MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - brake stuff

Ok I'm going to try to refit new pads, rotors, and lines to my front brakes. I didn't notice any problems with my brakes, but my mechanic advised me that the pads were getting thin and rotors old and pitted. I bought a kit from VB or Moss last year (I can't remember who I bought from). Kit came with pads rotors, split pins, pad retainers, and a pair of seals (presumably one for each wheel).

My first question is where does this seal go, it appears to be one of the seals for the caliper, maybe the outer seal where the piston goes into the caliper? It's black with a coil of metal (like a spring) wound round the inside. Next, how do I know if the seal on my car needs replaced, and do I have to take the caliper off the car to replace it? Seems like this is the case.

I removed the old pads from the left front wheel and noticed that the outer pad was about 3/4 worn while the inner was about 1/2 worn. Would this point to caliper/piston problems (seems like uneven pressure causing uneven wear), or is less than even wear not unusual?

Finally (for now) I siphoned a little fluid out of my master cylinder to avoid overflow when messing with the brake pistons. This fluid was dirty with very tiny black particles (maybe from the old brake lines?). Any thoughts on cause and can I flush with ezibleed & new fluid?

I do plan to have a pro look over all this when I'm done.

Thanks for all the help I know it's a lot of questions but I now have a garage to work in (1st house) so I can do lots more work to my car.
Brian

Duh my car is a 1980 B roadster...sorry forgot to mention that first time round.
Brian

Brian. I believe the two seals are the grease seals which go behind the inner wheel bearings. Take a look at the workshop manual or parts catalog. There is the stub axle and the hub assembly. The order of appearance is the grease seal, inner bearing, inner bearing race, spacer, shims, outer bearing race, outer bearing, washer and nut. Most people would take the time to clean, inspect and re-grease the wheel bearings when removing the hub assemblies from the car. (You have to remove the hubs to unbolt the brake rotors/discs from them, then attach the new ones.) Did you get new wheel bearings with the kits? Some come with them, some without. It is a good idea to have some spare shims also as you may need to add or subtract a shim or two when setting up the hubs again. Paul Hunt's website has some very good information on this subject as do the archives.

Unequal pad wear indicates that the pad wearing less is not being forced against the rotor/disc by the caliper piston. This indicates that rebuilding the front calipers would be an excellent idea. Much information on this in the archives. You will probably need one or more new pistons. Make sure they are either the original, chrome plated type or the new stainless steel type. There were some pistons a few years ago which appeared to be blued carbon steel. This will rust quickly when exposed to moisture and brake fluid attracts moisture.

From the condition of things, as you describe them, you are probably going to want to rebuild the front calipers, replace the rear wheel cylinders, replace the three rubber hoses and flush the system with denatured alcohol to get rid of years of built up crud. Rebuilding the master cylinder would be a good idea so the whole system is in good condition. Once again, the archives and a good shop manual should provide sufficient information to do what needs to be done. Les
Les Bengtson

Brian,

With hdraulic brakes you cannot have different pressures on opposite sides of the caliper. That is the reason why you have hydraulic systems in the first place.
You can have a seized piston on one side, if this is the case the runout on the rotor would now be excessive, and would have to be replaced.
Having changed disc brake pads literally thousands of times since I first had my mga twin cam in 1964, and working for years in the clutch and brake business I have never seen pads worn evenly on both sides. The variation is caused by different amounts of water and grit thrown on each side, the effect of splash guards shielding the rotor, different temperatures because of different air flow etc etc...
If the rotor runout is correct you don't have a problem.

Mick
M F Anderson

Brian,

I'm gonna take a shot that the rebuild kit is, eg: VB FBK100. The seals shown are for the calipers. For what it's worth, by the time I got to brakes in my restoration process, I was too frazzled, and a bit unsure of rebuilding calipers. So I got rebuilt ones, considering piston costs, time, labor etc (for my own pieces of mind).
But that's a personal call.

The black crud is just from age of fluid and any moisture within the system. You might consider replacing the brake lines, along with the rebuild of master cylinder.

Just some more babble to lend a thought.

glg

glg gimbut

Les, thanks for the response. I didn't get new wheel bearings and I do think they need replaced (another job I've not taclked before). I'm planning to order new bearings and install while I'm doing the brake job. Any suggestions on where to get quality bearings from? Can calipers be refreshed, new seals etc without separating the halves? My pistons seem to be in good shape all the chrome is there no pitting or rust. There may just be some crud between the piston and seal.

Thanks,

glg, I'll look up the id number of my brake order, I keep all my receipts in order.
Brian

Brian, Based on my experience with changing several hundred sets of disc brake pads I think uneven wear is normal as Mick stated. It happens in the single piston calipers used in many US made cars as well as in the dual piston calipers like those on the MG. Bearings should last longer than a set of brake pads. FWIW, I change the bearings, if after cleaning and inspection they appear to be defective. You should be able to get good quality bearings at any good local auto parts place. Good luck, Clifton
Clifton Gordon

Anyone have any tips for pushing the pistons in to allow the installation of the new (thicker) pads. I was able to get the pistons to retract but only with a pry bar, a lot of brute force and maybe some dings to my rotors from said prybar (which is no big deal since I'm replacing them). But in the future I wouldn't want to go that route. Maybe some kind of funky C-clamp, or is there an actual tool for this?

Brian

Take the calipers off and use channel lock pliers to push the pistons in.
David
David

Brian. I have always received good parts from Brit-Tek up in NH. Bob Ford runs a good, tight ship and provides quality service. The B-Hive, owned by a fellow named Gordon I believe, has a similar reputation. If you have BAP imported parts stores, they can get MGB parts as can a number of the "general auto parts stores".

The seal you mention in your orginal post is definitely the grease seal for the hub. I have just checked three different brands of caliper rebuild kits, including Lockheed, and none of them supply a seal having a spring. All of the caliper seals are solid rubber with the only metal parts the two rings which hold the seals in place. As Dave notes, removing the calipers and using vice grips or "Channel-Lock"s(actually a brand name for water pump pliers) is a good way to force the pistons back inwards. C clamps can be used (but there is not a great deal if space to get the larger ones inside, so you are limited to the smaller sizes and need to use some form of spacer to either bridge the piston from side to side or to sit into the hollow and give the C clamp something to push against. There is a good deal of information on removing pistons in the archives and help with rebuilding the calipers. You do not have to split the halves and many people, including the factory, do not recommend doing so.

As to pad wear, Mike is perfectly correct that the pads seldom wear exactly the same. However, my experience is that they wear at a similar rate. Thus, while you will see some varience in the pad thickness when you place them side by side, the thickness difference will not jump out at you with a casual inspection while the pads are installed. When you look at the pads and immediately notice a big difference, you have some form of problem. Do not know, myself, if having a stuck piston will damage a caliper. You can put a dial indicator on the caliper and spin it while on the hub. Run out (wobble from lowest to highest point) should be .003 max, preferably less. You can also use a set of dial calipers to measure the thickness of the rotor to see if it is within spec. I will actually do such things on the second and subsequent brake rebuilds. The first time I rebuild the brakes on a car I replace the rotors, pads, rebuild the calipers and mater cylinder, replace the rear wheel cylinders and brake shoes and clean, inspect and lube the rear brake shoe adjusters. I also replace the three rubber hoses. At that point, I know, and have documented, exactly what the condition of the brake system is. I also have a starting place for my general and preventative maintenance programs. Les
Les Bengtson

Thanks again for the detailed response. My rotors and pads are Lockheed. The seal (which came with my rotor/pad kit) doesn't actually have a spring attached but has a coil of metal that "looks like a spring" if I were to pull it out of the channel on the seal and straighten it out. I suspect it is the grease seal for the hubs. We'll see when I take my old one out and compare.
Brian

Brian. It is the grease seal. As I mentioned, the other seals do not have the spring inside. Thus, if you decide to rebuild the calipers, you will need to get the caliper rebuild kits. There is information on doing this in the archives. Les
Les Bengtson

This thread was discussed between 11/03/2003 and 12/03/2003

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.