Swapping to 73+ rotors

[ratrod67]

Is it possible to swap from the rotor on my 71 to a 73 and newer rotor? Are the bearings the same? I have a set of wheels and tires that are 5x5 pattern but the centerhole is too small to fit over the 71 rotors. I have ECE drop spindles on the truck right now.

[SCOTI]

Originally Posted by ratrod67

Is it possible to swap from the rotor on my 71 to a 73 and newer rotor? Are the bearings the same? I have a set of wheels and tires that are 5x5 pattern but the centerhole is too small to fit over the 71 rotors. I have ECE drop spindles on the truck right now.

I seem to recall the 'pilot hole' for the hub is the same dimension on all the 1.25" C10 disc rotors so I don't think the 73-up will work any better. That being said, any machine shop should be able to turn the rotors hub down to the dimension you need w/o breaking the bank & might be worth investigating since you already have the wheels.

[tdave00]

I just bought a set of drop spindles from Tim Christian and he told me the 73 and up rotors were the only ones that would work with these drop spindles. The brand is Mcgaughay. I don't know if that helps your situation any, but that's what he told me because I already had a set of rotors and calipers from a 69.

[ChevLoRay]

The nice thing about the ECE components is that the boxes arrive with GM labels on them. Aren't GM rotors the same from '71 to '87? All of their components are designed so you can use aftermarket parts to replace anything with a stock spec.

Does this situation boil down to the wheels being hub centric and not originally designed to fit the stock hubs on our trucks?

[Longhorn Man]

If the pilot hole was smaller starting in 73, then we'd never be able to run the 73 - 87 rallys on the 71/72 trucks.
They are the same size.

I already had a set of rotors and calipers from a 69...

Not likely, since trucks never had disks untill 71. EVERY gm truck built before 71, was drum brake equipped.

Aren't GM rotors the same from '71 to '87?

No... the 73 - 87 are thicker, and if I am not mistaken, the lugs went metric sometime in the 73 - 87 run too.

[SCOTI]

Originally Posted by Longhorn Man

If the pilot hole was smaller starting in 73, then we'd never be able to run the 73 - 87 rallys on the 71/72 trucks.
They are the same size.


Not likely, since trucks never had disks untill 71. EVERY gm truck built before 71, was drum brake equipped.


No... the 73 - 87 are thicker, and if I am not mistaken, the lugs went metric sometime in the 73 - 87 run too.

71-80's were 1.25" as far as I know. Then 81-87's were available in 1.00" or 1.25" options.

[ChevLoRay]

Call ECE.....they have a toll-free tech line.

[michael bustamante]

I thought the 73-87 rotors would not work on a 71-72 hub, the center hole isint the problem but the way it mounts to the spindle, as for the wheels, I thought the size of the hub (centerhole) went smaller in 1999.

[tdave00]

Sorry, don't know what I was thinking. The guy who gave them to me pulled them off a 69. A previous owner had put them on there. I knew better. I meant 71-72.

[ratrod67]

Thanks for all of the replies. All I know is I bought the wheels and they were on a 78 Blazer but wont fit onto my 71. The wheels are weld draglites. I called Summit and talked to a tech and he told me the wheels were different from 71-2 to 73 and up. The centerholes are smaller on the 73 and up. I was hoping I could just swap rotors and be ok. They fit on the front of my 67. The 67 has a 78 crossmember swapped in.

[SCOTI]

Originally Posted by ratrod67

Thanks for all of the replies. All I know is I bought the wheels and they were on a 78 Blazer but wont fit onto my 71. The wheels are weld draglites. I called Summit and talked to a tech and he told me the wheels were different from 71-2 to 73 and up. The centerholes are smaller on the 73 and up. I was hoping I could just swap rotors and be ok. They fit on the front of my 67. The 67 has a 78 crossmember swapped in.

I had to turn down the rotor 'snout' to install the car wheels (steel & TT2's) on my 74.

[ratrod67]

Originally Posted by SCOTI

I had to turn down the rotor 'snout' to install the car wheels (steel & TT2's) on my 74.

Any reccomendations on a place to get it done?