Time for new discs?

Ive got a set of M670 SLX discs and always been happy with them but recently they have lost their bite. They squeal a lot but with very little braking power. The lever feel isn’t spongy so i don’t think they need bleeding and i have lightly sanded the disc and pad surface to take off any glaze but still no difference. Am i missing something or is is maybe time for new pads and if so should i be looking to replace the discs at the same time to be sure of no contamination?

Change the pads, and clean the discs with IPA, should get rid of any contamination.

Ok thanks I’ll try that. Any tips as to which pads to go for?

Ok thanks I’ll try that. Any tips as to which pads to go for?

depends on what conditions you ride in and your braking style.

organics are the best for feel and power but are also the softest compound. especially if its really wet/muddy and you are heavy on the breaks they can get worn down on one ride

sintered have a higher metal content so they last a lot longer but the trade off to this is some of the feel and bite of organics. they are especially good if you ride a lot on wet/muddy conditions (so that most UK riders then)

kevlar is a balance between organic and sintered and the most expensive type you can get. they are supposed to last as long as sintered but have the performance and feel of organic pads

it also depends on how much you’re prepared to pay for a set of pads too.

Thanks for that, really helpful. Just looked on superstar website and the difference in cost between each type is a pound so based on kevlars being the best compromise would you recommend getting a couple of sets of those?
I just ride local trails, trail centers and xc stuff so nothing too extreme

I use the superstar kevlars in all mine, they’re great pads. But can be a little noisy in the wet, and there’s some conditions they just don’t last in, sharp gritty mud and teh like (dark peak, I think is what people say?) I’ve never had that problem even in evil fort william grinding paste but it seems to be a real thing

It is the callipers that are knackered. The seals are gone and spraying a very fine most of oil on the discs / pads. Changing the discs / pads won’t fix it, you need new callipers (shimano don’t do spare calliper parts apparently). Better yet, take the opportunity to upgrade to some brakes that don’t do this, Hope for example.

That’s possible, but you can’t diagnose like that based on this info.

Hope do do it, eventually. Had continuous issues with contamination until I changed the seals but they were 8 years old.

i received my kevlar pads last weekend. they’re now on the bike and apart from a quick spin up and down the road in front of my friends house to initially test them, i’ve now had a chance to go for a ride yet. hopefully this weekend i’ll find time to go find a big hill so i can get the pads bedded in.
on first impressions though they seem to feel a bit sharper than the standard pads

[Quote]Northwind – Member
That’s possible, but you can’t diagnose like that based on this info.[/quote]

It is hugely likely. It is what shimano brakes do (shit the bed).

Thanks, i’ll give the kevlar ones a go and see how i get on. I’m assuming that for the M670 slx im needing the S5K pads from superstar?

I’m assuming that for the M670 slx im needing the S5K pads from superstar?

that’s correct. if your current pads are the finned version, just be aware that the kevlar superstar ones aren’t finned. the fins are attached to the pads themselves…shouldn’t be an issue though

It is hugely likely. It is what shimano brakes do (shit the bed).

I’m not sure why you’re taking your bike to bed with you, and I’m pretty sure it’s probably too much beer and curry that’s causing your defecation/sleep issue.

I had a very similar issue and it was the calipers that were gone