Today's mystery...

[fourstonebloke]

OK, Today's problem. Removed ABS etc 2 weeks ago from '04 1150GSA. All good. MOT today. Rode the 6 miles there, passed all good, no advisories. Riding back, got 3 miles in and front brake seized on almost solid. Loss of all lever pressure. Left it 3 mins, all good again. 2 miles later - same thing. 3 mins, all good. Now home. Brakes couldn't have been binding badly at MOT as they were checked. But to seize, must be pressure on pots. If I'm not squeezing, must be fluid expanding. If fluid expanding, must be heat. If heat, must be friction. Only friction source can be dragging pads? Any ideas?

 

[DrFarkoff]

What sort of hoses are fitted?

If you have the older design Rubber hoses ?

They do de laminate and collapse inside ! Creating a one way valve

 

[Paul G (BHT)]

What sort of hoses are fitted?

If you have the older design Rubber hoses ?

They do de laminate and collapse inside ! Creating a one way valve

This ^^

If they are the original hoses you need to replace them.
Happened to me too so I replaced them with some steel braided hoses from MotorWorks.

 

[fourstonebloke]

What sort of hoses are fitted?

If you have the older design Rubber hoses ?

They do de laminate and collapse inside ! Creating a one way valve

Braided.

 

[DrFarkoff]

Braided.

Okay So Just some ideas

Did you adjust the Stroke of the brake piston on the lever? Do you have a little free play between off and feeling the master cylinder piston move? If you don't this can be an issue

Also remove the brake fluid reservoir top and look down in, You will see a larger hole and a tinier one to the inboard side of the piston stroke It should flow fluid when you release the lever It may be blocked and need cleaned BE VERY Careful its is a tiny hole and you can Break off a safety pin head in the hole ! I know as I had to fix the mayhem after someone doing this But it can be done"

Did the pistons/pads move back with pressure from your fingers ? Those callipers especially the Tokico ones had a bad habit even when just 6 months old of salts building behind the wiper rings and jamming the pistons so much so they would not retract So then you got some heat + fluid expansion and seizing brakes Just a matter of stripping and cleaning and light lubrication!

The Master cylinder.... Dear Gawd having to ask this!! Is your lever a bit floppy near the other end of travel ??

Could be the piston is not retracting out the whole way and you have residual pressure in the MC

 

[fourstonebloke]

Yes tothe lever stuff.All good at the resoviour and bleeding up through it, and plenty of upflow on squeezing. Brembo calipers. One pot was slightly sticky, but not stuck - good glean and all was good. Nothing out of the ordinary with the lever. Brakes seem to have about the same drag as they always have had when lever released, which is to say the pads brush the disc, as they always have, which would seem to rule out increased residual pressure in the system. Also, I have ot push it on/off my turntable, and it is/was rolling as normal. It was a case of sudden onset mid-ride!

 

[DrFarkoff]

In that case just be VERY careful and monitor it and carry a spanner for the bleed nipple and see if that frees it off any quicker???

No blue disc or Excess heat when you pull over ??

Perhaps lower the level in the reservoir a tad especially if you have new pads???

 

[fourstonebloke]

I'll do that. No, didn't change the pads, so all is exactly as it has been. I felt the disc and calipers the second time it did it and was expecting a lot of heat. Cool enough to grasp with bare hand, so what I would consider normal for a not very brake heavy short run on a cold day.

 

[Riceburner]

Braided.

How old are they?

Just because they're braided doesn't mean they'll last forever. The inner is still a rubber tube and so still vulnerable to rotting and disintegrating internally.

The braiding is there to stop "outward" expansion while braking (ie to fight the tendency of the rubber tube to expand when the internal pressure increases).

 

[maztm1]

OK, Today's problem. Removed ABS etc 2 weeks ago from '04 1150GSA. All good. MOT today. Rode the 6 miles there, passed all good, no advisories. Riding back, got 3 miles in and front brake seized on almost solid. Loss of all lever pressure. Left it 3 mins, all good again. 2 miles later - same thing. 3 mins, all good. Now home. Brakes couldn't have been binding badly at MOT as they were checked. But to seize, must be pressure on pots. If I'm not squeezing, must be fluid expanding. If fluid expanding, must be heat. If heat, must be friction. Only friction source can be dragging pads? Any ideas?

My GSA once had the brakes bind on and stop me,took it to rainbow and they diagnosed it as the pads being a tight fit in the calipers,checked over cleaned and the pads were filed,or rubbed down a tiny bit,they were fine after that until worn out .

 

[Steptoe]

My GSA once had the brakes bind on and stop me,took it to rainbow and they diagnosed it as the pads being a tight fit in the calipers,checked over cleaned and the pads were filed,or rubbed down a tiny bit,they were fine after that until worn out .

I once a had box of Ferodo 2125 brake pads where every set of pads needed a few strokes with a file at each end to make them fit into the caliper.

 

[Riceburner]

I once a had box of Ferodo 2125 brake pads where every set of pads needed a few strokes with a file at each end to make them fit into the caliper.

I think I've had that a couple of times, only to be expected really with modern manufacturing QA methods.