Jump to content
HybridZ

Question about dual master cylinders...


Recommended Posts

  • Replies 99
  • Created
  • Last Reply

Top Posters In This Topic

On 12/28/2017 at 9:02 PM, NewZed said:
 

Genius! I didn't realize they moved to a paid accounts thing or I would've looked that up, I thought they just updated their settings and users had to click a checkbox or something.

 

On 12/29/2017 at 8:04 AM, JMortensen said:

I don't even remember having a photobucket account. Tried to log in, all I had were the wind tunnel test pics in there. I know I had more pics at one time, this is all I could find. 

dualmaster.jpg

thanks for getting these posted! These are super helpful in planning things out. and also I was mistaken, the posts were from Lunar's buildout, not yours. His posts were The ones not working. Either way, thanks again!

Now that you've had some time (I'm assuming you nstalled this setup and it's on now), how do you like the 3/4 and 7/8 MCs? would you prefer larger or have they been good? and how do you like the overall braking with the dual MCs?

Link to comment
Share on other sites

That's a tricky question, because pedal feel and overall performance have lots of different variables. Rotor size, caliper size, pad size, pedal leverage ratio, etc all affect how much pedal effort you need and how well it will perform. With the pedal ratio modded to close to 5:1 with 12.2" rotors, Superlight 1.75 4 pistons and Dynalite 1 3/8 4 pistons and Hawk Black pads and after messing with the balance bar a bit I think my brakes feel pretty good. In fact, if I stuck someone else in the car and didn't tell them, I doubt they would know that it was a manual setup. That said others running 6:1 ratios seem to like bigger masters, more like 1". 

Link to comment
Share on other sites

On 1/3/2018 at 6:52 AM, JMortensen said:

That's a tricky question, because pedal feel and overall performance have lots of different variables. Rotor size, caliper size, pad size, pedal leverage ratio, etc all affect how much pedal effort you need and how well it will perform. With the pedal ratio modded to close to 5:1 with 12.2" rotors, Superlight 1.75 4 pistons and Dynalite 1 3/8 4 pistons and Hawk Black pads and after messing with the balance bar a bit I think my brakes feel pretty good. In fact, if I stuck someone else in the car and didn't tell them, I doubt they would know that it was a manual setup. That said others running 6:1 ratios seem to like bigger masters, more like 1". 

Yeah I know those are all important factors, but I'm in the same boat as you were when this thread was started where I can spend the amount to fix my system or just do the upgrades I want to do in the future, so I'm potentially opting towards this if the MC rebuild kit from ZCAR doesn't fit my 71 (it's listed as a 72 and up, and they weren't positive on the fitment either, so who knows). I figure my setup will be pretty similar to yours, not exactly the same but it will give me a basis in my head of where to start. Either way, thank you for the info! You are the man!

Link to comment
Share on other sites

1 hour ago, TUME said:

http://www.jakelatham.com/radical/info/brake_calculators.shtml#MaxGBraking   Try this.

 

I`v got skyline 4-pots front and 2-pot calibers rear. With wilwood pedal assembly. Calculator gives .75 and .625 masters.

So I've looked into this but from what I can tell none of the values you can change actually affect the size of the Masters. It seems to be more of a tool that you would input your own master size (or a master size of what you want to test) to then find a pre-determined braking torque percent balance (at the end of step 3, after inputting the rest of the data). If I input my data in steps 1 -3 (some of the data being my best guess, I admit), then go d own to step 3 and begin testing various sizes of MC on front and back, you can achieve the desired ratio. Based off of my crazy exact calculations (that is sarcasm), my desired MCs would be 1 inch in front and .8125 in the rear for a very close to 50/50 balance (which is also just an assumption I'm making based off of limited knowledge). Am I correct in how this would work, and the guesses at the desired ratio? I will now just sit here and brace myself for some learnin!

 

image.thumb.png.380a547ab171f514f5bbf37b112c1044.png  

Link to comment
Share on other sites

It doesn´t tell you what size masters you need straight away. But you can test different sizes with this. There are not so many size of masters, just try different sizes and you see chances immediately.  it takes really a few minutes.

Link to comment
Share on other sites

7 minutes ago, TUME said:

It doesn´t tell you what size masters you need straight away. But you can test different sizes with this. There are not so many size of masters, just try different sizes and you see chances immediately.  it takes really a few minutes.

well yes, I am more so curious if you're shooting to get as close to a 50/50 braking ratio as possible or is there a more preferred ratio?

Link to comment
Share on other sites

Quote

Maximum braking performance occurs just before brake lockup, as a sliding tire has less grip than a rolling tire, thus tuning brake balance is all about controlling when the brakes lockup. As max performance obviously will occur when all 4 tires (& associated brakes) are doing the maximum work, an ideal brake bias is one that locks the front and rear brakes at the same time. In practice however, locking the rear tires typically result in a rapid spin, and locking all 4 wheels results in a slower spin, especially if the car is trail braking. For this reason, some “extra” front bias is normally used, because when the front brakes lockup the car remains stable (but you lose the ability to steer the car – it just goes straight) and this allows the driver time to recognize the brake lockup and reduce brake pressure to regain max braking performance and control. 

 

I would get near 50/50 with masters and use balance bar with fine adjustment. 

Edited by TUME
Link to comment
Share on other sites

  • 1 year later...

Hey all, I haven't found an answer to this question in my searching. I just finished my setup and I've done the brake lines for the most part. Before I try taking on the road I wanted to verify it was correct. I removed the factory splitter/biaser thing that is in the engine bay (I believe it's the proportioning valve that adjusts the amount of pressure to the front/back?) and ran the lines as such:

 

both front lines meet at a T and from there go directly to the MC. The back lines are pretty much the same. Does that sound right? Does anyone keep the PV for any reason? It seems to me that it is obsolete now but I just wanted to make sure. Thanks in advance!

Link to comment
Share on other sites

The proportioning valve is part of the design, it balances the amount of the flow to the rear brakes so they don't lock up before the front brakes.  If you have no PV then you're probably getting 50% F, 50% R  if you have to slam the brakes on your rears will lock up and you start your skid.  Why would you think it is obsolete?

Link to comment
Share on other sites

10 minutes ago, grannyknot said:

The proportioning valve is part of the design, it balances the amount of the flow to the rear brakes so they don't lock up before the front brakes.  If you have no PV then you're probably getting 50% F, 50% R  if you have to slam the brakes on your rears will lock up and you start your skid.  Why would you think it is obsolete?

 

The thread is about dual masters, so he presumably has different sized master cylinders and a balance bar that he can use to dial in the differential. 

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


×
×
  • Create New...