When to change brake pads/shoes?

John_D

Club Member
Radio Code Guru
Going by the wear pattern on the pads your discs are just about worn out. When you do change them (I never let pads go below about 4mm friction material thickness) this time you really need to fit new discs at the same time as well.
 
OP
OP
H
Going by the wear pattern on the pads your discs are just about worn out. When you do change them (I never let pads go below about 4mm friction material thickness) this time you really need to fit new discs at the same time as well.
Thanks John_D

Here is the current state of my disks


I have noticed something else that needs to be sorted urgently. Here is pictures


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John_D

Club Member
Radio Code Guru
The disks are not scored but have a wear ridge of about 3mm, both at the edge and at the hub centre which effectively makes the disc about 6mm thinner. If you fitted new pads to those discs, initially they would only touch on the high spots on the edge and the centre.
I just changed the discs and pads on my K12 , new quality Mintex parts cost £40 (ebay supplier) and transformed the braking. As for the caliper dust seal, new seals might solve the problem (if you can get them) but be sure to thoroughly clean the exposed piston, BEFORE pushing it back into the caliper, with brake/clutch cleaner. Failing to do this will probably cause dirt/grit to be carried into the caliper bore and consequently damage the caliper seal.
 
When they are like this?

Seriously I'd get yours replaced, disc too :) it's the difference between stopping and crashing!!


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pollyp

Club Member
if the pad is 2-3mm thick and or the material has broken away, it needs replacing.

measure the discs thickness.
if the thinnest section is 17-18mm, it still has enough meat left. minimum is 16mm.
if the disc face has severe rippling scoring and the edge of the pads have left a radius lip, either have the disc remachined flat or replace the discs before fitting the new pads.

damn that piston boot has been obliterated. imo the caliper will require an overhaul. take out, clean & inspect the piston closely. if the chrome plated sealing surface is degraded in any way (chrome chipped off or rusted), replace the piston & seal.
while replacing the piston boot, you may as well get a full caliper service kit for £8-10 to replace all the rubber components/seals tbh.
clean & regrease the sliding guide pins only with non-petroleum lube like Red rubber grease so the rubber doesn't swell & seize.
if it's too much work, could get a new or used caliper.
 
OP
OP
H
if the pad is 2-3mm thick and or the material has broken away, it needs replacing.

measure the discs thickness.
if the thinnest section is 17-18mm, it still has enough meat left. minimum is 16mm.
if the disc face has severe rippling scoring and the edge of the pads have left a radius lip, either have the disc remachined flat or replace the discs before fitting the new pads.

damn that piston boot has been obliterated. imo the caliper will require an overhaul. take out, clean & inspect the piston closely. if the chrome plated sealing surface is degraded in any way (chrome chipped off or rusted), replace the piston & seal.
while replacing the piston boot, you may as well get a full caliper service kit for £8-10 to replace all the rubber components/seals tbh.
clean & regrease the sliding guide pins only with non-petroleum lube like Red rubber grease so the rubber doesn't swell & seize.
if it's too much work, could get a new or used caliper.
Thanks pollyp,

I would probably service the calliper and would count on your help and advice.

Where can I get the kit from? Yesterday did a quick search but could find anything!

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Or swap to bigger brakes like the sunny / almera ones. But if you do look up if they fit with your current rims first.
 
I had my front discs and pads & rear shoes, some hoses & brake fuild changed earlier in the year.
The stopping is so much more crisper then before. You touch the pedal and they straight in, wherea's before I had put pedal down that inch and half etc.
I think it came to about £250. Best money spent IMHO!
 
I think brake fluid changes are majorly overlooked by car owners. On my bike I change it every year and the difference is noticeable, but then there's no servo on a bike so it's direct feel.


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John_D

Club Member
Radio Code Guru
I think brake fluid changes are majorly overlooked by car owners. On my bike I change it every year and the difference is noticeable, but then there's no servo on a bike so it's direct feel.


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All types of brake fluid up to and including DOT4 are hygroscopic (DOT 5 is silicon based and does not suffer with this), that is to say they absorb water from the air. This alters the 'feel' of the pedal, but more importantly reduces the boiling point of the fluid, such that under extreme braking conditions the fluid can boil and you lose the brakes due to the fluid in the caliper turning to vapour!
Having just done a clutch change, and the fact that the brakes and clutch uses the same fluid reservoir I've pretty much just changed mine though might well bleed some more through the brake system, from each wheel, in the spring, to make sure.
 
Just to add that dot 5 can't be mixed with dot 4 but there is dot 5.1 which isn't silicon based and can be used with brake systems that have dot 4, and has a higher boiling point than dot 4. In normal driving there's no real advantage but in competition or track day using 5.1 could have a benefit :)


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