brakes lockup

[jarvis]

run a pure stock class rules say no after market master.Are running disk in rear but for the last three weeks calipers have locked up in the heat race have replaced everything front to back every week and we are not running a porpotion valve could that be it.It also always starts with the right rear

[Egoracing]

Fluid has water in it or is cheap and it is swelling up/boiling and locking the brakes.

[jarvis]

Ok I will use a better fluid.Could it be anything else

[keithbaker]

pinched line or calipers could be bad

[racerkrp1]

Master cylinder not returning all the way back

[stock car driver]

Usually when I have any rear brake issues its because the mounts arent 90 to the rotor, if one is bent just a tiny bit even it will apply side pressure to the caliper piston and the piston will not return into the caliper and THUS its locked up..

I visually inspect my caliper mts every time I change gears, looking at the distance from the bolt to the rotor can be a good quick indicator also you can usually visually see a caliper that is not 90 to the rotor.

[Chaps46]

Don't use DOT5!!

[bushracing67]

Don't use DOT5!!

yeah i found that out this year, that (not a nice word)(not a nice word)(not a nice word)(not a nice word) sucks... the sticking brakes could be a bad rubber hose collapsing as well, check them all if your not running stainless hoses

[jarvis]

Started all over one more time new everything including brackets did use Prestone synthetic high heat fluid. Has anyone had any luck with it. Never the less I will let you
Know this weekend how it turns out thanks for the info guys

[dirty white boy]

yeah i found that out this year, that (not a nice word)(not a nice word)(not a nice word)(not a nice word) sucks... the sticking brakes could be a bad rubber hose collapsing as well, check them all if your not running stainless hoses

seen this many times on stock lines..

[keithbaker]

maybe check to see if your pedal and master cylinder is returning all the way

[Dirtrunner35]

seen this many times on stock lines..

I have never seen a rubber brake hose collapse. It has always been where it is crimped together at the end to the metal. Rust forms under it, squeezing the hose shut.

[stock car driver]

I run DOT 4 fluid. Synthetic attracts and holds moisture, I wouldnt use it in a race car.

[Egoracing]

I run DOT 4 fluid. Synthetic attracts and holds moisture, I wouldnt use it in a race car.

Synthetic is bad but ALL brake fluid will absorb and hold water. That is why on evey bottle it says only use fresh fluid. There are meters on the market that can read the water level.

[stock car driver]

Synthetic is bad but ALL brake fluid will absorb and hold water. That is why on evey bottle it says only use fresh fluid. There are meters on the market that can read the water level.

YES true BUT synthetic is much worse at absorbing or attractiong the water from what I remember.

I havent read about it in years but I remember when the synth first came out everyone was getting soft pedals from it within a night or two.

[dirty white boy]

I have never seen a rubber brake hose collapse. It has always been where it is crimped together at the end to the metal. Rust forms under it, squeezing the hose shut.

the ones ive seen,...rubber com lose on inside,..an plug line up....line look fine on outside!

[Egoracing]

YES true BUT synthetic is much worse at absorbing or attractiong the water from what I remember.

I havent read about it in years but I remember when the synth first came out everyone was getting soft pedals from it within a night or two.

You ever see someone go to the old "racing" synthetic fluid that would NOT mix with regular fluid. They would mix and it looked like burnt jello.

[gadirtracer]

You ever see someone go to the old "racing" synthetic fluid that would NOT mix with regular fluid. They would mix and it looked like burnt jello.

Ego, do you cook your Jello?

DOT 3 or 4 store brand fluid will work on a street stock, just keep the system bleed and the fluid fresh. After every race or two, I'll bleed the calipers to get the old heat soaked fluid out of the calipers and top it back off with fresh fluid.
When I buy brake fluid, I get the small bottles, to minimize the times the lid is removed allowing moisture in.

[gadirtracer]

jarvis, are you using an inline residual valve? If so, which one? Why?
If you have a master cylinder designed for rear drums and you now have disks out back, that's you issue. Some stock masters have the residual valve built in them. Drums require more pressure to operate and the m.c. is holding a set amount of pressure there when you are off the brakes, the components heat up and expand and now your brakes are locked up.

[gadirtracer]

Read this......
http://www.thebrakeman.com/valvetechi