Brake Swtich

I just added speedway's disc brake kit to my 36.

Kit came with all parts, rotors, caliper etc.
I also bought a their disc drum master, and a 2lb residual valve to repalce the 10lb I had from the drum brakes up front.

Rear brakes are 56 chevy drum

bench bled the master, and did my first round of bleeding last night.
The line for the front goes from the master to a T with the brake swtich, then to the residual valve and then to the front calipers.

I bled it last night and seem to have all the bubbles out, and the front brakes start to lock with pressure on the pedal, but my switch seems to need the pedal to move more now that it did before. I had the same switch with the drum drum set up and mustang drum/drum master, and was plumbed the same as now...
Any ideas why it seems to need more pressure to activate? Could it be the difference in the bore size of the master cyl going from drum up front to disc?

 

In several recent threads/posts here on the HAMB, the general consenus seems to be that mecahnical switches are far more reliable, and predictable, that the hydraulic types.

I know that is an answer to a question you didn't ask, but may be the answer you need. Either the underfloor lever type switch or, if you have suspended pedals, the OEM push****on type is probably a better choice for operating the brake lights.

Ray

 

I have the ch***is engineering pedal ***embly that mouns to the X member

 

That would seem to lend itself very well to the lever type mechanical B/L switch. Readily available from Speedway and many other suppliers, maybe even a HAMB vendor.


Ray

 

Use a '55-'59 Chevy truck lever type switch. They are inexpensive and easy to locte between the brake pedal arm and toe board.

 

First, the residual(s) really should be located as close to the master cylinder as possible.
Second, try bleeding the pressure switch, as a small amount of air can make a big difference in the switch sensitivity.
A change in master cylinder bore size will also affect the amount of pressure for a given pedal input.

 

I was going to say pretty much the same as DrJ this should be the Napa number to the lever switch for a 53 Chevy pickup http://www.napaonline.com/Catalog/C...01953+50014+2014099+25015&Ar=AND(P_RecType:A)

Which should be the same as the 55/59 switch http://www.napaonline.com/Catalog/C...01958+50014+2014099+25015&Ar=AND(P_RecType:A) Fab a bracket to mount it and move the wires and you are good to go.

I have had a Ford style pressure brake light switch on the 48 for a number of years and I lost track of how many of them I replaced over the years. And they do seem to be a bit sensitive to how much pressure they need to operate.

 

would I just crack the threads until I get fluid out of it?

 

Before you replace the switch, follow V8Bobs suggestions. Move the residual back as close to the MC as possible, certainly before the switch, then bleed the switch. Probably will take care of the problem. I know guys will say go to a mechanical brake light switch, but I have been using the pressure type for 30 years without incident.

 

I can try, it is within 6 inches of the master cylinder, with the Ford drums and dual drum master the switch was before the residual and it worked no problem

 

I have a question....why would you want to put the residual valve BEFORE the switch...that would keep (residual) pressure on the switch all the time, though perhaps not enough to keep it activated with 2# disc R/V. Is that the goal?

Second, within the last week there was a loooong thread roundly criticzing hydraulic switches....with very few in favor.....make up your #@&! minds already !

Ray

 

I put the switch before the res-valve because I was worried that it would activate the switch.

 

And I agree with that reasoning.......in the absence of compelling reasoning to the contrary.

My question about that was intended for the previous poster, Fat47.

Ray

 

The brake switches operate around 50 + psi, way more than a 10 psi residual. Keep in mind most drum brake systems that used hydraulic switches had built-in residuals in the master cylinders. Locating the switch down stream from the residual will make it more sensitive.
To bleed, loosen the switch just enough to allow fluid to flow past the threads with light pedal pressure and tighten. Repeat once or twice until no air is seen or heard.

 

thanks all, will give it a try.

I found this here on the hamb

"
If you use disc brakes in front, and want an inline pressure swith, you will need a LOW PRESSURE brake switch. With disc brakes, you won't develop enough line pressure to activate a regular in line switch. After a lot of searching, I finally found a well priced low pressure switch from painless. (some think they are made of gold) I have had my ****xt xod for 20 years abd have never needed a porpotioniong valve. "

 

Just the oposite is true, disc brakes require more pressure than drum brakes, the reason proportioning valves are required on disc/drum systems.
I would look into a good mechanical switch in the future, as others have suggested. The sensitivity can be adjusted, they don't/won't leak, and some, like the ****on style from Ron Francis, can handle high amperage halogen bulbs without the need for a relay. JMO.