951 Brake Upgrade
11-25-2011, 11:58 AM
#16
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So Marc, do you now run a dual m/c Tilton type setup? Are you saying that with this setup you now have a lot longer pedal travel but better modulation? Or a similar pedal travel but requiring much higher pressure from you? Does the pressure required vary when you adjust front to rear bias? Also, is your car a stripped out trackcar. How much does it weigh?
Unfortunately those of us supposedly 'blessed' with Mo30 can't retrofit these contemporary calipers....shame...
Unfortunately those of us supposedly 'blessed' with Mo30 can't retrofit these contemporary calipers....shame...
The car is stripped out and weighs 2600lbs. The brake booster had to be removed so that the LS would fit.
The short answer is that I am running an ATE master cylinder from a 740iL. The physical dimensions are the same as the OE 951 master but the circuits are larger (25/21). When I put the LS in I needed bigger brakes but my car is an '86 so I had the early offset.
Long answer is that I knew I was going to change over to the late offset in the future, and wanted the biggest brakes for least amount of money. I put on the biggest 4 piston Wilwoods made (Ebay 150 bucks, rebuilt). The pistons were 1.88 and 1.62. These are huge compared to the '86 pistons. The pads for the Wilwoods were 50% larger than the OE pads and 1/4 of the price. I had to find a larger M/C to accommodate the larger pistons and installed a proportioning valve.
Fast forward to the present. I am still running the 740iL M/C and proportioning valve, no reason to change as both are less than 4 seasons old. On pedal travel, I have much less than with the Wilwoods, because the piston area of the GT3 calipers is much less than the Wilwoods. In fact the piston area of the GT3 calipers is not much greater than the '87 951 calipers and almost the same as the Mo30 (S4) calipers. (Again, I have exact numbers at home). I can't comment on pedal pressure vs the 951 M/C. There is no discernible change in pedal pressure when changing front to rear bias.
Anyone doing this upgrade could keep their existing M/C and adjust bias by using different pads in the rear if there is a problem. The Mo30 M/C and pressure valve should work perfectly. Non Mo30 cars could swap the Mo30 valve for the one on their M/C.
Marc
__________________________
'00 Audi TT
'99 996 (Wife's ride)
'86 951 LS1 (C-2)
'77 911 3.2 (C-1) Gone but not forgotten.
3.2 Conversion and 915 Rebuild Home Page
The 958 Conversion
958 Track Video
PCA National Registry of Instructors
Last edited by marc a; 11-29-2011 at 07:35 PM.
11-25-2011, 12:08 PM
#17
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Marc, thanks for this tid bit, I haven't previously heard of anyone using a valve in-line to keep a minimum pressure. While I think in my last race I may have had one front wheel bearing a bit too loose, I am still scratching my head trying to figure out the brake pedal issues.
Do you have a source for the valve?
Do you have a source for the valve?
http://www.wilwood.com/MasterCylinde...temno=260-3278
11-25-2011, 10:33 PM
#18
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Ha, that's interesting Marc. I pursued the mythical 7 series m/c for some time. I remember reading somewhere that this was the next size up that would fit an OEM setup. I even bought one from Ebay some years ago. I contacted ATE and they wouldn't give me any details for fear of some legality if I was in a crash. The idea being that going up to Big Reds constituted an increase in piston size and therefore needed larger piston area vs stock. I never tested it but glad you have and can verify to it's veracity.
I found that when I used Mo30 setup with Big Reds in my '89 (abs) it worked pretty well, but there did seem to be issues with longer or softer pedal from time to time. I switched pads from EBC to PFC and found them to be massively better. Never noticed the abs kick in on the track either. Then when we shifted all the running gear across to the '86 without abs I found that I was flat spotting tyres...which as you might know, is a real pain in the butt...especially as we sometimes bought and shipped these over from the US. My interest was piqued when you mentioned you had to take out the booster. Although I knew this to be a common change needed with LS conversions, I thought you might have gone for dual m/c setup and were alluding to some changed pedal characteristics. As I have had this done on my car I was interested to gain any foresight as what to expect. I have read from the few that have also done this that the pedal needs much greater effort but the modulation is dramatically improved. To add, this is something that can be altered with the size of the dual m/cs and also the bias adjuster. Wish I could fit the Monoblocks but am hoping for a car of similar weight to yours so perhaps the Big Reds will be ok...for now...
I found that when I used Mo30 setup with Big Reds in my '89 (abs) it worked pretty well, but there did seem to be issues with longer or softer pedal from time to time. I switched pads from EBC to PFC and found them to be massively better. Never noticed the abs kick in on the track either. Then when we shifted all the running gear across to the '86 without abs I found that I was flat spotting tyres...which as you might know, is a real pain in the butt...especially as we sometimes bought and shipped these over from the US. My interest was piqued when you mentioned you had to take out the booster. Although I knew this to be a common change needed with LS conversions, I thought you might have gone for dual m/c setup and were alluding to some changed pedal characteristics. As I have had this done on my car I was interested to gain any foresight as what to expect. I have read from the few that have also done this that the pedal needs much greater effort but the modulation is dramatically improved. To add, this is something that can be altered with the size of the dual m/cs and also the bias adjuster. Wish I could fit the Monoblocks but am hoping for a car of similar weight to yours so perhaps the Big Reds will be ok...for now...
11-25-2011, 10:36 PM
#19
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Well if you really wan to you can switch to the 968 or late model S2 spindles. According to Racers Edge they are the same strength as the M030. Then you have to figure out the spacers, but it is doable.
I wound up switching back to the non M030 spindles after a guy hit me on the track breaking my left front rotor and spindle.
I wound up switching back to the non M030 spindles after a guy hit me on the track breaking my left front rotor and spindle.
11-26-2011, 03:41 PM
#24
I don't think many peope do know the numbers of some of the newer cars. I just thought I'd point it out.
Not trying to nit pick or pick on you. Just sharing information.
I'm still tempted by the 948 myself.
Not trying to nit pick or pick on you. Just sharing information.
I'm still tempted by the 948 myself.
11-28-2011, 09:48 AM
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So did you put the Touareg/Cayenne Rotors and Calipers on your car? I thought about doing that when I worked for Lamborghini as I could get the Calipers from our parts department for a decent deal. I think it is the same Brembo caliper as the rest of them for some reason. I am overdue for brakes on my '87 951 and only want to change them one time. I have often wondered if I could get a hookup at the local VW dealership and put those calipers and rotors on my car. Do you have a good source for this stuff? The prices you quoted seem really inexpensive.
11-28-2011, 08:12 PM
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Ok, so you used 6 piston GT3 calipers with the Cayenne/Touareg rotors? Where did you source these things from? Just the VW dealership and the Porsche store? Sounds like a great set up. Did you use the mounting hardware from 9P?
11-28-2011, 10:06 PM
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6 Piston calipers from a 996 GT3 (not 997) 2000 Ebay
Adapter blocks from VCI (see post on page 1): 275
350mm Rotors from a Cayenne or Q7: 150 to 220/pr depending on vendor. Ebay, Amazon
Centering rings from Rennlist member Xschop for rotors: 80
Banjo bolts and unions to have the flex brake line feed in from bottom of caliper rather than straight in. Here are the part numbers: 901 355 531 00 & 914 355 531 00. I got them from Patrick Motorsports. They have them in stock.
65mm studs which VCI also provided were optional.
Brake pads range from 80 (cheap street) to 400 (best race pads). Ebay
18" wheels.
Marc
__________________________
'00 Audi TT
'99 996 (Wife's ride)
'86 951 LS1 (C-2)
'77 911 3.2 (C-1) Gone but not forgotten.
3.2 Conversion and 915 Rebuild Home Page
The 958 Conversion
958 Track Video
PCA National Registry of Instructors
Adapter blocks from VCI (see post on page 1): 275
350mm Rotors from a Cayenne or Q7: 150 to 220/pr depending on vendor. Ebay, Amazon
Centering rings from Rennlist member Xschop for rotors: 80
Banjo bolts and unions to have the flex brake line feed in from bottom of caliper rather than straight in. Here are the part numbers: 901 355 531 00 & 914 355 531 00. I got them from Patrick Motorsports. They have them in stock.
65mm studs which VCI also provided were optional.
Brake pads range from 80 (cheap street) to 400 (best race pads). Ebay
18" wheels.
Marc
__________________________
'00 Audi TT
'99 996 (Wife's ride)
'86 951 LS1 (C-2)
'77 911 3.2 (C-1) Gone but not forgotten.
3.2 Conversion and 915 Rebuild Home Page
The 958 Conversion
958 Track Video
PCA National Registry of Instructors
06-12-2012, 03:44 PM
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Cayenne rotors are 68,5 mm high ... so the caliper has to be 8,5 mm out of the body of the car (M030 or big red have 77mm high discs)
did you use spacers for rims ?
did you use spacers for rims ?