Brake Master Cylinders Front vs. Rear

[Redwein]

With the Wilwood brakes and pedal box, it looks like the rear master cylinder (.75) goes on the middle mount of the pedal box and the rear (.625) goes to the right of that. We're just noticing that this means when you apply the pedal the rear brakes get applied first, followed by the front as more pedal pressure is applied. Is that correct? There was no good picture or conclusive instruction in the manual and we want to make sure we get it right.

Thanks,
Tom

[erlihemi]

You need both the FFR manual and the Wilwood instruction sheet to adjust the threaded bar that bias front and rear brakes.
If the sheet wasn't in the box go to the wildwood site and download the PDFs.

[skullandbones]

Hi Tom,

This is something I learned the hard way. I had a Wilwood pedal set that had two 3/4 inch MCs. I was biasing the front MC so it was being given more pedal pressure by using the bias bar between the two MCs. What happened was my rear MC failed eventually. I used this opportunity to change to the 7/8 MC for the rear. Before I put it back on the road, I called Wilwood tech support. Now this was the surprise I got. The tech said to balance the balance bar so there was almost no bias. He actually suggested that it should be set up this way normally. From everything I had read about it, I was sure you could use the balance bar with as much bias as you needed for my application until talking with him. I wish I could have verified that (maybe in writing) because I know I'm not making it up or mistaking what I read or anything like that. He said it. So I did as instructed and am now using the proportioning valve which is on the rear line. It does not require a lot of turns but it has done the trick. I know Wilwood sells a bias bar adjuster that you can even run back to your dash for real time control so it seemed completely weird to me that the tech would suggest basically not using it. I do have a slight bias on mine which favors the front MC but it is no where close to what I had before on the original set up. I haven't taken the original 3/4 MC apart yet (the one that failed). I bought a rebuild kit for it as a back up for the front. I'm not sure if the MC failed on it's own or if it was due to banging on the system when I went to the track but it does at least suggest that the out of alignment position of the push rod on the MC could have caused the problem. However, one thing for sure is the 7/8 MC that I installed is consistent with the changes FFR made with their kits and so far seems to modulate the balance and adjustment of my system better so that very little adjustment is necessary to get desired results now.

BTW: One thing in the Wilwood instructions that in hind sight makes sense is they suggest the clearance of the balance bar is critical which got me to thinking. When I had a lot of bias, I couldn't get that clearance to meet the standard but when I "balanced" it better, the clearances also worked better.

Good luck,

WEK.

[Arrowhead]

With that setup (assuming you have the standard FFR supplied front calipers and stock Mustang rears calipers) you should be able to adjust the balance bar to center so they both are applied equally The rear calipers have a smaller piston surface area than the front, so by staggering the master cylinder size (3/4" front, 5/8" rear) it more closely matches the stroke required for the front and rear. Ideally you can fine tune the bias bar after it's on the road. Also, it doesn't matter which is on the left or right for purposes of balancing, just brake line routing. The balance bar is fully adjustable to give significant bias to either cylinder.

[Arrowhead]

Hi Tom,

This is something I learned the hard way. I had a Wilwood pedal set that had two 3/4 inch MCs. I was biasing the front MC so it was being given more pedal pressure by using the bias bar between the two MCs. What happened was my rear MC failed eventually. I used this opportunity to change to the 7/8 MC for the rear. Before I put it back on the road, I called Wilwood tech support. Now this was the surprise I got. The tech said to balance the balance bar so there was almost no bias. He actually suggested that it should be set up this way normally. From everything I had read about it, I was sure you could use the balance bar with as much bias as you needed for my application until talking with him. I wish I could have verified that (maybe in writing) because I know I'm not making it up or mistaking what I read or anything like that. He said it. So I did as instructed and am now using the proportioning valve which is on the rear line. It does not require a lot of turns but it has done the trick. I know Wilwood sells a bias bar adjuster that you can even run back to your dash for real time control so it seemed completely weird to me that the tech would suggest basically not using it. I do have a slight bias on mine which favors the front MC but it is no where close to what I had before on the original set up. I haven't taken the original 3/4 MC apart yet (the one that failed). I bought a rebuild kit for it as a back up for the front. I'm not sure if the MC failed on it's own or if it was due to banging on the system when I went to the track but it does at least suggest that the out of alignment position of the push rod on the MC could have caused the problem. However, one thing for sure is the 7/8 MC that I installed is consistent with the changes FFR made with their kits and so far seems to modulate the balance and adjustment of my system better so that very little adjustment is necessary to get desired results now.

That may have worked in your case. I'm pretty sure FFR has switched to shipping a 5/8" for the rear on newer kits, the 3/4" was too big for stock rear Mustang calipers. I didn't know you could get a 7/8" master for the Wilwood pedal box - it's not listed anyway.

http://www.wilwood.com/MasterCylinders/MasterCylinderList.aspx?group=Compact%20Remote%20R eservoir%20Master%20Cylinder

[myjones]

That may have worked in your case. I'm pretty sure FFR has switched to shipping a 5/8" for the rear on newer kits, the 3/4" was too big for stock rear Mustang calipers. I didn't know you could get a 7/8" master for the Wilwood pedal box - it's not listed anyway. http://www.wilwood.com/MasterCylinders/MasterCylinderList.aspx?group=Compact%20Remote%20R eservoir%20Master%20Cylinder

I have the 5/8 with my kit #431 so it saved me making the change after the purchase. The O.P used the term applied the front first but it's really more about length of stroke for each cylinder than timing.
I'm almost done changing mine up to 13" rotors all around but since the calipers are the same I should still have the right combo on the fluid side of it.
DB Hemi33

[kraftee]

Interesting that your car (#431) has the 5/8" MC while mine (#538) came with two 3/4" MCs. Made no difference to me as I went with a vacuum-boosted power brake system. However, I did use one of the kit Wilwood masters for my hydraulic clutch setup. Learned the hard way that 3/4" wasn't big enough to generate enough fluid movement to completely disengage the clutch.

ERIC

[CHOTIS BILL]

That may have worked in your case. I'm pretty sure FFR has switched to shipping a 5/8" for the rear on newer kits, the 3/4" was too big for stock rear Mustang calipers. I didn't know you could get a 7/8" master for the Wilwood pedal box - it's not listed anyway.

http://www.wilwood.com/MasterCylinders/MasterCylinderList.aspx?group=Compact%20Remote%20R eservoir%20Master%20Cylinder


You can get master Wilwood master cylinders from 5/8 to 1-1/8

5/8” Combination Master Cylinder Kit (1.2 stroke) 260-3372 Rebuild Kit, 5/8” Combination 260-3880
3/4” Combination Master Cylinder Kit (1.2 stroke) 260-3374 Rebuild Kit, 3/4” Combination 260-3881
13/16” Combination Master Cylinder Kit (1.2 stroke) 260-5920 Rebuild Kit, 13/16” Combination 260-5921
7/8” Combination Master Cylinder Kit (1.2 stroke) 260-3376 Rebuild Kit, 7/8” Combination 260-3882
1” Combination Master Cylinder Kit (1.2 stroke) 260-3378 Rebuild Kit, 1” Combination 260-3883
1-1/8” Combination Master Cylinder Kit (1.2 stroke) 260-3380 Rebuild Kit, 1-1/8” Combination 260-3884

Bill Lomenick

[myjones]

Interesting that your car (#431) has the 5/8" MC while mine (#538) came with two 3/4" MCs. Made no difference to me as I went with a vacuum-boosted power brake system. However, I did use one of the kit Wilwood masters for my hydraulic clutch setup. Learned the hard way that 3/4" wasn't big enough to generate enough fluid movement to completely disengage the clutch.
ERIC

Eric
I double checked the MC's yesterday and I do still have both 3/4 units. I have known for awhile it needs to be 5/8 on the back to balance but I still need to buy that part, Oldtimers brain fart I guess sorry for the confusion. DB

[Redwein]

Thanks for all the helpful replies. We now have the .75 on the RHS for the front and the .625 on the left for the rear and adjusted the balance bar so everything appears straight and being applied equally.