968 calipers on an 86 951
10-25-2001, 10:23 AM
#1
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968 calipers on an 86 951
Hi:
I just wanted to make sure that calipers from a non-M030 968 would fit my 86 951. Will there be wheel clearance problems? Any issues I should watch out for? Anybody tried it?
Thanks,
S
I just wanted to make sure that calipers from a non-M030 968 would fit my 86 951. Will there be wheel clearance problems? Any issues I should watch out for? Anybody tried it?
Thanks,
S
10-25-2001, 11:48 PM
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I posted a reply to this earlier, but it didn't come up for some reason. I had said the same thing about the calipers being the same though.
If you are planning to replace the front's, you could do much better upgrading to some Turbo S (928 S4) calipers, OR, if you have 17" rims, the best (cheapest) way to go would be Big Red's (about $600/pair- new)- then you could mount your stock front calipers to the rear, and, you could have larger front rotors (12 3/4" - 13"). The standard Big red rotors are cheaper than the Turbo S rotors, and, being larger, give more leverage- unfortuantely, they also weigh more, but it all depends on what you have, and what you want to accomplish- oh, and how much $$$ you have
Good Luck,
Robby
If you are planning to replace the front's, you could do much better upgrading to some Turbo S (928 S4) calipers, OR, if you have 17" rims, the best (cheapest) way to go would be Big Red's (about $600/pair- new)- then you could mount your stock front calipers to the rear, and, you could have larger front rotors (12 3/4" - 13"). The standard Big red rotors are cheaper than the Turbo S rotors, and, being larger, give more leverage- unfortuantely, they also weigh more, but it all depends on what you have, and what you want to accomplish- oh, and how much $$$ you have
Good Luck,
Robby
10-26-2001, 04:34 PM
#5
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With an '86 there's no upgrade path to S4 rotors and calipers unless (as far as I know) you change out the A-arms, spindles, hubs, etc. This is another result of the different offset. There are kits out there that allow an upgrade to Big Reds but one changes the offset which requires you to buy new 17" rims with the new offset and the other kit doesn't change the offset but still require 17" rims to fit.
Stock front and rear calipers on any non S 951 are all the same. 87+ calipers have slightly different piston sizes to get more even pad wear but all non S 951 calipers are interchangeable in terms of fit.
Hugh '86 951
Stock front and rear calipers on any non S 951 are all the same. 87+ calipers have slightly different piston sizes to get more even pad wear but all non S 951 calipers are interchangeable in terms of fit.
Hugh '86 951
10-27-2001, 07:28 PM
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Hugh,
Right about the offset stuff. The 17"+ rims are also needed to increase rotor size. I want to go to 13" mysels, or the standard 993 TT (12.68" or 12 5/8) if I have to... BTW, you didn't mean that all of the front and rear caliper's were the same size on non S Turbo's did you? I mean as in- the front's are the same as the rears? I assumed not, but(?)...
If anyone's interested, here are some links to some cool site's that give lot's of info on BR's, Turbo S (S4), Alcon's, etc, w/prices, caliper sizes, piston bores, pad sizes, rotor sizes, etc...
www.stealth-3000gt.st/FAQbrakeupgr.htm
and, these last two can be acessed to from the first by clicking on the links, but they are:
www.stillen.com/brakes/systems/systems.html
www.ultimategarage.com/
Right about the offset stuff. The 17"+ rims are also needed to increase rotor size. I want to go to 13" mysels, or the standard 993 TT (12.68" or 12 5/8) if I have to... BTW, you didn't mean that all of the front and rear caliper's were the same size on non S Turbo's did you? I mean as in- the front's are the same as the rears? I assumed not, but(?)...
If anyone's interested, here are some links to some cool site's that give lot's of info on BR's, Turbo S (S4), Alcon's, etc, w/prices, caliper sizes, piston bores, pad sizes, rotor sizes, etc...
www.stealth-3000gt.st/FAQbrakeupgr.htm
and, these last two can be acessed to from the first by clicking on the links, but they are:
www.stillen.com/brakes/systems/systems.html
www.ultimategarage.com/
10-28-2001, 01:11 AM
#7
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Robby,
Yes, all front and rear calipers on non S 951's are identical in size as well as fit. They are different from side to side but that's it (i.e. a left side caliper won't work properly on the right side). The proportioning valve adjusts brake bias to even out the braking forces.
Stock 951's have a 5/18 valve. My understanding is that braking forces are evenly distributed up to 5 bar of pressure. Above 5 bar, only 18 percent of the additional pressure over 5 bar being fed to the system is fed to the rear. This helps prevent rear brake lockup.
If you track your pad wear between the front and rear calipers, you'll find your rear pads seem to last forever.
Anyone upgrading to the Big Reds should consider changing to the 928's proportioning valve which is a 5/33. I'm still on stock calipers and have also swapped to the 5/33 to get more out of the brakes on the track. On the street, the rears absolutely do lock up earlier now. Maybe a bit too early.
On non-ABS cars, the installation is easy as the valve is on the master cyliner. On ABS cars it's more involved as the valve is behind a fender liner.
Hugh
'86 951
Yes, all front and rear calipers on non S 951's are identical in size as well as fit. They are different from side to side but that's it (i.e. a left side caliper won't work properly on the right side). The proportioning valve adjusts brake bias to even out the braking forces.
Stock 951's have a 5/18 valve. My understanding is that braking forces are evenly distributed up to 5 bar of pressure. Above 5 bar, only 18 percent of the additional pressure over 5 bar being fed to the system is fed to the rear. This helps prevent rear brake lockup.
If you track your pad wear between the front and rear calipers, you'll find your rear pads seem to last forever.
Anyone upgrading to the Big Reds should consider changing to the 928's proportioning valve which is a 5/33. I'm still on stock calipers and have also swapped to the 5/33 to get more out of the brakes on the track. On the street, the rears absolutely do lock up earlier now. Maybe a bit too early.
On non-ABS cars, the installation is easy as the valve is on the master cyliner. On ABS cars it's more involved as the valve is behind a fender liner.
Hugh
'86 951
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10-28-2001, 04:23 AM
#8
Race Director
With an '86 there's no upgrade path to S4 rotors and calipers
Notice that they have two different type of brake hats? The short one's for the '86 and the thicker one is for the '87+ cars. Talked to them about this a while back and they do have kits for '86.
That's really the only difference (hats). The rotors, adapters and calipers are all the same.
And there's people out there who have put the Big Red upgrades with 13" rotors (some minor grinding involved). I measured the clearance on my stock brake setup and I've got 24mm of clearance between my rims and the back of the caliper. So I can actually increase my rotors to 13.7" and still fit under 16" rims (assuming Big Reds are same height above rotor as stock).
10-28-2001, 06:53 AM
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Hugh,
That's a new one on me... I'm not trying to argue- I don't even have a regular 951- Mine's an S, but, I don't understand why Garrity Repta would put the front's on the rears when people uprgrade the front's to BR's if they were the same size(?). I mean, why bother? Also, Chris Cervelli told me that going to the original turbo front's (for the rear) would be too big, even for BR's (proportionally), and that the piston size is so great, that pedal travel would be too much. Maybe Garrity get's them to just squeeze by(?)... Also, I have the piston sizes written down somewhere, and the front size was pretty big, bigger than the rear- BR's were bigger of course (36mm & 44MM) and Turbo S fronts are even bigger (38mm & 44mm), which is one reason why KVR say's not to go to BR's if you ALREADY have Turbo S front's, despite the pad dif... I've never really looked at the front's that closely on a regular 951, but I was always under the impression that the rears stayed the same from the normal to the S, but that the front's were always bigger, and then got even bigger on the S(?). If this isn't true, then all of the people who are doing business w/the aforementioned businesses, are being misled, but there's no reason for that to be the case, as the businesses aren't gaining anything from telling people to keep existing caliper's in place whether they're the front's or the rears being used on the rear in addition to BR's or whatever... Besides I've done business w/these guy's, and know them to be honest, and knowledgeable. Maybe I've been thrown off somehow, but I've been discussing this stuff w/them for awhile...
That's a new one on me... I'm not trying to argue- I don't even have a regular 951- Mine's an S, but, I don't understand why Garrity Repta would put the front's on the rears when people uprgrade the front's to BR's if they were the same size(?). I mean, why bother? Also, Chris Cervelli told me that going to the original turbo front's (for the rear) would be too big, even for BR's (proportionally), and that the piston size is so great, that pedal travel would be too much. Maybe Garrity get's them to just squeeze by(?)... Also, I have the piston sizes written down somewhere, and the front size was pretty big, bigger than the rear- BR's were bigger of course (36mm & 44MM) and Turbo S fronts are even bigger (38mm & 44mm), which is one reason why KVR say's not to go to BR's if you ALREADY have Turbo S front's, despite the pad dif... I've never really looked at the front's that closely on a regular 951, but I was always under the impression that the rears stayed the same from the normal to the S, but that the front's were always bigger, and then got even bigger on the S(?). If this isn't true, then all of the people who are doing business w/the aforementioned businesses, are being misled, but there's no reason for that to be the case, as the businesses aren't gaining anything from telling people to keep existing caliper's in place whether they're the front's or the rears being used on the rear in addition to BR's or whatever... Besides I've done business w/these guy's, and know them to be honest, and knowledgeable. Maybe I've been thrown off somehow, but I've been discussing this stuff w/them for awhile...
10-28-2001, 10:29 AM
#10
Race Director
Here's a complete list of brake-proportioning valves:
Actually there are numerous sources for an infinitely-adustable brake-proportioning valve. Truechoice, Racer Parts Warehouse, etc... Another way to do it with a balance-bar and dual master cylinders in parallel (stock on is in series).
Actually there are numerous sources for an infinitely-adustable brake-proportioning valve. Truechoice, Racer Parts Warehouse, etc... Another way to do it with a balance-bar and dual master cylinders in parallel (stock on is in series).
10-28-2001, 11:44 AM
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Danno,
Do you have a website? I saw one the other day, and belive it was your's (someone named Dan), and tried to e-mail the address (there were parts for sale-?), but it wouldn't go through...
I've looked into bias valves- I plan to use a 928 (33), but have been told the 928 had several diferent one's over it's life span(?)- no matter, everyone seems to use the 33. I've considered an adj, but am afraid it may be difficult to get set correctly(?). Do you know if this is true or not, and can one know exactly what the pressure is as they adjust it, do you need some type of gauge, or just go by "feel" or what? Also, the balance bar and other master cylinders- are these an expensive proposition (I assume so, at least installation)? Have you, or anyone you know, done anything like this to a 951? When you go to really large pistons, the pedal travel increases, and you would have to change the master cyl to get it right, so I wondered about doing this to allow ULTRA-large brakes...
This is why Hugh has stupmed me on the front and rear caliper size issue. Piston size determines pedal travel- a bigger piston displaces more fluid. A large piston's advantage is more equalized pressure on the pad, and better, more even wear. If the pad were the size of a schoolboard eraser and used one 2mm piston, then the incredible pressure of brakes (psi) would cause some really strange wear, brakes would overheat easier, and have much more trouble overall.
Awhile back, I had planned to install some front 951 calipers to the rear of my Turbo S, and was going to go to BR's up front eventually, but not right away. Most people said it was a mistake, unless I did it VERY soon, but even then, other's said it didn't matter, that front 951's were much too big for even BR's and would give way too much piston to use effectively. Maybe the pad size of the front to rears is the same(?)...
Do you have a website? I saw one the other day, and belive it was your's (someone named Dan), and tried to e-mail the address (there were parts for sale-?), but it wouldn't go through...
I've looked into bias valves- I plan to use a 928 (33), but have been told the 928 had several diferent one's over it's life span(?)- no matter, everyone seems to use the 33. I've considered an adj, but am afraid it may be difficult to get set correctly(?). Do you know if this is true or not, and can one know exactly what the pressure is as they adjust it, do you need some type of gauge, or just go by "feel" or what? Also, the balance bar and other master cylinders- are these an expensive proposition (I assume so, at least installation)? Have you, or anyone you know, done anything like this to a 951? When you go to really large pistons, the pedal travel increases, and you would have to change the master cyl to get it right, so I wondered about doing this to allow ULTRA-large brakes...
This is why Hugh has stupmed me on the front and rear caliper size issue. Piston size determines pedal travel- a bigger piston displaces more fluid. A large piston's advantage is more equalized pressure on the pad, and better, more even wear. If the pad were the size of a schoolboard eraser and used one 2mm piston, then the incredible pressure of brakes (psi) would cause some really strange wear, brakes would overheat easier, and have much more trouble overall.
Awhile back, I had planned to install some front 951 calipers to the rear of my Turbo S, and was going to go to BR's up front eventually, but not right away. Most people said it was a mistake, unless I did it VERY soon, but even then, other's said it didn't matter, that front 951's were much too big for even BR's and would give way too much piston to use effectively. Maybe the pad size of the front to rears is the same(?)...
10-28-2001, 02:08 PM
#12
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Danno,
The Kokeln kit is for Big Red brakes, not S4. S4 rotors are a one piece design which don't allow for a different hat to be installed. The typical Big Red kit uses one piece C2Turbo rotors but the Kokeln kit uses 993TT rotors which are two piece. So they replace the hat with one that will fit the pre-87 offset. I've no idea if S4 calipers will fit 993TT rotors.
The 17" requirement for BR kits is due to the caliper height, not the rotor size. BR caliper are higher over the rotor than S4 or stock calipers. A friend and I did try and fit some 16" clubsport rims onto a set of BR's and the fit was tight but it did clear so I wonder if what other 16" rims would fit.
The caliper adapters for S4 and BR's are the same.
So again, there's no upgrade path to S4 brakes for a pre-87 offset car but there IS an upgrade path to BR. The Kokeln kit does not change the offset, the VCI kit does.
If someone does find an S4 kit for pre-87 cars, I'd be very interested as I'm not all that interested in going to 17" rims.
Robby: As far as the confusion about the caliper sizes...I'm dead WRONG! For whatever reason, I've been thinking pad size. Neurons are crosswired this week. My apologies. Your comment about the piston sizes jogged my memory. Sigh...sucks to have spread disinformation.
-Hugh
'86 951
The Kokeln kit is for Big Red brakes, not S4. S4 rotors are a one piece design which don't allow for a different hat to be installed. The typical Big Red kit uses one piece C2Turbo rotors but the Kokeln kit uses 993TT rotors which are two piece. So they replace the hat with one that will fit the pre-87 offset. I've no idea if S4 calipers will fit 993TT rotors.
The 17" requirement for BR kits is due to the caliper height, not the rotor size. BR caliper are higher over the rotor than S4 or stock calipers. A friend and I did try and fit some 16" clubsport rims onto a set of BR's and the fit was tight but it did clear so I wonder if what other 16" rims would fit.
The caliper adapters for S4 and BR's are the same.
So again, there's no upgrade path to S4 brakes for a pre-87 offset car but there IS an upgrade path to BR. The Kokeln kit does not change the offset, the VCI kit does.
If someone does find an S4 kit for pre-87 cars, I'd be very interested as I'm not all that interested in going to 17" rims.
Robby: As far as the confusion about the caliper sizes...I'm dead WRONG! For whatever reason, I've been thinking pad size. Neurons are crosswired this week. My apologies. Your comment about the piston sizes jogged my memory. Sigh...sucks to have spread disinformation.
-Hugh
'86 951
10-29-2001, 02:10 AM
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Hugh,
Cool enough... I didn't know ANYTHING about the pad sizes...
As for the BR's being the only part that won't clear the 16" rims- does this mean it might be possible to run larger rotors, like the 993TT's w/16" rims w/my stock S4 calipers? I know that KVR says one of their reasons for not considering the BR's as an upgrade to S4's is b/c the S4 can hold a larger rotor- that's what they say at least. I have read about people "machining" BR calipers to fit larger rotors, like 14"...
I would really like to get some lightweight rotors, as I would really like to run some 13", or maybe even the 12 5/8" stock 993TT rotor size, but don't want to add weight over my Turbo S rotors- any suggestions? Ceramic's sound like the way to go, but I doubt I could find a way to retrofit, and even if I could, it would be pricey I'm, sure. KVR and other's have recommended 2-piece, but I've been told they really aren't much lighter, and the weight that is removed, is removed from the center, which wouldn't help nearly as much as lightening the outer edge. So, I'm not sure they would be worth the $ either(?). Any ideas?
Thanks,
Robby
Cool enough... I didn't know ANYTHING about the pad sizes...
As for the BR's being the only part that won't clear the 16" rims- does this mean it might be possible to run larger rotors, like the 993TT's w/16" rims w/my stock S4 calipers? I know that KVR says one of their reasons for not considering the BR's as an upgrade to S4's is b/c the S4 can hold a larger rotor- that's what they say at least. I have read about people "machining" BR calipers to fit larger rotors, like 14"...
I would really like to get some lightweight rotors, as I would really like to run some 13", or maybe even the 12 5/8" stock 993TT rotor size, but don't want to add weight over my Turbo S rotors- any suggestions? Ceramic's sound like the way to go, but I doubt I could find a way to retrofit, and even if I could, it would be pricey I'm, sure. KVR and other's have recommended 2-piece, but I've been told they really aren't much lighter, and the weight that is removed, is removed from the center, which wouldn't help nearly as much as lightening the outer edge. So, I'm not sure they would be worth the $ either(?). Any ideas?
Thanks,
Robby
10-29-2001, 03:14 AM
#14
Race Director
You'll have to try to qnantify your brake upgrade, that is, how much of a performance increase you will get (seconds per lap) for how much money spent. There are NUMEROUS people out there who are currently using the BR brake upgrade on their Turbo/TurboS with GREAT results (Oliver, Tom Pults from email list, check out http://www.944s2.com/brakes.htm).
Rather than discussion theoretical aspects, try measuring the clearances you have on your current set-up and go from there. With my HRE 16x10.25" wheels all around, I know I have enough clearance without machining the BR calipers when using bigger rotors. Others who are using the Porsche cast wheels (with thicker rims) have had to grind their calipers, but they fit.
But there's yet another route you can take. Rather than use standard Porsche parts, you can go to the aftermarket for better value and performance. Instead of using the 322mm 928/993 cast-iron rotors (heavy), can save weight and improve performance by going to full 13"/330mm two-piece STEEL rotors with aluminum hats.
Like on the Kokeln upgrade. Coleman and Baer also make great brake-upgrade parts as well. Using steel rotors (Coleman) will save you 4-5lbs per wheel because steel is 3x stronger than cast-iron, so you can use less of it for the same strenght. You'll end with something like this:
Rather than discussion theoretical aspects, try measuring the clearances you have on your current set-up and go from there. With my HRE 16x10.25" wheels all around, I know I have enough clearance without machining the BR calipers when using bigger rotors. Others who are using the Porsche cast wheels (with thicker rims) have had to grind their calipers, but they fit.
But there's yet another route you can take. Rather than use standard Porsche parts, you can go to the aftermarket for better value and performance. Instead of using the 322mm 928/993 cast-iron rotors (heavy), can save weight and improve performance by going to full 13"/330mm two-piece STEEL rotors with aluminum hats.
Like on the Kokeln upgrade. Coleman and Baer also make great brake-upgrade parts as well. Using steel rotors (Coleman) will save you 4-5lbs per wheel because steel is 3x stronger than cast-iron, so you can use less of it for the same strenght. You'll end with something like this:
10-29-2001, 06:13 AM
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Danno,
Unfortunately, I can't get his website to come up- my computer's a piece o S***!!! I've e-mailed him before, and we can't decide why it won't do it, but everytime it comes up, it say's I have to install "virtual machine", but won't allow me to do it, so none of the stuff on his site comes up...
Is there a place I can go to find out the exact measurements of the Turbo S calipers, and/or the those of my stock calipers? How would I measure my rims for clearance- What points exactly?
I know that BR's can be used successfully- I was just saying that I doubt it's a worthy upgrade to the Turbo S, unless your Turbo S calipers are worn out- BR's are cheaper. The Turbo S brakes have larger pistons, can use larger calipers, and something about the way they are made (more centered at the connection-?)- these are their advantages over BR's (according to places like KVR). BR's only advantage is their greater pad size. I'm not sure that the extra pad size doesn't make up for the other stuff though- it very well may. I just doubt it would be noticeable enough to be worth the $ to convert (for a Turbo S). I don't track my car either, so it really seems to be a waste when looked at that way- I doubt BR's would help at all on a single stop(?).
I would really like a way to maximize what I've got- I would especially like to be able to increase rotor size, and, lose a few pounds. I'm also wondering what size rotor's people go to in the rear when they do these upgrades- BR's, 17"+ rims, 13"+ rotors, etc...(?). I wouldn't want to go to 17" rims, and use the same size rotor as I have now- I like to fill up the rims, like the way they are now w/12" rotors in 16" rims. But, I wonder if the drum brake in the rear makes them difficult to upgrade(?)...
Any input?
Thanks,
Robby
PS: BTW, nice looking 2-piece rotors in the pics...
Unfortunately, I can't get his website to come up- my computer's a piece o S***!!! I've e-mailed him before, and we can't decide why it won't do it, but everytime it comes up, it say's I have to install "virtual machine", but won't allow me to do it, so none of the stuff on his site comes up...
Is there a place I can go to find out the exact measurements of the Turbo S calipers, and/or the those of my stock calipers? How would I measure my rims for clearance- What points exactly?
I know that BR's can be used successfully- I was just saying that I doubt it's a worthy upgrade to the Turbo S, unless your Turbo S calipers are worn out- BR's are cheaper. The Turbo S brakes have larger pistons, can use larger calipers, and something about the way they are made (more centered at the connection-?)- these are their advantages over BR's (according to places like KVR). BR's only advantage is their greater pad size. I'm not sure that the extra pad size doesn't make up for the other stuff though- it very well may. I just doubt it would be noticeable enough to be worth the $ to convert (for a Turbo S). I don't track my car either, so it really seems to be a waste when looked at that way- I doubt BR's would help at all on a single stop(?).
I would really like a way to maximize what I've got- I would especially like to be able to increase rotor size, and, lose a few pounds. I'm also wondering what size rotor's people go to in the rear when they do these upgrades- BR's, 17"+ rims, 13"+ rotors, etc...(?). I wouldn't want to go to 17" rims, and use the same size rotor as I have now- I like to fill up the rims, like the way they are now w/12" rotors in 16" rims. But, I wonder if the drum brake in the rear makes them difficult to upgrade(?)...
Any input?
Thanks,
Robby
PS: BTW, nice looking 2-piece rotors in the pics...