Chevy P30 Chassis 1973 brake rotor clearance.

[DryCamper11]

I had to replace the front rotor on my '73 P30 Sportscoach RV. The local NAPA had no listing for '73 dual rear wheel P30, but they did have one for the '75 and the rotor matched all dimensions, except thickness of the disk. When installed, The heads of three bolts holding the rotor shield on would slightly touch the surface of the rotor. I removed the lock washers and they still slightly touched. I had to grind the heads down 30% thinner to clear.

Does anyone know if I've gotten the wrong rotor?
TIA

[SuperDutyFiver]

Well if it may have been an issue on the other side as well I'd just go with it the way you got it together-Of course taking a good test drive to make sure all is good-even maybe pulling the wheel to do a visual afterwards!

Bigger concern-did you figure out why one side wore faster? were the contact points the pads ride in a mess? Do they make retrofits for those old capipers to add some kind of stainless shims to eliminate the 'stickiness' your pads may have experienced?

[MEXICOWANDERER]

I had a tenant at the RV park who pulled in with his brakes on fire. E-450. We went to the refraccionia (parts store). Brand new rotor, fifty four dollars (in pesos). "Sorta weird" he explained as he measured the difference between the old and new rotors. "You mean I wore two pounds worth of metal off these originals?"

He loved doing a full brake job under the palms. He emailed me a few months later and said all the parts, the total cost him three hundred dollars less than what the USA parts stores wanted. It's a bear having to fork over four dollars eighty cents each to have the new discs turned. Intelligent guy, he even replaced the master cylinder when he ran his finger down into the goo at the bottom. New drums, calipers, hoses, cylinders. This guy went for it.

[DryCamper11]

MEXICOWANDERER wrote:
No problem. Your rotors were cast and machined down here in Mexico in the city of Monterrery, Nuevo Leon. Or in a suburb. Want boring nomenclature? The iron was cast in Monclova. Nuevo Leon. Gad I've been down here too long 😞

Your original rotors were hybrid metric (bearings) and US standard (inches) for rotor dimensions. Not the new rotors, they are all metric - to the closest mm match to the original inch measurement. They didn't want to be accused of "cheating" so they "rounded up" instead of "down" with the mm's.

That probably explains it. Those suckers are heavy! I had to put them on/off a half dozen times as I worked on the clearance issues.

[DryCamper11]

SuperDutyFiver wrote:
Was there a lot more meat on the disc than your old rotor or is the gap between the two surface greater?

I'm amazed that the dust shiedl hasn't rusted away and that you could even get the bolts off!

Yes, there's lots more meat. The previous one had been reground enough that this time it just wouldn't take another regrinding. I'd (stupidly) used brake pads that have rivets instead of the newer ones with the adhesive pad attachment, and one side wore out much faster than the other. The rivets cut those awful grooves.

Still.... the new rotor should have had clearance unless they are building the rotors with much greater thickness than in '73.

I do vaguely recall that I may had to replace the other side 10 years ago and had to remove the lock washers from the shield bolts to get more clearance until the pad had worn down a bit. On this side, however, I've had to remove those washers and grind down the bolt head. I like having more beef in the rotor thickness, but I sort of wondered if anyone else had ever seen this issue.

The shield was still in great shape - and the bolts came off with little or no effort. The DW was standing there and commented "Those bolts will never come off." She was amazed they came off so easily.

[MEXICOWANDERER]

No problem. Your rotors were cast and machined down here in Mexico in the city of Monterrery, Nuevo Leon. Or in a suburb. Want boring nomenclature? The iron was cast in Monclova. Nuevo Leon. Gad I've been down here too long 😞

Your original rotors were hybrid metric (bearings) and US standard (inches) for rotor dimensions. Not the new rotors, they are all metric - to the closest mm match to the original inch measurement. They didn't want to be accused of "cheating" so they "rounded up" instead of "down" with the mm's.

[SuperDutyFiver]

Was there a lot more meat on the disc than your old rotor or is the gap between the two surface greater?

I'm amazed that the dust shiedl hasn't rusted away and that you could even get the bolts off!