Weird Brake Pad Wear

[AmirGSXR]

I was changing the worn brake pads of wife's Mk3 Suzuki Swift, and noticed that the inner pad of the N/S front had this brake disk shaped groove etched on the pad (see pictures). The car does make a humming sound from that area when driving, particularly when cornering right (for example on a roundabout). It passed it's MOT recently and there are no other issues. Apart from the groove, pad wear on both sides are equal and consistent, as is the tyre wear. Following the change to new pads, the humming noise is still there, so I am presuming there is still an issue.

What could be causing this to happen?

[steveo3002]

its the rusted lip thats worn into it like that

possibly had new pads onto old discs at one point

[AmirGSXR]

steveo3002 said:

its the rusted lip thats worn into it like that

possibly had new pads onto old discs at one point

That's an interesting point. The car has done 66k miles, so it's plausible it had new pads on original discs at some point, though I could see nothing of that in its history of receipts. However, I am wondering now whether I should just replace the discs too. Picture below shows how current discs look and they seem to have that rusty lip!

[thebraketester]

Does the car stand for long periods? I would change those discs personally.

[AmirGSXR]

No, it actually used for a 40 mile commute every day of the week for the last 2 years or so.

The MOT guy only gave advisory for low pads, but nothing was noted about the discs, but having said that they don't have a lip that you can feel when running your finger along it and besides the rust on the top edge of the disc, look fine. In fact, I have had worse discs on other cars (i.e. with a pronounced lip), but never had this type of problem with pads.

[GreenV8S]

The groove is most likely caused by the rusted disc. It would have beenreasonable to replace the discs together with the pads but those don't look bad enough to cause problems so I wouldn't take it apart again just for that. Did you clean and lubricate the calipers and flush the fluid as part of the brake service?

The murmuring noise is probably unrelated and may be a sign of a wheel bearing on the way out.

[AmirGSXR]

GreenV8S said:

The groove is most likely caused by the rusted disc. It would have beenreasonable to replace the discs together with the pads but those don't look bad enough to cause problems so I wouldn't take it apart again just for that. Did you clean and lubricate the calipers and flush the fluid as part of the brake service?

The murmuring noise is probably unrelated and may be a sign of a wheel bearing on the way out.

Yes, I cleaned and lubed the caliper bolts (lubed with Ceratec), and the brake fluid will be changed later this week, although it's level and colour are still ok.

I have considered a wheel bearing too, but the noise doesn't happen if I spin the wheel and there is no movement of the wheel when rocking it side to side. Having said that, I suspect the issue (noise) will only occur when the wheel is at speeds higher than my hand spinning!

Thanks for all the help so far...

[brman]

There looks to be a crack in that pad and the disc is showing an odd wear pattern so I am wondering if it has been overheated at some point. I'd say it is worth checking the calipers are not sticking.
Regardless, I agree, I would definitely be replacing the discs as well as the pads.

[Demelitia]

AmirGSXR said:

GreenV8S said:

The groove is most likely caused by the rusted disc. It would have beenreasonable to replace the discs together with the pads but those don't look bad enough to cause problems so I wouldn't take it apart again just for that. Did you clean and lubricate the calipers and flush the fluid as part of the brake service?

The murmuring noise is probably unrelated and may be a sign of a wheel bearing on the way out.

Yes, I cleaned and lubed the caliper bolts (lubed with Ceratec), and the brake fluid will be changed later this week, although it's level and colour are still ok.

I have considered a wheel bearing too, but the noise doesn't happen if I spin the wheel and there is no movement of the wheel when rocking it side to side. Having said that, I suspect the issue (noise) will only occur when the wheel is at speeds higher than my hand spinning!

Thanks for all the help so far...

A wheel bearing won’t always show up when the wheel is unweighted. Try spinning it whilst holding the spring on that corner, it’ll sometimes amplify the roughness enough for you to detect it.
You could also try using a long screwdriver, tip against the back of the bearing area, handle in to your ear like a stethoscope. Compare sides for reference.

[GreenV8S]

AmirGSXR said:

I have considered a wheel bearing too, but the noise doesn't happen if I spin the wheel and there is no movement of the wheel when rocking it side to side.

In the early stages the symptoms may only show up when the wheel is loaded in the right direction to run on the specific part of the race which is damaged. It'll gradually spread until you're in no doubt.

[E-bmw]

GreenV8S said:

AmirGSXR said:

I have considered a wheel bearing too, but the noise doesn't happen if I spin the wheel and there is no movement of the wheel when rocking it side to side.

In the early stages the symptoms may only show up when the wheel is loaded in the right direction to run on the specific part of the race which is damaged. It'll gradually spread until you're in no doubt.

^^^^ Wot 'e said.

Classic early signs of wheel bearing wear.

If you took it off & had it in your hand rotating it and did the same with a new one, you will feel/hear the difference immediately.

Going back to the brake disc/pad issue it will certainly be new pads put on an old disc.

Doesn't mean you need to run for the hills & immediately change everything, but my advice would be to budget for a full set of discs/pads for that end of the car within a year to make sure all is well going forward. Maybe in time for next year's MOT might be a good plan.

[VanDiesel99]

Discs & Pads are so cheap and so important that if you're concerned about it, there's no point pratting about, just change em. I tend to use Pagid Discs with a top quality pad such as Bosch.

[Chris32345]

They are past it looking with the rust and marks at how far the piston is extended you have a fair bit of wear into the disc as well so probably unlikely to last another set of pads before they are down to minimum thickness