Multi 1200s 2013 Very quick and easy question. Somehow the cover of the rear brake reservoir gone missing. I was looking to order a cover from China but before I do that can someone please tell me whether there should be a rubber gasket as well like the ones in the clutch and front brake reservoirs. I cannot remember whether there should be one or not ........ I did say its an easy question
Yes, there needs to be a reservoir cap gasket. The gasket assists in pulling fluid back, which in turn helps to pull the Caliper pistons back once you release the brake lever. By means of causing a vacuum effect in the fluid line.
@Shoboshi - many thanks and also thanks for the explanation - never thought of that . The nice Chinese covers are off the list now as they don't come with gasket and also the gasket is not available as a Ducati spare part. Looks like I will need to buy both cap and reservoir from Ducati unless somebody knows better
They are shown as one part no so I suspect you are correct and you’ll need to buy both.... £12.28 for the pair shouldn’t break the bank tho
Had the same thing happen on my Monster 1200S - at the time I thought a pikey had nicked it, but I wonder in hindsight if it was just loose, and worked it's way off while I was riding. Luckily I had a spare at home. Weird thing to happen though. My first port of call would be ebay for a replacement.
Brake slave pistons are slightly pulled back by flexing of the square rubber sealing ring. While the fluid reservoir may develop a bit of vacuum it would never be enough to move a brake piston. The rubber bellows in the cap is to minimize air to fluid contact in the reservoir and specifically to be sure NO vacuum is created when the level drops due to pad wear
Next time you’ve got a caliper off, m/c cap still tight, in place, pump the lever till the pistons are well out, look at the seal inside the reservoir. It’ll be distended and out of shape. Think you’ll find that’s caused by a vacuum effect. Everything works in conjunction to assist in the minuscule movement that retracts the piston rearward from the pad stopping pads dragging.
I'm sorry but this is incorrect. The bellows main job is to PREVENT vacuum in the reservoir. The cap is vented to atmosphere outside the rubber bellows to achieve this. You are however welcome to believe what you wish. but I would recommend further research
I have to say I think TaskMule is correct You can pump the brakes without the cap on at all and it still returns as normal My understanding is it serves two functions 1) as above to minimise air gap 2) it flexes to reduce the available volume so the fluid can’t slosh about as much reducing the chances of introducing air into the system Just my 2p
Brake fluid is hygroscopic (absorbs moisture) The diaphragm is there to keep the outside air separated from the fluid. It has to be vented on the top side to allow fluid to rise and fall as the pads wear. Pretty sure you can bug the diaphragm separately as a Brembo part. You can certainly buy it with just the lid.
Well, there you go. Having had this explained to me many moons ago, seems it was incorrect. Nonetheless, always time to learn. Cheers.
Problem solved. Got a brand new complete reservoir for £10.79. It's more original than the Ducati OEM for £30+ . I got the real McCoy - Brembo . Its BRE104446650 15ml (45 degree) from DemonTweeks with free delivery. Thank you all
Reading the answers until found someone who would say the correct name. It is not a rubber seal, it is not a gasket, it is a diaphragm. And by its name, no need for further explanation. Only could have come from John. Thanks. By the way, the front brake reservoir is a pain in the neck for many (including me), it leaks time to time, no matter what you do. You can replace the diaphragm and cap, still will leak. I got used to it, every 2 months or so, open it, clean the diaphragm and cap, assembly back with minimum torque (I mean, just turn the shaft of a screw driver, not the handle, a little snug).
