Re: Brake Indicator Switch and Brake System Balance
Posted: 11 Mar 2010 20:02
Ok, here it is...bare with me while I load it up.
Ok, so I’m riding through the forest last night, lost in my thoughts on the brake issue, between trying not to lose a lung.
First thing I decide, is that it would be too hard for me to try to explain the brake proportion valve CLEARLY, when the good old Internet is filled with enough information to get Dislexidime lost forever. I don’t usually go looking for stuff, but this topic got me looking on the Net, and I was boggled at the information out there. So, with that in mind, I am attaching the link to the TILTON site, for HOW THE PROPORTIONING VALVE WORKS! And, more importantly, it shows the graph…which is very visual. This was going to be the tough part of the explanation…so I am taking the easy way out.
http://www.tiltonracing.com/pdfs/98-126 ... valves.pdf
Now, I can talk about the valve from the drivers perspective, that I know, have lived with, and I think can comment from true experience.
My valve is and old DIRECT CONNECTION one, made by Kelsey -Hayes. It is an infinitely variable one, with a range from 100 to 1,000 PSI. It has small lines scribed on the screw shaft, which are kinda useless. I just put a reference mark on the valve mount, and, over time know how many turns to turn the knob, for a bias setting, which I note in my log. You can look at the graph in the Tilton link, and basically see what my screw type one looks like, in terms of the “knee point”. It sits by the passenger seat ( see picture). I have learned where to put it, based on going out on a straight stretch of road, and getting the brakes up to whatever I thought would be the appropriate temp, and see how the car feels under truly severe, race type braking situations. Don’t overheat the brakes, or you will not really get a reliable setting. The setting is the hard thing to describe, as, it is both determined, by what you may hear, and, more importantly, what you may FEEL in the seat of your pants. If you can hear the rear tires ripping rubber off…well…you have too much rear brake. You just want the car to be slowing down VERY HARD, and just have a “sense” as the weight is really finishing it’s transfer, that rear end ( read tires) are ALMOST getting to feel like you are on skippy bumps. That’s the hard part, and it just takes some testing, to get to that point, and maybe back it off just a tad more…depending on what you/the car, like.
I have had the valve on my car for some 30 years now. Seems I never noted in my log book when I put it in, only reference the adjustments. So, with my master being the 15/16, the BMW 2002 4 piston steel calipers on the rear, and the front being the Brakeman 4 piston calipers, this is what I do with my brakes, via the proportioning valve. I am not going to get into the bore sizes, etc, as that is a discussion unto it’s self, and best left to those with good math skills, and able to build a balanced system, just using bore size matching alone, which still would not give you the ADJUSTABILITY, should you want it.
In the case of my ride, I can adjust from the extreme of having severe rear lockup, to NO lockup at all, barring actually locking the whole system up, which I have never done. In my slaloming experience, one learns to be very smooth, and able to take the tires to incipient lockup, but no more.
For driving on the street, which primarily means we have cold pads and rotors when we get onto the brakes, I have it set so that the front is doing most of the work. I have it set this way, should I have to really hit the brakes when cold, I will not get any rear lockup, and possibly cause me to want to come around. That being said, I have just enough rear bias, that when I enter a corner very fast, and I like to use trailing brake, the rear JUST feels like it is at the point of locking, and helps the car turn in a tad.
When I would road race, with sticky race slicks, I did not want the front doing most of the work, for all the reasons. I had more grip on the rear, so why put more heat into the front pads and rotors, at a disproportionate rate, by having HUGE weight transfer to the front. I would screw the knob IN, thus ALLOWING more pressure to the rear ( again, you must read the Tilton link, as it explains about the pressure!!!!). This would decrease the weight transfer, and make the rear work harder, which the car could tolerate. Now, there are a lot of factors going on here, main one being temperature. It took me a while to figure out the optimum amount to change to knob, as it took awhile for the pads/rotors to get to their equilibrium…KINDA. Obviously you keep introducing more heat, if you have undersized rotors, and or poor cooling, which can start to change things too. Balance..pun intended….becomes just a case of both testing, and knowing your car and driving style.
I had a problem to deal with also…pad choice. I could NOT get the same compound, from the same manufacturer. This gave a problem of have a relatively grippier pad at the front, which both caused the weight transfer to happen, and the lightly loaded rear to be not doing much. In my case , the difference in the coefficient of friction from front to rear, made for some interesting braking situations. Having the ability to fine tune things with the valve was a bonus, let alone a necessity for good PREDICTABLE braking.
And, what fuel load do you have? More weight over the rear, you can get away with more rear bias. This is really only a factor in a road race setting, where you are getting lighter in the rear, and want to back off the rear bias. That is where the TILTON LEVER type is likely better, you have 7 click stops.
As the so called DOT street legal race rubber has come along, the better grip has let me run with a bit more rear bias, and, this summer I am going to try dialing some more in. I will be the first to admit I am just not a hero when it comes to an over steering car. I have been very conservative about how much rear bias I have. I can really haul down INTO a corner, and as I have harped about before in regards to rear toe change, be able to get HARD on the brakes if I have to, and not worry about it either locking, or trying come around under heavy braking.
So, do you NEED a proportion valve…depends! Read the above again. Coming from my racing back ground, and a car(s) that were ALWAYS evolving, ever changing tires and grip……I NEEDED ONE..PERIOD!
I have done so many types of events’, it was the only way to both stay competitive, and safe. I had drum brakes originally, and when I changed to the “green stuff” shoes, things started to go to hell, in terms of brake balance.
We also now, and have for years, put on a hodge podge of different components, to do with the brake system, none of which were ever designed to be compatible.
My brake system uses all the stock line plumbing, except steel braided lines for the front and rear calipers. My shuttle valve is intact, as is the “brass” T at the fire wall.
So, botttom line for me, is that I have a complete range of adjustment for my brake balance, letting me maximize
my decelerations, at a hell of a rate!!
Ok, so I’m riding through the forest last night, lost in my thoughts on the brake issue, between trying not to lose a lung.
First thing I decide, is that it would be too hard for me to try to explain the brake proportion valve CLEARLY, when the good old Internet is filled with enough information to get Dislexidime lost forever. I don’t usually go looking for stuff, but this topic got me looking on the Net, and I was boggled at the information out there. So, with that in mind, I am attaching the link to the TILTON site, for HOW THE PROPORTIONING VALVE WORKS! And, more importantly, it shows the graph…which is very visual. This was going to be the tough part of the explanation…so I am taking the easy way out.
http://www.tiltonracing.com/pdfs/98-126 ... valves.pdf
Now, I can talk about the valve from the drivers perspective, that I know, have lived with, and I think can comment from true experience.
My valve is and old DIRECT CONNECTION one, made by Kelsey -Hayes. It is an infinitely variable one, with a range from 100 to 1,000 PSI. It has small lines scribed on the screw shaft, which are kinda useless. I just put a reference mark on the valve mount, and, over time know how many turns to turn the knob, for a bias setting, which I note in my log. You can look at the graph in the Tilton link, and basically see what my screw type one looks like, in terms of the “knee point”. It sits by the passenger seat ( see picture). I have learned where to put it, based on going out on a straight stretch of road, and getting the brakes up to whatever I thought would be the appropriate temp, and see how the car feels under truly severe, race type braking situations. Don’t overheat the brakes, or you will not really get a reliable setting. The setting is the hard thing to describe, as, it is both determined, by what you may hear, and, more importantly, what you may FEEL in the seat of your pants. If you can hear the rear tires ripping rubber off…well…you have too much rear brake. You just want the car to be slowing down VERY HARD, and just have a “sense” as the weight is really finishing it’s transfer, that rear end ( read tires) are ALMOST getting to feel like you are on skippy bumps. That’s the hard part, and it just takes some testing, to get to that point, and maybe back it off just a tad more…depending on what you/the car, like.
I have had the valve on my car for some 30 years now. Seems I never noted in my log book when I put it in, only reference the adjustments. So, with my master being the 15/16, the BMW 2002 4 piston steel calipers on the rear, and the front being the Brakeman 4 piston calipers, this is what I do with my brakes, via the proportioning valve. I am not going to get into the bore sizes, etc, as that is a discussion unto it’s self, and best left to those with good math skills, and able to build a balanced system, just using bore size matching alone, which still would not give you the ADJUSTABILITY, should you want it.
In the case of my ride, I can adjust from the extreme of having severe rear lockup, to NO lockup at all, barring actually locking the whole system up, which I have never done. In my slaloming experience, one learns to be very smooth, and able to take the tires to incipient lockup, but no more.
For driving on the street, which primarily means we have cold pads and rotors when we get onto the brakes, I have it set so that the front is doing most of the work. I have it set this way, should I have to really hit the brakes when cold, I will not get any rear lockup, and possibly cause me to want to come around. That being said, I have just enough rear bias, that when I enter a corner very fast, and I like to use trailing brake, the rear JUST feels like it is at the point of locking, and helps the car turn in a tad.
When I would road race, with sticky race slicks, I did not want the front doing most of the work, for all the reasons. I had more grip on the rear, so why put more heat into the front pads and rotors, at a disproportionate rate, by having HUGE weight transfer to the front. I would screw the knob IN, thus ALLOWING more pressure to the rear ( again, you must read the Tilton link, as it explains about the pressure!!!!). This would decrease the weight transfer, and make the rear work harder, which the car could tolerate. Now, there are a lot of factors going on here, main one being temperature. It took me a while to figure out the optimum amount to change to knob, as it took awhile for the pads/rotors to get to their equilibrium…KINDA. Obviously you keep introducing more heat, if you have undersized rotors, and or poor cooling, which can start to change things too. Balance..pun intended….becomes just a case of both testing, and knowing your car and driving style.
I had a problem to deal with also…pad choice. I could NOT get the same compound, from the same manufacturer. This gave a problem of have a relatively grippier pad at the front, which both caused the weight transfer to happen, and the lightly loaded rear to be not doing much. In my case , the difference in the coefficient of friction from front to rear, made for some interesting braking situations. Having the ability to fine tune things with the valve was a bonus, let alone a necessity for good PREDICTABLE braking.
And, what fuel load do you have? More weight over the rear, you can get away with more rear bias. This is really only a factor in a road race setting, where you are getting lighter in the rear, and want to back off the rear bias. That is where the TILTON LEVER type is likely better, you have 7 click stops.
As the so called DOT street legal race rubber has come along, the better grip has let me run with a bit more rear bias, and, this summer I am going to try dialing some more in. I will be the first to admit I am just not a hero when it comes to an over steering car. I have been very conservative about how much rear bias I have. I can really haul down INTO a corner, and as I have harped about before in regards to rear toe change, be able to get HARD on the brakes if I have to, and not worry about it either locking, or trying come around under heavy braking.
So, do you NEED a proportion valve…depends! Read the above again. Coming from my racing back ground, and a car(s) that were ALWAYS evolving, ever changing tires and grip……I NEEDED ONE..PERIOD!
I have done so many types of events’, it was the only way to both stay competitive, and safe. I had drum brakes originally, and when I changed to the “green stuff” shoes, things started to go to hell, in terms of brake balance.
We also now, and have for years, put on a hodge podge of different components, to do with the brake system, none of which were ever designed to be compatible.
My brake system uses all the stock line plumbing, except steel braided lines for the front and rear calipers. My shuttle valve is intact, as is the “brass” T at the fire wall.
So, botttom line for me, is that I have a complete range of adjustment for my brake balance, letting me maximize
my decelerations, at a hell of a rate!!