Riddle me this Batman...

After driving for a bit on bumpy roads the first application of brake hits the floor, a puick short pump will have it hard.
I have bled the lines and replaced the master cylinder, the old one was new also (6months use) but always had same problem but got progressively worse with internal leak I assume from bottoming out the piston constantly.
I'm assuming it's got to do with my rear drums not being adjusted properly, although they have new cylinders and pads bit one of the adjusting eccentrics is rounded so vice grips it is...
I have no leaks and don't loose any fluid.

Harley

Did you fit a spring into the new rear cylinders between the two pistons? Some of the modern ones have stiffer seals which stick a little and need a little assistance. I understand the spring from a light fitting does the job.

You need this

http://www.2cviking.com/catalog/product ... ucts_id=66

Harley,
take the drums off and check to see if the pistons move back into the cylinders and out of contact with the brake shoe after each brake application.
This problem is not caused by the composition of the O ring seal, it's the shape of the dust seal which is incorrect.
It's been around a long time, first time I found a set of cylinders like this was back in 1995 and the manufacturers are still churning out useless cr@p...

The best cure is to install a light spring between the pistons, so that they always stay in contact with the tip of the brake shoes.
Using the old dust seals is another option, as long as they were the correct shape...

Ken

The same thing is going on with the (front) disk-brake piston seals, the new seals are to soft, so the piston backs off to far when releasing the brakepedal. If you brake then you need to move the pedal much to far to get pressure.

This is discussed with the manufactures by a small Dutch 2cv service station (Duck-Hunt) but without any results..

If got this problem at my Ami 8...

So if you can try to use old seals as long as possible.....


@ Harley; Are you sure theres no Vapor lock involved (boiling brake fluid)????
Is your brakepipe running near the exhaust??? Wrap some aloy foil from a windscreen protector (against the sun) around the brakepipe put some tywraps around it then....

Great replies everyone, a wealth of knowledge here!
Viking the rear cylinders are new from Viking raid, I also had these symptoms then.
Thanks Ken, I will have to check the rear return and look into a light spring, it does go with my feeling of it being related to the rear adjustment. ..
A "new" GS powered 2cv here was recently passed by an engineer on the premises it had a rear brake bias valve, I might look into that.
Lpgo you have me thinking now, I check proximity to exhaust. ..

Harley

Double post

What Knighley said, the springs out of rear lights do the trick.

Harls. We sell and supply plenty of rear wheel brake cylinders from the new Italian supplier. All these have that problem due to O ring being too short allowing the dust cap to push the pistons back. I replace all O rings and problem gone. It used to be Bendix cylinders but they are long gone.

Harley it is very simple....

If you have bleed the brakes, are they working well then??? and after driving a whil they don't work well, then its probably vapor lock...

If you can't bleed the brakes well at the first place then it is probably pistons moving in to far...

p.s. ofcourse you did adjust the brake-shoes with the 14mm spanner at the backside of the drum...... did you...