2009 Nissan GT-R: Brake and Tire Walkaround Supplement
June 08, 2009
The 2009 Nissan GT-R suspension walkaround started to get long and drawn-out, so I decided to break it up. I took way too many photos for a single post.
Let's spend a bit more time on the brakes and tires.
Just look at those rotors! The ventilated air passages are big enough to put your fingers in. Don't, however, unless you want them severely burnt or chopped-off. Suffice it to say that air has no trouble finding its way through there.
Instead of being hidden on the back side, the GT-R's caliper mounting bolts (green) are easily accessed. Six-piston front-loading calipers have a very long pad slot, which would make them prone to flex and reduce their efficinecy if nothing was done about it. But here something has been done, in the form of two bridge bolts (yellow) that hold the center of the caliper together and make sure the clamping force goes to the rotor, where it belongs. Of course the bridge bolts have to be removed (as well as the usual pair of pins) in order to get the pads out.
Those with sharp eyes will notice that our pads still have some meat left, but they are getting thin. You might see a pad-change DIY post in a few weeks.
Another interesting tidbit is the external crossover pipe (white) that brings fluid from the inner half to the outer half. Sometimes internal passages are cast in the caliper body for this purpose, but these are cast solid for increased strength. This pipe should never need to be removed over the life of the car.
No internal passages also means twin brake bleed fittings (white). That's right, each half of this caliper needs to be bled seperately. You might also notice that these fittings screw into the same machined bungs as the crossover pipe in the last picture, making it look like left- and right-handed calipers are a simple matter of where they put the crossover pipe and the bleeders...
But that's not the case. Six-piston calipers almost always have a leading pair of pistons (white) that are slightly smaller in diameter than the middle and trailing pairs (yellow). It has to do with making sure the clamping forces are balanced across the entire pad, and the trailing end has to work harder.
So these caliper castings are, in fact, left and right-handed. Instead, the symmetrical bleed and crossover port machining simply makes life easier for the machinist.
The rear brakes also have an external crossover pipe and dual bleeders. Those who bleed their own brakes will have to go through the motions 8 times instead of the usual 4 times, and that means you're going to need to be real nice to the buddy you recruit to push the pedal for you.
Here you can see the clips that hold the ventilated and drilled rotors to the aluminum "hat". The clips allow a little lateral movement, which means the rotors will run true and will be less apt to create vibration when clamped by the caliper.
You'll also notice that this caliper has no bridge bolts spanning the pad slot, and that's because a 4-piston caliper's pad slot isn't long enough to create excess caliper flex.
This would be a healthy rear tire size for a lot of cars. On the GT-R, it's a front tire. The rear tires are 285/35ZRF20 100Y.
Surprise! The GT-R's Bridgestone RE070R assymetrical run-flat ultra-high performance tires are not long-wearing tires. Who knew?
The last 4 digits of the DOT number are the date code; 1308 in this case. That means these tires were manufactured during the 13th week of 2008. That's probably the last week of March. Maybe even April Fool's Day.
The GT-R's front wheels would also do the ass-end of any hot-rod proud: 20 by 9.5 inches. 45 mm is the offset, incidentally. The rear wheels are 20 by 10.5 inches with a 25 mm offset.
The front tire and wheel assemblies weigh 63 pounds. The rears weigh 67 pounds. That's the downside of rolling on dubs. While it's still a lot of unsprung mass to deal with, it makes more sense on a car like the GT-R. No one expects it to ride gracefully, so they can crank down the damping and use stiff springs.
Putting 20's on a luxury car, however, puts you deep in your own end zone. Makes those 20's run-flats, and you've really dug yourself a hole.
Finally, a word about tire-black detailing treatments: Don't. Just, don't.
Dan Edmunds, Director of Vehicle Testing @ 21,650 miles