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Pedal box question


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Hi guys,


Quick question, with an after market pedal box with its own master cylinders, you obviously dont run the stock booster right? So surely the effort is a lot more? I have a 620 with drums all around and currently the booster interferes a but with my r1 carbs.




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I made my own intake for the R1s. As you can see they are no where near the brakes.




The pipes come out at 90 to the head then the carbs then I tried lengths of muffler pipe that I flared with a hammer




Then home made filter box and zx filter. This was just a proof of concept.




Then I shortened the tubes to move the improved filter box filter down mostly as it rubbed the hood.




Nothing was in the way of the master cylinder or the booster. The air filter would be the only other thing that might get in the way but it was fine.


Do you have a picture of yours? Is it your air filter(s) that does not clear?






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If you are running 4 corner drum brakes I would not recommend spending the $700+ for a pedal box setup.  To answer your question though, no, manual brakes do not automatically mean you will have a harder pedal.  However, it isn't just as simple as just buying a pedal box, bolting it in and putting your master cylinder one it.  The pedal box will undoubtedly have a different pedal ratio than your stock.  I think the stock is around 4.5:1, where an aftermarket such as a Tilton will be adjustable from 5:1 to ~6.2:1.  I think Wilwoods are somewhere around 6.1:1 and I'm not sure they are adjustable.  In any case, this additional leverage gives you a mechanical advantage between your foot pushing the pedal and the pedal pushing the master cylinder rod. 

Once you figure out the ratio difference, you would then need to adjust your master cylinder sizes accordingly to balance pedal force and brake force.  A few things to keep in mind... the larger the master cylinder, the higher the foot pressure, but least amount of pedal stroke.  The inverse is true in that a smaller master cylinder will result in less pedal pressure to brake force, but will result in a longer pedal travel.  On top of this you will need keep in mind your chosen the master cylinder volume in relation to your caliper's fluid volume and ensure so there is enough fluid available to fully extend the calipers pistons (in your case the brake cylinder).  You will need to balance all these things. 

Then finally, you will need to select your front and rear master cylinder's sizing appropriately to apply the correct bias between front and back.  You don't want this 50/50 because during a braking manuever a large majority of the vehicles weight (~70% is a common figure) is transferred to the front axle of the vehicle.  Due to this you need to have most of the braking force applied to the front axle; failing to do so will result in your rear brakes locking up first.  Most pedal boxes will have an adjuster bar, but you will want the primary balance set by the size difference in master cylinders leaving the balance bar for minor adjustments to account for things like weather or track conditions.

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If all you are doing is removing the brake booster the pedal effort will most certainly go up. You can show yourself the difference by pulling the hose off the booster and plugging the end. Leave yourself lots of room on the driveway to get stopped when you try them. The booster reduces effort by about 50%. See what you think.



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