How do you test your brakes?

Mine always easily passes the MOT, even with the scabby discs it had on until recently. I have recently done a visual check all round (including taking of the rear drums etc.) The two front flexis were splitting in a spot that was well hidden, so replaced them, also the discs, pads and a couple of fixed pipes. I then tested them (after some mileage)....they pulled up straight and pretty sharply, handbrake sharp too. Seems about right to me!

Last time I really stamped on the brakes was when I fitted the newly re-faced discs with the Green Stuff pads. That must be several years ago now.

Like Nick, I tend to check the brake (and clutch) reservoir before most runs out.

Chris.

Hi Nick

I guess because I had a short stint at rallying, nothing serious, I got into the habit of finding out the braking and handling limits of every car I have owned somewhere safe off road. If there is a problem with the G valve it should be apparent at 30mph. Just be prepared for the back to come round very rapidly in a most unlike Landcrab way so keep well clear of any curbs etc.

You certainly don't want the first time you find there is a problem to be a real life emergency!

Regards

David

Early days maybe, but I am beginning to get the feeling that a number of owners do not know whether their G valves are actually working or not as it is only obvious when braking very hard which is something you would normally wish to avoid, especially with a classic.

If you look at your w/s manuals you will see the valves have pistons with seals that are now probably well past their use by date.

Is this a fair assessment?


David

Nick

If you look at the original road tests carried out with tyre sizes of 175x13 (Mk1), 165x14 Mk11 /111 all the cars were able to lock their front wheels under very heavy panic braking and the Mk1 eventually locked all four.

The G valve does not affect the front brakes directly although by reducing the braking to the rear wheels does allow for more weight transfer to the front reducing the chance of front wheels locking.

If the G valve on Mk1 / Mk11 cars is not working properly the rear wheels will lock under moderate braking. Alternatively if the valve is seized shut there will be very little or no rear wheel braking. This would show up on a MOT test unlike the seized open situation. It is important to have some rear wheel braking to keep the back in line. The symptoms would be more front end dip under braking similar to Mk111 cars.

Mk111 cars had less rear wheel braking than earlier models and the valve may either reduce this further or possibly stick open. The latter would result in brakes that feel more effective at low to moderate braking. If a Mk111 car suffers rear wheel lock up under any normal conditions ie wet roads but not ice, the valve almost certainly needs to be examined.

1800S cars had more front end braking and should be able to lock the front wheels sooner (Alexander?)

Some other points to note. If the front calipers / pads are not 100% there will be less nose dip and the rear brakes may cause some intermittent lockup under hard braking. The road tests were carried out in unladen cars. Modern 70 profile tyres may prevent front wheel lock up on a good dry surface but make it more likely in the wet. Remember the original tests were mainly carried out on textile radials so if you cannot get front wheel lock up it is not necessarily something to worry about unduly.

Before carrying out the test ensure all tyre pressures are correct and have a check over the braking and suspension components so that you can readily isolate any issue to the G valve.

regards

David

I have received this very comprehensive note from Tony, the webmaster at the Eighteenhundred website about the brakes fitted to Australian 1800s. It would appear that the later Mk11 cars had a much safer dual circuit system than UK vehicles and this obviated the need for a G valve or similar.

Perhaps Tommy or Alexander or other readers in non UK markets could provide details of their braking systems to complete the picture? Andrew which system do you have in NZ?


In Australia, early MK1 cars had the Girling brakes with proportioning valve for the rear, and power assistance on all four wheels. In the transition to MKII, early MKII's still had Girling brakes - probably until the factory ran out of stock. Later MKII had PBR brakes. These brakes have dual opposing pistons in the front calipers, power assistance to the front calipers only, a dual tandem master cylinder with separate circuit to rear brakes. Rear brakes have no power assistance, and no pressure proportioning valve at all. The rear brakes have one leading and one trailing shoe, with a self adjusting mechanism that set the shoe to drum clearance via a ratchet that operated when the handbrake was applied. These same brakes were fitted to quite a few other makes in Australia as the laws here favoured the manufacturer if they increased the local content. They are quite good brakes, and have more capacity than needed for the size of car - the usual fitment is on larger 6 cylinder Holdens and Chryslers.

Manual cars have a pressure balance switch that illuminates the spare orange dash light to signify a loss of pressure in either front or rear circuits (just so you can be fully informed of a failure in one circuit while you are panicking and trying to stop). Automatic cars did not have this switch because it is mounted in the place where the automatic cable bracket is just near the master cylinders. In the auto case, that spare orange light is there, but there is no bulb fitted.

I am not a MKI expert and can't say if anyone has had problems but I will be seeing someone tomorrow who has 5 MK1 cars and he should be able to tell me something.


We recently sent you by email a request for information about your braking systems and experiences. A number of you have kindly provided some interesting details. May I take this opportunity to remind you if you have not already replied that it would be helpful if you could do so by the 5th October. This is your forum and the chance to help the safe continuity of these cars.

If you have not received an email, please check your details are correct on this site. If not please amend them and PM me so I can forward the email to you. 

Many thanks


David