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Discussion Starter #1
I have an idea on a probable cause of brake vibration , has anyone ever actually dial gauged the actual runout of suspected warped disc's ?
Excuse the mystery , I will reveal what I think when I've had some replies.
 
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Discussion Starter #2
BTR do it to mine each time they replace them.

Details are:

Old
Left front: inside face:0.6mm outside face:0.4mm Total run out:1.0mm
Right front: inside face:0.5mm outside face:0.2mm Total run out:0.7mm

New
Left front: inside face:0.01mm outside face:0mm Total run out:0.01mm
Right front: inside face:0.015mm outside face:0mm Total run out:0.015mm

Do tell your theory!
 
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Discussion Starter #3
bloodaxe

thats the same figures i have
it s not that much runout when cold but my quess is when hot the runout is much more

tell the story EVO BOY

regards

andre
 
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Discussion Starter #4
I was told because of the small hub/big disc of the Evo, the tiny runout amplifies the wobble, which would not be noticeable on a normal car.

I too suspect that hot, runout is worse.

Go on, let us into the idea, oh man of mystery!
 
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Discussion Starter #5
OK , here it is , I've done some research into brake problems and my conclusion is an effect known as DISC CONING .
Apparently , when a large brake disc heats and cools and is not correctly designed OR , produced exactly to design and drawings , the disc takes on a coned shape if u cud look at it cut thru at 90 degrees to centre axis.
This absorbs hydraulic pressure and distorts the pads before they can exert the full brake pressure (hence reports of a long pedal perhaps?) , and the disc will overheat due to the reduced contact area , hence warping ?

I am now convinced it is not due to inadequate cooling , because when I have examined the disposition of brake dust with the car on a 2 post lift with wheels off , there is minimal dust on the inside of the calipers , suspension components etc , but a huge amount on the outside (wheel side) of the caliper and down the sides of the car! This wud indicate that a positive airflow exists past the caliper and disc.

This requires further investigation, as in sectioning rogue disc's , looking at pads etc , but , I reckon this cud be the problem.

The thing I cannot explain is why some drivers including myself , do not have any problems , unless driving style or bad disc batches are the culprit.
 
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Discussion Starter #6
evoboy

bad batch of discs i don t think so

i have tried ap 2 piece discs and porsche discs both warped heavely
it s combination of the whole system brembo caliper discs hub etc. thats my quess

regards

andre
 
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Discussion Starter #7
OK , lets break it down , why wud it be the caliper or the whole front brake system ? The components are used on other vehicles without a problem , for example the Skyline R34 GTR ,a much heavier car, do we know of a problem there? I don't. You are having problems with other disc's , are these disc's similar in design to the Brembo disc , excluding 2 piece with alloy bell which obviously arn't.
Cud there be faulty calipers out there , remote I know , but has anyone checked ?

I approach it this way because the problem seems to afflict drivers of all types , moderate to extreme , in many types of conditions and then some cars are completely unaffected , so there has to be an esoteric reason for the problem , not simply a crap braking system , which it isn't.

Remember also that no magazine test has ever commented on a) poor brakes or b) brake problems , and these guys really push cars to the extreme.

Really I don't think that the braking system is inadequate , and I also don't think that it is neccesary to replace the system with 6 piston AP kits to cure the problem , more investigation is required , preferably controlled tests with detailed data aquisition.
 
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Discussion Starter #8
Evo boy youre right but so far no one found a solution to the problem the money i have already spend on discs and pads i could have a 6 pot kit for the rear also.

i have never doubt on the braking force the brembo s produce but i am all out of answers here

i wish i could find a solution for the brembo system then i had never bought the ap 6 pots but i don t want to spend 400 guilders for trackday and leave after 3 laps because my discs are warped again.

the ap discs with alu bell warped on the circuit in 5 laps the dragons warped on the road so in my opinion it has nothing to do with the disc everything warps on my car does not matter what kind of brake pad i use

Try this:

Maybe some brembo calipers have a differance in braking pressure in one side of the caliper and because of the differant pressure the disc warps (it s a thin story but worth a test)
bad batch of calipers maybe? i am 99% sure it s not a disc problem

Maybe the caliper and disc design are not good and produce to much heat in centre of the disc(bell) and put so much heat in the wheel bearings the the wobble comes from there (i know pretty thin story also but who knows)

i am just thinking guys so don t kill me

regards

andre
 
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Discussion Starter #9
I don't want to #### anybody off, but the fact that some people warp their discs all the time, regardless of whether they are moderate or extreme drivers, like Evoboy said, suggests to me that this is a driving style problem...
Andre, I don't want to patronise you, but could you explain, how you brake (before the corner/in the corner/ etc.) and what exactly you do once you come off the circuit and when (apply handbrakes/stand on the brakes to stop rolling/ etc.). I know that especially at the Ring most parking spots have an incline, so one has to brake to stop the car from rolling. Maybe this way we can get a profile of the disc-warper.
 
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Discussion Starter #10
Micheal Please i have started racing karts when i was nine years old and did 1 year formula ford and then 2 years formula renault so i know how to treat my brakes that really is not the problem on my car

i brake very hard to almost locking up my tires sometimes some trailbraking into the corners to go sideways every disc gets warped soner or later on my car

99% sure this is not a disc problem ok the discs get warped but there is a reason for it and it s not comming from discs but the result is warped discs

ps i never stand on brakes in pits
i always heat my discs up for 1 lap
i always cool my discs for 1 lap

the heating and cooling i never did with my ap 4 pot system never had any warping so there must be someting wrong with the brembo setup it s clear as cristal.

next test should be new brembo calipers they cost a fortune for almost the same price you have complete ap setup so the answer in my case is pretty easy

regards

andre
 
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Discussion Starter #11
I think that even if expensive the ap 6pot kit is a good solution.

Anyway I have warped my discs when the evo was around 30000miles, they were used by the way, and when I warp them I was using pagid brake pads and I really insist on the brakes when they were red. Then I slowed down as the fluid was boiling and I loss all the braking power.

Could the problem be the evo gsr hubs?
Is there any evo rs driver that usally have disc warping problems?

In the workshop manual they are talking about rs option special hubs,maybe they are already fitted to some evo rs?

I don't have warping problems with my new ctf separate alloy bell discs even when they became red,but if I had this problem I would try to find these rs special hubs!
 
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Discussion Starter #12
Andre, like I said, I didn't want to patronise you, but I still think driving style is a factor in this and maybe we could find some common pattern with the people that warp their discs. The problem is that this would probably require some very detailed data, which we probably can't get like this. Like Evoboy said, this would require tests with proper equipment and different types of drivers present, basically like a proper car industry R and amp;D effort, so impossible for us. One thing that is also sure is that there are no problems in Group N with the system, so how hard people drive is not the factor that determines why discs get warped...
 
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Discussion Starter #13
I think the Group N has no problems as they change discs so many times in a short period so you can't really compare it let's say to a lap on the Ring where you reach much higher speeds than in Group N. The warping always happens on my car when braking hard above 160km/h below I can abuse them as I want without warping them (at least with the Mintex pads)
In my case I'm sure it has to do with my driving style and I have to change it. In André's case it's another story as he's a real racer and is far superior than me.

Just my opinion

Mike
 
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micheal i am not mad at you :)

maybe it has to someting with driving style but i can hardly believe it the rallyteam were i bought my rs2 brings boxes full with discs to the reskimmer so a rallydriver warps them too

if it has something to do with driving style why does a 6 pot work with every driving style

regards

andre
 
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Andre, I didn't think you were :)

The six pot works cause it can cope with whatever the extra stress factor is. This probably means that there is no alternative for hardcore discwarpers but to buy the AP sixpot...

Scoobymike,
how did yours warp? Did you brake from over 160 km/h to slow speeds and it was warped straight away, or did the brakes fade first?
 
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Discussion Starter #16
In an attempt to make some progress with this problem I need to aquire as many sets of warped/suspect discs as possible with information on there use up to the time they were replaced , source and time of purchase etc etc.
Then in the near future I wud like to set up a test program at a circuit venue using drivers with and without the warping problem.

I will make efforts to obtain foc brake components for the test from the relavent companies to minimise the cost for everyone involved.

Obviously this is only the base outline of an idea , but with good cooperation we shud be able to resolve this.

So , send me some disc's to start with.
 
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Michael

it happened at the Schweden Kreuz. I came with around 210-220km/h and broke down to around 150-160km/h and in this moment horrible judder. I have to say it was after several runs and I expected it to be earlier. No fade during two days on the Ring. The pads were absolutely fine but discs got blue including the hubs!!! :blush: I tried to avoid to stand on the brakes when we turned on the track (during section training, no public allowed) and let them cool off as good as possible. They recovered but as soon as they get the same temperature when they warped judder comes again.

My setup was the following:

- skimmed discs
- Mintex FR 14 cut down pads
- standard brake lines
- standard fluid

Hope this helps a bit. Currently I can't send the discs to the UK as I'll give them their last skim because I think I go to Aneau du Rhin in September for another trackday as I got the fever now:D and gonna destroy them there completely.

During my Ring days I met the coordinator of Ralliart Germany Mr Reiss and he told me that the discs have to warp once and then get them reskimmed on the car. They use the Pagid Blue pads and don't have any problems.

Hope this is a bit of help
Cheers

Mike
 
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Interesting thoughts, I have now done 8 track days 16k road miles. No warped discs ( and if you think I drive like a wuss, try and keep up :D Evoboy may have a point so keep us posted.

Kevin A
 
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Discussion Starter #19
This is definetely something quite complex, because if Scoobymike warped his disc while braking hard from 210ks to 150ks it is quite worrying, as braking like this will happen on almost every trackday. I don't think the Nürburgring will have any special effect, because if you do a trackday on any track, you'll put the brakes under about the same stress. Well, I'm out of quick-fix ideas...
 
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Discussion Starter #20
Guys
I am not an expert, just an enthusiast like most of the rest of you. I have been reading these braking threads for a while and it seams that its the high speed braking that's causing the problems could it therefore be that it is the ally bell that is causing you guys all the problems? Is it posible that the bell gets so hot that it is unable to support the disc adiquatly? Do any of the rally teams use steel bells?
As i say it's just a thought.

Sean
 
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