Master cylinder... 1 1/32" vs 1 1/8"

[Nacho-RT74]

I can' recall which one my car has actually, but If it has the 1 1/32"... Will the 1 1/8" a noticeable upgrade on braking power ?

[Kern Dog]

My understanding is that a larger bore requires MORE pressure from your foot to stop the car, but the pedal travels less. A smaller bore travels further to the floor but is easier to get the car to stop.

[Nacho-RT74]

Ok... More ppl agreed in this ?

Now another question: just for curiosity I have being searching stock 4 holes master cylinder with the large bore on rockauto, but it seems the large bore are really 2 holes to booster? i can see large bore on jegs to stock 4 holes thought. Is this Jegs piece a regular stock replacement or some HiPo aftermarket piece made for upgrades ?

[Charger-Bodie]

http://www.ebay.com/itm/321769979944?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

[Nacho-RT74]

Yes I saw that one, but I have serious doubts about replacement kits locally for  1 1/16" bore ( seals or pistons )

Beside that, would like to find it on a stock replacement price rate, LOL.

[John_Kunkel]

Disc Brake MC's

[Nacho-RT74]

Ok, I'm seeing those earlier units with 1 1/8" bore... They are HUGE reservoirs!!! LOL.

Are they same outputs sizes and threads than laters ?

[John_Kunkel]

AFAIK, all have the same thread size on the line fittings.

Keep in mind that a lot of the 1 1/8" MC's are mated to dual-diaphragm boosters and that reduces the leg effort that is normally associated with big bore MC's.

[b5blue]

I just installed 1 1/32 master with the 11 3/4 slider disk swap. Brake is fine, even with manual brakes. (Bought new not rebuild from Rockauto.)

[Nacho-RT74]

ok so is true about the bigger bore makes more leg effort... ok, will despite that idea then.

[John_Kunkel]

An example, with 100 lbs. of leg pressure, a 6-1 pedal ratio and no boost:

A 15/16" MC will make 1058 PSI line pressure

A 1 1/32" MC will make 717 PSI line pressure.

A 1 1/8" MC will make 604 PSI line pressure.

[Nacho-RT74]

Nice comparision... thanks!!!

However, I think volume would make its effect of course, because allong with the pressure, still needs an ammount of fluid volume to fill calipers moving the pistib, and the rear cilinders action.

[b5blue]

From researching manual brakes master cylinders and some testing, the volume is accounted for with travel. I tried a true manual disk brake master from 3rd gen B body. Smaller bore, longer travel and did not like the longer travel at all. (Just to save a bit of foot pressure.) I've a 1 1/32nd from 75 year up working fine now with manual so I'd think with power disk 1 1/8 may give less foot travel and better "feel". (Power boost being almost too strong on most Chrysler.)

[John_Kunkel]

Yes, increased pressure comes at the cost of extended pedal travel but, keep in mind the pedal ratio. Manual brakes typically have a pedal ratio of 6-1 while the power brake pedal ratio is 4-1. Lower pedal ratio means less pedal travel.

[Nacho-RT74]

one question abour Rick's master cilinder auction ( the one with 1 1/16" )

it was really a stock piece ? never have found that info or kits available for that bore.

There is one supossely Mopar original remanufactured MC being sold around with this bore per seller answer to my question:

"looks like 1 1/16" ( that was the answer to the question I sent )

[1974dodgecharger]

I use a 85 diplomat master cylinder  its 1 1/32 bore size....works great got it because it accepted the shaft linkage.