hyd brake light switch

[arc40s]

Question is does a Harly Davison hyd brake light switch last longer than a stock reproduction swith from C& G or Drake?
Is there a specific part # to look for?
used for 39-48 Ford master cylinder.

[19Fordy]

If you do a search for harley brake light switch this will come up along with other info. The Harley switch requires less pedal pressure to activtate it.
http://www.fordbarn.com/forum/showth...e+light+switch

[estout81]

I have a Harley brake lite switch on my '48 F-1 that works with very little pedal pressure. Don't know how long it will last as it has only been on since spring. The ones you get in the parts stores don't work very good. Too much pedal pressure to turn lite on.

[DICK SPADARO]

To answer your question about the use of this switch. I have been selling this switch as a replacement for the OE style hydraulic brake light switch. This was a result of the customer complaints that the OE style switch required too much pedal pressure to activate with their upgraded disc brake conversions. In other words with the OE switch by the time the stop lights came on you locked up the brakes.

It requires less line pressure to activate so your brake lights come on a fraction quicker, which might save you from getting rearended by some blonde haired Lucy talking on her cell phone.

As for longevity if you keep the moisture out of your brake system it should last for a long time. To install this switch requires changing from the bullet connectors to a spade connector on your brake light circuit wire.

[arc40s]

Sounds good to me. Please advise the part # for this switch. I started 6 years ago with complete new brake system with Dot 5 fluid. New w. cyl, new master, new hoses and new complete steel brake lines, resisual 10# front 3# rear and ajustable porposirsinal valve .

Pedal has always been spongie no matter how many times I bleed brakes. I still do not feel warm and fuzzie when I need to make quick stop. Disc brakes in front stock 1940 drums in rear.
Suggestions?

[DICK SPADARO]

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Well start here the 10 lb valve goes to the rear drum brakes not the disk side, 10 on the disks and you wear the pads out. Next throw away that water spigot valve also, that is a race car part. What master cylinder did you use?

[arc40s]

Mustang two resovor 1" piston.
This car is not Street Rod. has stock flathead w/ 3-speed trans and 3:54 banjo rearend.

[DICK SPADARO]

Thats a good sign but, Was this a disc drum unit or a drum drum unit?

[arc40s]

Not sure and not sure how to find out. It did not have a brake booster set up so I supose could be drum/drum mastercylinder. Things I did not know to check in beginning..... suggestions?

[36tbird]

Drum/drum and disc/disc m-c's will have equal sized reservoirs. A disc/drum will have different sized ones and I the larger one goes to the discs.

[DICK SPADARO]

Most drum drum master cylinders have a built in residual line valve if these are used on a disc brake application the line pressure is keeping the pads pressed upon the rotors, adding another in line valve creates another the problem. Your brakes should be rock solid not spongy. If you purchased a kit its good to know the brand. If you just purchased a bunch of parts the potential for problems develop.

Assuming you have the correct master cylinder your 3 lb valve should go to the disc side. If early ford brakes are being used in the rear they have a cam adjuster that limits the return of the brake shoe, no rear line valve is necessary.

[V8 Bob]

Most/all drum/drum (single/dual) and disc/drum master cylinders had check valves (more often called residuals) up to the early/mid '70s, when they became obsolete, because of modern front disc brakes that never used/needed residuals, and rear wheel cylinder cup expanders that prevent air from entering past the cylinder cups. Today, some new/rebuilt masters that had internal residuals initially may not have them installed, so it's always best to check for them in the master you will use before adding any to the system. As noted, install 10# external or stock internal to drums, and 2# external to discs ONLY when the master is lower than the calipers. Using residuals on mid-’70s-up drums is not necessary, but can only help “tighten” the system with slightly shorter pedal stroke as a result.


All drum brake shoes return to a solid anchor with strong springs, but without a residual check valve, a partial vacuum can develop during fast brake release, allowing air to enter past the wheel cylinder cups. Because of this, all drum brakes prior to the early '70s had and need residuals, most often located internally in the master cylinders, but on occasion in-line.

As far as proportioning valves, they have been factory standard equipment on most disc/drum (and some disc/disc) vehicles. The reason is the higher line pressures required for disc brakes for a given deceleration than drum brakes. An adjustable prop valve is a smart addition to any custom disc brake system, as you do NOT want the rears to slide before the fronts, wet or dry. Stay away from the fixed type prop valves, unless replacing one that was factory installed. IMO