Brake master cylinder

[Elanlover]

I'm not concerned that we couldn't get a M10 connector to fit where the M12 is now. My concern is that the larger opening is there for a reason and will push more fluid through the larger opening (likely to the front brakes?) so going with a smaller aperature on one outlet might affect the brake action. pressure and proportioning valves.

But I'm just making this up as we go. I've no idea if the larger aperature leads to both fronts, the backs, the right side, the left?????? Anyone know???? Anyone hazard a guess as to the impact of two M10 connectors instead of 1 M10 and 1 M12?? If nothing then some form of simple connector to replace the M12 with an M10 would be all that's needed. All the other pieces are supposed to line up but I can always call again to verify if we're not too worried about 2 M10 connectors.

[Monty]

Now, this isn't something i am interested in, as my MBC is okay (touch wood), but there are specialists out there who will ream out brake cylinders and fit a stainless steel insert together with pistons & seals to match.

Haven't a clue on the prices either

(but they do work, 'cos i know a man who had one done on his Humber)

Did a quick search and found this place http://www.jlspares.com/brakeparts.htm which do Reconditioning and Resleeving of BMC and it`s not to far from me. So when i get chance i may buy those 1" repair kits from rock auto`s and see if this company will make them fit

[DeeAitch]

I'm not concerned that we couldn't get a M10 connector to fit where the M12 is now. My concern is that the larger opening is there for a reason and will push more fluid through the larger opening (likely to the front brakes?) so going with a smaller aperature on one outlet might affect the brake action. pressure and proportioning valves.

But I'm just making this up as we go. I've no idea if the larger aperature leads to both fronts, the backs, the right side, the left?????? Anyone know???? Anyone hazard a guess as to the impact of two M10 connectors instead of 1 M10 and 1 M12?? If nothing then some form of simple connector to replace the M12 with an M10 would be all that's needed. All the other pieces are supposed to line up but I can always call again to verify if we're not too worried about 2 M10 connectors.

I've no evidence and need to check the ports later but IMHO the pipes themselves are the same Dia and the M10 v M12 thing is to ensure you put the pipe in the correct hole, keeping the diagonal split correct

[Elanlover]

I spoke to AC Delco technical supprot again. Different guy who wasn't quite as helpful as the last guy I spoke with. But, he tells me there shouldn't be any difference in fluid displacement between a M12 and M10 coupler. But, there are a few other things to consider when swapping out the BMC.

Do we know what the ratio of displacement is from the primary to the secondary chamber? He couldn't (or wouldn't) tell me what it was on the OEM BMC but they aren't all 1:1. Some will pump more fluid through the primary chamber than the secondary one. So, you need to make sure that any new BMC matches that spec to the old BMC or you're going to have a decidedly diferent braking experience than stock - as in not normal.

Now, I'm surmising that, if the brake system sent fluid from the primary chamber to one front and one rear caliper then it would hav eto be 1:1. If it sends fluid from the primary to the right and left from calipers then it could be anything including 1:1. Anyone know the answer to this?

Other things like the push rod thread size and mounting holes are important too. If you get the stock one bored out then the replacement push rod you use has to be the same length for both chambers. Easy if you have the old rod out for comparison of course.

[Elanlover]

I've been looking over the parts diagrams and the service diagrams and I'm confused to be sure. To figure this out will require some "experienced" people on both sides of the pond. I'm looking into this under the belief that, in order to get a BMC that does a satisfactory job with a Wilwood (or other) brake upgrade we'll need t fit a whole new BMC. This means new pipes and fitting to go along with the BMC.

So, here we go in bullet form.

- Tech manual says we have a diagonaly split fluid supply system in order to provide better braking in the event of leaks, etc.

- We have a 4 port BMC with one chamber supplying the LHF/RHR calipers and another supplying the RHF/LHR calipers

- You look at the parts guide for the RHD model and, sure enough, you see 4 pipes.

- You look at the LHD version and, lo and behold, 3 pipes

- Read the Training Course manual on page 80 (actually marked 17 on the page) and it tells you that to remove the BMC you need to disconnect the 3 brake pipes

Conclusion: seems the Fed model only uses 3 ports and the UK version uses all 4????? How bizarre is that? So much for the split braking system. Seems I recall someone commenting that thye had a leak and the system didn't perfrom as advertised. Wonder if it was a Fed car? Top it all off with the fact that there's a different BMC product code number for Fed and Uk versions.

So, one would think that the UK BMC is pretty straight foward. Two chambers with a 1:1 ratio. But what about the Fed version? Could it be a different BMC with different ratios in each chamber? This would have a big impact on what BMC could be sourced for Fed cars.

Anyone have any insight into this? Anyone pulled off their Fed BMC???

[Elanlover]

Monty, don't send your new BMC back just yet. Apparently, these guyscan make all your dreams come true.

I was able to find a brake specialty shop in the city. They don't do the work they just stock the parts - and lots of them. I dropped by today (thinking they actually did the work as well) and proceeded to tell them about my desire for a bigger bore BMC, how ones I've seen don't have the same fittings, how I'm thinking I need to run alll new brake lines to mak ethis happen, blah, blah, blah. He stops me and asks why I just don't buy some fitting adaptors. Metric to metric? Metric to imperial? No problem he tells me - look up what I need, call him and there's a good chance they can get them.

How easy is that?

[Monty]

Monty, don't send your new BMC back just yet. Apparently, these guyscan make all your dreams come true.

I was able to find a brake specialty shop in the city. They don't do the work they just stock the parts - and lots of them. I dropped by today (thinking they actually did the work as well) and proceeded to tell them about my desire for a bigger bore BMC, how ones I've seen don't have the same fittings, how I'm thinking I need to run alll new brake lines to mak ethis happen, blah, blah, blah. He stops me and asks why I just don't buy some fitting adaptors. Metric to metric? Metric to imperial? No problem he tells me - look up what I need, call him and there's a good chance they can get them.

How easy is that?

I`ve not sent of for any parts yet as i`ve spent enough at the moment.

It`s going to be very interesting in which way you go, but you still need to find out if the upgraded MBC has the same bolt pattern to replace the stock one:?
Then it`s going to be down to price! new BMC + new fitting/adaptors. The 1" repair kit is only about $20, so i need to find out how much it will cost to have the stock BMC rebored as this could be the easyer and may be alot cheaper too

Keep us up todate and what you decide

[Elanlover]

I think I'd defintely go for a new BMC and a pair of fitting adaptors if they can find them. I'd be concerned that the size of the internal pushrod in the refurb kit for the larger bore BMC might not match the length of the current BMC. Could be a perfect fit - might not be. Without a tech diagram its a bit of a shot in the dark. At least with a new BMC there's no fiddling to be done. I suspect a new 1 inch bore Dorman will bolt right on and if the mounting holes don't line up exactly its easy to fix that with a drill. I can stop by this shop again and have them compare the two Dorman BMC's if they have them in stock.

[Monty]

If i bought the refurb kit i could compare dimensions as i`ve got a spare stock BMC, but i`ll hold off for now and see how you get on.

Going to the Shop to compare 1st is the way to go, don`t forget to compare the indentation where the rod from the pedal makes contact with the BMC.

[Elanlover]

I spoke to the guys at the shop again today. They have the Dorman version of the OEM BMC in stock now but not the 1" bore model. He said he'd try to order one in so we could compare but I'm going to call Dorman first. They've got a tech line and I'm sure they can pull their own tech diagrams and describe whatever differences there may be in the mounting holes and outlet sizes.

[Elanlover]

Ok, been on the phone with Dorman Tech Support. They tell me that the Dorman M390371 is the 1 inch bore BMC we could be after. He also confirmed that it has 4 ports, all of which are M10 x 1. I have the local brake shop looking for an M12 - M10 reducer. He wasalso able to give me the mounting hole dimensions. On the M390371 the centre of each hole is 3.4 inches apart and they are equidistant from the centre of the main piston itself. They didn't have this measurement for the M39869 whihc should be the Dorman equivalent of the OEM BMC.

So my dear Monty, this is where I need your help.

If you have an OEM BMC lying about perhaps you can measure the mounting hole spacing to see if this new 1 inch bore BMC will fit the existing mounting holes. Secondly, could you have a look at the OEM BMC piston and the piston from the 1 inch bore BMC you ordered (I think you got a 1 inch bore BMC????) and have a look to see if there are any noticable differences in the face of each pistion where the pushrod would "mate" to it. The Dorman guy says he thinks there shouldn't be a problem having our push rod mate to the larger bore piston face but then again he also said they don't recommned this kind of "upgrade" (a statement which he later categorized as a purely "CYA" corporate remark).

[Monty]

Blair,

You certainly wasting no time, i`ve just checked the distance between centre of the bolt holes but i`m only getting 2.75"

Don`t forget this is on the UK M100, i presume it`s the same on the Fed

BTW, i haven`t ordered the 1" repair kit so i can`t compare

[Candles]

Just a quick update on my brakes: I fitted the x-ref cylinder earlier in the year to try and get rid of a sensation that the brakes pulled to the left. I thought it might be weak seals in one of the compartments of the BMC. I'd already replaced the front & rear calipers, hoses and many of the lines. The brakes still have the sensation and the front left wheel still locks up first, although the readings for MOT are the same. The only part left to replace is the proportioning valves!

Candles.

[Elanlover]

Blair,

You certainly wasting no time, i've just checked the distance between centre of the bolt holes but i'm only getting 2.75"

Don't forget this is on the UK M100, i presume it's the same on the Fed

BTW, i haven't ordered the 1" repair kit so i can't compare

That's not good This week I may ask the guy to order the BMC into stock and then we can butt the two up together and see for ourselves. I'll also check the length of each BMC because, if they aren't identical there then the 1" bore "repair kit" isn't going to fit into the OEM BMC.

This, as ususal, is a bit harder than it seems.

[Elanlover]

I still want a new BMC!

[WillB]

Mine for sale:-

viewtopic.php?f=3&t=13427

Would post!

[Elanlover]

Let me clarify:

I still want a new bigger bore BMC!


(besides, I can get a new Dorman, Delco or similar BMC for almost 1/3 your price!)

[bobbrown]

Let me clarify:

I still want a new bigger bore BMC!


(besides, I can get a new Dorman, Delco or similar BMC for almost 1/3 your price!)

I feel I am repeating myself
If the brakes are correctly sized then the standard master cylinder will be more than adequate, go too large on the calipers and it will not be.

[ESM]

A reasonably priced master cylinder can be purchased here.

It's in as an Opel Vectra 2.0 16v part. OE Equivalent Numbers listed are:
3492616
558107

As of October 2011 it was priced at £52.30 (ex VAT).

I've bought one. It comes in a box labelled Brake Engineering with the part number MC1213BE. It's a big heavy lump - certainly not an Al alloy. I haven't fitted yet but it looks right. The port sizes certainly look correct (2xM10 2xM12).

[racerstev]

This might help you choose one that's right for you.

http://www.tceperformanceproducts.com/bias-calculator/