Master cylinder choices
Oct 4, 2023 | 08:13 AM
#1
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Joined: Jun 2012
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From: San Jose, CA
Master cylinder choices
My 88 22r DLX pickup is heavily loaded (4600+ lbs). It didn't start out with a 1-ton rear gear but I swapped that in. Wheels and tires are fairly normal.
For regular stop and go braking is good. For hard stops, braking performance is only fair. I have to murder the pedal, but it does stop. No pulling, skidding, bad smells, or noticeable fade. (I allow generous stopping distances, as if I'm driving a semi.)
OE master cylinder and Brake Power booster is new, as are calipers & pads, drums & shoes. Pressure bleed done recently.
Rear proportioning valve is new and set for maximum rear brake pressure. (still not getting a lot of heat at the rear during hard braking)
Here's my question: I believe a 1-ton brake master cylinder is available for my pickup. What I'm wondering is, what makes it different from stock, and how would the differences affect braking.
Is it a different bore size?
Is the bore size for the front brakes different than the bore size for the rears?
Is braking performance of pickups like mine typically lackluster?
Your insights much appreciated.
For regular stop and go braking is good. For hard stops, braking performance is only fair. I have to murder the pedal, but it does stop. No pulling, skidding, bad smells, or noticeable fade. (I allow generous stopping distances, as if I'm driving a semi.)
OE master cylinder and Brake Power booster is new, as are calipers & pads, drums & shoes. Pressure bleed done recently.
Rear proportioning valve is new and set for maximum rear brake pressure. (still not getting a lot of heat at the rear during hard braking)
Here's my question: I believe a 1-ton brake master cylinder is available for my pickup. What I'm wondering is, what makes it different from stock, and how would the differences affect braking.
Is it a different bore size?
Is the bore size for the front brakes different than the bore size for the rears?
Is braking performance of pickups like mine typically lackluster?
Your insights much appreciated.
Edited for font color - chose black. Doesn't seem to matter on my screen
Last edited by MichaelKLerner; Oct 12, 2023 at 06:24 AM. Reason: Edited for font color
Oct 12, 2023 | 06:19 AM
#3
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Joined: Jun 2016
Posts: 718
Likes: 189
From: Florida
@MichaelKLerner
You need to edit your post, probably for font color, because your text is showing up as blank. I was only able to read it by holding left-click down & highlighting it on my screen.
Yes, the bore sizes between the 1/2 ton & 1 ton/$WD units are different. The 1/2 ton is 0.875" & the 1 ton is 0.938". By the math, that means the 1 ton cylinder is pushing about 7% more fluid volume (roughly speaking).
Did you also bleed the rear proportioning valve before you bled the rear brakes? If not you may have a lil bit of air trapped in the valve, causing the system to not be balanced correctly.
You need to edit your post, probably for font color, because your text is showing up as blank. I was only able to read it by holding left-click down & highlighting it on my screen.
Yes, the bore sizes between the 1/2 ton & 1 ton/$WD units are different. The 1/2 ton is 0.875" & the 1 ton is 0.938". By the math, that means the 1 ton cylinder is pushing about 7% more fluid volume (roughly speaking).
Did you also bleed the rear proportioning valve before you bled the rear brakes? If not you may have a lil bit of air trapped in the valve, causing the system to not be balanced correctly.
Oct 12, 2023 | 06:43 AM
#4
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Joined: Jun 2012
Posts: 122
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From: San Jose, CA
My analysis
After hours of reading, this is what I've come up with -
My rear brakes are weak exactly because are heavy duty (swapped in a 1-ton rear end, replace original base model rear end) but retaining my base model m/c. Therefore I'm not pushing enough fluid to the rears. Based on the temp of the rear drums, I'm getting minimal rear braking pressure.
Rear proportioning valve is set to max.
All components are in new condition.
Pressure bleed has been performed by an experienced mechanic.
My rear brakes are weak exactly because are heavy duty (swapped in a 1-ton rear end, replace original base model rear end) but retaining my base model m/c. Therefore I'm not pushing enough fluid to the rears. Based on the temp of the rear drums, I'm getting minimal rear braking pressure.
Rear proportioning valve is set to max.
All components are in new condition.
Pressure bleed has been performed by an experienced mechanic.
Oct 12, 2023 | 07:37 AM
#5
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Joined: Dec 2021
Posts: 334
Likes: 52
From: nor cal
All I was seeing was a blank screen also, but...........
A LOT of experienced mechanics do not know about the rear valve having a bleeder valve on the top of it, but given the context of the post a larger bore master cylinder I'm sure will correct the problem. Maybe one off of a Landcruiser..they have a 1'' bore
A LOT of experienced mechanics do not know about the rear valve having a bleeder valve on the top of it, but given the context of the post a larger bore master cylinder I'm sure will correct the problem. Maybe one off of a Landcruiser..they have a 1'' bore
Last edited by mechkw; Oct 12, 2023 at 07:39 AM.
Oct 12, 2023 | 02:20 PM
#6
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Joined: Dec 2011
Posts: 608
Likes: 28
From: Spokane, Wa
I'd go with the early 90's V6 4Runner master. 1" bore and set up for disc front and drum rear. The Landcruiser ones are set up with a residual valve in both for 4 wheel disc brakes (at least the year I got).
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