More brake help!

sharpshooter677 · 05-24-2009, 07:05 PM

I bought rear rotors for my 74 911. Zimmerman Part # 901-352-041-14-M259. They fit all 1974-83 911 models. These rotors DO NOT fit on my car. They are about 1/2" too small at the Hub. To mamke matters more confusing car was previously installed with a 3.2 motor. Meaning what? Im not sure. To my knowldege, I have the original 915. My quesiton, what would be the next size up rear rotors, that could possibly fit my car. I am waiting to send back the rotors I have now to Pelican, untill I know the right ones to buy. Thanks

Flieger · Flieger's Garage

You do not have any wheel spacers, do you?

What size wheels are you running?

I cannot remember if your car is narrow body or has the SC/Carrera flares to go with the 3.2 engine.

You probably have a 915 gearbox. It is a big job to retrofit a G50. Where is first gear in the pattern? Up and to the left, right above 2nd? That is a 915.

If you have wheel spacers for wider wheels (more likely if you have flares), that may be causing interference.

Photos would help a lot for better diagnoses.

Do you have 101 Projects for Your Porsche 911?

sharpshooter677 · 05-24-2009, 11:25 PM

No spacers, yes it is a 915 haha, 7" wheels, no flares ( I wish) just straight narrow body, and yes ofcousre, 101 projects is in my collection. I will take some pictures a.s.a.p.

Bill Verburg · Bill Verburg's Garage

Quote:

Originally Posted by sharpshooter677

I bought rear rotors for my 74 911. Zimmerman Part # 901-352-041-14-M259. They fit all 1974-83 911 models. These rotors DO NOT fit on my car. They are about 1/2" too small at the Hub.

Before you send the rotors back a little more investigation is in order.

all 911 from ;69 - '83 used the same rear rotors, you do have the correct rears as noted by the part #

what is meant by the part I underlined?

'84-89 rotors will have exactly the same hubs, w/ a 4mm thicker annulus

even the rear 930 rotors have the same hub as what you now have.

sharpshooter677 · 05-25-2009, 09:52 AM

Right, what I meant is that, the outside hat of the rotors I purchased, (in diameter) is roughly 1/2" shorter than the outside hat of the rotors I have on my car now. My motor is an 85...is it possible to have an arm and brake assembly to match?

Bill Verburg · Bill Verburg's Garage

Quote:

Originally Posted by sharpshooter677

Right, what I meant is that, the outside hat of the rotors I purchased, (in diameter) is roughly 1/2" shorter than the outside hat of the rotors I have on my car now. My motor is an 85...is it possible to have an arm and brake assembly to match?

I'm not sure if it is your terminology or what but I'm still very confused. A pic would help a lot.

all the 911 rear rotors from '69 - 83 are 20x290mm
from '84 - 89 the hub is the same but the annulus is thicker, 24x290mm
the only other rear rotor used fro '78 - 89 was the 930, again same hub section but the annulus is 28x309mm

pre '69 there were some 18x290mm but it's extremely doubtful that they would show up on any later car.

sharpshooter677 · 05-25-2009, 10:12 AM

Sorry ha, I will post some pics soon.

sharpshooter677 · 05-25-2009, 12:27 PM

Hope this helps. Wasnt sure what the best way to approach this was. THANKS!

Bill Verburg · Bill Verburg's Garage

At first glance the rotor in your hand apears to be for another car, perhaps a 964.

Are there any casting #s on the rotor?, the boxes they came in had the correct 901-352-041-14 part #?

A 911 rear for '69-83 will measure a tad under 13/16" x a tad under 11 7/16"

a 911 rear for '84 - 89 will measure a tad under 15/16" x a tad under 11 7/16"

964 rear will measure a tad under 15/16" x a tad over 11 3/4"

sharpshooter677 · 05-25-2009, 06:41 PM

964? Hmm, well I believe this would be the cast number from the rotor.. H1010SD303. Also the rotor reads,{ 2.153 MIN. THICK 0 800 INCH (20.4mm) }. I'm afraid I have misplaced the yellow sheet from the box indicating the parts. I hope this is helpful.

Bill Verburg · Bill Verburg's Garage

Ok, we have established that the rotor in hand is not a 911 '69-83 rear. I strongly suspect that it is a 964 rear

Now lets measure the one on the car.

measure the thickness, as accurately as you can, at the edge of the rotor

sharpshooter677 · 05-26-2009, 05:36 PM

Is this good enough?

sharpshooter677 · 05-29-2009, 09:57 PM

Need more help!

Bill Verburg · Bill Verburg's Garage

Quote:

Originally Posted by sharpshooter677

Is this good enough?

The rotor on the car is a stock 20x290. the other one appears not to be.

Just to be sure measure the thickness and total diameter of the new one, my guess is that it is ~15/16x 11 13/16" (24x299mm)

send it back it was in the wrong box.

the part # you want is 901-352-041-14

sharpshooter677 · 06-01-2009, 06:29 PM

Quote:

Originally Posted by Bill Verburg

The rotor on the car is a stock 20x290. the other one appears not to be.

Just to be sure measure the thickness and total diameter of the new one, my guess is that it is ~15/16x 11 13/16" (24x299mm)

send it back it was in the wrong box.

the part # you want is 901-352-041-14

ok so... this is to confirm that the rotors I have are incorrect and that the correct ones are 901-352-041-14... alright I already called and they said im gunna get charged a restocking fee..plus i have to ship it!

sharpshooter677 · 06-01-2009, 06:35 PM

also...does it matter that one model rotor ends with M367, which is the cross-drilled version? (901-352-041-14-M367) Because I purchased the slightly more inexpensive (901-352-041-14-M259)...and I received the clearly wrong part.

Bill Verburg · Bill Verburg's Garage

Quote:

Originally Posted by sharpshooter677

ok so... this is to confirm that the rotors I have are incorrect and that the correct ones are 901-352-041-14... alright I already called and they said im gunna get charged a restocking fee..plus i have to ship it!

Clearly they sent the wrong rotors, a '74 911 wants rotors in back that measure ~13/16" x 11 7/16", the drum for the parking brake will measure ~ 6 7/16"

as far as I can see the new rotors you have are 13/16" (which is ok) x 11 9/16" (this is not ok)w/ a drum measuring 6 4/16"(this is not ok)

visually you can see the difference in the drum sections, the '69-83 911 rear will have an externally tapered drum the new one has a square drum as used on the later cars
you have the correct part #901-352-041-14

Pelican uses the extra charaacters to distinguish between the 3 versions of the same rotor that they sell
901-352-041-14-M259 plain
911-352-041-08-M359 w/ galvanized drum(this is the one I would buy)
901-352-041-14-M367 drilled

They are all the same rotor casting and all should measurre the same.

Did you explain that the mistake appears to be on their end?

sharpshooter677 · 06-02-2009, 09:00 AM

I see. Yes well that makes alot of sense. My ultimate concern is that my car was not zombied together and I had some mismatched parts together. But okay sounds good. I will go ahead and call again explaining what happened, and re-order the 911-352-041-08-M359 rotors.

I really appreciate the help Bill and thank you very much! Very informative and thorough. Your a lifesaver!

Thanks again.