Ron Pope Motorsports                California Custom Roadsters               

proportioning valve

Some one will have to explain to this OLD Man where the air is going to come from to let the fluid drain back to the MC.......I'm sorry but if you have the brakes bled right there is no air to displace fluid......most of your MCs are on the same plane as you wheel cylinders anyway.....if you are getting air in the system you will have a leak somewhere.........I'm done........
 
This isn't an arguement or competition, just talking about the theory and it has nothing to do with air in the system. If the mc is below the caliper, gravity will allow the fluid to return to the lowest point and it retracts the caliper piston away from the pad and rotor, no air. That's the theory, I sure there are variances, but if the mc is mounted under the floor, depending on the rake of the chassis, the calipers are normally mounted to the spindle in front or back, and are usually higher than the frame. I totally understand your point about it being a sealed system and don't disagree, just explaining it as I understand it. From my perspective, the valves are relatively inexpensive, I'm going the safe route and using them. I have enough things to deal with, I don't have time to mess around with the brakes after I think they are done.
 
Lincolnu T, There is no air "getting in the system" but the calibers and/or slave cylinders are retracting thus making the pedal spongy. Just like when you compress the calibers to replace the pads, you have to pump the brakes to bring the pads back in contact with the rotors, definitely not to this extent, but the same thing, no air in the line. Some M/C's have built in res. valve so in theory they "don't" need them.
 
How many of you guys are running power brakes?
I have them on the first T-bucket I built and don't find them to be necessary. I didn't use them on the next two and they stop fine.
 
I don't use the RPV's, just the adjustable prop valve. Built the brake system without it, and found in a panic stop, the rear drums wanted to lock up, and the rear end come around . . . not good! So now I have a little purple prop valve on the rear brake line. No rear lock up. Much better!:)
 
In planning out my brake system, I found that the proportion valve for the rear brakes might be a waste. In my experience with my last T, the rear brakes never seemed to lock up. And on a T with disc brakes up front and drums on the rear, the front brakes are what actually stopped the car. Maybe too much. That may explain why Spirit installs one in the front line. This time around, I may not install one. Of course, another thought is, considering the low cost, why not? That's also my thoughts on residual valves. Low cost insurance. And as Fletch stated, when I'm done with the brakes, I want to be done.

Also, in reading the responses, it's as if each installation yielded various results. Some needed PV's and RPV's and some didn't and every combination in between. Logically, if you have it in and don't need it, no worries. Unless they leak. Remember, in a brake system, the fewer the connections, the fewer chances for leaks. But if everything is installed without and you feel you need them, there you are taking your system apart. Hmmm..... much to consider, as I move forward with my car.
 
In planning out my brake system, I found that the proportion valve for the rear brakes might be a waste. In my experience with my last T, the rear brakes never seemed to lock up. And on a T with disc brakes up front and drums on the rear, the front brakes are what actually stopped the car. Maybe too much. That may explain why Spirit installs one in the front line. This time around, I may not install one. Of course, another thought is, considering the low cost, why not? That's also my thoughts on residual valves. Low cost insurance. And as Fletch stated, when I'm done with the brakes, I want to be done.

Also, in reading the responses, it's as if each installation yielded various results. Some needed PV's and RPV's and some didn't and every combination in between. Logically, if you have it in and don't need it, no worries. Unless they leak. Remember, in a brake system, the fewer the connections, the fewer chances for leaks. But if everything is installed without and you feel you need them, there you are taking your system apart. Hmmm..... much to consider, as I move forward with my car.

I like the way you think things through, Fred. In so doing, you'll have a well built car that you'll enjoy for years.

Jim
 
One other consideration: you're not likely to change anything on the brake system once installed, other than pads/shoes, etc. But, wheels and tires when changed can make a big difference in how your bucket stops. I vote for an RPV in the system somewhere so you can have some adjustability if rolling stock changes are made. I'm just sayin' . . . :)
 
One other consideration: you're not likely to change anything on the brake system once installed, other than pads/shoes, etc. But, wheels and tires when changed can make a big difference in how your bucket stops. I vote for an RPV in the system somewhere so you can have some adjustability if rolling stock changes are made. I'm just sayin' . . . :)

What type of brake system did you have, that the rear brakes wanted to lock up? Disc/disc or disc/drum? Also, where was your PV set at? All the way open, mid way or closed? My rear end never locked up on my old T, so with what I understand about PV's, it would be set all the way open on my present car. Which is what the system would be like without one.:confused:

The more I look into this, it seems that a PV to control pressure to DRUM brakes on a disc/drum T Bucket is useless. HOWEVER, a PV to control the front disc seems a better application. Never the less, I'll probably install one just in case. As stated before, when I'm done with the brakes, that's gonna be the end of it.
 
I like the way you think things through, Fred. In so doing, you'll have a well built car that you'll enjoy for years.

Jim

Thanks, Jim. That's the plan because this will probably be the last one. And being possibly the last one, I find myself building it for the future. I'm not getting any younger and soon, the journey won't be as much fun as the destination. So things like seating, having a door and using systems with minimal maintenance are getting a lot of attention.
 
I have a Camaro rear axle with drum brakes, and Chevy spindles in the front with Speedway "metric" caliper disc brakes. Rear wheels are 15" x 10" wide with 305/50-15 BFG Euro TA's; fronts are 14" x 6" wide with 185/60-14's. For whatever reason, my rears locked up in a panic stop, esp. the right rear. Installing the APV in the rear brake system and adjusting it about half way solved my problem.
 
I have S10 rear drums and mid size calipers up front with the big diameter mid size chev rotors. The cars brakes are a bit front biased.
I found my T wanting to lock up and slide the front wheels on gravel or grass, so potentially it would do the same thing on a wet street if I ever got caught in a downpour.
Like Spirit, I added a front PV which I adjusted 1 full turn in from wide open. (No idea where Spirit sets theirs.)
Car stopped great after that with no front wheel sliding.

Heres the interesting thing though.

That winter I replaced the front pads as they would squeek sometimes during a slow stop.

After that the brakes took a lot more pedal pressure to stop, so I opened the PV all the way and the car stops better...but still not as nice as the old pads WITH some brake force dialed out!
Gonna try a different set of pads next summer as these new ones are not gripping nearly as well as the old.

Lesson here obviously being that pad composition itself plays a big part in brake "feel' and performance.
This alone could help explain why one car might need a PV while a very similar car works fine without one.

There are so many variables in how these cars can be built that having the available adjustability of the PV cannot be a bad thing.

Now you just gotta decide which end of the car you need it on!!! LoL
 
Pads do make a difference. I really notice the difference when stopping from high speed or when loaded pulling a trailer or such when heat and fade play a roll. (In other vehicles) I am hoping that the 11" drums on the rear of my bucket will do much of the work because I'm skeptical of the amount of braking I will get from the front discs due to the skinny front tires. That's why I plan on as much built in adjustability as possible. My thought is it's easier to install during the build than after, and if a variable such as tire size, compound, or brake pad composition changes, I can compensate. Just a theory. I know that I have built very fast cars in the past and scared myself trying to stop them due to under thinking the braking system. I want to be as safe as possible so I don't ruin the fun and work invested in this thing.
 
I have S10 rear drums and mid size calipers up front with the big diameter mid size chev rotors. The cars brakes are a bit front biased.
I found my T wanting to lock up and slide the front wheels on gravel or grass, so potentially it would do the same thing on a wet street if I ever got caught in a downpour.
Like Spirit, I added a front PV which I adjusted 1 full turn in from wide open. (No idea where Spirit sets theirs.)
Car stopped great after that with no front wheel sliding.

Heres the interesting thing though.

That winter I replaced the front pads as they would squeek sometimes during a slow stop.

After that the brakes took a lot more pedal pressure to stop, so I opened the PV all the way and the car stops better...but still not as nice as the old pads WITH some brake force dialed out!
Gonna try a different set of pads next summer as these new ones are not gripping nearly as well as the old.

Lesson here obviously being that pad composition itself plays a big part in brake "feel' and performance.
This alone could help explain why one car might need a PV while a very similar car works fine without one.

There are so many variables in how these cars can be built that having the available adjustability of the PV cannot be a bad thing.

Now you just gotta decide which end of the car you need it on!!! LoL

Hacker, I think what I'm going to do is install RPV's and a PV and be done with it. If I need them, they'll already be in. If I don't, they won't hurt anything by being there. Peace of mind and supporting my hatred doing brake stuff would be worth the small cost and time. Thanks guys.
 
Some people swear by them while others swear at them.
RPV's and PV's don't seem to have much middle ground.
All I can say is, my car was messed with and tweeked, bled in multiple fashions and the brakes never worked without two pumps.
My buddy was used to it and it made no difference to how he drove the car. I couldn't stand it.

When I bought it I decided to try RPV's right away.
There was no sense in running another gallon of fluid thru it to get the "air" bled out...because that hadn't worked multiple times before.

Installed them...did the shadetree pump it up and crack the bleeders thing a couple of times.
Excellent pedal that has never been low since.

But the funny thing is...your car might have an absolutely perfect brake without them. Many do!
Hope it all works out for you first try!
 
Don't know if anybody has brought it up but if you have through the frame fittings it is very hard to get all the air out of them. The hole in the middle is larger than the outlet and causes an air pocket. Somebody makes one that doesn't but I can't remember who.
 
If you attach a clear vinyl hose to the bleeder and submerge it in fluid in a container, then simply pump fluid through the system untill there are no bubbles seen in the hose, it's bled. No need for a helper, or pump and hold, or any mess. I do it by myself always with no issues. The only exception that I've had is with hydro vac or anti lock systems. For those, I use a garden sprayer type power bleeder. Oh, remove, clean, and install thread sealant to the bleeders first, and bleed all wheels from farthest from to closest to the MC, and be sure that the wheel cylinders or calipers are full of fluid and fully expanded firmly against the pads first, so no air is in front of the bleeder and the piston isn't moving allowing trapped air. If you have a spongy pedal, it may be from the caliper backing off and allowing extensive travel, not air. And about the braided lines, if you think about it, a longer line will allow the line to flex long ways more than to expand. That could be a factor to consider when designing our brake systems.
 
I
If you attach a clear vinyl hose to the bleeder and submerge it in fluid in a container, then simply pump fluid through the system untill there are no bubbles seen in the hose, it's bled. No need for a helper, or pump and hold, or any mess. I do it by myself always with no issues. The only exception that I've had is with hydro vac or anti lock systems. For those, I use a garden sprayer type power bleeder. Oh, remove, clean, and install thread sealant to the bleeders first, and bleed all wheels from farthest from to closest to the MC, and be sure that the wheel cylinders or calipers are full of fluid and fully expanded firmly against the pads first, so no air is in front of the bleeder and the piston isn't moving allowing trapped air. If you have a spongy pedal, it may be from the caliper backing off and allowing extensive travel, not air. And about the braided lines, if you think about it, a longer line will allow the line to flex long ways more than to expand. That could be a factor to consider when designing our brake systems.

I'm going to use "Speed Bleeders'. Never let me down.

Domestic Cars Application Guide - Speed Bleeders - Russell Performance Products
 

     Ron Pope Motorsports                Advertise with Us!     
Back
Top