68 camaro proportioning valve (combination valve)HELP?

[72Z/28]

Originally Posted by GregWeld

Now -- here's the problem with buying a "one size fits all" proportioning valve...


Those valves are usually specific for a car - as it left the factory. Well ---- as it left the factory it had bias ply skinny tires.... Now days we have staggered tire sizes... with big fat ones out back and fat nice ones in front...and or we also have different rotors and calipers on than came from the factory.... so now the brake bias is all wrong for what we currently have on the car.

Thus -- most people around here (performance enthusiasts for lack of a better term) will put on an ADJUSTABLE PROPORTIONING VALVE -- which, obviously, can be adjusted so that the bias will be proper for the car it's installed in.

The last thing you want to have happen is for you to need to panic stop, god forbid it's wet out -- and you lock up your rear brakes and have the ass end swap with you. Thus the need for the proper ratio of front braking power to rear braking power AKA a brake proportioning valve.

Wilwood will be happy to sell one to you -- along with a mount (if you want to use theirs) and instructions... The proportioning valve ONLY goes to the rear brakes since they're the ones we're trying to tune to get them to match what we have up front - whatever those are and the grip we have there.




http://www.wilwood.com/TechTip/TechFaqs.aspx

Thanks Greg for the write up. Actually the Wilwood MC was installed by the previous owner and I don't have the bleeding kit. I guess I am going to order the plugs to bleed the MC on the car.

As for the new stock proportioning valve, does that mean that it will not work properly with the wilwood MC and calipers? I wonder if wilwood sells a valve that does not require any adjustments because the car will not be used for autocrossing or at a track.

One more point, I recently replaced the rear brake line from right stuff detailing. It is a 1/4" line, which is basically a stock replacement. However, wilwood recommends a 3/16" line.

[GregWeld]

Originally Posted by 72Z/28

Thanks Greg for the write up. Actually the Wilwood MC was installed by the previous owner and I don't have the bleeding kit. I guess I am going to order the plugs to bleed the MC on the car.

As for the new stock proportioning valve, does that mean that it will not work properly with the wilwood MC and calipers? I wonder if wilwood sells a valve that does not require any adjustments because the car will not be used for autocrossing or at a track.

One more point, I recently replaced the rear brake line from right stuff detailing. It is a 1/4" line, which is basically a stock replacement. However, wilwood recommends a 3/16" line.

You might have misunderstood why I posted what I did.... In a nutshell -- the stock type prop valves are designed to work with pretty much stock tire and brake sizes... I didn't say it wouldn't work with the master cylinder... I was giving you some information you could use so that you might question the use of a stock prop valve over a adjustable prop valve if you're NOT running stock or nearly stock tires etc. This is a safety issue.... you're brakes and understanding them should be your most important concern. Spinning at freeway speeds is nobodies idea of a good time. The brake bias of your system is critical to work properly when you'll need it the most... a panic stop.

[72Z/28]

Originally Posted by GregWeld

You might have misunderstood why I posted what I did.... In a nutshell -- the stock type prop valves are designed to work with pretty much stock tire and brake sizes... I didn't say it wouldn't work with the master cylinder... I was giving you some information you could use so that you might question the use of a stock prop valve over a adjustable prop valve if you're NOT running stock or nearly stock tires etc. This is a safety issue.... you're brakes and understanding them should be your most important concern. Spinning at freeway speeds is nobodies idea of a good time. The brake bias of your system is critical to work properly when you'll need it the most... a panic stop.

You are absolutely right and I am not disagreeing with you Greg. As you said, the tires,wheels, and the brakes are all modified;therefore, the stock valve might not fit this application.

I started looking at the wilwood valve but the I have to order different size MC fittings to install the valve. Unfortunatelly the fittings are in back order and need to wait for two more weeks to get them.

As for the front to rear brake line, i am running stock 1/4 in brake line, which I installed recently but wilwood recommends 3/16 line instead. I am not sure if there is a prebent line in the market

[GregWeld]

Originally Posted by 72Z/28

As for the front to rear brake line, i am running stock 1/4 in brake line, which I installed recently but wilwood recommends 3/16 line instead. I am not sure if there is a prebent line in the market

Most tube today is 3/16” or ¼”. 3/16” is stiffer, lighter, and easier to bend. It and its associated fittings are also the most common. ¼” has less internal friction (less resistant to fluid flow) and is easier to handle without damaging. Note that ¼” DOES NOT “provide more volume” to actuate the callipers more quickly as I have read more times than I care to remember. The MC piston’s bore and stroke determines the fluid volume displaced and therefore the pedal stroke required to apply the brakes. The tubing is sealed and full – its diameter has nothing to do with it (within reason) and you certainly won’t notice the difference between ¼” and 3/16” – except maybe the placebo effect cuz your buddy said so! I personally like to use 3/16”.

[Sieg]

Chassis line from master to drop down is 1/4" and 3/16" line from the drop down to calipers is OEM spec?

[GregWeld]

Originally Posted by Sieg

Chassis line from master to drop down is 1/4" and 3/16" line from the drop down to calipers is OEM spec?

Some OEM ABS systems combine the use of 1/4 and 3/16" in the same system. I researched this question for a couple hours and could find nothing definitive to explain the "recommendation" of 3/16" over 1/4" in this closed system. The volume difference - even if you calc'd all the line length and diameters is negligible and the PRESSURES would be the same in both line sizes.

[Vince@Meanstreets]

Originally Posted by GregWeld

Some OEM ABS systems combine the use of 1/4 and 3/16" in the same system. I researched this question for a couple hours and could find nothing definitive to explain the "recommendation" of 3/16" over 1/4" in this closed system. The volume difference - even if you calc'd all the line length and diameters is negligible and the PRESSURES would be the same in both line sizes.

3/16" tubing is lighter due to material and fluid capacity and easier to package and and form. lighter = faster