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One of the fellows here in Medford has an 1800 Eurotrike with a real weird rear brake problem. After a few minutes of riding the rear brake pedal goes almost all the way down as though there's air in the system. A second stroke on the pedal brings it back up to normal operation. The Eurotrike people came to Medford and spent a couple days on it with no success. The system has been bled many times both manually, with pressure and vacuum bleeders with no success. The master cylinder was changed with a brand new Honda OEM master with no success. The brakes show no sign of heating, the calipers are cool to the touch when acting up. The brake system is not quite the same as a standard 1800, the front fork master cylinder has been removed and of there are two rear calipers instead of one. The Honda front calipers are mounted on the trike raked front fork assembly. In an effort to solve the problem the front and rear brake linkage was eliminated and the same result obtained. This one is a real poser and if anyone has an idea we'd appreciate suggestions. I 'm about tapped out as are several others around here.
 

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is this a new problem or did they ever work ? Are the calipers mounted higher than the master cylinder?JB
 

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This is a problem that started with the triking of the bike. All the calipers are mounted higher than the master cylinder but not by much.
 

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Off the top of my head im going to say you mighthave to look into puttinga 2 psi residual valve. inline .You normally dont need them with disc brakes as most the time the the calipers are lower than the master and stay full. There is a chance that fluid is flowing back into the reservoir by means of gravity requiring to pump them up. .. JB
 

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Sounds like a good possibility to me. I've passed your suggestion on to Bud. It makes sense too because his rear calipers are at the top of the disks and there are two of them which may make it more likely the fluid could pull back toward the master cylinder. Thanks for the suggestion, I hadn't considered that.
 

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JBz wrote:
Off the top of my head im going to say you might have to look into putting a 2 psi residual valve. inline . You normally dont need them with disc brakes as most the time the the calipers are lower than the master and stay full. There is  a chance that fluid is flowing back into the reservoir by means of gravity requiring to pump them up.  .  . JB
A bleed down test would confirm this theory. Hold the rear brake down for a few minutes. If you dont get brake fade, The system is intact!
 

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There's no doubt the system is intact, the pedal ends up hard when pressed and held. The only thing is that sometimes it goes down 1/2" and firms up and the next time it may go down 1 1/2" to firm up. I like JBz's suggestion and have already relayed it to Bud along with some websites with information about residual valves. It makes sense to me. As the trike goes down the road the slight shifts of the caliper and rotor can wiggle the pistons back into the caliper body. Then the next time you need the brakes it's going to require more fluid to get them back against the disk so it requires a second press of the pedal to pump the extra fluid into the system. I can see where a residual valve would help prevent the fluid from being pushed back into the master cylinder via gravity from the high mounted calipers and the vibration and motion of the caliper vs the brake rotor. I've got great hopes that this is the answer. We'll know soon, Bud is going to get a 2psi valve and try it ASAP.
 

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Just found this thread. The master cyl. reservoir is about 5-6 inches above calipers. I'm beginning to wonder if, when going hot into curves, if something is flexing enough to shove some pistons, maybe even the axles themselves are bending slightly. Stranger things have happened. It wouldn't take much deviation with the amount of displacement involved, vs: the displacement of master. I'm beginning to think floating calipers are the real deal.

John, here's the oem brake set-up without the ABS.
 

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The only shot I could find of Bud and Trike

Added : For further info, Google "Eurotrike" or "EML trike"
 

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If they are they trying to feed 2 calipers with a master cylinder that is intended for only one.<double the Volume or dispacement wise> I would think A residual valve might only be a bandaid as the master might not really have enough volume per stroke of the pedal. :?JB
 

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Hi John.
The brakes work fine, if on a very smooth surface, and when first getting underway. When sitting overnight, there's only 1/4" pedal movement, and it is very hard. Probably due to better, stiffer hoses. They're the Stainless braided teflon variety.

The problem almost seems to be deflections in the suspension, causing the discs to deviate from their original path, consequently pushing the pistons in, thus requiring a pump-up of master cyl. Once pumped back up, they work perfectly, until a few more bounces down the road.

Anyway, scrutinizing the suspension, and the engineering of the caliper mounts will be the avenue we're going to pursue Monday. I personally think he would be better off with floating calipers. Will let you know what we find out.

BTW, the caliper relationship to the master cylinder is actually better than the oem set-up. The disc calipers are a little lower than original caliper.
 

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Kudos to JBz!:clapper::clapper::clapper:It looks like a 2psi residual valve is solving a problem that's plagued Bud's trike for over a year. Even the factory people couldn't get the rear brake system working on his trike. Why only his trike no one knows but a test ride today showed the rear brakes working as they should. Thanks again for the suggestion.
 

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Its good to hear its working Paul. Its actually kudos to Fred Puhn author of the Brake Handbook . Iveused his ideas and formulas on some custom projects over the years. JB
 

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Good job guys! That's what this forum is all about!!! ;)
 

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Indeed, the forum is one of the first places I turn to with a mechanical problem and many other types. There is a huge knowledge base on many subjects here.
 
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