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2/05/2023 5:04 PM  #1


Brakes..... rear wheel cylinders

I can't believe I'm posting a brake question! Butt hear goes.........
I have grumbled about a 'low brake pedal' a loooong time.
Welp(thx RPM) I 'MAY' have come up with a fix.
Many many moons ago I went through my brakes and replaced the wheel cylinders (one was leaking)
I can't remember butt......I 'MAY' have installed wheel cylinders with .90625 bore size.
It fit butt.......
There is another cylinder that is .875 bore size that fit Mustangs too!
If I remember my fiziks/physics class...the smaller bore 'should' give me more pedal ! Right?!
"I read".....wheel cylinders from a Full-size/Galaxy were the heavy-duty/"racing" size and were the.....
"hot-set up". (Gotta luv those Hot Rod/Car Craft editors!)
It's been so long....I can't rememerate if I did that swap or not.
BUTT.......the smaller bore wheel cylinders should give me a little more pedal ?!
Anybody???
I just hate to go through the mess if the change would be negligible.
Thankee
6sally6


Get busy Liv'in or get busy Die'n....Host of the 2020 Bash at the Beach/The only Bash that got cancelled  )8
 

2/05/2023 5:08 PM  #2


Re: Brakes..... rear wheel cylinders

Correctissimo , larger cylinder takes more fluid so pedal goes down  further.

Last edited by Rudi (2/05/2023 5:09 PM)


Good work ain't cheap, Cheap work ain't good!   Simple Man
 

2/05/2023 7:20 PM  #3


Re: Brakes..... rear wheel cylinders

As I recall, the stock wheel cylinders on my 4 wheel drum brakes were 29/32” with a 289.

Which is .906”

What front brakes do you have?

 

2/05/2023 9:27 PM  #4


Re: Brakes..... rear wheel cylinders

Nos681 wrote:

As I recall, the stock wheel cylinders on my 4 wheel drum brakes were 29/32” with a 289.

Which is .906”

What front brakes do you have?

I converted to disc front several years ago. Lt......do you think the smaller slave cylinder will net MORE pedal?
6sally6
 


Get busy Liv'in or get busy Die'n....Host of the 2020 Bash at the Beach/The only Bash that got cancelled  )8
     Thread Starter
 

2/06/2023 1:57 PM  #5


Re: Brakes..... rear wheel cylinders

I remember the 78 Granada had a 1/32” larger bore (15/16”…30/32”)  than my 65.

I had considered changing wheel cylinders when I installed the Granada front discs.
Never did…in the past now.

I know the Granada brakes with semi-metallic brakes for Taxi/Police/severe duty work well.
78 Granada calipers are about 2-9/16”….remanufactured ones might be slightly larger.

Then next questions would be about your master cylinder.  (Diameter, single or dual, manual)

 

2/06/2023 7:06 PM  #6


Re: Brakes..... rear wheel cylinders

He has scarebird fronts. Big GM pistons equals lots of travel.
Put the stock size cyls on back with drums that are in spec with new shoes and adjust them properly.
15/16” maverick master cylinder should be fine. 

2” pedal travel MAX


Money you enjoy wasting is NOT wasted money... unless your wife finds out.
 

2/07/2023 6:08 AM  #7


Re: Brakes..... rear wheel cylinders

I looked at the Scarebird offerings briefly for first generation Mustang.

I don’t see the kit available for Mustang, only rotors that have been machined and redrilled bolt pattern.
That’s it.

I also looked up some info about ‘92 S10 pickup brake components on Rock Auto.
Gotta realize that the rear end on an S10 is lighter (2wd or 4wd) than a Mustang.

I noticed a couple of things (92 S10):
1).  Brake master cylinder has 2 different piston sizes (24mm and 36mm)
2).  Rear wheel cylinders are smaller than stock 289 Mustang’s .750” - .875” (24/32” - 28/32”)
3).  Front calipers are 63mm-63.5mm (about 2-1/2”)

This mix of Mustang and GM might be the cause of your pedal level.
Steve’s advice is perhaps the best solution without changing brake components.
Ford brakes would be better.😁

What diameter are your wheels?

Last edited by Nos681 (2/07/2023 6:21 AM)

 

2/07/2023 8:40 AM  #8


Re: Brakes..... rear wheel cylinders

Take a look at this information about your calipers and master cylinder.

https://www.jalopyjournal.com/forum/threads/gm-metric-low-drag-calipers-fixed.1202460/

 

2/07/2023 3:40 PM  #9


Re: Brakes..... rear wheel cylinders

6sally6 wrote:

If I remember my fiziks/physics class...the smaller bore 'should' give me more pedal ! Right?!
BUTT.......the smaller bore wheel cylinders should give me a little more pedal ?!
Anybody???
I just hate to go through the mess if the change would be negligible.
Thankee
6sally6

The smaller bore diameter will require less fluid to activate the brakes, and less pedal travel.  The tradeoff is less pressure exerted to the brakes (due to the smaller bore), and a higher pedal pressure to achieve the same braking force.

 


65 Fastback, 351W, 5-speed, 4 wheel discs, 9" rear,  R&C Front End.
 

2/07/2023 8:44 PM  #10


Re: Brakes..... rear wheel cylinders

Nos681 wrote:

I looked at the Scarebird offerings briefly for first generation Mustang.

I don’t see the kit available for Mustang, only rotors that have been machined and redrilled bolt pattern.
That’s it.

I also looked up some info about ‘92 S10 pickup brake components on Rock Auto.
Gotta realize that the rear end on an S10 is lighter (2wd or 4wd) than a Mustang.

I noticed a couple of things (92 S10):
1).  Brake master cylinder has 2 different piston sizes (24mm and 36mm)
2).  Rear wheel cylinders are smaller than stock 289 Mustang’s .750” - .875” (24/32” - 28/32”)
3).  Front calipers are 63mm-63.5mm (about 2-1/2”)

This mix of Mustang and GM might be the cause of your pedal level.
Steve’s advice is perhaps the best solution without changing brake components.
Ford brakes would be better.😁

What diameter are your wheels?

I do not see a comparison of the drum diameter and width of the S-10 vs Mustang, both of which would weigh in on the wheel cylinder area requirement.


Money you enjoy wasting is NOT wasted money... unless your wife finds out.
 

Board footera


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