A6 c7 pulsating brakes & wheel vibration cure

[Steve Q]

Info credited to Harry Joynes: 

Hey everyone. Just thought I’d share my hunt for slightly pulsing brakes at low speed and a vibration in the seat at 50mph plus. After much searching the internet it lead me to a wheel bearing however I was thinking warped rear discs. I changed the fronts that stopped the steering wheel shake when braking   I thought today I’d just take the wheels and docs off to see if there was anything noticeable and there it was. The hubs between the discs were corroded and pushing the whole lot ever so slightly off straight. Cleans all faces up and now it drives like a dream. Just a free thing to do if anyone is experiencing similar issues. Little before and after pic.

[Magnet]

Thanks Steve,

This is really straight from the book of best practice, and should always be done as a matter of course. DIYer have no excuse for not doing this - apart from ignorance, so certainly worth a mention.

Garages not doing it, because it takes a little longer?? 

Anyway, thanks Steve. 
Kind regards,

Gareth. 

[Steve Q]

No probs at all Gareth, just thought it was worth a share 🙂

[DaveOL89]

Great post!

 

 

pretty disappointing that a garage didn’t clean this up whilst changing the disks over, really doesn’t take all that much more time if your already there changing the disks.

 

[nitch]

Hi Steve, did you just change the fronts in the end? I get the judder when lightly braking at 40+ speeds which goes the second I brake harder. Was that similar symptoms to you? Thanks 

[Magnet]

Thanks Oliver,

So has the area Steve refers to been checked and confirmed good? 
If not , you can forget all other possibilities until this has been checked. 
So called ‘warped discs’ diagnosis is an Internet favourite! 
Kind regards,

Gareth. 
 

Dave,

p.s. Many - most? owners go with cheapest quote, with little interest in the quality of parts used, and an extra 20mins labour per side can be a deal breaker. 

 

[nitch]

No not yet but when I have the time, I'll take a look at them. If I'm honest, I'm struggling to see what that corrosion is doing that would cause my symptoms but will give it a go as it's a free fix. Thanks

[cliffcoggin]

55 minutes ago, nitch said:

 If I'm honest, I'm struggling to see what that corrosion is doing that would cause my symptoms

When steel rusts it expands, thereby pushing adjacent parts away from each other. That's why rusty bolts are a swine to remove and brake discs are pushed out of alignment.

[nitch]

I understand that but why would it cause the vibration under light braking? If the corrosion is moving the rotor out slightly, it's still out there when I brake harder and the vibration goes. Any ideas on the reason? Cheers

[Magnet]

OK, apologies for jumping back in on this thread, but I must stress it’s your car Oliver, and you are free to follow advice asked for - or not. 
The advice you have been given has been on the basis of not getting into any more complex possibilities until this potential issue has been eliminated.

Good luck,

Gareth. 

[Caffrey]

Hi All,

Had this problem for a while. 70 mph on the motorway, the guy in front slows down so just apply a bit of pressure to the brake would make the car shake violently but not through the steering column. Hit the brakes hard, no problem but just a feather touch was horrible and the longer the journey the worse the shaking.

Upshot - warped discs on the front - 120K on the originals so no complaints. New discs and pads, problem gone.

 

[Magnet]

Thanks Tim.

Never did hear anymore from our Oliver. 
Kind regards,

Gareth. 

[nitch]

I asked a simple question, got a fairly frosty response. But appreciate some more input, Tim. I'm taking the car to a local specialist to check the discs and if there's a problem to either have them skimmed or replaced.

Cheers

[Caffrey]

18 minutes ago, nitch said:

I asked a simple question, got a fairly frosty response. But appreciate some more input, Tim. I'm taking the car to a local specialist to check the discs and if there's a problem to either have them skimmed or replaced.

Cheers

Sadly skimming is a thing of the past, I asked, just not done anymore.

Just had the bill as well, it had to be done but it's not cheap!!

[nitch]

It's a heavy, powerful car but it's pretty rare that the brakes get much abuse so I'm surprised it's happened. I will also check out the corrosion mentioned above but I can't get my head around why that would cause the symptoms. Anyway, I'll update once I get around to it. Cheers

[Caffrey]

28 minutes ago, nitch said:

It's a heavy, powerful car but it's pretty rare that the brakes get much abuse so I'm surprised it's happened. I will also check out the corrosion mentioned above but I can't get my head around why that would cause the symptoms. Anyway, I'll update once I get around to it. Cheers

I've done 120K in mine and they're the original discs so can't complain really. I asked the mechanic to clean the hubs anyway after what was said here. My guy put the car on a rolling road so he could also feel the shaking.

My discs and pads came to £350 plus VAT for reference.

[spartacus 68]

Warped brake discs are a bit of an anomaly. That’s not to say it can’t happen.

In my experience, it’s sometimes not the brakes at all, but potentially worn wheel bearing, suspension component such as deteriorating suspension bush or a sticky brake piston. Older cars, then you get into top mounts, etc.

You can also get brake pad transfer. The brake discs may have heat spots or dark areas on an otherwise clean brake disc. That’s a sure sign of excessive heat, possibly the brake caliper sticking. Sometimes seized brake sliders, or corrosion on the dust sleeve on the caliper itself.

One way to rule out sticky piston(s), is to run car then coast to a stop. Brake discs may be warm, but defiantly not hot. Check for lip on brake disc, scoring on the brake disc or different disc material widths remaining, easy to spot on ventilated brake discs.