Bosch Discs OK?

[trickywoo]

Just wondered if anyone has any thoughts on Bosch brake discs? I got a pair before winter and they haven't rusted at all but have developed a vibration (no abuse by me, sitting on the pedal etc) after 3k miles.

A good BMW specialist is saying I need BMW branded discs to fix the issue despite the runout on the Bosch ones being in tolerance and all suspension bushes OK.

I suspect I may not have bedded the pads properly but its really hard finding somewhere you can do 10 consecutive stops from 60mph to 10mph.

[trickywoo]

Yes just cast iron, not drilled or groved.

I know you can't tell just by looking but the casting on the Bosch discs looked good. If I had the cheapest Chinese stuff maybe but I really can't see why just because the Bosch aren't OEM that has caused my issue. The overall difference in price is £300 v £600.

[trickywoo]

Thanks guys. I'll provide an update for anyone else with the similar issues when I've had a go.

[trickywoo]

Martin350 said:

Ferodo DS2500 pads, by any chance?

No. Matched Bosch pads.

Its pretty frustrating as for 3k miles they were great.

I'll give scrubbing them a go but think I'll end up needing a skim, which hopefully I'll get done via one of the on car machines so if I do have any hub issues it'll fix that too.

[trickywoo]

Just thought I'd do a quick update for anyone thats interested.

I had the car into a garage with a pro-cut lathe. Having run the skimming they took the car out for a road test and the issue was still there.

Skimmed again and it still has a shimmy / shiver through the steering wheel when you first get on the brakes at 50mph +. Its much better than it was but obviously frustrating as they are a professional outfit and took their time over the job. The runout is fine and its reasonable to assume any disc thickness variation has been resolved. It felt better after I found a piece of road to bed the pads in and hopefully will improve.

I've had a clean bill of health on the front suspension from a couple of garages now and the tyres, wheels and tracking are OK. Nothing happened that I recall leading to the vibration (pothole, curb, hard braking etc). If its still the same after a few more miles I'm looking at new discs again.

Am I right in thinking it can't be a hub issue if the runout is OK? I don't know why the hub would be an issue but its a confusing situation now. Also can I rule out a wheel issue? There is no obvious damage and no vibration unless braking in certain circumstances.

[trickywoo]

battered said:

If the runout is ok then there is nothing with the hub. Check also that it is concentric. It will be, but check. It could be a warped wheel, unlikely to give this symptom but worth checking. Also wheel balance, again unlikely but it may contribute when decelerating. You will of course detect this undernnormal deceleration without touching the brake. You can also get odd effects from worn CV joints in FWD cars, though more usually it's vibration under acceleration, not braking. It's odd that the skim has not resolved it.

Thanks. Helpful stuff.

The garage doing the skimming seemed equally disappointed.

Just as an aside the pro-cut lathe is a really nice bit of kit. I have a bit of a machinery fetish and apart from being electric and not petrol that ticked a lot of boxes.