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Steering judder when braking at speed.

Old 21 May 2019, 06:39 AM
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davemar
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Default Steering judder when braking at speed.

Recently I've started getting steering judder when braking firmly from high speeds (70mph). I don't get it at lower speeds. I haven't changed anything on the car recently.

It's a 2005 WRX wagon with 4-pots at the front.
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Old 21 May 2019, 07:52 AM
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Warped discs are common for this.
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Old 21 May 2019, 10:16 PM
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That was my assumption, but wondered whether warped discs would shudder at all speeds, or just at high speeds. Looks like I ought to find a run-out dial to check them.
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Old 21 May 2019, 11:51 PM
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I had the same problem when braking at higher speeds. It was warped EBC discs.
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Old 22 May 2019, 09:46 AM
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warped discs or wishbone bushes.
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Old 22 May 2019, 09:47 AM
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Could just be pad deposits , everyone jumps the gun and says warped discs
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Old 22 May 2019, 09:49 AM
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very true
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Old 25 May 2019, 12:54 AM
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How do I check for pad deposits?
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Old 25 May 2019, 10:12 AM
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often black 'smear' marks on the disc, etc.....
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Old 25 May 2019, 12:41 PM
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Try riding the brakes at about 30mph for a little while, sorts my neighbors' L200 out when it feels like that
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Old 31 May 2019, 12:00 AM
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Iv found with cheaper pads after overheating them one I got deposits left and judder, cleaned disks and it was om for a while then came back, had to change pads and give discs a good clean to cure it.
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Old 31 May 2019, 11:35 AM
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Originally Posted by davemar View Post
That was my assumption, but wondered whether warped discs would shudder at all speeds, or just at high speeds. Looks like I ought to find a run-out dial to check them.
You will start to notice judder at high speeds when you apply the brakes, and it might get to a point where you start to think the whole front end will fall apart if you have to pile on the brakes hard.
If they are badly warped , you can do a quick check to "feel for this", get the wheel off and have someone turn the by now "cold" disc while you brace your hand on the calliper and place your braced thumb or forefinger it on face of the disc,
but if they are only mildly out of true, then yes a dial gauge is needed. However if you do find them so just replacing them may not be a long term fix, you really need to establish Root cause as why they have warped.

A possible issue is that your disks have warped because they were of poor steel quality, and unfortunately there are many of these are bad material "discounted" on the aftermarket.
It pays to use good quality named brands or original OEM supplier, however you may still get a repeated warp issue, one of the problems with the WRX calliper is that they do tend to suffer piston sticking,
They just get gummed up with brake dust and while this is also a very corrosive material in a damp environment , aggravating this your brake fluid (which is hydroscopic) promotes corrosion pitting of the pistons,
( which highlights the need to replace fluid frequently) While this is going on , then when during braking you apply more pressure to one side of the disc than the other then you physically distort the heated disc to one side.
If under braking, they should become a dull red hot in this exercise then as they cool they can very well lose shape memory and they develop a warp, this happens far more frequently on disc's which were manufactured without a de-stress
process controlled heat to cool characteristic or that have a coarse steel metrological phase structure. (proving you can't get good quality steel for very little money).

Result is you can very quickly warp the new ones you just fitted again. Its happened to me after a fast run while holding the car on a hill at a T junction with the footbrake. (So use the handbrake that's what it for).
So before mounting new discs you should at least dismount the callipers and clean the pistons in brake fluid or get a rebuild done or rebuild kit installed. ( Ian above can help you with parts for that).

And a word of caution , the WRX brakes are not man enough for spirited driving, and if you have like most of us do , pushed up the power output from 218bhp to XXXbhp then you will find that they are often glowing red hot.
You might like to think about and longer term plans for the car before renovating and recycling your WRX 05 callipers swap to SH Sti Brembo's or a big brake kit.
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Old 31 May 2019, 10:22 PM
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Thanks for the detailed explanation. I've had the car about 18 months, and haven't fiddled with the brakes since buying it. The symptoms have only become noticeable in the last couple of weeks or so.

This afternoon I decided to remove the discs and pads to inspect them. I haven't got a dial gauge so just placed a metal ruler edge-on against the surface to see if there were any visible gaps, and they both looked OK. I know a dial gauge would give a better idea of warping though. Both discs and pads have got plenty of life left in them, and seem to be wearing evenly. As I had spare pins and clips for the pads I decided to replace those as they looked pretty tired, and cleaned everything up. The old pins were very tough to get out, and ended up having to grind one of them in half to help bash it out.

I haven't had a chance to drive the car as I finished doing this quite late, and wine was more important

Hopefully I'll give it a drive tomorrow to see if anything changes.
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Old 01 June 2019, 02:46 PM
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The warped discs myth... https://alconkits.com/technical-info...ed-brake-discs - worth a read.

On my Legacy I found it only occurred when they were pushed hard and getting hot - had the discs skimmed, changed discs, changed pads changed calipers... Turned out to be a sticky rear caliper on its sliders!!!

DOH! - anyway worth a look to rule it out... - hopefully someone can learn from my mistake

Here's a bit at Castle Combe - letting my son have his first drive - unfortunately thats the first I found out about the brakes misbehaving


Unfortunately the 'start at' feature didn't seem to work - so I suggest start at 5 mins 55 secs...

Last edited by Mick; 01 June 2019 at 02:52 PM.
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Old 04 June 2019, 11:58 PM
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John 37
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Had brake judder on my other car. It showed up on MOT brake test machine as a fluctuating reading on the problem wheel.

Last edited by John 37; 06 June 2019 at 03:17 PM.
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Old 09 June 2019, 10:04 PM
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I finally got round to measuring the run-out on the front discs today. The front right disc has about 0.04mm of run-out, and the front left has about 0.14mm. I'm not sure how much is considered acceptable, but this doesn't seem too bad?
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Old 09 June 2019, 10:06 PM
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Actually just dug out some figures and it seems 0.070mm is the maximum run-out for the front discs, so the front left could be causing the shudder.
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Old 13 June 2019, 08:02 PM
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Some garages are able to reface brake discs while they're on the car.
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Old 14 June 2019, 04:27 PM
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Originally Posted by Mick View Post

Here's a bit at Castle Combe - letting my son have his first drive - unfortunately thats the first I found out about the brakes misbehaving

.
The video with sound really does describe the experience. on a motorway at very high speeds its downright dangerous.
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Old 19 June 2019, 10:43 PM
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I gave the surface of the front left disc a bit of a rub with some 2500 grade paper to remove any surface muck. The problem has seemed to have reduced a lot now on my last high speed drive, so hopefully that's eased the problem off now. Hardly any noticable judder at all now, or a least nothing that could otherwise be just grotty road surfaces.
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Old 20 June 2019, 12:16 PM
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Originally Posted by davemar View Post
I gave the surface of the front left disc a bit of a rub with some 2500 grade paper to remove any surface muck. The problem has seemed to have reduced a lot now on my last high speed drive, so hopefully that's eased the problem off now. Hardly any noticable judder at all now, or a least nothing that could otherwise be just grotty road surfaces.
What pads are you running in it ?
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Old 20 June 2019, 10:29 PM
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I'm not sure, as they are still the same ones from when I bought the car early last year. They still have plenty of life left on them too.
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Old 30 June 2019, 09:50 PM
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hi members, i have problem and doing my head in bought some alcons prodrive with discs and pads , had installed and ran for a while then got brake judder so ord some new discs to be fitted 2pc not cheap then ran for a while same judder at braking at speed so had a skim of discs and new pads ebc blue same again ran a while and now judder again so dont know what the problem could be as now same again could be installed and hubs not cleaned or callipers or anything else , before this was running brembo on my wr1 no issue any help would be appreciated will it need a strip down and anybody manchester to look at them
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Old 09 July 2019, 08:14 AM
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To add to obey1's question, if the calipers are a problem, is there an easy way to test each of the pistons in a 4-pot caliper?
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Old 09 July 2019, 07:41 PM
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I recently had a warped hub - fitting new discs didn't help and they weren't warped obviously.
Wheel bearing had gone - a lot
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Old 17 July 2019, 07:20 PM
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Originally Posted by davemar View Post
To add to obey1's question, if the calipers are a problem, is there an easy way to test each of the pistons in a 4-pot caliper?
Take caliper off - apply A LITTLE brake pedal and see which don't move - or just try pushing them back in and see how much pressure they take to move...
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