Improving M type brakes on OG 2438.

[garagiste]

I have a job to get 50% reading on the Tapley meter for my brakes, no way can I lock the wheels.

May I have suggestions in the order that I go through the system to get some improvement.

Linings and drums appear sound, cables nearly new, apparently not much slack in the system.

What purpose do the anti squeal weights serve? Not fitted as there is no squeal present!

High performance linings have been suggested.

All suggestions welcome Thanks David.

[ian judd]

I would start by jacking up the whole car using axle stands, then using a length of wood between the pedal and somewhere solid ( don't ever use the handbrake for adjusting ) press down the pedal. Then go round checking each wheel, adjusting them till they lock. The levers shouldn't go over centre. If none of them will lock solid it may be that they have had hard linings fitted so will need replacing with softer ones - which bite better but fade quicker. Or, like me, fit Minor hydraulics - real stoppers!

Ian

[Jpallis001]

You have me worried now Ian, why should I not have used the handbrake for adjusting the brakes? I set the brakes (mind I still cannot lock the wheels!) so that they rotated freely; then set the handbrake on one click; went round adjusting individual cables so that they offered the same resistance when trying to turn by hand; set the handbrake to 2 clicks, went round again adjusting so that they offer the same resistance; repeated again on 3 clicks so that wheels were locked.

How do you balance the cables without using the hand brake?

John

[Ian Grace]

John,

I think it is all to do with the twist in the brake cross-shaft, which will be different when applying the hand or foot brake because the apply torque to different positions along the shaft. Hence the bit about setting the brakes on using a wooden block or similar on the foot brake pedal. Unless, of course, you intend to use the handbrake to slow down.

[ian judd]

As Ian says, it's to do with the pedal not being central to the shaft. On M Types the cross-shaft is a 'loose' fitting arrangement which isn't affected by chassis twist like Minors. So when you press the pedal it's pulling the cross-shaft at a slight angle which you can adjust out when altering the cables so it makes no difference. When you use the handbrake to adjust them they will come on slightly differently when you press the pedal. Not only that, but you generally can't apply the same amount of pressure with the handbrake as you would pressing the pedal. A long length of wood jammed between the pedal and the wood behind the seatback is the best method I have found. Don't forget that if one brake is a little too tight it will make the others slack.

Ian

[Ian Grace]

Also, the cross-shaft on the Minor was a much more flimsy affair than that on the M, which was about twice the diameter or more, so it can twist more when pedal pressure is applied.

As for the question about the anti-squeak weights, I don't believe they had any effect on braking - except if your brakes squeal loudly, pedestrians have more notice of your rapid approach.

[Jpallis001]

Ian and Ian, you were right! I had adjusted the brakes very carefully using the hand brake. After reading this thread I re-adjusted them using the foot brake (I used a ratchet strap fixed to the front axel and the brake pedal to get the initial set-up}, and yes, they work much better now! - not managed to generate any skid marks on the road yet!

[garagiste]

Thanks everyone for your suggestions.

Have bitten the bullet and started from the front linings working backwards.

Have found several horrors already, skimmed drums, worn cam shafts, loose bush housings etc etc all on a rebuilt car!

Oh well a good Christmas holiday project!

Have a pleasant Christmas and Peaceful New Year Everyone.

[tonym]

More thoughts on poor braking.

Check for wear on the steel ends of the brake shoes - excessive wear here reduces the effect of the rotating cam on braking.
Also, see if the the top and/or bottom bush housings on the backplates are actually at 90 degrees the the backplates - if they are not then the shoes will be working at an angle to the drums ans also causing excessive wear on the semi-circular notch at the end of the shoes.
Also check to see if you have matched pairs of brake shoes in any particular wheel - there appear to be lots of differences in size of shoe
I am currently, along with my much more mechanically minded pal, encountering all these issues, encountering all these problems.