i cant find them on my 97 cavalier Z24 . . here is a pic of my cavy and someone elses that has em idk maybe my car didnt come with em
here is the other guys
this boggles my mind......
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- Sold my beloved J in April 2010 -
Why are you worried about it? You don't need them if you swap to rear disc. I realize they came stock on some 3rd gens, but I still can't figure out why. They weren't really needed, since the MC is higher than the wheel cylinders.
I have a 97 Sunfire and it doesn't have them either. I don't know what else to tell you.
my '02 Z has them. they are in the lines, just forward of the rear tire on the driver side.
Desert Tuners
“When you come across a big kettle of crazy, it’s best not to stir it.”
my buddy's 98 zed has 'em, could be a pre 98 thing
1998 Chevrolet Cavalier
5-spd
i've realized that the abs units are diff from 95-99 to 00-02. perhaps they are located somewhere in the abs unit for 95-99?
anyway, i dont think its a thing of he needs them, i think he wants to get rid of them overall for doing the rear conversion (but isn't sure where they are, seeing as j's supposedly have them....)
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- Sold my beloved J in April 2010 -
yeah what viper said . i dont wanna do the swap and find out i have them somewhere and have the brakes drag from having the 10psi ones on lol . but ill go ahead with the swap somtime soon and see what happends
00+ has them, older does not.
Cahill, I believe they use them on the back because if you park on a hill you can easily get your rear cylinders above the MC. Then float the fluid back and overflow the MC reservoir.
James Cahill wrote:Why are you worried about it? You don't need them if you swap to rear disc. I realize they came stock on some 3rd gens, but I still can't figure out why. They weren't really needed, since the MC is higher than the wheel cylinders.
This has nothing to do with the height of the MC. It has to do with the drum brake setup.
Drum brakes use springs to pull the shoes away from the drum. Disc brakes do no such thing. The pads stay in contact with the rotor and simply don't have any pressure applied.
If drum brakes didn't have the springs, then they'd be permanently locked up since they use mechanical force to increase stopping power. They need something to pull them away when the pressure is released.
What a residual valve does in this case is keep a certain amount of pressure in the system to overcome most of the power of those springs. This holds the shoes closer to the drum than they would otherwise be, so they engage right away when you press the brake rather than having to travel the length that the spring would have otherwise pulled them back first.
Without a residual valve, the front brakes would always engage before the rear, which isn't what you want at all.
To set the record straight:
The description of the RPV sent along with the RPV's inside the package from willwood reads and I quote, "A residual pressure valve is used when a master cylinder is mounted equal to or below the horizontal plane of the calipers or drum brake wheel cylinders. This valve prevents fluid flow-back to the master cylinder reservoir which can cause excessive brake travel or "pumping" of the pedal to engage brakes."
See, in hydraulic systems they naturally restore to a state of equal pressure. Yes, drum brakes use springs and use them to push the hydraulic piston back when the pressure on the brake pedal reduces, however you'll notice these systems have a automatic self adjusting system "star bolts" - or whatever you call them. Meaning that as the pads wear, the state of natural pressure is spread outward as the pads wear. This is caused by the "star key bolt adjuadjustablengy" and thus this star bolt is what takes most of the burden of the spring pressure at this natural state, not the RPV's as wild weasel has stated. The RPVs only keep enough pressure on the hydrhydraulicskeep snug against the shoes.This is the only purpose of the mechanical system.
Now, as the pads wear and the mechanics spread out the pads, the hydrhydraulicse out also with the pad wear. Now, this means the hydraulic system has a floating natural pressure state as the pads wear aswelas wellause as the star key thingy spreads the minimum diameter that the pads create) And hydhydraulicsing such wont "suck back" into the wheel cylinder as the residual pressure valve keeps 10psi on the brake line thus keeping the hydraulic cylinder constantly lightly pressed against the pads, wherever the mechanical system choses to place them as the pads wear.
This means the hydraulic system is constantly ready to spread out the drake drums all thanks to the RPV's.
As weasel has said, you dodon'tant the front to engage before the rear. However this is where the inferiority of the drum brakes can be noticed. See in disc there are no springs required to "pull back" the brakes. Rather the pressure equalization is enough to stop the frictional forces required to stop the car and this is also why there is only 2psi RPVs used on Disc brakes as 10psi would cause drag. Disc brakes never pull back only release pressure.
The drum brakes uses MOST of this hydraulic pressure trying to overcome the springs constantly trying to retract them when they are engaged. This therefore reduces the amount of pressure avavailableo be pushed against the drum and therefore make drum brakes suck compared to disc. See in our cars the MC biases Front and Rear and keeps pressure constant (or constant but off by a certain differential if you have a peper-portioningalve, which our cars ddon't between them, meaning the drum brakes will always have less force applied to the friction surface than the disc bbecausealot of it is wasted in the springs - which causes the dive to the front when brakes are engaged.
I hope this helps. RPV's are to only snug up the hydraulics and keep fluid from flowing-back to the MC. Without RPV's "soggy pedal, or pedal pumping could happen"
I hope I havn't left anything out, but its so easy on this type of topic.
Wild Weasel wrote:James Cahill wrote:Why are you worried about it? You don't need them if you swap to rear disc. I realize they came stock on some 3rd gens, but I still can't figure out why. They weren't really needed, since the MC is higher than the wheel cylinders.
This has nothing to do with the height of the MC. It has to do with the drum brake setup.
Drum brakes use springs to pull the shoes away from the drum. Disc brakes do no such thing. The pads stay in contact with the rotor and simply don't have any pressure applied.
If drum brakes didn't have the springs, then they'd be permanently locked up since they use mechanical force to increase stopping power. They need something to pull them away when the pressure is released.
What a residual valve does in this case is keep a certain amount of pressure in the system to overcome most of the power of those springs. This holds the shoes closer to the drum than they would otherwise be, so they engage right away when you press the brake rather than having to travel the length that the spring would have otherwise pulled them back first.
Without a residual valve, the front brakes would always engage before the rear, which isn't what you want at all.
Normally I would never try to argue a point with you, since you're a smart guy, but I have to here.
You're right about the springs pulling the shoes back, but hydraulic pressure doesn't keep them from fully disengaging, its the star wheel adjuster that does. Everytime you apply the brakes, the adjuster is tightened (wether or not it actually rotates is based on shoe/drum wear, and how much shoe to drum clearance there is), so that when you release the brakes, the adjuster keeps the shoes in contact with the drums, not fluid pressure. This is why you have to back the adjuster off when the drum is bellmouthed, because the adjuster is keeping the shoes in contact with the drum.
My 94 never had and type of RPV, not from me, not from the factory, and my rear brakes never engaged before the fronts.
Alot of street rods need to use RPVs, since they mount the MC below the floor so the firewall is cleaner, which also puts it below the calipers and drums. Without an RPV, fluid would flow back to the MC due to gravity, and pressure would hae to be built up again to get the fluid back to the calipers/drums.
josh, nice post, but were u drunk when you posted that lol
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- Sold my beloved J in April 2010 -
i dont quite understand how residual valves became a big concern all of a suddden. people have been going to rear discs for years
