Bad Vibrations

[magoo]

Help please !

I have an 08 Breva 1200 and I've had a major vibration problem with the Brembo front brakes for a while now. I get major vibrations when braking in the last few metres before a stop and on low speed steep downhill hairpins. It's definitely not warped or glazed discs, there is absolutely no pulsing at the lever. It's at its worst on bumpy downhill roads but I can induce it almost anywhere.

I've had the front brake pads changed (for new Kevlar based pads) and that fixed the problem for a month or so but it came back. The bike only has 13000 km on it and the suspension and steering head bearings are in perfect condition.

It feels like the pads are biting and releasing at a very high frequency. I had an Alfa Romeo many years ago with a severe vibe under braking that was fixed by having a copper 'paste' applied to the back of the pads. Anyone know if this might apply to bike disc pads ?

I love my Breva but I'm at my wit's end how to fix this issue, it was so severe on a ride last week that I almost felt the need on a steep local road to bail out. Local bike and brake shops don't know what to do and no-one I've spoken to has ever heard of an issue like this.

I'm looking forward to any and all replies on this.

Thanks

[john zibell]

I've had the front brake pads changed (for new Kevlar based pads) and that fixed the problem for a month or so but it came back. The bike only has 13000 km on it and the suspension and steering head bearings are in perfect condition.

Magoo,

Based on what you say about the replacement pads, it points me to the pad/rotor area. Are the rotor buttons moving freely? If not do some hard braking stops. That may free them up. Also you stated no warping since no pulse, but you may be getting pad deposits on the rotor, as you said, new pads got rid of it. Try cleaning the rotors with a Scotchbrite pad and see what happens. I've used coatings on the backs of pads to eliminate noise, but not vibration. For a bike I found just a little paint on the pad, then let the paint stick the pad to the piston seems to work for noise, but I don't know about vibration.

[ghezzi]

It's definitely not warped or glazed discs, there is absolutely no pulsing at the lever."

May I ask, Have you actually spun your wheel and measured run out with a dial indicator guage?

Because you also said;

I get major vibrations when braking in the last few metres before a stop and on low speed steep downhill hairpins.

In my experience, these are the classic symptoms of warped discs, my car currently suffers this dilemma. I am not experiencing pulsing at the pedal but some times there is a slight movement in the steering wheel. What I mainly feel in the final few meters of retardation is a slight jerkiness as the rate of retardation alters cyclicly.

My Bellagio has a bent R/H disc (measured) from previous owners slow speed fall, again the symptoms are as you stated, with no pulsing at the lever. I only have 2 spot (sliding) calipers.

ANYBODY GOT A SPARE 320mm BREMBO, black centre old pattern?

Could it possibly be, that as you have 4 spot calipers with horizontally oppossed pistons, that a warped disc could be pushing one pair of pistons out and the displaced fluid is just moving to the other side of the caliper and pushing the other 2 pistons in? This could cause the vibration you feel.

[ghezzi]

Addition: I had the discs on my last Ducati replaced under warranty, as have many people. Why is this happening?
Sports bike manufacturers are constantly demanding their parts suppliers create lighter, smaller, stronger, better, faster components. Ducati = sports bikes = largest Brembo client, which means Moto Guzzi as a small player just uses what is available = economy of scale. Thinner discs = lighter but also = shorter service life before the minimum thickness is reached. We should be grateful Guzzi's don't use bits from Harley Davidson suppliers (= heavier).

Many people who have suffered warped or worn out OEM discs have upgraded to aftermarket wave or petal discs. Close inspection reveals some of these discs are actually 2-3mm thicker, why? Could it be to resist warping.

I ponder their marketing strategy = style, supposedly run cooler, better water/dust/gas dissapation, longer service life etc but there is never a mention of them being lighter in weight.

If you definately need the performance advantage then Carbon Fibre wheels and Ceramic Matrix Composite discs are a must but for the average Guzzi rider, discs a few hundred grams heavier might be a good thing.

I have contemplated aftermarket discs for my Bellagio, a pair can be had for similar money to one Brembo.
I prefer the Retro look to something more modern and all blinged up but hey, I gotta stop somewhere!

[gsf12man]

I had a similar problem on my '06 Breva 1100, bought used. The front-brake lever pulsed very badly, especially at lower speeds, feeling like a badly warped rotor. Someone, somewhere on a Guzzi forum, posted that he'd cured his brakes' pulsing problem by using the brakes hard (which, so the idea went, would clean off deposits). I'd credit him but I don't remember where I saw it.

So, I braked as hard as practical and safe every time I used the brakes. The pulsing went down by 80% fairly quickly, and is now completely gone after a few thousand more miles. Re-reading John Zibell's comments, perhaps I was freeing up the buttons rather than cleaning the rotor, but anyway it worked.

This surely wouldn't be a cure for every brake rotor, but it worked on mine.

Tom

edit: I now see that my problem wasn't that similar but I'll leave the post up in case it is useful to someone.

[magoo]

Problem solved. Turns out it wasn't glazed discs but glazed pads. I had a new front tyre fitted yesterday and I asked the installer to pull the pads and check. He said they were badly glazed and after roughing them up problem has completely disappeared. I tried real hard to get it to vibrate and it's just plain perfect Brembo action.

Funny thing is that the first set of pads didn't look or feel at all shiny and the first tech thought that they looked pretty good but the second set of pads did cure the problem for a short while.

A couple of friends in the know reckon that since I've had two sets of pads glaze after quite low kilometres that I must be braking too gently and not properly heating the discs. What say you all ?

Either way I'm happy that the fix was so simple.

Cheers,

[Guy R]

Hey Glenn, Glad that you got your brakes sorted. I'm surprised though! Being as your favorite haunt is the Goat track and Mystery Rd I thought that you would be hard on brakes Cheers Guy

[magoo]

G'day Guy. Yes I am hard on the brakes up in the hills I suppose. Saw you arriving at Canungra on Sunday just as I was leaving.

Have you noticed that there have been a few more Bellas around lately ? Went to the NYE rally at Maidenwell and saw TWO in one day, they must be breeding

Cheers

[Daley]

Hi
I have also this problem that vibration noise from my bike is very high. Although i bring this to mechanic but no result. I can't understand what's problem. please give me some suggestion.

[sign216]

Hi
I have also this problem that vibration noise from my bike is very high. Although i bring this to mechanic but no result. I can't understand what's problem. please give me some suggestion.

Daley, what model, year, miles? How long have you had the vibrations?

How bad? Bad like an old British single or paint-shaker Harley? Or bad by modern standards?