Grooved v Drilled v Combi Grooved+Drilled v Blank Brake Discs v OEM!

CL500Wizard

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I'm trying to get some views from the MB owners what they thought of the different types and makes of the discs, if they have tried them. From what I've read on the forum, generally people either go for MB supplied or oem equivalent (zimmerman etc) replacement brakes and it would also be very interesting to read opinions of those who have gone for a non-oem setup (discs specifically).


As for my view of the different types of brake discs (all are vented):

Blanks: My usual choice for most cars (other than my track car) with a good set of fast road pads such as Frodo DS2500. No issues with warpage unless the disks are cheap ebay no-well-known brand type, people bedding in wrong &/or abusing them by not letting them cool down after spirited braking - usual suspects are the ones who brake hard coming to a traffic light and then leave their foot on the brake transferring more pad material on to the hot brakes and less heat dissipation causing either warpage or quicker pad disintegration. However this can and does happen to all disks due to user error!

Drilled: Personally I hate these discs and something I would avoid unless no choice. My CL500 standard brakes are Drilled on the fronts and I will not be replacing them with alike. These are the worst for the spirited driver (and track use), and have seen plenty develop cracks (including a fully bedded in set developing cracks and badly pad glazed on my track car during just 1 day on track, same make Grooved lasted many more track days and quite a few pad changes) - several makes have been tested against just the same make Blanks and proved to have a much shorter life, and this is why suppliers to motorsports do not supply these - bling is some describe these to be!! These disks have poor integrity due to drilling and not as cooling efficient claimed to be in addition to not help reduce pad glazing. I don't know why Merc decided to put these on a £60K+ car :rolleyes:

Combination Drilled and Grooved: These are usually the best brakes (dependant on material), and a lot of fast production cars (Porsche, DB's) come standard with these. However if you source a cheaper make which is made of poor quality materials, these can be as bad as Drilled.

Grooved: These are my favourites for upgrading discs. They allow better pad bite better than all of the above, and additional grooves (compared to combi) help release the heat very well too and substantially reduce pad glazing.

2 makes that I always use are EBC for Blanks and BlackDiamond (black in colour as well) for Grooved. EBC only do blanks for my car versus ATE (from EPC who say ATE are oem for MB) which are drilled. BlackDiamond lists discs on their website but doesn't say if they are Blanks, Combi or Grooved - still looking for a supplier who can get the Grooved ones for the CL. May just slap on EBC blanks (which are more expensive than ATE drilled!) with Frodo DS2500 or EBC RedStuff pads and see how things progress.



What are you thoughts and experiences?
 

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I have to admit that my drilled disc can fail in odd ways.

I replaced with Zimmmeman at£98 for the pair
 

Xtractorfan

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Certainly for track use drilled discs are not really an option, but in general their use on a road car has never been called into question.. Grooved no doubt are a better all round disc and would be the ideal upgrade for the spirited driver, it is claimed that drilled discs do not heat up as much and cool down quicker than the solid or grooved disc.. also not as prone to loosing the braking force due to water on the discs...Interesting topic
 

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Certainly for track use drilled discs are not really an option, but in general their use on a road car has never been called into question.. Grooved no doubt are a better all round disc and would be the ideal upgrade for the spirited driver, it is claimed that drilled discs do not heat up as much and cool down quicker than the solid or grooved disc.. also not as prone to loosing the braking force due to water on the discs...Interesting topic

Be nice if some more answers come in on this, it is interesting
 

wireman

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I am under the impression that the cross drilling allows the gasses produced under high load braking to escape and not try to lift the pads, whilst the grooving allows dust to escape and prevent squeaks/grunt noises and by coincidence indicates how much disk wear has taken place.

Cross drilling of motor cycle disks is common and less prone to cracking but the disks are thin section alloy steel not the iron used on car systems.
 

HelpThisDude

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I must admit, when I was competing, I only used a larger solid, vented disc, 4 pots calipers.
I was in Group C with a very heavy car (1250 odd kg), but I could always out brake the Group A cars into a corner. Great at Lydden hill.
Drilled were always a no-no among most in the paddock, grooved were the best for deglaze and de gassing, while keeping overall structural strength, but I am going back some time.
Maybe drilled discs are better now?
I have had drilled discs on a road car & bike, (and soon will have again), I have never had a crack form between holes, althought I know it happens.
I know that it is not possible to recreate the stresses of ‘track’ drive/braking on the road but, at an irresponsible age, I think I did drive/brake quite hard.
I read recently, that a company called Nitrac (who?) are cryogenically cold treating their discs rather then heat-treating them. Some touring car teams are using them (so Nitrac say), but touring car teams chop-and-change all the time with deals an offers.

I'm going to keep my eye on this post, i'm sure some professional will soon have all the answers.
 

Bolide

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I'd lay a medium-sized bet that most people couldn't feel any difference between the various types of brake discs when driving on the road

Nick Froome
www.w124.co.uk
 

wireman

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Sorry JT but I must disagree.

The gas is produced in the gap between the disk and pad, time does not come into the equation except in clearing the gas away hence the holes being put there in the first place as somewhere for it to go, from where it can squirt its way into the atmosphere just as soon as the pad clears the hole.
The problem only manifests itself under very high brake loads.
The pads do exude large quantities of gasses as they are wearing at high temperatures

It is a known problem on aircraft disk brakes (made of similar materials as road vehicle brakes) which are called upon to shift horrendous amounts of energy at temperatures in excess of 600C, believe me there is time in the 10 milliseconds or so per wheel revolution to generate a sufficiently large pressurised gas cloud between the pad and disk to cause troubles with brake efficiency reduction due to the pads lifting slightly. The amount of lift is in the submicron range but it is there.

Cross drilled disks can hold water in the holes which can turn to steam as the brake is applied and cause erratic behaviour due unbalanced wheel to wheel retardation forces in the initial stages of heavy braking in wet conditions (you would not want that on a holiday jet would you?), it is a small effect that lasts for a very short time but does make the vehicle twitch (and the driver) to one side as the water clears from one brake before the others.

There is no way that cross drilling can help with heat disipation, no cooling air can flow through them, the holes face the wrong way and in reducing the mass of the disk assist in increasing the disks temperature, to me they are not needed except on the highest performance vehicles where it is essential to keep the sprung to unsprung weight ratio to an absolute minimum.

My choice would be radial vented disks with surface grooving having a geometry that ensures even disk wear. Not a hole in sight.
 
OP
C

CL500Wizard

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  • Thread Starter
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I'd lay a medium-sized bet that most people couldn't feel any difference between the various types of brake discs when driving on the road

Nick Froome
www.w124.co.uk

emergency braking happens on road all too often and thats when one really needs good brakes ........ same car, good grippy tyres, same brake pads (decent ones at the very least), all bedded in properly but one on cross drilled discs and other on grooved .... ask a normal driver (who just slams the brakes) to do emergency braking at different speeds 50mph, 60mph & 70mph (or higher if the private road is good stretch) on both cars and then tell the difference

ABS will have a play in it (non-ABS cars are best for this test) but even then the difference should be obvious.

During pad bedding in procedures on blanks and grooved, one can tell the difference as well. My friend and I own the same spec and model car, same tyres, same brake pads, no ABS, changed pads and discs (his on blanks and mine on grooved) same day and went for bedding in drive (I drove both cars while he passengered). a few 60mph-0 soft stops followed by 2 to 3 60mph-0 hard stops, on the last hard stop it was clear that grooved stopped the car in shorter distance and one could clearly feel the difference.


how much is a medium-sized bet (on emergency braking though)? ;)
 

joe1972

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I don't know whether it is still true, but quite a few years ago I bought and fitted some Tarox grooved discs on a Mazerati BiTurbo. I ignored the Tarox fitting instructions as they suggested I fit them the wrong way around! (grooves spinning into the hub)...I'm guessing braking efficiency would be great with the car in reverse?! lol
Wish I'd kept those instructions. I'm guessing Tarox probably changed them.
Worked well but was not sure how well they lasted, as I fortunately got rid of that frankly awful car soon afterwards.

To be honest for my use now I tend to stick to no 'bells n whistles' solid discs with decent pads. The only thing that really pee'd me off about the w124 was some idiot had gone and painted the calipers with red paint, when the money shouldve been spent on new pads and discs!
 

Number_Cruncher

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>>how much is a medium-sized bet

As one-off emergency braking, under full pressure, is solely limited by tyre to road grip rather then the brake itself, then, I agree fully with Bolide.

If you see a difference in a one off emergency braking event, it means one or both of you are not pressing the pedal hard enough.

It's only when you repeat the braking, when there has been a significant heat load that the difference will emerge - and if this difference is emerging on the public road, then, I want to be nowhere near it!
 

stats007

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Proper cross-drilled discs are actually cast that way - Porsche used to do this but now the warranty claims indicate they're not...

The best brake feel I've had is with solid discs and Mintex C-tech pads. The worst with EBC reds and OEM drilled discs. Tried EBC on a few cars (Porsche/Maserati) and they were utter rubbish.
 

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The best brake feel I've had is with solid discs and Mintex C-tech pads. The worst with EBC reds and OEM drilled discs. Tried EBC on a few cars (Porsche/Maserati) and they were utter rubbish.


Maybe you fitted the wrong ones for the car, I and thousands of others would not use anything else
 

stats007

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Thousands of people bought the ebay resistor and electric supercharger off of ebay...

I did some research into EBC - the pads are rebranded low quality material imported from the US. In no way is the quality the same as Jurid/Pagid/Textar/Ferodo/Mintex etc.

Less brake dust because the discs wears rather than the pad itself...
 

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Thousands of people bought the ebay resistor and electric supercharger off of ebay...

I did some research into EBC - the pads are rebranded low quality material imported from the US. In no way is the quality the same as Jurid/Pagid/Textar/Ferodo/Mintex etc.

Less brake dust because the discs wears rather than the pad itself...

Totally untrue, the dust that comes off, is not like any other pad, other than the other new type on sale in the USA.

The figures on a rolling road show no difference on the green pads and better with the Red.

I find it hard to believe that you made that statement
 

stats007

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Not untrue at all Malcolm. There was a technical presentation at MechanEx earlier this year.
 

Number_Cruncher

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The important thing with replacement brake friction linings and pads is to ensure compliance with ECE regulation 90. If the replacement parts do not carry this certification, you are modifying the car, and should inform your insurer.
 

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