I have Original front rotors?? I need replacements. 1' or 1.25 Look inside!

[Nasty-LSX]

I think I still have original front rotors, WOW. I say this because the rotors have holes in them like originals. I never seen
replacements with holes. Any way, I am finally getting around to putting in the Performance gear box. I seen my brakes
and rotors are really bad. Time to swap out for new stuff. My rotors are so worn I cant tell if I have the 1in or 1.25 thick
rotors. How do I know or tell what would be the correct replacement rotors for a 86 C10? Thanks.

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

 

[nvrenuf]

There should be a min thickness measurement cast in the rotor somewhere (probably the backside), this should tell you which one you have since the new to min tolerance difference is in the thousandths of an inch (ie; less than .25”).

 

[Turbo4whl]

I think I still have original front rotors, WOW. I say this because the rotors have holes in them like originals. I never seen
replacements with holes. Any way, I am finally getting around to putting in the Performance gear box. I seen my brakes
and rotors are really bad. Time to swap out for new stuff. My rotors are so worn I cant tell if I have the 1in or 1.25 thick
rotors. How do I know or tell what would be the correct replacement rotors for a 86 C10? Thanks.

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

They do look like factory rotors. Many people had their vehicles serviced at the dealer. The dealer had many parts that were an exact match to the original equipment. I put 280,000 miles on my 1982, only one set of replacement rotors. If memory serves, I believe I only had the original rotors cut one time. Well over the 200,000 miles before I replaced the original rotors.

 

[KMC1]

Holes? What holes? Are you referring to the cooling slots? All rotors have those. And what about them makes you say they're in bad shape, unless I'm not seeing it in these pics, they look normal to me.
What is the thickness of them now?

 

[bluex]

Just measure then with a tape measure. Anything over 1" an you had 1.25" rotors. If it's under an 1" then they were 1" since it's an 86 they more than likely are 1" but measure before you buy parts. There's no way you wore 1.25" rotors down to or under 1" without other issues.

 

[Octane]

I have originals on my 77 k10 also, 130k.+ I just started on the 2nd set of pads,that I put on there anyway, in 22 years.

 

[Nasty-LSX]

Holes? What holes? Are you referring to the cooling slots? All rotors have those. And what about them makes you say they're in bad shape, unless I'm not seeing it in these pics, they look normal to me.
What is the thickness of them now?

Cooling slots are not on aftermarket replacements. There is a deep lip on top of rotor and lower part by the hub.
There are no grooves on the surface face, but these are worn thin. Im pretty sure they have been turned before also.

You must be registered for see images attach

look at lower pad to rotor surface. That a deep lip. Same way on top. Just hard to see. They are a hair under 1 inch.

 

[nvrenuf]

Those are “vented” rotors. Rotors are made either solid (1 single disc) or vented (2 disc with the dividers), what a vehicle has is spec’d by the manufacturer and aftermarket replacements should be made like the original.

 

[bluex]

Cooling slots are not on aftermarket replacements. There is a deep lip on top of rotor and lower part by the hub.
There are no grooves on the surface face, but these are worn thin. Im pretty sure they have been turned before also.

You must be registered for see images attach

look at lower pad to rotor surface. That a deep lip. Same way on top. Just hard to see. They are a hair under 1 inch.

They don't look "thin" to me, just worn. If they measure under 1" at the ridge then they are the LD rotors.

Another way you can double check is the inner bearing. Take it out of the rotor an take it to the parts store. Compare it with a new bearing for each rotor. The difference is pretty easy to see when they are side by side. If they happen to be 1.25 (which I highly doubt) the bearing for a 1" rotor won't go all the way on the spindle. The inverse is the 1.25 bearing is much larger than the axle on a 1" spindle, also if you try to use a 1.25 rotor on the 1" spindle the castle nut won't go on correctly an you can't get the pin in.

A 3rd way to check, Take the rotor off, lay it flat an measure the overall height to the dust cap face an compare as well. There will be a .25" diff there regardless of pad contact area wear.

 

[bluex]

I found this to add for anyone else who might be looking to figure out the difference in rotors.

It goes with #3 above. With the rotor laying flat a 1" is 4.65" over all height. The 1.25" is 4.95"

 

[mlsceo]

The 4th pic from the top of your OP. At the 7 0'clock position are the letters MIN, following that should be a number. I can't read it from here but what is that number?

 

[Keith Seymore]

What is your GVW rating?

Manual brakes and the lightest power system (JB1 and JB3, respectively) get the 1" rotor, which is kinda rare.

Anything above that (JB5, which was the bulk of the production volume) gets the 1.25" rotor.

K

You must be registered for see images attach

 

[Nasty-LSX]

The 4th pic from the top of your OP. At the 7 0'clock position are the letters MIN, following that should be a number. I can't read it from here but what is that number?

it says min thick 24-5 or 24-6

You must be registered for see images attach

 

[KMC1]

Cooling slots are not on aftermarket replacements. There is a deep lip on top of rotor and lower part by the hub.
There are no grooves on the surface face, but these are worn thin. Im pretty sure they have been turned before also.

You must be registered for see images attach

look at lower pad to rotor surface. That a deep lip. Same way on top. Just hard to see. They are a hair under 1 inch.

Yeah, I didn't even see the pic with the MIN THICKNESS on it. You have 1" rotors. Minimum thickness is 24.5mm, which is .964 .

 

[Nasty-LSX]

Awesome, thank you KMC1