one brake disc hotter than the other

sebastianlieken · 08-08-2013 9:17am #1

So I had been experiencing a strange cyclic rubbing noise over the past while at low speeds. (like the brake pads were touching the disc at a high spot).

I identified which wheel it was (front right) by noticing that the front right disc would always be hotter than the front left.

I removed both wheels, discs, calipers, and pads and removed all rust/dirt/ brake dust build up. I made sure the disc was sitting absolutly flush on the wheel hub aswell but I was still getting the noise.

So recently I put brand new brake discs on both fronts. Although the noise is gone (as far as I can tell), my front right disc is still always hotter than the front left.

Any one have any ideas?

car is mk5 golf.

JoseJones · 08-08-2013 9:28am

I had a similar problem on my rear callipers. Have you checked that the pads are free to slide in the carrier? Also check the piston seals to make sure they haven't perished which would allow dirt/rust to build up and stop the piston from retracting. Is the disc slightly warped? I'm not sure if it's easy to tell by eye, I used a DTI and mag base to check mine. Probably a bit ott tbh!

sebastianlieken · 08-08-2013 10:19am

I put copper grease on the pad wings so they can slide on the caliper slider

The piston itself may warrant a bit more attention though...

I couldn't find any warpage or uneven wear in the disk. I just clamped a flathead screwdriver against the disk and rotated the disk... uniform all the way around as far as I could tell.

the piston itself didn't look like it was corroded or anything - just a bit of superficial oxidation where it presses against the back of the pad.

Avns1s · 08-08-2013 10:21am

Did the piston retract easily?

biko · 08-08-2013 10:24am

I had to file down a little on pads once for them to fit into the calipers as they would get stuck and heat up.
Just a little on the touching points so it slides easily by hand.

shamwari · 08-08-2013 11:11am

As an outside bet, is the wheel bearing / hub ok?

sebastianlieken · 08-08-2013 12:30pm

Avns1s wrote: »

Did the piston retract easily?

yep, no problem to rewind them in. barely had to torque the rewind tool.

shamwari wrote: »

As an outside bet, is the wheel bearing / hub ok?

I bloody hope so... My front left wheel bearing went a while back and was replaced. I have none of the same symptoms this time though. No vibrations anywhere, (through peddals, seat, steering, etc). it's very smooth at any speed; it's just that the front right seems to be building more heat.

aside:

I had alot of trouble getting a locking bolt off the front right before (couldn't get the teeth to grip, they were worn down). I tried lots of things but eventually it came to beating an old socket onto it with a lump hammer. I seriously doubt this would have damaged the wheel hub but, it's a minor possibility.

but then, I would have noticed the disc rising and falling when I tested to see if it was warped.

Maybe it is the caliper that's being a bit bold at retracting the piston.

I really hope it isn't the wheel bearing - they're like £100 and it's not a job I can do myself...

shamwari · 08-08-2013 2:15pm

The calipers slide when the brake is applied and the piston extends. The slide pins aren't siezed? This could result in on pad (usually the side opposite the piston) staying against the disk

sebastianlieken · 09-08-2013 12:28pm

shamwari wrote: »

The calipers slide when the brake is applied and the piston extends. The slide pins aren't siezed? This could result in on pad (usually the side opposite the piston) staying against the disk

aye, i'll check the pins and make sure they've got a bit of silicone grease on them too. They're defo not siezed and are still shiney crome with no corrosion - i'll just make sure the rubber inserts through which they slide are good and clean.

Lurching · 09-08-2013 12:52pm

Did you replace the pads when you replaced the discs? If not, the old pad may have only been contacting a lower area of the disc, thus producing increased heat in one spot.

sebastianlieken · 15-08-2013 8:07pm

okay so I finally got around to fiddling with the brakes again (and on my test drive found the most kick ass road ever! one of those roller coaster rolling hills type jobs!

)

anyway, I noticed that the steel pins (slider bolts) were having a very hard time sliding back and forth in the rubber sliders on the caliper. And well, what do we do when the little hole is too tight for our *ahem*... anyway, I lubed 'er up with some castrol engine oil I had lying about (it was that, copper grease, or WD40).

I'm wondering if you generally have to lube up those pins to give them some sliding power? And what is the best lube for a rubber to steel contact on brake calipers?

CJhaughey · 15-08-2013 8:58pm

sebastianlieken wrote: »

I'm wondering if you generally have to lube up those pins to give them some sliding power? And what is the best lube for a rubber to steel contact on brake calipers?

Rubber grease is the best lube, Castrol red rubber grease.
Copper grease will destroy the rubber in short order IME.

sebastianlieken · 16-08-2013 12:16pm

I asked my mate who's a bike mechanic:

A little note on the rubber grease though. I use it for almost everything but I’m starting to phase it out for some things. The red rubber grease isn’t actually water repellent so in some circumstances it can be harmful to use it. Also, when its cold its quite hard and doesn’t seem to lubricate as well as I would like. In applications that will get some heat into it when being used that’s not an issue though. Say with your brakes, they will get warm to hot so it will help the grease. Also I’ve noticed that both my Honda and Kawasaki/Suzuki service manuals specify to use Silicone grease on brake components. Silicone grease seems to lubricate better than the red rubber and is waterproof so seems like a better choice for brakes. You get it in any place that sells diving equipment (used on all the regulator seals etc as its non toxic and waterproof). The red rubber is still great stuff to have around and good for coating the inside of rubber hoses or the likes that are likely to get stuck to wherever they are slipped on. In the future, I’m more inclined to use the Silicone grease for the likes of o-rings and seals in the cooling system and brake components.

Just if anybody is interested.

I may be more inclined to go with silicone grease now instead because the red rubber grease seems to go slightly hard in the cold. Not good when winter is always just around the corner.

CJhaughey · 16-08-2013 3:53pm

sebastianlieken wrote: »

I asked my mate who's a bike mechanic:

Just if anybody is interested.

I may be more inclined to go with silicone grease now instead because the red rubber grease seems to go slightly hard in the cold. Not good when winter is always just around the corner.

Not really a problem on brakes;)

RandomAccess · 17-08-2013 12:21pm

I think one of my rear discs is sticking occasionally. If I was stopped at a traffic light on a really slight slope and didn't appl handbrake I would hear a creaking sound rather like a spring, but I think it's just the brake rubbing. The other week I noticed it sticking after I left the cinema, and when I got home I sprayed some windolene on the disk to see just how hot it was, there was no sound from the rear right but I could feel it was warm, however the rear left made a hiss on contact. Need to get it looked at as I have no facilities in underground car park.

biko · 17-08-2013 3:43pm

Are you able to remove wheel and open caliper?
If so do that and try to remove the brake pads. They should come away pretty easy from the caliper. Grease surfaces between pads and caliper with copper grease (be careful not to get any on the pad/disc contact surface, it will impede braking power) and put them back on again.

Also remove slide pins and grease up with something rated for that job.
Ask in a motor factors for sachets of caliper grease, sometimes they'll just give you a couple free if you buy something else.

Ah, I see you can't do it yourself. Just have a mech look at it. They'll have everything needed and can probably fix it while you wait, unless there's a complication.

one brake disc hotter than the other

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