bought a old ford hot rod ! It has some pretty bad work done on it , my question is the car stops good . But it has the large brake reservoir plumed to the rear ? And the small to the front ? Can I leave it that way,????? if not why .
As disc break pads wear down, the level in the reservoir will drop as discs do not fully retract as drums do. There is a possibility of running out of fluid before pads are changed if the smaller reservoir is connected to the discs.
It will work fine as long as you monitor fluid as the brakes wear. The calipers require more fluid as the pads wear. Operation wise, they don’t know the difference Sent from my iPhone using H.A.M.B.
The only problem I see is if you add fluid as the pads wear, when you go to put new pads in you will have to remove fluid or it will come spilling out of the reservoir when you compress the pistons.
Swap the brake line on the master cylinder and just be done with it and have it right. Then you don't have to monitor it, remove fluid etc. when you replace pads. 1 hours worth of work to have it right.
Most dual master cylinders are not 50/50 in fluid displacement output, especially disc/drum, so it's important to plumb them correctly. The larger reservoir should always go to the front brakes on cars and light trucks.
I’m curious about this statement, unless it is a quick take up master, then shouldn’t it be the same? The secondary piston is activated by the primary piston hydraulically and provided they are the same bore size shouldn’t they be the same output? I realize the secondary is ever so slightly slower in applying, I’ve never seen anything pointing towards them being different outputs so am interested in this. Sent from my iPhone using H.A.M.B.
The primary and secondary master cylinder piston strokes match the normally larger front and smaller rear brake caliper and/or wheel cylinder fluid displacement requirements, and is why the OE lines are configured not to be switched at the master cylinder. Some drum/drum and disc/disc master cylinder reservoirs may look identical, and can easily be plumbed incorrectly, while the typical disc/drum (and some drum/drum/disc/drum) masters have an obviously larger fluid reservoir intended for the fronts. Bottom line-if the reservoirs are not obviously different, make sure you know the original design intent before you plumb the brakes.
I’m just trying to wrap my head around this, should the secondary piston not move exactly the same distance as the primary given the same bore size? Also given that there is very little “flow” I can’t see how it would be different between primary and secondary circuits. Again other than gm’s quick take up master. Sent from my iPhone using H.A.M.B.
There are springs and sometimes valving that allow one piston to move before the other. Once the fluid pressure starts to build, the second piston moves.
He nailed it there. Also you for sure don't want the rear brakes hooking up before the fronts do or you end up making a nice spin out when you don't want to. Larry K a big empty and slightly wet parking lot where you can run 35 or 40 and nail the brakes and hang on might be your friend here. that will let you know if the rear brakes hook up before the fronts do before you have a situation where it would be a real issue. Normally the larger reservoir is intended for the front brakes on disk brake setups though
A normal master doesn’t have valving in it and the only springs are for piston return, the metering and portioning valves take care of any needs brake bias. The secondary is applied hydraulically by the primary but it can’t move less than the primary, hydraulics don’t work that way Sent from my iPhone using H.A.M.B.
This is how I understand this: When the primary piston is pushed, the piston pushes fluid INTO THE RESERVOAR until the piston seals off the port on the reservoar. This movement does NOT move the secondary piston. When the primary piston has closed its port, it Will move the secondary piston, witch Will also push some fluid into its reservoar. Until now, there has not been built any pressure in any of the brake circuits. Further movement will move fluid to the calippers/cylinder and move pads/bands in contact with discs/drums. Any further movement will now build pressure. If the primary circuit is cut off, the primary piston Will make MECHANICAL contact with secondary piston (see the tap om secondary piston) If the secondary circuit is cut off, the secondary piston will make mechanical contact with the master cylinder and let the primary circuit build pressure. Hope this was understandable and not too many spelling mistakes. I'm Norwegian... Rune Waltoft
I actually have some hands on experience with this. When I built my model A truck, I plumbed the front reservoir to the front brakes, and the rear reservoir to the rear brakes. The brakes were never that good, so I chased all kinds of solutions, to the extent of changing caliper sizes, from metric to big impala calipers. Nothing seemed to make much difference, until my buddy and I were bleeding them one day, and we finally figured out we had the lines mixed up. I changed the lines around, and instantly had great brakes. I could finally lock up the front brakes. Its embarrassing to admit I did it wrong. That was probably the first mistake I've ever made though, and I'm not sure I've ever made a mistake since then.
I agree with the above post and picture, the ports are covered almost instantly, I still don’t see how they move different volumes. As far as I know, the only reason for different sizes is to compensate for brake wear as the calipers keep moving out as the pads wear, wheel cylinders do not Sent from my iPhone using H.A.M.B.
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