I know - they all pull to the right, but.....

[kiwiaudio]

Has anyone tried the washer behind the swingarm pivot bolt mod, that is mentioned way down the bottom of the FAQ page on this subject? I've removed these pivot bolts a few times before, and am not beyond doing it again. The writer said it fully cured his pulling issue in combination with removing the wheel spacer, which i've already done.

 

By the way, never use loctite high strength red 271 on these pivot bolts- it just laughed at the heat from my gun and I was wondering if I'd ever get them off!

Last time I used the regular 242 blue loctite.

[BMWRich58]

Has anyone tried the washer behind the swingarm pivot bolt mod, that is mentioned way down the bottom of the FAQ page on this subject? I've removed these pivot bolts a few times before, and am not beyond doing it again. The writer said it fully cured his pulling issue in combination with removing the wheel spacer, which i've already done.

 

By the way, never use loctite high strength red 271 on these pivot bolts- it just laughed at the heat from my gun and I was wondering if I'd ever get them off!

Last time I used the regular 242 blue loctite.

 

Two hex head GS Beemers and both ride/ran straight as an arrow!!!!

Maybe time to switch to a GS????

Even my airheads were straight drivers...

[RSL]

Start with removing the big spacer between the wheel and hub, if you haven't already. That cures most PTTR and makes it hardly noticeable.

[swilson]

When you say big spacer are you talking about the thin metal spacer that has a large hole for the hub center and small holes for the wheel studs to pass through?

[RSL]

Yep.

[Ken H.]

When you say big spacer are you talking about the thin metal spacer that has a large hole for the hub center and small holes for the wheel studs to pass through?

You can get away with removing the spacer on an 1100 series because doing so won't disrupt the brake rotor to caliper spacing. But on the 1150 series it will and thus removing the spacer is a poor idea.

[AviP]

Two hex head GS Beemers and both ride/ran straight as an arrow!!!!

From what I know of PTTR, the effect is felt in the vertical plane that runs along the length of the bike. It induces the bike to turn to the right and your involuntary correction at the handlebars negates it. So you may have PTTR and not know it. Here's a simple test.

 

With the engine on at idle, both feet planted on the ground, rev the engine to 5K rpm. If it pulls to the right .... Yeah, it's that easy.

[bmwmick]

When you say big spacer are you talking about the thin metal spacer that has a large hole for the hub center and small holes for the wheel studs to pass through?

You can get away with removing the spacer on an 1100 series because doing so won't disrupt the brake rotor to caliper spacing. But on the 1150 series it will and thus removing the spacer is a poor idea.

 

Ken is absolutely correct here. Do NOT remove that spacer on the 1150's OR on the 1100's. It is there for a reason and a 2mm spacer will not correct or cause PTTR.

 

Mick

[smiller]

It is there for a reason and a 2mm spacer will not correct or cause PTTR.

Removal didn't cure PTTR on my bike but it sure seemed to lessen the effect. In any event I can't see the harm in removing the spacer on an 1100.

[bmwmick]

It is there for a reason and a 2mm spacer will not correct or cause PTTR.

Removal didn't cure PTTR on my bike but it sure seemed to lessen the effect. In any event I can't see the harm in removing the spacer on an 1100.

 

Seth,

I believe you believe it. Can't argue that.

 

The spacer is put there to increase the friction between the wheel and the final drive hub. I think I can dig up an article that describes that function in a law suit from a few years ago.

 

Mick

[smiller]

I believe you believe it. Can't argue that.

And I in turn will agree to believe that you don't believe it...

 

Seriously, how did you come to determine that it is impossible for a rear wheel displacement of 2mm to affect vehicle tracking (which seems to be the implication of your earlier statement)? Not trying to be argumentative, just wondering what method you used to calculate this.

[GrafSpee]

Seriously, how did you come to determine that it is impossible for a rear wheel displacement of 2mm to affect vehicle tracking (which seems to be the implication of your earlier statement)? Not trying to be argumentative, just wondering what method you used to calculate this.

 

I don't know what he used, but I used calculus

 

(see attachment)

[bmwmick]

I believe you believe it. Can't argue that.

And I in turn will agree to believe that you don't believe it...

 

Seriously, how did you come to determine that it is impossible for a rear wheel displacement of 2mm to affect vehicle tracking (which seems to be the implication of your earlier statement)? Not trying to be argumentative, just wondering what method you used to calculate this.

 

I've ridden my RT with and without the spacer just as a test. No difference and no PTTR with or without.

The factory stated maximum wheel offset is 9mm or 0.354". I don't see how 0.078" can make any noticable difference.

 

Mick

[smiller]

I've ridden my RT with and without the spacer just as a test. No difference and no PTTR with or without.

The factory stated maximum wheel offset is 9mm or 0.354". I don't see how 0.078" can make any noticeable difference.

Well the fact that I've seemed to notice a difference and you have not doesn't mean much, purely anecdotal on both our parts. But the 9mm maximum offset is interesting. I'm missing something though, in that on my bike a 9mm offset would put the tire against the swingarm. Are they saying that a 9mm offset either way from the centerline is permissible? Or do they mean 4.5mm in either direction, which seems more reasonable.

 

In any event I don't know that that spec alone necessarily means that a smaller deviation can't possibly affect vehicle handling. Or perhaps the (rather common) perception that the spacer can make a difference on some bikes is just a mass hysteria... wouldn't be the first time...

[chrisolson]

... Or perhaps the (rather common) perception that the spacer can make a difference on some bikes is just a mass hysteria... wouldn't be the first time...

put me in with the mass hysteria crowd. When I first got the RT it didn't pull to the right, it dove to the right. When I removed the spacer it sure **seemed to me** that it was less... now it only had normal PTTR

[bmwmick]

I've ridden my RT with and without the spacer just as a test. No difference and no PTTR with or without.

The factory stated maximum wheel offset is 9mm or 0.354". I don't see how 0.078" can make any noticeable difference.

Well the fact that I've seemed to notice a difference and you have not doesn't mean much, purely anecdotal on both our parts. But the 9mm maximum offset is interesting. I'm missing something though, in that on my bike a 9mm offset would put the tire against the swingarm. Are they saying that a 9mm offset either way from the centerline is permissible? Or do they mean 4.5mm in either direction, which seems more reasonable.

 

 

I looked closely at the wording in the frame-check section and it appears they allow + or - 9mm wheel track misalignment.

 

Mick

[flyboy]

try putting your heavy items in the left saddlebag. I do this and it seems to reduce the pttr significantly.

[motoguy128]

I think I just tend to naturally sit slightly off center to the left to compensate. I have a good sense of balance from years of racing bicycles and do it automatically. I've never noticed at PTTR issue, but I also come to expect some strange characteristics due to the engine layout... and it's german. ALL German machinery at home or at work that I've every worked with is somewhat quirky.

[kiwiaudio]

No one has yet stated whether they have tried offsetting the front of the swingarm an additional 2mm as stated in the FAQ, although, along with others here, i'm having a hard time believing 2mm will effect anything !!

Personally, i think the very high center of gravity, that is an inherent nature of these bikes, exarcebates this pttr phenomenon - as in - I think mine is worse with a full tank of gas !

[T__]

No one has yet stated whether they have tried offsetting the front of the swingarm an additional 2mm as stated in the FAQ, although, along with others here, i'm having a hard time believing 2mm will effect anything !!

Personally, i think the very high center of gravity, that is an inherent nature of these bikes, exarcebates this pttr phenomenon - as in - I think mine is worse with a full tank of gas !

 

Mark, about all the late model Harley dressers have an offset rear wheel/tire to clear the belt (some where’s between 3/8” & ½” ) & none of them pull to the right.. The rear wheel offset position is somewhat controversial (just like the BMW bunch) as there are 2 ways to align that rear wheel,, one is a straight offset (front & rear wheel offset maintained but both pointing forward on separate lines) .. The other way is the offset maintained but the rear wheel aligned to be on the same travel line as the front wheel (basically the rear wheel crooked in the chassis) .. I have tried both ways & while I won’t clutter this site with the details there is a significant difference is HIGH SPEED tracking & stability,, low speed pulls or tracking doesn’t seem to be factor in either set up..

 

On both my old 1100RT & now the 1150RT there is a distinctive drift to the right ( I won’t exactly call it a pull though).. The severity of the drift seems to be effected by the current state of front & rear tire wear & amount of weight I carry in the L/H pannier.. The drift did seem to be worse with a lightweight aftermarket exhaust system..

 

I have checked the tracking alignment on both bikes (1100 & 1150) & both were less than 3mm.. It’s difficult to check offset as BMW doesn’t give any frame hole coordinates to measure from..

 

From my personal observation the drift to the right seems to be mostly weight induced as the center of mass seems to be right of center.. If I load the L/H pannier with my rain gear, extra boots, & other travel items the drift to the right is almost null..

 

Based on personal observations I would venture to guess that ANYTHING you do to move the center of mass to the left-- like remove the wheel spacer,, move the rear control arm,, move the seat,, sit off center, etc will have a positive effect on PTTR.. Now based on my Harley experience if you just start moving the rear wheel position in a lateral direction without also correcting the wheel tracking you could inherit some high speed issues (probably slight but still noticeable) ..

 

Twisty

[RSL]

Another reason for pulling to the right, at least on my particular '94 RS bike, is the fuel tank having more volume on the right side than on the left. Looks like maybe 1-1.5 gallons more In the lower right lobe of the tank, whereas no lobe at all on the left side, adding to imbalance.

[Tipover_Bob]

As a new owner I am not very qualified, however, my bike certainly pulls hard to the right or did. More than my K75 ever did. I complained about it before negotiating my price last week. However, I gotta tinker. It appears to me the pull to the right has gotta have something to do with the front wheel, because you gotta push the front wheel to the right to stay straight on the road. Soooo, I undid all the front fork bolts and pushed the front wheel gently to the right against the stop and retightened them (bolts). Wow, significant improvement. Bike now tracks straight if I lean just a bit to the left. Soooo, tonight I will work on it just a bit more. I will make sure the tubes are exactly even on the top, I will loosen all clamp bolts and axle bolt, I will add a beer can shim under the crossover on the right side and I will retighten all bolts (using blue loctite of course) while holding the front wheel lightly against the right hand stop. I just can't believe something as well engineered as this bike doesn't track properly.

(It is possible that when tires were replaced, one typically holds the front wheel while torquing the crossover bolts, possibly causing a slight twist in the sliders contributing to a pull to the right?)

 

Tipover Bob

[twins4life]

Mine PTTR at times then other times it is perfect. I just attribiute this to road crown. The roads (almost) always slope to the right to encourage water to drain away from the median. My truck pulls to the right too for the same reason, as have all of my trucks.

[Haynes]

...I just attribiute this to road crown. ..

They also PTTR in Australia where ride on the left and the road camber is opposite to yours.

Both of my RT bikes have gone absolutley straight but I have ridden a couple that have been almost impossible to ride without constant steering input. I have offered to diagnose the problem but the owners weren't bothered by it. Instead, they corrected it by loading the left case.

 

I believe that loading the left side is not correction but compensation.

[twins4life]

Well that about kills my theory. Thanks for posting, I hate to propagate error.

 

Amazing, what causes it to PTTR?

[T__]

Well that about kills my theory. Thanks for posting, I hate to propagate error.

 

Amazing, what causes it to PTTR?

 

 

George, as mentioned, if the PTTR was road induced it would pull to the left in drive left countries or when on the L/H side of road center in the USA (they still PTTR in the L/H lane of the freeway or left of road center when passing)..

 

If it were caused by bike geometry the PTTR would get worse as the road speed increased (most I have ridden get better as the road speed increases).. (exception here is bad tires). In fact my present 1150RT will go hands off straight for a long ways at 80+ mph, there is some PTTR at 20-40 mph though..

 

In a lot of cases tire wear can & will exaggerate the PTTR so we will assume new tires here..

 

There is some rear wheel off-set on the BMW boxer but a lot of shaft drive bikes have rear wheel off-set with no obnoxious PTTR.. The Harley dresser has a very pronounced rear wheel off-set to clear the drive belt & those bikes are very directionally stable going down the road (I could ride my Electra Glide all day long hands off if no sharp curves involved)..

 

About all the leaves is weight bias on the oil head boxer as a cause of PTTR.. Plus the fact that adding weight to the L/H side or sitting off center will make them go straight..

 

If you look at the weight center vs. the bike center line you will soon see the trans gearing is almost ALL right of center (lots of heavy gears right of center),, the rear drive shaft & housing is also right of bike center line,, the rear final drive & brake parts are right of bike center line also.. About the only weight Left of center is the muffler itself but the majority of the cat converter weight is right of center.. My guess is that if took that amount of weight that is right of bike center line & move it to the L/H side the bike would track straight down the road.. It takes way less weight than is right of bike center to be placed in the L/H pannier to make them go somewhat straight with little or no PTTR (probably due to the fact that the weight is farther off the bike center line)..

 

 

Twisty

[Haynes]

I think Twisty is close to the mark. Weight is the most obvious suspect. Standing the bike vertically using an accurate spirit level on the wheel rims could prove this. If PTTR is caused by weight, in this vertical stance the bike should indicate some weight bias to the right.

 

Alternately, with the bike standing balanced, the wheel offset from vertical could be measured to indicate weight bias.

 

On the two bikes I have ridden with severe PTTR, I feel that it was much more than weight. The steering gave prominent and forceful feedback that indicated much more than weight. Furthermore, shifting my weight to the far left side of the seat failed to eliminate it.

 

PTTR is a great discussion topic and perhaps we are incorrectly assuming that it all emanates from the same cause. On the worst bikes, perhaps it's a combination of elements.

 

One question of weight: If the right side of the bike is heavier, the bike will ride balanced tilted slightly left. Shouldn't this cause camber thrust and turning to the left and not to the right?

[T__]

I think Twisty is close to the mark. Weight is the most obvious suspect. Standing the bike vertically using an accurate spirit level on the wheel rims could prove this. If PTTR is caused by weight, in this vertical stance the bike should indicate some weight bias to the right.

 

Alternately, with the bike standing balanced, the wheel offset from vertical could be measured to indicate weight bias.

 

On the two bikes I have ridden with severe PTTR, I feel that it was much more than weight. The steering gave prominent and forceful feedback that indicated much more than weight. Furthermore, shifting my weight to the far left side of the seat failed to eliminate it.

 

PTTR is a great discussion topic and perhaps we are incorrectly assuming that it all emanates from the same cause. On the worst bikes, perhaps it's a combination of elements.

 

One question of weight: If the right side of the bike is heavier, the bike will ride balanced tilted slightly left. Shouldn't this cause camber thrust and turning to the left and not to the right?

 

Squeaky, in my limited exposure to the BMW PTTR in my opinion it definitely is not always from the same ONE source.. It feels like an accumulation of sources..

 

On my personal BMW’s the PTTR is/was always there from day one.. It gets worse as the tries wear (can’t tell if only front or both front/rear).. New tires moderate the PTTR to a very minor distraction that is much more noticeable at lower vehicle speeds.. As the tires wear the PTTR follows the vehicle speed to a higher MPH & also needs more rider input to counteract..

 

I have had my digital inclinometer on the front & rear wheels of both of my BMW oilhead boxers & a friends oilhead with the results being there is no apparent angular difference in the vertical plane of the bikes I measured so I don’t think it’s a vertical twist as the cause.. I have tried to use two bathroom scales to balance my feet on while sitting still but that didn’t give me an accurate indication of balance (though it would but didn’t work worth a hoot) .. One thing that comes to mind on balance is most R1100/R1150RT fall overs are to the R/H side (maybe just coincidental, I just don’t know)..

 

I have owned a LOT of motorcycles in my lifetime, some with offset engines, some with offset tracking wheel tracks,, some even with bent forks & NONE have pulled to one side or the other like the BMW oilheads do..

 

My present R1150RT with almost new tires hardly pulls to the right but if I sit well centered on the bike it definitely PTTR as lower speeds.. At high speeds it isn’t a problem.. If I ride with my hands on the bars it isn’t even noticeable.. With well worn tires it can be felt with hands on bars but not uncomfortable to ride.. If I put most of the heavy objects in the L/H pannier it pretty well goes straight even with worn tires..______ Maybe if I put my wallet in my L/H pocket,, put my watch on my L/H wrist,, put all my loose change in my L/H pocket,, clip my cell phone on L/H side & hang my tongue out the L/H side of my mouth it will then go straight down the road!!!!!!!

 

Twisty

[Ken H.]

About all the leaves is weight bias on the oil head boxer as a cause of PTTR.. Plus the fact that adding weight to the L/H side or sitting off center will make them go straight..

All good thoughts, but how does one explain that the phenomenon is gone in the hexheads? They still are over heavy on the right, but no PTTR.

[T__]

About all the leaves is weight bias on the oil head boxer as a cause of PTTR.. Plus the fact that adding weight to the L/H side or sitting off center will make them go straight..

All good thoughts, but how does one explain that the phenomenon is gone in the hexheads? They still are over heavy on the right, but no PTTR.

 

 

Ken, that’s a real good question.. I wonder what is different between the bikes? For instance where is the balance shaft placed in the engine or is the rear wheel placed farther to the R/H side? I wasn’t aware that the Hexhead didn’t have PTTR.. I have ridden the 1200 & that bike sure feels like it has a lower CG so maybe the weight is placed differently on the 1200..

 

You brought up a good point here so if we can figure out what the difference is between oilhead/hexhead bikes maybe we can then understand the PTTR situation..

 

Twisty

[Haynes]

digital inclinometer on the front & rear wheels.....so I don’t think it’s a vertical twist as the cause

 

This is good work. I never discount any theories but give greatest support to those who apply some sort of testing procedure.

My opinion is that if it can be accurately diagnosed, it can be cured.

 

A slight difference in the Australian RT models is that we have the radio as standard and no charcoal canister fitted. The radio adds weight to the left, the absence of the canister subtracts weight from the right. Even so, we still get a predominance of PTTR and occasionally a severe PTTR.

Perhaps there is such a thing as normal PTTR (weight) and severe PTTR (misalignment).

 

I remain totally open minded on the issue.

[kiwiaudio]

When I look at the steering geometry of these RT's with regard to the rake or trail, I cannot help but think this has something to do with the pttr. Few bikes I see have such an abrupt rake, even dirt bikes made to turn on a dime. This of course could be why the RT's handle so well.

This exerpt from http://www.rider-ed.com/tips/motorcyclestability.htm

seem to lend some credence to this theory, and if nothing else, the article makes interesting reading.

 

"If you projected a line through the Center of the bike steering head to the ground you would find the tire contact patch is behind this point. This distance between the two points is “trail”. This makes the front wheel inherently stable and want to “follow” where the steering head (and hence motorcycle) is going. Generally, a larger trail will tend to produce a slower steering, more stable motorcycle.

 

As a result of “trail” if the bike starts to lean left, even without rider input, the front wheel will turn to the left (buy a cheap model motorcycle and try it: roll the bike forward in a straight line, then lean the bike to the left, the front wheel will turn to the left without steering input). The force on the wheel returning it to the “in line” position, should it get out of alignment, increases with speed. This effect is similar to a weather vane pointing into the wind: the greater the wind speed the more rotational force returning it to face into the wind should it get out of alignment."

[T__]

When I look at the steering geometry of these RT's with regard to the rake or trail, I cannot help but think this has something to do with the pttr. Few bikes I see have such an abrupt rake, even dirt bikes made to turn on a dime. This of course could be why the RT's handle so well.

This exerpt from http://www.rider-ed.com/tips/motorcyclestability.htm

seem to lend some credence to this theory, and if nothing else, the article makes interesting reading.

 

"If you projected a line through the Center of the bike steering head to the ground you would find the tire contact patch is behind this point. This distance between the two points is “trail”. This makes the front wheel inherently stable and want to “follow” where the steering head (and hence motorcycle) is going. Generally, a larger trail will tend to produce a slower steering, more stable motorcycle.

 

As a result of “trail” if the bike starts to lean left, even without rider input, the front wheel will turn to the left (buy a cheap model motorcycle and try it: roll the bike forward in a straight line, then lean the bike to the left, the front wheel will turn to the left without steering input). The force on the wheel returning it to the “in line” position, should it get out of alignment, increases with speed. This effect is similar to a weather vane pointing into the wind: the greater the wind speed the more rotational force returning it to face into the wind should it get out of alignment."

 

Mark, you can’t really compare the BMW telelever front suspension to a conventional sliding fork front suspension as far as rake & trail go.. Especially if just drawing an imaginary line down through the steering head axis.. (just not the same).. The Telelever front fork system revolves around the instant center of the steering head at the upper fork attachment area & the ball joint (center of ball) in the control arm (& that point changes as the control arm moves up & down)..

 

Twisty

[jbr7t]

I used a MUCH easier fix to the PTTR. I just keep some stuff in the left sidecase. Don't knock it till you try it!

[twins4life]

Well that about kills my theory. Thanks for posting, I hate to propagate error.

 

Amazing, what causes it to PTTR?

 

 

George, as mentioned, if the PTTR was road induced it would pull to the left in drive left countries or when on the L/H side of road center in the USA (they still PTTR in the L/H lane of the freeway or left of road center when passing)..

 

If it were caused by bike geometry the PTTR would get worse as the road speed increased (most I have ridden get better as the road speed increases).. (exception here is bad tires). In fact my present 1150RT will go hands off straight for a long ways at 80+ mph, there is some PTTR at 20-40 mph though..

 

In a lot of cases tire wear can & will exaggerate the PTTR so we will assume new tires here..

 

There is some rear wheel off-set on the BMW boxer but a lot of shaft drive bikes have rear wheel off-set with no obnoxious PTTR.. The Harley dresser has a very pronounced rear wheel off-set to clear the drive belt & those bikes are very directionally stable going down the road (I could ride my Electra Glide all day long hands off if no sharp curves involved)..

 

About all the leaves is weight bias on the oil head boxer as a cause of PTTR.. Plus the fact that adding weight to the L/H side or sitting off center will make them go straight..

 

If you look at the weight center vs. the bike center line you will soon see the trans gearing is almost ALL right of center (lots of heavy gears right of center),, the rear drive shaft & housing is also right of bike center line,, the rear final drive & brake parts are right of bike center line also.. About the only weight Left of center is the muffler itself but the majority of the cat converter weight is right of center.. My guess is that if took that amount of weight that is right of bike center line & move it to the L/H side the bike would track straight down the road.. It takes way less weight than is right of bike center to be placed in the L/H pannier to make them go somewhat straight with little or no PTTR (probably due to the fact that the weight is farther off the bike center line)..

 

 

Twisty

 

Excellent information! Thank you! It makes sense now.

[Tipover_Bob]

Well, I fixed it and you all are right. I just had to tinker, cause I drank too much beer. The bike is pretty much fixed too. Everyone is pretty much right. Here are my fixes:

1. I undid all the bolts holding on the front wheel (clamp, axle, crossover).

2. I made sure the steering head clamps were holding the tubes exactly even.

3. I Placed two thicknesses of a budwiser can between the crossover and the slider on the right side. This encouraged a very slight canting of the front wheel to the right when combined with retightening the other bolts (4, 5 and 6 below).

4. I tightened the crossover bolts while holding the front wheel to the right against the stop with slight pressure.

5. I tightened the axle bolt (bottom of the sliders) while

holding the front wheel to the right against the stop with slight pressure.

6. I tightened the clamp bolts (bottom of the sliders) while

holding the front wheel to the right against the stop with slight pressure.

7. I moved my water bottle from my right saddlebag to my left saddlebag.

 

The bike is pretty much neutral now. When I ride in the right side of the tire tracks nearer the center line. When on the right side of the road it does pull to the right slightly. Handling around curves appears equal, right or left.

 

My theory is that a left camber or cock is accidently set up when tires are replaced. This is induced by holding the front of the front wheel when tightening the crossover bolts, the axle bolt and the clamp bolts. My tinkering just tried to correct for that.

 

I might add that my "new" bike's tires are pretty much worn out. This has probably increased the effect. I can't wait to put on new tires.

[Ken H.]

3. I Placed two thicknesses of a Budwiser can between the crossover and the slider on the right side.

What if I don't drink Budweiser?

[Tipover_Bob]

3. I Placed two thicknesses of a Budwiser can between the crossover and the slider on the right side.

What if I don't drink Budweiser?

 

I don't recommend using a glass bottle.