Boxer Balance

[tazplas]

I have on occasion taken both hands off the 'wheel' so to speak and i find that the bike wants to kick over to the right and then i have to shift my weight to the left to compensate.

 

My question is, is this a normal occurrence for Boxer bikes or does it happen to others? Can't remember it happening on the old GSX but that was some time ago.

 

I am fairly sure that i ride vertically but i suppose i need to have this checked from behind at some time.

 

Tyres have about 8000 kms on them and are not squared off or worn adversely on any one side. Running PR2's.

 

Any ideas.

 

Cheers

 

Steve

[Joe Frickin' Friday]

It's the RT, and it's normal. We call it PTTR (Pull To The Right).

 

Some people like to blame a torque reaction due to the longitudinal crankshaft or the driveshaft, but it happens whether you're on the gas or not, and whether the engine is spinning or not, and it doesn't happen on other bikes with a similar driveline, such as the Honda Goldwing.

 

A couple of years ago I stuck an inclinometer on my 1100RT's fuel tank and took some balance measurements. I figured out that the RT was perfectly balanced on its two tires when it was tipped about 1 degree to the left, which means that the center of mass is just a smidge to the right of the centerline when the bike is vertical. I'm pretty sure this is enough to account for the observed PTTR.

[Dave Faria]

Was the bike in neutral??? If not check for play in the pivot bearings in front of the rear drive. There are several articles on the web that talk about using a string to check frame alignment. My rear wheel tracks .1inches to the left of the front and always has. According to BMW anything less than .3inches is with in spec. I can't remember which or if my bike pulls one way or another any more. I hit a pot hole about 3 years ago and was worried abt it. I check the alignment probably every other tire change now to see how the frame bearings are working. I own a 2004 R1150RT with 71k miles. I've replaced only the pivot bearings in front of the rear drive.

[T__]

Steve, as Mitch said it is normal on the R1100/1150 BMW boxers.. The drive shaft weight & good portion of the transmission weight is offset.. ALL my R1100/1150’s did it.. I found that as I added weight (like tools & tire repair stuff) to the bike under the seat (I would try to keep it on the L/H side) & as I added things to the radio storage box on the L/H side the PTTR got better..

 

After a while I just paid no attention to it..

 

Just do a search on this web site..

 

Go to advanced search,, change the L/H box to search (oilheads),, put PTTR in the Keyword search Terms box,, change the Date Range to (3) & (Years) then click (Submit)..

 

Should be some reading on it there (Mitch did some work on finding or isolating it)..

 

You can also try “pulls to the right” (use the quotes) in Keyword search Terms box.. Or try “pulls right” or try “pull to right” (use quotes on more than one word)..

 

Or you can try +pulls +right

 

 

Twisty

 

[bmw_rider]

First check you bags - are they empty, or evenly loaded weight wise? Are you sitting centered on the bike?

[Paul Mihalka]

If you load the bags, put the heavy stuff in the left bag.

[Clive Liddell]

Steve,

 

The 1100 and 1150 RT fuel tank is not symmetrical. Allowing for the radio/glovebox and the air inlet duct results in the LH side having reduced capacity and therefore being lighter. Check carefully next time you are very low on fuel and again after topping up for a difference in PTTR.

 

I also have a R850R and I can always "let go the bars" and it tracks straight.

[NonComp]

My r1100r seems to track straight. I suspect that the muffler balances out the driveshaft. Maybe that's why the muffler is so darn heavy?

 

I don't think that the balance is inherent to the design of the basic machine, but maybe has something to do with the RT bodywork?

[flars]

My 98 RS and 2002 RT both PTTR. With bags or without bags. Full gas tank, empty gas tank. Right lane, or left lane. But depending on the road surface (high crown, no crown, compressed asphalt, etc) the PTTR can be negated/reduced.

Absolutely Normal.

[mneblett]

On my R11RT, I had a HUGE problem with this -- the bike pulled to the right hard enough to cause fatigue/pain in my left arm. After a lot of back and forth, a BMW rep that rode the bike pronounced it "ok" (yet admonished me to not take my hands off the bars, because the bike would turn to the right!! ).

 

I finally did a bit of experimenting and some back-of-the-envelope calculations and figured that if I could move the swingarm 3mm to the right, it should fix the problem. Of course, the swingarm position on an oilhead RT was not adjustable. My solution was to remove the right side swingarm pivot bolt and place a 3mm shim (a big washer) under the head of the pivot bolt, and reinstall the adjustable swingarm pivot bolt on the left side 3mm farther in towards the right. It worked -- no more pull.

 

Note: I left out a key part of this -- getting the right pivot bolt out was one of the worst jobs I've ever had to do on a bike -- the bolt had serious locktite on it, and the threads in the tranny case (the R11 swingarm pivot location) were fine/weak. It took a huge amount of heat (while still trying to not overheat the tranny case and cause the magnesium to suddenly slump/melt), and even still, when the threads started to strip out, we had to immediately stop. We finally ended up demmel out the *entire* pivot bolt from the center out. After something like 7 hours, we finally got it cleaned up and reassembled with a new pivot bolt.

 

Anyway, a long story, but the point is moving the swingarm to the right can address a PTTR problem -- but you must consider what you might be getting into. The job shouldn't be as much of a problem on a bike with the swingarm pivots in the frame instead of the tranny, but that is not the only consideration -- for example, you need to make sure that there's enough clearance to move the swingarm over while not interfering with frame parts, wheel clearance, etc.

[DrPaul]

PTTR? FWIW, TADT! DAMHIK ..... LOL!!!

[Polo]

According to the Mayan calendar it will take care of itself on 12/21/2012.

[Edgar]

It sure makes taking out the shim on rear wheel of the 1100 seem like an easy fix for PTTR.

[T__]

Edgar, if it really does fix it?! I tried removing the 2mm rear wheel shim on my 1100 & couldn’t tell the difference in PTTR.. I also tried it on my 1150 by using a worn brake pad to offset the 2mm lateral wheel/brake rotor movement & couldn’t feel the change in that either.. If it helped at all on my bikes it was such a small difference it wasn’t really noticeable.. Maybe if a person could move BOTH the front & rear 3-4mm it might help & removing the shim is directionally correct just not enough..

 

 

Twisty

 

[Edgar]

I can tell you in my case on an 1100 it made a difference. I cannot tell you why it did not make a difference in your case, but with everything the same with the spacer in it PTTR and with it out the bike ran straight. The point of the comment is that pulling the spacer might be the first thing that one try's to lessen PTTR in an 1100. If it works, as it did in my case, fine if it doesn't then you move on.

[T__]

Edgar, did you JUST remove the spacer or did you install a new tire or tires at the same time?

 

 

Twisty

 

[Edgar]

30,000 miles ago I just removed the spacer to see if it made a difference, as it's so easy to do. The only change I made at the time was to remove the shim. It made a difference then so I never went back to it. I did put it back in 10,000 miles ago on a tire change to verify that in fact it made a difference. I changed the tire replaced the shim rode it for 3 miles, pulled the shim, and by golly the PTTR was gone again.

[Paul Mihalka]

My PTTR experience: My '99 R1100RT was a extreme right puller. First took out the shim behind the wheel. It made a difference but not enough. Then using a 2 mm spacer under the right swing arm pivot moved the swing arm over to the right. That cured PTTR completely.

[mneblett]

My PTTR experience: My '99 R1100RT was a extreme right puller. First took out the shim behind the wheel. It made a difference but not enough. Then using a 2 mm spacer under the right swing arm pivot moved the swing arm over to the right. That cured PTTR completely.

I should have mentioned in my post on the previous page that I also removed the wheel shim. Same results as Paul -- it helped, but the 3 mm shim under the pivot bolt head was still necessary to completely cure the PTTR.

[tazplas]

Sounds like it's all very normal really.

It's not something i am worried about, just curious.

Apart from the PTTR which is only noticed in 'hands off' situation, all is well with my RT.

 

Thanks for the info.

 

Cheers

 

Steve