brake switch et al

reborn55 · February 08, 2009, 08:48:35 PM

Getting ready to get POS ragtop on the ground and go to upholstery shop. Doing a routine check, found that the brake lights are not coming on as quick as I think they should. Pedal has to be almost to be as full pressure(engine off) for the light to come on. If you remember I installed under floor remote dual cylinder and ran front brake lines to discs through Midland booster. With the car in the air and in gear it take full brake pedal to stop the rear wheels.. Don't know if theis is normal--don't think so. Did this with single pot also. I have bled the brakes numerous times and have a good pedal. Rear lines run throught a brake pressue switch, residual valve and Wilwood proportioning valve. I have tried messing with the valve but not sure if it is doing anything. Car stops well on the road but am not sure if the rear brakes are doing what they are supposed to do. In turn if the pressure is not to good then the stoplight switch is not coming on soon enough. Don't know why?/if pressure is low. Would a lower pressured switch help or should I do some more troubleshooting. Little help would be appreciated.--Thanks

enjenjo · February 08, 2009, 09:07:11 PM

I have never worked with brakes that were boosted on just the front, so I am at a loss to say how they should work. If you are using a pressure actuated brake switch, they are notorious for doing just what yours has done.

reborn55 · February 08, 2009, 09:12:43 PM

Guys at Brake Tech Solutions guided me into the line hookup as far as using the Midland booster.
I guess your are saying to replace it with a lower pressure type switch.

enjenjo · February 08, 2009, 10:09:43 PM

Quote from: "reborn55"Guys at Brake Tech Solutions guided me into the line hookup as far as using the Midland booster.
I guess your are saying to replace it with a lower pressure type switch.

I am not saying the brakes are wrong, I just don't know that system.

With the pressure type brake switch, they don't seem to last long without taking more pressure to operate. It's the nature of the switch. I use a 60 chevy truck mechanical switch, they hold up good, and work off pedal movement, not pressure.

paul2748 · February 08, 2009, 10:10:17 PM

Go to a mechanical switch. If adjusted right, they go on immediately when you touch the brake pedal.

wayne petty · February 08, 2009, 10:41:09 PM

my thoughts are also going mechanical..

spring loaded...

i don't know the application of this switch but i found it here

http://www.classic-car-accessories.com/electrical/

one of the 415 switches

my sister had a rover 2000tc with dual boosted remote masters.. one for the front brakes... one for the rear... both ends were disc ..

i just cannot understand how one end being boosted is going to work... the difference in line pressures is going to be huge...

reborn55 · February 08, 2009, 11:25:16 PM

I guess with the way the Midland booster works--off pressure and not so much off vacuum the assist is not as great as with a conventional booster. Pedal feel is basically the same and car does stop better. As far as applying brakes, I was not getting the rear brakes to apply any better with the old single master cylinder. Still had to apply full pressure to get wheels to stop while up in the air. I am going to check with BTS tomorrow and get their opinion. thanks

wayne petty · February 09, 2009, 01:41:40 AM

here is a link for everybody... the cole hersee brake light switch catalog..

only two pages...

but a bunch of different switches are shown and described...

http://www.colehersee.com/pdf/L-Stoplamp.pdf

as for the rear brakes... how tight is the adjustment... can you stick a screw driver through the adjusting hole and with a flash light see how far you can push the adjusting wheel forward and back... (not rotate)

you will have to move it several times back and forth to get a good idea... and the parking brakes if they work the rear shoes will have to be released...

if you can see more than 1/8" of fore aft movement ... your brake adjustment is out of whack... and it will take a full stroke of the pedal to stop the rear wheels...

i also take it that your drums were turned.. so there is no bell mouthing of the drum... this makes it really hard to get a proper adjustment when new linings are installed..

one last thing... short shoe linings towards the front of the car...

i have even caught my self putting two primary linings on one side and two secondary linings on the other.. i have also found a bunch of cars with two adjusters with left hand threads or two with right hand threads..

this causes the self adjuster to slack off on the adjustment... instead of keeping it tight... i have even found both sides swapped.. so they both backed off every time the car was backed up...

i am not saying that you have done anything wrong... but these are things that i have run across in my years of fixing cars...

Bruce Dorsi · February 09, 2009, 07:46:24 AM

Some thoughts:

(1) If the rear drums have been cut, it is possible that the arc of the brake shoes does not match the radius of the drum.

Remember when arcing brake shoes was a standard part of doing a brake job?

Rubbing some chalk across the brake linings and checking the chalk pattern after the brakes have been applied will indicate how much of the brake shoe is actually contacting the drum.

(2) Many Combination valves incorporate a hold-off valve for a disc/drum system. ......You did not mention having a combo valve or a hold-off valve.

Front disc brakes will begin to operate at lower line pressures than rear drum brakes. .....At low speeds, the front brakes will do most of the stopping before the rears are sufficiently activated.

The hold-off valve (a.k.a. metering valve) delays the operation of the front discs until the pressure to the rear brakes is sufficient to overcome the brake-shoe return springs and the rear shoes begin to contact the drums.

Installing a hold-off valve in the front brake circuit will also help minimize nose-diving caused by unevenly applied brakes. .....Weight transfer is a different matter.

(3) As others have already said, if the rear brakes are not adjusted properly, the front discs will be fully applied before the rear shoes travel far enough to stop the drums.

(4) Although the hydraulic (pressure-type) brake switches are not known for longevity or high-amperage durability, they can be more reliable by using a relay activated by the switch to turn on the brake lights.

It is possible that your rear brake circuit is not building enough pressure to activate the light until you are near the end of the pedal stroke. .....This again, may be caused by improper adjustment of the rear shoes.

If the pressure switch is bad, or going bad, it may not be operating properly.

enjenjo · February 09, 2009, 09:40:11 AM

The cole Herse 8486, or 8487 is the one I use. They are weatherproof

rumrumm · February 09, 2009, 01:08:11 PM

I used the mechanical switch with the arm that is actuated by the brake pedal. It is adjustable as to when the lights come on based on how far the pedal is depressed. Very accurate. I used an inline switch on my previous street rod and never liked how it worked, although I have to state that it has lasted since the car was first on the road in 1988.

Topsterguy · February 09, 2009, 01:24:51 PM

I used to Cole Hersee #8486 lever mechanical one on my last couple of cars and they work great. I replaced the inline ones for the same reason - the brakes have to be on heavy to work cuz a hot rods lighter I guess. Even the lower pressure ones you get from rod shops aren't that reliable I found.

The Paisano · February 09, 2009, 04:05:57 PM

Quote from: "wayne petty"my thoughts are also going mechanical..

spring loaded...

i don't know the application of this switch but i found it here

http://www.classic-car-accessories.com/electrical/

one of the 415 switches

my sister had a rover 2000tc with dual boosted remote masters.. one for the front brakes... one for the rear... both ends were disc ..

i just cannot understand how one end being boosted is going to work... the difference in line pressures is going to be huge...