[XinZhao]

In the book it says dot3 or dot4 but in the shop they told me dot 5.1 is the fliud to use in modern cars with ABS. I bought some dot 4, will soon change it for the 1st time by myself.
Btw. To express problems I have had since the car was new: (now its at 130 k km)
- at about 95k handbrake was stuck and the LR break inside burnt all the way.

- at about 120 k km LR break got stuck (one of the guiding pins) and it burned off one side of the inner pad.

- now - about 130k km - changed by myself the front pads because i have had random strange noises when turning the wheel and it got worse and worse - at the latest stage I heard hard grumbling noises when breaking.

I didn't suspect the break pads because the outer part had plenty of meat on it. When I changed it, the inner part was completely gone, the iron of the inner pad was breaking and destroying the disk.
With new pads I didn't get the small metallic pad-holders. I tried with the old ones, cleaned them somewhat, but the pads were too tight, so I now have pads without the those thin metal holders. Only downside as I see it is that the pads make some noise on a bumpy road or on a touch of a break pedal.

I wonder how long would've the original pads last if they were wearing evenly

[Phil №❶]

The disc brakes are supposed to wear each pad evenly by virtue of the fact that each pad equally forms the opposing side of the applied braking force. (I can't think of another way to describe it   )  It sounds to me that your calipers are jammed with crud and are unable to perform properly. I'd be getting them checked ASAP as the end result could no braking at all from that caliper.

[diablo]

 

Only times I've had problems of uneven wear on brake pads is when the pistons have partially or fully seized, though that was on oldish cars and about 25 years ago when I did my own servicing.

I'd force them out somehow (I forget) and clean them and the barrel before fitting new pads.

The car seems a bit new to have such problems, but I doubt if it is the brake fluid causing it.

[sundiz]

Correct if I am wrong, but I've heard that you could mix dot 3, 4 and 5.1. Therefore dot 4 would be ok. Biggest differences are in the boiling points of the liquid. I have used dot 4 and it works well. Dot 5 is a different and that can not mixed with the others. I think that is mostly used in race cars.

[Surferdude]

Found this which expands on sundiz point.

Since DOT 4 and 5.1 are both glycol-based brake fluids they are compatible with each other, which means they can be readily mixed without harming your brake system. It is important never to mistake DOT 5.1 (glycol-based) with DOT 5 which is silicone-based and should never be mixed with any other DOT fluid.

[XinZhao]

When was the 5.1 put on the market? Why isn't there an  5.1 mentioned in the manual of the car?
I cleaned the pin guids, although they were fine - except one of them is not perfectly round anymore.
So what is the part number for the guide pins?
Also, I was surprised that the pins aren't the same, top pin is different from the bottom one.

I think 5.1 is also more fluidly and therefore less susceptible for clogging. But the down side is that absorbs more water.

What do you use for lubricating the guide pins? I can't find, here were I live, silicon grease.

I don't know why I have so much problems with seized guide pins.
Can the reason have something to do with snow-salty roads during winter?

[Surferdude]

TBH I reckon your issue is more in the calipers than the external slides.
With this sort of problem I'd be overhauling ALL the hydraulics although the master cylinder might be OK.
As for the slide pin lubrication, you should be able to buy some high temperature lubricant specifically for this purpose.
I'd also be getting pads which come with matched anti rattle plates.

[sundiz]

What do you use for lubricating the guide pins? I can't find, here were I live, silicon grease.

I've used copper grease and brake grease. I don't know whats in it but it is sold for especially for that use. I think brake grease would be ideal for that use.

[Asterix]

I also use copper grease, which caused someone here to accuse me of being old fashioned.... 

Well it worked fine when I was an apprentice 25 years ago.... 

What worries me is that @XinZhao didn't change the rotors when the pads was worn down to the metal...   If there's salt on the roads you should disassemble and grease up the brakes every spring.

[XinZhao]

Yes, I am still undecided about changing rotors yet. I think the FrontLeft one is about 0.3 mm under limit and the other ones are few 0.x in limit.
I also used Copper grease as antiseiz o n the back and sides of the pads.
How you clean the guiding pins?
I used break cleaner but maybe mistake as it is very aggressive on the gum-covers..

[Paolo5]

Besides the wear limit factor, the rotors need to be running 'true'....do they need to be machined?

[Asterix]

Besides the wear limit factor, the rotors need to be running 'true'....do they need to be machined?

The fact that one rotor is 0,3 under minimum thickness makes machining pointless. New rotors, never compromise on safety with brakes.

[XinZhao]

I know but also I presume the limits are "full speed proof", so I guess if I never go above 130, no harm is done by not changing them.
Anyway, I know, I should probably change them, especially because I have a kid, but they are expensive and...
 I rarely go above 100km/h.
I soon have "technical inspection" so I'll see how the breaks are, and will I pass or not.

[Surferdude]

Brakes work harder in suburban areas where there are more applications,  more often. Overheating could well result in a cracked rotor and complete brake failure.
Top speed has nothing to do with it.

[Asterix]

If you value your kid, you'll change the rotors. They're not expensive if you don't buy them at Hyundai 

[Phil №❶]

I know but also I presume the limits are "full speed proof", so I guess if I never go above 130, no harm is done by not changing them.
Anyway, I know, I should probably change them, especially because I have a kid, but they are expensive and...
 I rarely go above 100km/h.
I soon have "technical inspection" so I'll see how the breaks are, and will I pass or not.

Price should not be a factor in this case. In Oz, if you have a smash, your car will be inspected by the police and any faulty parts will enable your insurer to evade their responsibility, possibly to all parties involved. It is your responsibility to ensure the car is roadworthy. As well, personal liability or legal damages through death  could be compromised. As you have a child and even your own life must be worth 2 rotors, surely.

Sorry to sound narky, but avoiding trouble is a much better solution

[XinZhao]

I understand but I can't see what could go wrong with the disks.
As I never do sport driving. So, no excess heat. Emergency hard breaking, I don't see how can go wrong.
I will still make a decision, but if I change, I will change all 4 rotors.
How I regularly break/drive you can see by me having the original pads for 130 k km. They would still be fine if there was no pin guide stuck.
I'll make a decision after technical inspection which is mandatory at my country every year before insurance payment. That's for me in about 2-3 weeks.
Thanks for the info, though.