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MG MGA - Front drum brakes pulling to the left

Hi, my front brakes are pulling to the left under braking, but not enough to take the wheel out of your hand. Thinking I needed to adjust the right shoes I took the drum off, both cylinders are working with no leaks, adjusted shoes as described in the manual and went for a test drive, car still pulled to the left.
Took the left side drum off which was hot compared with the right side. On the left side no leaks but the first cylinder in line was not working, it only worked when I G clamped the working cylinder. The left side brake is doing the harder braking using just one cylinder while the right side with both cylinders working is not as good. All brake lines are in good condition, I am using silicon fluid.
Any help would be appreciated.
Regards
Dave
MGA 1958
Dave Swinburne

Dave
I am not proficient enough to give you the definitive answer, but surely the first step must be to sort out that sticking wheel piston.
My guess is the left side is completely out of balance hence the hot drum.
Good luck, Graham
Graham V

It is not uncommon to have an internally deteriorated flex hose, that outwardly looks to be in good shape, cause a problem like this. The rubber liner material delaminates internally and the loose pieces can act as a one way valve, and prevent the brake from releasing properly.

Also, just because one of the cylinders appeared not to operate until the other was clamped doesn't mean there is anything wrong with that cylinder. When you pressurize the system with the drum off, the fluid is going to take the path of least resistance, so whatever cylinder is loosest and/or has less spring tension acting against it will be the first to move. That the other cylinder operated once the first was clamped, indicates nothing unusual.

If it were my car, I would replace both front flex hoses, bleed the system, and re-evaluate from there.

-Del
D Rawlins

Dave
I had this problem at start of this season after replacing cylinders, shoes and hoses. Before anything else sort cylinder problem. Eventually my problem got sorted after I also replaced the drums and did a thorough bleed of front brakes. You could check/eliminate drums easily by swapping sides and seeing if it changes symptoms. Then a really good bleed and reassess. I don't use silicon but I hear it can be a pig to bleed at times. Also you haven't just run out of adjustment on the bad side? Hope it helps.

Paul
Paul Dean

Many thanks for the advice, I have just ordered 2 sets of Lockheed front wheel cylinders, I already have a set of new brake shoes. I will do the swop and bleed the system and see if that does the trick. If not I will do what you have done Paul and get new drums. I rebuilt this car frame up from 2000 to 2005 most of the parts were in crates including the wheel cylinders so I was not sure how good they were when I fitted them, all brake lines were new including flexi brake parts.
Many Thanks
Dave
Dave Swinburne

I changed all 4 front wheel cylinders and shoes today and bled the front. The left hand old cylinders were both lose one had a bolt missing. Stopping not sharp but I guess they have got to wear in, no noticeable pulling to the left. Brake pedal does seem a bit spongy and quite a bit of travel no different from before, is this the norm using silicon fluid?
Dave Swinburne

Silicon fluid makes no discernible difference. Although marginally more compressible the result at the pedal should be no more than perhaps a couple of milimetres. Sounds like you may still have air in the system.

Steve
Steve Gyles

Brake systems using Silicone take a lot more slow bleeding as the little air bubbles do not move fast in silicon suspension.You have to be very careful whenuring fast creates all sorts of little beastie bubbles.
Sandy
Sanders

Ok thanks I will bleed again, also I have just read that when bleeding back off the adjusters to give the cylinders more movement to give a better chance of getting rid of trapped air.
Thanks
Dave
Dave Swinburne

Dave
Did you say you only bled the front - could that be the problem?
Graham
Graham V

I will bleed all wheels this time starting with the back left.
Dave
Dave Swinburne

Dave

Further to my last, brake pedal movement due to silicon fluid is likely to increase by about 0.1mm rather than the 2 or 3 mm I suggested. The following extract is from an American author (I believe) who wrote an interesting article for the MGCC 'Safety Fast' magazine in 1999.

"Some time ago, an article appeared about the dangers of using silicone. It was written by (I believe) a sales engineer for a company who markets DOT4 type fluid. The myths created by this have been widely quoted since. Among the myths is the fact that silicone is 3-times as compressible as glycol (TRUE) and that this leads to excessive pedal travel, such that the pedal will travel as much as 3cm further (FALSE). While it is 3 times as compressible, the compressibility is still a very small number. With the volume of our brake systems, the additional compressibility would at most add 0.1mm to the pedal travel. Most of the problems with "soft" pedal arise from air bubbles entrapped, and poor bleeding. One should take the precaution of pouring carefully so as not to introduce air bubbles. Wait for 10-15 minutes for any bubbles to escape, and then bleed the brakes."

The link I have to the full article on my website has broken. I will try to rectify and post it later. However, if you use this one and go down to item 22 you can view it that way: http://www.mgaroadster.co.uk/technical_information.htm

The MGCC gave me permission to put the article in my website, mainly because I converted it and a hundred or so other unrelated historical articles for them from hardback to digital for their archives.

Steve
Steve Gyles

Dave, Rather than going round in circles (as I have done) you can isolate the front and rear brakes at the four way connection with the brake light switch sitting on top. All you need to do is disconnect the pipe feeding the rear brakes at the four way connector and use a spare bleed nipple to block it, then you are only activating the front brakes when you press the pedal. If you get a firm pedal the problem is with the rear brakes, obviously a soft pedal means theres a problem with the front and visa versa. You can then further isolate the problem at the three way connector at the back by doing the same thing; disconnect one brake line and block with a bleed nipple then try the pedal. You could actually isolate each brake individually using this method all you need is three bleed nipples with the right thread which I believe is the front (rears have a different thread on mine)
AR Terry

I read the article Steve and I am glad I used silicon fluid, as my car stays in the garage for most of the winter I do not have to worry about corrosion and replacing the fluid every few years. The Chaparral mentioned in the article I saw this race and win at Brands Hatch 1967 BOAC 500.
Dave
Dave Swinburne

This thread was discussed between 04/07/2017 and 19/07/2017

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