Brake FAQ - rotors, calipers, master cylinder sizes, proportioning valves, etc.
This post summarizes the specs and operation of brake components for the MkII MR2. The focus is on North American cars but the info should apply to other cars as well.
Rotors:
Rotor diameter and thickness is given. To calculate effective radius for brake torque calculations, use Re=((OD?+ID?)/2)^0.5 where OD is outer-diameter and ID is inner diameter where the brake pad ends. For best all-around track/race performance, choose plain OEM-style rotors and steer clear from "cross-drilled" or "slotted" rotors.
OEM Pads:
After-market Pads:
Aftermarket high-performance brake pad compound data
Included in this list are approximate friction coefficients (determines max brake torque) and temperature ranges (fade resistance and cold bite) Note that pad compounds rarely have a constant cF over the whole temperature range. for example EBC pads:
Pad life on the racetrack?
http://mr2oc.com/showthread.php?t=403191
Calipers:
1993+ turbo calipers have the same size pistons as 1991-1992 calipers, but the caliper and bracket are much larger to accommodate the larger rotors.
Brake proportioning valves:
Master cylinders:
Brake boosters:
Continued at: http://mr2oc.com/showpost.php?p=3250142&postcount=6
This post summarizes the specs and operation of brake components for the MkII MR2. The focus is on North American cars but the info should apply to other cars as well.
Rotors:
Rotor diameter and thickness is given. To calculate effective radius for brake torque calculations, use Re=((OD?+ID?)/2)^0.5 where OD is outer-diameter and ID is inner diameter where the brake pad ends. For best all-around track/race performance, choose plain OEM-style rotors and steer clear from "cross-drilled" or "slotted" rotors.
- Front
- 1993+ Turbo vented [275mm*30mm] [replace@28mm]
- 1991-1992 Turbo & 1991+ NA vented [258mm*25mm] [replace@24mm]
- Rear
- 1993+ Turbo vented [280mm*22mm] [replace@21mm]
- 1991-1992 Turbo & 1991+ NA vented [262mm*16mm] [replace@15mm]
OEM Pads:
- Front
- 1993+ Turbo MKD582 (50cm?)
- 1991-1992 Turbo MKD489 (49cm?)
- 1991+ NA MKD242 [15mm thick] [105mmx47mm overall size]
- Rear
- 1991+ NA/Turbo MKD657 - all cars use the same pad
After-market Pads:
- Front NA
- Hawk HB191.590 [HPS/HP+/HT-10/Blue-9012]
- Porterfield AP242 [R4/R4E/R4S/R4-1]
- Ferodo SD242 [DS2500/DS3000, etc]
- Axxis Ultimate 109.02420
- Carbotech CT242 [Bobcat,AX6, XP8, XP10, XP12]
- Front Turbo 1991-1992
- Porterfield AP489 [R4/R4E/R4S]
- Ferodo D489 [DS2500/DS3000/etc]
- Axxis Ultimate 109.04890
- Carbotech CT489 [Bobcat, AX6, XP8, XP10, XP12]
- Front Turbo 1993+
- Porterfield AP582 [R4/R4E/R4S]
- Ferodo D582 [DS2500/DS3000/etc]
- Axxis Ultimate 109.05820
- Carbotech CT582 [Bobcat, AX6, XP8, XP10, XP12]
- Rear (all)
- Porterfield AP309 [R4/R4E/R4S]
- Axxis Ultimate 109.06570
- Ferodo D528/D657 (not available any more)
- Wagner PD309/PD657
- Carbotech CT528/657 [Bobcat, AX6, XP8, XP10, XP12]
Aftermarket high-performance brake pad compound data
Included in this list are approximate friction coefficients (determines max brake torque) and temperature ranges (fade resistance and cold bite) Note that pad compounds rarely have a constant cF over the whole temperature range. for example EBC pads:
- Street/Track
- Axxis Ultimate [cF=0.40] [0?F-900?F]
- EBC Yellow [cF=0.55] [0?F-900?F]
- Porterfield R4-S [cF=0.40] [0?F-900?F]
- Hawk HPS [cF=0.40] [0?F-750?F]
- Hawk HP+ [cF=0.45-0.50] [0?F-900?F]
- Ferodo DS2500 [cF=0.50] [100?F-1000?F]
- Carbotech Bobcat [cF=0.45] [0?F-900?F]
- Carbotech Panther Plus/AX6 [cF=0.54] [150?F-1250?F]
- Track/Race
- Porterfield R4 [cF=0.485]
- Porterfield R4-E [cF=0.485??]
- Ferodo DS3000 [cF=0.62] [300?F-1500?F]
- Hawk Blue 9012 [cF=0.52] [250?F-1000?F]
- Hawk HT-10 [cF=0.55] [300?F-1600?F]
- Carbotech Panther XP8 [cF=0.58] [200?F-1350?F]
- Carbotech Panther XP10 [cF=0.6] [300?F-1600?F]
Pad life on the racetrack?
http://mr2oc.com/showthread.php?t=403191
Calipers:
1993+ turbo calipers have the same size pistons as 1991-1992 calipers, but the caliper and bracket are much larger to accommodate the larger rotors.
- Front
- 1993+ Turbo dual piston front caliper [2x36.5mm = 2092.6mm?] (identification stamp: AISIN 36T30)
- 1991-1992 Turbo dual piston front caliper [2x36.5mm = 2092.6mm?] (identification stamp: AISIN 36T25)
- 1991+ N/A single piston front caliper [1x51mm = 2026.8mm?]
- Rear
- 1993+ Turbo single piston rear caliper [1x42.9mm =1452.2mm?] (idetification stamp: left:22VL right:22VR)
- 1991-1992 Turbo/1991+ NA single piston rear caliper [1x41.3mm = 1339.6mm?] (identification stamp: left:16VL right:16VR)
Brake proportioning valves:
- Here is how it works. After the threshold line pressure is reached, the valve kicks in and begins to reduce pressure to the rear brake pistons. So for moderate pedal pressures, the front and rear brake pressures are the same, but once you start to squeeze the pedal harder, the front pressure continues to rise, but the rear pressure rises at a slower rate.
- Because the weight of the car transfers forward to the front axle under braking, the front tires have more grip and the rears have less grip. Because the rears have less grip, you need to reduce the braking force on the rear with respect to the front to prevent the rear wheels from locking up. Without a proportioning valve, the car would skid out of control very easily under braking. So Toyota, like most other manufacturers, installs a proportioning valve at the factory.
- For the turbo cars, not only is the threshold line pressure higher, but the bias is more rearward. There are several reasons for this:
- additional rear weight of turbo engine & accessories
- wider staggered rear tires.
- more piston area in front dual-piston calipers
- Many track junkies report that with non-ABS cars, the front axle tends to lockup well before the rear. It follows that with proper brake pad and tire choice, the brake bias can be moved slightly rearward to better optimize braking performance under extreme braking conditions. So an OEM turbo brake proportioning valve is a suitable upgrade for an N/A car using wider rear tires and the turbo front brake calipers. Some folks opt for an aftermarket adjustable proportioning valve which allows finely tuned braking performance depending on tire choice and changing track conditions.
- NA: above 427PSI, rear increases at 75% rate of front
- Turbo above 853PSI, rear increases at 84% rate of front
- Discussion threads: http://www.mr2oc.com/showthread.php?t=73553 http://mr2oc.com/showthread.php?t=396406
- BGB reference http://www.mr2-tech.com/bgb/mechanical/volume2/brake_system/8.htm
- Stoptech article: http://www.stoptech.com/tech_info/wp_proportioning_valves.shtml
- 1991-1995 NA with ABS (very rare, very expensive)
- 1991-1995 NA without ABS
- 1991-1992 Turbo with ABS
- 1991-1992 Turbo without ABS
- 1993-1995 Turbo with ABS
- 1993-1995 Turbo without ABS
Master cylinders:
- 1991-1995 NA & 1991-1992 Turbo 7/8" bore size (~22mm)
- 1993-1995 Turbo 15/16" bore size (~24mm)
- Other options: http://www.mr2oc.com/showthread.php?t=185454
- There are physical differences between master cylinders with ABS and without, but the bore sizes are as shown above.
Brake boosters:
- 1991-1992 NA (with or without ABS)
- 1991-1992 Turbo (with or without ABS)
- 1993-1995 NA (with or without ABS)
- 1993-1995 Turbo with ABS
- 1993-1995 Turbo without ABS
Continued at: http://mr2oc.com/showpost.php?p=3250142&postcount=6