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Why donít we see more 964ís with dual master setups?

 
Old 12-10-2018, 07:55 AM
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Peteinjp
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Default Why donít we see more 964ís with dual master setups?

In going through all the possibilities for the 964 brakes and having read Bill Vís numerous responses about the master cylinder size- or lack of sizes- I started to wonder about the possibility of dual masters. It seems like a good solution all around- no booster needed, adjustable bias allowing for different settings to accommodate track conditions, street use, rain etc. Just to be clear I doubt I will ever go that way because I already have enough projects and need to get the brakes sorted as easily as possible.

Anyway it occurred to me that the dual cylinders are a good, if not the best, solution for many of us regarding the use of larger calipers as well as addressing bias. Dual masteres with adjustable bias are a better solution that simply removing the bias valve or even adding an adjustable valve. People go as far as adding CAE shifters, larger lighter brakes, fully adjustable dampers not to mention re-gearing and 10ís of 1000ís on engine work- but I have yet to see what seems like a very effective mod in terms of dual masters. Am I missing something? Is it because of the removal of ABS?

Interested to hear thoughts on this for sure. I did find one lonely facebook post by Rothsport racing:



https://d.facebook.com/story.php?sto...78&__tn__=%2Cg

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Old 12-10-2018, 09:51 AM
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Bill Verburg
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Originally Posted by Peteinjp View Post
In going through all the possibilities for the 964 brakes and having read Bill Vís numerous responses about the master cylinder size- or lack of sizes- I started to wonder about the possibility of dual masters. It seems like a good solution all around- no booster needed, adjustable bias allowing for different settings to accommodate track conditions, street use, rain etc. Just to be clear I doubt I will ever go that way because I already have enough projects and need to get the brakes sorted as easily as possible.

Anyway it occurred to me that the dual cylinders are a good, if not the best, solution for many of us regarding the use of larger calipers as well as addressing bias. Dual masteres with adjustable bias are a better solution that simply removing the bias valve or even adding an adjustable valve. People go as far as adding CAE shifters, larger lighter brakes, fully adjustable dampers not to mention re-gearing and 10ís of 1000ís on engine work- but I have yet to see what seems like a very effective mod in terms of dual masters. Am I missing something? Is it because of the removal of ABS?

Interested to hear thoughts on this for sure. I did find one lonely facebook post by Rothsport racing:




964RS/LW is the only 964 That I've ever seen w/ dual masters

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Old 12-10-2018, 12:40 PM
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wallra
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wouldn't it be easier to install adjustable brake bais valve like race cars have. https://www.maximummotorsports.com/A...orts-P687.aspx
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Old 12-10-2018, 01:45 PM
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Originally Posted by wallra View Post
wouldn't it be easier to install adjustable brake bais valve like race cars have. https://www.maximummotorsports.com/A...orts-P687.aspx
Easy isn't always best. A p/v can only be used on the rea circuit(s) and only reduces line pressure above a certain point called the knee. It can do nothing to increase the effectiveness of the circuit, only decrease it.
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Old 12-10-2018, 01:52 PM
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you can use a Tilton with ABS. With that car, I'm going suggest durability + adjustability is the reason. A friend has a 993 with a tilton setup. You can also add motorsport ABS to these (my shop has an M4 setup in a 993 they are building). You can also add an adjustable bias to the setup as it exists now. Will require some plumbing. The tilton setups with a balance bar are effectively infinitely adjustable and very fine grained.

Why? Well I'm not sure you can add assist with the tilton setups. (maybe you can?)> its sort of that line for full on race car vs. street balance.
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Old 12-10-2018, 05:27 PM
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Originally Posted by Spyerx View Post
you can use a Tilton with ABS. With that car, I'm going suggest durability + adjustability is the reason. A friend has a 993 with a tilton setup. You can also add motorsport ABS to these (my shop has an M4 setup in a 993 they are building). You can also add an adjustable bias to the setup as it exists now. Will require some plumbing. The tilton setups with a balance bar are effectively infinitely adjustable and very fine grained.

Why? Well I'm not sure you can add assist with the tilton setups. (maybe you can?)> its sort of that line for full on race car vs. street balance.
The issue mostly arises w/ 964 because though there are good front upgrade paths there aren't optimal rear upgrade paths, The rear will always be anemic wrt the fonts here unless you do what you did and change the whole thing to a very expensive aftermarket setup. 993 doesn't have that issue, the 993RS setup is just about right, sure it can be improved w/ aftermarket ABS and/or dual master but the improvement is so minor that most won't even think about it.

The water cooled cars seem to be more in need of a better ABS than the air cooled. These cars are the ones that suffer from 'ice pedal", I've seen it on all models right up to 993GT3RS


In general I am really leary of most after market ABS changes, I've seen several Cayman/Boxster installs that were questionable at best. The best brakes i've seen on one of those cars was a dual master setup
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Old 12-16-2018, 05:04 PM
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Does anyone know the diameter and stroke of the 964 RD/LW twin brake master cylinders. It looks like they are the same with single outlet. Does not like it would be hard to set up. Are the lines run through the ABS unit or bypassed (ABS removed)?
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Old 12-16-2018, 05:57 PM
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Originally Posted by Gus View Post
Does anyone know the diameter and stroke of the 964 RD/LW twin brake master cylinders. It looks like they are the same with single outlet. Does not like it would be hard to set up. Are the lines run through the ABS unit or bypassed (ABS removed)?
Just an educated guess, but probably 17.8/15.88mm(7/10//5/8"), that puts the bias between 1.476 and 2.196 depending on where the bias bar is placed w/ a pedal ratio of 34.5

19.05/17.78mm(3/4//7/10") also works giving the same bias ratio but changing the pedal ratio to 28.96 which is getting low for non boosted brakes, though a fit driver should be fine
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Old 12-16-2018, 10:12 PM
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Thanks Bill - you have such a great knowledge when it comes to Porsche brakes. The group is really luck to have your expertise available.
Follow up - could you/would you run the brake lines through the ABS or just by pass?
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Old 12-17-2018, 02:33 AM
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If I recall correctly this car has no Abs. The trunk looks like a trunk should! -edit- take a look at the pic above!

And yes- I too consider myself lucky to have Bill on board! Thanks Bill!

pete
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Old 12-17-2018, 11:04 AM
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Originally Posted by Gus View Post
Thanks Bill - you have such a great knowledge when it comes to Porsche brakes. The group is really luck to have your expertise available.
Follow up - could you/would you run the brake lines through the ABS or just by pass?
I suppose it would depend on what you wanted to accomplish, but personally I would want to keep ABS

PS I just reran the #s, originally I forgot to change the rotor size and rear caliper piston sizes

the 19.04/17.78 gives a range of 1.338 to 1.991 w/ a pedal ratio of 31.15 this is right where you would want to be

the 17.78/15.88 gives a pedal ratio of 37.22, this works ok for normal use but is not desirable for hi perf/track use

the next stp up would give a pedal ratio of 26.8 this is again getting too low, it would take a lot of leg


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