Rear disc brakes

[new to this]

The drum back plate is also a difficulty to revert back haha, but yeah it's just for quicker consumable replacement .

Jikovron

I can see that,makes sence

Dave

[Carledo]

Why do people modifiy the hub to take a MGF disc,why not open up the hole in the disc its self,that way you can always go back to the original setup if you need to

Dave

It's not solely about the hub centre diameter fitting, but about the top hat shaped disc fitting over the hub! There's not enough meat in the disc to allow you to relieve it sufficiently to clear over the stock hub without fatally weakening the disc!

To Jikovron I would say that not every mod is a waste of time and money, the Trackerjack vented disc kit being a case in point! This not only makes you feel better, it does actually improve the car's stopping power! Other mods I have done to the braking system, like altering the rear axle pipe pathways also improve brake performance by removing the "first hit" imbalance in the rear brakes that can cause the car to spin out under emergency stop conditions. Some mods improve the physical abilities of the car, more horsepower makes it faster, this is desireable, so worth "wasting" time and money on IMO. Other mods like go faster stripes only affect the look and maybe how you feel about the car, but not it's function! To me, function is all, it can look like the worst shed in history, so long as it goes like a stabbed rat, corners on rails and stops on a sixpence and gives change! I just can't see the point in uprating the rear brakes and then having to limit their performance artificially to what you had in the first place!

Steve

PS, have you investigated the possibility of using a different disc altogether, one that already fits your altered PCD of 105 or 108 mm or whatever the Stag is? It's quite a common size!

[jikovron]

I agree with the overall sentiment but I'm still convinced that I felt the benefit in pedal feel and prolonged fade resistance , also as I had access to a lathe it realistically only cost in discs,pads, second hand calipers and some minor fixtures so only a minor waste of money haha.

If it's good enough for a fiat 124S it's good enough for me

[Carledo]

I agree with the overall sentiment but I'm still convinced that I felt the benefit in pedal feel and prolonged fade resistance , also as I had access to a lathe it realistically only cost in discs,pads, second hand calipers and some minor fixtures so only a minor waste of money haha.

If it's good enough for a fiat 124S it's good enough for me

Well, when I have to reset the so-called selfadjusters every 3 months to keep the pedal up and the handbrake working, I might just agree with that! And yes, you will get prolonged fade resistance, but since the drums can stand 20 laps flat out round Castle Coombe with it's fast straights and tight corners, how much use the extra life is defeats me! If I ever get to Le Mans in a competitive sense, I might go for rear discs!

Funny you should mention the Fiat 124, I was already working in a garage when these came out, the first full production car to feature rear discs. I also remember that it was nigh on impossible to get the handbrake to work well enough to meet MOT standards, even on a well maintained, 3 year old car! I wasted an awful lot of my time and other peoples money in the attempt!

But enough! We can agree to disagree!

Steve

[harvey]

Funny you should mention the Fiat 124, I was already working in a garage when these came out, the first full production car to feature rear discs.

How do you define "full production"? Mk2 Jag had rear discs from 1959, and Rover P6 from 1963.

[Carledo]

Funny you should mention the Fiat 124, I was already working in a garage when these came out, the first full production car to feature rear discs.

How do you define "full production"? Mk2 Jag had rear discs from 1959, and Rover P6 from 1963.

Consarn it Harvey, you're right! And worse than that, I KNEW it! Plus E type from 61, and MkX from 60 or so. I don't really count the Jags cos they used that stupid cable operated second caliper for a handbrake. But the Fiat was the first "average man's" car to have them.

But if you think about the point I was trying to make, none of those cars is a shining example of how to make rear discs and a handbrake co-exist, are they? All of them had useless handbrakes that mechanics appoached with fear and trepidation when forced to work on them, me included! As for the inboard disc with handbrake of the P6, all I can say about that, is that it couldn't have been more useless and complicated if someone at Renault had designed it!

Even today, 40 odd years later, the rear handbrake caliper is a source of problems, the wretched things are always going wrong!

If I was going to employ rear discs, i'd use the "drum in disc" design featured on BMW, Mercedes, Volvo and my beloved MkIII Cavaliers. These work and keep on working! And they give a much more effective handbrake than any dual purpose caliper. But, of course, the engineering involved in doing it this way is far more complicated and harder still to adapt to a car it wasn't designed for.

Another good reason to leave the Sprint drums alone!

Steve

[cleverusername]

If I was going to employ rear discs, i'd use the "drum in disc" design featured on BMW, Mercedes, Volvo and my beloved MkIII Cavaliers. These work and keep on working! And they give a much more effective handbrake than any dual purpose caliper. But, of course, the engineering involved in doing it this way is far more complicated and harder still to adapt to a car it wasn't designed for.

Another good reason to leave the Sprint drums alone!

Steve

The BMW ones don't, I have a Rover 75 that uses the BMW setup and it is a pain. It is very difficult to adjust and it has a tendency to fail over time because the drum isn't used to stop the car, so is never cleaned and can rust.

Citroen had an interesting setup, they used the front discs, which meant you could you the hand brake to stop the car and it was p**s easy to setup. Alas there were cases when the handbrake came off if the front discs were hot when the car was parked and they cooled.

[Carledo]

If I was going to employ rear discs, i'd use the "drum in disc" design featured on BMW, Mercedes, Volvo and my beloved MkIII Cavaliers. These work and keep on working! And they give a much more effective handbrake than any dual purpose caliper. But, of course, the engineering involved in doing it this way is far more complicated and harder still to adapt to a car it wasn't designed for.

Another good reason to leave the Sprint drums alone!

Steve

The BMW ones don't, I have a Rover 75 that uses the BMW setup and it is a pain. It is very difficult to adjust and it has a tendency to fail over time because the drum isn't used to stop the car, so is never cleaned and can rust.

Citroen had an interesting setup, they used the front discs, which meant you could you the hand brake to stop the car and it was p**s easy to setup. Alas there were cases when the handbrake came off if the front discs were hot when the car was parked and they cooled.

Sorry but that's one man with one car! I work on hundreds of cars per year, the number of times I have to fix a DID handbrake is around 1 or 2 a year, then it's usually just a quick nip up of the manual adjusters or, at worst, new shoes, often because the driver has attempted (and sometimes succeeded) to drive with the handbrake on. In an average year, I probably free off and reset 20-30 rear DP calipers, replace a dozen or so sets of pads and a handful of pairs of rear discs ruined by these partial seizures and replace maybe 10 calipers that can't be persuaded to work again. My own Cav auto has DID, the handbrake only gets used once a year, at MOT time! Still passes every time! I still have a handful of Rover 75/MGZT on my books and a mate has at least 6 (some come and go) of his own. can't think i've ever had anything to do with the handbrake on any of em!

The Citroen system ended with the Xantia probably around 2002! They didn't learn the lesson from Saab who employed a similar front wheel disc handbrake in the late 70s/early 80s on the Saab 99 and early 900s. It was discontinued by Saab for the same reason, frequent runaways! One of my neighbours had a Xantia that ran away off his drive, across the road, up a curb, over 20 feet of grass and into a tree. Fortunately, no-one was hurt and the damage to the car was not enough to write it off. I think Citroen actually paid for the repairs as the car was only a couple of years old. He always parked it in gear after that! Shame really as the Xantia was really quite a good car otherwise, one of the last, if not THE last of the quirky hydraulic Citroens. I can't remember now if the XM outlasted it!

Steve

[new to this]

Funny you should mention the Fiat 124, I was already working in a garage when these came out, the first full production car to feature rear discs.

How do you define "full production"? Mk2 Jag had rear discs from 1959, and Rover P6 from 1963.

Consarn it Harvey, you're right! And worse than that, I KNEW it! Plus E type from 61, and MkX from 60 or so. I don't really count the Jags cos they used that stupid cable operated second caliper for a handbrake. But the Fiat was the first "average man's" car to have them.

But if you think about the point I was trying to make, none of those cars is a shining example of how to make rear discs and a handbrake co-exist, are they? All of them had useless handbrakes that mechanics appoached with fear and trepidation when forced to work on them, me included! As for the inboard disc with handbrake of the P6, all I can say about that, is that it couldn't have been more useless and complicated if someone at Renault had designed it!

Even today, 40 odd years later, the rear handbrake caliper is a source of problems, the wretched things are always going wrong!

If I was going to employ rear discs, i'd use the "drum in disc" design featured on BMW, Mercedes, Volvo and my beloved MkIII Cavaliers. These work and keep on working! And they give a much more effective handbrake than any dual purpose caliper. But, of course, the engineering involved in doing it this way is far more complicated and harder still to adapt to a car it wasn't designed for.

Another good reason to leave the Sprint drums alone!

Steve

Steve

For me, i dont see the point of having a drum inside a disc,if your going that way you mite as well leave the drums on,im going with a caliper that also does the hand brake,less to go wrong,and should be a easy hand brake adjustment only hope saying that it doesnt come back to bite me

ive also found a new disc to use, Stag PCD is 114.3

Dave

[Carledo]

How do you define "full production"? Mk2 Jag had rear discs from 1959, and Rover P6 from 1963.

Consarn it Harvey, you're right! And worse than that, I KNEW it! Plus E type from 61, and MkX from 60 or so. I don't really count the Jags cos they used that stupid cable operated second caliper for a handbrake. But the Fiat was the first "average man's" car to have them.

But if you think about the point I was trying to make, none of those cars is a shining example of how to make rear discs and a handbrake co-exist, are they? All of them had useless handbrakes that mechanics appoached with fear and trepidation when forced to work on them, me included! As for the inboard disc with handbrake of the P6, all I can say about that, is that it couldn't have been more useless and complicated if someone at Renault had designed it!

Even today, 40 odd years later, the rear handbrake caliper is a source of problems, the wretched things are always going wrong!

If I was going to employ rear discs, i'd use the "drum in disc" design featured on BMW, Mercedes, Volvo and my beloved MkIII Cavaliers. These work and keep on working! And they give a much more effective handbrake than any dual purpose caliper. But, of course, the engineering involved in doing it this way is far more complicated and harder still to adapt to a car it wasn't designed for.

Another good reason to leave the Sprint drums alone!

Steve

Steve

For me, i dont see the point of having a drum inside a disc,if your going that way you mite as well leave the drums on,im going with a caliper that also does the hand brake,less to go wrong,and should be a easy hand brake adjustment only hope saying that it doesnt come back to bite me

ive also found a new disc to use, Stag PCD is 114.3

Dave

Think 4x114.3 PCD is used on Mitsubishi and Toyota amongst others.

The handbrake on these dual purpose service/hand brake calipers is MEANT to be self adjusting. But the mechanism design (and it dosn't matter who makes it) relies on a spring, on the outside of the caliper in all the road muck and crap, returning the actuator arm FULLY to the rest position, or the self adjuster doesn't adjust. A little bit of grime in the works, or stiffness in the cable is enough to stop it returning fully, this leads to binding, accelerated pad wear and a non functional handbrake!

There is also the factor to me, that this design of handbrake, relying as it does on brute strength at the lever, is not as efficient as on a drum, in the same way that it takes more pedal pressure to stop an unservoed disc equipped car than it does to stop a similar car with drums. I actually experienced this difference first hand in My Zodiac days, the MKII Zodiac often had discs and a servo, Zephyrs mainly had drums all round. But I converted a Zephyr to discs but didn't immediately fit a servo. You needed to be Charles Atlas to stop it!

So with a disc you need greater effort at the operator end than you do with a drum to get the same effect at the business end and the same applies to a handbrake! If you are converting a drum equipped car to discs, you should really examine the mechanical advantage generated at the lever and increase it accordingly to deal with the shortfall the calipers have introduced. Otherwise it's more difficult to stop the car with the handbrake in an emergency (the "true" purpose of a handbrake) and also much harder to do handbrake turns, or park on a hill, or pass an MOT!

And this is the real benefit of a DID handbrake, you get the efficiency and fade resistance of discs on the (power assisted) service brake and the utility and relatively low effort demand of a drum on the parking/emergency/hand brake. So the best of both worlds.

Steve

[harvey]

As for the inboard disc with handbrake of the P6, all I can say about that, is that it couldn't have been more useless and complicated if someone at Renault had designed it!

I'd have to disagree with that as well. Forgetting about the early Dunlop braked versions with the same system as the Jags, the biggest problem with the Girling braked versions was the people who tried to work on them and failed miserably because they didn't know what they were doing. Correctly fitted and set up the handbrake could be almost as efficient as the footbrake, and that can be very efficient. I never had MOT fails after I'd done them properly, and a lot of those were putting right other people's faulty work. The percieved complication of them meant a lot of people's brains went out the window. I mean, if you had a rear drum braked car with manual brakeadjusters, you'd adjust on the adjusters first, then adjust the handbrake cable length to suit, you wouldn't just adjust the cable and leave it at that. Come to the P6 rear calipers, most people just adjusted up the cable to get a handbrake that held (for a while) and did leave it at that. I did loads, and actually worked out that if I could have had all the money that I'd earnt doing them in one big lump, it would have paid for my house.

I would also add that I've seen work done by several of the "P6 Specialists" and they are still doing them incorrectly now, so I can understand your viewpoint, and sorting those out afterwards if you don't know what your doing is going to be a headache. Pass the Anadin please.....

What I say here is in now meant as any kind of insult to your good self, as I'm sure you know enough to leave them alone, but for me, if I could do one specific job for the rest of my days it would be fixing P6 rear brakes, trouble is there just aren't enough of the cars with owners willing to pay my reassuringly expensive prices to keep me living to the standard of luxury that I require..

[Carledo]

I paid my dues with the P6, bought the tool, read the book! Learned to do them right and did quite a few back in the day. Not enough to buy a house with the proceeds (but I lived in London then!) They are still complex, seize up a lot and access is poor to say the least. Still don't like doing them, but then I was never that big a fan of the P6, give me a nice simple Triumph 2000 anyday!

There are so called mechanics to this day that think the way to get rid of excess travel in a handbrake is to adjust the cable! I see it all the time. I guess you still can't cure stupid and lazy!

Steve

[harvey]

Not enough to buy a house with the proceeds (but I lived in London then!)

So did I!

I guess you still can't cure stupid and lazy!

You're right there, that's never gonna happen.