cleaning rust from brake discs

**jape** · 02-28-2010, 03:38 AM

I'm getting ready to do a home service, strip and clean and tighten or replace on my bike but a few areas on my Kinlon 200 dualsports are showing rust after less than a year, kept under cover, and 600 km ... oh well, rub it down, proof and paint ... except the brake discs, I don't want to oil/wax/paint them of course so what do I best use in this critical area please?

**kupo kupo** · 02-28-2010, 04:37 AM

Is the rust on the pad contact surface? Or near where it bolts on?

Vlad

**jape** · 02-28-2010, 06:45 AM

Originally Posted by kupo kupo

Is the rust on the pad contact surface? Or near where it bolts on?
Vlad

Hi Vlad. It is superficial speckling over the surface, not particularly around the bolts. I want to get to it before it pits. In some cases with rust on bare metal I would leave it as itself forms a protective coat; I would use paint on the frame so welds etc. don't weaken but I don't want to treat the disc surface because I am wary of weakening it and/or losing the grip. It is fine where the brake pads rub as that keeps it shiny. I know the discs will probably be replaced from usual wear before any rust could weaken them so it is mainly cosmetic.

**david3921** · 02-28-2010, 12:07 PM

It's fine to treat the metal anyway you want as long as it's not on the surface where the pads contact. Where the pads contact, scuff up both sides of the disk with 60 grit sandpaper in a circular motion, clean with a thinner (any type but water), dry, and mask off. Now treat the rest with paint or some kind of metal treatment.

**kupo kupo** · 02-28-2010, 05:49 PM

Being a Chinese moto, I'm not really sure what material the manufacturer used for the rotor. I can however share my experience in regards to more standardized Japanese bikes. Most manufacturers prefer stainless steel rotors over iron ones simply because of aesthetics, even though iron performs better. I'm sure many motorcyclists would freak to find their rotors covered in rust after their fist ride though the rain. If your rotors are indeed ss and your overly worried about it, take some medium grit sand paper to it. Don't worry, your actually supposed to sand the contact surface when you change to different pads. If your rotor is iron, which it likely isn't, the only solution is riding more or switching rotors.

GL,
Vlad

**jape** · 02-28-2010, 07:46 PM

Thanks David and Vlad. It is annoying to have to do this kind of work on a newish bike, the same kind of problems jap bikes had in the '60's as I remember, and dual sports bikes, all bikes, are meant to handle the wet! Considering we have had very little rain at all and the damn thing has only been splashed a few times, never soaked, I hadn't expected rust. Now I am finding out why the machine was 'cheap'.

Last year I spent many, many hours rubbing an old trailer down to metal, treating it with branded rust converter then undercoating and top-coating it with well known paints of the correct type. Expensive job all up and many hours of labour. Damned if half the paint hasn't flaked off in the year since and rust is now re-appearing. I did all very carefully as I was told to on the 'instructions'. I hope it will work better on the bike!

**kupo kupo** · 02-28-2010, 08:12 PM

I hope your not planning on painting the rotors. DON'T!

Vlad

**david3921** · 03-01-2010, 12:14 AM

Originally Posted by kupo kupo

I hope your not planning on painting the rotors. DON'T!

Vlad

The rotors on my Honda are painted, just not where the pads contact.

**jape** · 03-01-2010, 12:34 AM

Vlad, I did note that David said before to mask the rotor off so I understood not to paint the while disc. I was going to use engine paint over rust proofer if I did paint it. I assume that painting over the pad/disc contact point is what you warn against? I have to do something, winter is coming to the southern hemisphere so any rust that appeared in summer will worsen.
Thanks, jape

**kupo kupo** · 03-01-2010, 03:14 AM

I think there is a big case of misunderstanding and poor communication. Let me try again. From what I understand, the only place where rust appears on your rotors is over the friction surface. Is it also on the mounting area? If it's only on the friction surface, just sand it. Don't paint it. If it's elsewhere, sand off the rust then mask off the friction surface and have at it with rust proofer, paint, etc.

Hope that helps, GL
Vlad