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General Category => General Discussion => Topic started by: Guzzi Gal on April 13, 2020, 11:09:02 AM
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Dear Guzzi Braintrust shut-ins,
I'm not in the habit of riding handsfree but I've been known to rest my clutch hand on my knee on relaxed stretches of road. Last week I decided to experimentally loosen my grip on both handlebars to not quite nil and immediately Anni's front end started to wobble. I settled her down and tried again with the same results. What's up? I'm much more curious than worried.
Additional info:
Anni is structurally bone stock
(modifications include: top-case that's usually empty, Agostini crash-bars, Dart 'Classic' flyscreen)
Tire pressures are spot on
Under 2k miles on the clock
(yes, I should ride her more)
No wobble riding one-handed
I'm a tear it down to see how it works kind of gal, but only with stuff I don't care about putting back together. I have ZERO mechanical knowledge beyond helping my dad work on our Bug when I was a kid. The wobble isn't an issue, as I don't hoon around hands-free, but I'm a proactive type and wish to head off any problems before they become expensive repairs or life-threatening.
On a side note; my Vespa suffers from a low-speed front-end wobble that happens during deceleration, usually starting at about 40 mph to around 30 mph. This is well documented among Vespas made around the same time as mine (2012). Without consensus, solutions range from mild to mad.
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even empty, a topcase catches a lot of wind and may contribute to un-weighting the front end enough to cause a little wobble
I think the general best bet is check your steering bearings for adjustment, esp if your tire pressure is correct and tire isnt worn/cupped
But IMHO if your steerer bearings are loose enough to cause the head shake hands-free, you would also have a bit of chatter/wobble on front-brake deceleration as well (esp under hard braking)
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I've had bikes exhibit deceleration weaving. Those same bikes that have electronic cruise control have no weave while in cruise control.
My V7III, with cast wheels, is rock solid when coasting with hands off the bars.
My suggestion would be to raise the bike so the wheels are off the ground. Spin the wheels and verify that they are spinning true. Do the wheel bearing and steering stem bearing check for looseness. See if the brake rotor is a little warped and periodically slowing as it spins through the relaxed pads. Make sure the forks are operating correctly with no sticky spots in their travel.
If all checks out try removing the trunk and changing your position on the bike and see if it has any affect on the weave or wobble.
Good luck.
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I have done a few hard brake tests in the past and she was well planted and straight. I've never had her become unsettled, until this experiment. The tires are in perfect condition, with chicken strips fully intact. I'm into enjoying the scenery and practicing proper lines in the twisties, not dragging elbows. I'll pop off the top-case and try it again.
If she still wobbles, I'll see about getting the front end off the ground and check for wobble. How does one check the wheel bearing and steering stem bearing for looseness?
I posted this pic recently on another thread. I think it gives an okay look at the tire condition.
(https://live.staticflickr.com/65535/49753369736_05c0996601_k.jpg) (https://flic.kr/p/2iNx2rA)
The Vespa does it under engine braking, but she stops true under hard braking. There are too many reports that replacing the bearings made no difference, so for now, I'm leaving 'er be. (https://flic.kr/p/2iNx2rA)
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try removing the top box see if goes away
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I have had this experience with numerous bikes in the past that if you let go of the bars at lower speeds to get that front end wobble. In fact my 83 Honda CB1000C just did the same thing the other day.
Back in the early 80s we had 81-82 Honda cb900c for police bikes at the WSPD. We had 14 of them dressed in full Vetter equipment and they all did the same thing. It was determined by the dealership the extra equipment was the cause as the front forks were reacting to the extra front end weight. For the most part adding a fork brace fixed the problem. Fortunately at higher speeds there was no wobble issues just when the bike got below around 30mph with no hands on the bars. So we were instructed to keep at least one hand on the bar at all times, duh:)
(https://i.ibb.co/9n8MC9P/0-EE6-B8-F1-034-D-4207-9-C6-B-B96-D94-C897-EF.jpg) (https://ibb.co/9n8MC9P)
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Dear Guzzi Braintrust shut-ins,
I'm not in the habit of riding handsfree but I've been known to rest my clutch hand on my knee on relaxed stretches of road. Last week I decided to experimentally loosen my grip on both handlebars to not quite nil and immediately Anni's front end started to wobble. I settled her down and tried again with the same results. What's up? I'm much more curious than worried.
Additional info:
Anni is structurally bone stock
(modifications include: top-case that's usually empty, Agostini crash-bars, Dart 'Classic' flyscreen)
Tire pressures are spot on
Under 2k miles on the clock
(yes, I should ride her more)
No wobble riding one-handed
I'm a tear it down to see how it works kind of gal, but only with stuff I don't care about putting back together. I have ZERO mechanical knowledge beyond helping my dad work on our Bug when I was a kid. The wobble isn't an issue, as I don't hoon around hands-free, but I'm a proactive type and wish to head off any problems before they become expensive repairs or life-threatening.
On a side note; my Vespa suffers from a low-speed front-end wobble that happens during deceleration, usually starting at about 40 mph to around 30 mph. This is well documented among Vespas made around the same time as mine (2012). Without consensus, solutions range from mild to mad.
Spoked rims? If so, Bill Hagan had a similar 'bobble' at 45-55 mph, after mounting a fresh set of tires, remounting, checking balance, etc, he ended up having the front wheel re-laced. All good now I believe. Check out the V7 thread in ADV.
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I’m not sure I’d bother looking to deep. If the simple stuff checks out ok, or if you determine it’s the top case, so what? Just ride it, it will be fine and don’t take both hands off the bar.
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Guzzigal You should be use to that with your Vespa. Before you go tearing a lot of stuff apart take your top box off and try leaning front on htte tank kind of playing ricky racer.
Sounds like a weight distribution/dynamics problem to me
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Steering head bearings are loose.
I know, they are adjusted to spec. That is too loose. Tighten them until they affect steering and then back off just a bit.
BTDT.
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IMHO I’d try the top box first . I’ve not had one on my V7 but had one on my other bike (R1200r) for about 50 Mi. @ highway speeds it was disconcerting .
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If I read it all right GG's problem is head shake. Bills was more a thump like out of balance or round.
check the bearings as stated. my bet is the top box it sticks way back there like a para sail and I think the mfg design them to be used as a final piece of equipment with the saddle bags full. not used stand alone.
now when your all done I'd drop the front end 10-15MM and I bet that fixes it too and the handling will be better. only takes 5 minutes.
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Steering head bearings are loose.
I know, they are adjusted to spec. That is too loose. Tighten them until they affect steering and then back off just a bit.
BTDT.
THIS^^^^
Check them after removing the top case.
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The only thing a top case can/will do, is mimic the presence of a small passenger.
If your bike is exhibiting a tendency as you say, it means the oscillation present in all two wheeled countersteering vehicles is increasing in amplitude...(getting bigger).
I reckon your first course is to check the rims for run out as you said and have them remedied if necessary GG.
Then get a really good balance job done...(you must do both)
It’s possible to have an out of true wheel nicely balanced, such that it will appear perfect when checked for balance, but give problems when spinning.
These things are beaut..
https://youtu.be/RcIi5EUwDRo
It sure as hell wouldn’t hurt to check the headstem races for cleanliness and lubrication, then tension them appropriately.
You’re gunna’ be ok then..
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I have a new V7iii, I don't have the confidence to let go the bars as I can do on my Griso, some bikes just don't feel as planted.
Given that it's less than a year old and kept indoors the steering should still be ok, the wheels are certainly running true.
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You say that tyres pressures are spot on - but what pressures are you using?
On the Mk I, MG give the same pressures for both wheels but many people run with a little more in the rear wheel as it carries more load.
AndyB
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You say that tyres pressures are spot on - but what pressures are you using?
On the Mk I, MG give the same pressures for both wheels but many people run with a little more in the rear wheel as it carries more load.
AndyB
The manual says 36.26 PSI for both. I keep them between 36 and 36.5 and that's what they were at the time of my original post. That said, my mechanic suggested 34 for the rear so sometimes I'll let the rear drop to that before topping off. He is a former AMA racer and was recommended by several Guzzi geeks from here and MGOC so I'll assume he knows what he's talking about.
As far as carrying a load, beyond the top-case its self, I rarely do. I use it for storing my helmet, jacket and gloves whilst I walk around.
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Lower pressure in the rear tyre than the front? That is the wrong way around.
On my V7 I use 36 rear / 32 front when solo, maybe 2psi extra in each when dual. Tyre pressures need to be higher when there is more weight on a wheel to maintain the same sidewall deflection. Otherwise the tyre can overheat.
My other bike, a BMW R100R was very sensitive to tyre pressures with the original bias tyres - and would gently want to wobble the bars if riding one handed and the tyre pressures were not spot on 36 front / 42 rear. It is much more tolerant now it runs on radials.
My V7 had Pirelli Sport Demons from new which are also bias tyres - which looks like what you have. Without wanting to start a tyre thread, modern radials do seem to be better than bias tyres in many ways, and when you come to changing tyres a move to radials may help stability.
Andyb
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Lower pressure in the rear tyre than the front? That is the wrong way around.
On my V7 I use 36 rear / 32 front when solo, maybe 2psi extra in each when dual. Tyre pressures need to be higher when there is more weight on a wheel to maintain the same sidewall deflection. Otherwise the tyre can overheat.
My other bike, a BMW R100R was very sensitive to tyre pressures with the original bias tyres - and would gently want to wobble the bars if riding one handed and the tyre pressures were not spot on 36 front / 42 rear. It is much more tolerant now it runs on radials.
My V7 had Pirelli Sport Demons from new which are also bias tyres - which looks like what you have. Without wanting to start a tyre thread, modern radials do seem to be better than bias tyres in many ways, and when you come to changing tyres a move to radials may help stability.
Andyb
Are you sure tubes in radial tires is a good idea?
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As I recall it looks like u don't weigh 90#. 32-33 in the front is plenty.
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Both my bikes have tubeless wheels as standard - the BMW has spokes that go to the edge of the rim and my V7 has cast wheels - so no tubes are used.
But I guess GG’s V7 will have tubes as it has spoked wheels....does that preclude the use of radials?
Just one other thought - Tyre pressures should be measured and set before the bike is ridden, ie with a cold tyre. If they are measured after riding the bike the tyres will be underinflated.
Good luck solving the wobble and do report back when you have sorted it
AndyB
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I've been reading this and have to wonder: I had a Triumph America that did what GC describes for 14000 miles with no ill effects to me or the bike. I simply kept two hands on the bars-no extra pressure or effort needed. My Rocket III would wobble with no hands from 40 down to 30 and ZERO was out of sorts. It did that thru 4 sets of tires.
I'll take my V7 out next week and see what it does with no hands. How about others do that also and lets see the results. Or have you already?
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If the bike is showing a tendency for this behaviour, then it’s asking for help.
Sure, we all know that holding onto the ‘bars with at least one hand will (mostly) dampen any tendency for a tank slapper, but the aforementioned “tanky” is an unstable condition and once it starts, if it’s serious enough it’ll increase in amplitude and the forces of hell won’t stop it spitting you off.
https://youtu.be/TpeNWxHF6uI
The go is to do the checking and when everything is ok, then learn to adapt, but not just “make sure you never let go”...
If GG let’s go with her left hand one day on a rough road to attend to a bee that’s gotten inside her helmet, she may end up not being the most attractive photo of our membership any longer...
No one wants that.. :clock: :bike-037:
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For what it’s worth (not much?): V7II, cast wheels. I often remove both hands while riding. No wobble except when I had a fresh new 80/20 rear working with an older front street tire.
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My thoughts would be:
Check the steering head bearings
Out of balance front wheel.
Rear swingarm bearings not quite tight enough on the adjustment. (probably unlikely)
As a thought, jack the front up so it spins easily and spin the wheel while runnibg say a spanner against the spokes. listen for a dull tink amongst the high pitched sounds. Could indicate a loose spoke which could cause an out of round wheel.
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While all of the mechanical things are good and important to check. I also found that going to the 'optional' 110 wide front tire stabilized things as well as switching tires. The front with the OEM Pirelli bias tires just never felt planted to me.
I also keep coming back to the tail pack and weight distribution. My experience is that even unladen a tail pack can catch the wind and lighten the front end which could cause a wobble. Unlike a pillion who is right behind the rider the pack has enough of a gap that it doesn't slipstream. I also experienced problems when putting too much weight behind the rear wheel axle line.
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One way to find out about the air pressure on the tires especially the front. Pump it up to max on the sidewall. Go out and do the "test". If it still does the problem then could be the steering neck bearings or the box or the swing arm bearings. If it is low air pressure. Pump both of your tires to just below max on the sidewall.
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The manual says 36.26 PSI for both. I keep them between 36 and 36.5 and that's what they were at the time of my original post. That said, my mechanic suggested 34 for the rear so sometimes I'll let the rear drop to that before topping off. He is a former AMA racer and was recommended by several Guzzi geeks from here and MGOC so I'll assume he knows what he's talking about.
As far as carrying a load, beyond the top-case its self, I rarely do. I use it for storing my helmet, jacket and gloves whilst I walk around.
I always start with the stock pressure and adjust. I mostly commute on the V7 and ended with #30-32 F 36 R. This slowed down the front made the it less twitchy and better planted. Granted this is for city, town and neighborhood. When taking on longer trips or loaded, I'll go to 36f & 38r.
It cant hurt to pull the top box ro see it it changes the sensation. Also good idea to chexk steering head. Start with the easy.
Not sure if you said or someone asked, but how is the wear on the tire?
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Thanks for all your suggestions! :bow:
If after removing the top-case the problem persists, I will check the spokes (watched https://www.youtube.com/watch?v=9eOKzknv-TE ) and bearings (watched https://www.youtube.com/watch?v=zQJhcfdsWTk among others). Additionally, I've always checked tires cold. I also find running the front pressure a few pounds lower negatively impacts my ability to steer. They only have about 1600 easy miles on them so, in theory, they should be excellent condition.
Any ideas on how to lift the front end safely without a lift, jack or center stand? :gotpics:
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Thanks for all your suggestions! :bow:
If after removing the top-case the problem persists, I will check the spokes (watched https://www.youtube.com/watch?v=9eOKzknv-TE ) and bearings (watched https://www.youtube.com/watch?v=zQJhcfdsWTk among others). Additionally, I've always checked tires cold. I also find running the front pressure a few pounds lower negatively impacts my ability to steer. They only have about 1600 easy miles on them so, in theory, they should be excellent condition.
Any ideas on how to lift the front end safely without a lift, jack or center stand? :gotpics
If you are going to do your own diagnosing, invest in one of these. https://www.amazon.com/gp/product/B01860HLCU/ref=ppx_yo_dt_b_asin_title_o07_s00?ie=UTF8&psc=1 Fits where the center stand mounts and raises the bike nicely. Then a 4x4 of appropriate length under the engine should balance the front end up, or a bottle jack can work instead of the 4x4.
If you already have the centerstand then have someone push down on the rear of the bike to raise the front tire off the ground and prop the 4x4 or bottle jack under the engine.
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3 year old bike from that probablly gets washed regularly from a factory famously allergic to grease, I'd say the steering head bearings probablly have a notch in them. With the front wheel off the ground the bars should smoothly move from one side to the other no "clicks" or tight spots especailly on dead centre (normally where the appear).
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As a matter of interest, what size wheel is on the V7lll, 17" or 18"?
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The handlebars should not flop freely to either side, either.
I had a bike that did it after the first front tire change. I was told it was loose bearings. Silly me, I said it had to be the new tire and I did the on centerstand check of the head bearings. All checked ok...then I snugged the bearings. Problem solved.
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It seems to me that slightly over-tightening the head bearings works because it adds some friction to the steering. Wouldn't installing a steering damper be a better way to solve the wobble problem?
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It will only mask the real problem if at all.
EDIT:that is if you are referring to a hydraulic type or the friction type between the frame and forks.
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It will only mask the real problem if at all.
Or make it worse.
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3-year-old bike from that probably gets washed regularly from a factory famously allergic to grease...
Anni has never had a bath because she never gets dirty beyond a bit of bug here and there. Our Lady of the Garage is willing to sit still for a polish but is quite aquaphobic, which is fitting for a desert deity. :bow:
As a matter of interest, what size wheel is on the V7lll, 17" or 18"?
18" front
17" rear
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Before you begin tearing into the bike, consider it could simply be the tire itself. I have experienced that on a tire that was no where close to worn out. Perhaps not first on the list when you consider cost, but if the steering head bearings are not loose, this may be your next consideration.
John Henry
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Thanks for all your suggestions! :bow:
If after removing the top-case the problem persists, I will check the spokes (watched https://www.youtube.com/watch?v=9eOKzknv-TE ) and bearings (watched https://www.youtube.com/watch?v=zQJhcfdsWTk among others). Additionally, I've always checked tires cold. I also find running the front pressure a few pounds lower negatively impacts my ability to steer. They only have about 1600 easy miles on them so, in theory, they should be excellent condition.
Any ideas on how to lift the front end safely without a lift, jack or center stand? :gotpics:
Call Fay and ask if Richard can check them for you. He also wouldn't mind tutoring you. He's retired. :thumb: :grin:
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Call Fay and ask if Richard can check them for you. He also wouldn't mind tutoring you. He's retired. :thumb: :grin:
I may do just that if it becomes a problem. Of course, only after the world returns to semi-normal. :azn:
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Quote from: Zoom Zoom on Today at 12:50:15 PM (https://wildguzzi.com/forum/index.php?topic=105268.msg1669217#msg1669217)Before you begin tearing into the bike, consider it could simply be the tire itself. I have experienced that on a tire that was no where close to worn out. Perhaps not first on the list when you consider cost, but if the steering head bearings are not loose, this may be your next consideration.
John Henry
One problem...something caused the tire to wear like that. When the new tire wears the problem will get worse.
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Anni has never had a bath because she never gets dirty beyond a bit of bug here and there. Our Lady of the Garage is willing to sit still for a polish but is quite aquaphobic, which is fitting for a desert deity. :bow:
18" front
17" rear
The Breva has a 17" front, marvelous in the tight twisties and although stable in a straight line it can feel a bit "uncertain' in sweepers above 85mph if there are any irregularities. I can take my hands off the bars and it feels fine.
Having said that, my bike was one where Luigi lost his grease pail, and I did put some grease in the steering head bearings and tightened the head. This did make quite a difference.