S2R 800 rear brake lock up

[redheinz57]

Hi all in Ducati land, need help,i went out on bike for the first time for a while today. Have just fitted a de-cat pipe to my termis' went about 8 miles when the bike started struggling up a hill (slight incline) the bike came to a stop and i could not move it. Realised the rear brake had locked on, a friend near by help lift rear wheel and walk the bike out of the middle of the road. After about 5 minutes and alot of self doubt i rang Ducati dealer they advised me to get it recovered, but when i went back to bike the brakes had cooled off and released. I rode back about 5 miles to dealer without using rear brake where they promptly put it on the bench saying that they had never heard of a disc brake locking on and asked if i was riding with my foot on the pedal (novice rider but NO). Two minutes later the tech comes out saying he pumped rear brake a few times and it locked on AHHH!!!!!. Recalling previous work done by dealer i remember they had trouble bleeding rear brakes when i had my swing arm powder coated ?. As the said they had never heard of this before all they did today was adjust rear brake pedal play and bleed the brakes. I now have doubts on riding my monster please help :fou: Smilies

[desmo]

either the rear caliper piston is sticking, or the rear master cylinder is not allowing the brake fluid to return, which will probably require a new master cylinder.

I suggest you remove the rear brake caliper with the hydraulic pipe still attached & carefully pump the brake pedal a few times & then try to push the piston back into the caliper, if it is reluctant to move, undo the bleed nipple & try again, if it moves & pushes fluid out of the bleed nipple then your master cylinder is faulty.

Desmo.

[Bodybag]

either the rear caliper piston is sticking, or the rear master cylinder is not allowing the brake fluid to return, which will probably require a new master cylinder.

I suggest you remove the rear brake caliper with the hydraulic pipe still attached & carefully pump the brake pedal a few times & then try to push the piston back into the caliper, if it is reluctant to move, undo the bleed nipple & try again, if it moves & pushes fluid out of the bleed nipple then your master cylinder is faulty.

Desmo.

Beelzebub did that on the Front brake!! Needed a new front brake master cylinder.

[CK & AK]

I agree with the above, but also what it could be: is over adjustment on the push rod - with not enough free play (the push rod into the master cyl from the brake pedal)

The scenario with this is:
When the brakes start to warm up and you get heat expension, it cant expend cos there is no free play, so it pulls the brake on, the more hot it gets.

If under warranty, please ask your dealer to fully check this. It is a quite obvious problem for a mechanic to solve.

Hope this helps

Alan:)

[gary tompkins]

I've had 2 rear m/cyl fail - both on 900's. Caused the same syptoms of disc binding and not releasing properly. Replacement cylinders (£28) sorted problem on mine.

[redheinz57]

Thanks all sugestion are welcome it is a 56 reg so under warranty am going to ride it again tommorrow to see if more free play helps. I am sure they will take your sugestions on board and as i work there i know they will look after me. Many many thanks i now know why they say buying a Ducati is like becoming a member of a family

[russ77]

I stopped to help a fella stranded by the side of the road last summer. The rear brake on his 900 was locked solid, so it does happen. We couldn't work out what was causing it by the side of the road with no tools. The rear disc had got so hot it had turned blue.

Bleeding the system again would be the first thing to try. It is important that the brake fluid used when bleeding the system is the same as the type already in there. Using different DOT types could cause reactions with each other and may degrade the seals. Hopefully this isn't the case. It's more likely that some gunk has got into the lines when bleeding after your swingarm work. Try bleeding again, flushing the whole system through. If this doesn't work, dismantle the caliper and check the cylinder and piston are nice and smooth. The excessive heat may have warped the cylinder too.

Also check the free play in the brake pedal. There should be a few millimetres to allow the pads to disengage when released. If they are allowed to drag a bit, they will heat up, boil the fluid and they'll eventually bind completely. This is why they release once they've cooled down.

Here's a helpful chart for for diagnosing problems with brakes. It's meant for cars but it's still relevant:
http://home.att.net/~m.prendergast-alliedsignal/BRAKCHRT.htm
(http://home.att.net/~m.prendergast-alliedsignal/BRAKCHRT.htm)

Of course, if the bike's still under warranty, take it in and ask someone else to work it out.

[Trent]

A mate of mine had a similar problem on the front brake of a BMW F650 (Brembo Brakes)
Turns out the small return spring inside the master cylinder had broken. Fitted new spring and all OK again.

If the same thing has happened on yours on the rear, then it's a new master cylinder reqd. (I don't think you can get a rebuild kit for the rear master Cylinder)

If they had problems bleeding it after powder coating, then something is definitely wrong...
My guess is the Master Cylinder - bike is too new for the caliper to seize up... (and it looks shiney and cared for in your avitar!)

Yours is under warranty, so you're fine... Others wanting new master cylinders can find them here:
http://www.gprdirect.com/epages/GPRDirect.storefront/45d7f38c007df4942719d9c7b8050716/Product/View/BRE10&2E4776&2E60

[Rockhopper]

Mixing fluids isnt really a big drama, the only one you shouldn't be using is DOT 5. Its safe to mix DOT 3,4 and 5.1 which are the commonly available ones. DOT 5 shouldn't be mixed with anything other than more DOT5!