Disc brake rotor question

[stepawayfromthemachine]

Not my best bike by any means, but I have a Shimano disc equipped hybrid for commuting duties. I don't have discs on any of my other bikes so have no experience of the replacement criteria.

The bike gets lots of abuse and is used through all weather and seasons, and a couple of weeks ago they started to squeak quite badly and at the last moment of coming to a complete halt they make a rather loud graunching noise. I think there may have been some contamination on them which has caused them to glaze up.

Performance is definitely down on how they've worked previously, so I've stripped them down and have ordered a new set of pads. I'm most likely going to order a new set of discs too, but I'm interested to here people's experience as to if the discs look like they need replacing or not looking at the images below.

The discs are centre lock Shimanos, and have a fair bit of scoring (you can feel this with your nail) they are about 1.5-2mm thick.

Cheers, Si

 

[mk one]

Is that a lip on the disc? if so i would change them

Mark

 

[Timoth27]

Re:

I would change the rotors and the pads. Looking at that lip I would also check they are the right size, the rotors look a bit big to me

 

[stepawayfromthemachine]

Re:

Yep there is a lip on the rear disc so new pair ordered along with the new pads. I've owned the bike from new and the pads and discs are both OEM as fitted when I picked it up so would be surprised if they are not the right size?

Is it the pad you are saying is the wrong size, or the disc?

 

[Timoth27]

Re:

The only reason I say they look the wrong size is that there seems to be wear onto the spokes of the rotor (if you know what I mean) along with the lip it looks like either the rotor is too big but more likely the calipers are not quite in the right position, maybe needs an additional shim under it?

 

[jimo746]

Re:

Rotors : I think Shimano recommend changing when the thickness of the disc reaches 1.5mm.
If the pads are not quite hitting the outer edge of the rotor then you can simply put a small washer under each end of the caliper to space it out a few mm. Ive had to do this on a couple of bikes in the past.

Noise: sounds like contamination on discs/pads. Try using some brake cleaner spray (I use car stuff), or change for new pads, and while the pads are out check the piston on the caliper, they can be known to leak a little brake fluid which contaminates pads straight away.

 

[stepawayfromthemachine]

Re:

Right ho, thanks for the responses guys, totally see what you're saying now.

Will make sure everything is in the right position when I reassemble, and I'll check there are no leaks also. Be rather annoying to fit new pads and discs only for those to be ruined straight away too!