Mitchell wrote:
Swank Force One wrote:
It's way better when you just top off the fluid, then forget you did so when you do the brake job later.
Brake fluid takes paint off QUICK.
Should I siphon old fluid out to the minimum line before replacing pads and rotors?
my method (with the CRX … track days, TT, and a-x) so I end up changing pads fairly often
after removing the old pads, I open the bleed screw and then push the piston back. this gets the old, used, over heated fluid out. I then either continue letting that corner bleed itself (called gravity bleed), or close the bleed screw and top off the MC … then go to the next caliper … wash, rinse, repeat
Rotors need mass for heat absorbability.
Machining removes some of that mass.
I'll have the rotors turned for street use … for the TT car, I just replace them … for the reason Iceracer states
Swank Force One wrote:
It's way better when you just top off the fluid, then forget you did so when you do the brake job later.
Brake fluid takes paint off QUICK.
Had that done to me before, on a suburban. lots of extra brake fluid running all over the ground
I have had worn pads give a low pedal, it seems to have something to do with caliper design, the two piston Girlings on the Jensen did it. Whatever.
I did pad slaps on the Trooper twice, used a set of OE pads the first time and Akebono ceramics the second time, nary a peep from the brakes. FWIW, the Akebonos don't dust but they don't last as long as semi metallics and are NOT a good track day pad, they will fade under hard use. They are fine for normal street use though.
If the pads are worn and the fluid is low typically the engineers have determined what volume of fluid will go from the m/c to the caliper for new pads vs worn and this is the 'low fluid' point. On a lot of cars not only is this the lower level mark but it's also when the low fluid light will come on telling you it's time to have the brakes checked. It's also why it's not a real good idea to add brake fluid, this defeats the purpose of the low fluid light.
Now, if the pads are still in reasonable shape but the level has dropped, the fluid had to go somewhere and the one weirdo place is out of the back of the master cylinder and into the booster. I would remove the nuts holding the m/c, pull it forward and feel for brake fluid at the rear of it. Find fluid = replace the m/c and the booster (fluid can cause problems inside the booster).
Kenny_McCormic wrote:
Most rotors these days start out so thin machining them will put them near the wear limit anyhow.
True! The last couple of times I took rotors to have them turned they measured the thickness and said there wasn't enough material left to resurface the originals. Re-surfacing was the norm back in the Pleistocene era.
I am guilty of doing pad slaps if the rotors are clean and there is no complaint of pulsation or shudder. We were actually taught that the surface on a un-warped used rotor is more perfect mating surface than a turned rotor.
I went to a seminar put on by Performance Friction where they said pad break in was the process of transferring a microscopic layer of friction material from the pad to the rotor, once that happened you got max stopping torque. They also said that brake pulsation and vibration was due to that same pad material transfer and the best overall solution was to whizz wheel the rotors, install the new pads, then brake hard 4 or 5 times to effect the material transfer. Typically resurfacing wasn't needed and took too much meat off the rotor.
It's also a fact that two surfaces lapped together creates the best grip between those surfaces when they are clamped together. That is why Renthal dirt bike handlebars are not knurled; the top mechanics will use a little lapping compound on the bar clamps then work the bars back and forth, thus lapping the bars to the clamps, clean the compound off then torque the bolts. On brakes it's the same thing, the rotor finish will lap the pads to the rotors.
