::.. How are these Rotors?

[Alexlind123]

My mother's dodge durango had a problem with cracking rotors, probably because the terrain is fairly mountainous for a bit with some steep grades to heat brakes up. Finally my dad ordered some crossdrilled rotors that are gold in color (powerstop comes to mind, but im not sure). The crossdrilled rotors are far, far better and have already payed for themselves twice over in the price of new factory rotors. Whether this is due to better rotor material or the actual crossdrilling, i do not know.

[DanDombrowski]

Bill,

You're right about the drilling to help relieve the layer of gas that develops, that was another reason for putting the holes through.

As far as the heat capacity of the material, yes, you lose some. However, I've done enough engineering analyses to know that the amount of material you lose by drilling is probably neglidgable.

I was referring to the increased convection of having the holes through the disc. How much more? I have no idea, but as I understood it, that was the reason for claiming less brake fade.

Ideally, you would want more of the energy in braking to go into the air through convection than into the rotor's heat capacity (becasue all of that energy will have to be either convected out anyway or conduct into the caliper and brake lines), but without heat capacity, the same energy results in higher temperatures of the disc and caliper, and you're right back where you started from.

A question a lot of people ask about these is "If they're no good, then why does Porsche put them on their cars?"

I think the reason is that Porsche has done the real engineering thermal analysis to show that the pros outweigh the cons, at least with the rotors that they put on their cars. Weather or not Zimmerman or any other company has done the same analysis or is just banking on the bling factor, I don't know, and probably won't ever be allowed to find out. But for the price difference and the fact that labor is free, I thought I would give them a try. So far they seem the same to me.

[Springfield1952]

Am I missing something here? Aside from the discussion on the merits of cross drilled vs. solid rotors, the eBay auction is for Zimmerman rotors at $150/pair Buy it Now price while BMA has Zimmerman's for $127.50/pair. Why spend the extra $22.50?

Curt.

[DanDombrowski]

Yeah, no reason. I got mine from BMA too, they were only slightly more expensive than blanks.

[granit_silber]

In a recent issue of Roundel Steve Dinan is quoted saying that they have tests that show slotted rotors work better (less stopping distance) than drilled or slotted and drilled rotors.

Besides craked rotors and worn pads, you lose a lot more braking area with holes vs. slots.

Drilled rotors work on race cars because they only have to last one race before being replaced. On street cars I think they're stupid. But hey, to each their own. For my car I'm going with the ATE rotors with the elliptical slots (more so for the wear indication than the bling)
-ashley

[Qube]

Am I missing something here? Aside from the discussion on the merits of cross drilled vs. solid rotors, the eBay auction is for Zimmerman rotors at $150/pair Buy it Now price while BMA has Zimmerman's for $127.50/pair. Why spend the extra $22.50?

Curt.

Yep. You are missing my point in the first post. I'm getting them legit for $200 front AND back.

[Visions]

Slotted rotors slice the brake pads each time so you are always driving on clean pads... Drilled does the same but less...

[sKilled]

Thanks for the info - I just switched to stock replacements. Brembo front and Bradi rears.