SheffieldSam

Morning everyone, just want to ask for a little advice from you helpful folk.

On Wednesday after a short drive I noticed the n/s rear brake felt substantially hotter than the o/s. On Thursday evening I took that brake caliper apart on the bench to investigate why. The slider pins felt fine - no binding in them at all, but the piston felt very stiff. I managed to get it turning again by putting it in the bench vice and applying my turning-tool (bolster chisel and a large adjustable wrench) and the piston moved a lot more freely.

On Sunday I reassembled everything, checked that I could move the wheel by hand (I can), and that I can push the car back and forth with no handbrake (I can) and went for a test drive The n/s rear brake disc measured around twice the temperature of the o/s (infrared thermometer). After the half hour run to work this morning I measured again, and once more it was substantially higher temperature.

So to sum up:

• One rear brake is getting a lot hotter than the other side
• It's not fully "bound" as I can move the wheel by hand and push the car back and forth with no handbrake

Problems:

1. I need the car for Sunday (Donington Historic)
2. I am intending either rebuilding, or paying someone else to rebuild, all four calipers this winter (and give them a lick of paint at the same time)
3. I have no money

Solutions:

1. I have a theory that the handbrake is dragging because the lever only manages about 5 clicks before being fully engaged - I read in the manual it should be closer to 9-14. So tonight I'm going to pop off the center console and completely slacken off the handbrake and go for a test run
2. Get a replacement second hand caliper and fit it this week as a short term solution until the winter rebuild

Questions:

1. If I get a replacement caliper, would I be better doing both sides or is this overkill for calipers?
2. Where's a good place to get a new caliper delivered from?
3. Does the handbrake idea sound likely?
   

Any other suggestions?

Nottm_S2

What was the temp?

Maybe your other one is barely working? If they get really hot the pad can fail (happened to me). But if the piston looks clean and the pins are greased it should all be good.

SheffieldSam

Good shout.

The "hot" one was up around 100°c this morning
The "cold" one was around 25-30°c.
Ambient was maybe 10°c.

Nottm_S2

100C is not hot really

As a rule of thumb for me during normal use if the wheel warms up its a problem.

PiSoft

I'd say the same here.

Recently I had a slight problem with one of my my front brakes. I have realized the problem when the car started to pull to one side due to binding brake on that side. I pulled over and had a quick assessment.
Long story short, even the wheel on the binding side started to warm up quite much. I could feel the temperature difference by hand, I could not touch the caliper body as it was so hot. The other side caliper body was just warm, the rotors were too hot to touch both sides.

So I'd have a look of your 'cold side' brakes, you may find that the piston is (about to be) seized and no (very little) braking action is present.

If you are good with the spanner, just pull the caliper apart, clean, lubricate and assemble. It's a good insurance to do yearly anyway...

lower

Good point that the other rear brake that's cool is not actually doing any work.

However, money or no money, don't even think about doing a track day unless you know your brakes are 100%. Get them fixed.

SheffieldSam

Fear not - trackday is a month away so plenty of time to get this sorted before then. Thanks though :-)

So what's the recommended way of testing the other caliper for laziness? Get the rear in the air and see if I can turn it while someone else pushes on the brakes? Even if the caliper is only working "a bit" I would have thought that would be enough for me not to be able to turn it.

Nottm_S2

If you give it a bit of beans then measure temps on all 4 you'll know whats working

dan_bourne

if youve taken one off to free it up, why not do the other side, it doesnt cost anything, you might find the slider pins or piston are binding on that side, when regreasing the slider pins, dont use copper slip, use something like 'mintex ceratec'.

could be something simple, if a previous owner hasnt looked after something it normally rears its head at some point!

lower

MOT testers can measure the brake balance for a definitive answer.

I would strip and clean the other rear brake in the same way as the other side and then drive the car to see what effect it has on wheel temperature.