Hey guys, still deliberating about this. Read all I could find on the internet, and a lot of guys talk about Town cars and such, but they never came with rear discs, so they are kind of out of the question (I wonder how safe those cars are with people running 4 wheel discs with them). So IS there an affordable < 1" M/C for 4 wheel discs that will fit? I'm running SN95 right now as I said (1.125? Or is it 1/16), so I'm wondering if 1" will make any difference, and if 15/16 will be too small..
15/16 wont be too small check out my post its probably the last one.
THanks for the quick responses guys! Well my dilemma is (Can't remember if I wrote it in this thread) I have power brakes (not sure if that will effect pedal travel too much), using 68 fronts, with SN95 rears, and a 94 base model SN95 master, which is only 1 1/16, so I'm not sure if going down to a 1" bore will make any difference.
Booster seems to be operating fine, or at least, it's holding vacuum fine. Pedal is correct and all that jazz, but the pedal is rock hard with the engine off (obviously) and not much better with the engine running. Even going on gravel at 15mph or so, you have to hammer to lock up the fronts, and locking up the rears won't be happening, even with the prop valve adjusted all the way to the rear (I know it's not ideal, but I was just seeing if they were working at all) so I can't think of any other problem except the MC.. But it's only 1 1/16, so I'm a little confused on what to do now!
'68 vette M/C is 4xdisc and 1" bore and it fits, that could be an option. The 84 LTD M/C is for rear drums, I wouldn't run it for all the tea in china.
I very strongly suspect that 15/16" would work...1 Owner or Shaun would probably be the people that could verify that.
The difference between 1" and 1.0625" might be fairly noticeable, the 1.125" M/C seems to be VERY noticeable over a 1" unit.
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The squirrels in my head have spoken.
Cobra 5.0L & AOD swap, here we come.
rockauto.com sell 1inch bore master cylinder for 93 cobra for 58.00 part no. m390125 made by dorman
Hey, that part number says raybestos and it's $80 or so.. THere is another one for cheaper, but doesn't say if it's remanned, or what.. So you think a step to 1" will be good, or should I drop to 15/16?
Thunderbird Supercoupe? Seems have to 15/16 M/C, and same dimensions as SN95, so it seems.. THink it's too small?
My concern is, with an SN95, the front brakes are very similar, and the rear brakes, are well, what I'm using. I'm using a booster, so why is my pedal travel so much harder than an SN95?
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My concern is, with an SN95, the front brakes are very similar, and the rear brakes, are well, what I'm using. I'm using a booster, so why is my pedal travel so much harder than an SN95?
I can't remember; have you checked the distance ratios on the pedal (the distance from pedal to fulcrum to actuating rod) compared to the SN95? IOW, do you have it set up so the mechanical advantage of the lever is about the same as the SN95?
Well 68's are 2.4", no? Which I understand is smaller, but..... Didn't think it would be that noticeable, so much so that I have to undersize my master by several sizes. So you guys think 15/16, or 1"?
Still not sure why my rears don't seem to have much if any pressure though!
I did the sn 95 conversion on my 93 and had the same problem very hard pedal and didn't lock up. So I replaced the front calipers with 84 svo. The spec on the cobra master 25.4mm (1.0inch) mustang 27mm (1.06inch). I would try the cobra master.
The shop manual could be wrong on the cobra master I though they were 15/16inch
See, I thought since the 68 pistons are actually bigger than the SN95 fronts, that the bigger M/C (1 1/16) wouldn't matter.. BUT, I guess not.
So I posted this in the other section but no replies. Anyone know if a T-bird supercoupe M/C is the same length as the SN95 style, and, if I can just plug up two ports (It has 4, for some reason).
The 84 Crown Vic MC was recommended by Ford Motorsport for rear wheel disc conversions for Fox Mustangs (which consisted of Thunderbird Turbo Coupe components IIRC).
Apart from the residual pressure valve in some drum MC's, there's not really a difference between disc and disc/drum master cylinders. The bowls should be large enough and discs may require more volume (so that you don't run out of fluid when the pads wear and the pistons are sticking out more) than drum brakes.
You could even check how much volume you need:
the amount of fluid required in the bowl to compensate to wear the pads down to the metal = pad thickness x 2 x piston area x 2 brakes
In case of SN95 brakes: 5/16 (guess) x 2 x 1/4 x pi x 1.5 x 1.5 x 2 = 2.2 cubic inches = 35 cc. I don't have an MC in front of me, but say that the bowl is 2x2", then the fluid level would only be reduced by a little over half an inch if you wear the pads down to the metal.
I'm not saying that disc/drum MC's are fine for all rear disc brake setups though. MkVII/SVO and also Versailles rear calipers for example, have large 2.125" pistons (twice the area), so they may need a bigger MC.
Are you sure that your caliper pistons are the same diameter as sn95. 1994 mustang caliper cylinder bore is 66mm (2.60 inch).
I just looked it up at rockauto. The calipers were listed as 2.6" bore, but the (separate) pistons as 2.369" diameter (same as 68). I guess both are correct but it's the piston size that counts.
Quote:
Originally Posted by JohnnyK
Well 68's are 2.4", no? Which I understand is smaller, but..... Didn't think it would be that noticeable, so much so that I have to undersize my master by several sizes. So you guys think 15/16, or 1"?
Still not sure why my rears don't seem to have much if any pressure though!
Remember that it's the area that counts. The area of a 1 1/16" MC is 13% larger, not just 6%. The same is true for the calipers. Although they're the same in this case, going from 2.375 to 2.6 is a 20% change in area.
The SN95 calipers are actually rather small. The fronts have 2.5 times the area, or 71% of the total piston area. The static front/rear weight balance is about 56/44, so you need to brake pretty hard before you reach the point were the rear brakes are bigger then they need to be. To be precise, braking at .75G results in a 71/29 weight balance.
English, man! So the 68 pistons are 2.377 from what I found out (On rockauto, so who knows the discrepencies) while the sn95's are 2.359.. So you'd think I'd have more pedal travel, not less.
So you're saying the 1 1/16 is 13% larger than the 15/16's, or the 1". I assume the 1", but.. JUst not sure if going down a 1/8" will be too big of a jump, and the pedal will wack my wiring harness that I accidently routed behind the brake pedal.
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So the 68 pistons are 2.377 from what I found out (On rockauto, so who knows the discrepencies) while the sn95's are 2.359.. So you'd think I'd have more pedal travel, not less.
