Got GT85 on brake disc. Now what?
Got GT85 on brake disc. Now what?
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nsi

Original Poster:

329 posts

227 months

Sunday 2nd September 2012
quotequote all
Accidently got some GT85 on my brake disk whilst lubing up. D'oh! However didn't notice until I was out riding and front braking performance is basically none. Brakes are Avid Elixir 7 hydraulic disc brakes.

When I got back I wiped off what I could from the disc with some muck-off and paper towel, and also removed the brake pads and rubbed them on some sandpaper to clear some of the contamination. However the braking power isn't back still. So I got some brake cleaner spray from Halfords and used some of that on the disc, which should be better than muck-off for this job? Braking performance is better, but not amazing like it used to be.

I'm thinking I'll go and remove the wheel again, clean the disc with brake cleaner again and let it dry. In the mean time remove the pads and give them a bit more sanding to take some more surface off. Then let everything dry, then re-assemble, then go for a ride and see what happens after a bit more bedding in. (As I expect the pads need to bed in again after using the sand paper on them.)

Quick, before I go out and start spraying/cleaning/sanding again can you tell me if this sounds sensible or mental?

Cheers.

Pupp

12,948 posts

301 months

Sunday 2nd September 2012
quotequote all
If you'd have just ridden it, it would have been fine soon enough. 'Sanding' the pads will just fk up the facing surfaces and possibly the rotor too if you've embedded abrasive media from the paper in the pads ('though it's prolly going to be no worse than a wet day in the Peaks)

balders118

5,940 posts

197 months

Sunday 2nd September 2012
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Cleans the discs, replace the pads. Simple. We've all done it!

joema

2,754 posts

208 months

Sunday 2nd September 2012
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Need to find a good size hill and keep braking hard. Basically just need to get heat into them.

y2blade

56,318 posts

244 months

Sunday 2nd September 2012
quotequote all
clean it off with brake cleaner.

dudleybloke

20,553 posts

215 months

Monday 3rd September 2012
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if you've contaminated the pads replacing them is the best option. (found out the hard way)
i took it as an opportunity to get some kevlar pads from superstar components!

nsi

Original Poster:

329 posts

227 months

Monday 3rd September 2012
quotequote all
Cheers chaps. The pads are/were definitely contaminated; you could see the change in colour on the surface of the pads. However after a little light sanding on a bench they are now a uniform colour again. This time around I sanded the pads at the same time as re-cleaning the disc about 3 times with brake cleaner and paper towel. I've left them overnight to dry and will go for a test ride tonight.

I expect the pads will need bedding in again, as I presume I'll have spoiled the mating surfaces. (And also the pads need to leave a thin layer on the discs again.) So I'm hoping that after bedding in the power will come back again.

I did some googling in the mean time and it seems that brake cleaner/sanding is pretty standard. But a lot of people also repeated the advice here, that the rotors are savable, but the pads may be scrap frown

If the test ride/re-bedding doesn't work then I've one last ditch attempt to save the pads: baking them until they smoke. Apparently this will burn off the oil which is on them and bring them back to life. Sounds a bit scary, but if the alternative is buying new pads then I don't see any downside to baking them. If it mends them then great, if it ruins them then no loss as they are ruined anyway.

Cheers

Gren

2,030 posts

281 months

Monday 3rd September 2012
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Can't harm to sand them, bin em and replace if this doesn't work. Use isopropyl alcohol (or brake cleaner) on the rotors at the same time or you're just re-contaminating.

dome

688 posts

286 months

Monday 3rd September 2012
quotequote all
Take the pads out and stick them in the oven. Gas mark 6 for, ooh, a bit. The GT85 will burn off.

This does work. Your next chicken kievs may taste a bit funny tho.

a11y_m

1,861 posts

251 months

Monday 3rd September 2012
quotequote all
Gren said:
Can't harm to sand them, bin em and replace if this doesn't work. Use isopropyl alcohol (or brake cleaner) on the rotors at the same time or you're just re-contaminating.
This. Maplin sell nice big tins of isopropyl alcohol (I find it better than the muc-off disc brake cleaner I also bought).

However, I've never had great success with rescuing contaminated pads - they're never the same again. I only ever use Superstar/Uberbike pads at approx £6/pr though so don't see it as a major loss.