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Rust-O-Matic 04-02-2015 09:33 AM

'66 C20 Wheel Cylinder Bolts
'Mornin fellas, new guy here. Been lurking around here for a couple years though. This site is a huge wealth of info, so I'm hoping somebody can point me in the right direction on my latest endeavor.

I'm replacing the rusty, crusty, froze up brakes on my '66 C20 and I managed to mangle the head on one of the wheel cylinder bolts. There is two in each cylinder, that go in from behind the backing plates. They are 5/16" x 18 thread, 1/2" long, and require a 3/8" socket to remove them (or a 9mm custom fit with a hammer after you booger up the head). The head size is important, because it's smaller than a standard 5/16" bolt would be, giving clearance to get a wrench on it. They look pretty much like standard header bolts, but shorter. For whatever reason, I'm having a hell of a time finding replacements. I'd like to just replace all of them if I can find some because they're pretty rusty.

I've tried all the usual places, Google, Advance, Oreilly's, Rockauto, LMC truck, half a dozen local hardware stores, and they either don't have anything similar or the guy behind the counter has no idea what I'm talking about. There's lots of "GM style" wheel cyl. bolts on eBay, but none of them appear to have the smaller head on them like mine. I assume GM put these things on bazillions of vehicles over several decades, so I'm surprised I can't find any. Maybe I'm not calling them by the right name or something? Does anyone know where I can get some of these? Any help would be greatly appreciated.

jtrichard 04-02-2015 11:06 AM

Re: '66 C20 Wheel Cylinder Bolts
You could probably use these

Rust-O-Matic 04-02-2015 11:31 AM

Re: '66 C20 Wheel Cylinder Bolts
Those do look awful similar! I wish the spec section listed the flange diameter though. Maybe this is my plan B, if I can't find the correct ones. Thanks for the link man.

jtrichard 04-02-2015 11:38 AM

Re: '66 C20 Wheel Cylinder Bolts
Those generally have small flange as they are use in tight spaces i would say they would work great

Rust-O-Matic 04-02-2015 12:45 PM

Re: '66 C20 Wheel Cylinder Bolts
I think they'd work fine on the rear ones, but it just occurred to me I had to remove the front ones with the open end of a wrench because the spindle is in the way and I can't get to it with a ratchet. The closed end of the wrench wouldn't even fit between the bolt head and the spindle once the bolt was turned out a few threads. So the 12 point head might be a problem on the front.

jtrichard 04-02-2015 12:50 PM

Re: '66 C20 Wheel Cylinder Bolts
Then go socket head/allen

Rust-O-Matic 04-02-2015 01:02 PM

Re: '66 C20 Wheel Cylinder Bolts
Same scenario there, they'd work on the back but no room for a socket or allen key on the front. I wish I had taken a picture when I took the front apart the other night.

Maybe I should just leave the front ones alone and change the rear. The one I screwed up is on the rear, and they're easy to get to. I'm just afraid if I don't replace them all now, they will continue to rust and may snap off or something next time they are removed. It will probably be the next guy's problem by then, but still, that's not a surprise I'd like to receive.

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