STOP!! brake system questions - The 1947 - Present Chevrolet & GMC Truck Message Board Network

cobinder · 01-01-2008, 02:15 PM

I'm changing my 80 K20 to Hydroboost and all disc's. I believe my stock m/c is an 1-1/4" bore (it's so rusted I can't get the guts out).

I'm moving the master cylinder assembly to under the cab floorboard. So I want the brake line outlets on the opposite side from the stock m/c. All the master cylinders a can find to fit are only 1-1/8" bore. Is this a problem?
I have 39" military Michelins that are very heavy so I want good brakes.

thanks for any imput.

Ivan D. · 01-02-2008, 05:57 AM

Have you tried looking for big truck stuff, C30, K30, something like that? I got a C30 master cylinder in my truck, tis with the 1.25" bore, but ports are still on the wrong side...

LONGHAIR · 01-02-2008, 09:12 AM

Watch out for residual valves. When you convert to rear disc you need a different one for the rear brakes. The drum type valve holds more pressure in the lines because of the return springs on the shoes. If you run it like that with discs, there will be constant drag, wear, and of course heat. None of which is good.
Is this really an off road truck? Show truck?

cobinder · 01-03-2008, 05:23 PM

It's a functioning show truck. The body parts are too rare to do serious off roading

01-01-2008, 02:15 PM	#1
cobinder Everything is work in progress Join Date: Apr 2006 Location: Denver Colorado Posts: 326	STOP!! brake system questions I'm changing my 80 K20 to Hydroboost and all disc's. I believe my stock m/c is an 1-1/4" bore (it's so rusted I can't get the guts out). I'm moving the master cylinder assembly to under the cab floorboard. So I want the brake line outlets on the opposite side from the stock m/c. All the master cylinders a can find to fit are only 1-1/8" bore. Is this a problem? I have 39" military Michelins that are very heavy so I want good brakes. thanks for any imput. __________________ Good luck with your truck! How much?! It's just an old truck part!! 49 International on a 80 GMC 3/4ton 4x4 chassis 48 International KB-5 2 ton dump bed 04 Honda CRF "500" 09 Honda CRF450 fuel injected rocket 03 Suzuki hayabusa carbonfiber wheeled monster. 02 Ford diesel stretch van (toy hauler) 01 38' Monaco diesel pusher motorhome

01-02-2008, 05:57 AM	#2
Ivan D. glamoros piece o' lowlife Join Date: Mar 2007 Location: Redford, MI Posts: 1,164	Re: STOP!! brake system questions Have you tried looking for big truck stuff, C30, K30, something like that? I got a C30 master cylinder in my truck, tis with the 1.25" bore, but ports are still on the wrong side... __________________ The more I drink, the more I drink, the more I drink... diesel, reg cab, long bed, 4 across the rear, single stack, wooden stakes, and lotsa lights - the Hay Express

01-02-2008, 09:12 AM	#3
LONGHAIR just can't cover up my redneck Join Date: May 2004 Location: Columbus OH Posts: 11,414	Re: STOP!! brake system questions Watch out for residual valves. When you convert to rear disc you need a different one for the rear brakes. The drum type valve holds more pressure in the lines because of the return springs on the shoes. If you run it like that with discs, there will be constant drag, wear, and of course heat. None of which is good. Is this really an off road truck? Show truck?

01-03-2008, 05:23 PM	#4
cobinder Everything is work in progress Join Date: Apr 2006 Location: Denver Colorado Posts: 326	Re: STOP!! brake system questions It's a functioning show truck. The body parts are too rare to do serious off roading __________________ Good luck with your truck! How much?! It's just an old truck part!! 49 International on a 80 GMC 3/4ton 4x4 chassis 48 International KB-5 2 ton dump bed 04 Honda CRF "500" 09 Honda CRF450 fuel injected rocket 03 Suzuki hayabusa carbonfiber wheeled monster. 02 Ford diesel stretch van (toy hauler) 01 38' Monaco diesel pusher motorhome

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