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In Derek Seward's Race Car Design and in some of the videos on race car braking systems, such as this one, it is mentioned the use of two master cylinders, one for the front brakes and one for the back. The bias between front and back being set using different lever length between the pedal and each master cylinder.

Why is this configuration preferred over a single master cylinder of same surface area and a bias valve? Is it safety requirement to keep both front and back hydraulic systems entirely separated or is there any technical benefit?

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    $\begingroup$ @RodrigodeAzevedo don't think the edit changed the meaning much - it was pretty clear before, if you are after rep then writing an answer or two is probably quicker... $\endgroup$
    – Solar Mike
    Aug 3, 2020 at 19:19
  • $\begingroup$ @SolarMike 30 views so far. If 20% are interested in the book, that's 6 people. Does it make sense to steal a second or two from 6 people when including a link is easy? Why not include a field tag? It helps those who subscribe to tags. If the standards were a bit higher, perhaps this site would have left Beta a while ago. $\endgroup$ Aug 3, 2020 at 19:27
  • $\begingroup$ @RodrigodeAzevedo Never even opened the link to answer the question so your assumptions about how many check the link out are most likely way off... If you write some decent answers you will help improve the standards you are flag-waving so much about... $\endgroup$
    – Solar Mike
    Aug 3, 2020 at 19:30
  • $\begingroup$ @SolarMike It's easier to answer questions when I can actually find them. I can only answer questions in very specific fields. I am not going to stare at the front page of Engineering SE all day until something I can answer pops up. Proper tagging is required, for I subscribe to tags. $\endgroup$ Aug 3, 2020 at 19:44
  • $\begingroup$ @RodrigodeAzevedo then use the tags and « unanswered »... $\endgroup$
    – Solar Mike
    Aug 3, 2020 at 19:51

2 Answers 2

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It is so that balance can be adjusted between the front and rear brakes more easily, often times by the driver as he races. In a regular street car, there is a proportioning valve that determines how much pressure goes to the front brakes, and how much goes to the rear. The proportioning valve generally puts the back brakes on first, but then limits absolute pressure to the rear brakes. That way, the rear brakes come on early, holding the car straight, but never come on hard enough to lock, which usually results in spinning the car. In a race car, the brakes should be set up a little differently. The rear brakes should be on the verge of locking in a fast stop, because the driver can then use the brakes to put the car into a controlled oversteer condition on the way into a corner, getting the car to rotate and point towards the corner exit so that the driver can switch to the gas pedal sooner. Keeping the brakes adjusted this closely is difficult, because changing fuel loads, track conditions, or brake wear can subtly alter the point at which the rear brakes start to lock. So, a dual master cylinder setup is used. There is an adjustment that the driver can make on the fly that shifts mechanical advantage from one master cylinder to the other when the brake pedal is pushed. This allows the driver to fine tune the braking system, keeping it set exactly right as the race progresses.

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Two cylinders are often needed due to the fluid input needed by the multi-pot calipers used front and rear.

The control of balance is also handy.

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  • $\begingroup$ I mean at equal surface area what would be the benefit of two vs one cylinder? (I will update my question) $\endgroup$
    – ITChap
    Apr 11, 2020 at 19:25
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    $\begingroup$ Dual or multiple circuits $\endgroup$
    – Solar Mike
    Apr 11, 2020 at 19:26

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