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Richy's 1991 Porsche 944 S2 - BEWARE OF SHARN.


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On 7/22/2018 at 03:50, V8Pete said:

 

The same happens with the Vitesse. Almost everything dwarfs it but it's meant to be a "large" car. They just don't make cars like they used to, with all their fancy life saving rubbish now. 

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Seems to be running pretty well now, hot starts haven't been a problem again (yet) and it goes well. Have given it a couple of good hidings through some twisties, and now that I'm finally getting to learn about the car it's becoming more and more fun to hoon.

So I went to Caffeine & Classics this morning, then decided I'd pull it apart. Again. This time around, a brake refresh.

So first things first, acquire parts. Sterling Brake and Clutch sorted me with a set of fresh Zimmerman rotors, these are 298mm front and 300mm rear. Always a great price and the best service ever from Blair there, support the hell out of them. Great at finding stuff that no one else seems to be able to find.

30407870838_6217142ee8_h.jpg1991 Porsche 944 S2-488 by Richard Opie, on Flickr

30407870168_1763033436_h.jpg1991 Porsche 944 S2-492 by Richard Opie, on Flickr

I also bought a full set of caliper seals and dust boots, as I had some concerns the front calipers were sticking and causing uneven pad wear. Anyway more on that later. So I chucked al my gear in the boot, gathered up my tools and set off to George's place to chuck the car on his hoist and crack into it.

42466895610_51005d9b3b_h.jpg1991 Porsche 944 S2-498 by Richard Opie, on Flickr

First up, here's a look at the calipers. Rears, grubby. Sort of underslung Brembo 4-pots. Handbrake is one of those internal drum kind.

30407869578_1dd0c72f1c_h.jpg1991 Porsche 944 S2-500 by Richard Opie, on Flickr

42466895290_ef8077b423_h.jpg1991 Porsche 944 S2-510 by Richard Opie, on Flickr

Fronts, a Brembo 4-pot again. In this case I've got a bit of a problem with the clear coat going cloudy on both front calipers.

42466895180_911ec33ddd_h.jpg1991 Porsche 944 S2-513 by Richard Opie, on Flickr

42466894890_5bb1854f9d_h.jpg1991 Porsche 944 S2-521 by Richard Opie, on Flickr

Fairly straightforward to remove really. Release the spring clip on the top, remove the wear sensor and pull pads out after pushing the pistons back. I was a bit agricultural and used a pair of polygrips to squeeze them back, as the plan is to refinish the calipers anyway. Front hubs look pretty boring, just an aluminium casting with a toothed ring on them for the ABS sensor. Rears are a bit more interesting, with the whole handbrake thing going on.

30407868318_40f33c0ebd_h.jpg1991 Porsche 944 S2-526 by Richard Opie, on Flickr

Some positives here. Studs are 55mm long (end to end) and I want to install some that are 10mm longer to accommodate some spacers before I eventually throw the 17" wheels on. Plenty of space behind the hub to install these without pulling the axles and making a massive job of it. Yay!

Anyway, the calipers. Once I got them off, I thought I'd have a crack at squeezing the pistons in. They all moved fluidly in, and all the dust seals are in great condition. So I'm likely going to leave them be and not throw new seals at them... instead I'll clean and mask off that internal area before painting and it should all go to plan. A friend just drew up new decals for me too.

30407867928_c670490717_h.jpg1991 Porsche 944 S2-546 by Richard Opie, on Flickr

They might all look the same.... but here's the crucial difference between front and rear.

Front - staggered pistons, with a 40mm and 36mm piston combo.

30407866358_73763e4a50_h.jpg1991 Porsche 944 S2-559 by Richard Opie, on Flickr

Rear, staggered again but a 30mm and 28mm arrangement.

42466893850_e1a44daced_h.jpg1991 Porsche 944 S2-555 by Richard Opie, on Flickr

Any tips on what to do when it comes to bleeding will be appreciated, I have never pissed around with a 4-piston caliper before with a bleed nipple on either side of the caliper. I'm guessing you just do it one at a time, but inside or outside first?

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Wilwood calipers have bore sizes that increase in size from front to rear. This allows a pressure differential between the leading and trailing edge of the caliper, thus providing a more even wear pattern along the entire length of the brake pad, hence it controls pad taper. This is necessary because incandescent material and debris from the leading edge of the pad is trapped between the pad and rotor; it tends to float the trailing edge of the pad off the rotor. A larger piston at the trailing edge of the pad provides more pressure to compensate for this debris buildup and keep the pad flat against the rotor.
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10 hours ago, KKtrips said:

Always start with the furtherest away from the master cylinder. Callipers with dual bleed nipples, whatever is further away from the brake hose inlet.

Its not crazy like the AP calipers on a Vitesse, where both bleed nipples on each caliper need to be bled at the same time?

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36 minutes ago, kws said:

Its not crazy like the AP calipers on a Vitesse, where both bleed nipples on each caliper need to be bled at the same time?

How does that even work, would the fluid just not take the shortest path to the nearest bleeder every time?

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6 hours ago, sheepers said:

your trying to apply logical thinking to something british. 

it doesn't make and sense.

or work.

It did work, somehow. You bleed the two together, and then you bleed the third one afterwards. Three nipples, and not even the good kind.

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