Front brake vibration / tried everything

Saifmamoun · Mar 26, 2021

Hello

I know there are many posts about this problem.

My story started when i brought the bike Hyperstrada 2013 before few months ago.

I did a full check at the dealer and they changed the front disks due to vibration when braking.(front end).
And it was okay since then.

I installed brand new Pirelli tyres and after the installation the bike started to get front brakes vibration at high speed and a grap and go feeling when stopping at a traffic light to a full stop.

I went back to the dealer they balanced the front wheel and installed new bads and i still have the same vibration, the checked the steerer bearing and they are okay.

I check the floating bolts and they are very tight i cant move them by hand so i cleaned them and after cleaning i can only move them using screwdriver that fits inside, is this because the disks are still relatively new (one month old)??

Fluids are okay and no ABS warning light.

I left the front wheel and turn it by hand i noticed that the bads are holding the disks. sometimes it is hard to turn it and then is much easier.

Any advice.

gatdammit · Mar 26, 2021

The floating bearings ("bobbins") should spin freely in your fingers. If you grab the disc, tug it back and forth, and it doesn't move that's bad. If they make a loud noise when stopping, like windshield wipers on a dry windshield, then they need to be oiled and broken free. I would not suggest spraying solvent all over them as any fluid on the brake disc is bad. It's best if you drip some oil into the channel of each bobbin, then spin it to fully lubricate. I have to do this about every oil change to keep the discs quiet. Not sure if this is a common problem for floating discs, but certainly common to the 821.

gatdammit · Mar 26, 2021

bicycle chain or gun lube in a squeeze bottle with long applicator tip is best.

Saifmamoun · Mar 26, 2021

even after lubrication they are still soo tight and i am not able to turn them by hand !!

Saifmamoun · Mar 26, 2021

gatdammit said:
The floating bearings ("bobbins") should spin freely in your fingers. If you grab the disc, tug it back and forth, and it doesn't move that's bad. If they make a loud noise when stopping, like windshield wipers on a dry windshield, then they need to be oiled and broken free. I would not suggest spraying solvent all over them as any fluid on the brake disc is bad. It's best if you drip some oil into the channel of each bobbin, then spin it to fully lubricate. I have to do this about every oil change to keep the discs quiet. Not sure if this is a common problem for floating discs, but certainly common to the 821.

no loud noise when stopping or on high speed breaking.
what if bobbins is not moving freely after lubrication, should i buy new disks ???

krolinked · Mar 26, 2021

Might just need time to break free some more especially if the have rusted a little or something.

Araitim · Mar 26, 2021

Those bobbins are supposed to be snug. They are semi floating design. Same premise as floating but there is a wave spring/washer between the C clip and the disc itsself. It shouldn't spin by hand. There is a nice technique using a bolt that fits inside the hole of the bobbin, a nut, a drill and some brake cleaner that frees it up but it still shouldn't be loose enough you can easily spin it with fingers. That spring washer allows the rotor to float but without all that excessive rattling at red lights. One isn't better than the other. I researched this to death because I was dead set on making it full float but for anyone short of a track only bike it makes zero difference other than less noise. The front calipers are known to have piston issues and need cleaning for many(not all). Cleaning the pistons by pulling the pads, then the caliper and working some cleaner around the pistons with a toothbrush might help. Also look at the surfaces that the pas hits I'm the caliper. The vet edge of the pad hits the caliper. Often that area can gum up. Clean that and apply some brake grease to the surface as well as the other points that the pad touch the pistons and caliper. Google "cleaning motorcycle brake bobbins" and check out the drill technique.

Saifmamoun · Mar 26, 2021

Araitim said:
Those bobbins are supposed to be snug. They are semi floating design. Same premise as floating but there is a wave spring/washer between the C clip and the disc itsself. It shouldn't spin by hand. There is a nice technique using a bolt that fits inside the hole of the bobbin, a nut, a drill and some brake cleaner that frees it up but it still shouldn't be loose enough you can easily spin it with fingers. That spring washer allows the rotor to float but without all that excessive rattling at red lights. One isn't better than the other. I researched this to death because I was dead set on making it full float but for anyone short of a track only bike it makes zero difference other than less noise. The front calipers are known to have piston issues and need cleaning for many(not all). Cleaning the pistons by pulling the pads, then the caliper and working some cleaner around the pistons with a toothbrush might help. Also look at the surfaces that the pas hits I'm the caliper. The vet edge of the pad hits the caliper. Often that area can gum up. Clean that and apply some brake grease to the surface as well as the other points that the pad touch the pistons and caliper. Google "cleaning motorcycle brake bobbins" and check out the drill technique.

Thanks for your reply
I cleaned them using drill technique, still not moving by hand.
I will try to clean the pistons. The disks are still new and the pads are 2 days old.
I will get back with feedback after cleaning the pistons.

nickwst4 · Mar 26, 2021

I guess most Ducati forums have been round this one. On the ST group, we feel that relieving some of the clamp pressure of the bobbins works best. Using a chisel-end screwdriver, lift the petals of the bobbin spring slightly (some people say bend the washer itself but that only forces against the spring anyway) with the end result that the bobbins are much easier to turn by hand. This usually cures the problem.

However, you say the discs (complete with bobbins and carriers?) are new? If the discs are new, the bobbins cannot be seized up, but have the disc carriers been assembled on the hub to run true?.

When bedding new pads in, be careful to release the brakes just before you come to a standstill, otherwise material from the fresh pad can deposit on the disc and cause juddering and the only cure is to re-surface the disc with abrasive paper.

I'd be looking at whether the discs have been assembled true, and whether the pads are free to move.

Good luck.

Saifmamoun · Mar 26, 2021

nickwst4 said:
I guess most Ducati forums have been round this one. On the ST group, we feel that relieving some of the clamp pressure of the bobbins works best. Using a chisel-end screwdriver, lift the petals of the bobbin spring slightly (some people say bend the washer itself but that only forces against the spring anyway) with the end result that the bobbins are much easier to turn by hand. This usually cures the problem.

However, you say the discs (complete with bobbins and carriers?) are new? If the discs are new, the bobbins cannot be seized up, but have the disc carriers been assembled on the hub to run true?.

When bedding new pads in, be careful to release the brakes just before you come to a standstill, otherwise material from the fresh pad can deposit on the disc and cause juddering and the only cure is to re-surface the disc with abrasive paper.

I'd be looking at whether the discs have been assembled true, and whether the pads are free to move.

Good luck.

I will try to relieve some pressure using screwdriver. This sounds a solution since they are very tight.
The disk bobbins and carriers are new but i dont know why they are soo tighten.
Hopefully this will work. Thanks for the advice

gatdammit · Mar 26, 2021

Sorry, my dealership replaced my rotors very early in my ownership. I have a set of Brembo rotors with full floating rotors - no springs or washers. I only have floating bobbins. I put a thin bead of oil on them occasionally and make sure they spin freely. When they lock up, brakes rattle and make a lot of noise.

BadToTheBown · Mar 26, 2021

Read about this problem, I use silicon grease on my pistons and elsewhere and seems work fine, just an idea...

nickwst4 · Mar 27, 2021

Do make sure you use compatible grease on calipers and pistons!

In the last year I've messed-up several master-cylinders and calipers by using the wrong grease just because it was in a convenient tube and the same colour as proper red rubber grease! At my age, that's a very stupid mistake to make because the rubber absorbed solvents and swelled, seizing the units completely.

As BTTB says above, any silicone grease may be OK and Brembo repair kits include sachets of what certainly looks like silicone but I'm never going to use anything that doesn't hydraulic mention rubber compatibility again!

BadToTheBown · Mar 27, 2021

The SIL-GLYDE is what's on mine, with the radial master cylinder, these are the best feel brakes I've ever had, easy to modulate, no vib, no sticking...good luck...

Saifmamoun · Mar 27, 2021

Update

Cleaned everything but still have the same exact problem so i took the bike to well known mechanic, he inspected everything and came up with the following conclusion

The disks is not well mounted on the rim due to uneven surface, so he will sand plast it and level it and i will give it a try tomorrow.

Knowing that he told me that the rim received a big hit in the past.

I will keep you posted

BadToTheBown · Mar 27, 2021

I can see the rim, maybe spokes, being bent but the hub? Maybe the rotor mounting surfaces where not made as orthogonal to the axle as they should have been. Someone with a large enough throw on a lathe could rectify that fast and absolutely tell you what your rim runout is. Best of luck...

gatdammit · Mar 28, 2021

Uh, that sounds like a common car problem diagnosis. I've had warped rotors cause vibes under braking. I mean, can't hurt to resurface the rotors but if the wheel is that bent, it would cause vibes under all driving conditions, not just braking.

I don't know how you damage rubber bits by greasing the bobbins. I don't spray anything on the calipers and always clean the rotor well after lubing the bobbins. My favorite was a gun lube that came in a syringe with a very fine applicator nozzle. Drop a little bead in the race and spin to coat. I now use a spray silicone, which works but is a lot messier as it's not as precise.

Saifmamoun · Apr 3, 2021

Nothing worked out until now.
I am going to change the disks again, if it doesn't work i will buy new rim.
I will update you

Saifmamoun · Apr 3, 2021

Hello
I removed the calipers my self to check before buying new parts, and i noticed that the disk is touching the caliper it self not the pads!!! And neither the dealer or the mechanic didn't noticed.
Is that normal???

If it is not normal how could i center my disk to be in the Middle of the caliper.

Knowing that it is only the left caliper is hitting the disk the right one is in the Middle.

Thanks

gatdammit · Apr 3, 2021

The disc should have positive/static contact with the pads only, nothing else. I would think the disc would have witness marks/damage from contact with the calipers. Short answer = bad.

If the caliper is mounted properly and the pads are installed correctly, I don't see how the disc could be contacting the caliper. Unless you have the wrong sized disc installed.

Front brake vibration / tried everything

Saifmamoun

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gatdammit

BadToTheBown

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