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MG MGB Technical - mg brake lines

As long as I've got the attention of some of the MG sages I may as well press my luck.

I'm setting up a triple master cyl Wilwood pedal assy in my MGA. I've got three 3/4" master cyls with a balance bar on the two brake mcyls.

1. The mga has a larger line for the clutch slave cyl than the brake lines. The guys at Behling racing here in Milw assured me that I can use 3/16" line for the clutch slave. I'm worried that I'll end up with too much pedal travel or not a quick enough throwout bearing release. Any comments??

2. The fittings have been driving me nuts. I've posted, but nobody seems to know what the MGs have. I'm using American -AN3 fittings with a double inverted flare. The MG seems to have the same flare, but with different fittings. I've also heard of a bubble flare, single flare, 37* and 45*, and ISO. Any lessons out there from the school of hard knocks??

Fred H

1. The size of the pipe is immaterial - it is the relative bores of the master and slave cylinders that determines pedal and clutch travel.

2. Why not just buy the correct fittings from the UK - postage will be minimal.
Chris at Octarine Services

Chris, good idea, but that's not how I do things. First, I have to throw away all kinds of money unnecessarily. Seriously though, thanks for the advice. I've already got everything at this point including a double flare tool.

Come to think of it, there's a thread on the MGA post about parts you wish you could find. I guess British brake fittings would be one of those items. I've posted several time in the past about this stuff and never got a definitive reply, so I'll say it again:

What are the flares and fittings for MGs called?

English flare?
Double flare?
Double inverted Rodney flare
ISO flare
Metric flare with a twist....and are the threads on fittings for the Australian cars left hand?

I digress. I've ended up using AN fittings to and from the MGA 4way fitting. I'm using 2 of the 4 way fittings, one for the back and one for the ft with the brake light fitting on the front. I'm planning to plug the hole for the brake light fitting on the rear with a 3/8-24 hex plug, which worries me because I THINK it's a pipe thread hole. The hex plug is pretty snug in there and I'm wondering if it's okay to use it along with lock-tite thread sealer????

The other unused holes will have bleeders. Do you think that's okay?

Thanks
Fred H

Chris - maybe I'm looking at this the wrong way, but if the line size is larger than stock, doesn't that increase the pedal travel by requiring possibly double or triple the amount of fluid displacement to engage the clutch? 3/16" line requires 2 1/4 times the fluid flow of 1/8" line for the same line pressure increase. Or is it volume of fluid displaced that is of greater issue? Maybe Fred will have to determine the increased displacement volume of his new master cylinder and size his lines accordingly? Or does the line size just mean more volume of fluid in the system and pressure loss is immaterial?

Jeff Schlemmer

Jeff,

Brake fluid is non-compressible, that's why we bleed out all the air bubbles. Therefore, the volume displaced by the MC will duplicate in the slave cylinder. The tubing size is irrelevant unless severely restrictive.
Edd Weninger

That is why the clutch line is usually larger than the brake line - the fluid needs to move quickly as you thump the pedal down.
Chris at Octarine Services

Thanks guys. So is a bigger clutch cylinder better, or is there a formula for determining the proper fluid displacement. I imagine if you pump the fluid too fast that you would always get immediate full engagement of the clutch, which could make street driving difficult. Or is this such an extreme situaution that you would have to be a fool to get to that point? And how about brake lines? Size does matter, as I was thinking for the clutch right? Isn't that what keeps the front/rear proportioning correct?

Jeff Schlemmer

I larger bore master cylinder will pump fluid quicker but I think you'd get used to it and be able to drive the car smoothly. There ain't no brake proportioning in stock Bs. You can install a proportioning valve however or through trial and error you can use different compounds for the brakes as Mercedes used to do.
Mike MaGee

I recently got a replacement line from Moss.
As you know the lines are not pre-bent, but are quite easy to work with.
The flare on the new unit did not look like the flare on the original line (bubble flair?), so I spoke to the owner of an old time brake shop in the area, since I needed the line shortened by about 4 inches. (surprise !)
He said the flare on the Moss unit would work ok, and proceeded to put a flair (not sure of the correct name)
on the shortened end.
Louie

Hi Fred,
MGs have a bubble flare, not double (though they are close), with standard SAE sized threads. AKA an ISO bubble flare. My flaring tool kit for making such flares is mostly metric sizes, so I'm thinking mostly European cars are using these now. I just recently picked up some pipes with the right flares and fittings at Pep Boys.

On another note, Fred, didn't you recently post about getting a body dipped at a pretty reasonable rate? If so I'd like to hear about where. Feel free to e-mail me if you want.

Have a good one, Wade
Wade Keene

Wade, might as well share with all. The place here is in Franklin, WI. which is on the far southwest end of Milwaukee. If you've ever been to MG LTD, it's very close.

Restoration Specialists
6846 S. 112th st
Franklin, WI
414-529-1515

It takes of ever bit of rust and they coat it with a rust preventitive. Big stuff is a better deal than small stuff.

ft clip $150
r clip $150
fender $ 50

No amount of sanding, sandblasting or grinding could ever get every nook and cranny like this does.

Thanks for the info on flares. I noticed that the bubble flare tools were all metric. I began running lines yesterday and I'm heading over for more today. It's my first experience with flaring and it's not going as smooth as I had hoped. I'm switching to AN fittings with the double flare.

Any tips other than,(remember to put the fitting on FIRST)?????? That's when you know it's time to quit for the day.
Fred H

Thanks for the info Fred. It's been a while since I've been up that way, but I have a good idea of where that's at.

I don't have much else to offer for advice except patience, use the old lines as patterns as much as you can and err on the side of making the lines a little long. I don't have any references handy, but I have a feeling that an AN fitting may work with a flare other than a bubble flare anyway, so I'd find out what they would want and make sure you're using a type of flare that will do a good job of smooshing between an AN fitting and a Lockheed piece. Sorry I can't help more than that, good luck with it.
Wade

This thread was discussed between 10/01/2004 and 14/01/2004

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