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Bad rear lockup--prop valve or smaller cylinders? #55495 03/30/08 02:09 PM 03/30/08 02:09 PM
Joined: Jan 2003 Posts: 1,180 Willoughby Hills, Ohio gd9704 OP super gas
gd9704 OP super gas Joined: Jan 2003 Posts: 1,180 Willoughby Hills, Ohio	Okay, my other project for spring is to reduce the tendency of the Demon's rear tires to lock up under hard braking. I bought the smaller wheel cylinder's from E-booger and was about to go that route--but my cousin who's much more auto-savvy than me told me that a proportioning valve on the rear brakes hard line would be a better way to go..... What say you? Thanks Greg

Re: Bad rear lockup--prop valve or smaller cylinders? [Re: gd9704] #55496 03/30/08 02:14 PM 03/30/08 02:14 PM
Joined: Jan 2008 Posts: 3,886 Lost and Spaced B bboogieart master
bboogieart master B Joined: Jan 2008 Posts: 3,886 Lost and Spaced	Rick Ehrenberg knows his stuff nothing against your cuz. there should already be a proportioning valve in place.

Re: Bad rear lockup--prop valve or smaller cylinders? [Re: gd9704] #55497 03/30/08 02:17 PM 03/30/08 02:17 PM
Joined: Jan 2003 Posts: 25,748 Rio Linda, CA John_Kunkel Too Many Posts
John_Kunkel Too Many Posts Joined: Jan 2003 Posts: 25,748 Rio Linda, CA	Either way will work but changing cylinder size is a guessing game while the adjustable valve takes the guess work out of it. The INTERNET, the MISinformation superhighway

Re: Bad rear lockup--prop valve or smaller cylinders? [Re: John_Kunkel] #55498 03/30/08 02:25 PM 03/30/08 02:25 PM
Joined: Jan 2003 Posts: 1,180 Willoughby Hills, Ohio gd9704 OP super gas
gd9704 OP super gas Joined: Jan 2003 Posts: 1,180 Willoughby Hills, Ohio	Quote: Either way will work but changing cylinder size is a guessing game while the adjustable valve takes the guess work out of it. True....and I would have the ability to fine tune it as well.... Thanks, John.

Re: Bad rear lockup--prop valve or smaller cylinders? [Re: bboogieart] #55499 03/30/08 02:40 PM 03/30/08 02:40 PM
Joined: Jan 2003 Posts: 1,180 Willoughby Hills, Ohio gd9704 OP super gas
gd9704 OP super gas Joined: Jan 2003 Posts: 1,180 Willoughby Hills, Ohio	Quote: Rick Ehrenberg knows his stuff nothing against your cuz. there should already be a proportioning valve in place. I know Ehrenberg is the man. The factory proportioning valve is in place. The brakes work very well--but panic stops are very hairy--now with my wife and 2 year old in the car I worry about having to hit the brakes hard on the freeway...... My cousin was wrenching on these cars all through the 70s and 80s before they became "collector" cars. I respect his opinion on these things. I like to get a number of opinions before I decide to screw something up!

Re: Bad rear lockup--prop valve or smaller cylinders? [Re: gd9704] #55500 03/30/08 03:34 PM 03/30/08 03:34 PM
Joined: Jan 2003 Posts: 6,570 San Francisco Ca SCATPK master
SCATPK master Joined: Jan 2003 Posts: 6,570 San Francisco Ca	I just installed disc brakes on my 66 dart and used an adjustable prop valve to eliminate rear wheel lock up. This is the way to go as you can tune it for your specific car and its suspension and tires. After fine tuning mine it is amazing how good it stops.

Re: Bad rear lockup--prop valve or smaller cylinders? [Re: SCATPK] #55501 03/30/08 03:59 PM 03/30/08 03:59 PM
Joined: Jan 2003 Posts: 9,887 USA CrAlt master
CrAlt master Joined: Jan 2003 Posts: 9,887 USA	Have you pulled the drums and looked at the brakes? My dart started having a rear lockup problem... Then i pulled the drums and found that the leaky axle seals softened up the brake shoes and made them grabby. I was asked to contribute money to help solve the civil unrest in Egypt, but I suspect it's some sort of pyramid scheme.

Re: Bad rear lockup--prop valve or smaller cylinders? [Re: gd9704] #55502 03/30/08 05:25 PM 03/30/08 05:25 PM
Joined: Jan 2003 Posts: 36 M MarkD member
MarkD member M Joined: Jan 2003 Posts: 36	I put front disc rear drum on my Dart with an adjustable prop valve. I still need to go with the smaller wheel cylinders. The proportioning valve is adjusted out. That's why E man suggests the smaller wheel cylinders.

Re: Bad rear lockup--prop valve or smaller cylinders? [Re: gd9704] #55503 03/30/08 06:44 PM 03/30/08 06:44 PM
Joined: Aug 2006 Posts: 2,499 God's Country Maryland GODSCOUNTRY340 top fuel
GODSCOUNTRY340 top fuel Joined: Aug 2006 Posts: 2,499 God's Country Maryland	In '68 &'69 Mopar used a delay valve to cure your problem. It was located just behind the proportioning valve. (pic). These were installed on High Performance vehicles. In '70 Chrysler redesigned the proportioning valve so this wasn't needed. It delayed the pressure to the rear brakes so they wouldn't lock-up first. 4316226-DSC04267.JPG (53 downloads) I love the smell of Deer guts in the morning, it smells like... VICTORY!

Re: Bad rear lockup--prop valve or smaller cylinders? [Re: GODSCOUNTRY340] #55504 03/30/08 06:46 PM 03/30/08 06:46 PM
Joined: Aug 2006 Posts: 2,499 God's Country Maryland GODSCOUNTRY340 top fuel
GODSCOUNTRY340 top fuel Joined: Aug 2006 Posts: 2,499 God's Country Maryland	Here's another pic in relation to the distribution block. 4316233-DSC04266.JPG (47 downloads) I love the smell of Deer guts in the morning, it smells like... VICTORY!

Re: Bad rear lockup--prop valve or smaller cylinders? [Re: GODSCOUNTRY340] #55505 03/30/08 10:31 PM 03/30/08 10:31 PM
Joined: Sep 2003 Posts: 1,688 Marlboro, NY, USA R Rick_Ehrenberg top fuel
Rick_Ehrenberg top fuel R Joined: Sep 2003 Posts: 1,688 Marlboro, NY, USA	You really need to get the proportioning close w/o a valve (by juggling wheel cyl / caliper piston diameters, etc), then use the valve for the last 10% or so. Here's why: The valve doesn't "cut in" - begin to work - until there a few hundred PSI of line pressure. So in rain, etc., it doesn't do anything. And, if the rear wheels are locked, the car will - MUST - spin! Rick

Re: Bad rear lockup--prop valve or smaller cylinders? [Re: gd9704] #55506 03/30/08 11:32 PM 03/30/08 11:32 PM
Joined: Nov 2004 Posts: 1,708 S. Il. U.S.A. 5spdcuda top fuel
5spdcuda top fuel Joined: Nov 2004 Posts: 1,708 S. Il. U.S.A.	It took both to get my Cuda to stop to my satisfaction. Weight distribution and the relative grip of the front and rear tires all play a part in getting it right.

Re: Bad rear lockup--prop valve or smaller cylinders? [Re: Rick_Ehrenberg] #55507 03/31/08 08:19 AM 03/31/08 08:19 AM
Joined: Jan 2003 Posts: 1,180 Willoughby Hills, Ohio gd9704 OP super gas
gd9704 OP super gas Joined: Jan 2003 Posts: 1,180 Willoughby Hills, Ohio	Quote: You really need to get the proportioning close w/o a valve (by juggling wheel cyl / caliper piston diameters, etc), then use the valve for the last 10% or so. Here's why: The valve doesn't "cut in" - begin to work - until there a few hundred PSI of line pressure. So in rain, etc., it doesn't do anything. And, if the rear wheels are locked, the car will - MUST - spin! Rick Wow, thanks for the personalized response, Rick! I guess I was hoping to avoid taking the rear brakes apart....but I guess this will be an educational experience!

Re: Bad rear lockup--prop valve or smaller cylinders? [Re: gd9704] #55508 03/29/09 11:42 AM 03/29/09 11:42 AM
Joined: Jan 2003 Posts: 8,131 New Mexico UCUDANT Troll Hunter
UCUDANT Troll Hunter Joined: Jan 2003 Posts: 8,131 New Mexico	Rear brakes are fairly simple. Spring tools will help make the job a snap. Do one side at a time so you have an assembled example. Check to ensure your drums are not heavily grooved, glazed or out of spec.

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