Ducati Sporting Club UK > Model Specific - Discussion, Technical Problems and Help > 999 / 749 > Brakes...again !!

[Gizmo]

Originally posted by Twinfan
Hmmm. I still don't think it's "right". A design feature it may be, but it shouldn't be there in my opinion. I wonder if this 'feature' contributed to the fault with my brakes...

You can't get rid of it easily, the stiffer the fork and the more true the rotor the less the rotor knocks the pads back so its just the deflection of the piston seal rubber returning the pads. Wobble the rotor agaisnt pads on a paddock stand and it'll spin freely as theres nothing preventing the pads going back. When you are riding the twist in forks and wheel axle can do just that although on modern bikes everything is stiffer and less likely to flex.

All that can grab a brake is pads not retuning because seal rubber isn't correct, ,something blocking the return of fluid ( you'd notice it as you apply brakes as lever would feel hard or not move at all) or the pad actually stuck in the caliper becasue of dirt or grit in which case it would wear pad and heat rotor up, it would take a lot of heat to presurise whole system enough so that fluid expands to drag brake to a point where it locked.

in the Ducati 999 book by Alan Cathcart theres a small section on the design of the brakes/master cylinder where Tierblanche says he wanted a lower/flatter master cylinder to get into the fairing he'd designed, the whole system was modelled up in 3D cad before any parts were made. Not sure if the caliper design was anything different to brembo's normal OEM range but the master cylinder was totally new although that could just be the resevoir bit.

[Twinfan]

I tell you what Gizmo, I wish Ducati had sent my brakes to you and not the factory/Brembo. I bet I would have had an answer as to the problem immediately!!!!

[Gizmo]

Originally posted by Twinfan
I tell you what Gizmo, I wish Ducati had sent my brakes to you and not the factory/Brembo. I bet I would have had an answer as to the problem immediately!!!!

Nope, don't claim to be an expert but luckily i do product management for a UK mountain bike company ( very high end, race bikes, won 3 out of the last 4 Downhill World Cup championships) who use a lot of disc brakes so work very closely with another UK based company who manufacure disc brakes for pedal bikes and also OEM stuff for motorbikes. I've seen quite a lot of development as we've tried to get weight out of systems, alloy rotors, smaller master cylinders, adjustment of pads ( mountain bikers hate that grab, they think its costing them valuable power). We've had brakes that expand to the point wher they lock up ( mainly closed systems), different sizes of rotor for DH type use because of the heat/expansion problem, split rotors, 2/4 or 6 piston designs and the worst thing is you just have to ride it to find out whether it works, stuff that looks great in CAD or on paper occasionally doesn't work as intended.

I only know the bit about the seals because we had a system a few years ago where the pistons didn't retract as far, the company concerned explained how the seal compressed and returned piston and that they were redesigning the shape to increase pad pull back.
I know from temperature testing I've sen how much heat gets into the systems and thats on a tiny capacity MTB brake.

if your brakes locked up then i can only think of a few things that would cause it

1) heat build up and expansion to a point where fluid couldn't go anywhere so expanded pads onto rotor.
2) swarf or a piece of dirt in the system which blocked the return of fluid
3) pads stuck fully out and not returning at all because of dirt
4) problem with the rubber seal where its reacted with fluid causing swelling. this can hapen if you use DOT in a mineral system ( citroen type) but i don't know about the opposite way round

None of these is easy to check really as after the accident its all cooled down or if there was dirt in the system it may have moved and I'm sure you'd have noticed if the pads were fuly out preventing the wheel from turning.

brembo will know all of this and a lot more so I can't work out why its taken so long to get back to you.

[Il Pres]

Just logged in to confirm my 999my05 bis has the same "problem" . I went crazy to fix the "grabby" brakes with no luck. I'll call my Ducati dealer soonm to see if it's a standar feature