Hi all

I decided to replace the master cylinder firstly as I thought it could have been my error.

Anyway, looking at the rear discs 100ish miles after replacing the Master cylinder, the sides of the discs nearest the wheels on both sides look good and braking clean and even on the discs (as they should be)

On the insides on both rear discs are rough with lines from rust and not braking clean and smooth.

Am I just been paranoid and should I just get on with it? After spending a lot of money on new parts for the brakes and been as they are new. I don't really want to settle for less than a new vehicle would be.
Can anyone help please?
 
trax said:
got the shields still on? are pistons moving as should be?
Click to expand...
I've removed the shields trax.

Bled many times too. So air is out the question.

And regarding the pistons... I presume so due to being fairly new calipers (6 months old) but I suppose they could be duff. With new discs and pads I would have thought the pistons would be fairly far back into the calipers. However I haven't had the wheels off to check
 
if you are happy with the braking, then i'd say you are probably paranoid.

you usually always have one side of the pad wear more than the other.

if you are really concerned, get it on a brake tester and it'll tell you what each wheel is doing :)
 
trax said:
if you are happy with the braking, then i'd say you are probably paranoid.

you usually always have one side of the pad wear more than the other.

if you are really concerned, get it on a brake tester and it'll tell you what each wheel is doing :)
Click to expand...
Cheers Trax.

They are braking well to be honest. I'm going to take the wheels off and have a closer look to see what the pistons are doing. And go from there. Maybe get it on the rollers. Thank you
 
ONE LIFE LIVE IT. D90 said:
Cheers Trax.

They are braking well to be honest. I'm going to take the wheels off and have a closer look to see what the pistons are doing. And go from there. Maybe get it on the rollers. Thank you
Click to expand...

I'd leave all well alone and fix something that needs fixing.

The back end of a 90 is very light and the brakes don't do a hell of a lot unless there is a load/trailer on the back. My rear discs do this quite a lot when I go through long spells of it not doing any heavy load hauling. Last summer I bought heaps of concrete making supplies and was hauling a half ton of sand and aggregate in the boot. I was aware this was going to give the rear discs a workout and had a look at them before I set off, they were clean enough but looked very similar to yours, sort of underused, when I got back to the house with all my supplies the rear brakes looked positively shiny.

I have genuine lockheed calipers on the back, rebuilt with genuine seals, they were very clean when I rebuilt them, I have a low mileage, 2/3 year old gen master cylinder. I have a G valve on the front bulkhead bracket which clearly works as I don't tend to lock up the back end but when carrying heavy loads or towing I can feel the back end pulling down when braking and as said the discs shine up, so clearly all works fine. I personally think you would be wasting your time taking things to pieces as you are not going to fix it.

Those who don't get this rusty disc issue possibly work their vehicles harder, drive them more frequently and longer miles so they just stay clean through use or their biasing valve isn't working properly allowing too much braking force to the back axle.
 
Last edited:
discomania said:
I'd leave all well alone and fix something that needs fixing.

The back end of a 90 is very light and the brakes don't do a hell of a lot unless there is a load/trailer on the back.
Click to expand...

I agree. the rear shoes (drum brakes), on mine have been there since I bought the vehicle in 2008, and the friction material doesn't seem to have worn at all :D
 
If in any doubt rev up and let go. When the engine begins to slow down jump like feck on the pedal. That should free off any binding pistons.

It works for me!
 
discomania said:
I'd leave all well alone and fix something that needs fixing.

The back end of a 90 is very light and the brakes don't do a hell of a lot unless there is a load/trailer on the back. My rear discs do this quite a lot when I go through long spells of it not doing any heavy load hauling. Last summer I bought heaps of concrete making supplies and was hauling a half ton of sand and aggregate in the boot. I was aware this was going to give the rear discs a workout and had a look at them before I set off, they were clean enough but looked very similar to yours, sort of underused, when I got back to the house with all my supplies the rear brakes looked positively shiny.

I have genuine lockheed calipers on the back, rebuilt with genuine seals, they were very clean when I rebuilt them, I have a low mileage, 2/3 year old gen master cylinder. I have a G valve on the front bulkhead bracket which clearly works as I don't tend to lock up the back end but when carrying heavy loads or towing I can feel the back end pulling down when braking and as said the discs shine up, so clearly all works fine. I personally think you would be wasting your time taking things to pieces as you are not going to fix it.

Those who don't get this rusty disc issue possibly work their vehicles harder, drive them more frequently and longer miles so they just stay clean through use or their biasing valve isn't working properly allowing too much braking force to the back axle.
Click to expand...
Thanks discomania.

Beleive it or not. I've actually finally fixed all problems on it. Can you believe I've said those words.

I just found It odd that the outside of the discs are braking perfect on both rears. But the insides aren't. So it can't be a weight issue can it?

I bought the discs from amazon for £30 for mintex. I'm not sure if they are knock offs. Because they seem to rust up so quick compared to the fronts
 
some cheap ones can rust quicker, if your braking on one side of disc more and wheel bearings are good you need to look at pistons and calipers
 
jamesmartin said:
some cheap ones can rust quicker, if your braking on one side of disc more and wheel bearings are good you need to look at pistons and calipers
Click to expand...
James.

I whipped the wheel off one side of the rear yesterday, took the pads out and had a look what was going on with the caliper pistons. They were spotlessly clean and both pistons came out of the caliper evenly when the brake pedal is pressed by a assistant. Couldn't see any issues with the calipers at all.
Inspecting the pads showed that only one side was working again. It can't be down to the pistons as they were perfect.

I don't think there's enough pressure getting to the rear calipers, I remember the pressure being much less when bleeding the rear to the fronts.

I'm absolutely stumped by this now. Very confusing. The discs are covered in like black spots and rust so I think poor rear caliper action has ruined them along with them being crappy.

Any ideas please guys
468337668d283585c2c6818d7a152fb7.jpg
 
Try towing a heavy trailer or put some heavy stuff in the rear end and drive around for a bit using plenty of brakes. Reading the other posts makes me think the brakes are not coming on full because they are not being "demanded". I'd give it a go as it costs nowt to check it.
 
you can sandpaper them if you want.

since you are so concerned, i'd ask a garage with a 4x4 roller to give you the braking efficiency of each wheel. that will tell you if something is wrong. it will only be 20-30quid


ONE LIFE LIVE IT. D90 said:
James.

I whipped the wheel off one side of the rear yesterday, took the pads out and had a look what was going on with the caliper pistons. They were spotlessly clean and both pistons came out of the caliper evenly when the brake pedal is pressed by a assistant. Couldn't see any issues with the calipers at all.
Inspecting the pads showed that only one side was working again. It can't be down to the pistons as they were perfect.

I don't think there's enough pressure getting to the rear calipers, I remember the pressure being much less when bleeding the rear to the fronts.

I'm absolutely stumped by this now. Very confusing. The discs are covered in like black spots and rust so I think poor rear caliper action has ruined them along with them being crappy.

Any ideas please guys
468337668d283585c2c6818d7a152fb7.jpg
Click to expand...
 
ONE LIFE LIVE IT. D90 said:
James.

I whipped the wheel off one side of the rear yesterday, took the pads out and had a look what was going on with the caliper pistons. They were spotlessly clean and both pistons came out of the caliper evenly when the brake pedal is pressed by a assistant. Couldn't see any issues with the calipers at all.
Inspecting the pads showed that only one side was working again. It can't be down to the pistons as they were perfect.

I don't think there's enough pressure getting to the rear calipers, I remember the pressure being much less when bleeding the rear to the fronts.

I'm absolutely stumped by this now. Very confusing. The discs are covered in like black spots and rust so I think poor rear caliper action has ruined them along with them being crappy.

Any ideas please guys
468337668d283585c2c6818d7a152fb7.jpg
Click to expand...

quite possibly you are down on the rears , master cylinder is 2 pumps in 1 ,with part doing fronts and part doing rears, though poor discs and braking is not uncommon on the rear
 
trax said:
you can sandpaper them if you want.

since you are so concerned, i'd ask a garage with a 4x4 roller to give you the braking efficiency of each wheel. that will tell you if something is wrong. it will only be 20-30quid
Click to expand...

good advice, info is vital
 
Wimblowdriver said:
Try towing a heavy trailer or put some heavy stuff in the rear end and drive around for a bit using plenty of brakes. Reading the other posts makes me think the brakes are not coming on full because they are not being "demanded". I'd give it a go as it costs nowt to check it.
Click to expand...
I've filled the rear as heavy as I could with no difference whatsoever
 
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