[Mgs] MGB rear brake questions

Sat Oct 23 11:44:51 MDT 2021

Thank you for your reply. 
As far as the type of wheel cylinders, I don't recall that there was a choice as to whether they were for a GT or a roadster. The only choice was either Lockheed brand (maybe) for more $, or an aftermarket for less $. As far as I know, the back plates are original, but I've only owned the car for 20 years. Its engine is not original, so who knows what else could have been swapped. 
Can you shed more light on the whole speed bleeder thing? And how do do pedal pumping bleeding when you're by yourself? 
The fluid is making its way back to the wheel cylinder, so no lines are crimped. But thanks to the poor fitment of the bleeder thing with the tool, I can't tell if the air bubbles are coming through the brake lines or are air being drawn into the bleeder because the fitment isn't good. 
Yes, I did the clutch system a couple or three years ago. It was a bit frustrating, but seems ok now. 

Thank you, 
-William 

From: "Robert's New iPad" <mgbobh at gmail.com> 
To: wkilleffer at epbfi.com 
Cc: mgs at autox.team.net 
Sent: Saturday, October 23, 2021 1:36:03 PM 
Subject: Re: [Mgs] MGB rear brake questions 

The rear-brake question opens more questions. MGBs had rear cylinders to fit the Tourers and the GTs, different sizes of cylinders and different back plates. The roll pins located the cylinders in the correct backing plates. 
Thus the questions arise: Tourer back plates and new GT cylinders? GT backplates and new Tourer cylinders? Car modified before you got it? Wrong cylinders ordered/shipped? 
Having wrestled through this with my GT, it was years back and now I do not recall which cylinders (size and pin location) are Tourer or GT. Someone will know, though, and that challenge easily mastered. GT cylinders are larger, suited to the additional weight of GTs. If you have to swap parts, do it the way MG built it—they got it right. 
As you replaced them years ago, my bet is that the vendor shipped wrong cylinders. 
As to the bleeding, my experience has been that ordinary pedal pushing has done fine for me on many cars, though I did install speed bleeders on this GT. They are an easy exchange and work OK, but the savings of 1/4 cup of brake fluid doing the job are hardly worthwhile. If the rear brakes are difficult to bleed, have a close look at the metal pipes on the axle. A car that has been flat-bed carried may have had the straps wrapped around the axle, crushing the tubes. That’s not an unusual thing to find. 
Since you are changing hoses, have you changed clutch hose? These break down internally whilst appearing fine externally. As you do the change, do it swiftly, w/o interruption, as introducing a bubble into the line is altogether too easy, and bleeding the clutch line has made many an owner irate. 
Bob 

On Oct 23, 2021, at 1:04 PM, [ mailto:wkilleffer at epbfi.com | wkilleffer at epbfi.com ] wrote: 

Hello everyone, 

The car I'm working on is a 1974 MGB roadster. I decided that I wanted to replace everything relating to the brakes and their hydraulics except for the metal lines. I ordered the parts from Moss but had to sit on them for a couple of years before actually starting the project. 

So, I got the new master cylinder installed, which is probably one of the more challenging things I've ever done on the car. Next step was working on the rear brakes. The rubber hose in the back was pretty simple, but the issue is with the wheel cylinders. I replaced them maybe twenty years ago and didn't have any trouble. But these new ones have a roller pin on them that doesn't line up with the holes on the brake's backing plate. It's been too long to try and swap them with Moss, and I'm not sure that would do any good anyway because I don't recall that there were too many choices for that part. You could get a cheaper aftermarket or a more expensive part that may be made in England. I went with the cheaper one. 

Has this been an issue for anyone else? I could probably drill another hole in the back plate to match the roll pin, but that seems like one of those DPO solutions. Also, I don't feel like I should have to entertain such a notion anyway. The part should fit and function correctly. The current wheel cylinders are probably ok to re-use, but I liked the idea of all new parts. The front brakes are also on the agenda, but we're not there yet. 

The next question has to do with bleeding the rear brakes. I started to bleed the brake furthest from the MC using a vacuum tool I got at a well-known less expensive (think shipping at a port) tool store. It's been a letdown for several reasons, among them that the bleeders on the wheel cylinders seem too small for the bleeder fittings that came with the tool, which causes the tool to draw a great deal of air through its system. I seemed to barely be able to get any fluid through the system. The trouble I have is that I am single and live alone, so I don't have any readily available sources of help. If the brakes are going to be bled, I have to do them by myself. Does anyone have any advice on this topic? 

Thank you, 
-William 
1974 MGB 

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