wstar's Journal

wstar

Just got done with my big weekend of brakes work:

1) Put the Relentless 2-piece rotors on all 4 corners (along with their rear caliper expansion kit for the thicker rear rotors, which means taking the rear rotors completely apart and introducing lots of air into the system in the process).

2) A very thorough bleed of all the fluid: ran 2L of cheap Prestone stuff from autozone through just to clean out air bubbles and old fluid/moisture, around the 4 corners 2x over. Then flushed that with fresh RBF600 to past the obvious color change at all 4 corners.

3) Installed Carbotech XP8 pads all around.

4) Bedded it all in together.

The Carbotechs seem to bed in fine, and no real noise so far, so I may just keep using them as street pads, at least until they start getting noisy on me.

The Relentless kit seem to function fine so far. Both the rotors and the caliper expansion kit seem quite high quality. The rears are considerably thicker than stock, and at all 4 corners it's obvious they've got a better cooling vane setup in the interior (that and they're slotted to boot).

The only technical gripe I have is about the weights. The fronts are as advertised and talked about elsewhere on the board: ~19lbs per rotor, vs 29lbs for the stock ones I took off, so there's 20 lbs of unsprung rotating weight gone from the front of the car.

However, at least in my personal case, the "lightweight" 2-piece rear rotors are actually heavier than the stock ones I took off, by 1.8lbs per rotor. I checked and double-checked and triple-checked. Relentless claims roughly 3-4 lbs lighter on the rear rotors, and other installers seem to have confirmed this. Scott@RA claims I'm the first person to report having lighter stock rotors than his 2-piece ones. It's not an insignificant difference though, or just some minor measurement error. "3-4 lbs lighter" vs 1.8 lbs heavier is a net of ~5-6 lbs difference from expectations, which is in the ballpark of ~25% of the weight of the objects we're talking about. I repeatedly measured both of my RA ones and both of my stockers. The stockers are 19.2 lbs each, and the RA's are 21 lbs flat. It's hard to imagine some Nissan variance (as in, maybe on some 2009 cars they sourced different rear sport-package rotor part numbers) accounting for such a large weight discrepancy.

I'll have to check and see if anyone else kept the actual weight numbers from their stock and RA rear rotors for comparison sometime to delve deeper into this mystery.

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