Brake disc caliper misalignment issue?

[Deleted]

OK it started as an mot issue, but hold on guys before you advise this is the wrong place to post . I tested a Vauxhall Astra G 2001 1.6 SI (spark ignition) the other day and the front brake imbalance was 55%, the rate of increase and decrease clearly not about the same rate, all in all a clear fail no question about it.

I removed the road wheels and removed the sliding calipers but not disconnecting the hydraulics. I don't allow the calipers to hang on the brake hoses once removed from the wheel hubs. . I removed the brake pads which had a good 5mm thick lining material left at their lowest point. I didn't find any brake pads seized when removing, nor did I experience any problems when using the brake wind back tool to push back in the brake caliper pistons, however I did notice that the nearside front brake pads anti-damping spring was missing at the time of removal of the pads. 

I measured the brake discs thicknesses at their lowest points and found them to be below the manufacturer minimum 21mm, so I ordered new brake discs and pads and cleaned everything up and re-assembled . I road tested the car for about five miles and can't say I noticed anything wrong, then I put the car in the mot bay and set the headlamp alignment, still not noticing anything wrong. I reversed the car into the rollers and then checked the front brakes, the nearside front brake was binding recording a reading of 40Kgf, the brakes imbalance was about 30%. The rate of increase and decrease at this time was within the maximum 30% range.

I took the car back home (because the job is a foreigner) and at that point I could smell the nearside front brake was operating too hot. I let the brakes cool down and then removed the road wheel to see what was wrong?

I found nothing obvious, so I removed the brake pads and a visual inspection of the outer brake disc face shows that the outer pad is overheating, and seemed to be operating misaligned. The pads and discs are brand new German manufacturer (can't remember the name without looking back at the box sent in)  and so now I am really suspecting that a misalignment issue is causing this problem. Further road testing and using an infra red temperature measuring device (yes I know not the most accurate) but is able to show me that their is a good 20 to 30 degrees increase in working temperature of the nearside front brake. 

The fitment of the brake pads and caliper did not present any issues during fitting and so I did not suspect a misalignment issue, but quite obviously there is as the disc is changing colour with the heat generated. When the road wheel is jacked up there is no brake bind present when the road wheel to turned by hand, which was very confusing?

Any thoughts on this guys?

[rpm]

I dont see how a misalignment issue would cause overheating/binding without causing more noticeable effect like vibration/rotational restriction.

More like a flexy hose i would have thought, releasing pressure unequally to the other side ?

[Noberator]

Overheating of the brake pads is caused if the brake caliper is stuck or not moving freely.

[Karl]

What I don't get is why there wasn't any signs of overheating on the old discs/pads

Maybe it's because the piston is now in a different position

What's the fluid like ? Not been changed in years I'd suspect

[Deleted]

Thanks guys for your replies , the nearside front (original brake disc faces) had no signs of over heating at all. I have checked the function of the brake hose using an assistant depressing the brake pedal while I open and close the caliper bleed valve observing the fluid flow, the results suggest that the brake hose is functioning ok. I also checked with the help of an assistant the operation of the brake caliper piston for moving out and then me winding the piston back in with the wind back tool doing this repeatedly where I can't see anything obviously wrong with the operation.

Visual inspection of the new brake disc fitted has severe heat discoloration ONLY to the outer face where the inner face is in perfect condition. The outer brake pad visually looks to be aligned correctly when fitted, but when removed the rubbing face shows that it is not contacting the disc face correctly after a few brake applications. The only difference between the old brake parts fitted and the new parts fitted is the inclusion of a brake anti-rattle damping spring to the outer brake pad, which was originally missing from the old pad.

The offside front brake assembly has been put together exactly the same as the nearside front and there is no operational problems at all with it.

This is a first for me with the nature of this fault, so tomorrow evening it will be photo time and see if you guys can see anything obvious that I have missed???

The reason I am thinking misalignment is because the only difference to the brakes between now and before is the anti-rattle damping spring that was missing previously. 

[Noberator]

Is there any play in the wheel bearing which may cause misalignment?

[Karl]

Drive until it's binding again , then check what's not releasing

[Deleted]

Nothing that I have noticed either during the mot test or while investigating the fault pulling and pushing on the road wheel at home.

[Deleted]

Karl that will be the routine tomorrow evening after another visual inspection and photo shoot

[Rhubarb]

I'm wondering if there is a wear ridge inside where the caliper sliders go through the caliper, because without the rattle spring fitted it would have been straining at a strange angle

Pop the pads out and refit the caliper and move it each way by hand.

[rpm]

Jul 30, 2014 22:56:46 GMT 1 harry said:

Thanks guys for your replies , the nearside front (original brake disc faces) had no signs of over heating at all. I have checked the function of the brake hose using an assistant depressing the brake pedal while I open and close the caliper bleed valve observing the fluid flow, the results suggest that the brake hose is functioning ok. I also checked with the help of an assistant the operation of the brake caliper piston for moving out and then me winding the piston back in with the wind back tool doing this repeatedly where I can't see anything obviously wrong with the operation.

Visual inspection of the new brake disc fitted has severe heat discoloration ONLY to the outer face where the inner face is in perfect condition. The outer brake pad visually looks to be aligned correctly when fitted, but when removed the rubbing face shows that it is not contacting the disc face correctly after a few brake applications. The only difference between the old brake parts fitted and the new parts fitted is the inclusion of a brake anti-rattle damping spring to the outer brake pad, which was originally missing from the old pad.

The offside front brake assembly has been put together exactly the same as the nearside front and there is no operational problems at all with it.

This is a first for me with the nature of this fault, so tomorrow evening it will be photo time and see if you guys can see anything obvious that I have missed???

The reason I am thinking misalignment is because the only difference to the brakes between now and before is the anti-rattle damping spring that was missing previously. 

Caliper sticking, sliders seized worn, as rhubarb says

[Deleted]

That's very good advise Rhubarb  and a visual inspection of the caliper guides will be completed tomorrow although the caliper pins having been cleaned greased and replaced didn't show any abrasions or wear, however I wonder as you rightly point out about the guides if now the caliper being aligned correctly is restricting the caliper movement because the pins threads areas might be slightly misaligned because of the unequal forces acting through the caliper over a long time period?

I must admit I never thought about that and will check the pins tomorrow, thanks again  

[Rhubarb]

Jul 30, 2014 23:38:48 GMT 1 harry said:

That's very good advise Rhubarb  and a visual inspection of the caliper guides will be completed tomorrow although the caliper pins having been cleaned greased and replaced didn't show any abrasions or wear, however I wonder as you rightly point out about the guides if now the caliper being aligned correctly is restricting the caliper movement because the pins threads areas might be slightly misaligned because of the unequal forces acting through the caliper over a long time period?

I must admit I never thought about that and will check the pins tomorrow, thanks again  

No worries

[Noberator]

Jul 30, 2014 23:46:40 GMT 1 Rhubarb said:

Jul 30, 2014 23:38:48 GMT 1 harry said:

That's very good advise Rhubarb  and a visual inspection of the caliper guides will be completed tomorrow although the caliper pins having been cleaned greased and replaced didn't show any abrasions or wear, however I wonder as you rightly point out about the guides if now the caliper being aligned correctly is restricting the caliper movement because the pins threads areas might be slightly misaligned because of the unequal forces acting through the caliper over a long time period?

I must admit I never thought about that and will check the pins tomorrow, thanks again  

No worries

No arm in checking.

[wheelnut]

As a matter of curiosity why are you using a wind-back tool on the front? The handbrake is on the rear wheels so the front pistons should just push back. If they do not push back without difficulty it would add to my suspicion that you have a faulty calliper. You could try squirting a few cc's of brake fluid under the rubber boot to see if a little lubrication around the piston helps. That would definitely indicate a faulty calliper.