Wilwood / Tilton - dual master - pedal return

[Jean]

Hi,

For those of you who have bled your dual master pedal assembly, how is the brake pedal feeling?

1) is it firm from the get to, or does it have a little bit of softness first before it's firm?

2) does the pedal return back to initial position on it's own?

3) did you have to install a return spring for the pedals to return to top position ?

The reason why I am asking is after I've bled my brakes using motive pressure brake bleeder and got all the air out of the system , my pedal is FIRM but inly after about 3/4" of initial movement. Also, the pedal does NOT return back to the initial position and this is really bugging me.,

Tips, suggestions, comments, are more than welcome :). I'd really like to finish this part of the swap so I can put the interior /dash back in place and move on to the engine swap.

[FredK]

There shouldn't be much mushiness.

I have a Massive dual master setup with two Tilton 74 series MCs, and what I've found is that the best pedal feel you'll get is after you bleed, drive around and activate the ABS a few times, then bleed again. Also, if you have brand new brake pads and rotors, the initial bite will feel terrible until you bed the brakes in.

There should be sufficient spring inside the master cylinder to return the pedal to the original position, but only after you fully bleed and bed the brakes. Otherwise, the air in the system causes the pedal to return very slowly and sometimes incompletely if you have a lot of air still in the system.

I realize you still are in the middle of a swap, so it may be something you have to tackle once you get the car on the road, or push a ton more fluid through and tap all the lines and calipers to get all of the bubbles to bleed out.

[Jean]

Thank you! I'll keep at it, the rotors and pads are old, I think they have 1 season of autocross on them from years back and then car sat.

Since you have the dual master setup, did you pressure bleed it as well? And, did you end up bleeding one caliper at a time as normally done, or TWO calipers at the same time as many guides for dual master configs recommend doing?

[Jean]

Called Summit Racing tech line, was not impressed with their knowledge. Called wilwood shortly after and they actually laughed about summit racing tech line :/

Anyways, long story short I went ahead and purchased 4 new/rebuilt calipers, will be installing them sometime this week and I'll re-bleed the whole thing again and see how it feels.

Per Wilwood they are suggesting that the dual 5/8" is too small for the stock calipers, so I went ahead and measured the piston sizes of the front and rear calipers (I got 45mm front piston diameter and 32mm rear) . Their technician stated that if there is no air left in the system, and the pedal is soft at the initial/starting point and then gets harder then the masters aren't sized correctly.

I will be calling then back tomorrow AM and see what sizing they recommend for these caliper piston sizes.

I know that Garagistic recommends dual 5/8 and that's what I went with, but the initial "dead space" and the fact that the pedal does not return back is less than optimal imho. I've used Motive pressure brake bleeder and the fluid is coming out clean and solid on each corner w/o any bubbles so I am pretty confident there is no air left in the system.

[FredK]

I have dual 5/8th MCs with even larger front and rear calipers (57mm F, 40mm R), and a 6.25:1 pedal ratio. I don't have particularly strong legs and I feel like dual 5/8ths is about what I need for a hydraulic ratio. I think my pedal effort is around 70 lbs or so to get to my maximum deceleration rate. I had a .625 front and .700 rear with 54mm front caliper piston diameter and 38mm rear caliper piston diameter. This was not confidence inspiring.

I pressure bled my system one caliper at a time. My pedal returns to normal. With the balance bar, make sure there's around .20 to .25" of total "play" to ensure it doesn't get bound up at any point, and to ensure there's no additional friction preventing a smooth return of the pedal.

[Jean]

That is promising! Maybe, just maybe it's just my calipers so I'll update this thread by end of the week. Hopefully won't have to pull the damn pedal assembly out again, it's getting to be quite annoying!

[FredK]

I also think there's a little bit of seal drag that loosens up after 50 to 100 miles, and at that point, the pedal shouldn't be sluggish any more. I probably only put around 250 mL of fluid through each master cylinder in total, and things feel fine. There's probably a tiny bit of air still left but I'm not sweating it.

I pressure bleed at around 15 psi.

[Jean]

Update -

Replaced all four calipers today, bled the system again. No air left, clean fluid at all four corners. Pedal still has about 3/4" of slack but there is improvement . Pedal is nice and firm after the initial slack, AND pedal DOES return more now than it did initially. It does not return to the initial position (due to the slack/dead space that I need to get rid of).

So, calipers did improve current situation . But, looks like I'll need to take the pedal box out again and adjust the "height" of the pedal to remove the slack or "dead space".

I called Wilwood and gave them all the info about the components I am using and piston / master sizes but they haven't gotten back to me yet, I'll follow up tomorrow.

I am bleeding using 15psi as well, really like the pressure bleeder!