Stone caught in brake/wheel.

[Carolyn]

So Bahnstormer has a scraping noise coming from one corner after getting bogged down in a gravel driveway.

My suggestion is to figure out which corner has the problem, take a wheel off and have a poke around.  It's probably stuck in the carrier or between the back-plate and the disc. 

Once you've found it it will probably be persuaded out with a screwdriver. Doubt you'll need to loosed a caliper or use a wind-back tool.

Edit:  Once a wheel is off, the disc is loose and floppy.  I wouldn't be surprised if the stone just falls out.

[Mikeymead]

Agree with all of that, jack the car up, work out which wheel is making the noise and take that wheel off so you can see if you can find the stone. May well be able to poke it out.

[Ardent]

Been there on another car. God awful sound. With imminent implosion mere moments away.
Cause. Tiny piece of shale between disc and back plate.

[stewart@boro]

Same happened to me on the mountain pass over to Applecross. Reversing the car with a bit of speed, then braking hard dislodged the offending bit of granite.
It had been in the disc for the whole descent so the disc was quite scored.

[Topdownman]

Using your brakes coming down Applecross? What a wuss!

[Call the midlife!]

Using your brakes coming down Applecross? What a wuss!

Shots fired![emoji23]


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[delhusband]

Using your brakes coming down Applecross? What a wuss!

Shots fired!


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[Call the midlife!]

On a related topic, I pulled myself up from laying beside the car earlier by putting my hand on the n/s front wheel.
Said wheel which was a few inches clear of the ground obviously rotated, nipping my finger between rim and caliper.
That certainly made some awful noises..


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[Ardent]

 

[Treboeth]

On a related topic, I pulled myself up from laying beside the car earlier by putting my hand on the n/s front wheel.
Said wheel which was a few inches clear of the ground obviously rotated, nipping my finger between rim and caliper.
That certainly made some awful noises..


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Did you say "flip" ?

[Call the midlife!]

On a related topic, I pulled myself up from laying beside the car earlier by putting my hand on the n/s front wheel.
Said wheel which was a few inches clear of the ground obviously rotated, nipping my finger between rim and caliper.
That certainly made some awful noises..


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Did you say "flip" ?

Definitely. In a broad, Yorkshire accent.


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[stewart@boro]

Using your brakes coming down Applecross? What a wuss!

Once I realised there was a stone in there, I didn't

[moredun]

Using your brakes coming down Applecross? What a wuss!

Once I realised there was a stone in there, I didn't

I only ever used my brakes once on Bealach na Ba,

[BahnStormer]

So Bahnstormer has a scraping noise coming from one corner after getting bogged down in a gravel driveway.

My suggestion is to figure out which corner has the problem, take a wheel off and have a poke around.  It's probably stuck in the carrier or between the back-plate and the disc. 

Once you've found it it will probably be persuaded out with a screwdriver. Doubt you'll need to loosed a caliper or use a wind-back tool.

Edit:  Once a wheel is off, the disc is loose and floppy.  I wouldn't be surprised if the stone just falls out.

Okay the plot thickens.... I DON'T think this is related to brakes and although I'm sure the driveway episode is the starting point, I think we need to look at that as a tim

To clarify: I would also describe the sound as an intermittent vibration more than "scraping" - I thought there was a bit of a grinding element to it at first, but it's not quite as abrasive sounding as that.

To be sure, I followed the advice from @Carolyn : I took both the back wheels off - I've fished some stones out from the undertray... but nothing around either brake (caliper, back plate, etc). I'm able to freely rotate the brakes (when in neutral, with the hand brake off), there's no sound other than pad disk on pad.

I think this is engine/exhaust related: I've done a bit more driving now and I can create this with 100% accuracy - it only happens when engine revs are dropping. It starts around 2300-2200rpm and dies off by 2000-1900rpm. It's most noticeable in lower gears (as the car is decelerating harder), but it can be recreated in ANY gear and even at idle.

[Ardent]

Heat shield rattle?
The one that sits underneath.
I believe the sheild itself can be secure, but something detaches inside.
Not sure if it usually rev specific though.

[wotugonado]

+1^
There's a weld on the covers that you cant easily  see, but it's there. I ripped mine off in the end after keep fixing it and heat wrapped it instead.

[Tomo70]

Heat shield rattle?
The one that sits underneath.
I believe the sheild itself can be secure, but something detaches inside.
Not sure if it usually rev specific though.

Completely agree, you could also have stones between the exhaust and the shield. I placed stainless steel wading in mine to prevent the rattle.

[BahnStormer]

Thanks guys - that gives me something to look at... seems like a decent level of consensus

Not sure if it usually rev specific though.

It could just be a certain level of resonance in the exhaust at that range of revs that causes whatever is in there to rattle - no idea if that will be broken heatshield or stones in there, but if I hold the revs in that range, then it does sound like a rattle around the exhaust area - but if the revs are dropping fast (e.g. shifting down and using engine-breaking as you approach a junction, then it moves through that range of revs so quickly, it sounds like a grinding noise.

@Carolyn sorry about the vague description at first - my initial description was based on very limited driving of it and then I wanted to check the brakes were clear before I drove it too much more!

[Carolyn]

@Carolyn sorry about the vague description at first - my initial description was based on very limited driving of it and then I wanted to check the brakes were clear before I drove it too much more!
[/quote]

Apologise not!  At least you've had a good look at your brakes eh?

[BahnStormer]

At least you've had a good look at your brakes eh?

yep - had a good look... and once I was confident there wasn't going to be an impromptu one wheel rear lockup, I was able to listen and observe when it was happening... and the exact nature of the sound.... it is definitely at that specific rev-range, it just changes in nature if you're going through that range gently or if you've shifted down and you're braking hard... hence why sometimes it felt like something was grinding briefly and sometimes it was more gradual...

Would be nice to get this sorted before the braces go on!

[BahnStormer]

SOLVED IT!

To be honest I'm not certain what ti was, but I found two issues when we were fitting the braces last weekend:

1) unlikely, but there was a loose piece of plastic trim (front part of the "nappy" - mine doesn't have the rear part).... which I cable-tied down.

2) almost certainly the culprit: the exhaust - the RHS was ~6mm higher than the right. Probably from when I pulled forward on the driveway... Almost unnoticable height difference, but because of the long vertical part of the L shape on the TTE exhaust, the pipe was touching the rear sway bar - cracked the bolts, straightened it out and tightened it up again.

All perfect now and doesn't appear any damage done

edit: also a slight mystery as to why it was so specifically between 2300 and 1800rpm on the way down only, but clearly the exhaust just hits a certain resonance at that engine speed that would force it to separate from the sway bar and rattle.