Master Brake Cylinder Bores

[Sandwich]

Hi guys,

I bought a new master brake cylinder from RockAuto and the bore holes are both 10mm (all on RA seem to be), however, one of my brake line ferrules (closest to driver) is >10mm (not sure exactly how big, I think because its RHD spec) would there be an issue with brake bias if I replaced the brake line to a 10mm one like the other one? I dont wanna go for a pirouette when I brake hard.

its a UK 89 Aerodeck EXI with ALB

any wisdom appreciated.

Cheers!

[ShiRen]

The brake line should be 3/16" tubing, that means the fittings are either 3/8" or 10mm. If you have a 3/16" line there should be no issue if you put a 10mm fitting on it, but I don't know why it would have a 3/8" fitting in the first place and I highly doubt your car is plumbed with 1/8" line. I would try to confirm what size line is on the car.

[Oldblueaccord]

Hi guys,

I bought a new master brake cylinder from RockAuto and the bore holes are both 10mm (all on RA seem to be), however, one of my brake line ferrules (closest to driver) is >10mm (not sure exactly how big, I think because its RHD spec) would there be an issue with brake bias if I replaced the brake line to a 10mm one like the other one? I dont wanna go for a pirouette when I brake hard.

its a UK 89 Aerodeck EXI with ALB

any wisdom appreciated.

Cheers!

im perplexed you cant find the correct master cylinder. Im guessing to the way the brake lines are run stock on a RHD car? Sorry being American about this.

[Sandwich]

Cheers ShiRen, gonna get the old calipers out to be sure. Yeh I think it might well be to do with the RHD spec, do you guys in US have ALB on your accords? Someone on an aerodeck forum told me US spec didnt have ALB, so could be why.
Cheers

[ShiRen]

You know, some ALB lines are 1/8" on some cars, maybe you have 8mm fittings.

Not sure if the US got ALB, if we did I think I want to avoid it like the plague.

[Oldblueaccord]

you will get more fluid volume with a larger line. I looked at mine and its the 15/16" bore but the fittings look the same front and back but mine has drum brakes in the rear.

[ShiRen]

I didn't know if he was asking about the piston bore or not. Mine is a 7/8" bore, that's standard on most models. I don't think they sell the 15/16" on Rockauto, that's an SEI part right? I do know all the ones one there are M10x1 threads though

[Oldblueaccord]

Not sure I only replaced it once.

[Dr_Snooz]

We didn't get Anti-Lock Brakes in the US, so unless Rock Auto has a UK division, you probably aren't going to find the right part there. In the early years of ALB (ABS in America), the systems were somewhat primitive and not standardized at all. The system on my '90 truck operates on the rear wheels only. Other systems only ran the front wheels. The system on my '93 Accord operated all four wheels, but the rears were operated together as one brake.

It's impossible to guess what Sandwich's system setup is, so I won't try. What I can say about my '93 is that the ABS master cylinder is a very different animal than the non-ABS MC. Do what you think is best, but I would exhaust every effort to find the right part before modifying the system.

[Oldblueaccord]

15/16 is for the LXi the 7/8 is for the DX. The Lxi has the larger brake rotors so the piston bore for the front caliper must be bigger.

https://www.rockauto.com/en/moreinfo...166914&jsn=841

[ShiRen]

I suspect a non abs master cyl will set the abs REAL QUICK

15/16 is for the LXi the 7/8 is for the DX. The Lxi has the larger brake rotors so the piston bore for the front caliper must be bigger.

https://www.rockauto.com/en/moreinfo...166914&jsn=841

I knew those 15/16" were on there, I guess I glossed over it when I checked

[Sandwich]

Yeh got my words mixed up, the piston bore fits perfectly, it's the 2 M10 threads which are off, my closer to the rear thread should be about 10.5mm, I managed to get the part number off the UK Aerodeck group 46100SH3N52, although the only sites selling it seem to be russian and about a £180 so not going that way! It's annoying because if it was the other way round (thread too big) I could just wack an adapter on and it wouldn't affect the but alas. I do need to get the Vernier callipers out to confirm the size of the lines, will get you guys an update when I can borrow some from work. An increase in area for .5/1mm diameter increase isn't huge, and it should solve my brake pedal sinking at the lights so may just go with it.

[ShiRen]

The piston bore is internal to the master cyl, not the part that fits into the brake booster. Unless you disassemble the abs master cyl and measure the piston diameter with calipers we have no way of knowing whether the non abs master cyl will work. I am worried that abs master cyl has a tiny piston in it and putting the DX/LX master cyl on the car will result in some brakes that are very easy to lock up. I have no idea where the EXI model stands compared to the US models, but it may even have a 15/16 bore like the LXI, but if that is the case I don't know why they would make it where they are unable to swap, future cars usually didn't have different master cyls for abs/non abs.
If you can verify the piston bore is 7/8 or 15/16 I don't see an issue with adapting the brake lines, there will be very little change in pressure, but you need to use the proper size fitting on the line and use a female adapter to go up to the bigger line.

[Oldblueaccord]

Yep the dang thing is backwards!

Might consider rebuilding it or getting it rebuilt. there just a few seals inside. The bore cannot be scratched up.

[ShiRen]

Its a single piston too! That would be tricky to adapt.
Ngl, this abs seems really sketchy, but hell its the 80s.

[Sandwich]

Ahhh! Now I see what you mean ShiRen, I guess I'm gonna have to take a look at the piston bore of the old cylinder and compare it to the size of the new one, having thought about the pressures I agree with that too ShiRen.. The part in my car is the same way round as the US ones, not like in that pic dont worry Oldblue (I've tried to attach a crappy photo of how it looks in the car atm). The one I bought on RA for reference is the Centric 13140008 https://www.rockauto.com/en/moreinfo...942&cc=1166969 .

I was considering a rebuild of the old one, my mechanic said he thought that could be fishy since given the sinking pedal, the piston could be off centre and gouging into the metal, no clue how one of these works so not really sure I can comment.

Really appreciate the help guys!

[Sandwich]

Yhe just had a check, the new one I bought was an LXI one so 15/16 bore, I guess thats what I'm hoping for!

[Oldblueaccord]

Well looks like same size fittings. The fittings are soft and pretty easy to cross thread. Yours are a little rusty too.

You may want to thread the fittings on then put the master cylinder all the way on just to make sure you got them threaded correctly it can be really frustrating. you bottom out the line against the female cup in the master cylinder then start the fittings

Dont forget to bleed(bench bleed) the new master cylinder first like I have in that picture above to get the air out. you will never get all the air out all hooked up in the car bleeding at the wheels.

Getting air out of the ALB modual is a whole nother thing that maybe the dealer can help you with.

[ShiRen]

Yeah now that you posted a picture that does look exactly like the US spec master cylinders. If it actually does fit then I don't see any issue in running the 15/16 bore even if the one on your car is 7/8. Imo my 7/8 is a bit underpowered, I am just going to grab a Wilwood master cyl since I don't have power brakes anyway.

It would be a very good idea to replace the oem fittings, they are made out of the worlds worst pot metal, so I would still verify your line size and if they are 3/16 grab some good, preferably stainless, M10x1 fittings.

[Sandwich]

Right, did some checking with the calipers. Both lines are 3/16, and the fittings are M10 (front one) & M10.5 or M11, (couldnt get in close enough) as suspected. Given the lines are the same I'm more confident going ahead with the new master cylinder. Plan now is to do some research on the OE part, if nothing, get the old one out again, check the internal bore diameter and then cross fingers, hopefully the inner piston is the same and bobs your uncle.

Good shout on the fittings, will get the manky things changed over.