Help !!!!Brakes & Master Cylinder

[rdorman]

Originally Posted by Jerry Clayton

with a pedal ratio you stated of 6.5 to 1---you are only moving the master aprox 1 in with 6 in pedal travel--a 3/4 master won't displace enough fluid to fill your calipers---you need to get bigger masters

Not to disagree with Rman but your problem at this point is strictly hydraulics---c-g and g forces don't apply---yet--

Jerry

Not a problem Jerry. The 3/4 master will travel about .22" and the rear about .14" for a optimal amount of radial run out (kicking the piston back) and deflection (zero!). That is on a 1.1" max travel for tilton master cylinders. I never would get any where near close to that max number for obvious reasons! Not sure what you mean by 'your problem'. If you are talking about the intermittant pedal he is having, yes, it is some form of hyraulic or mechanical problem. If you are refering to my working with master cylinder sizes, then actually I use CG, various CFs, aero loading, weight transfer, etc, etc, etc to play with different sizes.

My issue with recommending master cylinder sizes at the moment is CG height is unknown and he has another issue that needs to be resolved. Additionally, he states that no matter how hard he pushes, he can not lock the brakes. Assuming that all is right (and we know it is not), I would be leaning him towards smaller MC's (at least in the front). I have a similar setup in my Cobra on the front and the MC is a 5/8's and works very nicely with minimal travel (about 2" total). Same calipers, pedal ratio, etc.

[priobe]

rdorman,

I agree with you about the plating possibly being the problem.

Jerry,
Thank for the info and its funny you should say that. keep reading.


I contacted Wilwood and asked them how is it they came up with the solution to my problem. They told me that the setup which I have is the exact setup used in Superformance cars and it works fine.

Ok.....

I contacted Tilton and spoke to the Lead Engineer. I ask him the same question and why is it that it differed from Wilwood. He responded by saying if you contact Wilwood and ask them for a Master Cylinder setup they will almost always respond 3/4 front 7/8 rear regardless of the car.

He told me that the reasoning for the 1 1/8 bore size to the rear is because I am running a large rotor and larger pistons for the rear caliper. At that time he mentioned that he bets that Wilwood did not ask for any specification on my vehicle, which is true. He told because of the large multiple piston size in the rear combined with the large rotor that it will not take much to lock up the rear brakes. He said possibly 250-275 psi to lock the rear and 400-450 to lock up the front.

I am feeling confident that Tilton's suggested method is the better of the two.

I am not sure if this is the solution to my problem or if it is because I had the cylinders plated. By removing the plated cylinders and installing the 7/8 front and 1 1/8 rear, I will eliminate both possiblities.

Tilton also suggested not to run anything above the Wilwood 570 brake fluid because it will eatup the seals over time. He went on to explain that if you are using the car for racing then it does not mater because you should be rebuilding the masters and the calipers more often.

Final result is to order 7/8 and 1 1/8 bore from Tilton. "With out having them plated"

But first I will try to bleed the system individually one last time before I place the order.

Coud some Superformance guys comment on you brake setup please!!!!

[rdorman]

I played with both the Wilwood recomendation and the Tilton one. Both will bring you car closer to balanced bias then you are now (bias bar centered of course). One will simply result in about 15 pounds more pedal force then the other. Tilton will be right about 75 pounds of force which is the commonly recommended starting point for a race car setup up. After that comes driver preference and style of course. Personally, I have found 75 pounds nice in race car where you are strapped in well in a seat with little padding that does not move around much... haven't liked it much in the typical cobra.

The Tilton combination is well balanced (all looking at a 1g stop and a 20" CG height)). A slight forward bias of about 2% while the wilwood is more like 16% rear (about 32% rear now). Rear would need tuned out. Other combos could be 5/8 and 13/16 (4% front bias), .7 and 7/8 (3% rear) and 13/16 and 1" (6% rear). Ordered in the rate of increased pedal effort from the 5/8 (40 pounds or so) to the Tilton combo of about 75 pounds.

Regardless of what you do, can't wait to hear the results.

[priobe]

I should have never plated the M/C so soon. I could kick myself

[rdorman]

Don't kick yet, you may replace them and that was not the problem! If it wasn't, look at the bright side, you will have some purdy MC's that I am sure some one will want. It just seems like you have carefully done everything else (although I don't recall you talking about bedding, bias adjustment or alignment) so they are the big ?

[priobe]

What is bedding?

As for the bias adjustment I have left them in the center and moved it from right to left. When I set the to move force in the front the pedal pressure is consistant but more travel and the car still does not stop well.

[rdorman]

Bedding: http://brakepads.wilwood.com/03-tech/index.html

With a 2.5" distance clevis to clevis you would probably have to move it about 3/8" off center, towards the front MC of course, to get it in the ball park.

[rdorman]

Sorry, that is more like 3/16" off center to start on a 2.5" clevis center line.

[priobe]

WEll,

Here is update.

I tried bleeding the brakes 1 more time with the 3/4 MC. I bleed each system independently. I noticed that the front MC seems alittle spongy. The rear are rock solid.

After test driving the brakes still do not feel right. same issue.

[priobe]

just received the 1 1/18 for the rear and 7/8 for the front.

I will see if this will solve my problem.

Stay tuned!!!!!

[priobe]

Well I installed the MCs and the pedal is a lot harder but the tires will still not lock up.

I contacted Tilton to see what they have to say.. I will post the response

[rdorman]

Originally Posted by priobe

When I pull the car out of the garage and it begins to roll back and I hit the brakes, the pedal has more travel maybe 5-6 inch. As I approach a stop sign if I pump the pedal 1 time the pedal becomes hard again ...

Did the problem above go away?

As for them not locking up... I mentioned before that I thought the tilton combination was to large. Sure it is balanced, just to much pedal effort IMHO.

[priobe]

Yes,

The above problem went away.

I have been in contact with Tilton and now he is suggesting a 7/8 front and 1" for rear.

I am waiting to hear back on my options for these MCs.

I still have not heard back yet.



I am starting to think that Wilwood was the way to go with the recommendation of 3/4 front 7/8 rear.

I just want this to stop already ........literally

I am going to post a thread for Superformance owner and their brake setup.

[rdorman]

Good to hear about the problem going away. We now know it was the MCs.

Tilton is steering you toward smaller MCs because they feel the effort required is to high, as I thought it would be! Me, I would be leaning more towards the wilwood size recomendation, a little less rear bias then the latest tilton recomendation (still crank in some front on the bias bar about 15% to start) with a large increase in pressure (or you can look at it as a large decrease in effort required). You can go back to my post on 11/8 at 2:30 for more sizing options.

Do you have one of these: http://www.autoanything.com/brakes/61A3154A0A0.aspx

Tons of places sell them. A local speed shop or other automotive place should have them. Invaluable tool and when you think about what you are spending on MC's, a cheap tool as well!

While you are waiting on your MCs go and properly bed your pads!

[undy]

smaller MC = less pedal effort and more piston/foor travel

larger MC = higher pedal effort and less travel

I've got the 5/8" in the front w/ 3/4" in the rear. I'm running the 12.19" Wilwood fronts w/ the granada rears.

[rdorman]

That is the size I am running. Or maybe it is 7/8" rear. Anyways, similar.

[priobe]

rdorman,

What should the pedal pressure be if I am looking at the gauage?

Undy,

5/8 front 3/4 rear

What calipers are you using?

[rdorman]

I use the gauge in a number of ways. I use it to check bias setting, I have used an electronic scale placed on the pedal and made note of the two readings (foot pressure versus pressure at the caliper), heck I once used a fish scale to pull on the pedal. It is mainly for data collection and diagnostics. Teams with tons of data can use it to static set cars up for different tracks. For us, it tells us that things are working as they should and it confirms that the calculated numbers are correct so that we can make changes with a greater degree of certainty. You don't have to have it but it is a tool that I bet most of your buddies don't have in their box... so you can impress your friends with it

[undy]

Originally Posted by priobe

rdorman,
Undy,

5/8 front 3/4 rear

What calipers are you using?

Wilwood 4 piston calipers in the front. The rears are OEM Exploder brakes, on a Currier 4 link 9".

[priobe]

rdorman & undy

Well I have contacted Tilton and they are of no help. As this matter continues I am becoming more familar with the m/c setup. Obviously the 1 1/8 for the rear was way off. I contacted Tilton to see if they would do something for me in reagards to the useless 1 1/8 m\c and they said no.

I will have to be creative on this one I guess.

I have contacted Wilwood which is the company I should have listen to in the first place for their guidence.


I know Wilwood said 3/4 front 7/8 rear but I am thinking 5/8 front and 3/4 rear.

What do you guys think???????

By the way here are my brake pads Poly Matrix

front 15Q-6827k - 7320Q
Rear 15Q6824K - 7112q

I dont want to order new M\C and have a bunch of paper weights.