Changing rear calipers!

[adam928]

I'm considering updating my rear calipers on my 1983 928 to the brembo ones from an s4. One of mine has seized.

Does anyone know what else I would need to do the conversion, apart from the calipers themselves?

Thanks in advance-adam

[harborman]

Considering the rear brakes do about 25% of the stopping why not just put standard replacement rears on.

[adam928]

I've been offered a pair of s4 ones at a good price, so was seeing what sort of a job it was to use them!

[jheis]

You'll need small spacers to center the calipers over the rotors. I used four grade 8 flat washers when I did mine (don't remember the size, but it wasn't anything out of the ordinary).

And, of course, you'll need the correct brake hoses.

Don't know what brakes you have on the front, but I've got a pair of "S" brakes (if you don't already have them) that would probably "balance out" the front and rears. See my Garage Sale post below. Depending on where you are, though, shipping may be a ***** - they're fairly heavy.

James

[adam928]

Originally Posted by jheis

You'll need small spacers to center the calipers over the rotors. I used four grade 8 flat washers when I did mine (don't remember the size, but it wasn't anything out of the ordinary).

And, of course, you'll need the correct brake hoses.

Don't know what brakes you have on the front, but I've got a pair of "S" brakes (if you don't already have them) that would probably "balance out" the front and rears. See my Garage Sale post below. Depending on where you are, though, shipping may be a ***** - they're fairly heavy.

James

Thanks for the info James!

I have the s brakes up front, but may even go with the s4 conversion down the line!

At least the rears seem a simple swap over, so may as well go with them!

Thanks again, Adam!

[adam928]

Take it, just the s4 standard brake pipes will do the job?!

[MPDano]

Originally Posted by jheis

You'll need small spacers to center the calipers over the rotors. I used four grade 8 flat washers when I did mine (don't remember the size, but it wasn't anything out of the ordinary).

And, of course, you'll need the correct brake hoses.

Don't know what brakes you have on the front, but I've got a pair of "S" brakes (if you don't already have them) that would probably "balance out" the front and rears. See my Garage Sale post below. Depending on where you are, though, shipping may be a ***** - they're fairly heavy.

James

Same rotors?

[jheis]

Yes, S4 brake hoses. And yes, same rotors.

James

[MPDano]

Originally Posted by jheis

Yes, S4 brake hoses. And yes, same rotors.

James

Interesting as the S4 Brembo swap on an OB "Fronts" require different Rotors. My 83 S on the other hand stop very well compared to my 81 Euro.

[jheis]

I don't think I replaced the rear rotors when I did the swap on my car, but I did it over 10 years ago, so my recollection may be wrong.

Along with different rotors, the front S4 Brembo swap also requires the whole S4 front suspension: upper A-arms, lower control arms, steering knuckle, tie rods, sway bar, etc. The whole geometry is different.

James

[adam928]

Thanks James,

The rotors listed on parts sites seem to all be the same up until 95, so that ties in!

Thought the front may be a bit more involved, but didn't realise it was that involved! Thought it would be the hubs and Rota's but not the whole suspension set-up!


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[MPDano]

The kit I have for my 81 Euro is:

1) S4 Brembo Calipers
2) 997 Rotors <-- I think this was the model
3) S4 Braided lines
4) Special made overpriced adapters/mounting bolts
5) S4 Brake Pads

I still haven't installed it all, it's been in boxes for about 4 years now. Someday I will get to it.

[jheis]

Originally Posted by MPDano

The kit I have for my 81 Euro is:

1) S4 Brembo Calipers
2) 997 Rotors <-- I think this was the model
3) S4 Braided lines
4) Special made overpriced adapters/mounting bolts
5) S4 Brake Pads

I still haven't installed it all, it's been in boxes for about 4 years now. Someday I will get to it.

That is the other alternative.

You can "back date" to the earlier (apparently up to '81) front suspension and use the adapters or "up date" to the S4 - which requires all the S4 goodies off of a donor car.

James

[MPDano]

Originally Posted by jheis

That is the other alternative.

You can "back date" to the earlier (apparently up to '81) front suspension and use the adapters or "up date" to the S4 - which requires all the S4 goodies off of a donor car.

James

Probably 82 as well. 83 is the first S as I have one.

[jheis]

Originally Posted by MPDano

Probably 82 as well. 83 is the first S as I have one.

Don't know.

My '82 has the "Competition Package" which had everything (except the 4.7ltr engine) that the Euro "S" had including the "S" brakes - so different from the "up to '81" USA set up.

James

[adam928]

Originally Posted by jheis

I don't think I replaced the rear rotors when I did the swap on my car, but I did it over 10 years ago, so my recollection may be wrong.

Along with different rotors, the front S4 Brembo swap also requires the whole S4 front suspension: upper A-arms, lower control arms, steering knuckle, tie rods, sway bar, etc. The whole geometry is different.

James

Does that include the shocks and springs too, to be swopped over, or can the originals remain!

[jheis]

Not sure...

My '82 had the non-adjustable ride height Bilsteins on the front. One shock went bad, so I replaced them with adjustable ride height Bilsteins which - with the stock springs - jacked up my ride height - even when adjusted the whole way down - so I installed a pair of Weltmeister S4 springs.

All this was before I converted to the full S4 set-up, so I was already running front S4 springs and shocks. Ultimately, I ended up with a set of Eibach progressive springs from 928 Int.

If your car has height adjustable shocks on the front, you're probably good to go.

James

[Pete R]

I don't know If I'd run the S4 rears without the corresponding fronts. This will change your brake bias. How much I don't know. You could be in a situation where you locking the rears making it very hard to control especially in turns.

[jheis]

Originally Posted by Pete R

I don't know If I'd run the S4 rears without the corresponding fronts. This will change your brake bias. How much I don't know. You could be in a situation where you locking the rears making it very hard to control especially in turns.

True, but you can encounter this just with miss-matched brake pads front to rear.

I was running Ferodo "Premier" pads all around. When I needed a new set of front pads, my local parts guru recommended PBR "Deluxe Ceramic" pads. At an autocross, one of my buddies told me that I was locking the rear brakes before the fronts. On the street, it sometimes seemed like I was just going to roll through the intersection. With the PBRs it felt like I'd lost about half of my front braking "bite" compared to the Ferodos.

Dumped the almost new PBRs and got a new set of Ferodos and all was good again.

James

[Pete R]

Originally Posted by jheis

True, but you can encounter this just with miss-matched brake pads front to rear.

I was running Ferodo "Premier" pads all around. When I needed a new set of front pads, my local parts guru recommended PBR "Deluxe Ceramic" pads. At an autocross, one of my buddies told me that I was locking the rear brakes before the fronts. On the street, it sometimes seemed like I was just going to roll through the intersection. With the PBRs it felt like I'd lost about half of my front braking "bite" compared to the Ferodos.

Dumped the almost new PBRs and got a new set of Ferodos and all was good again.

James

Yeah, It's not as drastic, you still have the relative ratio with the stock stuff. The S4 caliper has much more volume and will create much more brake force given the same input pressure. The other side is that the rears may not even work at all if the fronts grab before the master has sent enough volume. I don't know the math on the set up.