Author Topic: Steering "weave" (Read 18460 times)

conybeare · « **on:** May 31, 2011, 07:41:15 PM »

Hi All,

Just replaced the steering head bearings on my 1990 K75S. Now that I'm paying extra close attention to the steering, I've noticed that the bike likes to weave back and forth. If I go straight at a constant speed, it will fall to one side, then fall to the other slightly harder, then fall to back to the other side even harder, and so on. It doesn't just fall to the right as I remember my old K75C doing, or as I've heard most K bikes do. This may have been going on before the steering head bearing replacement, but I'm not sure.

I've got the bearings adjusted properly (or so I think), although I did notice that this problem was worse when the bearings were somewhat too tight (I first noticed this as I was trying to dial in the bearing adjustment).

I think my rear shock badly needs a rebuild or replacement, but I can't see that causing this issue. Also, I've taken care to install the forks and fork stab properly.

Any thoughts? Could this be related to a wheel bearing? Something about the forks? This isn't really a "problem" in that slight pressure keeps the bike straight - but it is somewhat unnerving knowing that it wants to weave back and forth when it should just fall to the right... Any help would be much appreciated.

frankenduck · « **Reply #1 on:** May 31, 2011, 07:58:33 PM »

One possible culprit is your front tire. Wear pattern? Over-inflated? What tire are you running, how many miles? How many PSI?

conybeare · « **Reply #2 on:** June 01, 2011, 11:15:08 AM »

Just check the tires and they look good. They both have around 3k on them. They're at 32 (F) and 36 (R). Lasertec front and Marathon rear...

I took a closer look at the forks this morning and the right one is slightly lower than the left - I swear they were level last I looked... I'll level the fork legs out and see if that helps.

conybeare · « **Reply #3 on:** June 01, 2011, 04:49:34 PM »

Re-leveled forks, made sure axle is sliding through smoothly, and made sure fork brace was aligned properly. Still having the steering weave...

Any other suggestions??? ???

frankenduck · « **Reply #4 on:** June 01, 2011, 04:57:37 PM »

Try a few pounds more and a few pounds less in the front tire. What's the rated max PSI for one of those. (Says on the side of the tire.)

johnny · « **Reply #5 on:** June 01, 2011, 04:59:28 PM »

greetings conybeare...

is it more a wobble than a weave... is it looking to go full lock to full lock if you take your hands off the bars...

j o

conybeare · « **Reply #6 on:** June 01, 2011, 05:10:24 PM »

I'll try adjusting tire pressure... Max is 42 F and 50 R.

It is definitely more of a weave than a "head shake", although it does not go completely lock to lock (I'm assuming you mean all the way to one side) - although if I let it swerve back and forth, I think eventually it would go lock to lock. It starts out as kind of a normal feeling fall to the right, but then it always goes back left, then back right, and so on. The turns from side to side get wider and wider until I put pressure back on the bars.

Inge K. · « **Reply #7 on:** June 01, 2011, 08:03:49 PM »

This could be related to the "fluidblock damper" beeing disturbed during renewing the bearings, or it needs to be cleaned and repacked.

Inge K.

conybeare · « **Reply #8 on:** June 01, 2011, 10:28:02 PM »

When I replaced the steering head bearings, the steering damper had very little grease but I didn't have any of the specified grease on hand - so I left as is.

I could try renewing the grease next time I'm motivated drop the forks. Anyone had luck finding any grease for the steering damper? Or any luck with substitutes? I've read that the BMW grease is no longer sold. I would just replace the damper but I don't think that's doable without removing one of the steering head bearing races...

Tried messing with tire pressure, but no luck... :-\

johnny · « **Reply #9 on:** June 01, 2011, 10:41:55 PM »

greetings conybeare...

so you are not sure this was happening before you messed with the steering head bearings... so im kinda inclined to think it wasnt happening or you would have likely noticed it...

with that said... i can tell you of 2 wobble issues i had in the past...

1 - rear tire with just 3000 miles on it lost sidewall integrity causing the front end to wobble... matthais dobner of long beach ca... a bonofide motobrick specialists who was on the original k-bike design team in germany and motobrick genius knew what the problem was by watching me push the bug into his shop... i thought he was crazy but he was absolutely right...

2 - new set of tires... front tire with less than 50 miles on it had a defective internal radial caused the front end to wobble... a new front tire solved it... freaky...

those are my only 2 wobble issues... probably no help... butts thats all i gotts...

j o

frankenduck · « **Reply #10 on:** June 01, 2011, 11:18:39 PM »

Quote from: Inge K. on June 01, 2011, 08:03:49 PM

This could be related to the "fluidblock damper" beeing disturbed during renewing the bearings, or it needs to be cleaned and repacked.

Inge K.

Interesting post. I'd always taken that damper for granted and never gave it much thought - that is until I built my Frankenbike with a K1100 front end. Since the stem between the upper and lower fork tress is narrower than the K75/K100 one the bike effectively doesn't have a steering damper. It's pretty noticeable at low speeds (under 5 mph) as the front end tends to want to go wherever but once I get up any speed the instability goes away - I suspect due to being overridden by the angular momentum of the front wheel. I'm curious to know why you think that might cause the weaving Dan is experiencing.

Inge K. · « **Reply #11 on:** June 01, 2011, 11:23:28 PM »

Quote from: conybeare on June 01, 2011, 10:28:02 PM

I've read that the BMW grease is no longer sold.

It looking like the company that did deliver the grease still produces it, but sorry no
distributor list on their web page.
http://www.fuchs-lubritech.com/cms/spip.php?page=produkt&id_rubrique=21&id_produkt=4176

Inge K.

conybeare · « **Reply #12 on:** June 01, 2011, 11:54:19 PM »

I'm curious to know why you think that might cause the weaving Dan is experiencing.
[/quote]

I had a similar thought - not sure why that would cause the steering to actively change direction. It seems like a faulty damper would lead to the steering more inclined to fall to one side or the other, but not go back and forth...

I'm starting to think rear shock more and more...

Inge K. · « **Reply #13 on:** June 02, 2011, 12:14:54 AM »

Quote from: frankenduck on June 01, 2011, 11:18:39 PM

I'm curious to know why you think that might cause the weaving Dan is experiencing.

It just dropped into my head when reading the thread, and knowing that 75`s got a
factory fitted damper.
And the fact that the bearings beeing changed.....it could have disturbed the damper.

Just throwing in an idea of a another possible reason for the problem.....and giving
the owner more headaches.

Was thinking in the direction of varying friction, and much less friction when just in
center.....and this starting the pendelum effect......like when steering stem ballraces
being worn just in center position.

It must be some reason BMW added a damper only on the 75`s.........and then it
maybe have to function properly.

Inge K.

frankenduck · « **Reply #14 on:** June 02, 2011, 08:06:48 AM »

Quote from: Inge K. on June 02, 2011, 12:14:54 AM

It must be some reason BMW added a damper only on the 75`s.

Well, my K75 effectively doesn't have one since the stem between the forks is thinner than a K75 one. The only difference I notice is that the front end is wobbly at low speeds. Once I get above about 5mph though it rides just fine. So my guess is that the damper is there to stabilize the front end at low speeds.

I'm inclined to the that the problem here has something to do with the front tire if the forks aren't bent and are in proper alignment. I guess the only real way to tell would be to replace the front tire.

frankenduck · « **Reply #15 on:** June 02, 2011, 12:16:15 PM »

Dan:

I saw a post elsewhere where someone attributed weaving to a bad rear shock. Maybe that's causing yours.

conybeare · « **Reply #16 on:** June 02, 2011, 05:50:25 PM »

Took the rear shock off today and called Progressive to ask about a rebuild. They don't even have the parts! They're only suggestion was to buy a new one... I just bought a 2nd hand shock from eBay. If that changes the weave at all, I'll suspect the rear shock and order a actual new shock.

I may also just take it in, unless anyone has any other suggestions. I'm assuming they could at least tell me if it's one of the tires (or, anyone in the Chicago area want to swap front wheels for about 15 minutes?? ;)). I suppose they could also check the forks.

Here's how I aligned the front forks:

Evened top of fork tubes and tightened down top fork tree bolts. Pumped forks up and down. Tightened axle bolt. Pumped forks. Tightened lower fork tree bolts. Pumped forks. Tightened fork brace. Tightened axle clamp bolts. If I did that wrong, suggestions would be appreciated.

Argh, this is driving me nutso.

conybeare · « **Reply #17 on:** June 02, 2011, 07:12:26 PM »

OK - this seems to be more sensitive to tire pressure than I first thought. I tried experimenting with drastically different pressures than usual and it definitely changes the weave. I was able to lessen it by dropping the front to around 26-28. I also went down to around 20-22, and it actually made the bike want to pull left (as opposed to right first, then left). At that very low pressure, it was also harder to steer to the left than to the right.

Once I got as much weave out as possible (about 26 in front), I dropped the rear from 40 down to around 36, then 32, and that actually made it worse again, I'm assuming because it just offset the change in pressure up front.

Is this evidence that it's a front tire issue? The only other thing I'm thinking is that perhaps the change in tire pressure is just affecting the real problem (i.e., something else), but it does seem pretty likely that it's something with the rubber...

J.O. and Frankenbike - you may be on to something here...

gladstone · « **Reply #18 on:** June 05, 2011, 04:26:28 PM »

Hi there,

I'd say it's rear shock; do you have a top-box fitted? I had an unsettling weave above 75 mph on my LT, which reduced considerably when I removed the top-box. Disappeared entirely when I fitted a new shock (even with the top-box back on). I fitted a RAM shock from Realm Engineering in the UK.

Cheers

conybeare · « **Reply #19 on:** June 07, 2011, 12:28:49 AM »

Fitted the new-to-me used stock shock (w/ 20k) and the weave disappeared! The bike rides nice and straight now.

Many thanks to all for your input!

Bimmerman · « **Reply #20 on:** October 12, 2016, 07:51:03 PM »

Hello,

I thought I would try here to see if anyone is still watching this thread before starting a new one. I have a 1993 K100RS that is great and only has 30,000km on it. It rides and runs great but I noticed yesterday that if I take my hands off the bars at anything over 50km the front end starts to wobble. It's pretty bad but steady as a rock if I'm holding on. I've seen some of the suggestions but was wondering if anyone had had this problem and solved it. I will start messing with tire pressure today as mine is low. Any ideas or suggestions would be appreciated.

Laitch · « **Reply #21 on:** October 12, 2016, 08:32:10 PM »

Quote from: Bimmerman on October 12, 2016, 07:51:03 PM

It rides and runs great but I noticed yesterday that if I take my hands off the bars at anything over 50km the front end starts to wobble. It's pretty bad but steady as a rock if I'm holding on. I've seen some of the suggestions but was wondering if anyone had had this problem and solved it.

Are you taking your hands off the bike at that speed to curse in sign language or juggle?

How old are the tires? How many miles on them? Have you inspected them for cupping? Fill them to spec pressure, check the front for a missing wheel weight and try again.

Bimmerman · « **Reply #22 on:** October 12, 2016, 08:43:29 PM »

Thanks so much for the quick reply. I just wanted to see how balanced the bike was. I've noticed that there is a big difference with pull when I have the bags on. After checking everything I will get back to you. The tires have good tread and no cupping but they are not new I'm sure. The bike rides and handles great. I just thought the wobble might be caused by balance or some other issue. I thought if the wheel was out of balance it would shake at speed even holding on but no problem there.

I probably should apologise for posting here as my problem isn't weave but wobble. Again thanks for the comeback and the things to check.

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Author Topic: Steering "weave" (Read 18460 times)