I see a lot of new motorcycles with rotors that are super skinny and drilled out to the max, leaving little actual metal for the pad to come in contact with. Seeing that these machines run in the triple digits all the time and need to brake quickly in many cases, I assume weight has a large factor in the ability of the rotor to maintain its form and not crack under stress? That would be a main difference in braking against a car and a few buddies with bikes have no problem braking from 160+ when needed on their drilled out rotors. Maybe this is why some cars that see a lot of abuse to the brakes can get away with drilled/slotted, etc and not have serious deforming issues?
How much does lightening up the rotational weight on the car help rotors last, not deform, etc compared to dead weight?

 

Substantially less energy is needed to stop a 400lb bike than a 4,000lb car. Also, bike rotors are made from stainless steel not iron. It's not deforming under heat that is the issue, it's cracking from thermal shock. Any casting that is heat/cooled too quickly with crack. ie ice cube in coffee = pop!

Dropping rotating mass doesn't prevent deformation and it isn't intended to. The main advantage to lowered rotating mass is better handling, road feel, steering response etc. Drilling a rotor has a very negligible impact on reducing mass. The advent of carbon ceramic rotors has made it possible to use truly massive rotors without much of a weight penalty.

 

I think repeated 160+ runs on the freeway qualifies as "nascaring"

A proper bed in would be 1k miles, not 20. At 20 miles the friction surface crosshatching is still visible. An exploding rotor at 160 would have me more concerned with my life than my wheels, especially on a public freeway.

 

I would think at 160 on regular highways with street radials, braking hard enough to destroy your rotor would be pretty damn hard. Wouldn't the tire lose traction long before that and the car either go into abs mode or slide around on a layer of molten rubber?

 

It would not be hard at all, especially if you have plenty of horsepower on tap. Energy goes up with the square of velocity, meaning that the energy being absorbed by the brake rotors at 160mph is 4 times that generated from braking at 80mph (actually a bit more than that, as there is rotational energy also involved). Since braking would be at around 80-90% of what the tires can do as far as traction goes, they won't be a problem. They will cool off pretty quickly during the acceleration runs, but the brake won't cool nearly as fast and will be at much higher temperatures. ABS is also a non-factor for this type of test.

Essentially, the OE brakes stand no chance whatsoever. There is a reason why racing brake systems exist and cost so damn much.

Chris

 

Maybe they got too hot, I don't know. These did have a curved vane core (directional rotors,) and I only did 3 stops at high speed.. The cracks, I noticed when I was inspecting my front end for any hardware that might be coming loose.

I wasnt concerned about the wheels, just their ability to hold tires/air It cant possibly take 1000 miles to bed in brakes.. The wilwood brakes that we used in the trophy truck business were good to go with standard bed-in (I got rotors to operating temp by lightly using them for a few stops, then some 60-5 braking runs until they fade, then driving without using the brakes for 10 minutes or so.. they were a nice blue color after bed-in..)

 

It can take up to 1000 miles and at a minimum several hundred. Professional race teams spend a lot of money for pre-bedded brake sets for just that reason.

 

Learn something new every day

 

Did you come to full stops all in one shot from high speeds?

I've gone up to 130 on stock brakes and stopped just fine...i like to give it a pause in between pumps but it stops.

I agree tho those holes in the pics dont look like the proper finish.

I'm certain the car is not meant for nascar'ing....but it's also not going to dissassemble during a high speed blast or shatter the rotors. We'd see a lot more Fbody deaths if that was the case I am sure.

I think I may just stick with blanks for now. But do appreciate the science and knowledge shared.

 

So since we are learning so much about drilled rotors, and that Brembos may or may not be quality anymore, which drilled rotors are actually made correctly?

Additionally, if we aren't recommending drilled rotors for track use why would I want to "upgrade" my street car with them unless it is purely an aesthetic choice? If it is for more initial bite, maybe I should stick with a good blank and find a different pad.

While I am not going to dispute that surface area isn't in the classic physics friction equation, I am not familiar enough with pad adhesion or more realistic models of brake pad friction to know if surface area has absolutely no effect on stopping force. Perhaps it is less than brake pad chamfer, but it exists. I suppose it could be small enough to be insignificant, again being ignorant of a good model I wouldn't be able to say that with any authority.

I am a bit more interested in claims about cooling with a drilled vented disk versus a blank vented disk. What is the relationship between the air in the holes and the air in the vents? Is there actually flow through the holes and if so how does it effect the air flow through the vents. This point is continually argued on the forums...

Lastly I think the j-slots are neat. Too bad I don't think there are any good affordable ones to put on my car (at least there weren't the last time I looked). Really just an opinion on them, not so much a point for discussion.

 

The ones from Stillen are drilled correctly. They've been doing machined rotors for over 20 years and have got the processes down. There may be others, but not that I've personally seen.

Drilled (or other face pattern choices) are great for the street as they provide more initial bite as well as some other benefits (better wet braking, etc.). For heavy track use, the options are more limited. But on the street, you get the advantages without having to worry about premature cracking. The only downside is slightly faster pad wear, depending on how hard you use the brakes. Regardless, I know I'll never go back. One higher speed panic stop and you'd be hooked, too. I was cut off tonight on the way home (by a highway patrol car!) and felt the pads bite into the drilled rotors. My dog was NOT a happy camper...

Again, surface area by itself has no effect on brake torque -- until the pad is overheated. Too small of a surface area will overheat pads more quickly, so that is when it comes into play. But if you do 60 to 0 mph panic braking tests with various pad shapes, you find that the surface area has no bearing on a one-time stop. Chamfering pads is done to reduce noise complaints, Slotting pads is done to increase initial bite (by adding more leading edges).

Claims of a huge cooling benefit are misplaced. There have been cooling effects observed during testing, but that only showed up at elevated track temperatures, not a condition normally found on the street. In the typical street temperature range (100 - 600°F), virtually no cooling was observed. But, really, cooling under street use is not the #1 concern when looking to improve braking performance.

Talk to Stillen about J-Hooks. They have only done a few models, but would likely do more if there were a demand. They are only a bit more than drilled rotors, mostly because they spend a lot more time on the machine to complete.

Chris

 

Well not to belabor any points or beat a dead horse...

I can understand that there may be a couple benefits to a drilled rotor. But all in all I can't say that I have ever been a huge fan of them. Reason being that it seems to me that if you were on a budget, a quality blank is still cheaper and you could apply the extra money to a better pad which could also potentially provide better bite, and also more torque or fade resistance or whatever parameter you wanted to improve if you pick the right one. (Not to mention lines or fluid which are also key).

If you are interested in keeping debris or water out from in between the pad / rotor, or you want more initial bite then why not just get a properly slotted rotor? Seems that you would have the benefits with less likelihood of cracking if you decided to track the car.

I will admit that occasionally I will get the initial "no brakes" feeling if I hit a huge puddle that would probably be avoided with drilled or slotted rotors. But all in all I can't say that I have been compelled to switch when you factor everything together: price, durability, pad life, etc.

But since this has probably been one of the better threads on a board concerning rotors, why not try to learn something (as is the primary function of a tech related forum) and ask some questions for a good discussion. Partly why I brought up surface area, as if you look the simple friction formula is the friction equals the coefficient of friction times the normal force; however that equation isn't an exact model, especially if you look at something complicated like tires on pavement. If it were then the length of the contact patch in the direction of the velocity or even tread pattern would be irrelevant, and it clearly is not. That is in a large part due to adhesion between the rubber and pavement and shearing. This occurs somewhat with brake pads and the rotor (and why pad material sticks to the rotor), although apparently friction is typically the predominant force in braking torque with most pad materials.

If Stillen or someone else would make j-hooks for the Fbody I think my inner ricer would be too strong and force me to get them though

 

This discussion has kind of veered off into a debate on different types of rotors, but I'm looking for the same info as the original post. It seems to be hard to find many blank rotors that are available right now. Does anybody have any recommendations? I'm having trouble finding Brembo blanks in stock anywhere and I'd rather not get slotted or drilled rotors. Any other brands people have had good experience with?

Thanks

 

I had to wait and pay extra....but I did well with Wagners from Advance Auto.

They are USA build. And are super thick...so much so that it will push your rear wheels out some becuz they are much thicker in the middle section that couples to the oem spindle/hub vs. the stock rotor. They will push out rear wheels maybe an additional 5-8mm! in my opinion you can see a huge difference in craftsmanship and finish. I was impressed nevermind all the hoopla about super expensive rotors and kooky pros and cons of holes and such.

I'd be willing to try J hooks as well. But im not paying no damm 5 grand for 'em. I can Jhook a lot of other things w/5 g'z.

If you really want brembo's have you checked Summit Racing? and or Ebay?

 

http://www.summitracing.com/parts/XYZ-BRE27249/

A little pricey but they have them in stock. They were on sale for $50 a rotor a few months ago, I snatched up a pair even though I don't need rotors and won't for a while lol. For that price though, I would probably go with a set of powerslot rotors slotted only rotors since they are a bit cheaper.

 

I imagine the most important thing for a blank is the metallurgy. The one problem is keeping track of where the rotor production gets moved around. Used to be that Brembo or Duralast were the auto-recommended blank in this forum. I don't think at this time the Brembos actually warrant their price.

At any rate, I had a set of Duralast rotors that worked well for the years that I had them. But looking at Autozone's website, I thought they used to have a longer warranty than the 2yr it says they have now but I am probably misremembering. I didn't need the warranty anyway. I can't speak to the Valucraft rotors, but they supposedly use cheaper steel (which is why they are cheaper).

Strano sells "Best Brakes" blanks for $49fr, $52r...

Tirerack carries Centric blanks, but I haven't used them. Maybe someone else has and can chime in.

I imagine the other autoparts house brands might be ok but I haven't run them. You might want to shop by warranty terms...

 

Centric blanks are top notch..

 

Thanks for the feedback guys. I agree, seems like Brembo is a bit overpriced for what they are, I'm keeping my options open at the moment.

 

We've got autospecialty blanks front and rear rotors for $120.00 shipped. They are quality OE replacements at a price better than napa or autozone.