Saab 95 brake vibration.

[Robski]

Hi all.
Need some help.
I have a Saab 95 2007 with Hirsch upgrades,(suspension, brakes etc), and I love it but it's driving me mad. I keep getting vibration through the steering wheel when I brake at motorway speeds.
In the last 7000 miles I've tried 2 sets of front discs and pads from Hirsch (£600per set) being fitted by 2 different Saab garages, new front hubs and bearings, 2 new subframe bushes then a full set front and rear disc and pads (mintex) manly out of desperation, fitted by yet another garage and the symptoms are always the same .... Everything is fine for about a 1000 miles then a vibration starts to creep in when braking at motorway speeds. The steering wheel starts to vibrate anytime I brake doing more tha 60mph.
I've even put new tyres all round and had them balanced at 2 different places.
I've checked the discs for signs of overheating and made sure that there are no dragging callipers.
Each time the car has a change of discs the callipers are checked for leaks and pins are greased.
The disc are 345mm vented weighing 26lb each and I can't see how I'm warping them.
I have always had saabs and this is the first time I've had this problem.
When I brought the car it had just had a new set of discs so I have a feeling that this was a problem long before I had it.
I'm now thinking of changing discs, callipers and front shocks. Any help would be great

[phoenix]

Welcome

As you say, disc warping is unlikely. Brake judder is normally caused by uneven distibution of and matrial on the disc, often due to stopping and resting your foot on the pedal when the discs are hot, or failing to observe proper warm up and cool down procedures after hard driving.

There's a good decription of it here:

http://www.stoptech.com/technical-support/technical-white-papers/-warped-brake-disc-and-other-myths

[Robski]

Hi.
Thanks for the info but after the first time I had the problem I contacted Hirsch and followed their bed in procedures to the letter, I even got access to an airfield to do the bed in process and then when I changed to Mintex I followed their advise.
I make a point of not sitting on the brakes when I stop and even try to stop early so I have a bit of space to roll to avoid hot spots.
I'm wondering if it's something else that's possibly causing a small vibration to be amplified and that's why it only really happens at motorway speeds.

[Audax]

There's many things it could be but it doesn't make sense that this isn't happening until a 1000 miles after fitting the discs and pads.

If it was something other than discs and pads it should be all the time, not when new discs and pads are fitted.

Having had a bit of a think, I'd be looking at a couple of things, first off, has it had a 4 wheel alignment and all of the suspension and drive shafts carefully checked? If so has someone done a live Tech-II check to see what the ESP system thinks the car is doing at 70mph. I'm thinking along the lines of something like the ESP sees a wheel speed mismatch at 70 and applies brakes unevenly or steering angle is out, something like that.

[Robski]

Thanks AUDAX.
I've got to say it's really confusing me too. Doesn't really make sense, yes I've had 4 wheel alignment but I hadn't thought about the driveshaft although surely a bent shaft would give me a vibration even without braking.
However the abs is interesting, hadn't thought of that. Maybe the the warped discs is symptom and not the cause. I think I might try to disconnect the abs and see what happens, could it be something to do with the break fluid or a clogged brake line confusing the abs??
The strange thing is that there is no brake pedal pulsing and no vibration through the car just the steering wheel oscillating during braking but only above 60, perfectly smooth below that speed.
Could it be a dodgy shock because I occasionally I do get a clunk from the near side front on the odd occasion?