Replaced front tyre on my ST4S, opened pads to replace calipers, forgetting to open master cylinder, put them back on the bike now the brakes are locked on (both sides). presume I've knackered something in the master cylinder. Any help would be most appreciated! Thanks.
Presuming the lever is solid? Have you tried opening the reservoir? With something to catch the fluid.
As Jerry says that's the easiest and quickest test,otherwise it could be the pistons are stuck,ST series callipers do need regular cleaning of the pistons . And remember the new tyre Needs bedding in for about 80 miles. What tyre have you put on?
JerryXt, Lever very soft, opened the Reservoir, no spillage or air in the fluid. Michel, pistons are fine, all free. Avon Storms, usually have Mitchelin Pilots which I recommend, we'll see about the Storms!
I once had a similar squishy lever problem that affected the braking,that was cured with a goog clean of the pistons and seals,worth a try and cheaper than replacing anything yet!
any freeplay with the brake lever, without any freeplay the brakes will lock up, there should be an adjustment screw on the lever
Don't adjust the lever, you have a fault so don't try to work around it, fix it! Brakes tend to be quite important, if you have any doubts then get it to a workshop.
Must be an issue somewhere, I never open the top of my mc pot and never had issue you describe. You say opened the pistons up...large screw driver pushing them back or something else?
As above, have one of the pistons slipped out slightly during the process. If you don't already its good practice to clean the pistons whilst the opportunity presents itself. I've always used a toothbrush and diluted washing up liquid. Good luck.
Or if you have pushed the pistons in the caliper back but not straight then that could affect it,really think you should take the caliper off,check the piston movement,remember not to Let them pop out! Give the system a good thorough bleed incase of an airlock,whilst your at it give the pistons and seals,a damn good clean,all of that is cheap and uncomplicated to do,after that if the trouble persists then your talking money. But the ST series calipers are known for getting similar issues when they need a bit of TLC. All this suggestion will cost is a bit of brake fluid and time.
Master cylinder or caliper, I am thinking pistons in the caliper need TLC, master cylinder is far more and another proposition altogether .
Youre not running sps full floating discs and they have got wet, are you?! That feels like they are stuck and you wont move by hand on a stand, needs a good shove
I'd be looking at the pistons in the calipers then. But if you're not comfortable with this, get so,done over who can help you, or get the bike to a workshop.
Thanks guys, as I said the caliper pistons are all fine, zero effort being required to push them back. Something in the system is acting like a one way valve, like when a brake hose collapses, though I have braided hoses so that shouldn't happen, will bleed them as suggested, though I've a feeling a seal has gone in the master cylinder, presume Ducati or Brembo do overhaul kits. One thing I didn't mention, when I put the calipers back on I pumped the brake lever as you usually do to resit the pads but the brake lever didn't go solid, pulling right back to the bar and feeling kinda soft and springy. Bit of a headscratcher this one I know! Will do all the obvious stuff today and see what happens. Will post the cure and cause when I find it!
