The Stovebolt Site Forums The Shop Area The HiPo Shop Brake Pressure Gauge

I would like to hook up a pressure gauge temporarily for testing. Full disclosure this is not for a Stovebolt. To give a bit of authenticity though, I may do the same to the truck just to see what pressures I've got there. I have less than 2" from the female bleeder face to the frame. All the gauges I've seen require more than that. Is there a way to plumb something up to fit to the bleeder threads and still seal?

Dennis

You ought to have enough room on the front end if you put it on stands and turn the wheels. On the rear, I'd disconnect at the differential union and check there. As long as your tubing is in good nick, you should be fine doing that and most of the brake pressure gauge kits include adapters for that union fitting.

Buy a replacement bleeder screw and braze a short piece of steel brake line to the end. You'll need to drill a small hole straight through so you can tighten the screw into the wheel cylinder and avoid getting any leakage. Adapt the line to a pressure gauge and bleed all the air out of the adapter by leaving the fitting slightly loose at the gauge, then tightening it. Even a tiny air bubble will result in a false reading due to the air compressing and giving a spongy feel to the pedal.
Jerry

Thanks for the suggestions guys. Jon, I see what you are saying about going to the union for easy access. Yes, plenty of room up front. Only an issue at the rear.
Jerry, I can't braze but do have a mig. I'm not quite following what you're saying but will take a look at the bleeder tomorrow.

Dennis

I'm talking about putting an extension onto a bleeder screw, and adapting the gauge to that line. A bleeder seals with a tapered seat ahead of the threaded part so unless you duplicate the seal, you'll create a leak around the threads when you loosen the bleeder to get the brake pressure to the gauge.
Jerry

Many circle track racers run a brake bias (or balance) panel with pressure gauges. Speedway has them but you don't need the whole system. However, if there is a schematic you might pick up a few tips.

https://www.surpluscenter.com/Gauges/Pressure-Vacuum-Gauges/?page_no=1 Look here for cheap gauges for projects.

Since it's impossible to have a pressure difference anywhere from the master cylinder to the wheel cylinders, just plumb in a T fitting upstream of one of the front flex lines with a pressure gauge in the Tee. You'll have plenty of room there.
Jerry

I'm running dual Tilton masters with a balance bar so that's why I need to tap into front/rear separately. I couldn't make that link work Joe, but found surpluscenter then went from there. Thanks.
So Jerry, when you say I would have to drill out the bleeder, I would be drilling straight thru and essentially taking away the tip. The side hole is about 5/64. I assume that is the drill what I would use to leave enough sealing surface. Sound right?

Dennis

Any size drill will work, so use whatever is convenient. The size of the hole will control the rate of flow, not the pressure. It will be a lot simpler to use a Tee upstream of the flex line fitting rather than mess around with the bleeder screw. You'll get exactly the same pressure either place.

Once the brake components stop moving as the wheel cylinders and calipers get the friction material into contact with the drums and rotors, the pressure is going to equalize, so you'll need to be very quick on the trigger looking at the pressure differential.
Jerry

Until somebody gets around to repealing Pascal's Law, the idea that there can be different pressures anywhere in a brake system is ludicrous, unless the front and rear brakes have totally different plumbing, and a master cylinder for each end. Putting any sort of connection between both ends will allow the pressures to equalize within a fraction of a second.

https://www.sciencedirect.com/topics/engineering/pascals-law

Different amounts of thrust on the brake components front and rear is possible with the same line pressure, depending on the diameter of the wheel cylinders and/or the diameter of the caliper pistons.
Jerry

With the discussions here, I've got my plan of attack. I do have completely separate front/rear systems with dual Tilton masters and a balance bar. I can tap right off the bleeder for each of the Tilton masters.
Thanks everyone for showing me the way.

Dennis