Hi all. I am looking for advise. I have a 2000 748s that judders under braking. I have cleaned and de glazed the discs, also cleaned the callipers and all the pistons are moving freely. Any suggestions on the next step or should I just replace the rotors? What are decent replacements as Brembos are out my price range?
Check if your steering head bearings are loose, if your front wheel is installed correctly, if your front wheel is round, if your front wheel bearings are shagged.
Have you checked the free movement of the bobbins between the disc and the carrier ? There should be a small amount of movement between the disc and the carrier which you lose if the bobbins are seized. Simple job to free them up using an M5 bolt, nut and electric screw driver. Andy
Fit the bolt through the bobbin and put the nut on hand tight. Use the electric driver to spin the bolt. This will break the bond of any corrosion. Undo and repeat for each bobbin. If you cannot resist the temptation to use something like WD40, make sure you clean all traces of it from the disc surface with brake cleaner. Should take about 10 minutes. Andy
Drill the buttons out and fit fully floating bobbins,less drag,sound good,IMO Allows the disc to follow its natural path,came as standard on a lot of dukes! Cost around £50 and 1 hour of your time!
I had the problem with my SS. Cure? Take the discs off; then thoroughly clean the disc bearing surfaces on the hub and the backs of the disc as well. When re-fitting lay the wheel flat (I laid mine on an old tyre to protect the other side) then lay a cleaned disc onto the wheel. It should spin round easily when pushed with a finger. When fixing holes are lined up, try putting equal light pressure at 180 degrees roughly midway across the braking surface to see if the disc rocks slightly - then try another position. If it does rock, spin it again to a different set of holes. Add the bolts and spin the all down with fingers, then using torque wrench at lower setting to partly tighten opposite pairs all round - keep the same process going increasing the torque setting until it is correct all round.
I don't see how that will change anything? If the problem has just started to show its either a warped disc or fouled bobbins!(as long as the tyres balanced) he's checked the calipers are free so why would reseating the discs make a difference,check out " black shadow engineering " for their info on disc problems and cures,and prices for floating bobbins,I've used their products and they work fine,a good fast quality service with backup help and advice if problems arise !
I'm not trying to be contentious,it's just I've recently encountered this problem on my 851,and put my 900ss wheel/discs on and it was a instant fix, so I tried the drill/bolt method on my 851 discs and wasn't happy,so I drilled the rivets out and replaced them with the bobbins from black shadow engineering and my experience has been noticeably less drag and the brakes are just as good as they always were,no shudder but a bit of noise at walking speed,just the same as my mates superlite with factory discs, So a cheap fix for me and I like the chatter of floating discs,I did find that I had to fit an extra washer/shim to remove some of the side play on the discs,
I'm not trying to be contentious,it's just I've recently encountered this problem on my 851,and put my 900ss wheel/discs on and it was a instant fix, so I tried the drill/bolt method on my 851 discs and wasn't happy,so I drilled the rivets out and replaced them with the bobbins from black shadow engineering and my experience has been noticeably less drag and the brakes are just as good as they always were,no shudder but a bit of noise at walking speed,just the same as my mates superlite with factory discs, So a cheap fix for me and I like the chatter of floating discs,I did find that I had to fit an extra washer/shim to remove some of the side play on the discs,
Yes,I'm just sharing my experience,you pays your money you make your choices, this was the most effective/cheapest method I could find,I like messing around finding solutions (i have a brand new pair of discs)
Over the years I was always surprised how much effect water penetration can have when it gets in between the disc and the hub (which it will do), the corrosion can form quite quickly and the strength of it building up doesn't seem to 'squeeze' outwards, so I guess it can create an uneven bed between the two components. That's why I clean it meticulously - but it may also be because of race preparation. Regardless of talent and speed, reliability is of huge importance; so when others slung things together and we didn't is probably why we won and they didn't.
