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Rear brake caliper refurbishment
http://gt4dc.co.uk/forum/viewtopic.php?f=2&t=5673		 Page 1 of 2
Author:  Sirius [ Mon Jun 04, 2012 11:42 am ]
Post subject:  Rear brake caliper refurbishment
Hi folks,

I'm refurbing my rear calipers at the moment.

I was wondering if it is possible to buy new bolts that hold the caliper together. On one side the bolts are damaged from bashing the pins trying to get them out. I had to disassemble the caliper to remove the pins. I was able to get these caliper bolts undone but I don't really fancy reusing them as the heads are not hex anymore.

On the other side I managed to get the pins out without taking the caliper apart and it looks like there is enough space to get the pistons out without having it apart.

Does anyone know what torque the caliper bolts get done up to?

Cheers,

Mike
Author:  jgtcracer [ Mon Jun 04, 2012 3:04 pm ]
Post subject: 
im sure that you will be able to new ones, are they specialist bolts for the calipers? Are you on about the ones that screw into the sliding pin into the carrier? Sorry I cant be more help :D
Author:  two_OH_five [ Mon Jun 04, 2012 4:22 pm ]
Post subject: 
http://wiki.gt4dc.co.uk/index.php?title ... er_rebuild

I think you'll just have to try the parts counter for bolts. I know they were keen to sell me new calipers when I rebuilt mine so it's possible that individual spares aren't available. You might have to resort to either a set of scrap donor calipers or your local bolt supplier

Torque figure - I don't know but you won't go far wrong following the generic BGB figures assuming the existing boltshave numbers on the heads. Failing that just do them up "about right" :lol:

**edit**
Just looked at my own pictures, no sign of any markings on the bolts and there's no information in the BGB. "About Right" it will have to be!
Author:  Sirius [ Mon Jun 04, 2012 5:11 pm ]
Post subject: 
Thanks folks. At least I now know that I don't need to disassemble the other caliper to fit the new dust seals.

I'll try Toyota next week for the bolts.
Author:  Sirius [ Tue Jun 05, 2012 11:49 am ]
Post subject: 
I've managed to get the pistons out of the remaining caliper, one was fine but the dust seal had a slight tear in the other which has led to a bit of water ingress and hence a trashed piston.

Fortunately the damage is not too bad and it has not damaged the caliper.

Any suggestions on the best place to get a new piston?

Also looking at the caliper bolts they are and M8 bolt with a 12 mm head this is good news as standard M8 bolts only have a 13mm head so I am hopeful on being able to source a replacement from the local bolt shop.
Author:  Sirius [ Wed Jun 06, 2012 4:13 pm ]
Post subject: 
Update on this, I've ordered a new piston for the princely sum of £18.

Also it looks like you can order the caliper bolts separately they are about £2 each. We shall see if its correct when they arrive.
Author:  Diceman [ Thu Jun 07, 2012 10:08 am ]
Post subject: 
Mike,
What are you actually doing to refurb the calipers?

When I did mine I swapped all seals & pistons. Even the best pistons had some minor marking on them.

Brakes international can supply individual pistons and a full kit of seals and clips. If you need any odds & sods let me know as I have some spares that Steve had left over from his caliper rebuild.

I will have a look at what I have got as I can't remember if I bought a complete set of front pistons as well.

If you are only replacing some of the pistons I can see why there is a large difference in cost between buying a refurbed caliper and refurbing yourself. Brakes international do refurbed front or rear calipers for £79 (plus £20 surcharge for your old caliper) (probably plus the VAT etc).

For the fronts as you have 4 pots plus a fitting kit it is almost the same price if you change all 4 pistons.

If you have part numbers for the bolts that would be handy for the list we have. The other item I was trying to find was the o ring seal that sits in the fluid join between each half of the caliper.

Now what I wasn't sure of when I did mine and may be a good point for discussion...

Minor pitting I assume can be sanded back but is the piston externally coated (chromed?) that means that the corrosion and sanding may make it more prone to future rusting?
Author:  Sirius [ Thu Jun 07, 2012 10:34 am ]
Post subject: 
Diceman wrote:
Mike,
What are you actually doing to refurb the calipers?

When I did mine I swapped all seals & pistons. Even the best pistons had some minor marking on them.

Brakes international can supply individual pistons and a full kit of seals and clips. If you need any odds & sods let me know as I have some spares that Steve had left over from his caliper rebuild.

I will have a look at what I have got as I can't remember if I bought a complete set of front pistons as well.

If you are only replacing some of the pistons I can see why there is a large difference in cost between buying a refurbed caliper and refurbing yourself. Brakes international do refurbed front or rear calipers for £79 (plus £20 surcharge for your old caliper) (probably plus the VAT etc).

For the fronts as you have 4 pots plus a fitting kit it is almost the same price if you change all 4 pistons.

If you have part numbers for the bolts that would be handy for the list we have. The other item I was trying to find was the o ring seal that sits in the fluid join between each half of the caliper.

Now what I wasn't sure of when I did mine and may be a good point for discussion...

Minor pitting I assume can be sanded back but is the piston externally coated (chromed?) that means that the corrosion and sanding may make it more prone to future rusting?


Thanks JP.

What I am doing is rebuilding the calipers. I have been following Steve's guide posted on the wiki.

Three of the four pistons have no marking at all on the base or sides of the piston the only corrosion being on the top of the piston which does not touch the cylinder.

The cost is therefore much cheaper than getting a rebuilt caliper.

One part that is not supplied in the kit from Toyota is as you say this little o-ring that sits between the two halves of the caliper.

From what I have read any damage to the sidewalls of the piston and it is scrap as sanding it back etc the failure will just reoccur. I am not sure if the pistons are coated but they are certainly very shiny.

When I do the fronts I will take the pistons out first to see their state, if too many are damaged then I will order whole refurbished calipers. :)
Author:  Diceman [ Thu Jun 07, 2012 12:30 pm ]
Post subject: 
You have been lucky with your pistons then but unlucky with the pins :-)

Your thoughts are in line with my thinking when I refurbed them. I pulled the pistons out before ordering anything and had only one piston I was considering putting back in so just replaced all 4 instead of 3!

I do remember back in the day seeing people sanding back any rust on the piston and popping them back in with new seals and hence the question. Erghh actually I think when my cars were disposable and my disposable income was small I may have done this on a couple of old Audi Coupes I owned :-)
Author:  two_OH_five [ Thu Jun 07, 2012 2:46 pm ]
Post subject: 
Pistons which are.damaged on the seal face are scrap and should not be reused unless professionally refinished with a complete new surface


Sanding the rust off is downright dangerous as you risk immediate non sealing and long term failure of the seal with potential complete brake failure. This could happen without warning when the piston moves out to a damaged seal area

This possibility should not ever be considered

Sorry JP not having a go but this is a public forum and we have to assume the lowest common denominator in audience common sense and understanding. Otherwise we'll inevitably get the "cleaned pistons with angle grinder, now parked in a wall" post
Author:  TrackToyFour [ Thu Jun 07, 2012 6:51 pm ]
Post subject: 
The pistons on Stormy Blue's front calipers were all corroded to varying degrees. They looked like they were chrome plated and even although the corrosion was on the outside of the piston it had started to get under the chrome which was 'lifting'. I reckoned they were on the way out so it only a question of 'when' not 'if'.
Author:  Diceman [ Thu Jun 07, 2012 10:02 pm ]
Post subject: 
Fair point steve and no offence taken slating my past botch :-)

To be fair I wasn't actually sure if the rust was far enough down the piston to actually sit inside the caliper (piston moves in farther when you fit new pads).

I suppose welding 2 cars together is frowned upon as well now ;-)
Author:  two_OH_five [ Thu Jun 07, 2012 10:28 pm ]
Post subject: 
Not round here. The Mondota will be a thing of beauty :lol:
Author:  niblettr [ Sat Jun 09, 2012 8:03 pm ]
Post subject: 
refurbed caliper, is that £79 per pair or each?
Author:  Sirius [ Sat Jun 09, 2012 9:54 pm ]
Post subject: 
Each. If it was a pair, this thread would not exist. :)
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