94 q45t slotted rotors

[ahardb0dy]

pulled the tires off today to check the brakes and found that the front rotors are slotted, so I guess someone replaced them, will most shops cut slotted rotors or should I just get replacement ones? All the pads were good but the harder I apply the brakes I get like a vibration, not in the pedal but I can't tell if it's coming from the front or rear of the car, I did notice the drivers side rear rotor was a little wavy, so maybe that's causing the vibration?? Thanks

[maxnix]

Could be. If you have the OEM rear solid rotors, definitely true them on a lathe. Check for bearing/ball joint play while you are under there. A perfectionist (or a good technician chasing a problem) will measure hub run-out also and clean the mounting surfaces where hub and rotor hat meet.

[DrewQ45]

"will most shops cut slotted rotors or should I just get replacement ones"

Rotors are rotors, the lathe cares not.

[jamesmost]

"will most shops cut slotted rotors or should I just get replacement ones"

Rotors are rotors, the lathe cares not.

i had problems getting cross driled roters resurfacedsince that time i just replace them i no longer believe in re-surfacing.the warpage is deeper and resurface is only a temporary fix

[maxnix]

i had problems getting cross driled roters resurfacedsince that time i just replace them i no longer believe in re-surfacing.the warpage is deeper and resurface is only a temporary fix

This is true. When one resurfaces, one only achieves diminished returns as mass from the rotor is removed, so it will warp again in less time.

[Q45tech]

Everything is just a temporary fix ------replacement or trueing.

The insufficient mass, cast iron quality [plus formula selection to minimize rotor noise] and the integral hat [one piece design] are all going to contribute to exceeding the 0.0028" oem runout spec eventually.

Not aligning the rotor to <0.001" to begin with is the primary culprit, secondly the alignment of the calipers [are they perfectly centered [did they bend minutely......do they bend on application so that the pads are EXACTLY applied at the same moment and force......thru the various amounts of foot pedal pressure!

Slotted rotor tend to wear pads faster than drilled rotors which wear faster than plain rotors........leading edge of slot/holes etc.

Old brake systems are old and not new

[Q45tech]

Consider how little mass is removed from new to worn out as the machine surfaces only represent less than half the weight [hat and vanes the other half] so 2/9 of 50% is 11%..............a worn out rotor weighs 11% less than a new one of same type.......thus runs 11% Hotter [or gets hotter 11% faster] than a new one.

On the rear 1/9 of 60%~~6.66% mass loss.

Not significant, the reason one changes rotors is the caliper piston seal may not have enough flexibility with a worn out pad and rotor to retain the seal on the piston............the brake pads new are 9mm thick compared to a worn rotors loss of 1mm.............there is obviously some safety margin in the seal extension as we have seen pads worn into backing plate [no pad fricition material at all] and the backing plate was worn another 1.5 mm.

Which seems more critical a piston extension of 9-2 [7] x 2 =18-14mm for pads or another 1-2 mm piston extension due to rotor wear ?

[DrewQ45]

i had problems getting cross driled roters resurfacedsince that time i just replace them i no longer believe in re-surfacing.the warpage is deeper and resurface is only a temporary fix

Don't forget that slotted and cross drilled are supposed to dissipate heat faster by letting the hot gases escape at higher rates... This should resulting in better braking and less warpage - main reasons for buying them in the first place. If warpage is recurring may I suggested checking your driving habits, greasing your slide pins (sticky calipers?) and buying rims with large holes for improved airflow (see mine below).

I've always had good results from resurfacing OEM rotors but knew when it was time to change them (before exceeding minimum thickness). The rotor mass removed should be negligible as a good shop will only "skim" the surfaces...the usual culprit for higher removal will be those who let the brake pedal wear down to the point where the metal backing eats out a grove into the rotor surfaces resulting in deep resurfacing to remove said groove.

I currently have slotted and cross drilled with steel lines. Had them trued when brand new and it was not a problem finding a shop to do it.

Change cross drilled rotors on the regular? You must have some deep pockets man... I'm jealous.