R12RT Rear-wheel (drive) play--how much?

[bobbybob]

OK, I guess I am sufficiently paranoid after reading some recent posts. I have been doing the "wiggle test" on both of my 07 R12RT's (his & hers) rear wheels for some time and both have *some* play. The 15K RT has a noticeable "clunk" when rocking the wheel between 6 & 12 o'clock. The 13K RT...not quite as much, but still a clunk. Neither bikes appear to clunk when wiggling between 3 & 9 o'clock. Why is that??? What causes the "clunk"? HOW do I measure the *amount* of "wiggle"? What amount is acceptable? What is not? At what point do I call the doctor? Any other "anomalies" I should be looking (or feeling) for that I am missing? Please don't tell me to "just ride and enjoy"....I'm already doing that. But not blindly...not any longer.

[gettysburg]

I'm sure someone will correct me if I'm wrong, but what you're feeling is driveline lash; which is normal. It's the free play between all the parts that make of the drive system.

 

The type of free play that may indicate an impending final drive failure would be felt by grabbing the wheel at the 3 & 9 o'clock positions and wiggling the wheel as if you where tyring to pry it off the hub.

[grasslander]

The type of free play that may indicate an impending final drive failure would be felt by grabbing the wheel at the 3 & 9 o'clock positions and wiggling the wheel as if you where tyring to pry it off the hub.

 

Measured as more than 3mm play or movement at the outer rim of the wheel.

[Beaky]

Any detectable sideways movement is cause for concern. I'm not sure what the exceptable play is but mine doesn't

have any detectable movement and certainly no clunk. My previous bike, an early 1200GS didn't have any sideways play either but a colleagues had 5mm play and the final drive was replaced under warranty. I'd get it checked by the dealer asap.

 

Drive line slack, which was reffered to is shown by radian movement of the wheel while in gear and is quite normal, even necessary and is the cause of a clunk when taking up the slack (e.g. when letting out the clutch).

[bobbybob]

The type of free play that may indicate an impending final drive failure would be felt by grabbing the wheel at the 3 & 9 o'clock positions and wiggling the wheel as if you where tyring to pry it off the hub.

 

Measured as more than 3mm play or movement at the outer rim of the wheel.

 

Whats the best way to measure this play?

And does wiggling it between 6 & 12 oclock not really indicate anything? I noticed you stated 3 & 9 oclock...?

[bobbybob]

Any detectable sideways movement is cause for concern. I'm not sure what the exceptable play is but mine doesn't

have any detectable movement and certainly no clunk. My previous bike, an early 1200GS didn't have any sideways play either but a colleagues had 5mm play and the final drive was replaced under warranty. I'd get it checked by the dealer asap.

 

Drive line slack, which was reffered to is shown by radian movement of the wheel while in gear and is quite normal, even necessary and is the cause of a clunk when taking up the slack (e.g. when letting out the clutch).

 

No, this is not drive lash I am referring to--I am well aware of what that is.

 

When you say "sidewise movement", do you mean the *entire wheel* can be moved left or right without "rocking" it between the 6 & 12 oclock positions? Mine will not actually "slide" left or right at all, but will slightly "rock" from top to bottom of wheel (but not from left to right).

 

And I'll re-state my earlier question: why can I rock the wheel from top to bottom but NOT from left to right?

[Albert]

And I'll re-state my earlier question: why can I rock the wheel from top to bottom but NOT from left to right?

 

I think the answer is obvious Bob. If you're worried about bearing play at the axle I'd say you likely eliminated that possibilty by detecting none in the 3/9 axis play. The fact that rocking occurs on the 6/12 axis would indicate a different mechanism is at work.

 

I think if you have an assistant watch the paralever mechanism as a whole while you move the assembly they will be able to determine where the movement is taking place. I could imagine a different response in different axes given the paralever geometry. As to what's "normal" I cannot say. If I can remember I'll give mine a shake when I get home to see what I have.

[grasslander]

According to my BMW dealer, 3mm is BMW's specification for allowable play checked cold. This would be any "side to side rocking" (perpendicular to wheel rotation). I check mine with a dial indicator on the rim at 12-6 and/or 9-3. Example: I grasp the wheel at say 12 o'clock (top) and 6 o'clock (bottom) and rock the top and bottom opposite of each other. If I would see any play I would remove the brake caliper and test again.

[drzep]

When I had a FD failure a couple months ago, I PM'd Ken H. and he gave me some advice on how to check it and what the play may indicate. I don't think he will mind so here is a snip of his replay:

 

"...here's the quickest way to decide where the play is coming from - If when you attempt to rock the tire/wheel by grabbing it at the 9 and 3 o'clock position and then at the 12 and 6 o'clock, if you feel play both directions, on both axis, it's likely a FD issue. In theory there should be no detectable play in both directions. I would keep a close eye on it, and then if it seems to be getting worse, a FD tear down is in order.

 

On-the-other-hand if you can detect play in the 9 & 3 o'clock direction, but not in the 12 & 6 o'clock direction, it is likely a swing arm pivot bearing issue. A couple of mm of play there is rarely a critical, 'must address now' issue. It will to some extent effect handling, but it one of those things that can be repaired at your leisure."

 

Hope that helps.

[CraigT]

I had the very same issue with my ST when I bought it, and got the run around from dealer telling me it was a 'characteristic' of the bike. Bullsh1t!

I had experienced a wobble on left hand bends since I got the bike. BMW released a tech advice note for the GS stating that 1mm of play was acceptable, but given that the bike wobbles, I rejected this. Eventauly BMW agreed to repalce the complete back end of the bike to solve the problem. This included the excessive free play on the rear end from the lower most 'movement joint' in the rear assembly. Dealer was poor, I got mine fixed via BMW UK.

Bike has now done 43k miles and the rear end is now leaking, so just like 'Bobbybob', I'll be getting that sorted out too.

 

I posted a discussion on this very thing about three years ago and got zero response. It's real and it is a failing on BMW bikes. NB, some of the K series I've riden also wobble on right handers!

[bobbybob]

When I had a FD failure a couple months ago, I PM'd Ken H. and he gave me some advice on how to check it and what the play may indicate. I don't think he will mind so here is a snip of his replay:

 

"...here's the quickest way to decide where the play is coming from - If when you attempt to rock the tire/wheel by grabbing it at the 9 and 3 o'clock position and then at the 12 and 6 o'clock, if you feel play both directions, on both axis, it's likely a FD issue. In theory there should be no detectable play in both directions. I would keep a close eye on it, and then if it seems to be getting worse, a FD tear down is in order.

 

On-the-other-hand if you can detect play in the 9 & 3 o'clock direction, but not in the 12 & 6 o'clock direction, it is likely a swing arm pivot bearing issue. A couple of mm of play there is rarely a critical, 'must address now' issue. It will to some extent effect handling, but it one of those things that can be repaired at your leisure."

 

Hope that helps.

 

 

OK, so it looks like 9 & 3 oclock wiggle = swingarm issues, and both 9/3 and 6/12 = FD issue. What about 12 & 6 oclock--only? That is where my play is, and so far no one has addressed this being the only wiggle...?

[FLTRI]

fwiw, I just went out and wiggled my 05 RT with 16K on it. I couldn't detect any movement at 3-9 or 6-12, and certainly no 'clunk'...

[bobbybob]

fwiw, I just went out and wiggled my 05 RT with 16K on it. I couldn't detect any movement at 3-9 or 6-12, and certainly no 'clunk'...

 

I hope you're right...but try it again just to be sure. This time, don't grab the wheel tightly at the top and bottom and jerk it back and forth, but very lightly, with 2 fingers on each position, caressing the wheel tenderly (don't get carried away ) and gently rock it. If you grab it tightly you won't feel the movement because it is really pretty slight...but still there. I could feel a very small amount when I had 3K miles, now its more. If you still don't feel it, then I guess you lucked up and got one of the "precision models"...limited editions, not many made.

[FLTRI]

Hmmmm, I gave her another wiggle, gently this time, and I still don't feel any movement... Well, maybe a tiny, tiny bit at 3-9, but if it's there it's very minor. I have a disk brake run-out gauge, tomorrow I'll go see if I can clamp it on somewhere and see if I can get a reading...

 

Funny that I'm now worried about not having a problem.

 

 

[grasslander]

According to my BMW dealer, 3mm is BMW's specification for allowable play checked cold. This would be any "side to side rocking" (perpendicular to wheel rotation). I check mine with a dial indicator on the rim at 12-6 and/or 9-3. Example: I grasp the wheel at say 12 o'clock (top) and 6 o'clock (bottom) and rock the top and bottom opposite of each other. If I would see any play I would remove the brake caliper and test again.

 

Sorry folks "3mm" should read "1mm"

[babalueb]

Hey, I just tried that with my 06RT (3,200 miles) and I got that little clunk at 12 and 6, but nothing at 3 and 9. I feel it, but can't see it. Tomorrow I will use a magnetic base on the brake disc and dial indicator and try to see where the movement is.

[grasslander]

Tomorrow I will use a magnetic base on the brake disc and dial indicator and try to see where the movement is.

 

I don't think that'll work. The brake disk is mounted to the alloy flange that is attached to the axle tube, which is carried by the FD bearings. You will need to find a spot on the bike frame or paralever to test wheel or flange play.

[gasser]

I, too, am starting to get paranoid about this rear-end problem. For an otherwise outstanding bike, I need to build my confidence that this bike can handle long trips without fear of an FD failure. The EWS thing I think I can prepare for. Am I naive to believe that after the 6,000 mile service and rear-end inspection that I', out of the woods?

[CraigT]

6-12 wobble on my ST was the lower most union joint at the rear end. Not the main bevel box. Place your fingers on the inside of the lowermost joint and you may feel the free play.

[babalueb]

Ok, set up the dial indicator and found that my very slight clunking is NOT the final drive. So it must be the pivot bearing. I'll be keeping an eye on this one. I also noticed that when I tried 6 and 12 from the right side of the bike I couldn't get any clunking. Go figure.

[Limecreek]

So it must be the pivot bearing.

 

Pivot bearing? Where is the pivot bearing in the R12 trailing arm?

[bobbybob]

6-12 wobble on my ST was the lower most union joint at the rear end. Not the main bevel box. Place your fingers on the inside of the lowermost joint and you may feel the free play.

 

Craig, can you describe exactly where this joint is?

[babalueb]

It's where the fd hinges. And that is where the movement is coming from. It's enough that I can just see it move.

[Albert]

OK I monkeyed with mine last night and could find no perceptable play in either axis. Maybe my touch is not light enough.

[smiller]

 

As was already mentioned some (up to 1 mm) play is considered acceptable by BMW. The hexhead final drive is different from the oilheads and there is no preload on the ring gear/crown bearing, possibly allowing the axle a small amount of float. (Or, as we are hearing, sometimes more than a small amount.)

 

[drzep]

so what is the difference between play at 12/6 and play at 9/3?

[bobbybob]

It's where the fd hinges. And that is where the movement is coming from. It's enough that I can just see it move.

 

I could detect absolutely NO movement in that joint on my RT. Maybe yours needs tightening.

 

Overall, I think I'm learning what DOES and DOESN"T constitute abnormal FD play. The 6-12 play seems to be there in differing amounts on different bikes--even my 2 RT's are different. But as Smiller stated, some play is allowable. That, coupled with the absence of 3-9 oclock play seems to say that things are probably pretty much normal. So I'll continue to monitor every time its on the center stand. I have no idea *HOW* much advance notice I would get of a FD failure, but maybe vigilance will pay off--who knows.

 

And as a final note of paranoia, I found that when I took my fist and hit the rear tire from the left side at the 12 oclock (and immed. let it bounce off), the wheel made a short but evident "rattle" as it rebounded within it's own "acceptable" tolerance. Not a comforting sound at all...but possibly completely normal.

 

(And to DRzep's question, it seems theres no consensus on that.)

[Albert]

Bob, I realize that with 2 RT's your chance of contracting final drivanoia is doubled. Please stop punching your bike though, it won't help.

[bobbybob]

Bob, I realize that with 2 RT's your chance of contracting final drivanoia is doubled. Please stop punching your bike though, it won't help.

 

Al, you're absolutely right. On the other hand, it also gives me an instant benchmark to compare whats going on with one against the other.

 

Oh--try punching your rear tire too. Just curious if you hear that same "sproinggg" sound.

[bobbybob]

OK, had the EWS ring recall done today, and also asked the tech to just feel the rear wheel while he's with it and let me know if it feels normal. For $8.50 I was told "Checked final drive and found no movement". Hell, for free I CAN find movement. $8.50 isn't a lot of money but you'd think they wouldn't charge anything for such a simple thing. Its like charging $12.00 to tell me I don't need any brake fluid....

[ScottT]

final drivanoia

ROTFL!