The International CBX Owners Association

ericfreeman wrote:Here's a photo of the brake disc on a Porsche 917-30, arguably one of the fastest road racing cars ever built. Sure looks like holes in that disc to me.....Guess those Skip Barber fellows need to get out more often.

Eric

I second that remark, Eric!

I've seen countless pictures of racing brake rotors with holes in them. Actually makes more sense to me to have them on race cars since the braking loads are maximum nearly all the time and the cars are maintained constantly so any cracks would be noticed and parts changed out quickly. For a road car, the holes are probably overkill and of much less benefit, although they do tend to grab faster in the wet. I prefer slotted rotors for my street cars: no through-holes to worry about but still an escape path for pad gasses.

Eric

I think ther big advantage on a bike is you wind up with less swept area, so less chance of a wheel lock-up

If we were discussing race cars or race bikes where the brakes were used at near maximum capacity for extended periods, I suppose some (weak) arguments could be made for them - In the case of a CBX which isn't raced, it's all cosmetics . . . . Some folks think they look cool. I've never seen a pair of drilled rotors that added anything to the look of the bike, IMO - Unless they were professionally done with a carefully planned pattern, they could severely detract from the look though . . . . I've seen more examples of that than I can count - It gives the bike that unique 'home made' look

Don

spencer wrote:917-30? That would be Mark Donahue's number 6 or 7. (Actually, I guess about 5 exist, but only two were actually raced.) Absolutely my favorite race car of all time. Do you have any more pictures of it? I only have a few from when I saw Mark race it at Road America, in 1973.

I don't know, which one is Mark Donohue's car, but one of the 917/30 CanAm Spyders with the blue and yellow Sunoco Porsche Audi livery sits in the Porsche museum in Zuffenhausen. Not sure how many 917-30s survived. Some of them were modified after the SCCA rule changes in 1974 in order to continue to compete somewhere else. This happened to at least one of the Penske cars. Porsche campaigned the 917-30 in the Interserie in Europe after they had to pull out of CanAm. Brumos in Jacksonville has a 917-10.
I took this picture in 2003 in the historic racecar display during the 24-hrs of Daytona. I am not sure, whether this is the Brumos car.

Don wrote:I think ther big advantage on a bike is you wind up with less swept area, so less chance of a wheel lock-up

If we were discussing race cars or race bikes where the brakes were used at near maximum capacity for extended periods, I suppose some (weak) arguments could be made for them - In the case of a CBX which isn't raced, it's all cosmetics . . . . Some folks think they look cool. I've never seen a pair of drilled rotors that added anything to the look of the bike, IMO - Unless they were professionally done with a carefully planned pattern, they could severely detract from the look though . . . . I've seen more examples of that than I can count - It gives the bike that unique 'home made' look

Don

Funny!
Here we don't want to ride a CBX without chassis modifications front and back and yet we think it is nonsense to convert a CBX to cross-drilled rotors because it isn't raced.
I have a hard time thinking of any modern liter class bike currently, that does NOT have cross-drilled rotors. Even the Harleys do :|

It never rains in California....uh, wait a minute, it pours, man it pours...

Sorry if I am hijacking this thread. This will be the last one from me.

I don't know, which one is Mark Donohue's car, but one of the 917/30 CanAm Spyders with the blue and yellow Sunoco Porsche Audi livery sits in the Porsche museum in Zuffenhausen. Not sure how many 917-30s survived. Some of them were modified after the SCCA rule changes in 1974 in order to continue to compete somewhere else. This happened to at least one of the Penske cars. Porsche campaigned the 917-30 in the Interserie in Europe after they had to pull out of CanAm. Brumos in Jacksonville has a 917-10.
I took this picture in 2003 in the historic racecar display during the 24-hrs of Daytona. I am not sure, whether this is the Brumos car.

The 917 in your picture is a coupe. They were naturally aspirated, and ran mostly in the European endurance series. They generated about 680 hp and were the most successful of all the 917 models.

This is the Brumos car. It is a 917/10. It was driven by Hurley Haywood in the 1973 Can Am series. I was lucky to meet Hurley in Jacksonville, at Brumos Porsche, and I asked him about the 917. He very graciously took me to Brumos' car collection, and gave me a personal tour. They normally don't allow photography, but he allowed me to take one picture of the 917 with him standing beside it. I was thrilled. Hurley Haywood is a fine gentleman. This 917 is turbo charged, and I believe it normally generated around 1000 hp.


The 917/30 in the Porsche museum is one of the two which were owned by Roger Penske, and driven by Mark Donohue in the 1973 Can Am series. Number 6 was the primary car, and number 7 was the backup car. I don't know who owns the other one, but I wouldn't be surprised if Roger still has it. I believe that only two 917/30s were built originally, but two or three more were built from parts, later. This car produced up to about 1600 hp in qualifying trim, and normally raced at about 1100 hp. I believe it is the most powerful race car ever produced, except for dragsters. I believe it topped out at about 265 mph. One of Penske's cars was somewhat modified and set a closed course speed record in 1975, at Talladega, in spite of the fact that the attempt had to be cut short after two laps from a standing start, because of rain. Here is a picture I took of Mark driving number 6 at Road America, in 1973.


These cars instill the same type of feelings in me that I get from the CBX. Both are works of art.

spencer wrote: Sorry if I am hijacking this thread. This will be the last one from me.

Hurley Haywood is a fine gentleman.

Agree on both accounts Used to meet Hurley regularly and my wife Cindy liked to get into a shot with him before the race. For good luck

Samelak wrote:I have been thinking about drilling my stock rotors but I am unsure if its worth the effort.I am a machinist by trade and have access to a CNC mill that woud make the task simple. Any opinions from the forums would be appreciated.

Thanks, Lee

1. Wet weather performance is better.
2. Heat generated gases are relieved.

And lets not forget the "cool" factor........

Lee, I drilled mine about 30 years ago using a rotary table. Just my opinion but I don`t know if I would be comfortable using the Haas we have now. If I remember that steel was pretty tough stuff and dulled the drills, if that happens you know the cnc won`t let up but will try to jam the drill through creating a real mess.

Maybe useing the CNC and carbide drills and sharpen every so many holes per drill would work ok, sure would be faster than cranking a rotary. Thats alot of holes to drill.

Just don't try to drill used rotors. It may not be pretty at all.