Has anybody used the grooved type of discs on the Croma ? Are they worth the extra cash? As discs and pads have taken over from "you need a couple of brake pipes"on the MOT,( since the advent of stainless brake pipes), are they better?

In the dim and distant I have been able to reharden and skim discs (I worked as a metallurgist) but now they are so soft and the steel so low in alloys its impossible. This is why they are so cheap by the way so I am loathed to pay a load of money if they are not worth it and they wear down to minimum at the same rate . At present I am on the second set of pads on the original discs and the discs are at min 26mm and the car has only got 30000 on the clock!!

I'm seeing similar with my pads and discs - the fronts got me an MOT warning last week. They were new about 30k miles ago. I do drive economically too - anticipate, roll down to speed, avoid start/stop, etc. I try not to touch the brakes in general. I can't account for the other half's driving though.

What advantage are the grooves supposed to have? There's no need for better performance, as I'm sure the dinner plate sized standard discs are perfectly capable of a four wheel skid on any surface (well, without ABS anyway).

The story I heard was that the ban on asbestos in brake pads means they are much harder so grind the discs more. This may be a myth - perhaps it sounds better for the garages than saying that they're made out of cheap recycled bean tins (but still cost £££s).

you will need to use a low dust pad with grovved discs like ebc green pads.
i had red dot 20 groovs and ebc greens on my punto because i had upped the power from 80 bhp to 120 bhp
they are noisy and could do your head in if you like a quiet brake lasted over 70k miles though.
for my croma i just got brembo OEM spec discs an pads seem ok so far

The front discs are 28mm thick when new, and must be replaced when 26mm. i.e. you only get 1mm of wear per side out of them.

Is this normal? I'm surprised they've lasted more than a month.

Grooved or drilled discs do not offer any better braking performance under normal driving conditions. The groves and holes give better heat dissapation and thus eliminate brake fade in high endurance situations such as is found in motor racing.

So unless you are entering the millie miglia or planning a move to the Alps, I wouldn`t bother

Thanks for the info lads it looks like they are not worth it as my days of LeMans starts and doing the Monte Carlo are long gone!
Another interesting "theory" doing the garage rounds is that post asbestos the binding resin used nowadays is affected by the road salts used in winter causes them to soften on the surface , allowing the grit to stick and cause further accelerated wear to the pads. They have to be given credit for plausible excuses for taking our cash at MOT time !! All I know is that when the pads are getting ready I experience "flutter" at braking on the motorway from 60/70 which is very disconcerting.

Doofer said:

I'm seeing similar with my pads and discs - the fronts got me an MOT warning last week. They were new about 30k miles ago. I do drive economically too - anticipate, roll down to speed, avoid start/stop, etc. I try not to touch the brakes in general. I can't account for the other half's driving though.

What advantage are the grooves supposed to have? There's no need for better performance, as I'm sure the dinner plate sized standard discs are perfectly capable of a four wheel skid on any surface (well, without ABS anyway).

The story I heard was that the ban on asbestos in brake pads means they are much harder so grind the discs more. This may be a myth - perhaps it sounds better for the garages than saying that they're made out of cheap recycled bean tins (but still cost £££s).

Click to expand...

I have had a brake disc on the polyvac analyser when I had my Marea and believe me a bean tin is better bet than the disc!!

I had the rear near wheel off today to check the rear hub as the road noise has become louder of late.

The good news is the rear hub is fine , the bad news is that the excessive road noise is because the rear tyres resemble slicks (I don't know how that happened they were fine a month or so ago).

I also noticed that the rear discs are well worn and will certainly be borderline at MOT time (oh how the sun just keeps shining . )

However having searched the old internet I have found a reasonable supplier that can do both rear discs (that's the expensive 292mm vented version - you 8v diesel owners don't know how lucky you are) and pads for £65 delivered. Given that a set of discs lasts no longer than a set of pads we must now consider these a disposable item and work on the principle that paying mega bucks is not necessarily the best way to go.

The supplier is http://www.buypartsby.co.uk. Anyone had any dealings with them?

Little late to this thread but would contribute:

As Radlet6 says unless you are motorsporting your car then grooved/drilled discs provide no real benefit. Even in motorsport you can avoid the cost of running grooved/cross drilled discs by ensuring adequate cooling. This can necessitate the use of a more friendly air flow wheel to allow your ducted coooling air to easily escape.

The purposes of the grooves and cross drilling is not to allow better cooling but to allow gas to escape. Friction cuases heat. This heat causes 'gassing' at the pad to disc interface and at extreme temperatures pad gassing will to so great that the pad will actually aquaplane over the disc surface. Grooving and cross drilling allow this gas (cushion of air) to escape MORE QUICKLY.

Now grooves rubbing across pads causes increased pad wear. To compensate for this the pads are made of harder material. The harder the material lower the coefficient of friction and less heat is generated. Brake pads work better when warm/hotter.

Hard pads also equals increased disc wear.

You can see where this is now going......

For normal road use the grooved discs with harder/racing pads take time to warm up and provide good stopping power. They both also wear a lot more.

Also they generate noise/vibration as the pads are thrust into and over the groves. 8 grooves = highest noise, = highest vibration, = lowest cost. 20 grooves = the opposite.

Lastly, differential wear.

With smooth discs then as long as you have the minimum disc thickness then it does no really matter if the inside face has worn down by 1.5mm and the outside by 0.5mm (Croma disc are 28mm new and 26mm at end of service life).

With grooved discs then the inside grooves could be totally worn! This happened regularly on our track cars (Uno SX, Strada130TC) and you end up with decreasing performance and in many cases breaking imbalance.

The imbalance both in wear and braking is mainly due to caliper lateral float AND break pot quantity and distribution. Four or more pot calipers are of course the best providing equal disc squeeze and force distribution over the pad backing plates.

I had (a long time ago) a great discussion with Brembo about grooved and cross drilled discs for road car use (bearing in mind everything I written above). The guy I was speaking to totally agreed and said the only reason they sell them is because the public want to by them for looks, implied power and performance etc. Except for all out motor sport and high end sports cars they provide no advantage and can be detrimental to normal road going braking performance.

So what about your neighbours Porsche 911 with stonking Brembo Calipers fancy grooved and cross drilled discs. Simple. I bet you find a completely 'balanced' breaking system that will cater with shopping runs and German no limits autobahn driving. Uprated servos, tailored brake pad materials etc. etc. I still reccon though that there is a compromise window and your old Fiat Croma on stock breaking will out stop the 911 in certain lower speed, town driving, or no recent brake use scenarios.

Finally, any vibration put through the braking calipers/pots is bad news. Unlike an engine piston there is no lubricating fluid down the piston walls to protect both the bore and piston wall. So when you feel that vibration from grooved discs it is actually being rattled from the piston to the caliper bore walls and from there into hub etc. etc. Not good for the piston/bore walls.

Quick update:- went to collect the discs& pads and asked to look @ them, found that the discs were 285mm when the 150bhp has 305mm, never trust a woman with a computer!! The bloke at the desk said the price would be more, which you can expect but I was gob smacked when he said the 305s were £67 a pair inc vat against the £47 inc vat for the 285mm. We then had a question and answer session and it went "how can they charge nearly half as much again for a 20mm more material" Answer "dont know"
"Are they the same material?" Answer "dont know". You can see where the conversation was going!
The actual material is a slightly "stiffened" cast mild steel when I had the marea disc analysed and i`ve no cause to suspect that the more modern discs are any "stiffer"
In your conversations with Brymbo did you find any clue as to the vented discs being of a different material?

Hi

The 305mm discs fitted to the 16v are also thicker, 28mm as opposed to 25mm on the 285mm disc fitted to the 8v. A quick look on fleabay shows a £20 difference between 285mm and 305mm EBC grooved discs.

I take it of course that the 285mm discs they were trying to work up your kilt were vented and not solid. If they were solid they actually had the wrong end of the car.

Radlet6 said:

Hi

The 305mm discs fitted to the 16v are also thicker, 28mm as opposed to 25mm on the 285mm disc fitted to the 8v. A quick look on fleabay shows a £20 difference between 285mm and 305mm EBC grooved discs.

I take it of course that the 285mm discs they were trying to work up your kilt were vented and not solid. If they were solid they actually had the wrong end of the car.

Click to expand...

Hello:- Yes they were vented just the wrong size. The new discs have arrived at the lads garage who is doing the job on Thurs. We checked them for size and they are correct, however the £67 inc vat I was quoted has now become ex vat!! He is now double checking with the supplier(Brakeline factors) and I`m awaiting the answer with a view to an argument later. I feel my backs wet from somebody P***ing up it!!:bang:

Here's an interesting test to carry out if you can be bothered. Ring up pretending to be someone else and ask for prices for a set of front discs for a 2005 Vectra 2.0 Turbo or Vectra 1.8 and see what price you are quoted.

It's the same disc.

Radlet6 said:

Here's an interesting test to carry out if you can be bothered. Ring up pretending to be someone else and ask for prices for a set of front discs for a 2005 Vectra 2.0 Turbo or Vectra 1.8 and see what price you are quoted.

It's the same disc.

Click to expand...

Yep , the lad who is doing the job is doing exactly that as a check and will demand a refund on his account if they are less. He has opened an account with them only two weeks ago, they have been taken over and he wants to make sure they cant get away with owt.

The latest news is that the brake flutter was caused by the drivers side caliper was siezed on with the accompanying wear on the disc. the passenger side pads were only 25% worn and the disc was at 27mm thickness ie half worn. I agreed to run the freed off caliper and look at it later this month when the test is due. Anyone know the cheapest place for a new caliper?

Ok be careful here as there are two types of caliper. One for the 2.2 Petrol and the 8v diesel which are part nos.

LHS: 735350351
RHS: 735350352

And one for the 16v diesel and the 2.4, part nos:

LHS: 735374968
RHS: 735374969

I suspect that as yours takes the 305mm discs it is the latter. These are the part numbers for the full caliper assembly. However you will need the part number for the cylinder unit only. Which are:

1.8 and 8v diesel

LHS: 77363596
RHS: 77363687

For the 16v and 2.4

LHS: 77363628
RHS: 77363629

If it is the last one of this list which you require then you are in luck:

http://www.ebay.co.uk/itm/FIAT-CROM..._CarParts_SM&hash=item45fd711f16#ht_529wt_905

He does have a returns policy if it isn't the right one.

Just for further clarification

The first (a GM part) looks like:

and the second (a Lucas part - or the one that should be on your car) looks like:

Thanks for the info R6 its the lucas part as described. I saw the e-bay listing last week and he has now relisted it. Will keep you posted if I have further probs , but as i type the car is a lot better when freewheeling down one of our many hills than it was , it was the slow onset of the problem that showed you dont know whats going on. I would have expected to have felt something through the steering wheel but I didnt.

Actually now I come to think of it when I replaced the front pads last year the offside was worn more than the near side. This baffled the FIAT garage as the caliper was working fine. Sorry for not mentioning this before :bang:.

I wonder if it is something to do with the traction control or ESP?

Interesting. From my recent MOT warnings:

BRAKES: Offside front brake pads worn to 4mm. Nearside front brake pads worn to 8mm. Offside front disc close to min spec.

Mine had all new pads and discs 33k miles ago.

Are we identifying a characteristic?

I think mine has been rubbing though - I've heard squeaking recently when not braking. I'm going to have a decent length of drive tomorrow without braking and check whether the disc is warm after I stop.