Killer Deal on 300c and 300 Cross-drilled Slotted Rotors

[tracktone01]

I found this auction on Ebay earlier today. $299.99 for all four rotors for the 300 and $339.00 for all four for the 300c! Just wanted to know what you guys think: 300 and 300c Cross-Drilled Slotted Rotors

I emailed the seller and this is what he had to say:

Thank you for your interest in R1 Concepts. Sorry, but you did not specify if you had the 300 or 300c. Nonetheless, I will provide you with the price for both vehicles. We will offer you $299.99 for all four rotors for the 300 and $339.00 for all four for the 300c!

The rotors that you are inquiring about are cross-drilled and slotted. They are Electro-plated black on the hubs and inner vents to prevent the rotors from rusting.

These are premium quality rotors made from stronger casting than other rotors that are on the market. We can provide you with three different types of styles: drilled, slotted, or combination of both.

Please let me know what you guys think of this deal.

[DZeckhausen]

Originally Posted by tracktone01

I found this auction on Ebay earlier today. $299.99 for all four rotors for the 300 and $339.00 for all four for the 300c! Just wanted to know what you guys think: 300 and 300c Cross-Drilled Slotted Rotors

I emailed the seller and this is what he had to say:

Please let me know what you guys think of this deal.

Regardless of the price, you don't ever want to cross-drill AND slot a set of rotors. One or the other, but not both. All it does is weaken the rotor, without providing any additional benefit.

For a car which will never be taken to the track, cross-drilled rotors are fine. They give you improved bite, reduced delay of braking in wet conditions, and you save up to 1/4 pound per rotor over plain or slotted. For track use, you should go with slotted. Under race conditions, drilled rotors will crack sooner than plain or slotted rotors. Slotted give you virtually the same improvement in initial bite as drilled, without the propensity to crack under tough conditions.

Getting back to this vendor - you might want to ask him where these rotors are manufactured. I suspect they are cast in Mainland China or Taiwan. There are a handful of decent foundries in Asia, but most of them are boutique foundries with dirt floors, no process control, no adherence to standards of quality, and they crank out total junk. For example, I've seen casting flash completely block airflow through some cheap Asian rotors. If he says they are made at in ISO certified foundry in Asia, ask him the name of it. If it really is a quality foundry, he won't be afraid to identify it by name.

[tracktone01]

Thanks DZeckhausen! I'll email him right now and ask him those questions. Hopefully, he'll respond today. I'll let you know what he says.

[kidcoastal]

Originally Posted by DZeckhausen

Regardless of the price, you don't ever want to cross-drill AND slot a set of rotors. One or the other, but not both. All it does is weaken the rotor, without providing any additional benefit.

For a car which will never be taken to the track, cross-drilled rotors are fine. They give you improved bite, reduced delay of braking in wet conditions, and you save up to 1/4 pound per rotor over plain or slotted. For track use, you should go with slotted. Under race conditions, drilled rotors will crack sooner than plain or slotted rotors. Slotted give you virtually the same improvement in initial bite as drilled, without the propensity to crack under tough conditions.

Getting back to this vendor - you might want to ask him where these rotors are manufactured. I suspect they are cast in Mainland China or Taiwan. There are a handful of decent foundries in Asia, but most of them are boutique foundries with dirt floors, no process control, no adherence to standards of quality, and they crank out total junk. For example, I've seen casting flash completely block airflow through some cheap Asian rotors. If he says they are made at in ISO certified foundry in Asia, ask him the name of it. If it really is a quality foundry, he won't be afraid to identify it by name.

Great post Dave. I was wondering the same thing... which was better.

[todd tce]

I generally agree with Dave on that. But for the most part buyers WANT slotted and drilled rotors. If one is good, then both must be better....And thus most offer it as a combo finish because it's market demand. Not because one is better or worse.

I was looking at the rotor pic supplied....funny how it looks exactly like the same castings I have sitting on the shelf. Right down to the balance mill work and numbers on it. No way of knowing if what the guy sells you is a factory part modified but I'll wager $20 the ones in the pic are bone stock items.

More over I'd be very interested to hear from a buyer who has them in hand BEFORE you put them on the car I have a question about them. I'm not going to post it now to ask the vendor, but if you buy them let us know when and I'll take 10m of your time. Oh, we'll post the q&a here after too.

[DZeckhausen]

Originally Posted by todd tce

I was looking at the rotor pic supplied....funny how it looks exactly like the same castings I have sitting on the shelf. Right down to the balance mill work and numbers on it. No way of knowing if what the guy sells you is a factory part modified but I'll wager $20 the ones in the pic are bone stock items.

I would prefer a modified factory part to a cheap casting manufactured in a Mainland China boutique foundary with a dirt floor and chickens running around.

[shanemcse]

I just picked these up in person. I have them if anybody has any questions. They are very nice and from my point of view much better than others I saw on EBAY and the internet for the price. Others I saw only had 4 or 6 slots cut with 4 or 6 rows of holes. These have 8 lines and 8 rows of holes. I don't know a lot about rotors but I figure the more holes and lines cut the better. I live close by so I was able to go down and pick them up in person. The people I talked to on the phone and at the site were very helpful and the guy that helped me was a 300C owner himself.

[DZeckhausen]

Originally Posted by shanemcse

I just picked these up in person. I have them if anybody has any questions. They are very nice and from my point of view much better than others I saw on EBAY and the internet for the price. Others I saw only had 4 or 6 slots cut with 4 or 6 rows of holes. These have 8 lines and 8 rows of holes. I don't know a lot about rotors but I figure the more holes and lines cut the better. I live close by so I was able to go down and pick them up in person. The people I talked to on the phone and at the site were very helpful and the guy that helped me was a 300C owner himself.

You need to look back at Post #2 above or click on this link: Killer Deal on 300c and 300 Cross-drilled Slotted Rotors

Repeat after me: Rotors that have been slotted AND drilled are bad!

If a vendor is clueless enough to drill and slot rotors, then you can be reasonably certain they don't know the proper drilling or slotting patterns to apply to maximize the benefits while avoiding structural damage to the rotors. And no, more holes and slots is not better than fewer holes and slots! You want the hole pattern to be such that the entire surface of the pad is swept by them. To do this, you need the holes in adjacent rows to be staggered. You also need to space the holes appropriately, such that they don't cut into any internal cooling vanes. And you don't want the size of the holes to exceed 4mm in diameter.

Here's an example of drilled rotors done properly:



Note that the spiral "arms" of the drill pattern can run in the same direction or the opposite direction of the internal cooling vanes. It is critical for the spacing of holes to not hit or come too close to the internal vanes. You can see this in the cut-away photo above.

Slotted rotors should be cut in a direction opposite to the internal vanes so that each slot is supported by several vanes, which act as reinforcement. You should NEVER slot the rotor in the same direction as the internal vanes, since this dramatically weakens the rotor. Since the vanes should lean toward the back of the car at the top of the rotors, the slots should tilt forward in the opposite direction. The slots should never be machined all the way to the outside edge of the rotor. If they do, the rotor can crack under heavy use.

[4herb2tas0tik]

hey DZ thanks for the insight...i just learned something new..

[Goose]

On that note, where can we find a good set?

Originally Posted by DZeckhausen

You need to look back at Post #2 above or click on this link: Killer Deal on 300c and 300 Cross-drilled Slotted Rotors

Repeat after me: Rotors that have been slotted AND drilled are bad!

If a vendor is clueless enough to drill and slot rotors, then you can be reasonably certain they don't know the proper drilling or slotting patterns to apply to maximize the benefits while avoiding structural damage to the rotors. And no, more holes and slots is not better than fewer holes and slots! You want the hole pattern to be such that the entire surface of the pad is swept by them. To do this, you need the holes in adjacent rows to be staggered. You also need to space the holes appropriately, such that they don't cut into any internal cooling vanes. And you don't want the size of the holes to exceed 4mm in diameter.

Here's an example of drilled rotors done properly:



Note that the spiral "arms" of the drill pattern can run in the same direction or the opposite direction of the internal cooling vanes. It is critical for the spacing of holes to not hit or come too close to the internal vanes. You can see this in the cut-away photo above.

Slotted rotors should be cut in a direction opposite to the internal vanes so that each slot is supported by several vanes, which act as reinforcement. You should NEVER slot the rotor in the same direction as the internal vanes, since this dramatically weakens the rotor. Since the vanes should lean toward the back of the car at the top of the rotors, the slots should tilt forward in the opposite direction. The slots should never be machined all the way to the outside edge of the rotor. If they do, the rotor can crack under heavy use.