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2018 Vespa GTS 300 ABS- Bianco
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Yesterday I nearly crashed as my Vespa went close to out of control!
I changed out old OE tires for new Michelin Power Pure-120/70 front, 140/70 rear. My balancer won't handle a Vespa wheel so I installed Dynabeads in the tires. I've used them on last 4 sets of MC tires with great results.
PSI set at glovebox numbers, 26 & 29 and empty SH39 top case on the back and took an 8 mile test ride last weekend. Very smooth but had acquired a new low speed (mostly deceleration) wobble from ~ 30-34 mph but not enough to be worth a post here.
Yesterday I rode to medical appointments 1.5 hours away, 130 mile RT.
I was cautious the first 40k (tires not scrubbed off either) or so as a twisty road and early a.m. traffic but rural and basically a quiet, uneventful ride.
The last 20k is I-64 interstate and riding on smooth concrete through a long sweeping curve (I-64 west combines with I-75 south) I leaned left into the curve at 60-65 mph and nearly lost control! The scooter violently began to wobble, barely was I able to stay on pavement and dumped off speed as I used all the roadway to get off on the shoulder. I looked down at tires and seemed OK. I had no one behind me, thankfully, and then tried riding very slowly on the band of speed dents in the shoulder to see how tires reacted and all seemed OK. I rode the shoulder a short ways, down a short ramp and turned into the city where I went immediately to an air pump. I got off, checked air pressure and was up a couple PSI as you'd expect from fast riding/warm tires on the I road. I could place my bare hand on each tire. The top case was empty except when parked. I weigh 215#'s.
Nothing seemed wrong and I carefully rode around town to one errand and two doc visits. The ride home I gradually brought straightline speed up to 60-65 mph on I road then stayed around 50 on twisty 2 lane closer to home. I avoided leaning into a curve, riding sort of like a new rider, stiff & upright. Only in the one small town did I experience the low speed wobble and no sense of an issue now or then. The tires remain ok psi today. I checked for head stem looseness just now and seems normal to me, smooth swivel but laterally tight too. My top case was empty when this happened. When I rode with my wife on the back with old tires and a milk case full of groceries with or w/o her back there I never had any sort of wobble.
Now I've lost confidence in this scooter for safe riding. Yes, I've worn out reading Vespa wobble threads and web comments. I've read MC wobble, loss of control experiences too. I do have hvy bar end weights on order and a front rack coming.
This was NOT! just a troublesome wobble---> it was nearly a killer wobble! I am convinced that a heavier bar weight will not prevent the wobble I experienced! Perhaps smoother but no way could that one thing affect so profoundly. My milkcrate loaded certainly weighs as much as the new Shad SH39 top case and my wife weighs 140#.
Went form a smooth scoot with a wornout to a new set of Michelins and a near crash.
For now I've lost all confidence in this scooter.
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@dooglas avatar
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As you may be aware, a sidecar dramatically increases the potential for wobble on a GTS. The first time I experienced that stronger wobble, I tried all the usual stuff with rebalancing wheels/tires, changing tire pressure, adding heavier bar end weights, etc. The sidecar manufacturer suggested I increase the tightness of the steering bearing set. I did that and it made a substantial difference. (in fairness, most riders solve the sidecar wobble with a hydraulic damper, which is a solution used on some heavier motorcycles without sidecars as well).

My current GTS has the ESS front suspension. I am unable to produce even a minor wobble by any of the means my previous GTS would wobble. (I have never attached a sidecar to my current GTS, so I've no idea how it would deal with that more difficult test)
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I am a life long rider. I'm trying to be information helpful here but at the same time seeking a solution to a problem I didn't have until changing a couple of things. My scoot was smooth as glass until I changed these 3 items: tires, beads and top case. My milkcase weighs as much as a top case and certainly more when loaded. That leads me to tires & balance. Having had beads on 4 sets of MC tires I see no reason for now to look that direction?
I can afford to change out tires but these are typically considered a good choice tire. It's interesting that changing from a wornout rear and old front I ended up worse off. Comments are consistent but also varied on this whole wobble thing!
I am a retired pro wrencher and my feel from looking at my front stem this a.m. is it's OK and not the problem. There's zero "shake", i.e. lateral movement there or up/down looseness. Wheel bearings are smooth and tight.
On upping the psi I've read comments here from old threads suggesting as much as a 25% increase-I will not go that high on a PTW tire.
Never tried a sidecar, not my thing. I like these Vespas but somethings got to change on mine!
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I would try changing the tires first. Power Pures are excellent tires -- I have them on my Zuma and they perform wonderfully -- but maybe they're not right for the particular combination of your scooter, you, and the way you ride. Glad you weren't hurt!
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I find myself wondering if the Dynabeads got clumped up somehow.
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Madison Sully wrote:
I find myself wondering if the Dynabeads got clumped up somehow.
This^^^

Did you have a tire sealant added?
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Also check the tread direction on the tires. One or both could have been installed incorrectly. Happened to me on my MC once and the bike rode okay until, but got a bit wild leaning into turns.
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UTC quote
I have quite a bit of experience with "death wobble" on lifted Jeeps. It was usually caused by incorrect toe-in, but there always had to be an avenue for the tires to start wobbling (something loose) before the wobble would get out of control. Also an aftermarket steering stabilizer was very effective at reducing high speed wobbles. With only one tire on the front there's not much in the way of wheel alignment, but tighteneing the steering column bearing, as mentioned above, defintely sounds like something I would start with.
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I understand kantuckid's concern about trying various adjustments or changes, and then trying to produce a death defying tank slapper. I'd start with the clue that he experienced the more usually 30-35 mph wobble on deceleration, and see if I could make that go away with various mods.

I have used Power Pures as well as City Grips with no problems. I have heard of others having a new tire that is seriously out of balance or out of round. I presume that could happen with a Power Pure as well as with any other tire. I am also somewhat suspicious of a possible issue with the Dynabeads. One thing to try (short of new tires) is to actually balance the present tires and wheels. If one requires quite a bit of weight, that would raise a particular doubt.
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Tire direction-I'm the one who mounted these on the rim and the scooter-the direction is correct! Any comments I make are about my work on the scooter, not someone else.

Sealant- nope, none in there. Also- I am a life long woodworker and tires had these sitting in my shop so I blew them out then used the rubber cleaner used for patching tubes & tires. it's not sticky either. The tire mounting fluid I've been using last few years is Formula 1.7 and ones of it's characteristics is it leaves no residue, thus I doubt clumping inside.

Stem bearings- I moved the scooter to my workshop today and blocked the front up off floor and wiggled the front. No lateral movement, just a smooth swivel action. Not to say it couldn't be tighter but with only 3,800 miles on the scooter and a drastic wobble not there before seems unlikely to me?
Jeeps I know lots about the green ones. I sadly lost a CO from the M151 jeeps rollover crap before they began specialized training on them. I drove a Jeep J 10 pickup to work for several years- that would make anyone hate jeeps? HA!
Would I trade my life for the cost of a set of tires? Of course not!
But not what I'll consider doing for now as I look at other more variable answers. I really doubt the tires themself are at fault as a stand alone factor. If one or very few psi is whats between life & death I'll not ride at all? as it does change constantly. I can watch it change on my Ford Pick ups TPMS system as they heat up down the road or even more heat on rears when towing. On MC's in the past I typically went up a couple of pounds.
In full view of my comments, I remain open minded to solving this problem.
All this talk about a top case causing this wobble, I understand were it heavily loaded but not for an empty case? So many other weight factors present or possible I just don't buy in.
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I do know that with passenger tires they get tested more than say farm or truck tires, at least when I worked an a Goodyear tire plant. Every passenger tire went through a balance machine to qualify (or not) for becoming an OE tire. Each was also run through a force variation machine under inflation to catch interior defects in the carcass. They were also human eye inspected pre and post curing for defects before these other checks. I cannot imagine that a PTW tire isn't checked as much or more than a car tire. Any article I've read about MC tires has taught me nothing beyond my direct experience of working on the machines that make tires, seeing the whole process day after day and far too general overall.
A tire like a scoot tire has to be nigh on perfect to work OK.
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I've ridden one GTV with a 140 rear and I did notice that the wobble was much more noticeable than one with stock tires. That was only one example, though, and it had a decent amount of miles on it.

Did you mow through any potholes recently? One of the ladies in the scooter group had a real bad wobble arise and they ended up replacing the entire fork. Just fork bearings didn't help - they went back and replaced the whole thing.

Also someone came to me with a GTS with the new fork design and a horrible wobble. The Vespa shop had to replace that one too - apparently he strapped it down too tight and bent the fork. You couldn't tell just by looking at it.
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UTC quote
No potholes but I did hit the edge of one of those heavy steel plates in the city yesterday that was sitting kind of up a bit and got the low speed wobble thing only briefly.
To see an example video clip one was just posted in my cross thread on wobble in ADV/ Battle Scooters-
it's called a "tank slapper" not a wobble, and shows a pair of MC's in a drag race where one goes wild like my Vespa did.
Ceramic beads do pickup some of the soapstone slurry that's used to coat the innerlining of tires so they won't stick to the bladder that inflates them against the tire curing mold halves while under heat and pressure. they end up slightly larger and black over a tires sets life. I know as I've recovered them for reuse-that is if they didn't "escape". Laughing emoticon Never have I had them clump. They just happily roll around far as I can tell.
⚠️ Last edited by Kantuckid on UTC; edited 1 time
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UTC quote
I have been noticing the wobble lately when decelerating from 35-20mph and there has been no changes made at all. Tires, bar end weights all remain the same. Im guessing as someone has suggested I may have hit one of many freaking pot holes or concrete dropped on the streets of NYC and it must have bent the fork slightly. Will search to see if replacing fork can be done by one with guidance or is it better for the Dealership to do it.
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UTC quote
A big wobble can change your entire attitude about scooting.

I have been using Power Pure tires in the 120 front, 140 rear as you are using with no real problems. They are the only tires I buy.

But my GT with the top case does wobble more than the other two (one now).

It has heavier bar ends but still wobbles significantly at speeds between 25 and 50ish. When I remove my left hand to take photos, it can go into a big wobble. So less photos when using that one or, in the least, I hold on very tight with my right hand. But it never wobbles with two hands on the bars.

I remember that Motovista once told me that he had a bad wobble on his heavily modified GT. He ended up changing out the steering column, I know, a big change, but he said it worked for him. He thought the old one had gotten bent somehow.

I have never had a wobble though going your speeds while turning. That is a new one on me.

My easy suggestion is to up the tire pressures. I run 30/30.

Bill
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Seems an easy enough try to get rid of the Dynabeads and have the wheels balanced. I was never a fan of Dynabeads.
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Taking a real flier here. You mentioned the scooter with the top case wobbled but not with the milk crate full of groceries.

So, thinking out side the box here, or the top case as the "case" may be, the milk crate had different airflow characteristics because it was square with an open frame partially randomly blocked from airflow by the groceries. Plus it had some weight because it was full. The top case has a smooth exterior surface with a different airflow pattern than the crate and it was empty. A pound or two difference in tire pressure or a tweak on the stem nut can often improve or worsen the handling characteristics.

I have often felt that the caster on the Vespa front wheels was responsible for some wobble issues. Adding weight to the top case or even changing shock settings can have an effect on caster,via a slight attitude change.

It is a matter of trial and error. Whether wobble can be eliminated altogether is unknown. That being said, if just changing tires is the solution, then that is the way to go.
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Kantuckid wrote:
Tire direction-I'm the one who mounted these on the rim and the scooter-the direction is correct! Any comments I make are about my work on the scooter, not someone else.

Sealant- nope, none in there. Also- I am a life long woodworker and tires had these sitting in my shop so I blew them out then used the rubber cleaner used for patching tubes & tires. it's not sticky either. The tire mounting fluid I've been using last few years is Formula 1.7 and ones of it's characteristics is it leaves no residue, thus I doubt clumping inside.

Stem bearings- I moved the scooter to my workshop today and blocked the front up off floor and wiggled the front. No lateral movement, just a smooth swivel action. Not to say it couldn't be tighter but with only 3,800 miles on the scooter and a drastic wobble not there before seems unlikely to me?
Jeeps I know lots about the green ones. I sadly lost a CO from the M151 jeeps rollover crap before they began specialized training on them. I drove a Jeep J 10 pickup to work for several years- that would make anyone hate jeeps? HA!
Would I trade my life for the cost of a set of tires? Of course not!
But not what I'll consider doing for now as I look at other more variable answers. I really doubt the tires themself are at fault as a stand alone factor. If one or very few psi is whats between life & death I'll not ride at all? as it does change constantly. I can watch it change on my Ford Pick ups TPMS system as they heat up down the road or even more heat on rears when towing. On MC's in the past I typically went up a couple of pounds.
In full view of my comments, I remain open minded to solving this problem.
All this talk about a top case causing this wobble, I understand were it heavily loaded but not for an empty case? So many other weight factors present or possible I just don't buy in.
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Kantuckid wrote:
... seeking a solution to a problem I didn't have until changing a couple of things. My scoot was smooth as glass until I changed these 3 items: tires, beads and top case...
Lots of suggestions for a fix here. I'm of the "make a small change and test the results" mindset. Maybe start with the easiest, cheapest and least time consuming: adjust tire pressure. Go for a ride and see what happens. If the wobble persists, put back the milk crate. Test ride. Remove DynaBeads. Test ride. Etc.

FWIW, I've had the wobble at high and low speeds on 3 different GTSs but only when riding one-handed. Never did pinpoint the cause.
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UTC quote
Re: Seriously Bad! Wobble Event!!!
Kantuckid wrote:
Yesterday I nearly crashed as my Vespa went close to out of control!
I changed out old OE tires for new Michelin Power Pure-120/70 front, 140/70 rear. My balancer won't handle a Vespa wheel so I installed Dynabeads in the tires. I've used them on last 4 sets of MC tires with great results.
PSI set at glovebox numbers, 26 & 29 and empty SH39 top case on the back and took an 8 mile test ride last weekend. Very smooth but had acquired a new low speed (mostly deceleration) wobble from ~ 30-34 mph but not enough to be worth a post here.
Yesterday I rode to medical appointments 1.5 hours away, 130 mile RT.
I was cautious the first 40k (tires not scrubbed off either) or so as a twisty road and early a.m. traffic but rural and basically a quiet, uneventful ride.
The last 20k is I-64 interstate and riding on smooth concrete through a long sweeping curve (I-64 west combines with I-75 south) I leaned left into the curve at 60-65 mph and nearly lost control! The scooter violently began to wobble, barely was I able to stay on pavement and dumped off speed as I used all the roadway to get off on the shoulder. I looked down at tires and seemed OK. I had no one behind me, thankfully, and then tried riding very slowly on the band of speed dents in the shoulder to see how tires reacted and all seemed OK. I rode the shoulder a short ways, down a short ramp and turned into the city where I went immediately to an air pump. I got off, checked air pressure and was up a couple PSI as you'd expect from fast riding/warm tires on the I road. I could place my bare hand on each tire. The top case was empty except when parked. I weigh 215#'s.
Nothing seemed wrong and I carefully rode around town to one errand and two doc visits. The ride home I gradually brought straightline speed up to 60-65 mph on I road then stayed around 50 on twisty 2 lane closer to home. I avoided leaning into a curve, riding sort of like a new rider, stiff & upright. Only in the one small town did I experience the low speed wobble and no sense of an issue now or then. The tires remain ok psi today. I checked for head stem looseness just now and seems normal to me, smooth swivel but laterally tight too. My top case was empty when this happened. When I rode with my wife on the back with old tires and a milk case full of groceries with or w/o her back there I never had any sort of wobble.
Now I've lost confidence in this scooter for safe riding. Yes, I've worn out reading Vespa wobble threads and web comments. I've read MC wobble, loss of control experiences too. I do have hvy bar end weights on order and a front rack coming.
This was NOT! just a troublesome wobble---> it was nearly a killer wobble! I am convinced that a heavier bar weight will not prevent the wobble I experienced! Perhaps smoother but no way could that one thing affect so profoundly. My milkcrate loaded certainly weighs as much as the new Shad SH39 top case and my wife weighs 140#.
Went form a smooth scoot with a wornout to a new set of Michelins and a near crash.
For now I've lost all confidence in this scooter.
I believe that what you experienced is not the typical wobble but what is know as a "tank slapper." It happened to me once on a Harley Softail Classic at about 60 mph when I made a sudden steering input/braking maneuver to avoid a pothole. It's caused by a sudden force from either a rider or road surface input; basically a harmonic frequency thing tied to frame flex. This is a rare but unavoidable occurrence on some two-wheeled vehicles.

I wouldn't let it drive you to drink as there are better things out there to make us crazy!!!
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UTC quote
Another band-aid you can do is use all four bar end weights. You'll need to go find bolts long enough, though, or rethread some SAE bolts if you're handy.

I hated the jittery steering on my P200 at speed so I ran both a regular GTS weight AND a Kymco bar end weight on each side.

This worked so good that I did the same thing on my Buddy with 10'' wheels. The handlebar jitters of 10'' wheels spinning at 60+ mph really messes with my anxiety. Laughing emoticon Girlfriend said the Buddy felt like an entirely new bike.

EDIT: This reminds me that I need to order some more weights for my old Elite 250. It suffers a similar low speed wobble like the GTS, just not as often. Never at speed though, the leading link front suspension on the Elite 250's are solid as a rock going in a straight line.
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UTC quote
Vintage1 wrote:
Seems an easy enough try to get rid of the Dynabeads and have the wheels balanced. I was never a fan of Dynabeads.
I have been liking them but removed them today. Pulled the wheel assy and they are gone. One thing removed from consideration. FWIW, they don't clump but static does make them cling to nearly everything. When you place them in through the valve stem it requires constant tapping or a vibration or takes a long time. Given my rim and tire were pristine clean inside I eventually got them all out. 8/15 I'll figure out why the bead rim has a very slow leak? I can borrow some sealer in my nearby tire shop but they can't balance this wheel.
I'll use lead weight not double bar ends. The Piaggio heavy black ends I have coming take a 60mm screw.
I din't post the 'tank slapper" link here but an ADV member posted it on Battle Scooters over there. It shows exactly what happened to me which at least seemed to take longer as I traveled further than the drag racer MC in the link video.
Change yer scootin perspective real fast! I spent lots of time in helos so adrenalin is not new to me but this was one of those hard to forget dealies!
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UTC quote
You posted FIVE times with just this quote and no extra content. Not for the first time.

Faulty thumb on phone?
cballweg wrote:
Kantuckid wrote:
Tire direction-I'm the one who mounted these on the rim and the scooter-the direction is correct! Any comments I make are about my work on the scooter, not someone else.

Sealant- nope, none in there. Also- I am a life long woodworker and tires had these sitting in my shop so I blew them out then used the rubber cleaner used for patching tubes & tires. it's not sticky either. The tire mounting fluid I've been using last few years is Formula 1.7 and ones of it's characteristics is it leaves no residue, thus I doubt clumping inside.

Stem bearings- I moved the scooter to my workshop today and blocked the front up off floor and wiggled the front. No lateral movement, just a smooth swivel action. Not to say it couldn't be tighter but with only 3,800 miles on the scooter and a drastic wobble not there before seems unlikely to me?
Jeeps I know lots about the green ones. I sadly lost a CO from the M151 jeeps rollover crap before they began specialized training on them. I drove a Jeep J 10 pickup to work for several years- that would make anyone hate jeeps? HA!
Would I trade my life for the cost of a set of tires? Of course not!
But not what I'll consider doing for now as I look at other more variable answers. I really doubt the tires themself are at fault as a stand alone factor. If one or very few psi is whats between life & death I'll not ride at all? as it does change constantly. I can watch it change on my Ford Pick ups TPMS system as they heat up down the road or even more heat on rears when towing. On MC's in the past I typically went up a couple of pounds.
In full view of my comments, I remain open minded to solving this problem.
All this talk about a top case causing this wobble, I understand were it heavily loaded but not for an empty case? So many other weight factors present or possible I just don't buy in.
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Glad to hear you were able to ride it out.

I researched the GTS wobble topic heavily before seeking out one of the last new 17s with ESS front suspension. I recall reading that Power Pures on a GTS have a tendency to follow the grooves in pavement. Switching to Michelin Citys helped tame the problem. Unfortunately I can't remember where I read this. I brought the subject up while on the phone with ScooterWest this afternoon. They confirmed that this is a known issue with Power Pures in some situations. Balancing beads may have exacerbated the this.

Regarding bar end weights, think of the fork and handle bar assembly as a resonant system, kind of like a tuning fork. The fork is essentially a long pipe with an offset bend then the load from the suspension perpendicular to that bend. In my mind's eye I can see that thing wiggling all over the place in the right conditions, not just fore and aft, particularly side to side. Adding weight to the end of the bars or moving the existing weights further out with bar end mirrors between the weights and the bars lowers the Q of the system.
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Wpw man, that sounds terrifying!
WLeuthold wrote:
My easy suggestion is to up the tire pressures. I run 30/30.
Bill
I know it's probably not the answer you want, but this does make a huge difference for me. If I run sticker pressure on my tires (29/26) I get wobble all over the place. I go about 30/30 like Bill does, just found that is what works for me - no wobble with both hands on the bars, even in high speed curves (60 mph) though like him, if I take one hand off it will get dicey after a couple seconds.

Good luck man, I hope you get this sorted. Did removing the beads do the trick?
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get a marc parents balance tool and properly balance your wheels. remove the balance beads first of course. while you have the rims off check the bearings for excessive play.

What brand and style of tire were the old worn out ones?
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This event as described, and a front flat, are about the only things I truly fear about PTW riding.
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Jet Peddler wrote:
This event as described, and a front flat, are about the only things I truly fear about PTW riding.
Don't leave out that 103 yr old who can't see past the windshield of his 1975 Chevrolet wagon who makes a left turn right in front of you. Happened to me but I luckily was only doing 30 at the time and avoided contact.
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Vintage1 wrote:
Jet Peddler wrote:
This event as described, and a front flat, are about the only things I truly fear about PTW riding.
Don't leave out that 103 yr old who can't see past the windshield of his 1975 Chevrolet wagon who makes a left turn right in front of you. Happened to me but I luckily was only doing 30 at the time and avoided contact.
Or the texting teen.
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Maybe I should have said "fear most."
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Try setting the rear shock differently, try one way then the other.
OP
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old as dirt wrote:
get a marc parents balance tool and properly balance your wheels. remove the balance beads first of course. while you have the rims off check the bearings for excessive play.

What brand and style of tire were the old worn out ones?
Pirelli 23 & 24
I have a HF balancer which has two cones, one that fits the hubcap side, the other doesn't fit the backside. Just got back from the shop trial & errored 3/4" sockets until one was close, wrapped in masking tape and pulled it up tight with other cone and spins OK. I currently have 15 grams one side 14 grams the other which is nearly identical to the OE weights. I do wish I'd check/balanced the wheel as then I could spin the tire on the rim for exact balance. I know about wheel balance, I'm the retired auto mechanic guy... Vespa's I'm learning and not always the way I'd like-given my riding event Monday!
I watched a scooterwest video of a stem bearing install this a.m. and have decided against messing with mine for now. Given I had no wobble prior to tire change, I'll play with tires first. I've tried to find play in stem and there just isn't any there so it stays as is for now. Tightening the bearings over spec would just be a wrong minded masking of whats the actual cause for my wobble.
Changes were: tires, top case-empty one and balance beads.
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zigzagguzzi wrote:
Try setting the rear shock differently, try one way then the other.
My rears have been set at heaviest load since I bought it at 1,000k and rides like a dream when not trying dumping me. Laughing emoticon
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It sounds like a tank slapper rather than a wobble. It's usually caused by an under damped front end going into an oscillation and is made worse having less weight over the front wheel. The heavier bar weights should stop it. I'd guess the milk crate on the back is catching the wind and lightening the front wheel. Fighting the oscillation tends to make it worse. It's best to just let off the throttle gradually and move your body forwards. In the old days they used to fit steering dampers to the front forks of motorbikes to stop them doing this. I guess they just design them better these days.
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Two words:

Vortex shedding.

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robinm wrote:
It sounds like a tank slapper rather than a wobble. It's usually caused by an under damped front end going into an oscillation and is made worse having less weight over the front wheel. The heavier bar weights should stop it. I'd guess the milk crate on the back is catching the wind and lightening the front wheel. Fighting the oscillation tends to make it worse. It's best to just let off the throttle gradually and move your body forwards. In the old days they used to fit steering dampers to the front forks of motorbikes to stop them doing this. I guess they just design them better these days.
First off the scoot had an empty SHAD SH39 on the back when this happened.
2nd-I called it wobble cause that's what term comes into MV most often. You'll notice their is a reference I've made to a tank slapper video posted on my cross thread, same subject, on ADV in Battles Scootersby BMWBud. It will come up on google. Yes, it was a tank slapper.

Yes, I got it shut down and fighting was out of the question. It was all about holding on, reducing speed and remaining upright and on the roadway. I did look for a soft landing but thankfully didn't use the grassy area nearby outside the curve.
Given my short arms there's not much moving further forward gonna happen as I'm already there.
Not at all easy situation and I feel very lucky! to be talking about solutions.

FWIW, I was sort of "there" in the old days as I started riding in 1963 at age 20.
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Madison Sully wrote:
Two words:

Vortex shedding.

I buy that! Must have a physics guy named Madison Sully on hand?

Google this: "vortex shedding with motorcycles" and read the first item that comes up. It is an engineers treatment of this exact subject.
In my case the wind/yaw angle factor probably came from the speed generated wind while leaning into a curve (the angle) at fairly high speed as natural wind was negligible. This paper on vortex shearing is of particular interest as it discusses the windshield, top case and other aspects of my scooters or motorcycles as factors and all part of my scene.
I'm needing some stick on weights to finish my front wheel assembly and can buy them Friday in a town.
I'm also going to remove the beads in the rear wheel thus one more factor of change is gone, no matter that they've worked well for me in the past.
Changing tires at home-
I'll throw out this helpful hint if your working on PTW tires in a home shop.
They can be very stiff as you may know. I am a serious woodworker and have lots of clamps on hand. The type that comes in handy for these tires is the one handed squeeze clamp. I have several brands but it matters that you buy/use the heavy duty version as the light ones are crappo for wood or tires, whatever. 300# force is what to look for. Irwin are VG as are Wolfman, Jorgenson, DeWalt and Bessey, I own all of these in various sizes and use the 6" version for tires but longer will work just sticks out near your eyes. Avoid cheap off brands like the plague! They back off and can ruin a project. You do of course need rim protectors and the motion pros are better than others-blue ones! There are several tires irons out there for PTW's. I wish I had the Motion-Pro type that one bar inserts into the slot in the other bar as they break beads more easily. Also own some good bead lube as there are better types than simple soapy water-the Formula 1.7 I use is magic stuff.
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UTC quote
Kantuckid wrote:
First off ...
Perhaps I read your original post wrong. I thought you stated you fitted a top box on your Vespa but didn't install the recommended heavier bar end weights. I thought you then implied you fitted the front tyre yourself but didn't balance the tyre and instead used beads. Then it seemed like you were complaining about the resulting "wobble" that nearly killed you and how you can't trust your scooter. Obviously I missed something.
⚠️ Last edited by robinm on UTC; edited 1 time
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UTC quote
Kantuckid wrote:
Madison Sully wrote:
Two words:

Vortex shedding.

I buy that! Must have a physics guy named Madison Sully on hand?
Clown emoticon Eyelashes emoticon Scooter emoticon
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UTC quote
Kantuckid wrote:
old as dirt wrote:
get a marc parents balance tool and properly balance your wheels. remove the balance beads first of course. while you have the rims off check the bearings for excessive play.

What brand and style of tire were the old worn out ones?
Pirelli 23 & 24
I have a HF balancer which has two cones, one that fits the hubcap side, the other doesn't fit the backside. Just got back from the shop trial & errored 3/4" sockets until one was close, wrapped in masking tape and pulled it up tight with other cone and spins OK. I currently have 15 grams one side 14 grams the other which is nearly identical to the OE weights. I do wish I'd check/balanced the wheel as then I could spin the tire on the rim for exact balance. I know about wheel balance, I'm the retired auto mechanic guy... Vespa's I'm learning and not always the way I'd like-given my riding event Monday!
I watched a scooterwest video of a stem bearing install this a.m. and have decided against messing with mine for now. Given I had no wobble prior to tire change, I'll play with tires first. I've tried to find play in stem and there just isn't any there so it stays as is for now. Tightening the bearings over spec would just be a wrong minded masking of whats the actual cause for my wobble.
Changes were: tires, top case-empty one and balance beads.
your confusing the crap out of me, first you said you balanced with dyna beads , now you said you balanced with 15 and 14 grams.

Start from scratch, get a marc parnes balance tool so you can properly support both sides of the rim correctly. remove the weights and dyna beads. Best way to remove dyna beads is to break the bead and dump them out. make sure you get them ALL out as they will mess with static balancing. Reseat the tire. and static balance. you only need the weights on the off side of the rim away from the nice pretty outside.
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