P38A Service Brake right on the MOT limit...

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MrGorsky

MrGorsky

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Just had my car back from the MOT testers, and the tester mentioned I was just over the permissable requirements for the foot brake. The parking brake was fine.

I can punt it down the road for a year but what might cause that?

I have almost new discs and pads (tester said they were fine) and they were all rebuilt when I did my engine rebuild a year or so ago..... Can my acumulator be fading? I don't have any warning lights on the dash, but I'd prefer 100% braking efficiency rather than 53%.

The brake pump doesn't run especially often, and I think the brakes are pretty good for such a large car!!!
 
New gear. It just gives an overall figure without the front back split apparently….

I’ll whip the wheels off and push the pistons back and see how free the feel. I think that’s all it can be really!
 
Did they do it properly with Tapley Meter as recommended by LR ? That's how my local MOT guy does it.

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Last edited:
MrGorsky said:
Just had my car back from the MOT testers, and the tester mentioned I was just over the permissable requirements for the foot brake. The parking brake was fine.

I can punt it down the road for a year but what might cause that?

I have almost new discs and pads (tester said they were fine) and they were all rebuilt when I did my engine rebuild a year or so ago..... Can my acumulator be fading? I don't have any warning lights on the dash, but I'd prefer 100% braking efficiency rather than 53%.

The brake pump doesn't run especially often, and I think the brakes are pretty good for such a large car!!!
Click to expand...
If it was tested on a standard roller meant for 2 wheel drive, then the test is NBG and he could have damaged the transmission. Not sure how it's done in the UK but here the wheels on the axle not being tested are put on free running rollers.
 
They have a yellow box that they put in the car and drive up and down the road a few times braking.

I don’t know what it’s called but he’s only just re opened after a refit and the gear he’s now using is spanking new.

I don’t really care about that though, I just want my brakes better!
 
MrGorsky said:
They have a yellow box that they put in the car and drive up and down the road a few times braking.

I don’t know what it’s called but he’s only just re opened after a refit and the gear he’s now using is spanking new.

I don’t really care about that though, I just want my brakes better!
Click to expand...
That's a Tapley meter so the test is correct.
 
Yep, the new all-singing all-dancing digital Tapley meter. One of my bus engineering colleagues has recently bought one. quite clever stuff, it can tell you what the reading is on each wheel without connecting anything anywhere! 100% brake efficiency is almost impossible to achieve as wheels will (or should) lock on the rollers long before it reaches 100%. And with ABS locking the wheel "should" be impossible anyway. I've had old buses pass the rolling road test simply because 2 wheels on one axle locked on the rollers at about 50% efficiency. The best bit on old buses pre-1968, the parking brake must "be capable of preventing the rear wheels rotating"

You're reading too much bad news in good news.
 
I had a pug 306 many years ago, got it from an auction and the drive home showed the brakes were very poor, hard pedal but poor bite and quite dangerous. Discs and pads were like new, couldn't find anything wrong anywhere. I tried new pads and instantly they were bang on, could stop it on a penny. The old pads were not glazed or contaminated but had no maker's name on them but they were the issue. Food for thought?
 
That sort of percentage is what I would expect. On the old buses I work on 50% is a pass, on post-1968 buses they must have at least 30% on park brake. I don't know what the percentages are for cars, but you can download the Testers Manual online from the DVSA website. 7% imbalance is well within tolerance.
 
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