Mechanics and Fixing Any Questions Answered

Bad man tings.

Ok thanks for the info muchas gracias

Drink a few till the poor brake performance is no longer important.

IPA is iso propoyl alcohol, not Indian pale ale.

IPA is isopropyl alcohol, not India pale ale.

Pronounced ɑ́jsəwprə́wpɪl

I can only speak about motorbike, cars disc and drums. Using a brass wire wheel on a drill to clean discs, as motorbike and car brake pads leave a residue on the discs.

The brass is softer than the disc steel so doesn't damage or wear the disc. I also rough up the pads a little the re bed to pad and disc. Am not really sure how to bed in cycle discs and pads.

I maybe able to pronounce that after a few vodkas and a lager drink.

You don't need to sand rotors unless you're switching pad compound. Sanding a contaminated rotor does fuck all apart from move the contamination around. Assuming it's mineral oil, clean rotors with IPA. If they're resin pads, bin them and put fresh ones on. Sintered you might get away with burning off the oil in the oven, but at today's energy prices, new pads are cheaper.
Assuming DOT, wash the rotors in hot soapy water. See above with pads.

Then bed the pads in properly, drag them til they're warm then 10 or so firm brakes but don't come to a standstill.

And never underestimate the performance advantages of making sure the caliper is centrally aligned over the rotor, then balance the pistons. If one pad hits the rotor first, hold it back using the opposite pad and a flathead screwdriver, and advance the opposite piston. Repeat on either side until both pads contact simultaneously, without deflecting the rotor. A properly balanced brake makes a resounding "ting" noise when the pistons have been balanced right, and it works a lot better

Sanding a contaminated rotor does fuck all

Tim has spoken! I’d like to know why it works so well for the 100 or so times I’ve done it? When combined with some sort of cleaning fluid. If I drop the sandpapering I get worse results.

I’d like to know why it works so well for the 100 or so times I’ve done it? When combined with some sort of cleaning fluid.

Because you've cleaned it.

Sanding takes off the embedded pad material from the rotor (which is microns thick, not enough to hold a contaminant) so it's useful when switching to another pad compound, but there's no reason to do it when cleaning. All it does is mean you have to repeat the bedding in process again, and wears your rotors and pads out quicker.

Sanding is the quick and easy way to just get the job done. Sand the cunt, wash the cunt. No room for BS

Drop contaminated rotor into the RO/Oz juice washer and leave it overnight for best results, thank me later.

Dot fluid is neutralised with water, add some heat and soap and that's all you need.
Mineral oil is more difficult to clean, but isopropyl is all you need. Sanding just pushes whatever contamination that's on there around the rotor, possible even into the scratches you've just created.

I will die on this hill.

Scotchbrite and lots of brake cleaner

https://en.m.wikipedia.org/wiki/Scotch-Brite

I will die on this hill

Technically, you'll die at the bottom of it because your brakes can't hold you on the incline

When I have cleaned brake rotors on bikes, I have used a brass wire brush on a drill. With the disc on a piece of glass (well a glass chopping board) to keep the disc flat.

This is usually after using brake cleaner in the disc. Also I clean the holes in the disc out with a drill bit. Makes sure I don't create an edge on the hole.

As for dot contamination I just use hot water and car shampoo as it doesn't contain salt.

As for centering, I thought calipers self centered.

Green scouring pads are a quick and easy to get hold of alternative.

Told not to use brake cleaner on bike disc as brake cleaner can leave a residue, hence why you are supposed to use IPA

I presume that's motorbikes...
A caliper will never self centre unless all the pistons move equally, which invariably they never do.

Told not to use brake cleaner on bike disc as brake cleaner can leave a residue, hence why you are supposed to use IPA

Correct. If you also do welding in the same space, the brake cleaner fumes will kill you

Why? Heat or uv? Just thinking I should be very dead by now.

The brake rotor cleaning is cycles. Motorbike discs are strong enough to not deform.

The self centering is something I have never though of, but makes sense for a cycle with thinner discs.

On cycles I have only had single and double piston calipers. That didn't seem to have that issue, that I noticed.

Is it not any source of heat/flame?

Thought most brake cleaner in the UK is not the kind that does that. But yeah be careful.

Have wiped car drums and shoes with cellulose paint thinners in the past and the braking was highly improved.

Okay, so I’m gonna chim.

Both of you and @MCamb is right.

Sanding down rotor does do the trick, sure it may feel rough and horrid until it start to wear in, it can also contribute to the pads wearing out a tiny bit faster until it wear in with the rotor, performance might not be 100% as it once was, but does the trick.

It’s also doesn’t always work, sometime I’m lucky, other time it squeal and need further sanding.

In our workshop, it’s always better to just quote new pads and rotors if it’s contaminated because we can 100% offer our guarantee that it will work and completed in a timely manner.

On MTB, people aren’t that fussy as long the brake work better, we often sand down the rotor and put new pads but it really a case by case basis.

Mechanics are not cheap, they work on £60/hour (or complexity of jobs), it’s much cheaper at the time to go for a new pads and rotor, and never have to come back until the next service/fuck up.

Both, I believe. Creates phosgene gas, which isn't great for you

Agreed. If something is badly contaminated enough to need sanding, you should be replacing everything anyway