'Standard' Brake Linings

I have been running in my TA 21 saloon after a long period off the road. I have the original drum brakes. Although most parts have been renewed, I have had recurrent problems with adjustment and performance. The latest is brake fade. I am told that the new brake linings are 'standard' linings. Turns out, after some heavy braking on fast A roads with numerous roundabouts, that the linings are glazing. They will need to be roughed up. As I see it, the car was designed for fast driving and if the brakes get hot under certain road conditions, the linings shouldn't glaze over. I am told it may be necessary to investigate different lining materials. Does anyone know anything about this problem? What lining material should one be using? Posted by Cavendish51 12/08/2015 10:21:35

Have you considered that the drums may be either oval or too flexible to maintain concentricity due to their age and extent of wear? Newer style linings are likely to be more abrasive than old (asbestos based) linings so drum wear and resultant susceptibility to ovality and overheating could be more rapid than when the cars were new.  Oval drums, rusting backplates and / or worn wheel bearings are not good when trying to achieve optimum brake adjustment. You also need to check movement of the half shafts (across the car's width) under combined braking and cornering. If the wear area on the drum is deep the rear brake shoes may be competing with the half shaft movement.  Also, do not forget that brake fade was not unusual in many cars with drum brakes even when the cars were new. Posted by DaveT 12/08/2015 11:24:40

Thanks for that information, Dave. The problem seems to be confined to the front brakes, where curiously the drums are brand new. The original ones had become pitted from disuse and couldn't be machined out successfully, so after several false starts, and swapping them from side to side, they were replaced. With luck, therefore, they won't be either oval or flexible. The advice I'm getting is that it's all to do with the brake linings.   At the rear, I do have one drum with some scoring and a slightly bent back plate, but it doesn't seem as though the back brakes are causing much of a problem.   When I was last using the car in the late 1980s, I never had this problem with glazing. Would I have been running on asbestos-based linings then? Posted by Cavendish51 12/08/2015 13:33:08

It isn't unknown for brand new drums to be oval. I would take them off and look at them closely on a mandrel with an engineer's clock. Posted by Angus D'Arcy-Drake 13/08/2015 09:42:56

My TA21 suffers similar issues. The old linings were replaced with a softer bonded lining that was supposed to offer more bight and thus a better stop. That was the theory. In essence what is happening is that the linings have tended to glaze. There is no issue with the drums either with respect to thickness or being out of round. My garage owner is of the opinion that I do not use the brakes forcefully enough. I can understand the reasoning as I tend to brake through the gear box and thus let the engine do a lot of the stopping. I live in a mountainous area so a combination of prolonged "softer" braking and engine braking is the norm.  The solution is to roughen the linings on a regular basis. This is not a bad idea as it also forces me to inspect all the components. I have done this a few times now and the overall result is satisfactory. I can also add that there is no bluish discoloration of the drums due to heat  as the linings are of a softer material in the first place.  It is worth investigating whether you can still buy woven linings. I had these on a past car and the result was excellent. These linings are riveted but suffer from a relatively short operating life. That said if they were available in my area I would have put them on given the fact that the car is only used intermittently.    Richard Melbourne Posted by RichardWallach 16/08/2015 03:41:05

More questions than answers:  Is there any chance the brakes are binding slightly as this will heat the drums up nicely before you start to use them?  The new drums, are they standard or alufin type drums as the alufin type are supposed to reduce fade.  Do you have one of the laser temperature gauges as this may help to see how hot the drums get both front and rear just incase the fade problem is at the rear and these brakes are working harder than you expect?  Along the same lines, maybe the rear brakes need to be adjusted to reduce the work done by the front brakes therefore reduce fade at the front.  Are you seeing any difference in pedal stroke as I would expect the fluid to start to complain (go soft and give a long pedal) before the shoes did?   Chris Posted by chhym 01/09/2015 10:30:25

Chris, To answer your first question, my answer is no. Your car should be fitted with micram adjusters. They are simple to adjust, turn until the wheel binds and then back off a notch. With the wheel jacked rotate and check for any binding. If adjusted properly there should be none. Do the same for each wheel. As we are not using cables the brake fluid will apply even pressure to each wheel.   Your hand is the best test for rim temperature. Unless you have undertaken a lot of braking the rim temperature should be quite bearable.   As for pedal travel, yes it will be longer if the brakes have not been adjusted up. Given that long pedal travel has been an issue, even with micram adjusters, it pays to keep the brakes well adjusted.  Hoping this helps.  Richard Melbourne Posted by RichardWallach 02/09/2015 09:43:53

Richard,  I was going off experience with a Riley RMF I also own and had brake fade issues once and just trying to help out.  Those issues where simple, lots of downhill runs = lots of heat = very long brake pedal travel due to overheating fluid (silicon brake fluid) however I never got to the point of brake fade due to overheating shoes/drums.  As for Alvis, mine being a pre war 4.3 has the enjoyment of cable brakes however at least I dont have to worry about pistons in wheel cylinders getting stuck either on/off or somewhere in-between due to corrosion  :-)  Chris Posted by chhym 02/09/2015 14:20:02

Chris,  I prefer the hydraulic system but would dearly like it to be split so that I don't lose all braking. That said the location of the hand brake in the TA21 is terrible. If the brakes were to fail I would prefer the hand brake lever to be between the seats.  Regards  Richard Posted by RichardWallach 03/09/2015 02:37:57