when to change brake pads/disc - minimum mm?

Sportacus

My rear pads look like they have 2-3mm left on them, is there any rule as to when they should be replaced? They're the same ones that came with the car new, along with the discs.


On the same subject, is it worth replacing the discs too? They have a pronounced lip on them, and I did make a mistake of just replacing the front pads before, and 6 months later needing to replace the discs (which meant new pads too :mad:).


Also, is kwik-fit's lifetime replacement deal on pad and discs worth it?

wongataa

It depends on the discs and pads in question. They will each have a minimum thickness at which they should be replaced. Have you a maintenance manual that tells you?

forgotmyname

I thought KwikFit only replaced the pads or shoes for free. They do that so they can sell you a set of discs to make up for the loss.

One set of free pads and a set of expensive discs = ££ more than a set of discs and pads from a reliable local garage.

Yes the pads and discs will have a minimium thickness, It varies from car to car so you need your vehicles specs.

At KF minimum is probably 1mm less than the thickness of a new set.

Joe_Horner

The MOT limit for brake pasds (not that they can usually see them) is 1.5mm.

Bear in mind that braking performance won't suffer until the pads have no lining left and you start getting metal to metal contact. The MOT limit is there to try and ensure you don't end up in that situation.

As a very rough guide, if you've had those pads from new, you can work out about how fast you're using them. Pads tend to come with 8mm linings, so you've used about 6mm in the mileage you've done so far. If you work on another 1mm to go then you have (very very roughly) 1/6th of the mileage you've done so far left. So, if you're on 18k miles, you're lookiing at another 3k. If you've done 30k then you should be good for another 10k or so.

A lip at the edge of the disk isn't a problem in itself, what matters is the thickness of the worn part. That can be quite hard to measure with a lip but typical disks will happily carry a lip of 1mm or so each side for another set of pads. Basically, if a disk hasn't warped, or worn to the point that it's likely to break, then it won't affect braking and will pass an MOT.

That also applies to scored and pitted disks - but you'll wear pads faster in that case.

Sportacus

thanks, I think the lip on my rear discs is around 1mm, so I'll leave it for the moment.

JustinR1979

Presume rears are solid discs so can get away with a bit of wear, and wear slower than front anyway.

Hyperxr

I would only change it if it fails the MOT or starts squeeking etc. Brakes on my '98 Corolla lasts 30k-40k. Tyres too last atleast 30k miles. Since ownership (bought in 2001 with 30k mile) and now on 223k I've spent around £3.5k on 1 clutch change, 3 timing belts, 5 sets of tyres, brake dics/pads, oil changes and filters, lamda sensor including other small niggles like bulbs etc since 2001. Annual road tax is £145, insurance is £260 and it returns 45mpg on a run ad 35mpg around town. Preventative maintenance is the key to longativity and saving money. My car still goes perfectly and is good for at least another 100k.

Not bad in my books.

FiremanDave

Hyperxr wrote: »

I would only change it if it fails the MOT or starts squeeking etc. Brakes on my '98 Corolla lasts 30k-40k. Tyres too last atleast 30k miles. Since ownership (bought in 2001 with 30k mile) and now on 223k I've spent around £3.5k on 1 clutch change, 3 timing belts, 5 sets of tyres, brake dics/pads, oil changes and filters, lamda sensor including other small niggles like bulbs etc since 2001. Annual road tax is £145, insurance is £260 and it returns 45mpg on a run ad 35mpg around town. Preventative maintenance is the key to longativity and saving money. My car still goes perfectly and is good for at least another 100k.

Not bad in my books.

Darkmatter we all know the Corolla is your grandads car and probably does 500 miles between mots when he uses it on your school run.

Ebe_Scrooge

To the OP - all the above advice is sound. As a slight aside, on most cars, both pads and discs can be changed very easily and cheaply - it's a DIY job if you've got any experience with cars at all.

If you're not confident with DIY, then find yourself a trusted local independent - brakes are bread and butter stuff to any "real" mechanic ( avoid Kwik-Fit ! ).

Nodding_Donkey

The lip can also seem worse than it really is because of rust building up on the lip itself.

Joe_Horner

Wow! 8 hours and 10 posts into a thread about brakes, and so far no-ones posted that you must do the pads and disks together (all 4 wheels, of course) and should consider changing the fluid, all pipes, ABS ECU, tyres and rims at the same time cos it's safety innit!

What a refreshing change