I wanted to post this to the org before ordering anything, to get everyone's feedback.
On my 2004 Sunfire Without ABS, I have the Wilwood front brake kit with the SSBC rear disc conversion. I cannot find any Residual Pressure Valves on the rear lines, and to my understanding, some J's don't have them. The reason for this post is that under braking, the rear brakes will lock up before the front. I have read that two other J's on the org have had accidents due to this issue. For the safety of everyone on the road, and myself, I want to do this right, and I want to thank all of you in advance for your help.
I am going to buy a brake pressure gauge and take the reading at all four wheels. I've seen the "ideal" PSI numbers for our cars posted on the org in the past, but I haven't been able to find it again. What pressures should I be targeting?
I will need to install proportioning valves to dial down the rears. My understanding is that the lines coming out of the Master Cylinder going into the distribution block on my Sunfire output in an X pattern, so that one front and one rear are on each system. This means I will need to install two proportioning valves, one on each of the lines going to the rear. What is the ideal way to mount them so they will be secured in place? (in the engine bay)
For anyone with the Wilwood front brakes, did you feel a softer pedal after the install? Have you gone with a larger Master Cylinder?
Is there anything that you think I should be considering? I'm always welcome to different perspectives. Has anyone else experienced the rears locking up before the fronts with other big brake setups (BAER, etc) on non-ABS J bodys?
Thanks again for the help!
After a bit more research, I don't feel completely comfortable with two separate proportioning valves controlling each of the rear lines, even if I get them pretty close to the same adjustment.
It seems to come down to replacing the master cylinder or distribution block. Which one of these are responsible for the pressure to the rear?
contaminated brake linings can cause premature rear brake lock up. Weak brake return springs can cause this also on systems with conventional return springs. Since you have an 04 it will have one spring sothe problem is probably not the spring.
forget that post, I just re-read you post. My comment doesn't apply for your set-up.
OK, lets start this off right.
You only need a residual pressure valve, if the master cylinder is located below the caliper.
This is a common track car setup, not an OEM setup.
You will want an "Adjustable proportioning valve and distribution block".
You will not be able to dial down the rears, the pressure is coming right from the master cylinder.
Instead you will need to dial up the fronts.
I used this exact model.
CPP Adjustable Proportioning And Distribution Block
I have 13" fronts, and 12.5" rears.
They are also compiled with a 1.375 bore master cylinder, because my whole system is now 10 piston, compared to the OEM 2 piston system.
I needed to move more fluid, that is why my master cylinder is bigger.
I have wilwood 4 piston fronts, and wilwood single piston rears with the integrated ebrake.
I hope this helps
Thank you Bobby. How stiff does your pedal feel after installing that 1.375 master cylinder?
Would that Adjustable Proportioning and Distribution Block allow me to retain the split diagonal system design?
Thanks for the post prime... it might help someone!
My pedal is very stiff, I would say I have about .25-.375 of travel for full engagement.
Its like a brand new car, with new brakes.
You know how you need to get used to a new car ..... its like that for a couple days.
I used speed bleeders also, and went thru a full can of fluid, to make sure the whole system was completely bled.
I replaced everything with s/s lines and fittings.
Im not sure what you mean about the split diagonal design?
Sounds like a nice setup you have.
Quote:
HPBooks Brake Systems: OEM & Racing Brake Technology by Mike Mavrigian & Larry Carley (available online from Google Books) says:
With front-wheel drive, the hydraulic system is usually split diagonally with the left front and right rear brake sharing one circuit, and the right front and left rear brake sharing the other circuit. This is necessary because the front brakes (which do more work) are also the drive wheels. If both front brakes shared a common circuit and failed, the rear brakes alone might not be able to stop the vehicle safely. So splitting the system diagonally means at least one front brake will remain operational should one side of the system fail.
It would certainly make my setup simpler to do away with the split diagonal design for a front-rear split design, but I am uncomfortable switching the system away from a diagonal split because I've experienced a master cylinder failure in the past. I'm researching now if they make the adjustable proportioning valve distribution blocks for FWD vehicles.
There are some non-ABS FWD cars which had rear disc brakes from the factory. (the first gen neon had this option, as far as I've read) I am curious if the reduction of pressure to the rear was handled completely with the distribution block. It would be a fixed proportion, but it it were right, perhaps I could bolt it up to my Sunfire.
Well you always have your ebrake as back-up.
Im not sure how the non ABS vehicles are set up.
But I deleted my ABS, ran the front LH and RH individually.
I then ran one line to the rear, and tee'd to the LH and RH by the axle.
Do you know why your rears are locking first? If you're using the factory distro block and MC, you shouldn't be having that problem unless the distro block or a line is damaged somehow.
.
James,
This happens because the rears need to build pressure first iirc, seems like I learned this in the ASE A-5 testing.
I am using the original factory non-ABS distribution block and stock master cylinder (which was replaced in 2006 by the dealership, under warranty, when I still had the factory brakes). There are no leaks, and both lines to the rear seem good, no damage. The lockup is happening on both rear sides.
Jason, I've read that... I wonder if our distribution blocks are set up this way.
I ordered a brake line pressure gauge and it should get here next week. I'll take some pressure readings and post them up here. I remember reading on the org that we want something like 1200psi to the fronts and 900psi to the rears... but I don't remember the post exactly... it was years back and I can't seem to find it in the archive.
I talked with SSBC and Wilwood and the consensus is to take the pressure readings and go from there. I'll let you guys know what I find, probably be toward the end of the next week.
jason norwood wrote:James,
This happens because the rears need to build pressure first iirc, seems like I learned this in the ASE A-5 testing.
Hmmm.... I see your point, but no matter which end builds full pressure first, it will still only build a maximum amount (whatever the proportioning is set to). As long as the rears have less overall braking effectiveness (based on pressure and grip surface), they should never lock before the fronts. That's why I think it may have something to do with the distro block.
I'm interested to see what the pressures end up being.
.
Bobby Higgins wrote:OK, lets start this off right.
You only need a residual pressure valve, if the master cylinder is located below the caliper.
This is a common track car setup, not an OEM setup.
You will want an "Adjustable proportioning valve and distribution block".
You will not be able to dial down the rears, the pressure is coming right from the master cylinder.
Instead you will need to dial up the fronts.
I used this exact model.
CPP Adjustable Proportioning And Distribution Block
I have 13" fronts, and 12.5" rears.
They are also compiled with a 1.375 bore master cylinder, because my whole system is now 10 piston, compared to the OEM 2 piston system.
I needed to move more fluid, that is why my master cylinder is bigger.
I have wilwood 4 piston fronts, and wilwood single piston rears with the integrated ebrake.
I hope this helps
What size is the stock Jbody master cylinder??
Jason
99 Z24
LG0/LD9 for Life
10 Year Bash Veteren
James (Canuck) wrote:I am using the original factory non-ABS distribution block and stock master cylinder (which was replaced in 2006 by the dealership, under warranty, when I still had the factory brakes). There are no leaks, and both lines to the rear seem good, no damage. The lockup is happening on both rear sides.
Jason, I've read that... I wonder if our distribution blocks are set up this way.
I ordered a brake line pressure gauge and it should get here next week. I'll take some pressure readings and post them up here. I remember reading on the org that we want something like 1200psi to the fronts and 900psi to the rears... but I don't remember the post exactly... it was years back and I can't seem to find it in the archive.
I talked with SSBC and Wilwood and the consensus is to take the pressure readings and go from there. I'll let you guys know what I find, probably be toward the end of the next week.
The rears would lockup on me when I had the stock fronts and SSBC on the rear. I figured the rears was locking up due to weight transfer off of the rear wheels. I did not notice it when I switched to my Precision/Wilwood fronts.
Jason
99 Z24
LG0/LD9 for Life
10 Year Bash Veteren
I'll ask Darren to Chime in on this one... he had this set up when he had his car.
James Cahill wrote:jason norwood wrote:James,
This happens because the rears need to build pressure first iirc, seems like I learned this in the ASE A-5 testing.
Hmmm.... I see your point, but no matter which end builds full pressure first, it will still only build a maximum amount (whatever the proportioning is set to). As long as the rears have less overall braking effectiveness (based on pressure and grip surface), they should never lock before the fronts. That's why I think it may have something to do with the distro block.
I'm interested to see what the pressures end up being.
.
IIRC drum brake systems generally need more pressure to function than disc brake setups. Since the piston area is greater in a caliper than a wheel cylinder. So using a prop valve for a drum brake rear car on a disc brakes may cause locking up. Anyone who does disc brake swaps on EK Civics recommends switching to a prop valve from a disc brake equipped car. Though I never had issues with brake bias when I ran rear discs on the Sunfire.
This is going to be a long update. I will continue to post my progress, and as much information as I find, until I find a solution... in the hope that it may help somebody, for the sake of safety. Here's what I've found so far...
The brake pressure gauge kit that I used is SSBC part # A1704 ...it comes with adapters to fit different thread sizes, including the SSBC rears and the Wilwood fronts. Note, the adapter which fits the Wilwood caliper will not fit on the outermost banjo bolt/bleeder due to interference with one of the caliper bolts. No problem... mount the gauge to the innermost banjo bolt/bleeder on the Wilwood caliper (the one closest to the engine) and you will be fine.
The results of the brake pressure test
The rear was able to generate a maximum of 900psi. The front was able to generate a maximum of 2500psi. ...these numbers are theoretically in a good range. My conclusion, in this case, pressure is a factor, but not the smoking gun I expected. It led me to consider a few questions...
-
larger factory rear drum brakes? - I believe it was starting in 2003 that J-bodys were fitted with a larger drum brake setup than previous years. (my 2004 certainly had the larger drums from the factory)
Are the 1995-2002 J-bodys running a lower brake pressure to the smaller rear drums? Jason commented that his 1999 Z24 with SSBC rear/Wilwood-Precision front setup is not having the issue that I am having. Is the 1999 non-ABS brake distribution block different than the 2004 non-ABS brake distribution block? If so, it should be an easy swap. ...my brake distribution block has a few markings but I can't find a part number. On the driver's side "B12 D", on the front, "4 B 2", also a "7". If anyone with a non-ABS 1995-2002 distribution block could take a look at theirs, or knows what these markings mean, it might be a big help!
-
air in front brake lines? - If there is air in the front lines, but not in the rears, it may cause the rear brakes to lock first. To ensure there was no air in my system, I used a pressure bleeder. Motive brand, PowerBleeder, model # 0101. There was no air in my system. I'm including this in case it helps someone. It was my first time using a pressure bleeder and I highly recommend it, if nothing more than the peace of mind it provides.
I came across this in my reading and I believe it is very important to note...
Always use the top two banjo bolts/bleeders on the Wilwood caliper,
never the two bleeders on the bottom, which only exist because the orientation of the caliper is designed to be flipped, depending on application.
-
piston size of SSBC rear caliper, considering not using SSBC front kit? - It's logical that my choice to keep Wilwoods on the front instead of going with SSBC's front kit is at issue. There are differences... Wilwood uses a 4 piston caliper with a 12" rotor, SSBC uses a 2 piston caliper on the front with your choice of a 12" rotor, or a 13" rotor. I imagine the 13" SSBC front kit may be a good match for the 12" rotor with single piston caliper on the rear... but that'd be an expensive change to make, considering I could just keep the front Wilwoods and reinstall the factory drums... as far as safety is concerned.
Solutions
- put factory drums back on rear end (free)
- upgrade front brakes (expensive)
- adjustable proportioning valve - Can change the brake lines from a diagonally split system to a front-rear split system and use one proportioning valve.... or maintain the diagonally split system and run two proportioning valves, one for each of the rear lines.
- swap brake distribution block to one that has a lower pressure to the rear
Pressure isnt the only thing to look at. Multiply your line pressure by the area of the piston in sqare inches and thatll give you an idea how the actual force on the rotor relates front and rear. Its not perfect because the rotor diameter will still play a role.
As far as going to a front/rear split vs a diagonal. If the car is used on the street Id stick with the diagonal split and use separate proportioning valves to dial down the rear. The purpose of the diagonal split is leave you with a reasonable amount of stopping power if you lose pressure in one of the front circuits. If its a track car only go front/rear.
This will be a quick update because it might help someone who comes across this. The car has been in the garage for half a year. I have not been driving it but I do intend to get back to the brake problem this spring or summer. After my last post, I started researching to find a GM car that had 4 wheel disc non-ABS brakes from the factory. If the problem was the distribution block putting more pressure to the rears for the factory drums than is needed for the discs, I was thinking that GM would have engineered a different system for a car that had 4 wheel disc non-ABS from the factory. I found this in the 2003 Impala LS. Brake Code J65. Non-ABS 4 wheel disc. The master cylinder is a 1" bore, as opposed to the Sunfire's 7/8" bore, but with the large discs I have front and rear, 1" might be a good upgrade. It retains the diagonal split brake line plumbing, and should bolt on. As I recall, this system does not use a separate distribution block, so it will eliminate that from the equation. The only concern will be the size of the piston in the SSBC rear calipers. I will post again in the future, after my testing.
