Topic: Better Brakes

[Jeffy]

Another tidbit.  My rear cylinders changed from 13/16" to 7/8" by going from 2.5"x9" to 2.5"x10".

[sharpxmen]

Another tidbit.  My rear cylinders changed from 13/16" to 7/8" by going from 2.5"x9" to 2.5"x10".

are you locking the rear more (or easier) than before?

the one i have (not installed yet) looks exactly like the top one (including the master) - is that the 95.5 YJ? for whatever reason i thought was an early TJ one.

Ok, I think I found a problem I'll have with the TJ booster.  The YJ has that big spacer to keep it away from the clutch.  The TJ does not have that and is bolted to the firewall.  If I used a TJ booster, I'll have to cut and weld an extension to the booster.  Problem is I don't have a welder and I'm not sure if it would be worth it compared to buying a 1995.5 booster.  ARGH!

would you be able to use your old spacer for that? you would have to extend the rod however but you could use your old one and i'm thinking maybe cut and thread both ends and use a hex bar to join them.

BTW: from what I've read the TJ/Dakota master is 1" while the YJ is 15/16".

problem is that when you go to a larger diameter master you need more force/pressure at the pedal (if you keep the stock calipers) - i think i'm going to stick with the stock one unless the pedal is going all the way down to the floor and maybe upgrade if i ever end up with 2 piston calipers or hydroboost (unlikely) - not sure if the dual diaphragm booster would give enough extra pressure for the larger diam master which is what i fell i am lacking right now (no matter how hard i press the pedal the front never locks up unless it's raining).

[Jeffy]

are you locking the rear more (or easier) than before?

the one i have (not installed yet) looks exactly like the top one (including the master) - is that the 95.5 YJ? for whatever reason i thought was an early TJ one.

A TJ unit will not have the spacer to attach it to the firewall as TJ boxes are bolted straight to the wall.

would you be able to use your old spacer for that? you would have to extend the rod however but you could use your old one and i'm thinking maybe cut and thread both ends and use a hex bar to join them.

Yes you can reuse that spacer BUT you need to extend the rod as well.  Problem is I don't have the tools to do it so that makes it less practical for me.  Basically you can cut and weld a sleeve in there or else weld a all thread and then a collar so you can adjust it.  If you have a die, you could thread both sides and put a sleeve on there as well.

problem is that when you go to a larger diameter master you need more force/pressure at the pedal (if you keep the stock calipers) - i think i'm going to stick with the stock one unless the pedal is going all the way down to the floor and maybe upgrade if i ever end up with 2 piston calipers or hydroboost (unlikely) - not sure if the dual diaphragm booster would give enough extra pressure for the larger diam master which is what i fell i am lacking right now (no matter how hard i press the pedal the front never locks up unless it's raining).

Thing is my rear brakes aren't stock, at least not stock for a YJ.  They are 7/8" (10" drums) vs 13/16" (9" drums).  I know my rears are locking up, which is forcing the fronts to do even more work.

From my research, you might want to go with a smaller MC.  Smaller MC will produce higher pressure.

[sharpxmen]

A TJ unit will not have the spacer to attach it to the firewall as TJ boxes are bolted straight to the wall.

i guess it's a late YJ then and should be a straight bolt-on - for some reason i remember that the threads on the master were different than mine, do you know anything about that?

[95 Lowbuck]

According to Jeep and my VIN #,
I have a '95 built to '96 specs.
I have the small V.B. and steel M.C.
Was this a late change to the larger setup on the '95s ?
I have also heard that the Cherokees also have the larger setup
and is a direct bolt up but no clue about the prop. valve.

[oldjeep]

oldjeep's doesn't look like a dual, looks exactly like mine. i also have one off a late 95 TJ (or 96) in the garage and it's about twice the thickness of the one i have on now and i was told is the one with dual diaphragm - it came with the master with plastic reservoir on it, i was not aware there are clearance issues so i guess i'll have to figure something out when i'll make time to install it.

MIne is a stock single diaphram 94 booster with the Marquis master cylinder.  Stock brakes up front with O'reilly house brand pads, 8.8 disc in the back with the same pads.  Plenty to lock up and skid 35's on dry pavement.

[oldjeep]

What is the advantage running the Grand Marquis MC? I have seen a few people mention they have switched to them.
I have also heard of people running a MC from a Corvette, not sure what year.

The marquis MC is only an advantage if you have 4 wheel disc brakes.  The Marquis had 4 wheel disc and works great with the stock D30 fronts and 8.8 discs which are all about the same size as the stock brakes that the Mercury had.  Using the Marquis MC on a disc/drum setup would be a mistake - you would loose the pressure that the drums require in favor of the volume that discs need.

[Jeffy]

i guess it's a late YJ then and should be a straight bolt-on - for some reason i remember that the threads on the master were different than mine, do you know anything about that?

I know the YJ lines are 5/16" for the rear and 1/4" for the front.  From what I've been getting the TJ lines are different then the YJ's.  I haven't checked to see what size their are.

[Jesse-James]

MIne is a stock single diaphram 94 booster with the Marquis master cylinder.  Stock brakes up front with O'reilly house brand pads, 8.8 disc in the back with the same pads.  Plenty to lock up and skid 35's on dry pavement.

What do you use for a prop. valve, if any?

Edit: And what year range Marquis?

[oldjeep]

What do you use for a prop. valve, if any?

Edit: And what year range Marquis?

78 Marquis with 4 wheel disc - no idea what the range is.

Stock prop valve with the o-ring removed from the piston.

[Jeffy]

So I did a bit more research and a bit more thinking.  TJ's use the larger master and the booster while still having the same brakes (stock) as most YJ's. (except pre-91's)  From what I've read the pressure goes down as the volume increases.  The larger master gives you the false sense of firmed brakes because they have less pressure for every inch of travel.  The exception is if you increase the booster pressure.  So as long as you increase the booster pressure along with the larger master, it should be OK when using with stock brakes.

[dwtaylorpdx]

The catch is that if you use the booster to increase the pressure
on the master cylinder the pressure ramp in the system becomes
abrupt, so the brakes become grabby if you overdo it.

I'm running the same up sized rear brakes from a 87 Cherokee,
not only is the diameter larger the shoe is 2" instead of 1.75"

I've thought about dropping the booster completely and
using dual Wilwood cylinders instead. With each one sized
to match its side of the brake circuit and it would give me a
biasing adjustment as a bonus.

Dave

[Jeffy]

The catch is that if you use the booster to increase the pressure
on the master cylinder the pressure ramp in the system becomes
abrupt, so the brakes become grabby if you overdo it.

I'm running the same up sized rear brakes from a 87 Cherokee,
not only is the diameter larger the shoe is 2" instead of 1.75"

I've thought about dropping the booster completely and
using dual Wilwood cylinders instead. With each one sized
to match its side of the brake circuit and it would give me a
biasing adjustment as a bonus.

Dave

Well, I would think that the TJ setup would be good for someone who has a stock setup.  It might even work for us as well.  From '84-'90 the normal rear drums were 9"x1.75", with the exception for the D44 which is 10"x2.5".  In 1991, the rear brakes were changed to 9"x2.5" on the D35c.  I'm not sure what the brakes were for the 8.25" though.

[chardrc]

From '84-'90 the normal rear drums were 9"x1.75", with the exception for the D44 which is 10"x2.5".  In 1991, the rear brakes were changed to 9"x2.5" on the D35c.  I'm not sure what the brakes were for the 8.25" though.

would the change in drum size go along with the introduction of the c-clip to the d35c or on the actually year... IIRC the c-clips where a mid year (1990) introduction) Faq says clips where introduced in 91 but my 1990 has c-clips which is the bases of my thinking not that it maters that much....

[Jeffy]

would the change in drum size go along with the introduction of the c-clip to the d35c or on the actually year... IIRC the c-clips where a mid year (1990) introduction) Faq says clips where introduced in 91 but my 1990 has c-clips which is the bases of my thinking not that it maters that much....

Yes, the changed correspond with the model update.  1990 was the transition year BUT 1991 is the production year.  This means that they started building the '91's in 1990 and so late model 90's could very well see some '91 changes.