Dual Brake Masters/floor pedals.
01-09-2019, 04:09 PM
#16
Ok, these are the piston sizes of my setup:
1M2.8001A – 355x32mm slotted, w/6p Monobloc: 28/30/36mm pistons
2C2.6017A – 328x28mm slotted, w/4p: 28/30mm pistons
Bill whats the maths on that? :-)
Looks like about a 1.77 split. I have no proportion valve, 993 master.
Here's what I notice in actual use: excellent pedal feel, strong/positive initial bite, good modulation, and at threshold minimal ABS intervention and good balance (ie doesn't feel tail light or nose heavy)
1M2.8001A – 355x32mm slotted, w/6p Monobloc: 28/30/36mm pistons
2C2.6017A – 328x28mm slotted, w/4p: 28/30mm pistons
Bill whats the maths on that? :-)
Looks like about a 1.77 split. I have no proportion valve, 993 master.
Here's what I notice in actual use: excellent pedal feel, strong/positive initial bite, good modulation, and at threshold minimal ABS intervention and good balance (ie doesn't feel tail light or nose heavy)
Your pedal is right where I like to see it, @32.936 this gives you a nice high hard pedal which as you noted is easy to modulate, a lower pedal ratio improves that but the effort to do so goes up causing it's own issues for some.
Again more front is not a safety or major performance issue, it's just not getting the most from the rears as long as you can modulate the brakes and avoid lockup, which the lower pedal ratio helps with. The better the driver the less the abs intervenes because the driver can better predict and apply the right pressure to the pedal. Too much rear is a danger because when braking the rear is light anyway and has a tendency to oscillate side to side( softer springs and more travel exacerbate that) and the slightest amount of lock of 1 wheel can initiate a snap spin, here's where an effective LSD really helps as it assists in the torque distribution between the rear tires, ie less tendency for 1 wheel to lock even momentarily.
01-10-2019, 11:17 AM
#17
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Bill, May have chance to have custom front and rear calipers machined. Given this, what would you consider would be the optimum front and rear rotor size and the best piston sizes (front and rear) for the best bias and pedal pressure. Let’s assume that the MC has been up graded to the 993 single MC unit.
Additionally, would consider using both 17 and 18 inch wheels where a 345 and 355 front rotor could be used with a smaller rotor rear - say a 355/345 and a 345/330 optional configuration for the 964/993.
Additionally, would consider using both 17 and 18 inch wheels where a 345 and 355 front rotor could be used with a smaller rotor rear - say a 355/345 and a 345/330 optional configuration for the 964/993.
01-10-2019, 11:34 AM
#18
Bill, May have chance to have custom front and rear calipers machined. Given this, what would you consider would be the optimum front and rear rotor size and the best piston sizes (front and rear) for the best bias and pedal pressure. Let’s assume that the MC has been up graded to the 993 single MC unit.
Additionally, would consider using both 17 and 18 inch wheels where a 345 and 355 front rotor could be used with a smaller rotor rear - say a 355/345 and a 345/330 optional configuration for the 964/993.
Additionally, would consider using both 17 and 18 inch wheels where a 345 and 355 front rotor could be used with a smaller rotor rear - say a 355/345 and a 345/330 optional configuration for the 964/993.
things that would help bias and pedal feel and the best way to go
smaller front pistons, going from what you have to say what Spyrex has, ie 28/30/36 all else being equal and w/ a +/- due to the est. effective disk, changes the pedal to a nicer 33.8 and bias to a better 1.622, going to 28/30/34 improves both to 32.823 pedal and 1.546 bias, both of these are right where you want to be.
things that help bias but make pedal worse
change the rear to bigger pistons, but this will make the pedal worse, I wouldn't want to go this route
things that change bias but don't affect pedal
go to a bigger rear rotor, the usual reason for a bigger rear is thermal capacity that doesn't apply here, a bigger front or smaller rear would make bias worse
01-10-2019, 11:43 AM
#19
I've been thinking about the pedal a lot more, many of these brake upgrades want a 25.4 or larger m/c. For instance the factory use the more complicated electro-hyd brake booster on the RS, Cup and RSR while we are limited to the 23.8 because of the vacuum booster design
W/ some fabrication it may be possible to fit a Cayman or 996/997 vac. booster in lieu of the 993 vac booster, these later van cans use 25.4 or 27mm m/c.
I haven't done this but it may be possible. You'd likely need to do the same sort of things as when going from the 964 to 993 setup.
Here's a pic of a Cayman booster
W/ some fabrication it may be possible to fit a Cayman or 996/997 vac. booster in lieu of the 993 vac booster, these later van cans use 25.4 or 27mm m/c.
I haven't done this but it may be possible. You'd likely need to do the same sort of things as when going from the 964 to 993 setup.
Here's a pic of a Cayman booster
01-15-2019, 12:39 AM
#21
So-
I’m was in the process of ordering this Brembo set:
1H2.7005A1 993 front which uses a 4 piston caliper on a 332x32mm rotor.
And rear the same as Spyerx :
Brembo GT Kit, 964 - 2C2.6017A - 4 piston, 328x28 mm slotted.
I contacted race technologies and asked for the specs on the front caliper so we could do calcs for master cylinder sizing and was surprised at the response. They said- tell us your master size and we will size the caliper bores accordingly.
Hmm- so if I’m sticking with the 964 master and going with the 332 front rotor and 328 rear what would be ideal front and rear piston sizing?
Or is going to the 993 master and slightly larger piston bores a better path? And if so what would caliper bore sizes result in a good overall pedal and bias ratios?
I’m was in the process of ordering this Brembo set:
1H2.7005A1 993 front which uses a 4 piston caliper on a 332x32mm rotor.
And rear the same as Spyerx :
Brembo GT Kit, 964 - 2C2.6017A - 4 piston, 328x28 mm slotted.
I contacted race technologies and asked for the specs on the front caliper so we could do calcs for master cylinder sizing and was surprised at the response. They said- tell us your master size and we will size the caliper bores accordingly.
Hmm- so if I’m sticking with the 964 master and going with the 332 front rotor and 328 rear what would be ideal front and rear piston sizing?
Or is going to the 993 master and slightly larger piston bores a better path? And if so what would caliper bore sizes result in a good overall pedal and bias ratios?
01-15-2019, 12:57 AM
#22
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Hahah that’s pretty cool :-)
01-15-2019, 01:11 AM
#23
Yeah- if they actually let me choose. They may have liability issues that muddy things up.
Thanks for the advice btw. I had tried mailing them a couple of times before but never received a response.
Pete
Thanks for the advice btw. I had tried mailing them a couple of times before but never received a response.
Pete
01-15-2019, 09:04 AM
#24
So-
I’m was in the process of ordering this Brembo set:
1H2.7005A1 993 front which uses a 4 piston caliper on a 332x32mm rotor.
And rear the same as Spyerx :
Brembo GT Kit, 964 - 2C2.6017A - 4 piston, 328x28 mm slotted.
I contacted race technologies and asked for the specs on the front caliper so we could do calcs for master cylinder sizing and was surprised at the response. They said- tell us your master size and we will size the caliper bores accordingly.
Hmm- so if I’m sticking with the 964 master and going with the 332 front rotor and 328 rear what would be ideal front and rear piston sizing?
Or is going to the 993 master and slightly larger piston bores a better path? And if so what would caliper bore sizes result in a good overall pedal and bias ratios?
I’m was in the process of ordering this Brembo set:
1H2.7005A1 993 front which uses a 4 piston caliper on a 332x32mm rotor.
And rear the same as Spyerx :
Brembo GT Kit, 964 - 2C2.6017A - 4 piston, 328x28 mm slotted.
I contacted race technologies and asked for the specs on the front caliper so we could do calcs for master cylinder sizing and was surprised at the response. They said- tell us your master size and we will size the caliper bores accordingly.
Hmm- so if I’m sticking with the 964 master and going with the 332 front rotor and 328 rear what would be ideal front and rear piston sizing?
Or is going to the 993 master and slightly larger piston bores a better path? And if so what would caliper bore sizes result in a good overall pedal and bias ratios?
Just for comparison 993 uses 36/40 front on 304x32 & 30/34 rear on 299x24 for 1.604 bias and 37.342 pedal
01-15-2019, 08:30 PM
#25
here is a dual master cylinder setup from Rothsport Racing
[0]=68.ARD5BiSTnXWpcOsbQhNglWbeKWaz2X1YkpzY6JK07P27Ad74ALfVQsg2tyLHhBU0bCIg CL4eNTwVYGXnafO0X-aavy5DcIOOM4Wp32umDL3aujJ9TUzyndavSkP-BfMEzp9lBMB0nyoWTNOG4y6WghwZfw-kzFDF3izYlV__RxpYG_AhCvTMcn4zNxrgTinjOo5hXmtjB0gLFuuhTASWpupdlX3bixteZw2 AAzyN2kv_24INQjRl-TQgUR37NMZOir1P-c9XOVRuHgd3EWKL7o_8yD1QQqVpPBGrXm2Jr1OafSNwB77KO3KEru9572WzEahObNDi7864s fONBysuu-3qSw&__tn__=-UC-R
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01-15-2019, 11:35 PM
#26
They use off the shelf calipers and will have a limited choice, w/ roughly equal effective rotor diameters 36/40 front gives ~1.75 bias and ~32 pedal w/ a 23.8mm m/c, I doubt that they have a smaller front
Just for comparison 993 uses 36/40 front on 304x32 & 30/34 rear on 299x24 for 1.604 bias and 37.342 pedal
Just for comparison 993 uses 36/40 front on 304x32 & 30/34 rear on 299x24 for 1.604 bias and 37.342 pedal
Keep in mind that a may also be able to spec the rear caliper. The above caliper sizes are the same as the stock 964 4 pots front and rear.
In your opinion what is the lowest bias I should shoot for? Iirc the 993rs is 1.46 or so. Isn’t that what you run?
I’m planning on removing the stock Pv and possibly putting and adjustable Pv in the cockpit or frunk.
Peter
01-16-2019, 10:09 AM
#27
Thanjs Bill,
Keep in mind that a may also be able to spec the rear caliper. The above caliper sizes are the same as the stock 964 4 pots front and rear.
In your opinion what is the lowest bias I should shoot for? Iirc the 993rs is 1.46 or so. Isn’t that what you run?
I’m planning on removing the stock Pv and possibly putting and adjustable Pv in the cockpit or frunk.
Peter
Keep in mind that this bias is getting to the edge and the car need to be set up for it,
effective lsd
lowered
stiffer suspension
just for comparison all the 911s thru '83 have 1.491 w/ either 35.328 or 41.311 pedal depending on m/c
01-16-2019, 10:57 AM
#28
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Cayman/Dual MC
Bill, looks like there are 2 options right now 1. Go to dual masters using Tilton 2 pedal set up. 2. Try the Cayman conversion to a new vacuum booster/larger MC.
Both look like would require extensive fabrication to install. Not sure which route would be easiest. Pedals would require making custom base plate and brake lines. Plus figuring out route for lines to ABS and reservoir. While Cayman change over might be able to keep lines in general area. But have to fab a custom mount for vacuum canister. But more difficult - would be fabricating an interface between the Cayman set up and the 90 bend we have on the 964/993 for pedal movement directional change. All very interesting to consider.
Both look like would require extensive fabrication to install. Not sure which route would be easiest. Pedals would require making custom base plate and brake lines. Plus figuring out route for lines to ABS and reservoir. While Cayman change over might be able to keep lines in general area. But have to fab a custom mount for vacuum canister. But more difficult - would be fabricating an interface between the Cayman set up and the 90 bend we have on the 964/993 for pedal movement directional change. All very interesting to consider.
01-16-2019, 06:17 PM
#29
These are a 993 24.8 and 964 m/c 20.6
thi is a 993tt 25.4
these are Cayman 25.4 and 997GT3 27.2
the 993 and 964 are not interchangeable
the 993tt and 993 are no suppossed to be but I don't see or know why
the Cayman and GT3 are interchangeable, I spoke to a gent at the track one day who claimed to have modified a Cayman or GT3 m/c to fit on his vacuum boosted 993, but I don't know the details
This is a Cayman vac booster, again not sure what it would take to mate to a 993 or 964
thi is a 993tt 25.4
these are Cayman 25.4 and 997GT3 27.2
the 993 and 964 are not interchangeable
the 993tt and 993 are no suppossed to be but I don't see or know why
the Cayman and GT3 are interchangeable, I spoke to a gent at the track one day who claimed to have modified a Cayman or GT3 m/c to fit on his vacuum boosted 993, but I don't know the details
This is a Cayman vac booster, again not sure what it would take to mate to a 993 or 964
01-16-2019, 08:43 PM
#30
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Front for 997.1 NON PCCB 6 piston: 28, 32, 38mm
Front 997.1 PCCB, 997.2 all 6 piston: 28, 30, 32mm
Rear All: 4 piston 34mm
The master cylinder is the same across all 997.1 and 997.2.
The 997.1 non PCCB cars use a smaller front rotor. The Fronts on all others are the same size 380mm