wobble, vibration, grooves and cross drilling

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moose
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wobble, vibration, grooves and cross drilling

Post by moose » Tue Mar 15, 2011 9:05 pm

Sorry not a night out with Neil,

it's a bit lengthy but may interest some folk.

The following text is a collection of quotes and statements from a number of brake disc manufactures in the UK and Europe. These guys have responded to a number of questions I asked via email one Friday afternoon after looking at all the discussion on various forums about grooved disc, hard pad and warped discs. There answers where all given in good faith and although it is a bit like asking the banker why the banking crisis happened, I have no reason to disbelieve them, I also have no way of double check all answers so I will not be held responsible for inaccuracies in the information below. At least one said the answers he gave where his opinions and not necessary those of the company he work for. I would like to thank those engineers and managers who responded from. TRW, AP Caparo, EBCbrakesuk, TMD Friction (Bremtech Textar, Mintex, Pagid) Honewell (Jurid, Bendix) Eurac, Brakes international, Brake Engineering, Nitrac, Mtecbrakes, and National Auto Parts. Honeywell who make Jurid and Bendix brand have offered to set up a discount scheme for members which I will follow up and let you all know how it goes.

Pad type
The consensus is the best aftermarket pads are from any manufacturer that makes for OE. such as Ferodo (premium only - not FAL); Jurid, Bendix, Textar, Mintex, Pagid. others include. Lucas Apec and lockheed
These will generally use OE Factory production cells, same "family" of friction material, quality control standards etc. and meet regulation 90
EBC – say pad type is personal preference on braking, their standard pad will be similar to OE, greenstuff will be a first stage upgrade for someone who wants more response and yellow stuff is the ultimate upgrade for high performance usage and towing, EBC pads are made in their own factory in in Bristol
One engineer commented:
“There are many suppliers of friction material, most not even manufacturing the product, therefore limited to nil in terms of test capability. LR produce for the army as well as on road vehicles, they use one grade of friction for all applications.(I would question this ed) Pads termed as harder or coloured material are marketing gimmicks not real science. If they were I am sure LR would offer at least some of them. There are many cheaper pads, sometimes even dearer pads but LR still use the same suppliers, there is obviously a reason for this, they have to be sure everything works to its full potential at all times!”

Comparison on wear I am lead to believe is almost impossible to quantify as if depends on the environment they are used in, “Harder” pads do not absorb heat as well as the OE material, are likely to cause extra wear on discs and when too hot have far worse fade characteristics. One of the main issues with braking system is noise, I know one OE supplier spent many months working on reducing the noise (squeal) on the Discovery with different pad materials and pad shapes.

It is worth looking for Reg 90 Approved Replacement Disc Brake Pads – Reg 90 is a brake safety regulation outlawing cheap, non conforming friction materials. The new regulation which requires “type testing” of each brand of brakes compared to the original equipment on the exact model of car. The regulation affects only models of motorcars and trucks registered after the 1st January 1999.
One final comment on pads “If standard pads are not fading then there is limited benefit in using upgraded pads.”

Disc- Run out
The recommended run out for disc varied between 0.15mm to 0.3mm depending upon application, on this everyone seemed to be in agreement. Although the unit of measurement varied from mm to thou’s and microns .
A couple of comments where;
“when fitted to the vehicle the run out can be up to 150 microns”.
“Some run out is necessary to prevent the pads "dragging”

Disc- Warpage and Vibration
In answer to this question all the responses followed the same line:
“Brake vibration that occurs around 2-3000 miles after fitting is always an incorrect fitting procedure the instructions on the box must be observed exactly or this vibration will occur
Discs never warp it is always something else
It is ESSENTIAL that the vehicle hub is thoroughly clean, particularly around the bolt holes. Then lightly smear the cleaned surface with non-metallic grease (stops the early rusting).
Our testing on "warped" discs before and after cleaning the discs shows the amount of run out to drop by up to 3 times”.

“Avoid leaving the foot brake on after a prolonged stop. heat transfer from pad to disc can temper the metal and result in a different wear rate.
The higher quality disc is more resistant to these abuses.”
“Vibrations are felt through the car with a pulsating pedal when braking. ‘ Pedal bounce’ If the steering wheel vibrates also, this tends to indicate the problem is with the front brakes.
“Cause: Usually due to variations in disc thickness - DTV. These variations in thickness are usually the result of excessive disc run-out, caused by mating the disc to dirty or distorted hubs. When driving (brakes off), the pads are normally in close contact to the disc. However, when there is excessive disc run-out, the pads scuff the ‘high’ parts of the disc on”
“Solution: Replace the damaged discs; but when doing so inspect the hubs properly and use a dial gauge to ensure disc run-out is less than 0.1mm (0.004”). This will avoid damaging the new discs. Alternatively, if the discs are only slightly worn, they can be machined on the car so that they run perfectly true”.
“Facts: If you fit new discs and they’re great for the first 1,000-2,000 miles and then you start to notice a very slight judder developing, you’ve probably got DTV caused by run out”.
“If you fit new discs and they immediately judder, then it’s probable (although very rare) that they have been machined incorrectly or there was a flaw in the casting”.
Grooves / Cross drilling
Here most agree, the only two comments that are different do come from manufactures of grooved discs, the first comment “ For off roading grooved discs would be an advantage as they aid with water dispersal. This is of particular advantage given the large pad area on Land Rover Discoveries”.

Whilst another went on to say
“It really is personal choice as grooves will give better braking at the extreme of temperature normally only found on a track day so for your cars it really is personal preference for something that looks better , Off road it is not recommended to use grooves or drilling as it all fills up with mud etc and this then spreads across the disc so it is better to use a plain disc for off road”
The more standard line was – “Grooves & cross drilling will make no effect on normal driving, other than to make the braking noisy and to severely reduce the wear life of the pad. Cheese grater syndrome”.

further comments - “Grooving and drilling help with cooling and pad de-glazing. Whether it is worth it for any individual application depends on the use to which the vehicle will be put and the preferences of the driver, so to some extent this is a "how long is a piece of string" question I'm afraid. Drilled/Grooved discs will give a better performance in high stress situations, eg track use, or with high performance or heavy vehicles. It is in the latter area I suspect that might be of interest to your club members. We certainly have a number of customers with range Rovers and Land Rovers who have found our discs to be of benefit with heavily laden/towing vehicles used on motorways for example.
In low speed applications I would not see much benefit to grooving and or drilling unless the vehicle is so heavily laden that they are experiencing brake fade with conventional discs and pads”

“Cross drilled brake discs are designed to increase cooling of the disc. The holes drilled in the disc allow more air to flow in and over the disc which in turn helps reduce heat ‘build up’ which reduces brake fade, popular for fast road and semi track day use”.

“The grooved version of brake discs are designed to increase friction between disc and pad which increases stopping power, popular for fast road and semi track day use”.

“Grooved or cross drilled discs are designed for fast road or track use and its unlikely you would notice any benefit in off road use”.

So of 11 responses only one would suggest grooved discs off road, but as the second guy said it’s personal choice.

Disc material

Like most brake discs that are intended mainly for road use, discs are made from grey 220 grade iron. With a hardness of around 26 rockwell, some special disc are made from a slightly higher grade.
The design of these discs has not changed since disc brakes where developed, pad construction however has changed dramatically and as we all know the modern none asbestos pads will eat through disc at the rate of 1:1 in some cases, this was supported by all who commented on disc wear.

One interesting comment
“Brembo brake discs are used for Land Rover applications. The reason for this is that Brembo are the only brake disc manufacturer who guarantee to replicate the Original Equipment quality in their discs sold into the aftermarket”.
A couple of final notes
O/E discs mainly are manufactured in Europe from castings conforming to DIN1619 and GH190. They offer specifications consistent with original equipment and provide enhanced braking performance. world’s leading manufacturers, including Bremtech, Brembo, Lucas, Bendix and Bradi, If off road and / or towing then life expectancy of brakes will be reduced when compared to normal driving but perhaps the adage:- "You get what you pay for" - rings somewhat true. And the the black deposit seen on the surface of disc is more often vitrification ‘burnt on’ pad material
:tumbleweed:


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Re: wobble, vibration, grooves and cross drilling

Post by Neild » Tue Mar 15, 2011 9:09 pm

moose wrote:Sorry not a night out with Neil,

Cheeky :censored: :surprise: . Less of the wobble!!!!
moose wrote: have offered to set up a discount scheme for members which I will follow up and let you all know how it goes.
Your not a member though........ YET :whistle:


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Re: wobble, vibration, grooves and cross drilling

Post by anglefire » Tue Mar 15, 2011 9:16 pm

Very interesting read - particularly as mine were replaced by LR before half term and now are squeaking. Which they couldn't hear today - until the brought the car around from the carpark this evening :headbang:

I have a complete set of Standard EBC pads in the garage ready for the next change. I'm still happy with my choice after reading this :thumbright:


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Re: wobble, vibration, grooves and cross drilling

Post by Bodsy » Tue Mar 15, 2011 11:54 pm

Geeky but useful insight Chris :thumbright:
Interested in some proper discount :-)


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Re: wobble, vibration, grooves and cross drilling

Post by Paul » Wed Mar 16, 2011 12:07 am

:censored: the discount, this information on it's own is fantastic :thumbright: :thumbright: :thumbright:


Thanks for taking the time to make these enquiries and put all the responses together Chris, a truly excellent post :thumbright:

And yes...I'm also a geek :lol:



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Re: wobble, vibration, grooves and cross drilling

Post by benp » Wed Mar 16, 2011 4:35 am

Looks like a lot of work went in to that CG nice post thanks

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Re: wobble, vibration, grooves and cross drilling

Post by JF Lux » Wed Mar 16, 2011 7:24 am

good info :thumbright:

how about cleaning up the thread and making it a "sticky" ?


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Re: wobble, vibration, grooves and cross drilling

Post by PhilHunt » Thu Apr 07, 2011 12:05 am

Excellent post Chris - interested in the discount aspect so keep us posted as I'm shopping around for new discs at the moment. I have slotted and drilled discs on my D1 but won't now be fitting them to the D3!Are there any views on the quality of Britpart and Bearmach discs????


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Re: wobble, vibration, grooves and cross drilling

Post by moose » Thu Apr 07, 2011 2:00 pm

I didn't ask Britpart as I am fairly sure the discs come in from overseas, and Britpart are of course not experts in discs and pads they can only give there opinion like you or I.
it would be interesting to know who makes the discs, although I doubt they would tell me.

If you are after D1 or D2 discs I could get these as we coat hundreds every month for the offical LR supplier, I can ask for a set if needed. D3 are still made by Brembo in their Polish plant, I cannot get those.

The Discount I have followed up, as soon as the UK agent has his web site set up (don't worry they are not Chinese, they are made in Germany, on the same line that do O/E for Mercedes, BMW etc, I am not sure of which brand name they will use)
I will let everyone know. I have fitted their front discs and after a couple of thousand miles they are fine.


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Re: wobble, vibration, grooves and cross drilling

Post by moose » Thu Apr 07, 2011 2:06 pm

Fitted front disc
Image


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