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Brake discs...DIY noob?

Robertb

Well-known member
Joined
1 Sep 2003
Messages
8,406
I've bought some rear brake discs for my 996 4S, and fancy giving DIY fitting a go. I am not an experienced mechanic. Is it reasonably straightforward? I've watched the obligatory YouTube vids, it looks OK.

My concerns are...
-levering the pistons apart; can I cause damage doing this?
-that the screws holding the discs on will be seized

Anything else that can/will go wrong? Any tips?

Rather than taking off the caliper initially, can I have a go at the disc screws first, and if they are seized quietly put the wheel back on and take it to the indy?

Brake pads were changed not too long ago, so the pins etc should come apart OK.
 
When I did mine the hardest part was getting the pad retaining pin out as it corrodes itself in place, spent a lot of time knocking it back and forth and rubbing it with emery cloth/wd40 in between.

The rest was fairly simple including undoing the disc retaining screw although I used an impact driver.

Pushing the pads back is ok just remember to unscrew the fluid reservoir and don't have the handbrake on.
 
mr_stevo said:
Pushing the pads back is ok just remember to unscrew the fluid reservoir and don't have the handbrake on.

Or better still open the bleed nipple, just in case the fluid over spills the reservoir.

Assuming the pistons just push back in as opposed to screw then you can use a large G clamp to do it.

In addition to the retaining screws that can be a pig, the caliper bolts can also seize. Give them a coating of penetrating fluid beforehand to make it easier.

If you have good access then you can normally get enough leverage to move them, but if you are restricted to working on the deck then it's not quite as easy.

Good luck :thumb:
 
Should be pretty straightforward - just make sure the crosshead screwdriver is a good fit in the retaining screws. A quick squirt of WD40 should help and I generally give the screwdriver a quick tap before attempting to undo the screws (works best if the screwdriver has a shaft that goes all the way through the handle, otherwise don't go too hard in case the handle cracks). If the screwdriver has a square shaft or a hex profile near the handle then get a spanner on it to do the turning as this allows you to really lean into the handle to maximise grip on the screw head. (Obviously impact driver is great if you have one but don't think I have ever needed to use mine in years of old classic car disc changes - gets used for other stubborn stuff though)
Cheers.Ian
 
Did this on Sat. Fairly straightforward but yes try get the screws out first and most liklely will need an impact driver.

Big allen socket to get caliper bolts out, think its 12mm.

Then caliper pin removal, as said potentially the worst bit.
 
Not sure what you are using to knock out the pins but it really worth getting a Pin Punch (or set of them). Use the correct diameter punch and decent hammer (lump hammer?) and the pins should some out ok, even if they're old and corroded.

Put a light smear of copper grease on when replacing but not too much near the brakes!

If the pads don't push back easily they may just be sticking in the caliper but check the pistons are retracting freely, if not, get the calipers refurbished before they seize.
 
Good luck, Rob. I did all 4 corners on the R32 without too much fuss. Have tins of brake cleaner, wire brushes to clean up as you go in order to maintain/improve the mechanics of the systems.

This stuff was very useful and I had no brake squeak after:

https://www.ebay.co.uk/i/261882004462

Do the Porkie calipers have some anti squeal shims or such like?
 
My tips:

Try the disc retaining screw first.

Use a well fitting screwdriver.

As said smack it with a hammer a few times to loosen the corrosion before turning the screw.

Worst case: you drill the head off the screw and then unwind it with mole grips when the disc is off. Stainless replacements are on ebay.

The brake pad retaining pins: Go easy on them. If you use a punch and a hammer, then don't smack too hard. You can break the alloy caliper.

Instead, use mole grips to rotate the pin, use an old chisel to scrape the pin then turn a bit and keep going till you've scraped all around. Work it backwards and forwards and use some release oil.

WD40 is next to useless for penetrating corroded / stuck bolts yet it is always recommended for some reason on forums. Use Plus Gas instead: https://www.carparts4less.co.uk/cp4l/p/-/-/-/-/?549774741

I used a wire brush in a grinder to clean up the pin before putting back, a spray of zinc paint or similar will stop it rusting up again for a while. Or you can buy a new pin kit for about £50 front axle £25 rear.
 
wasz said:
WD40 is next to useless for penetrating corroded / stuck bolts yet it is always recommended for some reason on forums. Use Plus Gas instead: https://www.carparts4less.co.uk/cp4l/p/-/-/-/-/?549774741

Completely agree with Wasz

I'd say it's worse than useless, it's dangerous because it is a spray and it will get into places you don't want it on brakes.

Plus gas in the old fashioned 'dripper' type tin rather than a spray if you can get it, if not, be careful where it goes.
 
maldren said:
wasz said:
WD40 is next to useless for penetrating corroded / stuck bolts yet it is always recommended for some reason on forums. Use Plus Gas instead: https://www.carparts4less.co.uk/cp4l/p/-/-/-/-/?549774741

Completely agree with Wasz

I'd say it's worse than useless, it's dangerous because it is a spray and it will get into places you don't want it on brakes.

Plus gas in the old fashioned 'dripper' type tin rather than a spray if you can get it, if not, be careful where it goes.

agreed! doesn't matter so much if you are changing discs AND pads, but otherwise you don't want oil on either.....
 
Great suggestions and tips everyone, thank you! keep em coming...

I'll get some brake cleaner and Plus Gas.

I'm hoping the pins will be OK as the pads were changed not too long ago.
 
Clean everything first.
Take your time and have a plan.
YouTube can be really good.
Take a few photos on your phone to make sure all goes back together, incase you get brain fade. (easy on jobs you have not done before)
Use a correct size pin punch ( if it is to small it will either go on the piss and you will slip off it as you hit it or break)
decent quality tools that fit well on the fixings.
Clean and lube everything as you reassemble it.
Check everything.
Clean discs with a good cleaner.
Use a torque wrench on wheel nuts.
And enjoy it :)
Don't touch anything in the house or your partner / housemate will kill you for black hand marks EVERYWHERE !! :wink:
 
I did all 4 corners on my 996T about a year ago (same brakes?).
I wouldn't have managed it without an impact driver for the brake disc screws, they are quite cheap nowadays, and I think it's a no brainer.
I'd also buy a pad spreader. Less essential but again, cheap, and less chance of scoring pads or calliper paint.
For the pins, agree with all of the above re sanding off lumpy corrosion before trying to drive out. I started mine with a proper punch but only got it so far because the punch tip was tapered and got too thick to pass through the hole in the calliper. Hacksawed the tip off a 4 inch nail and used that to finish the job.
If you are changing the pads too, the OPCs replace the spring/pin/wear sensor and pad backing plates/anti squeal shims (which stick to the backs of the pads).
 

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