i have acess to a set of calipers that i belive that came off of and ls400 or 430. the front are dual pistons and the rear are singlei figured that sense the car is so big then it would have to have more claping force then the stock mk3 calipers.
bbk do or don't ??
- Thread starter supramic
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Not necesserially, clamping force is only part of the over all picture. Brake torque is what you are really after.
The caliper alone does not determine the clamping force. The mastercylinder bore size, brake booster diameter, and peddle ratio all play rolls along with the caliper in generating the clamping pressure.
The caliper alone does not determine the clamping force. The mastercylinder bore size, brake booster diameter, and peddle ratio all play rolls along with the caliper in generating the clamping pressure.
i lost, why dont i hear people switchiing mas/boosters when the go with mk4 calipers
i use to have a dsm and when i when with the 3000gt calipers i had to get the mas cylinder, booster to complet the swap
has any one done this for our cars and is it worth it
i use to have a dsm and when i when with the 3000gt calipers i had to get the mas cylinder, booster to complet the swap
has any one done this for our cars and is it worth it
I haven't really looked into the hole MKIV parts swap stuff. So I am not really sure. Swaping the lexus stuff will most likely be somewhat of a bennifit, but not worth the hasal. The lexus part that you are talking about are basically the same as the MKIV N/A brakes. Now chances are, swapping the other components would infact make the system better but mostly from a feel standpoint if they are infact different.
I probably should have went into more detail in my last post then what I did. The clamping force is like I said only part of the picture, where as the braking torque are thermal management are actually what your are really after when upgrading the brakes and more importantly the thermal management part , but even then its really the tires that stop the car in the end. So you can have the best brakes money can buy and still not have the car stop worth a damn.
Clamping force is not constant. The harder you press on the peddle, the more clamping force that is generated at the calipers. The reason for increasing the clamping force of the calipes (increasing piston area) is so that it takes less peddle effort to equal the same clamping force.
Heres an example to help make this more understandable incase its not. I'll leave out the booster cause it will vary depending on the engine vacuum. By doing this though, the clamp force numbers will be somewhat lower for the given peddle effort. (assume that it is an older car with manual brakes not power brakes)
Let say that the car has a
Peddle ratio of 7:1
Mastercylinder piston area of .441 sq in (.75" bore size)
caliper piston area of 4.43 sq in (2.375 piston diameter)
driver exerts 50lbs of force on the peddle
peddle pressure X peddle ratio = inlet pressure on mastercylinder or
50 X 7 = 350lbs of force going into the mastercylinder
mastercylinder inlet pressure / mastercylinder piston area = mastercylinder outlet pressure
350 / .441 = 154.35 psi mastercylinder outlet pressure
mastercylinder outlet pressure X caliper piston area = caliper clamping force
154.35 X 4.43 = 683.77psi caliper clamping force
Now lets change the caliper to one that has a 2.5" bore (4.91 sq in) so reworking the number you come up with 757.86psi of clamping force and this will make the car stop faster cause the brake torque will increase but will also make it easier to lock the wheels up for the same peddle effort or requier less effort then originally needed to stop the car the same as it did with the original setup.
The negitive side besides locking up the wheels easier is that as the piston area increases, more fluid volume is requiered or you will get a spongier peddle and longer stoke peddle. The only way to increase fluid volume is to go to a larger bore mastercylinder but as the mastercylinder bore increases, its output pressure decreases and therefore requiering you to step on the peddle harder to equal the same outlet pressure.
Increasing the rotor diameter and or the brake pad friction coeffficient will increase the brake torque also like increasing the clamping force but without the negitives except for the easier wheel lookup.
Overall, the stock MKIII brakes are not that bad. The design problem with them is the rotors are to thin and therefore thermal managenment issues can arise especially being that our cars are very heavy. If you have a issue with warping rotors badly, then you could bennifit from some form of BBK. Other then that, if you can lock the wheels up, the brakes are fine and better tires are what is needed more so. This all goes for normal daily street driving. Now if the car is used on a track or driven like on a track where you are constantly trying to slow the car down from very high rates of speed then YES a BBK would be needed. This is because for one, it is a lot harder to lookup the wheels at lets say 130mph then it is at say 50mph so more torque would be bennifical to slow the car down faster and second using the brakes in those conditions does gerenate a lot more heat so larger thicker rotors are needed to absorb and dissipate the higher amounts of heat generated by the brakes.
The reason that I say that you could possibly stand to bennifit from the the lexus parts is because the rotors are larger and thicker and therefore would absorb and dissipate more heat and probably cause a small increase in brake torque. Just because a caliper has more pistons does not mean that it generates more clamp force. As the piston number increase, the diameter decreases so the overall piston area usually changes very little. The main reason for multi piston calipers is to better distribute the clamp force over the length of the pad because the pad will flex as the length increases. Also one thing to note on multi piston calipers is that if you have a 2 piston with lets say 1.5" pistons (similar to the lexus ones) and a 4 piston caliper with the same 1.5" piston size (similar to the MKIV TT ones), there will be no differance in clamp force even though the one has 2 more pistons. Caliper piston area is figured for only one side and then multiplied by 2 because there are two pads and regardless of caliper design, the clamping force is the same on both pads or on each face of the rotor. This is why a caliper with piston(s) on only one side float over the rotor and apposed piston calipers (like the MKIV TT) are fixed location over the rotor.
Manufactures put a lot of effort into brake system design and one of the major design aspects is to make sure that you dont lock up the wheels to easialy at low speeds or typical road speeds. During this design aspect, a lot of factors are taken onto account like vechile weight, vechile dynamics like weight transfer and tire traction just to name a few.
I probably should have went into more detail in my last post then what I did. The clamping force is like I said only part of the picture, where as the braking torque are thermal management are actually what your are really after when upgrading the brakes and more importantly the thermal management part , but even then its really the tires that stop the car in the end. So you can have the best brakes money can buy and still not have the car stop worth a damn.
Clamping force is not constant. The harder you press on the peddle, the more clamping force that is generated at the calipers. The reason for increasing the clamping force of the calipes (increasing piston area) is so that it takes less peddle effort to equal the same clamping force.
Heres an example to help make this more understandable incase its not. I'll leave out the booster cause it will vary depending on the engine vacuum. By doing this though, the clamp force numbers will be somewhat lower for the given peddle effort. (assume that it is an older car with manual brakes not power brakes)
Let say that the car has a
Peddle ratio of 7:1
Mastercylinder piston area of .441 sq in (.75" bore size)
caliper piston area of 4.43 sq in (2.375 piston diameter)
driver exerts 50lbs of force on the peddle
peddle pressure X peddle ratio = inlet pressure on mastercylinder or
50 X 7 = 350lbs of force going into the mastercylinder
mastercylinder inlet pressure / mastercylinder piston area = mastercylinder outlet pressure
350 / .441 = 154.35 psi mastercylinder outlet pressure
mastercylinder outlet pressure X caliper piston area = caliper clamping force
154.35 X 4.43 = 683.77psi caliper clamping force
Now lets change the caliper to one that has a 2.5" bore (4.91 sq in) so reworking the number you come up with 757.86psi of clamping force and this will make the car stop faster cause the brake torque will increase but will also make it easier to lock the wheels up for the same peddle effort or requier less effort then originally needed to stop the car the same as it did with the original setup.
The negitive side besides locking up the wheels easier is that as the piston area increases, more fluid volume is requiered or you will get a spongier peddle and longer stoke peddle. The only way to increase fluid volume is to go to a larger bore mastercylinder but as the mastercylinder bore increases, its output pressure decreases and therefore requiering you to step on the peddle harder to equal the same outlet pressure.
Increasing the rotor diameter and or the brake pad friction coeffficient will increase the brake torque also like increasing the clamping force but without the negitives except for the easier wheel lookup.
Overall, the stock MKIII brakes are not that bad. The design problem with them is the rotors are to thin and therefore thermal managenment issues can arise especially being that our cars are very heavy. If you have a issue with warping rotors badly, then you could bennifit from some form of BBK. Other then that, if you can lock the wheels up, the brakes are fine and better tires are what is needed more so. This all goes for normal daily street driving. Now if the car is used on a track or driven like on a track where you are constantly trying to slow the car down from very high rates of speed then YES a BBK would be needed. This is because for one, it is a lot harder to lookup the wheels at lets say 130mph then it is at say 50mph so more torque would be bennifical to slow the car down faster and second using the brakes in those conditions does gerenate a lot more heat so larger thicker rotors are needed to absorb and dissipate the higher amounts of heat generated by the brakes.
The reason that I say that you could possibly stand to bennifit from the the lexus parts is because the rotors are larger and thicker and therefore would absorb and dissipate more heat and probably cause a small increase in brake torque. Just because a caliper has more pistons does not mean that it generates more clamp force. As the piston number increase, the diameter decreases so the overall piston area usually changes very little. The main reason for multi piston calipers is to better distribute the clamp force over the length of the pad because the pad will flex as the length increases. Also one thing to note on multi piston calipers is that if you have a 2 piston with lets say 1.5" pistons (similar to the lexus ones) and a 4 piston caliper with the same 1.5" piston size (similar to the MKIV TT ones), there will be no differance in clamp force even though the one has 2 more pistons. Caliper piston area is figured for only one side and then multiplied by 2 because there are two pads and regardless of caliper design, the clamping force is the same on both pads or on each face of the rotor. This is why a caliper with piston(s) on only one side float over the rotor and apposed piston calipers (like the MKIV TT) are fixed location over the rotor.
Manufactures put a lot of effort into brake system design and one of the major design aspects is to make sure that you dont lock up the wheels to easialy at low speeds or typical road speeds. During this design aspect, a lot of factors are taken onto account like vechile weight, vechile dynamics like weight transfer and tire traction just to name a few.
Damn Ian, a little late there? LOLIJ. said:Cliffs: BBK's are good!
but yes, BBK's are good (as long as they are designed correctly if not, then you are just shootingh yourself in the foot....)