CSX 7000 Brakes
 

Can anyone at Shelby American answer a brief question for me, please? On a CSX7000 series car, does the larger master brake cylinder go to the rear or front brakes? I have received conflicting answers. Thanks very much!

The 7/8" goes to the front circuit, and the 5/8" goes to the rear circuit. This is from the Baer rep. :)

Kris, thanks. I guess Baer is the brand of brakes?

jim
which way are the master cylinders mounted now?

The larger cylinder is on the front. The mechanic removed the lager cylinder and found a little debris. Anyone know where to get rebuild kits? Nostalgia Motorcars has been difficult to contact according to the mechanic.

jim
i'm pretty sure your going to want to switch the front and rear master cylinders.

Why do you say this? Is there something you know that the engineers at Baer don't know? I know you are a mechanic, so I am interested in your point of view. :confused:


Jim, Baer is the company who does the brakes for Shelby. :)
http://www.baer.com/

My hi-tech has the 3/4 in front and the 5/8 in the rear as far as masters go. I think that the bigger master goes in front. A 3/4 master would give you more leverage on the fronts versus the 7/8. Scott

kris
it's actually pretty basic hydraulics.use this for an example:
if a woman is wearing a stilleto heel on one foot and a flat shoe on the other which foot is going to apply the most presure where the shoes meet the ground?.........john

I assume more braking pressure needs to be exerted up front, correct? Every vehicle I have ever piloted has had this braking bias, even 911s which actually rule in the braking category. Have you also considered the thermodynamics of brake fluid under racing conditions? What is your brake fluid of choice that you recommend?

TC, your GasBag

Jim. sorry for the worries, the above post was directed to the professional mechanic above.

toy collector
i don't think this is what jim was talking about with his post but yes thermodynamics play a huge factor in a racing situation where the braking friction is tranfered into heat which boils the brake fluid. in this situation you may consider sythetic brake fluids as they have a higher boiling point and tend not to attract moisture as normal brake fluids do. the only real problem with sythetic fluids that i have used is that the pedal or lever effort can be vague compared to normal brake fluids.

corrected for mr. buckley

I didn't realize that synthetic brake fluid was compressible!

The above presupposes that the caliper pistons are the same front and rear. Front and rear master cylinder bores are different for two reasons; 1, to give a forward bias to the brakes (fronts should always lock before rears), and 2, to allow for the fact that the caliper piston arrangement/size is often different front/rear. e.g. 4 or 6 pistons on the front, 2 or 4 on the rear. And this does not allow for the fact that the piston areas may be different as well.
In that case, a higher volume of fluid needs to be moved to the front calipers to give the same piston displacement.

In the case of the original question, there was obviously a fault/blockage leading to a total lack of braking effort at the front. I hope that is sorted by now.

However, the issue of which master cylinder should operate the front brakes is more complex. I can't believe that the brake supplier would specify it wrongly?

Can anyone authoritatively tell me what the brake caliper configuration is on this car front vs rear?

Oh -and as to the question of the womans foot pressure, the answer is, assuming she is standing 100% vertically - the same total on each foot, but a different lb/sq in for each. Does that help any of us?????

Wilf...assolutely incredible how you can get right to the essential point, but I do wonder about one thing...

What else is she wearing?

The Big Gasbag!

P.S. While I am not a professional mechanic, I know better than to stay at a Holiday Inn. I believe the essential reason for the front needing the bigger master is as Wilf points out...matching components. Bigger brake swept area, pistons, etc. need a greater volume of fluid. The front better have the bigger brakes! A properly functioning master will yield the pressure needed.

If we were to follow the smaller hole-higher pressure analogy, then as brakes get bigger and more pistons are added, we should drop down to...say...1/8? Piss on that...wait, yeah, that's the ticket...:JEKYLHYDE

The "average" human being exerts 7 to 10 times their normal body weight on each foot with each step. In the case of brake application, closed kinetic chain and vector forces become applicable in the recumbent position. Basically the gastrocs counter balance the quadraceps in extension of the leg and plantarflexion of the foot. Since the gastrocs and the soleus combine to form the triceps surae which forms the Achilles tendon and whose major function in the recumbent position is to plantarflex the foot as with brake application, the force is a factor of patient's weight, leverage from seat position and muscle girth/strength plus endorphin stimulation. If the brake is applied as an emergency response verses a calculated movement, it will be applied with more force, quicker and disregards most "natural" formulas. Example: we've all heard stories of mothers with super human strength lifting cars that have fallen off jacks and trapped family members. Normally these same indiviudals might be capable of nominal physical feats. Most of the strength is derived from the legs in this maneuver.

Disclaimer: I'm NOT a professional mechanic and don't pretend to be one in normal daily conversations but I play a bona fide doctor during the daytime, who knows the muscular functions of legs and feet! :D

Reducing the size of the master cylinder does indeed increase the pressure in that side of the system. Increasing the area if the pistons increases the presure at the rotor as well. Adding pistons or increasing their size AND reducing the master cylinder size would each contribute to more braking force on that side of the system. While developing greater pressure for a given pedal effort, a smaller master will cause more pedal travel. I can't imagine that baer doesn't have the system balanced, especially if it is working in other cars.

Scott

Hold it--I am the master at boiling brake fluid--even did it right in front of the SAI trailer at SAAC 27--big fireball and all. :D

I experimented with various fluids afterward and found no discernable difference in foot/pedal pressure between the different types of fluids.

Jim, I am sorry that many of these posts have detracted from your question and I truly hope that your setup is working great.

Yea ,.......OK Dan......
....but not every one has seen your brakes

with apologies to moderators and Thread Hijacking Police

"........if a woman is wearing a stilleto heel on one foot and a flat shoe on the other which foot is going to apply the most presure where the shoes meet the ground?........."

This is right out of the book of -Principles of Hydraulics-, by Christian Dior.

MR GASBAG to you!