Inverted brake reservoir

[Tony Spicer]

Yep, they're spring loaded to the closed position. Grease, or in your case fluid forces the ball back against the spring and fluid can flow into the reservoir. The problem is when the fluid level drops, air must enter to replace the missing fluid. If that doesn't happen, a vacuum is formed in the reservoir. The fluid flows to the brake cylinder via gravity. What you have is the same as dipping a straw in water, putting your finger over the end, then removing the straw from the water and watching in amazement as the water stays in the straw. You've just been lucky. Best to replace the zerk with a vent.

Tony

[1001001]

I would think an inverted brake fluid reservoir would be difficult to fill.

[Caveman]

Originally Posted by Tony Spicer

Yep, they're spring loaded to the closed position. Grease, or in your case fluid forces the ball back against the spring and fluid can flow into the reservoir. The problem is when the fluid level drops, air must enter to replace the missing fluid. If that doesn't happen, a vacuum is formed in the reservoir. The fluid flows to the brake cylinder via gravity. What you have is the same as dipping a straw in water, putting your finger over the end, then removing the straw from the water and watching in amazement as the water stays in the straw. You've just been lucky. Best to replace the zerk with a vent.

Tony

Thanks for the explanation. My personal theory is more along the lines that the piston causes pressure to move the puck and gravity isn't too much of a factor. If a vacuum tries to form in the reservoir it overcomes the spring pressure and let's air in. I've never noticed either a pressurized reservoir or a vacuum when removing the zerk to check fluid levels and I don't loose fluid from the cap. I have about 435 hours on the 7 and have replaced pads twice. I have no brake sponginess or other issues. BTW, this wasn't my idea and there are others flying with this set up. It works fine, for me at least. I promise to report back if I develop brake problems. I'm gonna stick with it unless someone using it reports a problem.

[edsong]

I'm with Caveman. Been using this setup on my Pitts for years and my RV-8 for a year now. No leaks. I also use a zerk for the vent on Marv's smoke tank for my 8. Seems to let air in as I use the smoke oil. No issues.