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Do i need to skim rotors?

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-S- Community Regular

-S-

Posted
Posted

Hi all,

 

Need advise. ..

 

Long story short , do i need to skim my rotors that have been lying on the grass/dirt for more than a year?

 

I've measured the thickness for both front and rear rotors and they have not thin out at all . Not even 1 mm :) obviously they're full of rust and dirt . I've removed the dirt but wondering if i should skim it to remove rust and also balance the rotors before fitting them? (Not even sure if people balance rotors or not)

 

I've attached 1 pic to pretty much show how It was kept under the weather lol...

20161202_180320.jpg

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https://www.sau.com.au/forums/topic/469195-do-i-need-to-skim-rotors/
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GTSBoy Grand Master

GTSBoy

Posted
Posted

You can give them a rub with abrasive paper to try to remove a lot of rust.  They will not have changed dimensions in a way that you can measure, so you shouldn't worry about that.  They only real problem with using paper to clean them is that you may make the surfaces not evenly flat whilst doing so.  But you'd have to rub pretty hard in one spot a lot longer than other spots to achieve it.

Oddly enough, it's not the friction surface you need to worry about the most.  If there is thick rust on the hub surface, you need to clean that up.

-S- Community Regular

-S-

Posted
  • Author
Posted
You can give them a rub with abrasive paper to try to remove a lot of rust.  They will not have changed dimensions in a way that you can measure, so you shouldn't worry about that.  They only real problem with using paper to clean them is that you may make the surfaces not evenly flat whilst doing so.  But you'd have to rub pretty hard in one spot a lot longer than other spots to achieve it.

Oddly enough, it's not the friction surface you need to worry about the most.  If there is thick rust on the hub surface, you need to clean that up.

 

Will it be easier if i send it to a workshop to skim it to remove rust? I don't mind saving some money to do it myself though but i need guidance...

 

Reason i ask about skimming rotors is because a friend told me i should get it skimmed & balanced as well... do people even balance rotors? ?? I mean the last thing i need is driving and feeling a lot of vibration/ shake. ..

 

GTSBoy Grand Master

GTSBoy

Posted
Posted

No, rotors do not get balanced.

My position is never get rotors machined unless they absolutely need it.  You lose material and life from them every time you do it.  The only time to do it is if there is a lip than needs to be gotten rid of, or grooves in the surface, or serious warpage.  Although serious warpage should probably prompt replacement.  The other reason people get rotors machined is when they think they have warped rotors but they actually have uneven build up of pad binder material on the rotor faces.  This can also be successfully fixed with abrasive paper.

If your surfaces are nice and flat and you don't have a lip on the outer edge, try paper first.

Lastly, I never get rotors machined off the car.  It's just so easy to get the mobile brake guy to come and do them on the car, whether at home or in a workshop.  So you may as well just clean them up yourself and see how they go before moving onto machining if you need to.  But it is important for you to realise that there are other reasons for you to get braking vibrations also.  It may not necessarily be that the rotors are not good.  So if you do put it all together and run it and find vibration, you'd be well advised to look at the other reasons.  At the least you can put a dial gauge onto the car and spin the rotors to see if they have a lot of runout other wierdness going on, and this can be done better on the actual hub and bearing that they are working on than a lathe anyway.

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V28VX37 Veteran

V28VX37

Posted
Posted
5 hours ago, GTSBoy said:

No, rotors do not get balanced.

...

Well, they do - at the manufacturer. One of the RDA's I installed recently had a nice straight 'slot' cut on the outer rim of the disc at one single spot, whilst the other rotor didn't - I am 99% certain it's to balance it. The pair was less $200 so pretty cheap compared to mucking around with rusted rotors.

Also re machining rotors on hubs, it's a good option but some guys only do plain ones, the one my shop uses wouldn't touch my slotted DBA's on the car.

When re/installing rotors make sure you check run out and oscillation: https://www.sau.com.au/forums/topic/448613-r34-gtt-brake-improvement-without-breaking-the-bank/?do=findComment&comment=7803377

As others have said you definitely want to check the condition of those calipers. Rebuilding them at a workshop will cost a bit (my GTT fronts rebuild was around $400 drive in/drive out), but brakes is one of those things that you need to be pretty confident in what you're doing to DIY.

Also: If that's what your rotors and suspension looks like, what the rest of the underbody like??

dbasteve Enthusiast

dbasteve

Posted
Posted

I guess you've harvested the potatoes already. :369_sweet_potato:

Hi Mate,

Please either re-machine those discs or get new ones (your pads will thank you), rebuild the calipers (seal kit), replace the studs and clean the rust off those hubs and inside the disc hat. You should then have a safe ride.

Cheers 

Duncan Grand Master

Duncan

Posted
Posted
6 hours ago, dbasteve said:

I guess you've harvested the potatoes already. :369_sweet_potato:

Hi Mate,

Please either re-machine those discs or get new ones (your pads will thank you), rebuild the calipers (seal kit), replace the studs and clean the rust off those hubs and inside the disc hat. You should then have a safe ride.

Cheers 

do what this man says, he knows.  and welcome back to the forums :)

dbasteve Enthusiast

dbasteve

Posted
Posted
10 hours ago, -S- said:

I'm doing all except the studs...

Studs are cheap and easy to replace. Those in the picture look like they have advanced corrosion and aren't safe. 

Assuming you can get some wheel nuts on don't leave it too long.

niZmO_Man Grand Master

niZmO_Man

Posted
Posted

After changing wheel studs three times because of "technicians" who can't put wheels back on my Subaru properly, yes they are cheap to change but quite a crucial part of keeping your car on the road.

https://partsouq.com/en/search/all?q=43222-28B00

-S- Community Regular

-S-

Posted
  • Author
Posted
Studs are cheap and easy to replace. Those in the picture look like they have advanced corrosion and aren't safe. 
Assuming you can get some wheel nuts on don't leave it too long.

I thought u meant the stud of the caliper. Lol. Yeah i guess I'll look into it. .. thanks
dbasteve Enthusiast

dbasteve

Posted
Posted
22 minutes ago, -S- said:


I thought u meant the stud of the caliper. Lol. Yeah i guess I'll look into it. .. thanks

No Worries and good luck.

Give everything a good ol soak in WD40 a day or more before. Take the pads out first. 

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