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MG MGB Technical - Brakes pulling
I think this is a simple question with a straight-forward answer. I changed the front brake pads on my 1977 MGB yesterday. The new pads were a tight fit, and I had to grind off part of the metal to get the pins and retainers back through the caliper. The passenger side caliper was very tight and I had to tap the pins in...they didn't slide easily through the caliper holes.
This morning on a short 7 mile drive I noticed that the car is pulling to the left when I braked. Is the cause the tight pins on the passenger-side caliper, or should I be looking for something else?
All thoughts are welcome.
|I would suspect bad brake hoses to the front brakes. Internal breakdown can cause them to not release the pressure applied to the calipers when you press the pedal. The pedal pressure is enough to force the fluid through the sclerotic hoses, but the return pressure is only the results of the brake caliper's pistons' seals resisting the forward movement of the fluid pressure. I had a similar problem when I replaced pads and rotors. On the first test drive of less than a mile, I smelled burning break linings and returned immediately home. The offending wheel was too hot to touch, and the new rotor had already started to show a blue discoloration from the heat. If your hoses haven't been changed that you know of, just go ahead and do it. Also, if this is your problem, you may as well make plans to change the rear hose, and the clutch hose may soon follow. These things don't last forever!|
|The fact that you had problems getting the retaining pins in would suggest to me that you have been supplied with the wrong pads, you should NOT have to grind anything to get the correct pads to fit. You may have been supplied with MGBV8 ones. If you simply had problems getting the new pads in between the disc and the pistons then i would suspect siezed pistons or collapsed flexibles. If the pistons won't retract fully, try to push them back with the bleed nipple open, if they go this points to the flexibles.|
|When you replaced the old pads for new did you press the disc pistons back into calipers? If not the added thickness could make them about impossible to install correctly...way too tight. Of course you must keep an eye on the master cylinder so it does not over flow. I have used MGBV8 pads in trhe past and they make no difference. Bob|
|Yes, I had to open the pistons wider using a C-clamp. Then the new pads fit in...barely. The new pads looked the same size and shape as the old ones when I held them up to each other.|
The rubber hoses have not been changed since I have owned the car (10 years, or so).
I'll keep playing around with it over the next week and let you know more as things clarify.
|Expanding on what Allan says V8 pads are handed - there is an inner pad and an outer on each caliper. I seem to recall people fitting V8 pads to 4-cylinder calipers as they have a slightly larger swept area, which if true means they should fit, but maybe only one way round.|
If the pins have to be driven in i.e. are wedging the pads between themselves and the caliper then that *will* make it more difficult for them to retract fully as they should, the pads should only be under spring tension. Not being able to retract the pistons fully to allow insertion of the pads is a different issue and not mentioned by the originator.
I doubt a flex hose would have collaped internally just as you were changing pads, but I suppose it is possible.
|Try swapping pads from the left side of the car to the right side - and vice versa. Years ago I ended up with a set of mismatched pads (friction wise) that pulled heavily to one side. Swapping them around confirmed it was the pads since it then pulled the other way.|
|I fitted EBC Greenstuff V8-sized pads to my car last year. On one side it was also extremely tight to get the pads in and I could only just turn the wheel by hand. Had to tap the pads in with a hammer. The pins were also tricky to install (stiff). However, I certainly didn't need to grind anything and after bedding in they don't bind any more. I don't recall the pads being sided, but that may be because they weren't OEM? Regardless, I put it down either to not being able to retract the piston 100% or to the pads and/or new discs I fitted at the same time being marginally too thick.|
I would be inclined to suspect either a hose as others have mentioned, or that you have a sticky piston or jammed pads on one side. You might be able to tell which pad(s)/piston(s) are sticking by inspection of the pads or disc.
|Another possibility is that you have a buildup of rust behind the piston which won't allow the offending piston to be fully retracted into the caliper. I have encountered this on quite a number of vechiles where the brake fluid has not been changed for a long length of time, if ever. RAY|
Just wanted to follow up on an earlier discussion and let you know that after the break in period it seems that the brakes are no longer pulling the car to the side. So, thanks for all the input, and happy motoring!
This thread was discussed between 02/09/2008 and 10/09/2008
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