Need HELP! with brake question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**ScottH** · 09-20-2006, 11:46 AM

I have a 65 Chevy G10 van I'm in the process of working on to get it road worthy. Most of the work is done with the exception of the brakes. The fronts are stock 9.5 x 2.5 drums but it looks like the rear might have been changed. The stock size for the rear drums are either 9.5 x 2.5 or 9.5 x 2, depending on which rear was installed at the factory.

The rear drums on the posi rear now in the van are 11 x 2. From running the numbers off the wheel cylinders, it appears that the rear was from a 66 and up full size GM car, like an Impala.

So my question to our brake gurus is am I going to have problems with the rear drums/shoes being larger than the fronts? Keep in mind this is a single master cylinder system.

Any info, suggestions, or opinions would be greatly appreciated!

Thanks.

Scott

**dennislbrooks** · 09-20-2006, 02:22 PM

put disc on front with a proportioning valve and a 72 c10 master cylinder and all should work well

**ScottH** · 09-20-2006, 03:30 PM

I would if it was an easy low cost solution. But on these vans it is anything but.

**ScottH** · 09-21-2006, 09:37 AM

Can anyone address this size difference question???

sneakysnake · 09-21-2006, 10:06 AM

Depending on the volume differences in the wheel cylinders(bigger brakes need more fluid)the bigger drum and shoes should give you better stopping power.

**ScottH** · 09-21-2006, 02:42 PM

So are you saying the larger shoe/drum combo in the rear will do most of the stopping?

**dennislbrooks** · 09-21-2006, 03:09 PM

I would think they would tend to lock up easier

**ScottH** · 09-21-2006, 07:27 PM

The front wheel cylinders are 1 1/16 bore, while the backs are 1 inch bore.

Right now I'm thinking of changing the system from a single cylinder MC to a dual with a proportioning valve. I'm guessing it would solve the problem plus make it a lot safer from losing the entire brakes should a leak develop. Guess I'll have to re-plumb the entire system.

09-20-2006, 11:46 AM	#1
ScottH Senior Member Join Date: Sep 2002 Location: Hampstead, NC Posts: 8,190	Need HELP! with brake question I have a 65 Chevy G10 van I'm in the process of working on to get it road worthy. Most of the work is done with the exception of the brakes. The fronts are stock 9.5 x 2.5 drums but it looks like the rear might have been changed. The stock size for the rear drums are either 9.5 x 2.5 or 9.5 x 2, depending on which rear was installed at the factory. The rear drums on the posi rear now in the van are 11 x 2. From running the numbers off the wheel cylinders, it appears that the rear was from a 66 and up full size GM car, like an Impala. So my question to our brake gurus is am I going to have problems with the rear drums/shoes being larger than the fronts? Keep in mind this is a single master cylinder system. Any info, suggestions, or opinions would be greatly appreciated! Thanks. Scott

09-20-2006, 02:22 PM	#2
dennislbrooks Senior Member Join Date: Feb 2004 Location: Williamsburg, Ohio Posts: 1,798	Re: Need HELP! with brake question put disc on front with a proportioning valve and a 72 c10 master cylinder and all should work well

09-20-2006, 03:30 PM	#3
ScottH Senior Member Join Date: Sep 2002 Location: Hampstead, NC Posts: 8,190	Re: Need HELP! with brake question I would if it was an easy low cost solution. But on these vans it is anything but.

09-21-2006, 09:37 AM	#4
ScottH Senior Member Join Date: Sep 2002 Location: Hampstead, NC Posts: 8,190	Re: Need HELP! with brake question Can anyone address this size difference question???

09-21-2006, 10:06 AM	#5
sneakysnake It's a catastrophic success. Join Date: Jan 2003 Location: Oklahoma Posts: 2,077	Re: Need HELP! with brake question Depending on the volume differences in the wheel cylinders(bigger brakes need more fluid)the bigger drum and shoes should give you better stopping power.

09-21-2006, 02:42 PM	#6
ScottH Senior Member Join Date: Sep 2002 Location: Hampstead, NC Posts: 8,190	Re: Need HELP! with brake question So are you saying the larger shoe/drum combo in the rear will do most of the stopping?

09-21-2006, 03:09 PM	#7
dennislbrooks Senior Member Join Date: Feb 2004 Location: Williamsburg, Ohio Posts: 1,798	Re: Need HELP! with brake question I would think they would tend to lock up easier Last edited by dennislbrooks; 09-21-2006 at 03:10 PM.

09-21-2006, 07:27 PM	#8
ScottH Senior Member Join Date: Sep 2002 Location: Hampstead, NC Posts: 8,190	Re: Need HELP! with brake question The front wheel cylinders are 1 1/16 bore, while the backs are 1 inch bore. Right now I'm thinking of changing the system from a single cylinder MC to a dual with a proportioning valve. I'm guessing it would solve the problem plus make it a lot safer from losing the entire brakes should a leak develop. Guess I'll have to re-plumb the entire system.



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