Contemplating big brake kit

[nightfire]

I forgot about this thread... Well, I ended up ordering them and good god they're huge:



I couldn't believe just how substantial they were when I picked them up. In fact all that extra weight is not good. I'll have to order some two-piece rotors in the future.

Can't wait to install them.

[marcdh]

HOLY SHAT! they're the size of the moon! What weight are they? At least the calipers light... Got lightweight rims?

[onlytrueromeo]

These the ebay ones I linked to? Have you checked to see if they fit your rims? I love how they look, but I don't want to run 17's to fit the brakes

[nightfire]

The rotors weigh in at a beastly 21lbs each.

The calipers are about 5lbs lighter than stock, and my mags are 11.5lbs each, so all in it should weigh close to stock. Unfortunately my mags are too small (16x7) so I need to use 15mm spacers, adding another 3lbs per wheel.

Just can't win.

I did get them from some guy on ebay but I'm not sure if it's the same kit. I tested with the cardboard profile and they definitely won't fit as is. If I can't stuff them under even with spacers I'll have to go 17's, though that's not a bad thing since I want wider wheels anyway. I'd like to be running 17x8's with 245s all around.

In fact I put my wheels up in the FS section already.

[Mooneggs]

I don't like the fact they drilled the holes over the 5 hole pattern... won't that affect the integrity of that 4th hole? especially with them being that much heavier...

[nightfire]

I don't like the fact they drilled the holes over the 5 hole pattern... won't that affect the integrity of that 4th hole? especially with them being that much heavier...

Ah the rotors are crap. They were practically freebies thrown in so you could install the kit; they're heavy, not plated/anodized/painted, 1-piece. I bet they cost $50 each at most.

But that hole pattern shouldn't compromise anything. The bolts are only really used for holding the wheel against the hub. Most of the tortional force should be from the hub plate against the brake, and from the brake against the wheel center. The studs would shear off if they had to take the full force of heavy braking or even acceleration. I think, anyway.

[wytbishop]

The bolts are in direct shear all the time. That shear force is reduced by the friction between the wheel and the face of the rotor. If the wheel studs are not properly torqued, there is less friction between those surfaces and wheel studs can be sheared. It happens often on big rigs because of their huge loaded weights. But for a car, the problem is loose or missing wheel nuts. If the wheel can move on the stud it creates bending in the stud...snap!

The shear strength of a 5/8" grade 8 stud is ~27,000lbs min. That means your cars weight is supported in shear by 16x27,000lbs shear capacity.

For perspective...If you bolted 2 steel plates together with 16, 5/8" grade 8 bolts, you could hang 432,000lbs from it.

So if your car achieves 180 G's during either acceleration or deceleration you're in big trouble.

[nightfire]

The bolts are in direct shear all the time. That shear force is reduced by the friction between the wheel and the face of the rotor. If the wheel studs are not properly torqued, there is less friction between those surfaces and wheel studs can be sheared. It happens often on big rigs because of their huge loaded weights. But for a car, the problem is loose or missing wheel nuts. If the wheel can move on the stud it creates bending in the stud...snap!

The shear strength of a 5/8" grade 8 stud is ~27,000lbs min. That means your cars weight is supported in shear by 16x27,000lbs shear capacity.

For perspective...If you bolted 2 steel plates together with 16, 5/8" grade 8 bolts, you could hang 432,000lbs from it.

So if your car achieves 180 G's during either acceleration or deceleration you're in big trouble.

I knew wytbishop would be back in short order.

Ok, so basically even if the one stud didn't experience its share of equally distributed shearing force, the other 3 are one or two orders of magnitude more than enough.

[wytbishop]

It's way overkill.

the thing to consider with wheel installation in general is clamping force. What happens a lot is that people paint their rotors. Then, they torque their wheels down and think everything is good...but it's not. The paint is compressed by the clamping force and crushed. Over time it becomes thinner and the clamping load is lost.

Don't paint your rotors.

[nightfire]

Good point.

[Ryan]

Paint them, but not any part that will be bolted against another surface... why would you anyway, right? Can't see it. Save your paint!