of the answer is how small the sinmof small angles become.

[tallman]

Doesn't force input on handlebars alter that?

I still feel peg input varies my average rider when they shift in seat.

Professional golfers have a huge variation in weight distribution and shift before/during/after swing.

This takes a special scale to measure.

 

 

I think I have experimented with different input force on bars/pegs

while shifting position in saddle and can change directional vector w/out much input change.

 

After reading this thread aloud to my bike it now pulls to the left.

[roger 04 rt]

Doesn't force input on handlebars alter that?

I still feel peg input varies my average rider when they shift in seat.

Professional golfers have a huge variation in weight distribution and shift before/during/after swing.

This takes a special scale to measure.

 

 

I think I have experimented with different input force on bars/pegs

while shifting position in saddle and can change directional vector w/out much input change.

 

After reading this thread aloud to my bike it now pulls to the left.

 

(laughing ...) Could you come talk to my bike about taking a bath?

 

Input force (only a little bit) completely overcomes this issue. You're right. In my case I didn't even know I had PTTR until someone pointed it out. I think my 3" inch left body shift is about right. If one weighs 270 lbs., 2" would do. The pegs don't have much of a lever arm and it would take a lot of force there.

[Right Turn]

I was told by a so called BMW Mechanic at a so called BMW dealer in Atlanta that if I removed the shim my I-ABS wouldn't work. So called BMW Mechanic/Shop Supervisor was afraid to take his hands off the handle bars.

 

BMW Dealer owner told me I should place heavy stuff in the left saddle bag and sit to the left, He also pretty much called me and A##hole for saying anything about their PTTR problem.

[dirtrider]

Morning Buster

 

On the 1100 removing the spacer is a non issue as both the rear brake disk & the ABS tone ring are mounted to the final drive so they don't move with the wheel movement.

 

On the 1150 (I-ABS) both the brake disk & the tone ring are mounted to the wheel so they move laterally with the wheel movement.

 

Removing the spacer on the 1150 does move brake disk inside the caliper & does move the tone ring closer to the wheel sensor. With worn rear brake pads then no issue with the rotor movement & even with new brake pads not always an issue (just something to look for).

Same with the tone ring to wheel sensor, not all will make contact but when removing that spacer on the 1150 you have to pay close attention to the wheel speed sensor being too close to, or contacting the tone ring.

 

[roger 04 rt]

Today I took a ride over to Mass Diving in Natick. I wanted to see how big a three pound nylon pack of lead diving pellets were--about 3" X 4" X 3/4". I bought 4 and fit them easily in the bottom inch or so of the "glove compartment" on the left hand side of the fuel tank. So i now have 12 lbs. lead shot exactly opposite the unbalanced fuel. It's hard to tell they're there.

 

Rode home with the throttle lock on. Bike is balanced enough to ride and make left/right turns handsfree. It may be my imagination but the bike now seems more agile.

 

Since the time I've put the lead weights in, that I'd nearly forgotten about I've run the tank down to nearly empty. Down at 1 bar on the fuel gauge, maybe a gallon and a half of fuel ...

 

Now there is a very slight pull to the left. And with a slight PTTR with a full tank, I think something in the 12 lb. vicinity in the radio compartment makes a good compromise.

 

Balanced now it seems to be more responsive at all fuel levels.

[Clive Liddell]

+1 Roger.

 

I used 2.5 oz clip on car wheel weights laid side by side two or three "deep" laid in the glove compartment with results similar to yours.

 

 

[roger 04 rt]

+1 Roger.

 

I used 2.5 oz clip on car wheel weights laid side by side two or three "deep" laid in the glove compartment with results similar to yours.

 

 

Glad to hear that. How much total weight did you use?

[Clive Liddell]

Roger,

 

It was a few years ago and I really don't recall the total weight. I just packed in the wheel weights to end up with a flat floor to the glove compartment and with enough space above for the tool roll and a few other odds and ends.

[roger 04 rt]

Earlier in the thread I mentioned that I had gotten rid of the pull to the right by adding some weights. Twelve pounds in the front storage box seems to do the trick nicely. A side benefit: the handling is more nimble since you're not holding a slight force against the natural pull.

 

I finally got around to taking a photo and as you can see below, the lead shot takes very little space.

 

[Clive Liddell]

Hi Roger,

 

Do you notice that as your fuel gets towards empty the bike starts pulling to the left slightly :>) Mine does...

[roger 04 rt]

Yes I did, very slightly. Very slightly right with a full tank.

 

In both cases I can let go of the handle bars with just a bit of "body English".