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Old 17th December 2018, 21:46   #1
BigAde
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Default Knocking/thudding noise - frequency matches road speed

Could do with some advice on this one...

Yesterday I switched my 18" gridspokes with summer tyres over for the 16" Unions with winter tyres.... all routine stuff, everything I've done countless times before and all was well this morning driving to work.

However on the 25 mile drive home I soon noticed a knocking/thudding sound (definitely not metallic) coming from the nearside somewhere. The frequency of the noise matches the road speed and it sounds to me like it's one knock for every complete rotation of the wheel. I stopped the car twice on the way home and had a good look around, checked tyre pressures, looked under the car and in the wheel arches for obvious signs of loose trim or a stray twig/branch or something, but there was nothing.

The noise appears to stop on doing one of two things:
  1. Driving with the handbrake applied. The knocking resumes immediately upon release of the handbrake.
  2. Stopping the car and engaging reverse for a few feet. Thereafter driving is normal until such time as the knocking starts again (within a few miles it seems).
My first thought was that I'd done something while changing the wheels over so I whipped both rear wheels off tonight and checked and double-checked for anything wrong. Couldn't see anything. Took the car for a 5 mile test drive, but the knocking started within a mile or two.

Any thoughts?
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Old 17th December 2018, 21:59   #2
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Rear brake backplates corroded? As the handbrake shoe retaining pins broke free, mine did exactly that.
The disk/drum may be a challenge to remove.
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Old 17th December 2018, 22:16   #3
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Completely agree with Tony, get it sorted before the handbrake shoes get caught up on the back of the wheel bearing.........this is very unpleasant and will be a pain to sort out
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Old 17th December 2018, 22:25   #4
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Really obvious suggestion... But have you checked your wheel nuts are tight - on all wheels.
I had somebody bring a car to me with a strange knocking noise - Turned out the front wheel was loose
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Old 17th December 2018, 22:34   #5
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Quote:
Originally Posted by cb750chris View Post
Really obvious suggestion... But have you checked your wheel nuts are tight - on all wheels.
I had somebody bring a car to me with a strange knocking noise - Turned out the front wheel was loose
That would have been my first suggestion too Chris, had it not been for the fact applying the handbrake stops the noise

Still it's a nice easy check before dismantling the brake drum.

Brian
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Old 17th December 2018, 22:34   #6
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Quote:
Originally Posted by cb750chris View Post
Really obvious suggestion... But have you checked your wheel nuts are tight - on all wheels.
I had somebody bring a car to me with a strange knocking noise - Turned out the front wheel was loose
Yep - definitely on tight.. checked and double-checked.
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Old 17th December 2018, 22:40   #7
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Quote:
Originally Posted by marinabrian View Post
Completely agree with Tony, get it sorted before the handbrake shoes get caught up on the back of the wheel bearing.........this is very unpleasant and will be a pain to sort out
Ok, you've scared me now.

Should I not consider driving it until it's fixed then? And what are we talking about -just new back plates?

Here's a picture I took tonight with the rear wheels off.. not seeing anything obvious, but then I'm not sure what I should be looking for. The back plates are original I think but seem intact and not flaking away.
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Last edited by BigAde; 17th December 2018 at 22:44..
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Old 17th December 2018, 22:57   #8
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You need to disconnect the rear calliper. Use a good quality 13mm hex socket, not a multi sided one as the calliper retaining studs rust away. I’ve had to chisel them off before. Replace with new studs is a must.
With the calliper removed and handbrake adjuster slackened off inside the car, remove the torn screw securing the rear disc / drum. The rear shoe which will have come adrift will be catching on the drum so you need to wiggle it quite a bit.
With the drum off you can fabricate a stud with a nylon nut and washer to secure the brake shoe in place but remember it has to have some free play, hence the nylon nut as you don’t want it up too tight.
Onece you have secured both shoes re assemble the drum, and re adjust handbrake using the correct procedure.
Good luck !
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Old 17th December 2018, 23:15   #9
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Quote:
Originally Posted by BigAde View Post
Ok, you've scared me now.

Should I not consider driving it until it's fixed then? And what are we talking about -just new back plates?

Quote:
Here's a picture I took tonight with the rear wheels off.. not seeing anything obvious, but then I'm not sure what I should be looking for. The back plates are original I think but seem intact and not flaking away.
Hi Adrian
You will need to remove the brake caliper, also the disc drum to check the back plate and the hand brake mechanism, I bet the drum is full of dust also they need to be taken of at least once a year and cleaned out in my opinion.

Check the pins are not pulling through the back plate.

1

2

3

4

5

6

If the back plate is ok and in good condition clean it wire brush it scrap it etc,
7

8

9

paint it after treating with rust inhibitor
10

Finally add a new disc and brakes pads shoes if you have to, not forgetting if the back plate as gone then change that first.
11
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Old 17th December 2018, 23:22   #10
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Nice simple guide there Arctic


Glad the OP didn't have loose nuts, as you say Brian unlikely to have been that with the handbrake sorting the issue, but applying the handbrake could have just put pressure on the wheel, so pulling it agianst the studs stopping the noise (the one I had brought to me was a Rav4, which only made the noise in a straight line - the noise disappeared when cornering).
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Replacement keys programmed / supplied / cut

Diesel 135 upgrade available

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Sorry, due to a big change in home circumstances, I am unable to do any large jobs at present, but can still offer evening time diagnostics.
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