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gypo86
24th August 2006, 07:37 PM
I have a problem with my ae86's front end shuddering under braking. This shudder gets worse the slower the car gets under braking and the steering wheel shakes.
I had Rx7 4spot calipers put on the front end by IDB in Melbourne.

The setup is three or so years old now but the calipers where reconditioned and the disc were new at the time.
The problem has gradually gotten worse over two and a half years. Other front end parts have been replaced; ball joints, tie rod ends but not the steering rack which I have been told is good? The car has koni's King springs 35mm drop and Whiteline sway bar
I have had the disc machined 3 times in a year and a half.

I think it the discs, mechanics have said there is no problem but the problem never really disappears after machining the discs and it soon comes back come. It has been getting worse.

My theory is that the slots in the discs are causing it?

You see the slots in the discs point in the same direction on either side of a disc, not a mirror image.

That is if you look at the LHS front disk through the wheel the slots radiate from the centre out in an anti-clockwise direction.
If you look on the inside of the LHS front disk it also radiate from the centre out in an anti-clockwise direction also?
Now get this, on the RHS its different sort of, the slots on both sides of the RHS disc radiate out from the centre in a clockwise direction ??

This does not sound normal to me!! The disc were made up by IDB, I think they fudged it but has it causing my problem.
I thought that the slots would angle away from the approaching pad as the disc rotates,

As in slots radiate out from the centre:

RHS outside in an anti-clockwise direction
RHS inside clockwise

LHS outside clockwise
LHS inside anti-clockwise


I also know that the pistons are sticking some or stiff (“not a problem" said the last mechanic?), which could be contributing to the problem, by possibly pushing the tip of the pad into the disc and grabbing the slot?

Please any advise would be appreciated, thanks

Gilly
24th August 2006, 08:07 PM
i'd be checking wheel bearings as well dude, seems like everything else has been covered. commodores had a similar rotor problem to this requiring constant disc machining due to excess runout and eventually revised rotors were released to eliminate the problem.

i'd check your wheel bearings, definately get the calipers reco'd to eliminate the possibility of them causing the problem. if fault continues look to replace your rotors.

i don't believe the slots would cause the problem.

gypo86
24th August 2006, 09:34 PM
I have checked the bearings a lot, they have seemed to be good all times in the passed ? It has corona bearings which I will change and do the reco on the calipers and hope for the best. The supra rims have been muted as a problem as well? As usual it's a process of elimination.
The last mechanic was talking about replacing the front end, struts and brakes but I'm not there yet. Thanks

mc68
24th August 2006, 09:41 PM
thats how slotted rotors are supposed to be. they dont mirror on the other side, that wouldnt be very effecient at all.

how grooved are the rotors...as i can guess they are either warped or quite grooved...the miracle of using harsh pads on standard rotors...if u can feel the grrove with ur finger then they are probably already fucked.

dirty_86
24th August 2006, 10:16 PM
with brake shudder in most cases its the disk being warped.. buh don't quote me on this.. lol

gypo86
24th August 2006, 10:35 PM
Yes when I took off the wheel I saw they were grooved a fair bit on the RHS. I think a machine is in order again at least, but will have to reco the calipers first! thanks

mc68
24th August 2006, 10:46 PM
well id skim the rotors first...unless you are sure the calipers need love too...

if the rotors arent undersize, then skim them, should cost much at all! if that doesnt work then get the calipers reco'd

Hen is a total nutcase
25th August 2006, 10:35 AM
They look like DBA rotors. Are you also using EBC greenstuff pads? I've heard of a few people having problems with this combination shaking.

Also about warped brake disks, have a read here (http://www.stoptech.com/tech_info/wp_warped_brakedisk.shtml)

Long but worth it.

Hen

riceburner
25th August 2006, 02:39 PM
Ive heard of slide pins not moving would/can cause steering shudder.

I believe the slide pin is meant to move and when it doesnt it throws balance out.

Another option maybe?

Steve

Hen is a total nutcase
25th August 2006, 04:23 PM
Being 4 piston, those RX7 brakes don't have slide pins. Though still a valid point for other calipers.

gypo86
25th August 2006, 06:40 PM
Thanks again for your input, I am starting to think it's the sticking pistons creating warping in the disc. The pads aren't green ones but they seem to be tuffer than the disc so that could be a problem as well? I also want to reco the steering rack to eliminate that as a angle. The car has a bit of negative camber ( 1.8 ) because of the ra60 struts which is another element to the equation? They were done by IDB

Looking to get the reco kit for the callipers soon and get the disc machined , but probably after get another car for a month, I plan to put in the 4age rwd in that time as well !!

Slide pins got me thinking about my motor bikes front brakes, might lube up the pins on that sucker.

gumbie
27th August 2006, 01:46 AM
Thanks again for your input, I am starting to think it's the sticking pistons creating warping in the disc. The pads aren't green ones but they seem to be tuffer than the disc so that could be a problem as well? I also want to reco the steering rack to eliminate that as a angle. The car has a bit of negative camber ( 1.8 ) because of the ra60 struts which is another element to the equation? They were done by IDB

Looking to get the reco kit for the callipers soon and get the disc machined , but probably after get another car for a month, I plan to put in the 4age rwd in that time as well !!

Slide pins got me thinking about my motor bikes front brakes, might lube up the pins on that sucker.[/b]



Yeah reco your calipers and replace the discs (if they have been machined three times in the last eighteen months they are probably undersized by now). Also if the discs are thin they will warp easier as well.



Nick

FLT LNR
27th August 2006, 03:32 AM
all falcon owners would feel your pain.

disc machining, as mentioned earlier is a quick fix, but the problem lies with the design.

this shuddering i know well when driving my AUII fairmont. the heat dissipation is so poor that when things are hot and you park it, the portion of the disc beneath the caliper cools slower than the rest, this causes warping.

pain in the ass all round. so yeah i only read this thread hastily but yes, a machining and new pads etc will get rid of the problem in the short term. and you can attempt to prevent it reoccurring ( according to my wog uncle ) by never parking the car immediately after extended braking.

hope to help,

macca

gypo86
27th August 2006, 01:20 PM
New discs from IDB are 300 approx and 60 if you want them slotted from memory, and its around 80 for the reco on the calipers , plus pistons if they are stuffed and I may have to replace the bearings. I will see what the bank balance looks like. It could be cheaper, they have cost enough already. 1700 to buy and install plus the machining. I have thought of selling the car over all of this.