My Fab VRS needs new rear brakes....is there any benefit in getting upgraded ones ie bigger discs?? I've got 312mm on the front which are fantastic but do the rears not have much impact?

Cheers

Apparently upgrading the rears doesn't make much difference, most common reason I've read about is for looks more than anything

Thanks for the response Mike.

Never really understood about the brakes, when I press the brake pedal do just the fronts or all four brakes come on...? :S I always thought the rears were mainly for handbrake.

Just been to get some quotes, Kwik Fit were £170+ whereas local diesel independent garage £100

As far as i'm aware the way the brakes are set up they are front bias, so when you press the brake pedal the force is divided 60% to the front, 40% to the rear (or some other percentage) however being a front wheel dive car the front brakes will always have the higher percentage which is why most people don't bother upgrading the rear brakes. I remember seeing a kit on ebay for a 256mm rear brake upgrade for about £280, this included carriers, calipers, disk and pads.

If those quotes are to replace the existing discs and pads i'd say £100 isn't bad. I was just over £30 for discs and pads from a local stockist, changing them was a fairly simple job, only thing it required was a caliper wind back tool for the caliper piston.

I had to have my rear discs and pads renewed after 3yrs of ownership as they were in a bad way.

Apparently due to "lack of use" than the opposite!

The lack of use is quite common on rears on most cars. Been told it's the way most people brake due to not knowing how to work the abs system properly. Most people over say 30 have probably mainly only driven non abs cars so you brake the same with the abs system it never works which usually doesn't load the rear brakes correctly. Was told by a mate of mine (Citroën specialist mechanic) that a good bit of hard braking now and then letting the abs work properly should help with rear brake life. Have been doing this for the last 12 months with the old car and the discs still look like they did when put on where as the old ones were unevenly worn and very rusty

The lack of use is quite common on rears on most cars. Been told it's the way most people brake due to not knowing how to work the abs system properly. Most people over say 30 have probably mainly only driven non abs cars so you brake the same with the abs system it never works which usually doesn't load the rear brakes correctly. Was told by a mate of mine (Citroën specialist mechanic) that a good bit of hard braking now and then letting the abs work properly should help with rear brake life. Have been doing this for the last 12 months with the old car and the discs still look like they did when put on where as the old ones were unevenly worn and very rusty

I'm well "over 30" and I'd reckon that (sorry) women being cautous tend to back off early so the rear discs don't get much work to do. I tend to be reasonably firm with the brakes on my wife's Polo when I drive it and the discs are surviving okay. That is a lot better than what has happened to my B5 Passat with its ATE Power Disk front disks, lack of use has left it with coming out of the previous winter to last with some surface rust that just did not get cleared back to good metal before last winter and now they are both trashed with only 17500 miles on them. I think that any disks with grooves will always be more prone to this problem, the previous set of front ATE Power Disks were okay but the car had higher usage then so kept the disks clean. I'm not knocking grooved disks by the way, just pointing out the sort of use that can cause them trouble in the frozen North!

I think that a lot of rear disk damage is caused due to the fact that the weight distribution in a lightly loaded small car is always biased to the front so ther rears under present brake control thinking, can't be given any more work to do. My old VX CAV GSI 4X4 always braked "level", ie you could "feel" the rears getting to work - and that felt good, again a weight distriibution thing.

Edited 9 September, 201114 yr by rum4mo

As said, rear upgrade is mainly for looks, I got a full rear setup for £120ish iirc.

Matt

As said, rear upgrade is mainly for looks, I got a full rear setup for £120ish iirc.

Matt

disagree tbh, love my rearz

mainly for looks if u dont drive hard

This has been done to death. On the Fabia, with standard brake balance, almost all the braking is done by the fronts with the rears being braked only to stop the rear end coming round on you.

As standard, there is very little improvement in braking with upgraded rears. However, if you shell out for a balance box, where you can shift the bias of the brakes backwards, then the larger rear brakes do more work and it makes sense to have biggers rears. But then you need to disengage the ABS to stop it cutting in too early, or reprogramme the ABS controller.

The problem is always ABS.

There is even a school of thought that it's pointless upgrading the fronts as once the ABS kicks in, the car comes off the brakes anyway. If the standard discs will lock the front wheels (and they will!) then bigger discs are pointless.

mainly for looks if u dont drive hard

Yeah that's prob about right. Chris thinks his have made a difference too

Matt

This has been done to death. On the Fabia, with standard brake balance, almost all the braking is done by the fronts with the rears being braked only to stop the rear end coming round on you.

As standard, there is very little improvement in braking with upgraded rears. However, if you shell out for a balance box, where you can shift the bias of the brakes backwards, then the larger rear brakes do more work and it makes sense to have biggers rears. But then you need to disengage the ABS to stop it cutting in too early, or reprogramme the ABS controller.

The problem is always ABS.

There is even a school of thought that it's pointless upgrading the fronts as once the ABS kicks in, the car comes off the brakes anyway. If the standard discs will lock the front wheels (and they will!) then bigger discs are pointless.

Totally agree with your comments on the rear brakes, waste of time and money to upgrade.

With the fronts though, you are able to slow the car down more effectively (and frequently) without activating abs. Sure, if you're hitting the brakes so hard that your activating abs once then maybe nothing in it. Also, if you're braking so late (and hard) that abs cuts in all the time you're soon going to overheat your brakes - not to mention risk getting rear-ended if your out on the road!

If the size of disc's and pads and the force applied by the callipers really made no difference, then motor manufacturers being what they are would have a 'one size fits all' approach across their entire range to reduce costs.

In my own day to day experience 312's make a big difference to how the car stops from speed in normal driving, they also feel more progressive and have greater feel. Ok, so they may not slow me down quicker in a single 'emergency stop' situation but that's not the point.

What I do find amazing is the number of people who fit bigger brakes and then cheapo tyres!

Another plus on the 256mm rear upgrade is that the pad track is different so you shouldn't get that horrible 10mm rusty unused lip round the edge of the disk (like you get on the standard fabia rear brakes)

This has been done to death. On the Fabia, with standard brake balance, almost all the braking is done by the fronts with the rears being braked only to stop the rear end coming round on you.

As standard, there is very little improvement in braking with upgraded rears. However, if you shell out for a balance box, where you can shift the bias of the brakes backwards, then the larger rear brakes do more work and it makes sense to have biggers rears. But then you need to disengage the ABS to stop it cutting in too early, or reprogramme the ABS controller.

The problem is always ABS.

There is even a school of thought that it's pointless upgrading the fronts as once the ABS kicks in, the car comes off the brakes anyway. If the standard discs will lock the front wheels (and they will!) then bigger discs are pointless.

For a car on standard suspension I agree with you.

For a car lowered, even a minor (25mm) amount, the situation is less clear. There's a brake limiter on the rear axle to reduce the rear braking effort unless the boot is loaded. I think the Eibach install recommends this be tweaked after lowering to retain similar characteristics.

Talking about my car, the car sits far flatter through braking than when it was on standard suspension. There's less apparent weight transfer. I think the rears could do more.

When upgrading brakes, it's for reliability of operation with repeated applications. Rather than a one-off emergency stop scenario. Driven sympathetically, IMO there's no reason to upgrade anything.

However, jumping out of my impreza into the fabia, my level of sympathy seems inadequate, as do the brakes. Two or three medium-heavy stops or slows and I can feel the brakes going off.

Bigger brakes heat up slower, have more mass to heat in the first place and have a larger surface area windmilling around to cool them down.

The only real way to determine effectiveness would be to run on track and log front/rear brake temperatures.

However, I'm of the belief that once the fronts have been upgraded, on a lowered car, there's reason to consider upgrading the rears.

J.

With the fronts though, you are able to slow the car down more effectively (and frequently) without activating abs. Sure, if you're hitting the brakes so hard that your activating abs once then maybe nothing in it. Also, if you're braking so late (and hard) that abs cuts in all the time you're soon going to overheat your brakes - not to mention risk getting rear-ended if your out on the road!

This is where the other threads all bogged down as well. Hence my done to death comment. Ultimately you can only apply so much braking force before the ABS cuts in. That force isn't actually determined by the brakes, it's determined by the tyres and weight of the car. The argument then runs - on a light car, like a Fabia, with relatively skinny tyres, the 312mm brakes are overkill because you will always be limited by the ability of the tyres to apply the braking force to the road.

If the size of disc's and pads and the force applied by the callipers really made no difference, then motor manufacturers being what they are would have a 'one size fits all' approach across their entire range to reduce costs.

I'm pretty sure that on the scale VAG buy 312mm and 288mm brake setups the cost is not insignificant. For me, I reckon there are three factors that drive brake selection by manufacturers on a car - weight of car, contact patch of the tyres and looks. On a heavy car, you need bigger brakes. But you also need more contact patch to apply that braking force. Even F1 cars on slicks lock their tyres up.

In my own day to day experience 312's make a big difference to how the car stops from speed in normal driving, they also feel more progressive and have greater feel. Ok, so they may not slow me down quicker in a single 'emergency stop' situation but that's not the point.

I can't say what you can and can't "feel" though the brake pedal, but brakes are a relatively crude device and I am running a 312mm/256mm Octavia I setup myself, with a motorsports balance box and they purposely didn't upgrade the brake master cylinder when they fitted the balance box because they could have given me enough braking force to just have teh ABS on permanently if I touched the brakes. Brakes are not just about the size of the disks. They are about the abrasiveness of the pad material, what the disk is made of, how flat the disk is, how hot it is, the hydraulic pressure that can be brought to bear on the disk and, on bigger disks, how evenly that pressure can be applied across the surface of teh pad (whioch is why you have multiple piston caliper setups).

There is certainly some truth in the fade resistance argument as a bigger disk doing the same braking should run cooler than a smaller disk.

What I do find amazing is the number of people who fit bigger brakes and then cheapo tyres!

Again, I don't disagree.

Octavia I vRS rear brakes are a cheap upgrade if you need the brakes replacing anyway. Why wouldn't you do it, for looks alone?

There's a brake limiter on the rear axle to reduce the rear braking effort unless the boot is loaded.

That's news to me. I actually had Kenny McKinstry's fit a balance box to my car because I didn't think it had one.

I think the Eibach install recommends this be tweaked after lowering to retain similar characteristics.

I have the Eibach kit on mine and as far as I'm aware, they adjusted nothing when it was fitted.

Talking about my car, the car sits far flatter through braking than when it was on standard suspension. There's less apparent weight transfer. I think the rears could do more.

I do agree the car does not dive as much, but isn't that as much a function the stiffness of the spring rather than the fact that the car is lowered? Although we could be saying the same thing there from two different angles as the lowering and stiffening are functions of each other.

And I agree, the rears should do more, which is why I had an adjustable (not by me) balance box fitted.

When upgrading brakes, it's for reliability of operation with repeated applications. Rather than a one-off emergency stop scenario. Driven sympathetically, IMO there's no reason to upgrade anything.

Other than looks!

However, jumping out of my impreza into the fabia, my level of sympathy seems inadequate, as do the brakes. Two or three medium-heavy stops or slows and I can feel the brakes going off.

I have to say I don't know what sort of braking you're doing there. I did once have brake fade on my Fabia, but that was on an Alpine pass and I had been braking consistently hard for several minutes.

Bigger brakes heat up slower, have more mass to heat in the first place and have a larger surface area windmilling around to cool them down.

The only real way to determine effectiveness would be to run on track and log front/rear brake temperatures.

However, I'm of the belief that once the fronts have been upgraded, on a lowered car, there's reason to consider upgrading the rears.

J.

I still think you need to address the point about the ABS. You are basically saying that you can brake two or three times and overheat 312mm brakes without triggering the ABS? Even the standard brakes feel fade resistant to me.

Don't get me wrong. I always suggest upgrading the suspension (incl. RARB) and brakes before getting any form of power increase, and I run 370mm RS brakes on my TT, but generally, I reckon the rears do very little.

This has been done to death. On the Fabia, with standard brake balance, almost all the braking is done by the fronts with the rears being braked only to stop the rear end coming round on you.

As standard, there is very little improvement in braking with upgraded rears. However, if you shell out for a balance box, where you can shift the bias of the brakes backwards, then the larger rear brakes do more work and it makes sense to have biggers rears. But then you need to disengage the ABS to stop it cutting in too early, or reprogramme the ABS controller.

The problem is always ABS.

There is even a school of thought that it's pointless upgrading the fronts as once the ABS kicks in, the car comes off the brakes anyway. If the standard discs will lock the front wheels (and they will!) then bigger discs are pointless.

Unless of course you run a car like a B5 Passat with a heavy engine, I doubt if I could lock the front wheels in dry weather, I do agree from my experience of the 9N Polo, that this generic set of cars (Fabia + Polo + Ibiza) would really be in trouble if they did not have ABS EBD, especially in the hands of some "drivers" !

disagree tbh, love my rearz

mainly for looks if u dont drive hard

Agree with Like here.

Never felt the need to upgrade the rears until I started to do heavy late braking before corners on track days.

I've get Bembro front brakes and standard rears, you could feel the rear of the car getting a little loose, but only when really using them... so I am upgrading the rears.

Put it this way....go for a quick taz down a country road.....touch your rear discs....they'll be touchable, while your front discs will be untouchable.

But damn they look good!