BR-M445 reduced braking power

russelle

Hi,

I have a Voodoo Bantu with BR-M445 brakes. After using it for a good while for commuting 4 miles total per day, I replaced the rear pads & since then the stopping power has deteriorated.

With the original pads stopping was fine but they needed replacing. I got a twin back of pads from Disco Brakes, fitted one set & everything was fine for about 30-50 miles then the efficiency started to drop off & the rear brake was making a loud squeal when the rotation was slow, i.e. just before I came to a stop.

I thought I had contaminated the pads somehow so thoroughly cleaned the rotors & fitted the 2nd set. All OK until another 30-50 miles then the same problem as before.

By this time, I thought it must be the pads in general so I got some Clarkes pads, cleaned everything, fitted the pads but same result as the previous 2 times. This time I took the bike to the top of a long hill & got the pads really hot to see if that would make a difference. It didn't.

OK, after spending time examining everything very closely, I could see that there was no fluid leaking so that was fine but I noticed the rotor was lipped.

Order up a set of Shimano pads, swap the rotor for a barely used one & off I go again!

Same problem!

This is driving me nuts now as I am lost as to what is wrong! I've replaced disc pads on bikes for years & never had this problem.

Can anyone give me something to try before I go mad!

nicklouse

Sounds like you are either contaminating them or glazing them.

cooldad

Seems strange to be using up the rear pads before the front.

Are you dragging them?

russelle

They aren't contaminated, glazed maybe although I don't know why they should be.

Not dragging them, no.

I've had bikes with disc brakes before & never had this problem which is what's got me stumped!

buddy_club

What are you using to clean the discs, and what compound are the pads you are buying? Sintered, organic etc...

russelle

Muc-off disc brake cleaner & resin pads (B01S)

buddy_club

Hm Squealing is usually because of wetness, but if its been getting really hot i wouldn't think that was the case. Have you tried going in to your local Halfords (only worth a try if there's a decent mechanic who knows about bikes there)?

russelle

When I was last in there I mentioned it, the guy said only to use genuine Shimano pads & said that would solve the issue.

it's so bad that I can squeeze the lever as hard as I can & it doesn't slow the bike at all.

buddy_club

Tbh i don't really know mate, sorry i couldn't help more, i had this issue on the BR-M395's on my Bizango but a new set of Sintered pads sorted it straight away.

russelle

no worries, thanks for taking the time to reply.

I Seem to remember seeing something on the rotors about resin pads only.

cooldad

Ignore it, any pads work fine.

russelle

It's OK, the one I replaced it with is an RT61 anyway!

I'll get some sintered on order.

*AJ*

The shimano resin pads are a bit rubbish in anything but perfect conditions!

I run the cheaper shimano brakes on my commuter and as soon as I changed to superstar organic pads there was a huge improvement.

swod1

Another thing, do the brakes need a bleed or something ?

My m446 brakes have been going strong for nearly 2 years now and only just coming up to changing pads which I'm going to try out some superstar Kevlar or organic as the squeal when the discs are wet off sintered is starting to annoy me a bit.

russelle

Nope, no need to bleed them.

Rightarmbad

Put the pads that squeal onto the front and see if they squeal there.
My bet is they will.
It sounds like they are getting contaminated.
Look out for a fine layer of grease/oil creeping up the disc from the hub or spotting from a wet chain or exuberant lube application to the chain.
Riding in the wet will aid the oil creep.

Don't use disc brake cleaner on Shimano brakes, you will find a warning re this on the Shimano tech docs site.
It messes with the seals. It's OK on the rotors though.
Shimano also says not to use sintered pads on their icetech rotors as the steel outer lining is quite thin and leads to problems when they thin down too much.
The applicable rotors usually have a warning printed on them.

My bet is that if you wipe the disc and hub down with alcohol, clean the chain and run a dry type lube, fit new pads and check general alignment and piston operation that the problem will disappear.

russelle

I've always cleaned the rotor before a pad change.

On the ride home tonight, there was almost zero effect from pulling on the lever.

At lunch time I ordered a set of sintered pads. I'll fit those & see how it goes.