RK951

anyone have any experience or thoughts with these crossdrilled rotors or ones similar? Supposedly they are a direct replacement which allow you to use the factory calipers on the 951.

phils87951

Zimmerman rotors are good and used as Porsche OEM parts along with brembo Rotors.
the basic facts about cross drilled rotors is, you go get improved gas reliefe, they will crack from hole to hole ( cast with holes is slightly better but they will eventually crack) Once they crack to the outer edge they are considered finished.
They will give you faster braking in the wet. if you live in a very dry climate, get regular OEM parts, they work great
if you live in a very wet climate, sure go for it

If you figure on better braking performance, bahh not really, you are actually reducing the surface area available for the brake pads.
for looks , go for it, they look awsome

Be sure to sand or remove the zink coating on them prior to use as ut can gum up the pad material. or use a worn out set of pads for a few hundred miles to get rid of the coating.

eniac

The idea that they give you better braking comes from better cooling, eventhough there is less surface area. Brakes work better when they are not overheated. I've had Zimmerman cross drilled rotors on my car for 4 years. No problems yet and my '44 brakes better then any I have driven with stock brakes.

Crazy Eddie

7up or others ....
I will needing those pretty soon
Where and what is the price of those ?
I believe I had seen them at 165 give or take 10 bucks a few weeks back
on one of the parts vendors
Regards
Ed

RK951

the picture above is from an ebay auction. if you click on the word crossdrilled rotors in my initial post it will take you there. there are many people that sell them including lindsey racing. i've read many of the old threads and i don't expect any improvement in performance but i don't like the idea of a cracked or warped rotor. it would be nice to hear from people that have tried them whether its been a good or bad experience.

Crazy Eddie

7up the picture above is from an ebay auction. if you click on the word crossdrilled rotors in my initial post it will take you there. there are many people that sell them including lindsey racing. i've read many of the old threads and i don't expect any improvement in performance but i don't like the idea of a cracked or warped rotor. it would be nice to hear from people that have tried them whether its been a good or bad experience.
This topic has been debated back and forth ...
They will eventually crack but the will not be really effected
as the standard rotors will have small cracks as well ....
If you are racing it prob helps in cooling the rotors etc.
People used to joke and call them cheese graters ....
I think they look pretty nice but I don't think you have to worry about the cracking especially if your not racing
Regards
Ed

GOBOGIE

Definately have some curb appeal!

Evan70

I think you'll find that anyone that's serious about tracking their car will NOT run crossdrilled rotors. Personally, I would even avoid rotors with the holes cast in and stick with non-drilled rotors even for street use. Also, I would avoid Ebay crossdrilled rotors at all costs. Their is no telling who drilled the rotors, whether they actually used a proper pattern that avoids the cooling vanes inside the rotors, and if they chamfered the holes. Considering how much is riding on your brakes, it's worth the extra money to buy good quality rotors from a trusted source (Zims has good prices on them).

RKD in OKC

In the specs for my 01 Boxster S that came with holy rotors from the factory it said, "The drilled rotors are for water egress and better braking in wet conditions." Said nothing about cooling. They did look cool though.

When I was tracking my 88 Turbo S my braking style was always heating up the front rotors blue, smoking pads, and boiling brake fluid. I went with Zimmerman slotted rotors because of the track horror stories of holy rotors and it helped tremendously. The slotted rotors help move the gases and pad material away from the surface.

The guys that were running holy rotors at the track said they inspected them for cracks around the holes after every session.

Evan70

I like that, "holy" rotors.
A couple of things to keep in mind about slotted rotors:
1. they will eat pads significantly faster than blank (non slotted/drilled) rotors
2. they really aren't nescessary for anything but heay track use. Modern pads do not outgas very much at all, and therefore don't need drilled/slotted rotors for street, autox, or even most track days.
Slotted rotors will however make sure you have the cleanest pad surface at all times, which is of course a good thing for those pushing the limits.

phils87951

You will get marginally better cooling with the haha holy rotors.
The reason you ge tthe feeling of better braking is that the holes are scraping away pad material al the time, giving you a " fresh" surface.

I only track my car, and have just as good if not better resluts with full rotors. I do have air ducted into them.

like I said before and others have confirmed, the holes are there for gasses when your pads dont have a slot in them and for improvrd wet weather braking.

heck i even get heat cracks on full rotors. but at least they cant jump from hole to hole causing a potentially catastrophic failure of the rotor.

the way i see it is that you are paying more for less unless it rains most of the time where you live.

RK951

Anyone happen to know the diameter of the stock front rotor for an '89 951? Eyeballing it looks like 11-12inch.

My interest in this topic arose when I started planning for the upgrade to 17inch wheels. I noticed my current rotors have that surface rust down by the hub which will be more visible with C2 wheels. I'm now trying to decide whether I'm better off sanding them down and spraying/sealing vs. just getting new ones and putting these in the closet. I don't expect any performance improvement but if I'm buying new ones I like the cross drilled appearance.

Evan70

New rotors will rust as soon as the oil coating is removed. The only way to avoid rust is to paint the hub area. It's really easy to do, just sand them down to clean off the surface rust, then paint with high temp paint (I've found black usually looks best). You don't even need to tape off the pad contact area, just make sure the paint dries thoroughly before reinstalling, as the pads will clean off any overspray on first couple of stops.

RK951

Any particular recommendations on sand paper grit? Black is probably a good idea but I was wondering if there was some sort of high temp clear coat seal spray to keep that raw metal look (as if it would stay clean).

Evan70

Doesn't need to be very coarse at all. I forget what I used, but it was a pretty fine grit, it doesn't take much to get it off. Don't know of any high temp clear coat, but you could ask at any auto parts store and they should be able to tell you.