Tank slappin’ California

[HarveyMushman]

I have a ‘07 California Vintage with just over 60k miles. I bought it in February and only about 3k of the miles are mine. In my ownership it has always been unstable when anything more than the easiest of cornering loads are applied. By unstable I mean it quickly gets into a tank slapping behavior if I persist with the cornering load. I’ve put up with it until now, but yesterday it scared me at higher speed.

What might cause this behavior? The rear shocks appear to be original. I already have a pair of Ikons on order with MG Cycle, hopefully will receive them soon. The rear tire is a BT46 bias ply, while front is a ME880 radial. I think I’ve read about mixing tires like this, and how one shouldn’t do it, although when I bought the bike it had a radial on the rear and was unstable then too. I have a new BT46 I can install on the front. Apart from construction differences, the ME880 is a garbage tire, with little traction wet or dry. Maybe that could do it?

What else?

[guzzisteve]

Have you ever adjusted your steering head bearings or greased them? If not, now's the time.

[willowstreetguzziguy]

I had a 1975 BMW R90S that scared me many times because I could never get the steering bearings adjusted quite right. I was always taking the tank off, loosening the nut and adjusting them to try to get them to be right, but it never worked out. With over 40,000 miles on my 1200 sport, the steering is solid and I have never had to be adjusted once.

[moto]

Could be a combination of things, like those already suggested. Is your ME880 worn out? Radials have more sideways play than conventional tires and as a result that radial on the front may be amplifying any tendency to wobble.

I'd start by putting the Bridgestone on the front and checking and adjusting the steering head bearings while I had the wheel off.

[Moparnut72]

I don't know for sure but having a radial on the front and a bias ply on the rear is a no no. I don't remember reading this but I think so. Radial on the rear and bias on the front is ok, Guzzi does it on V7s and so does Triumph on their Bonnevilles at least from personal experience. But doing further research, I can't find anything saying don't do it the opposite way.
kk

[Vagrant]

Odds are the head bearings. I always put a grease zerk on the top and pump the whole head full. But just for grins, I'd get the tires in the air and spin them to see if there might be a broken belt in one of them.

[HarveyMushman]

Thanks, all. I have not inspected or adjusted the steering bearings so will do, and get the BT46 on there, hopefully this weekend.

I've owned and ridden lots of bikes in the last 20+ years but never had this problem. Looks like I'm going to learn something!

[Frenchfrog]

Do you have a decent steering damper on it ?

[HarveyMushman]

Do you have a decent steering damper on it ?

Define decent? It has the one that Guzzi supplied originally. I've tried adjusting it in and out, not sure I've noticed a difference.

[Antietam Classic Cycle]

The swingarm on a friend's '98 EV moved side-to-side about 4 mm until I adjusted the pivot pins. Worth checking yours.

[guzzisteve]

Define decent? It has the one that Guzzi supplied originally. I've tried adjusting it in and out, not sure I've noticed a difference.

If you disconnect one side then try sliding it you'll notice it does nothing.

[Frenchfrog]

Define decent? It has the one that Guzzi supplied originally. I've tried adjusting it in and out, not sure I've noticed a difference.

If it's this one which seems to be fitted to the Euro version of your bike it's shite;cheap shite.
https://www.officine08.it/p789_ammortizzatore-di-sterzo-classic-90mm.html
                                                        I'd get an adjustable hydraulic one .A few people on this side of the pond have experienced similar handling problems  and some think it's due to a combo of the luggage and screen.I couldn't say as i don't own a late model  but every bike I have owned has always had an adjustable and functioning damper fitted.

[nick949]

Fairing? If there is any inbalance in the way the wind hits the front, that will set it off.
Even mounting my phone on the bars when my Eldorado is naked is enough to give it a low speed shimmy (I don't go fast enough to get a tank slapper.  Also, where your body weight is situated can make a huge difference. Can you move your personal centre of gravity forwards an inch or two?

Nick

[lazlokovacs]

nearly one hundred thousand miles on cali vintages so I'll chime in.

they do weave at around 80mph, its at its worst with the stock screen on.

at any other speed they should be absolutely rock solid, especially in turns.

changing the windshield for a swanee/HandH fairing from Harpers eliminates the weave.

There were two types of steering damper fitted during the various model years, both are junk imo.

My bet is the steering bearings and tyre combo are exacerbating the existing weaving problem.

I'd check the steering bearings first then change thet tyre and ditch the windscreen as it does nothing much except look cool at the expense of horrendous helmet buffeting above 70mph and create the aforementioned weave.


Also - you can go a good few psi up from what the owners manual recommends. I used to do something like 32/42, can't quite remember, but I used mine for a lot of long distance high speed work.

 

[Tom]

Bump the air pressure up on the front tire.  I go 2 lbs.  less than max on the sidewalls.  Moto Guzzis are front heavy.  Your sidewalls are flexing too much.

[Turin]

What Tom said. My hot rod Cal III had a bad head shake at 80mph+. I removed the batwing fairing and it improved the, but the weave didn't go away. Putting 38psi in the front made her stable at high speeds.

[chuck peterson]

Frozen Shock mounts and maladjusted swingarm pins are showing up in my foggy brain from 2000 miles away …followed by front fork dampers and the steering bearings

Actual tank slapper? Going rapidly stop to stop on the fork while going at speed? Slamslamslamslam throwing your hands off? Things get broke afterwards?

My impression of steering dampers is they are designed to only work during tank slappers..but yours didn’t

[s1120]

Bet its the head bearings. When I got my 02 cali stone it shook bad on sweeping corners. When I went through the bike [less then 9k at the time[ I found the head bearing adjustment VARY loose!!  Once I adjusted those, it was perfect.

[HarveyMushman]

Thanks again, all. Once I get past turkey day I'll get started with the tire change, etc.

To elaborate a bit, the issue is present at all speeds, always in a corner with a bit of load on the tires. I turn in, bit of throttle, and the bike starts to wobble. I've never pushed it harder and have so far accommodated the problem by being less sporting in my cornering. It's hard though, because unlike my V7 III Milano, the CalVin actually has cornering clearance! Anyway, on Sunday I took an on-ramp at 60+ mph in 4th gear, mindful of the potential for wobble, and it very nearly developed into a full-on tank-slapper. I was able to ease up and let it settle down, but clearly I can't accommodate this any longer.

Re: the windscreen, I don't think it has any effect, not at the speeds I generally ride anyway (no interstates). I've ridden it with and without, and the cornering wobble is always there. Plus, the MRA Vario attachment I installed has largely cured the buffeting problems so I'd really prefer to keep the screen.

[guzzisteve]

While you have the front wheel off, drop front end, clean & grease head bearings. You wouldn't believe the difference even if you have to pay someone to do it.

I have seen new bikes & loose bearings. The old Service manuals used to have adjustment service at 25Kmi

[Shiny Hat]

It seems something is causing the front end to correct for a tracking issue. The more it tries to correct the more it will over correct to the point of you are no longer on the seat. I would look long and hard at the rear suspension. It’s fine going straight but a lateral load which is exacerbated by accelerating, shaft jacking, only adds to the front end trying to correct. Best of luck and hope it’s a simple solution. Great looking bike by the way. You can check out fortnine video on tank slappers, it might give you some ideas on where to look.

[kfz]

Is your front tyre too low pressure.  I often find owners running their bikes at the book pressures.   Tyres have moved on, you want them up around 38 psi .  Check the Metz website.

[geoff in almonte]

I had an 08 CalVin with the same issue - never did solve the problem.

But I agree that the steering head bearings should be serviced/adjusted.  If you are running Avon RoadRiders, deep six them.
A steering damper will only fix the symptoms, not the problem.
I had Matris cartridges and springs up front and IKON shocks in the rear.
If I hit a bump in a corner the bike would weave dangerously, not a tank slapper but severe enough to scare the s*it out of me.  If I hit two bumps the bike would literally jump into the oncoming lane!! 

The suspension shop that I was working with agreed with another poster here that the front suspension and rear suspension were not in sync.
They recommended a re&re on the head bearings, decent rubber, and removing the 50lbs of steel and fibreglass hanging out behind the rear axle.
Once you get the steering stabilized you can always re-install.

I gave up and sold the bike,

Good Luck!

G
 

[Frenchfrog]

If you look at any sports bike  you will see a steering damper that actually functions...not just there as bling.
So while one can say that they mask an issue one can also see they are necessary too or much more sophisticated and technically radical machines would not have them.
I agree with all of the suggestions from the other posters about tires, bearings ,setting up the suspension correctly and will add that others with the same machine seemed to have similar complaints.

[Huzo]

I’ll suggest the following…
As Frenchfrog points out, any high end sportsbike will have a steering damper and this is linked to stability.
The more stable anything is, the less tendancy it has to be amenable the changes of direction.
This is a big thing in aircraft.
But back to bikes. Your basic garden variety MV Agusta for instance, has a rather small amount of stability designed into it, not to say that it feels insecure…On the contrary, but the closer you are to neutrally stable, the easier it is to change direction.
This is what our budding Jack Millers want, here in Australia.
Now the Cali, which has the same handling qualities as the Exxon Valdeez, should have very little tendancy to try and swap ends all by itself, but once an upset occurs, there is a LOT of mass oscillating around the C of G and as the masses depart from the neutral point, the amplitude increases and it diverts into an unstable condition.
Or a crash…If you prefer the term.
The damper is just there to crush the tendancy of the oscillations to magnify.
The good suggestion is to not have extraneous masses too far away from the C of G. This increases the moment about which the force acts.
I don’t know if there’s “50 lb” hanging out behind the rear axle, but if it was on my bike it would be hanging on the shed wall.
So.
#1 New tyres
#2 Headstem bearings service/replace
#3 True and balance wheels
#4 Check/replace wheel bearings
#5 Service front forks/ replace oil.
#6 Ditch handlebar mounted “fairing” or barn door.

[Frenchfrog]

Nicely and concisely explained Huzo.

[moto]

Is your front tyre too low pressure.  I often find owners running their bikes at the book pressures.   Tyres have moved on, you want them up around 38 psi .  Check the Metz website.

Not so. The Metzeler website directly contradicts your claim. It says to use the owners manual's inflation settings:

Remember to check the inflation pressure of your tires weekly.
You will find the correct pressure in the operating manual of the motorcycle. Use Metzeler's information only as reference.

See https://www.metzeler.com/en-ww/tech-and-tips/pressure-safety-maintenance

[Moparnut72]

You never know what can cause an issue like this. My former '22 Triumph T120 developed a wobble this summer that it hadn't displayed before. I don't know if it was there all along or developed near the end of the 10,000 miles I put on it. I got it new, I traded it for my Mandello in October. I seemed to manifest itself when descending a somewhat steep grade. Probably needed steering stem attention. One of the reasons it is gone is that it shuddered on acceleration at lower rpm and was buzzy at higher revs. I got the usual answer at the dealer, "they all do that." Now that Guzzi has a model, Mandello, that fits my needs the Triumph is gone. Now if the dealer will get my damn side cases, I haven't ridden the bike near as much as I would like. Been a month and a half. If I knew then what I know now I wouldn't have let them order the cases. AF1 Racing has 3 sets in stock. I called Piaggio customer service, they haven't been much help either. Rant over.

[Tom]

Not so. The Metzeler website directly contradicts your claim. It says to use the owners manual's inflation settings:

See https://www.metzeler.com/en-ww/tech-and-tips/pressure-safety-maintenance

True.  It also states...."TYRE CONSTRUNCTION

Different constructions

We have three distinct construction types: bias (also called cross-ply) tyres (“-”), bias belted tyres (“B”), and radial tyres (“R”). The tyre’s ability to carry side and peripheral forces differs for each distinct construction type. Therefore, a combination of different construction types can influence the motorcycle’s performance. Only the tyre combinations listed in the motorcycle manufacturers fitment charts are allowed."

The point is moot when it comes to mixing of the types of tires bias ply & radial.

[LowRyter]

My EV will get unstable when I take my hands off the bars.  And gets very much so when I load the rear luggage rack.