Doing a ton of work on my new 1991 Honda Civic SI hatchback, and am interested in doing a rear disc brake conversion. Just got done looking through the FAQ posts regarding this conversion...and have some questions that those walk-throughs either didn't answer at all, or didn't answer clearly.

1. What all do I need from a DA/DB to do this conversion?

2. Will I need to buy rubber(or SS) caliper lines? If so, what car should I order them for? Or can I just re-use the civic lines or DA/DB lines?

3. Will a booster and/or prop valve upgrade be necessary if I'm only converting the rear to DA discs?

4. Is it 100% confirmed that I don't have to drop the fuel tank on my hatch to do this conversion?

5. I just ordered a rear camber kit for this car, that adjustable dog-bone that goes between the hub/trailing arm assembly and the car. Will this fit the DA hub assembly, or do I have to order another new kit for a DA?

6. Do I need the DA LCAs as well, or can I re-use the LCAs on the civic? In one of the FAQ walk-throughs, going by the photos it looks like he used the DA LCAs so I'm not really sure.

Thanks.

 

1. the rear hub, including calipers...ebrake cable from crx si
2. you don't have too, but you might as well get the complete front and rear set. get it for you 91 si.
3. YES! i would upgrade the ppv and mc/bb, again you don't have to, but i would!
4. YES IT IS 110% that you don't have to drop the tank.
5. YES it will fit, don't have to order for the DA

 

1. I was under the impression that I needed the DA parking brake cables...do they have to be for the crx si, or would either work?

2. I read in one of the walk-throughs that my brake lines won't work with this conversion, that I need crx si lines or DA lines. Maybe I misread it?

3. Is there any real downside to keeping my oem prop valve and booster with this conversion? The master cylinder is getting replaced this week because it's bad, just getting a new oem one. I really don't want to replace the prop valve and booster if I don't absolutely have to.

4. Awesome, that'll save me a lot of time and headaches.

5. Again, awesome, I was afraid I'd have to order the kit for a DA and wait another 2 weeks. The one thing I hate more than anything else during a build, is stupid delays.

Edit:

6. Do I need the DA LCAs as well, or can I re-use the LCAs on the civic? In one of the FAQ walk-throughs, going by the photos it looks like he used the DA LCAs so I'm not really sure.

 

well i answer your question based on my own experience with swapping my 91 DX....

1. correct me if im wrong but i think i think i might have read up somewhere that someone said that the DA cable is to long, so i went ahead and got crx si cables

2. im sorry yes u will need the rear lines either from a SI or DA...i was thinking that it already had it....but like i said you might as well go ahead and get a set of steel lines to replace the old lines on em....if you do decided to order them..order them for 90-91 crx si.

3. well with your oem ppv and mc/bb..you won't get the proper pressure going to the rear disc..because your still running the oem ppv and mc/bb that is set up for front disc and rear drums....get the DA mc/bb & 4040 ppv and you will stop on a dime.

4. i said the same thing also when i did my conversion.

5. agreed

 

I just did the swap:


1. What all do I need from a DA/DB to do this conversion?
Trailing arms, prop valve, parking brake cables, fluid lines you didn't say what Si. DA cables fit a hatch perfectly, but are long for a CRX.

2. Will I need to buy rubber(or SS) caliper lines? If so, what car should I order them for? Or can I just re-use the civic lines or DA/DB lines?
You can reuse the the lines but why, these cars are old and who knows how long it was exposed to the sun. I got a set of Goodridge lines (all 4 corners) for around $100

3. Will a booster and/or prop valve upgrade be necessary if I'm only converting the rear to DA discs?
You should replace the prop valve but I don't know if you have to. You don't have to replace the booster at all because an EX m/c is also 15/16 and fits the stock booster.

4. Is it 100% confirmed that I don't have to drop the fuel tank on my hatch to do this conversion?
Some people have done it with dropping the tank, but I had to. Dropping the tank doesn't mean removing it. I just undid the straps and let it drop about an inch or so.

5. I just ordered a rear camber kit for this car, that adjustable dog-bone that goes between the hub/trailing arm assembly and the car. Will this fit the DA hub assembly, or do I have to order another new kit for a DA?
Same one works for either arm.

 

1. I've got a Civic Si. The guy above said the DA parking brake cables would be too long for my car, and that I would need CRX Si cables.

2. I figured I will order new lines, I just needed to know what I should order them for...Civic Si, DA, or CRX Si. The guy above said to order lines for CRX Si or DA.

3. The non-ABS DA I'm getting all these parts from has a good prop valve and brake booster, so I'll take those and also buy a new non-abs DA master cylinder from autozone. Any mods necessary to use this stuff, or is it all pretty much direct swap-in?

4. If I have to drop the tank a little, will I need to access under the rear seat for that, unhook lines or anything...or is it just a matter of undoing the straps?

5. Already answered above, but thanks for confirming.

Edited first post to add a 6th question.

 

1 CRX cables only work for a CRX, it has the shortest car so it will be too short for anything else. I should clarify that DA cables work, but 4-door DA cables will be too long. I used the DA cables that came on my arms and they fit perfectly. All the clamps were positioned in the same locations as my hatch.

2 I ordered s/s lines for a CRXSi (with discs) discs is the important part because the ones for drums have different fittings.

3 Get an 90 Civic 4-door EX m/c from Autozone and it will bolt up to the booster already in the car. You won't have to hang upsidedown under the dash to swap boosters (unless you have to replace the booster.) The DA has a larger (fatter) booster but both will work.

4 I only undid the straps, left everything else attached. I only needed an inch more room.

5 .....

6 There is an adapter plate that will allow you to use your existing arms but replacing the entire arm is easier. I think cost is similar because you have to buy all the parts (calipers, rotors, hubs?) if you use the adapters. I suppose I should have gone with the plates since I replaced everything when I did mine.


This thread contains pics of my swap:
https://honda-tech.com/forums/honda-crx-ef-civic-1988-1991-3/rear-disk-swap-questions-2846303/

 

Not trying to throw a monkey wrench in this discussion, but I used eg9 rear disks for my conversion. I bought the the assemble from HMO with the trailing arms, caliper, pads, disk and everything already assemble. I had already changed my MC over to an EX for my hatch when it died. I did not change the PPV or BC. The brake cables were a little short to route through the normal route, but I've never had a problem with the catching or getting burnt by the exhaust, they stop just fine.

 

Just got back from Autozone. They looked up the MC for a 1990 Civic 1.6L hatch/sedan and it was the same exact one shown for my '91 Civic Si. They then looked up one for a 1990 Civic 1.6L wagon, and it was different. They didn't look up any for the 1.5L cars. Obviously they can only look up year, make, model, body type and engine...not actual trim level. I figured I would ask here before purchasing, because I'm not sure what to get.

What is the exact Civic I should have them look up for the better MC? I have no idea what motor the EX had, it was either 1.5L or 1.6L...if it's the 1.6L, then my car uses the same MC according to Autozone.

Also, if I do get a better MC...is it a direct swap-in replacement? I don't have to re-flare my lines or buy new lines?

 

I actually picked a 90-91 Civic EX MC from Autozone today. You have to make sure to tell them it's from the sedan, and that it's 15/16". Tell them to pull up the part and it will have that information there.

It was a special order part, in Cali at least. The system actually said they had one in stock like 10 miles away, and I drove there and they didn't. They also told me it was a special order part. But, I did get the reman, maybe brand new ones are different.

Like said earlier the Civic EX MC will work with your stock booster. And yes it will be a swap in replacement.

 

I was looking at their screen as he was searching for the MC. They're system pairs the hatchback and sedan together, at least for the 1.6L option. The separate one is the wagon, which I believe had the 13/16" MC.

 

the part# for the reman is : M52517
new one is : NM52517

 

That is the number that showed up when they searched the 1990 Civic 1.6L hatchback/sedan, and the number that showed up when they searched the 1991 Civic 1.6L hatchback/sedan.

Here's the results for my 1991 Civic Si 1.6L...bottom of page is the 15/16" reman'd mc.

http://www.autozone.com/autozone/par.../N-ithibZ8kn47

Apparently the 1.5L civic had the 13/16" MC, and the 1.6L had the 15/16" MC. So this means my '91 Civic Si 1.6L has the 15/16" MC already...?

 

You do not need to change the master cylinder or booster for a rear disc conversion; the stock 13/16" MC will work fine. The MC has nothing to do with proportioning. The Nissin 7CLP13S rear calipers require about the same volume of fluid for operation as your existing S04 wheel cylinders.

You should change the proportioning valve, however the only vehicles that would have the correct proportioning valve for your system are the '92-95 Civic 3dr Si and the '93-97 del Sol 2dr Si. If you're going to use any other proportioning valve, I wouldn't bother changing it because no cars other than the two that I listed have a similar brake system to the setup you'll be creating.

For parking brake cables, you must use those from a '90-93 Integra 3dr. '90-91 CRX Si cables are too short.

 

I'll try to find a prop valve for one of those two models you listed.

As for the MC...could you answer that for me? From what I'm seeing on Autozone's system, I already have the 15/16" MC...not the 13/16" MC. I need to buy a new MC regardless because mine is shot, just wanted to make sure the one for this car is already the better one.

 

The bore size is noted on the casting. If it's the original master cylinder, it will say 13/16" right on the MC body. Only '90-91 4dr EX models had the 15/16" MC from the factory in the US; all hatchbacks used a 13/16".

The '90-91 CRX Si used a 7/8" master cylinder, which is equivalent to 14/16" - however, it also used Nissin 16CL13VN front calipers, which had larger pistons than the front calipers found on '90-91 Civic hatchbacks, and thus required a larger volume of fluid for operation.

The EX 15/16" and the CRX Si 7/8" cylinders will bolt right up to your stock booster and lines and will work okay, but the pedal stroke will be shorter and the pedal will be firmer resulting in slightly more difficult brake modulation. It's not really a big deal, but it will feel different.

 

Ah, so Autozone showing it available for my car was only their system basically showing it was compatible? I'll check my MC and see what it says, you think I should just go ahead and get the 15/16" since I already have to replace my MC? From the looks of it, they were going to sell me the 15/16" MC anyways.

 

It's actually more likely that their system is incorrectly listing the 13/16" master cylinder for both models. The '90-91 EX 15/16" MC isn't nearly as common as the 13/16", which was used on all 1.5L USDM Civics and all '88-95 Si non-ABS hatchbacks from 1988-1995.

If I recall correctly, the correct aftermarket reman part number for a '90-91 EX MC was M54016. The OE part number was 46100-SH4-A11.

 

https://honda-tech.com/forums/honda-crx-ef-civic-1988-1991-3/90-91-ex-master-cylinder-part-autozone-781917/

I bought part #M52517 at autozone, and I'm pretty sure it's for an EX. It has a larger reservoir than my Si's MC.

 

i couldve sworn the 91 SIs came with rear discs

 

My current MC is 13/16", stamped on the body of the MC. I'll go ahead and get the 15/16" MC and call it a day.

 

CRXs did, not Hatchbacks

 

Yup. My Civic Si definitely has drums back there, I distinctly remember cussing a lot when I seen them.

 

You can search Autozone's website. It shows the bore diameter in the details.

http://www.autozone.com/autozone/par..._0_0_4307,7319

 

Nothing wrong with drums. They're 8lbs lighter per side, wear much longer, and are cheaper to maintain.