Technical Brakes again...

[koalar]

Yes, I do.

Bit sketchy

you can lift the front, chock the rears and spin the wheels up,

I have tested a rebuilt gearbox this way, before flushing and filling with expensive gear oil

You will get an ABS error, as far as I remember that error self clears once you drive the car normally

It's surprising how slow the wheels spin even at 70mph

You will have to use the brakes a few times to be a fair test


My car has thicker alloy wheels I have just done 10 miles down a dual carriageway and pulled up fairly gently 3x popped my hub caps off, the center is still cold and the disc are too hot to touch

 

[koalar]

Why are these moving like this? Doesn't it have any spring clips?

They are suppose to

The springs are on the caliper itself

Which appears to be missing in @xf1ref video

 

[xf1ref]

you can lift the front, chock the rears and spin the wheels up

I already tried this but only one wheel at a time but I will do with both in the air and let the car to run some time.

Which appears to be missing in @xf1ref video

They were removed by me.

 

[koalar]

I already tried this but only one wheel at a time

What was the result?

 

[The Panda Nut]

I have never measured the temperature, but brakes do get very hot when the car is driven briskly or on hills etc. I do feel wheel temperatures and you should normally be able to touch the wheel with the palm of your hand unless you have been going pretty mad. 67 maybe getting up but its not ridiculous.
BInding and dragging brakes stink, discs become blue quite quicly and brake dust build up is noticable very quickly. I feel the wheels to check side to side is not madly different and have been doing this for years as a basic check. Brakes are designed to dissipate heat through the hubs and wheels. If these are quite warm are quite normal.
My own work on our 169 2011, ended with new brake hoses and calipers. The brakes are now fixed, the whole disc is shiny on both sides and the car pulls up straight. I am wholly convinced the caliper sliding arrangement on the Panda is pretty duff and that softening of the rubber bushings allows the caliper to twist when the the brakes are used. This will cause some sticking both when the brakes are applied and released. While not slack enough to show any movement when checked stationaly. It seems to be the only thing that could be resonsible for the issues I had. Calipers are cheap and fairly certain to fix most brake issues. Front wheels should turn without hearing the disc dragging too much, but you will hear a noise unless thepads are fully backed off. You cannot spin the wheel and expect to see it continue spinning round due to gearbox drag. If the pads are free and the disc not blue the brakes sound to be broadly OK. Internal collapse of brake hoses is not unknown and can mean brakes dont release as quickly as they should leading to heat. Try driving the car and using the brakes faily hard for a few miles so they are going to be on the hot side of average. Measure the temerpature every 10 minutes on both sides and compare side to side temps and how long they take to cool. That may show something interesting. If they are within a few degrees and they cool back down at a similar rate I dont think there is too much of an issue. Hot brake disc will cause water to boil off instantly so above 100C at least is normal if the brakes have been used more than a little. If the brake pads are as free as you have shown and the car pulls up straight I would be happy if it were mine. The issue of the discs rusting is at least in part due to the caliper bush condition. The crude design of the panda brakes seems to mean they cease to function too well with less wear than more sophisticated designs. I wish I had none my calipers sooner! Notable the 319 Panda has a more sophisticated design and seems to work longer between clean ups and respond better. If not already done I would at least change the sliders and the caliper bushes. If the pistons are moving freely this should eliminate any problems caused by them, and they are available and cheap. Most good makes of calipers of course have these parts replaced anyway. LAstly if the car is put in a rolling road brake testeras used for UK MOT's its the operation that is most important and you can see how the two sides efficiency compares accurately.

 

[The Panda Nut]

I already tried this but only one wheel at a time but I will do with both in the air and let the car to run some time.

They were removed by me.

If you have ABS it will throw errors doing this. Both wheels off the ground and one will go backwards and one forwards due to the diff, and not necessarily at the same rate.. Not helpful. I wouldnt do it as I dont think the diff will not like it. You dont want to damage that! One wheel should be OK. I did wind my company car on several thousand miles once at tickover using the jack up method to improve the mpg..... Left it ticking over all night in 5th gear each night for a week. The ABS light had to be switched off but other than that no damage.

4 degrees is nothing

You don't know if the cool one is doing slightly less work

Even the side of the sun makes a difference if it's out

15 miles of stop start is not a good test

The whole point of the brakes is to convert forward motion to heat. There's a lot of energy to be lost in a lump of metal travelling at 30mph to a stop in a few feet

If you want to see if the brakes are dragging, you need to drive without using the brake, so any heat build up is due the dragging

Hammering it from leek to Macclesfield is enough to get brake fade 350C (13 miles)

Yet when driving slow Crewe to Telford and they are below 40C (40 miles)

And everything in between

Sounds very normal to me. Some small temperature variation of this sort could be down to variation of the pads and discs themselves side to side. Both sides more or less the same shouts normal to me. Dragging brakes will never be the same temperature side to side, but 4C is not statistically significant.

 

[xf1ref]

I let the front wheels spinning in the air today, 4th gear at idle, about 10 minutes. After this checked the discs and were starting to be hot..so this means that pistons are no retracting.
If everything is changed at calipers and the pistons can be pushed back very easy with a screwdriver maybe the issue is somewhere else. I'm thinking at brake pump or abs block.

 

[koalar]

I let the front wheels spinning in the air today, 4th gear at idle, about 10 minutes. After this checked the discs and were starting to be hot..so this means that pistons are no retracting.
If everything is changed at calipers and the pistons can be pushed back very easy with a screwdriver maybe the issue is somewhere else. I'm thinking at brake pump or abs block.

If they are only slightly warm for the first minute or so, they are at that monent in time fine

There's no side loads on the bearings moving the rotor slightly

There's no wind cooling effect

The pads are always in contact with the rotor, the pistons don't retract,

There is always some friction, so will build up of heat eventually

But they shouldn't instantly get to hot to touch

 

[vexorg]

Pads might not be free in the carrier

 

[Pugglt Auld Jock]

If they are only slightly warm for the first minute or so, they are at that monent in time fine

There's no side loads on the bearings moving the rotor slightly

There's no wind cooling effect

The pads are always in contact with the rotor, the pistons don't retract,

There is always some friction, so will build up of heat eventually

But they shouldn't instantly get to hot to touch

Pads mightn not be free in the carrier

With the wheel off the ground, if you can spin the wheel easily by hand then it's unlikely you've got a problem. As said above, there's no return springs etc with a brake caliper - although distortion in the piston seals due to the pressure of the fluid when applied, can give a small retracting effect as the seals return to their dormant state when the pedal is released. The effect is minimal though.

With front wheels particularly, you'll never get them to spin completely freely because of the slight drag of the pads and the resistance from the transmission. By the way, less experienced folk frequently mention that their pads are "dragging" because they hear the rubbing noise. Because disc pads never retract completely you'll always get a rubbing noise from them so don't get too up tight trying to eliminate this. Our Panda, and even more so our Ibiza, if not used for a week or so in winter when it's damp so the discs get surface rust on them, sound horrendous for the first half mile or so! I've noticed the Ibiza, with it's very open spoked alloy wheel design rusts it's discs much more under these conditions than the Panda with it's steel wheels and hub caps giving much more protection from driving rain.

 

[bugsymike]

I let the front wheels spinning in the air today, 4th gear at idle, about 10 minutes. After this checked the discs and were starting to be hot..so this means that pistons are no retracting.
If everything is changed at calipers and the pistons can be pushed back very easy with a screwdriver maybe the issue is somewhere else. I'm thinking at brake pump or abs block.

If you suspect the brake pump or abs block, then the easy way to prove or disprove would be to feel the drag on the wheel and then open the bleed nipple on the caliper, which if diagnosis was correct wheel should then spin easier.
I have had cars with dragging /hot brakes caused by badly fitted brake light switch at pedal and even wiring hanging around top of pedal, this means the brake master cylinder cannot retract the last bit and eventually the brakes will bind on.
Usually this would affect all four wheels.
If you issue is only one or two wheels I would recheck the caliper are sliding freely and brake pistons are not sticking, also that the pads are free in their holders.
Re brake pistons if cylinder and piston good, with caliper away from the disc and someone very gently presses the brake pedal pushing the piston out a fraction, as they release the pedal you should see the action of the brake seals actually ease the piston back a tiny bit due to the design of the piston rubber seals.

 

[Pugglt Auld Jock]

If you suspect the brake pump or abs block, then the easy way to prove or disprove would be to feel the drag on the wheel and then open the bleed nipple on the caliper, which if diagnosis was correct wheel should then spin easier.
I have had cars with dragging /hot brakes caused by badly fitted brake light switch at pedal and even wiring hanging around top of pedal, this means the brake master cylinder cannot retract the last bit and eventually the brakes will bind on.
Usually this would affect all four wheels.
If you issue is only one or two wheels I would recheck the caliper are sliding freely and brake pistons are not sticking, also that the pads are free in their holders.
Re brake pistons if cylinder and piston good, with caliper away from the disc and someone very gently presses the brake pedal pushing the piston out a fraction, as they release the pedal you should see the action of the brake seals actually ease the piston back a tiny bit due to the design of the piston rubber seals.

Not very common, but if one wheel only don't discount a partially collapsed brake flex pipe. Not found very often, I've seen a couple in my whole carrer, but can be very difficult to diagnose as the outside of the hose looked fine in both the one's I found. The inner liner was damaged though and not allowing the fluid to go back although the greater pressure of application was allowing fluid to go to the caliper. As you suggest I found it by slackening the bleed nipple, although it did take a while for the penny to drop that it was the flex hose itself at fault.

 

[xf1ref]

Not very common, but if one wheel only don't discount a partially collapsed brake flex pipe. Not found very often, I've seen a couple in my whole carrer, but can be very difficult to diagnose as the outside of the hose looked fine in both the one's I found. The inner liner was damaged though and not allowing the fluid to go back although the greater pressure of application was allowing fluid to go to the caliper. As you suggest I found it by slackening the bleed nipple, although it did take a while for the penny to drop that it was the flex hose itself at fault.

Everything is new on the caliper side like sliders, flex pipe, etc.. only the metal body and the piston are original.

 

[vexorg]

There are limited things that can cause it, sticking pads, sticking guides, sticking piston, fault with hydraulics.]
There are ways to check, pads are easy, you know from the feel of force needed to get them out and in, and you can move the wheel after you lift the caliper off to see if they are binding or not.,, then take pads out and feel the guides, and so on.

And binding can be felt just by trying to move the disc or when it stops, you can feel the force needed to get it moving.

 

[xf1ref]

The pads can be easily removed, piston can be pushed with a flathead, guides are new and very easy to slide but even so a slightly binding can be felt. Compared to other cars it feels like the pads are pressing on the disc. Is not a strong binding but it makes the discs hot to be touched by hand after 10 minutes spining in the air without touching the brake.

 

[koalar]

How hot after a couple of minuites you have a infred thermometer

Looks as exoected in the video

You are also turng a drive shaft running inside a oils seals , two joints, a large gear inside the gearbox that's half submerged in thick oil, a few other bits in the gearbox and the pads touching the discs

The front wheels never rotate freely, Regardles of the which gear it's in or if one or both wheels are on the ground

The pistons and pads do not retract by themselves

The plenty of rubbish and youtube video showing they do and some nice 3D animations, showing how it works in theroy,. But the pistons are held firmly by the O ring and the pressure behind it is held by the rear wheel cylinders pistons retracting,

In real use its not a problem, The discs expand as they get hot as you brake, as soon as you move off the discs contract again as they are air cools them leaving a small gap

The wheel bearings aren't perfect as you turn it's moves the discs a few thousands of an inch making some clearence

Rear brakes are fully locked a 3 clicks of the handbrake

 

[koalar]

And as it happens I just taken a caliper off a suzuki alto

A front wheel drive car wheels never spin freely like a bicycle wheel

I don't know why I keep reading that it should clearly the car in the video above has no brake even connected

 

[AnthonyH]

The other posters think this is normal. As do I.

Why don't you drive it and see what happens?

 

[vexorg]

I'm not sure i think it's normal, getting hot if just free running with wheels in the air.

 

[koalar]

I'm not sure i think it's normal, getting hot if just free running with wheels in the air.

Whether the original poster has a problem or not I can not say,

All we can to go on is

A video of a wheel spinning normally
No smell
No brake dust
No wear
Normal temperature and both sides the same after city driving

I have run a car up to 70 mph on axle stands and it's fine

But I have never run a car for 10 minuites without any airflow, I will not be wasting 10 minutes of petrol to testing.