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| wheel cylinder sizing question https://www.slantsix.org/forum/viewtopic.php?t=67598 |
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| Author: | mcnoople [ Mon Jan 22, 2024 10:26 am ] |
| Post subject: | wheel cylinder sizing question |
I am having problems remembering how to properly size a rear wheel cylinder for more or less lockup. The car it will be going on is a 1965 valiant 2dr with 10X2 rear drum, BUT it is not chrysler rear drums and there is a huge available list of diameters for this setup. My choices are 11/16, 3/4, 13/16, 7/8, and 15/16. If it helps the front are 10.87 disc with "pin" type mopar calipers. The WC that are currently on the baking plates are a 7/8 but I haven't peeled the seals back to see if they can be rebuilt. Due to stupid cost of the correct width 8.75 axles and the scarcity of BBP 8.25 I sourced a toyota truck axle. It is 55" wide at the wheel flange, comes with 10x2 drums, and a 3.91 gearset for $200. |
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| Author: | SlantSixDan [ Mon Jan 22, 2024 12:40 pm ] |
| Post subject: | Re: wheel cylinder sizing question |
13/16" was always my go-to for 10" rear drum cylinders. The 15/16" factory-installed ones are too damn big, and Chrysler knew it; see here. Could probably run the 7/8" (=14/16", between the other two sizes I mention here) with 10" front drums rather than discs, but I'd still prefer the 13/16" in back unless I routinely carried or hauled heavy weight…and then I'd want discs up front, so I'd be back to wanting 13/16" cylinders in back! |
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| Author: | Greg Ondayko [ Mon Jan 22, 2024 5:11 pm ] |
| Post subject: | Re: wheel cylinder sizing question |
Thanks for that linked info Dan. Greg |
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| Author: | Badvert65 [ Mon Jan 22, 2024 7:00 pm ] |
| Post subject: | Re: wheel cylinder sizing question |
Would 3/4" be ok for 10 x 2 1/2" rear drums and front disk (65 two door B-body)? |
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| Author: | volaredon [ Tue Jan 23, 2024 10:22 am ] |
| Post subject: | Re: wheel cylinder sizing question |
I know that whatever they put into a 78 2 door b body from the factory with 10" brakes is awful touchy.... |
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| Author: | SlantSixDan [ Tue Jan 23, 2024 10:36 am ] |
| Post subject: | Re: wheel cylinder sizing question |
Quote: Would 3/4" be ok for 10 x 2 1/2" rear drums and front disk (65 two door B-body)? I'd call 3/4" (12/16") rear cylinders undersized. Remember, those cop cars that originally got the 13/16" cylinders as a fix were B-bodies. I don't mean to sound like an evangelist about it, but every time I replaced 15/16" rear cylinders with 13/16" ones, the result was really, really good.
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| Author: | Greg Ondayko [ Tue Jan 23, 2024 1:22 pm ] |
| Post subject: | Re: wheel cylinder sizing question |
Wish I had known this when I had my '78 Apsen I chaed my tail with everything on that car rebuilt master cyl. prop valve etc etc. replaced shocks, tires, etc. Always touchy rear lockup! If I could have spent $26 dollars on some undersized rear cylinders that would have been cool! Now I know. Awesome. |
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| Author: | hank2 [ Tue Jan 23, 2024 4:06 pm ] |
| Post subject: | Re: wheel cylinder sizing question |
Long ago, my dad could have used Dan's fix. He had an ordered 1978 Chrysler Lebaron. Same problem with easy lock up of rear drums. I guess that the Lebaron was essentially a post '67 A body. Despite multiple dealer and other visits, it never was much improved in the 10 years that he owned it. Years later, I read of one other fix which involved fitting a Ford portioning/ metering valve without quite so much initial rear brake bias.Swapping out rear brake cylinders would be cheaper and easier. |
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| Author: | mcnoople [ Thu Jan 25, 2024 10:44 am ] |
| Post subject: | Re: wheel cylinder sizing question |
Back in the 90s mopar action covered the rear wheel cylinder sizing. I couldn't remember which sizes worked best and couldn't find any easy search results for the topic. So I started this thread knowing that someone here would know a good answer. Now when someone searches they have this resource. Thanks for the answers. |
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| Author: | SlantSixDan [ Thu Jan 25, 2024 12:01 pm ] |
| Post subject: | Re: wheel cylinder sizing question |
Quote: 1978 Chrysler Lebaron. Same problem with easy lock up of rear drums. I guess that the Lebaron was essentially a post '67 A body. No, the '78 LeBaron was a C-body, much bigger than an A-body.Quote: Back in the 90s mopar action covered the rear wheel cylinder sizing …with that publication/author's usual delicious blend of truthy-flavored nonsense, made-up wishguesses, baseless claims, and a percentage of whole-grain facts. Part of this complete breakfast; stays crispy and crunchy in milk, yum-yum!
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| Author: | volaredon [ Thu Jan 25, 2024 2:20 pm ] |
| Post subject: | Re: wheel cylinder sizing question |
Wrong again. The 78 LeBron was actually one of the first of the M bodies |
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| Author: | SlantSixDan [ Thu Jan 25, 2024 5:26 pm ] |
| Post subject: | Re: wheel cylinder sizing question |
Quote: Wrong again
Oh! Whatchya mean 'again', what was I wrong about before in this thread? Is this like that preaching thing you were on about the other day?Quote: The 78 LeBron was actually one of the first of the M bodies
Derp, right—I was thinking of the Noo Yawkuh. 
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