78 to 87 brake upgrade.
10-24-2009, 03:40 AM
#1
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78 to 87 brake upgrade.
Hello,
I have a friend that wants to buy a set of S4 brakes from me front and rear, and put on his ancient 928 from 1978.
I have a S4 parts car that we can steal from.
He wants to take his nice shark on the track next year, and badly needs better brakes!
But we are uncertain as to what parts are required.
Please advice.
I have been told that the upper A arms need to be included, but what else?
Cheers and thanks.
I have a friend that wants to buy a set of S4 brakes from me front and rear, and put on his ancient 928 from 1978.
I have a S4 parts car that we can steal from.
He wants to take his nice shark on the track next year, and badly needs better brakes!
But we are uncertain as to what parts are required.
Please advice.
I have been told that the upper A arms need to be included, but what else?
Cheers and thanks.
10-24-2009, 05:48 AM
#2
Rennlist Member
That really depends on what parts you have and what you want to put into it, and what you want the end result to be.
IIRC you can swap everything over. I believe that you can keep the early crossmember, but upper/lower A-arms and spindles have to be swapped over together if you want to be able to use standard S4 rotors.
I just did this conversion myself, and while I don't have a writeup posted yet I will within a couple of weeks. I did post some pictures of the finished install here though.
I took a different approach: Put the 993 rotors on the front(Same as S4 except they are cast-hole and have a different offset) and buy the adapter (~$200) to mount the calipers to the 78 spindles. This has the advantage of not needing an alignment. It won't work if you have the aluminum lower ball joint carriers, but if you have those they need to be replaced with the steel version ASAP anyway. You may run into clearance issues even with steel ball joint carriers if they are worn. Also, I think this places the caliper closer to the wheel so make sure you have clearance.
The rears are a no-brainer. The rotors are a simple swap and the calipers just need a 1-2mm spacer to line up properly. You will need S4 brake hoses all around.
If you want to run more camber in the front than you can get with the stock setup you can do the 993 rotor conversion as I described(leaving the 78 spindle and lower a-arms) and replace just the upper a-arms with the shorter S4 parts.
928 Specialists has all of the adapters and spacers, 928 International has just the adapters.
There may be other details to contend with along the way, like backing plates etc. but there's not much point getting into all of that until you pick a direction.
IIRC you can swap everything over. I believe that you can keep the early crossmember, but upper/lower A-arms and spindles have to be swapped over together if you want to be able to use standard S4 rotors.
I just did this conversion myself, and while I don't have a writeup posted yet I will within a couple of weeks. I did post some pictures of the finished install here though.
I took a different approach: Put the 993 rotors on the front(Same as S4 except they are cast-hole and have a different offset) and buy the adapter (~$200) to mount the calipers to the 78 spindles. This has the advantage of not needing an alignment. It won't work if you have the aluminum lower ball joint carriers, but if you have those they need to be replaced with the steel version ASAP anyway. You may run into clearance issues even with steel ball joint carriers if they are worn. Also, I think this places the caliper closer to the wheel so make sure you have clearance.
The rears are a no-brainer. The rotors are a simple swap and the calipers just need a 1-2mm spacer to line up properly. You will need S4 brake hoses all around.
If you want to run more camber in the front than you can get with the stock setup you can do the 993 rotor conversion as I described(leaving the 78 spindle and lower a-arms) and replace just the upper a-arms with the shorter S4 parts.
928 Specialists has all of the adapters and spacers, 928 International has just the adapters.
There may be other details to contend with along the way, like backing plates etc. but there's not much point getting into all of that until you pick a direction.
10-24-2009, 07:40 AM
#3
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Thx so much for your detailed response!
Very kind of you.
Basically I need to know what is the least amount of parts my friend needs to convert his 1978 5 speed brake system into S4 Brembo spec. Front and rear.
The rear I gather from your writing is simple.
But what does he need to install S4 calipers and discs in the front?
Cheers and thx again.
Michael
Very kind of you.
Basically I need to know what is the least amount of parts my friend needs to convert his 1978 5 speed brake system into S4 Brembo spec. Front and rear.
The rear I gather from your writing is simple.
But what does he need to install S4 calipers and discs in the front?
Cheers and thx again.
Michael
10-24-2009, 10:30 AM
#4
Man of many SIGs
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He just needs a set of caliper adapters and a set of 993 ( non turbo ) rotors. Here is a picture. All of the big three 928 vendors sell these items. The items shown and the picture were taken from www.928gt.com
10-24-2009, 01:55 PM
#6
Rennlist Member
Thx so much for your detailed response!
Very kind of you.
Basically I need to know what is the least amount of parts my friend needs to convert his 1978 5 speed brake system into S4 Brembo spec. Front and rear.
The rear I gather from your writing is simple.
But what does he need to install S4 calipers and discs in the front?
Cheers and thx again.
Michael
Very kind of you.
Basically I need to know what is the least amount of parts my friend needs to convert his 1978 5 speed brake system into S4 Brembo spec. Front and rear.
The rear I gather from your writing is simple.
But what does he need to install S4 calipers and discs in the front?
Cheers and thx again.
Michael
Are the S4 rotors in excellent condition, or are you motivated to stick with them for budget reasons? Are you motivated enough to change out the whole front suspension? If you do not have a compelling need to use S4 rotors then the 993 rotors fit without changing any suspension parts, assuming you have steel lower ball joint carriers on the 78. IMHO you should check that before making any decision. The S4 calipers then fit with the adapter on the front, thin spacers on the rear.He just needs a set of caliper adapters and a set of 993 ( non turbo ) rotors. Here is a picture. All of the big three 928 vendors sell these items. The items shown and the picture were taken from www.928gt.com
Left: 993 351 043 01
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10-24-2009, 02:19 PM
#9
Rennlist Member
So, to help clarify...the rears just bolt on but the fronts are more complicated. You have two choices up front:
-Use the adaptors with his existing front suspension. This route will require the 993 rotors as well.
-Change over the front suspension to the S4 stuff. I know you will need lower A arms, and spindles. Not sure about the upper A arms and shocks. This route will use the S4 rotors.
Personally, if it were me, I would go with the S4 route and change the whole front suspension as well as the brake booster (10" instead of 9") and master cylinder. Probably move over the rear shocks as well.
My reasoning is this:
-You have the S4 stuff. What else are you going to do with it?
-The adaptors and 993 rotors add up. If the S4 parts are less expensive he can put the extra money into some other race prep parts.
-If he is going to be racing it, he is going to want the strongest, best brakes and suspension he can get.
-There can be some sort of issue with the 993 rotor rubbing the lower ball joing or something.
On the other hand it is probably a lot more work to move the S4 stuff. Particularly with the engine in the car.
-Use the adaptors with his existing front suspension. This route will require the 993 rotors as well.
-Change over the front suspension to the S4 stuff. I know you will need lower A arms, and spindles. Not sure about the upper A arms and shocks. This route will use the S4 rotors.
Personally, if it were me, I would go with the S4 route and change the whole front suspension as well as the brake booster (10" instead of 9") and master cylinder. Probably move over the rear shocks as well.
My reasoning is this:
-You have the S4 stuff. What else are you going to do with it?
-The adaptors and 993 rotors add up. If the S4 parts are less expensive he can put the extra money into some other race prep parts.
-If he is going to be racing it, he is going to want the strongest, best brakes and suspension he can get.
-There can be some sort of issue with the 993 rotor rubbing the lower ball joing or something.
On the other hand it is probably a lot more work to move the S4 stuff. Particularly with the engine in the car.
10-24-2009, 02:44 PM
#10
Rennlist Member
In my case at least, a thin spacer(actually 2 per caliper) was needed on the rear to get the caliper properly centered over the rotor. It looks like it will work without that but getting the inner pad in will be very tight.
Upper a-arms must be swapped if S4 spindles will be used. The angle of the ball joint is different. You can get away with S4 upper arms on early spindles if more camber is desired(ask Jim Bailey) but I don't think it will work the other way around.
Putting the S4 MC in will require re-plumbing the brake system to do it right. '78 cars have equal-size pistons in the MC and are plumbed for a split-diagonal system. S4s have unequal-sized pistons in the MC, the larger rear piston(close to the booster) is plumbed to the front brakes, the smaller, floating piston in the front is plumbed to the rear brakes. Connecting this directly to a split-diagonal system will result in different pressures in each diagonal circuit. The larger booster may reduce brake feel somewhat, they may end up a bit too touchy for a non-ABS car but that is pure speculation on my part. My recommendation would be to go with the stock booster initially and only change if less pedal effort is desired. I happen to like the feel with the original booster, and can lock the wheels at any speed without too much effort.
The lower ball joint issue is the reason behind warning him about the aluminum ball joints(aside from the unpredictable failure tendency of the aluminum units), also worn ball joints reduce the clearance. The clearance issue means you may not be able to fit backing plates, as the ball joints push the backing plates into the rotors. I had to pull the backing plates off, will reinstall when I have time to cut a clearance hole for the balljoints and/or grind 1-2mm off of the balljoints.
but the fronts are more complicated. You have two choices up front:
-Use the adaptors with his existing front suspension. This route will require the 993 rotors as well.
-Change over the front suspension to the S4 stuff. I know you will need lower A arms, and spindles. Not sure about the upper A arms and shocks. This route will use the S4 rotors.
Personally, if it were me, I would go with the S4 route and change the whole front suspension as well as the brake booster (10" instead of 9") and master cylinder. Probably move over the rear shocks as well.
-Use the adaptors with his existing front suspension. This route will require the 993 rotors as well.
-Change over the front suspension to the S4 stuff. I know you will need lower A arms, and spindles. Not sure about the upper A arms and shocks. This route will use the S4 rotors.
Personally, if it were me, I would go with the S4 route and change the whole front suspension as well as the brake booster (10" instead of 9") and master cylinder. Probably move over the rear shocks as well.
Putting the S4 MC in will require re-plumbing the brake system to do it right. '78 cars have equal-size pistons in the MC and are plumbed for a split-diagonal system. S4s have unequal-sized pistons in the MC, the larger rear piston(close to the booster) is plumbed to the front brakes, the smaller, floating piston in the front is plumbed to the rear brakes. Connecting this directly to a split-diagonal system will result in different pressures in each diagonal circuit. The larger booster may reduce brake feel somewhat, they may end up a bit too touchy for a non-ABS car but that is pure speculation on my part. My recommendation would be to go with the stock booster initially and only change if less pedal effort is desired. I happen to like the feel with the original booster, and can lock the wheels at any speed without too much effort.
My reasoning is this:
-You have the S4 stuff. What else are you going to do with it?
-The adaptors and 993 rotors add up. If the S4 parts are less expensive he can put the extra money into some other race prep parts.
-If he is going to be racing it, he is going to want the strongest, best brakes and suspension he can get.
-There can be some sort of issue with the 993 rotor rubbing the lower ball joing or something.
On the other hand it is probably a lot more work to move the S4 stuff. Particularly with the engine in the car.
-You have the S4 stuff. What else are you going to do with it?
-The adaptors and 993 rotors add up. If the S4 parts are less expensive he can put the extra money into some other race prep parts.
-If he is going to be racing it, he is going to want the strongest, best brakes and suspension he can get.
-There can be some sort of issue with the 993 rotor rubbing the lower ball joing or something.
On the other hand it is probably a lot more work to move the S4 stuff. Particularly with the engine in the car.
10-24-2009, 03:20 PM
#11
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Karl!
Thats pretty clear.
Your reasoning is very good.
I think I will suggest that he buys the whole S4 front suspension then.
Makes more sense that sourcing new parts etc.
I love this community.
Its such a help and guide.
Its all pretty clear now.
Cheers and thx to all!
Thats pretty clear.
Your reasoning is very good.
I think I will suggest that he buys the whole S4 front suspension then.
Makes more sense that sourcing new parts etc.
I love this community.
Its such a help and guide.
Its all pretty clear now.
Cheers and thx to all!
10-24-2009, 06:25 PM
#13
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Dave When you removed your backing plates how did you treat the nuts that are welded to the backing plate and hold the caliper in place? Did you just go to nuts and washers to hold the adapter bolts to the spindle ? Great write ups and photos very helpfull Keep up the good work!
10-24-2009, 06:54 PM
#14
Rennlist Member
Dave When you removed your backing plates how did you treat the nuts that are welded to the backing plate and hold the caliper in place? Did you just go to nuts and washers to hold the adapter bolts to the spindle ? Great write ups and photos very helpfull Keep up the good work!