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donf888

BluDot adjust brake pressure & maintenance

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Scrap, Mine is in the supply line to tank. And, yes, if I have low air they lock down. Recently happened when quick release valve blew out. Have not had mine long enough to judge pad life but they work great. More truck brake I give, the more Teton brakes apply. It rolls easy. Do not believe they are dragging any at all. I originally plumped mine to output to valve. Changed it though. Did not tow this way. I was thinking like you were. It seems it should go there. Like I said, it works great.

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Sorry, I forgot that you guys don't use Relay Emergency Valves.  You use emergency control valves, which I think just actuate from tractor supply knob and not directly from low air, which ultimately gives you a lot more leeway than I was originally thinking.  When you had low air did they lock down before red knob popped out?  Or when the red knob popped out?

So I guess being valved that way you don't really have a holdoff pressure, but still limiting the whole tank to 70 doesn't seem right.  You lose out on a whole lot of applications that way and are really relying on truck air flow to get back there.  Seems you would keep the tank at system pressure and then put the RV-1 in the control line of the relay valve (or delivery port of emergency control valve - same thing) and do your limiting there.  You have full system pressure of storage but there is no way that it can apply more than 70 lbs to the chamber.

I was also wrong on ratio REV's earlier - I forgot trailer ratio valves ratio UP so you don't want to do that.  Makes things worse!  So put your LQ-4 in the control side of the relay and limit applications there.  So you end up ratio-ing the trailer lower until 50-60, then it blends back to tractor application pressure, then RV-1 caps it at 80 (or 70 if readjusted per this thread).  

I also remembered that Sealco makes a 0 PSI crack "signal booster" valve that looks exactly like their relay valve.  Maybe that was the trouble with the trailer that needed a crack pressure?  Wrong valve was shipped?  A zero crack relay would make for a pretty hyper trailer!

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Wheels on Teton locked, Red knob popped. Then busser low air sounded. It all happened rather quick but it was in that order. This was a 40ish mph. Glad not highway speed. I was on off ramp doing a turn around for potty break

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Yea I'm thinkin that is pretty much how it is gonna be with that valving.  Emergency braking is gonna be on/off only and depend on the truck red knob and not do it on their own.  'Course maybe everybody already knew that and I just figured it out, ha.

I still think the limiters need to be in the control lines, but that is contrary to a lot of installs.  Anybody know why the whole tank is limited?  Something not working right when plumbed in the control lines?

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As I mentioned earlier, my limiting valve is the RV-1 --- and it is set to 80 psi.  My concern parallels Dick T's experience, where there seems to be premature wear on the disc pads.  I didn't know about the LQ-4 valve having a hold-off feature where it would only respond when tractor braking pressure exceeds 4 psi.  The RV-1 applies the brakes in-sync with the brake pedal,,,, which has a definite and most-reassuring feel as all 14 wheels apply braking pressure at the same time and the same force.

BUT methinks there may be some degree of constant pressure (in the under 4 psi range) that is causing the brake pads to have continuous, small-psi contact leading to the pads needing to be replaced every 10-15k miles (regardless of brake usage).

AND, NOW, Scrap has me thinking maybe we need to consider placing the RV-1 on the control line (not the supply-to-the-tank)... to ensure capping the braking force. Hmmm?

-Don

Edited by donf888

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The relay valve installed already has a 4.5psi crack (check its part #) so there will be no change in that regard.  LQ-4 will change the brake bias though.

Maybe ditch the RV-1 and put a 1000 psi proportioning valve on the hydraulic side?

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26 minutes ago, Scrap said:

Maybe ditch the RV-1 and put a 1000 psi proportioning valve on the hydraulic side?

That is probably the best solution in the long run.  The goal is to get the pressure at the calipers down to "reasonable" levels. Without side effects. A properly proportioned master cylinder is the correct way to solve this, but not possible. So a proportioning valve on the hydraulic line would probably be the best second way to solve it.  Not sure how much trouble that will be, though.

I ran my Royals International at least 50K miles with one set of brakes and NO air reduction valves on it. Did not blow out the seals. But I was pretty religious about not leaving it parked with air pressure on it. IMO this is where you risk the blowout the most. As far as I know, John has not had any issues either. 

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Jack -- Thanks for that info; it's encouraging to learn that a set of pads should last ~50k miles.  For me, the concern wasn't the potential for blow-out (of the calipers), it's with the short life span of the brake pads I've seen... around 10-15k miles uses over half of the pad's thickness.  I've now(?) learned (from Glenn) that there is likely a 4psi application pressure with zero braking pressure -- which might be the source of the reduced life span... just trying to find a solution that will help increase the life expectancy to (at least) the 30-40k miles range.

FYI, we are, generally, religious about bleeding down the tank when parked... occasionally, may have parked one night without bleeding (but rarely).

-Don

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I know this from my dirt track days. We would install a single stage master cylinder, which cane from an older truck. Now this was in the eighties. They contained a check valve of sorts. They held pressure against drum brakes. Preload springs so not long brake pedal. This played havoc on our 4 wheel disc brake system. Burn it up in one race. Disassembled it and removed valve, basically a Reed. Worked great afterwards. Don't need any pressure on disc when not braking. 

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