Cars - changing disc brakes [wear vs lifespan]

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davis
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Cars - changing disc brakes [wear vs lifespan]

Postby davis » Thu Nov 08, 2012 13:13 pm

Yes, yes, it's about cars. Yes, this is a bike forum.

I've agreed to change a mate's discs and pads on his 2001 Ford Focus as he said they were making an awful noise, not really working and he could feel a definite lip on the disc. Because he was pretty definite I ordered the discs and pads (Wahey - 65 quid for Brembos from NextDayBrakes.com!) and drove over to his (he lives about 3 hours from me) Now, I've just dragged a finger along the disc, and there is a noticeable lip, but I'd say it's only about 0.5mm, and there isn't too much gouging on the surface.

I'd therefore say his discs could stand to be left on as they'll survive another set of pads... When I pop the calipers off I'll take a good look at both the pads and the discs, but is there a rough guideline for how much life you'd expect from pads and from discs*? I know it might be possible to re-face the discs, but we've already got the discs, so how do I know whether they need replacing? We don't have a friendly local garage (in Totterdown, Bristol right now).

*: I know that depends entirely on how you drive it (mostly slow city stop/start driving), but I'm only looking for a rough guide of say "<4mm of brake pads probably needs replacing, but might last between 2000 and 5000 miles" or something like that.
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Paul E
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Re: Cars - changing disc brakes [wear vs lifespan]

Postby Paul E » Thu Nov 08, 2012 13:21 pm

I would just change both at the same time, I always did that on mine and I don't know what the scored discs would do to new pads.
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andyrr
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Re: Cars - changing disc brakes [wear vs lifespan]

Postby andyrr » Thu Nov 08, 2012 13:37 pm

If their performance isn't up to scratch then it might be something oither than worn disks - modern pads can be fairly noisy anyway but it might be worth having a drive and seeing if one side in particular is getting too hot indicating a sticking caliper.
If so then that can mean the caliper needs rebuilt which is a pain - nice and simple to do disks/pads but might not fix the issue, lettng pads wear down also can mean that the piston is then coming further out of the caliper bore and that can lead to it sticking.
Could also be the brake fluid neeing changed / bled.

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SimonAH
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Re: Cars - changing disc brakes [wear vs lifespan]

Postby SimonAH » Thu Nov 08, 2012 13:41 pm

The Haynes book of jokes will give a specific minimum disc thickness for you. Libraries usually have them for common vehicles.
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meanredspider
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Re: Cars - changing disc brakes [wear vs lifespan]

Postby meanredspider » Thu Nov 08, 2012 13:43 pm

Discs normally have a wear limit (often marked on the disc edge itself) which indicates the minimum thickness of the disc. Wear rate depends a lot on the driving style and the compound of pad so it's impossible to say how frequently they should be changed.
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Veronese68
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Re: Cars - changing disc brakes [wear vs lifespan]

Postby Veronese68 » Thu Nov 08, 2012 13:45 pm

meanredspider wrote:Discs normally have a wear limit (often marked on the disc edge itself) which indicates the minimum thickness of the disc. Wear rate depends a lot on the driving style and the compound of pad so it's impossible to say how frequently they should be changed.

This. If well within tolerance I'd just change the pads. This is why I still have a pair of Passat discs in my garage.

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meanredspider
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Re: Cars - changing disc brakes [wear vs lifespan]

Postby meanredspider » Thu Nov 08, 2012 13:46 pm

SimonAH wrote:The Haynes book of jokes will give a specific minimum disc thickness for you. Libraries usually have them for common vehicles.


Library is a quaint idea

http://www.justpartsbiz.co.uk/acatalog/ ... Drums.html

Dunno if that's the exact car but I'm sure you'll find it
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CiB
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Re: Cars - changing disc brakes [wear vs lifespan]

Postby CiB » Thu Nov 08, 2012 13:50 pm

I'd fit the discs anyway. It's an 11-y-o Focus so this'll be the last time it needs doing; all you're doing is creating another pair of 3 hour journeys to fit them next year sometime. Nothing wrong with having new brakes when you maybe didn't totally need new brakes

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davis
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Re: Cars - changing disc brakes [wear vs lifespan]

Postby davis » Thu Nov 08, 2012 13:55 pm

CiB wrote:I'd fit the discs anyway. It's an 11-y-o Focus so this'll be the last time it needs doing; all you're doing is creating another pair of 3 hour journeys to fit them next year sometime. Nothing wrong with having new brakes when you maybe didn't totally need new brakes


Now that you put it like that, it makes perfect sense. Thanks all. I'll just stick the pads and discs on there. It'd cost more in fuel to do the journey than the discs cost to buy (Course I came to see him 'cos he's my mate, and work have sent me to a job about 10 miles away, but that's not the point). I'll take it for a quick razz first and see how the brakes are behaving anyway.
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gtvlusso
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Re: Cars - changing disc brakes [wear vs lifespan]

Postby gtvlusso » Thu Nov 08, 2012 14:51 pm

try Golden Hill Garage on kellaway Avenue; 01179 425468, very friendly and will offer good advice.

Personally, I would just change the lot as I have no way of facing the discs. Maybe get the old set re-faced later on and store them for a swap out when the new set get worn out.

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Kieran_Burns
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Re: Cars - changing disc brakes [wear vs lifespan]

Postby Kieran_Burns » Thu Nov 08, 2012 15:28 pm

and ger Gawds sake remind your mate that there will be minimal braking available until the pads / discs have bedded in.

We've all made the mistake in the past... it'd be nice to avoid one more.

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davis
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Re: Cars - changing disc brakes [wear vs lifespan]

Postby davis » Thu Nov 08, 2012 15:31 pm

Kieran_Burns wrote:and ger Gawds sake remind your mate that there will be minimal braking available until the pads / discs have bedded in.


Don't worry, I will! It's not usually that bad IME, but I'll make him stick a post-it note to the dash or something.
Sometimes parts break. Sometimes you crash. Sometimes it’s your fault.


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