Great!
Greg
----- Original Message -----
From: Louis & Laila <bwana@c2i2.com>
To: <ellis838@concentric.net>; <alpines@autox.team.net>
Sent: Friday, 16 February 2001 07:09
Subject: Re: Wilwood M/C
> Jim,
> Are you lucky or what?! I just spent the last week figuring this all
> out! I had my physics books, and automotive repair books all laid out. I
> even had help from the physics genius at UCSD! SO, here is the $64,000
> answer.
> Think in terms of a simple system. i.e., a master and a slave, with
an
> area of 1" square face on the piston. If 100 pounds of pressure is placed
on
> the master, that will transmit exactly 100 pounds of force through the
> slave. Now, increase the diameter of the slave cylinder to 2" squared, so
> that it is twice as big as the master. If 100 pounds is placed on the
> master, there will be 200 PSI through the slave.
> Now, rather than have 1 slave twice as big, just put two slaves, each
> with a face of 1 square inch. The pressure in the system is still the
same,
> no matter how many slaves there are. Therefore you will have two slave
> generating 100 pounds, for a total of 200 pounds. In a car, with 4 wheel
> cylinders, you would have 400 pounds of force for the one master at 100.
> Going back to the simple system, you can see that decreasing the size
> of the master or increasing the size of the slaves, creates the best
braking
> for the car. So, the ideal situation, is to have wheel cylinders that are
6"
> in diameter, and a brake master that is 1/4". OF course, that sounds
absurd
> because there is no way that the brake master could supply enough fluid to
> power 6" wheel cylinders. It would bottom out before the pistons moved
> enough to make contact with the drum.
> This is where the trade off comes. Here is a simple rule for you to
> remember. Smaller master equals MORE pedal travel, and LESS felt pedal
> pressure. Larger master means LESS pedal travel, but STRONGER quadriceps.
> You want to increase braking power, yet still have enough brake fluid so
> that your pedal doesn't bottom out. And, you would like to have a margin
of
> error, so that the pedal still could go down farther if there was a little
> air in the system.
> Lets talk about the early cars. They did not have a servo, so braking
> power was related to the quads of the driver. The series I & II used a
.700"
> master. It escapes me right now, but I believe they used a 7/8" (.875")
rear
> slave. The Series 3, which was boosted, used a .750", and the 4,5, and
> Tigers used a .875", and of course, they were boosted. However, on the
rear,
> they used a 3/4" (.750) slave wheel cylinder.
> So, you can see that on the early cars, to get the felt pedal
pressure
> down, they used bigger slaves in the rear, and a smaller master cylinder.
> On the later cars, since felt pedal pressure was reduced by the servo
> (when it wasn't sucking up the fluid or locking up), they used a bigger
> master for safety, with smaller slaves.
> All that aside, I drove my tiger without servo for 8 years every day
> with no problem. Now that I am servo spoiled, it would be a problem!
> There are 2 other things that affect brakes that you must think
about.
> The radius of the braking force at the wheel will affect how much pressure
> you need. If the wheels are ten feet in diameter, that is like a 5' prybar
> putting torque on the brakes. So, decreasing the size of the tires
DECREASES
> the amount of braking force required. And INCREASING the sizes of the
tires,
> requires trips to Gold's Gym and the quad master.
> The last one is the diameter of the brakes. A brake drum of 10'
> requires less force than the brake drum of 5', again, it is the prybar
> effect.
> The real "last" thing is pad composition, but that is a matter of
> choice and race conditions/requirements.
> So, all that said, you can't do much about your brake drum, or rotor
> size, so we look at them as constants. You will probably put smaller tires
> on, so this will reduce the amount of felt pedal force. You will also
reduce
> the master cylinder bore, so again, less pedal force. If you have a series
> 3,4,5 or tiger, you "can" get a set of rear slaves from a series I or II,
> and this will give you better braking force in the rear. You would have to
> experiment with this since you don't want these locking up on you before
the
> fronts take over.
> For safety purposes, I am going with a 13/16 bore, dual master. It is
> from a 82-84 Honda Accord. That way, if one system fails, I can still stop
> the car. To clear the Weber carbs, I moved the brake master to the clutch
> hole, and then welded in the gear for a clutch in the firewall, and used
> Tiger pedals and Tiger clutch master. I have strong quads! Lou
> ----- Original Message -----
> From: <ellis838@concentric.net>
> To: <alpines@autox.team.net>
> Sent: Thursday, February 15, 2001 6:13 AM
> Subject: Wilwood M/C
>
>
> > Hello,
> > Question, is the Wilwood master cylinder with the 3/4 inch bore big
> > enough to replace the stock 7/8 inch unit and not cause any braking
> > problems due to the different bore size. I want to use the Wilwood to
> > clear a set of side draft webers. Thanks Jim
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