545OH

My neighbor just bought a new G37S coupe and it has nice big 19 inch wheels and I noticed the rotors are quite large in overall diameter however the diameter of the inner circle is much larger than most, including the one's on the 545's. The actual width of the rotor though is quite skinny (the part the pads grab onto). This is hard to explain I am finding but basically the overall diameter is very big but the actual rotor material is quite thin and the middle center hole is bigger than normal making the overall piece appear larger in diameter. This is in comparison to most others, including bmw, where the inside circle is about the same size as the wheel hub. Question is when they advertise rotors it is in overall diameter ie. 14 inches. But how does that take into account actual rotor material. I would assume bmw rotors with less overlal diameter but more actual rotor disk width would be more effective then a huge diameter rotor with only a skinny piece of rotor disk and large middle space of nothing.?

andy535xi

British Touring Cars (and many other GT race cars) use the same system, except they use aluminum floating center cap. The Idea is to reduce centrifugal force (inirtia), yet at the same time, cool the rotor down ASAP. A bigger diameter rotor wil always have more surface area = cools down quicker. At the same time, if the rotor is very thin, heat cannot be dissipated fast enough and it warps from overheating. Case and point - go to an Audi dealership, and touch the front and rear rotor (to see how thick they are) on an S4 or RS4 and then touch a regular A4 ... very big difference.

545OH

I guess I was not clear in how I was explaining it. I was not meaning thin as in thickness of the rotor but rather a shorter diameter of the actual rotor material at any given point around the rotor (meaning not the diamater of the entire rotor). It may be a floating setup which makes sense however I do not see how that would help any. I wish I could use a picture. Maybe I will find one to show.

545OH

Here is two pictures, the first is a floating rotor and is what I was talking about when I said it was a larger diameter but no difference in actual rotor material diameter and the second is a normal looking one that is on our cars or most cars I see.

545OH

Ok I cannot get the other one posted but the one above is the one that is different than the stock 545 for example. Larger overall diameter but the 545 rotors have more "meat" since the actual rotor material is thicker.

545felix

I'm not sure I'm explaining this in the correct manner, but the further out from the centerline of the rotor the caliper is, the more force the rotor can apply. (think leverage on a wrench- you can certainly apply more force on a nut or bolt if you're using a longer wrench.) swept area is important as well, but both are factors in braking power.

there is a great site out there explaining all of this, I just can't find it on google right now.

525iEnjoy

hey Felix I remember seeing a comparison on Zeckhausens site between the 350z base vs 350Zbrembo vs Stoptech

545felix

not that one, but that did lead me to a Stoptech article that explains it on page 4 in far better wording.

Brake System design