When did brake rotor hat height change?

[Royce]

Howdy folks,

I have a 09/71 built 240Z ('71 model). I just received new rotors but they don't fit. The "hat" height is different. I used a tape measure and got the following measurements.

The new rotors have a hat height of ~1.25".

The old rotors have a hat height of ~1.5".

I did have some old rotors around from a parts car that look like they match the new rotors. In fact on the spares it looks like the hub is thicker and the rotor hat is more narrow. So the net result looks the same, using eyeball only. I am sure they came from a first generation Z but not sure what year or 240, 260 or 280. I really don't want to use the hubs attached to these spares because the bearings in them look like they should be replaced. The bearings in the hubs that came off my car look good.

Also, I am not sure if the spare hub rotor combination would be a bolt on swap anyway.

Anyone know when the change was made to the rotor hub and hat?

Anyone know if the thinker hub/thinner hat combination could be swaped for the combination that I took off the car?

I did try a search on rotor hat and read through those posts but did not find my answer.

Thanks for any assistance!

[Nissanman]

The rotor for all 240Z cars, 1970-1973 has a "hat" dimension of 52mm or 2".

The manufacture includes the rotor thickness in their "hat" spec.

If you add the rotor thickness to your measurement of 1.5" that gives the right spec for a 240Z rotor.

However, for 260Z cars, 1973-1978, the "hat" dimension is 43.5mm or 1.7".

1.25" plus rotor thickness gives 1.7".

So, what you have are 260Z rotors.

The critical bit is locating the disc rotor in the centre of the calliper you wish to use.

Unless the hub+rotor combination puts the rotor smack in the middle of the calliper slot, it ain't going to work:angry:

If your mix and match achieves the correct rotor placement, it will probably be OK:nervous:

[sblake01]

In the US, they changed 8/73 with the 74 260Z which are the same as the 75-78 280Z. Found that out some years ago when I found a pair of brand new 240Z rotors in the hatch area of a junkyard car. Took them home only to find out that they wouldn't work on my 78. So you could have 260Z or 280Z rotors.

[Royce]

Nissanman, Good call. You guessed correct. I did measure the rotor hat from the outside starting at the rotor surface and not from the inside which would include the rotor surface. Thanks to you and Stephen for the information.

I was just on MotorSport auto web site and it "seems" that the wheel bearings and seals are the same from '70 240 - '83 280ZX. So that seems to support my theory that the 240 hat/rotor combination might be able to be swapped with the later 260 hat/rotor combination. I tried to confirm on the Courtesy Nissan site, but they do not list the wheel bearings. I may have to break out the Z parts CD that I bought from this site a long time ago!

I'll have to take some more measurements and see if the bearing race sits in the same place relative to the axle and that the rotor will be in the same place relative to the caliper.

Why do all this, you ask? Because I have everything apart and am waiting for the guy to respond regarding how he wants to handle the return of the rotors. I don't think he believes me, that they are wrong, just yet. So I figure I will see if it is in my interest to keep them and use the other hubs.

Thanks for reading!

Royce