uneven braking

[Hubert]

Hi to all,

I have read the thread about poor braking a few posts down below with great interest, and I would like to hear what you are thinking about my problem: uneven braking.

The situation is: Replica convertible, built 1969, drum brakes and servo, professionally restored (including brakes) in March 2010 and since travelled about 3,500 miles. After about 1,000 miles after renewal the new brakes felt very good, deceleration was excellent and braking even. Since 500 miles the car wants to pull to the left when I suddenly have to brake hard. When I gently press the pedal until the car just starts braking and then increase the pressure it brakes in a straight line. I have been to a garage, specialized on vintage British cars, and they had the Moggie on test equipment. As the measurements at the full brake application were almost even, well within the limits of the German MOT requirements, they refused to adjust the brakes. What can I do to receive an even braking even when I have to brake hard all of a sudden?

Also sometimes , when I brake gently from higher speeds, e.g. before leaving a motorway, the front brakes are wobbling. Funnily it stops when I brake harder and doesn't appear at lower speeds. Will the brake drums already need turning or replacing?

Thank you very much for all your help,

cheers
Hubert

[chrisd87]

Just a guess, but maybe one of the wheel cylinders is sticking when the pedal is applied suddenly, but a gentle application gives it enough time to unstick and perform correctly. This shouldn't be happening so soon after a full rebuild though.

I read your article in Practical Classics a few months ago by the way!

[Alec]

Hello Hubert,

I agree with Chris, have a look at the side opposite the pull first. Adjustment would make no difference to the pulling, the signs that tell you they need adjusting is a low pedal, but not a pull.

Alec

[mike.perry]

Take the drums off one at a time and watch the pistons whilst someone gently presses the brake pedal. Both pistons should move almost together.

[bmcecosse]

There may be looseness/free-play in the suspension bushes - especially the tie-rod front mount rubbers ? Does the car steer hands-off when it's running along normally ?

[beero]

I agree with BMC, sounds like the brakes are okay from the test on the garage equipment. I would renew all front suspension rubbers and then look at differences in the grip on the road caused by unequal damping or unequal tyre grip.

[Neil MG]

If it's on sudden braking and not slow braking it sounds like it's your shock absorbers at fault! It could also be bushes or antiroll bar if fitted, but they should have been easily spotted during the test, shock absorber sounds more likely.

[bmcecosse]

Could even be rear wheel steering - you need to decide if it's 'weaving' or 'pulling'... Adjusting is unlikely to make any improvement - but if it consistently 'pulls' to one side, try swapping the brake shoes from that side with the ones on the other side - does it now 'pull' the other way ?

[Hubert]

At first thank you to all who have giving me advice on my problem.

The car is definitely pulling to the left, not weaving, so it can't be the rear axle. I had the problem mentioned having driven about 1,500 miles. When I had the chance to have the car on the jacks I tightened the U-shaped brackets which fix the rear axle at the springs and the weaving disappeared. Apparently the renewed rubber pads had to bed in.

My Moggie is also running totally straight, even when I take my hands off the steering wheel. The problem only comes up when I am braking.

I have a feeling that a sticky brake cylinder on the right front wheel might be the reason. I have undone the brake drums once so far (last February), and there was an astonishing amount of dirt inside. Maybe this has happened again and is now blocking one or both of the brake cylinders. I will do as recommended and take the drums off to have a look inside as soon as possible. At the moment it's raining (thank goodness - after seven dry weeks) and I am not allowed to do any repairs in the garage I have leased for the Minor, so I have to move her to our carport.

@chirsd87
So Practical Classics have published my little report . I had asked them to send me a copy if they do, as this magazine is not available in Germany, but they have apparently forgotten. Could anyone please tell me in which volume it has appeared, so I can ask my friend in the West Midlands to get me a copy.

Thanks again for your help.

Regards
Hubert
[frame][/frame]
Last weekend saw Maggie's first use as a wedding car!!

[bmcecosse]

Not heard of rear axle pads needing to 'bed in' - they just weren't done up correctly in the first place - but the axle being loose can indeed cause weaving/pulling. At least you have now eliminated this. If the front cylinders are the replica ones with O ring seals, then they may indeed have partly seized by now. When you take the drums off you will be able to see if any of the cylinders are not fully closed. Otherwise - swap the shoes around ands see what happens.

[chrisd87]

Your report is in the Spring 2011 issue, on page 56. It came out a couple of months ago now so your friend will probably have to order it as a back issue.

[kjm]

Hi Hubert,
I just saw your thread , and hope your brakes have now been sorted , our car also pulls to the left on braking , when MOT in March the examiner said the balance was 30% out and that being their limit ,just passed, he thought it was maybe due to lying up during the winter , it does not seem to have improved much so will need looked at , by the way I like your colour scheme .