Wobble/occilation at 70/75mph+, am i expecting too much from old bike?

[sgborgstrom]

I went back and re-read your original post and noticed you have the shock pre-load set at soft and your problem appears to occur after riding over something that makes the shocks work. Tightening up the pre-load might take some of the wobble you're feeling.

My F650 Dakar is quite sensitive to how much crap is in the saddle bags and and what I set the shock to. I always have to jack up the pre-load with the bags loaded or I get a wobble very similar to what you described.

 

[rdalland]

Ignorance is Bliss.

Also, is it possible to remove to wobble from these SWB bikes? Or am I going to die for sure at 75mph+?

I've been flying around the country at higher than "high speed (75 mph)" speeds for 20 years on my '71 R75/5. I've never experienced a wobble.

Thank God for the Internet.

I guess I better leave it in the garage from now on.

 

[APEXERIC]

Knowledge is Power

I've been flying around the country at higher than "high speed (75 mph)" speeds for 20 years on my '71 R75/5. I've never experienced a wobble.

Thank God for the Internet.

I guess I better leave it in the garage from now on.

Thank God for the internet is right. So I CAN get this sorted out. I guess I better get in the garage and get my bike back on the road!

 

[Bill Burke]

I have seen more than one /6 sub-frame with a cracked weld on the crossmember just in front of the rear fender. On one bike, it was impossible to see and was only discovered when dropped on the garage floor and made an unusual sound. The owner of that bike said it was un-stable at highway speed.

This is important. In addition to the measures you intend to take, double-check the subframe for a hairline crack in the paint. Just aft of the old mount locations for the old panniers. This was a stress point, and the crack won't show on a quick glance. Easily repairable by a good welder, but will cause the instability you report. I know this because I experienced it with my /6.

 

[KHEEREMA129911]

Initial Results

First of all, thanks everyone for your advice, this board is very helpful for bmw nubies like myself!

Yesterday I installed a new mastercylinder brake switch, and also the lift off seat mod to cure a broken seat hinge, both successfully.

I also really cranked down on all the subframe bolts, and the shock mounting bolts/nuts and went up one notch on the Koni rear shock preload settings (previously set at zero). The bolts were not loose, but I was able to really crank down on them, and I was able to tighten up a bit.

My test ride into work this AM resulted in positive results. I could not exceed 70mph, due to traffic/cops on those darn new fangled BMW's, but I believe I percieved some additional stability over some pavement changes, and just doing a few lane changes. i didn't feel the rear suspension was overly harsh, it really didn't feel that much different. I did feel less side to side motion over a stretch of crappy contstruction pavement I usually am forced to frequent that usually gives me quite a bit of side to side motion after/during the suspension absorbs the bumps.

I've also noticed recently that when in slow speed cornering leaned over, like 20mphish or slower, making relatively sharp turns, the front tire seems to "understeer", meaning the front of the bike kind of swings wider than I'd like it to or am directing it to, and I get kind of a vague feeling from the front end. This is not confidence inspiring, and I have been hesitant to corner like I'd like to because if feels like the front end is going to wash out. I've wondered if this is a BMW trait as I'm new to the brand and haven't ridden with any other bimmerheads. I only had one corner to really test this out this AM, and I think it felt better, but I'll have to ride some more to really be able to tell if my preload changes and subframe torquing has solved the problem. either way, I will get around to the steering bearing maintenance as I'd feel better (especially as current usage is daily commutting for this bike) knowing everything on the bike has been serviced and gone through. I have the "go" worked out, also the "stop", now suspension/handling!!!

I have checked the subframe over visually, and the crossmember in front of the rear fender, and did not see any visually detectable cracks/breaks in the frame. Tapping it does not create sounds that would evidence a fracture.

thanks all

 

[ebeeby]

I'm having the same problem with my 71 R60/5 but mine begins to wobble at 30mph and disappears at 35mph+.

I put new Metzlers on the front and rear hoping that the wobble would go away. But it didn't.

My head bearing seems ok but I'm going to take it apart to grease it and reset it.

If that doesn't work then I am going to replace the fork oil and probably replace the springs.

I don't mean to hijack the thread but I think that my questions are related.

There are three types of fork springs listed in Bob's catalouge: standard, heavy duty and Progressive.

What type should I consider to order for replacement? And, is it necessary to replace the rear shocks at the same time?

Hey, this might be getting expensive!!

Also, is it possible to remove to wobble from these SWB bikes? Or am I going to die for sure at 75mph+?

I am still relativly new to this compared to many of the members here at MOA so any advise is appreciated.

Thank you.

Eric

You need to read up on the SWB /5 wobble scenarios. BMW finally admitted to the problem and delivered a fix - to lengthen the swingarm - in 1973 1/2.

Good info here :

http://www.w6rec.com/duane/bmw/wobbles.htm

 

[dlearl476]

That surely could be the problems with an older /5, but not with the R90 that started this thread. That's a scary issue, for sure!

Nonsense, I've ridden both my properly adjusted and maintained R60/5 and R75/5 at 90+ and never had that issue. Something needs tending.

 

[dlearl476]

Also, is it possible to remove to wobble from these SWB bikes? Or am I going to die for sure at 75mph+?



Eric

For one thing, how's your steering dampener?

 

[APEXERIC]

You need to read up on the SWB /5 wobble scenarios. BMW finally admitted to the problem and delivered a fix - to lengthen the swingarm - in 1973 1/2.

Good info here :

http://www.w6rec.com/duane/bmw/wobbles.htm

Yes, I have read those articles. My question is: If I perform the frok aligment procedure and replace the springs am I still going to have a wobble? Or do I find a 1973 1/2 for sale and eliminate all of the hassle?

This particular bike has been a PITA since I purchaced it. This front end wobble is just an other item in a long list of stuff that was wrong with this bike. I really feel like selling it and starting over with something else.

I have replaced the rusty bars, fixed the stripped mirror mounts, replaced the cables, fixed all of the stripped out drain hole threads, replaced the torn drive shaft boot, new tires, etc. Now I need to sort out the front end wobble.

It seems like I work on this bike more that I ride it. I would really like to keep it but not if I can't get the wobble out of it.

So do all of the pre 1973 1/2 bikes have front end wobble regardless of thier alignment and suspension settings?

 

[testinglogin]

Nonsense, I've ridden both my properly adjusted and maintained R60/5 and R75/5 at 90+ and never had that issue. Something needs tending.

I agree it's likely something needs some work. The way I was thinking it didn't come out correctly; I should have typed it more like:

That surely COULD be the problem.... (but not saying that it is).

I'm waiting to hear back and see what the end result is!

 

[APEXERIC]

Nonsense, I've ridden both my properly adjusted and maintained R60/5 and R75/5 at 90+ and never had that issue. Something needs tending.

Yes, see that is the information that I am looking for. If it is possible to eliminate the wobble through proper repair and maintenence then I will take care of it.

As far as the steering dampener goes, the one on my bike was not working properly. It was not tightning down sufficently.

It is my understanding that the steering dampener was not the correct way to eliminate the wobble.

Whaterver the case I still need to go through the head bearings and investigate the fork for stiction and alignment.

Apologies to kheerema for hijacking the thread.

 

[SEMUTA]

In all honesty, how many people are running /5's with no problems? Many. I just threw that out there as something to confirm: that your forks were aligned properly.

My bike needs a lot of work also, but I view it as a learning experience (of which I need many). Plus, everything I replace/fix now is one less thing to replace/fix later.

 

[flash412]

I put about 70k miles on a short wheelbase R75/5, much of it two-up, most of it over 75 mph, some above 100 mph (indicated, WFO). I never understood that BS about the short wheelbase bikes having handling problems. My bike had Euro (short) handlebars which certainly would not have helped in a wobbly situation. Yes, I occasionally had problems with handling such as a low speed wobble when letting go of the handlebars below 40 mph. But I easily fixed handling issues with new or re-lubed/readjusted steering head bearings or wheel bearings. I guess the folks who complain about the short wheelbase bikes as being unrideable are the same folks who don't know which end of a screwdriver is the handle. Proper maintenance is key.

 

[APEXERIC]

Semuta and flash412,

Thank you for the input and advise. Just a long I know the issue can be solved then I can fix it.

 

[KHEEREMA129911]

Apologies to kheerema for hijacking the thread.

No problem apexeric, hey, I'm even learning stuff, even if it isn't about my particular model BMW. Hijack away. I'm just glad I didn't end up with a problematic bike, or have to worry about a tendancy to wobble for a particular year bike/model, true, or untrue. I really bought my bike because of the condition/900cc/wanted oppossed aircooled engine/disk brake, but I could easily have ended up with an earlier 750. Next time I buy, I will research more, but I guess I didn't do too bad with a '75 r90!.

I guess there is a lot of value in having a real bmw rider "airhead" check out/ride your bike, I"d love to have someone take out my beast for a flogging, then report back to me what they thought. I'm just concerned I'm asking for too much from this bike, but from several of the responses on this thread, riding 75-90mph is not impossible on these bikes (maybe foolish though ) either way, until i service the steering bearings and maybe stiffen up the front end with progressive springs, I won't know!!!

 

[testinglogin]

No problem apexeric, hey, I'm even learning stuff, even if it isn't about my particular model BMW. Hijack away. I'm just glad I didn't end up with a problematic bike, or have to worry about a tendancy to wobble for a particular year bike/model, true, or untrue. I really bought my bike because of the condition/900cc/wanted oppossed aircooled engine/disk brake, but I could easily have ended up with an earlier 750. Next time I buy, I will research more, but I guess I didn't do too bad with a '75 r90!.

I guess there is a lot of value in having a real bmw rider "airhead" check out/ride your bike, I"d love to have someone take out my beast for a flogging, then report back to me what they thought. I'm just concerned I'm asking for too much from this bike, but from several of the responses on this thread, riding 75-90mph is not impossible on these bikes (maybe foolish though ) either way, until i service the steering bearings and maybe stiffen up the front end with progressive springs, I won't know!!!

If you want to bring the bike up to Toledo, I'll be happy to take it out for a spin.

75-90 is NOT impossible, at all. My R80/7 is really happy at 75-85. I did 700 miles from the VT rally home, and most of the slab riding was around those speeds. They'll run all day like that. They WILL go faster if you want them to... I've heard.

 

[mikea]

kheerema-

I have a '92 R100R and began to have similar problems last summer. It just felt vague and wobbly in corners (mostly at >60 mph or so). I got a lot of good suggestions here as have you. I made some adjustments - the most effective of which was reducing rear preload slightly per The Veg ( Fox shock). This seemed to stabilize the bike.

However, the biggest improvement for me came from reading Lee Parks' book and analyzing my lack of technique. Not saying there's anything wrong with your's mind you.

Anyhoo, I ride a dirt bike and I realized that I was carrying over habits from dirt to street. I'm not very good at either, and now I was getting the worst of both! I was weighting the outside peg in turns. Worse yet, I was holding my torso upright in turns when I should have been leaning farther into the turn than the lean angle of the bike. Good technique for dirt-not for street.

Don't know if this helps, just food for thought.

mike

 

[ebeeby]

I put about 70k miles on a short wheelbase R75/5, much of it two-up, most of it over 75 mph, some above 100 mph (indicated, WFO). I never understood that BS about the short wheelbase bikes having handling problems. My bike had Euro (short) handlebars which certainly would not have helped in a wobbly situation. Yes, I occasionally had problems with handling such as a low speed wobble when letting go of the handlebars below 40 mph. But I easily fixed handling issues with new or re-lubed/readjusted steering head bearings or wheel bearings. I guess the folks who complain about the short wheelbase bikes as being unrideable are the same folks who don't know which end of a screwdriver is the handle. Proper maintenance is key.

Well, lots of interesting thoughts there.
I cannot recall anyone in this thread or the links in this thread saying that SWB have handling problems - in fact just the opposite as it was implied that they are "quicker" in their handling.
Heck, I have a SWB 1971 R50/5 and it doesn't have any handling problems.

But the SWB wobble was and is a very real and dangerous problem on *some* SWB airheads. Let me repeat: *some* SWB airheads. Duane and company found a solution in a precision fork alignment but BMW did not - they lengthened the swingarm at 1973 1/2. They did this in response to a well documented and perhaps fatal problem not because they couldn't come up with the right end of a screwdriver.

 

[pmdave]

Sounds like steering head bearings. Tapered rollers used on BMWs need correct preload to keep them snug, and of course, periodic cleaning and regreasing. If you haven't overhauled the steering head bearings for a long time, just do it.

What you may discover is that the bearing races are notched from the rollers pounding in the same locations with inadequate preload. The only fix is to replace the races and rollers, top and bottom. That requires pulling the upper triple clamp and dropping the front end out the bottom to get at the bearings. Obviously, you want to remove the gas tank to get it out of the way.

The lower roller bearing must be pressed off the steering stem. The upper bearing just slips off the top. The races are difficult to remove because they are a press fit in the steering head. It's possible to tap them out with a sharp drift, or to pull them out with a special puller. The shade tree easy removal trick is to draw a bead on the race with a welder, which shrinks the race as it cools.

When you're ready to install the new races, it helps to chill them in the freezer for an hour or so, which shrinks them slightly. I use a long piece of all thread--say 1/2" dia and the old bearings to pull the races into the holes simultaneously. Then I grease the new rollers well before putting it all back together.

Preload on the bearings should be so that the front end will rotate from center to either side over about one or two seconds--not an instant clunk. If it seems a bit reluctant to rotate, loosen the nut slightly. If it clunks over to the side too quickly, tighten the nut slightly. You'll discover that as you add the locknuts, covers, etc. the clearance may change slightly.

Since the primary purpose of a steering damper is to prevent rapid oscillations of the front end from side to side, you might want to re-evaluate your dislike of a steering damper. Personally, I like adjustable hydraulic dampers, so I can set the damping for the conditions.

pmdave

 

[dlearl476]

Good info here :

http://www.w6rec.com/duane/bmw/wobbles.htm

+1

And if it's not the usual (easy) suspects, do this:

http://www.w6rec.com/duane/bmw/fork/title.html


With a 30+ year old bike, chances are someone, somewhere, got the forks back together askew.