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rotor size question 300zx


Guest 70datsun240

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Guest 70datsun240

Hi, ive searched for specs and could not find. I bought a set of 1984 300zx non turbo rotors, front and backs for my toyo vented swap and my 240zx rear swap. I purchased everything from Ross except the calipers and rotors. I recieved my rotors today and noticed the rear was so much larger than the front. The guy i got them off me said they were for 84 non turbo models excluding SF models and 1985-1989 (All non-turbo models) I specified that I needed 1984 non turbo 300zx rotors. I messured the fronts at 10 3/4 across and from outer lug to outer lug (diaginal)(4 lug) it was about 4.5" The rears were about 11 7/16 across and about 5" from outer lug hole to outer lug hole. Ross's spacer plates holes line up with the front rotors but the rear 240sx bracket doesnt line up with the rear. Is this correct or is somthing wrong? Any idea what rears I have if theyre not the right ones? specific months in 84 I needed to order from? Can someone please help clarify this for me, thanks again!, Ohh I can post pics if needed

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Pictures would help, but the OD of the rear rotor sounds correct. I measured the rotor (not a real good measurement) on my 240SX (it's a 300ZX NA rotor as well) and it was close to 11 1/2". The "hat" is about 1 3/8" tall as well.

 

When you say Ross' bracket does not line up, what do you mean exactly? Have you got the calipers on them to test fit?

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The 4 lug, non-turbo 300ZX rear rotors are a nominal 11 3/8" in diameter, 290mm. That is the rotor that goes with the 240SX calipers if you bought the adapters from Ross Corrigan at Modern Motorsports. That is the same kit I put on my car so I could retain the parking brake function.

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Guest 70datsun240

ok, looking at Ross's rear bracket now, im taking it that the 3 mounting holes dont mount up to the lugs. I guess they mount behind or somthing? Im alittle confused now, I bought the 2 front and 2 rear rotors for a 84 300zx. but the lug holes dont' match up, all the messurements on the rear rotor seem to be correct. I really just need to know the lug hole spacing. I doubt that they would be different from front to rear correct?

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You sound like you need to look over how everything goes together a bit before you start, as well as familiarize yourself with the parts.

The front rotor bolt holes do not use the stud pattern for mounting. Instead, the front rotor uses a separate set of bolts (on a smaller diameter) for mounting, and thus the difference between the front and rear rotor mounting hole patterns.

Also, the calilper braket mounts to the bearing carrier flange on the strut where the backing plate was mounted (else the calipers would spin around with the wheel if mounted on the studs).

Take a look at another car with the disc brakes intact, look over it real good, and you'll get the big picture on what you need to do. When you disassemble the front rotors, it will be obvious why the front rotors have a different mounting pattern than the rears do.

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