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jazzcornet said:
makes sense, but then why do people buy big brake kits?
for the same reason they buy the tornado fuel saver, electric superchargers, $5 "performance chips" and super fuel mileage pellets- because they don't fully understand how the system they're trying to improve actually works.

most people just assume that bigger is better. truth is, balance is better. bigger only improves fade resistance, but can have detrimental effects on actual stopping distances. if you want a brake change to be an upgrade, it should not only improve fade resistance, but improve braking distance as well. most people assume that going bigger accomplishes both.
 
phatvw said:
Without a proportioning valve, the car would skid out of control very easily under braking.
I totally disagree, many people (including me) do not change the proportioning valve with great success. Some highly respectable mr2 gurus would say the same.
 
tadjo said:
I totally disagree, many people (including me) do not change the proportioning valve with great success. Some highly respectable mr2 gurus would say the same.
Do not change... but you arn't eliminating it entirely.
 
Discussion starter · #24 ·
Alex W said:
Do not change... but you arn't eliminating it entirely.
Indeed. I clarified the post to indicate that our cars ship from the factory with a proportioning valve which works just fine. But it certainly isn't optimal for all racing conditions which is why some folks swap it for aftermarket valves.
 
Milo_101 said:
Dumb Question maybe, But are the Rear calipers the same as the Front calipers?
Gen 3 car, so 93+ brakes.
It is not a dumb question. That was the point of this "FAQ" thread. But the answer was covered in the first post. Please read it.

Phatvw said:
Calipers:

Although 93+ turbo calipers have the same size pistons, the caliper and caliper carrier is much larger to accommodate the 93+ rotors.

Front
93+ Turbo dual piston front caliper [2x36.5mm = 458.673mm?]
91-92 Turbo dual piston front caliper [2x36.5mm = 458.673mm?]
91+ N/A single piston front caliper [1x51mm = 320.442mm?]

Rear
99+ JDM Turbo single piston rear caliper [1x42.9mm = 269.549mm?]
93-98 Turbo single piston rear caliper [1x41.3mm = 259.496mm?]
91-92 Turbo/91+ NA single piston rear caliper [1x41.3mm = 259.496mm?]
 
phatvw said:
  • Front
  • 93+ Turbo vented [275mm*30mm] [replace@28mm]
  • 91-92 Turbo & 91+ NA vented [258mm*25mm] [replace@24mm]
  • Rear
  • 93+ Turbo vented [280mm*22mm] [replace@21mm]
  • 91-92 Turbo & 91+ NA vented [262mm*16mm] [replace@15mm]
So you're saying that the rear rotors are larger in diameter then the front rotors? that's not normal is it? Or is it cause we have a mid engined cars? Just asking.
 
Discussion starter · #29 ·
The_Kong said:
So you're saying that the rear rotors are larger in diameter then the front rotors? that's not normal is it? Or is it cause we have a mid engined cars? Just asking.
Its true that most cars have larger front rotors by mass, thickness, and diameter. MR2 front rotors are only larger by mass and thickness, not diameter. The mid-engine design with rear weight bias would be a compelling explanation, but you'd have to ask a Toyota engineer to get a real answer for choosing the size they did.
 
Discussion starter · #31 · (Edited)
Blurvision said:
Is there a difference in 91-92 Prop valve compared to 93+

Yes. According to the parts catalog at www.1sttoyotaparts.com, there are 6 different factory prop valves:

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


Now I'm not sure if the 1993+ turbo valve actually changes the proportioning or not - I suspect it has the same proportioning just with an updated design or different parts supplier. I've added this info to the main post.

:thumbup
 
so essentially the 99 spec rears are slightly larger than its predecessors. guessing it wouldn't be as cost effective to hunt one down. looks like i'll just stick to finding a full 93+ set for my 91T.
 
hey . i want to make sure im getting something right. i have a 91 turbo. i want to upgrade to 93 turbo brakes all around.
I NEED: Front 93 calipers, rotors, pads
For the REAR: i Can get calipers from a 91 or 93? just the rotors are bigger? and what about pads?

also, does the parking brake cable go right onto the 93 calipers, or are they the same as a 91?
thanks for help
 
phatvw said:
  • Front
  • 1993+ Turbo dual piston front caliper [2x36.5mm = 458.673mm?]
  • 1991-1992 Turbo dual piston front caliper [2x36.5mm = 458.673mm?]
  • 1991+ N/A single piston front caliper [1x51mm = 320.442mm?]
  • Rear
  • 1999+ JDM Turbo single piston rear caliper [1x42.9mm = 269.549mm?]
  • 1993-1998 Turbo single piston rear caliper [1x41.3mm = 259.496mm?]
  • 1991-1992 Turbo/91+ NA single piston rear caliper [1x41.3mm = 259.496mm?]
just a side note, but i think you may have been calculating the circumference of the pistons (diameter x pi) rather than the area of the pistons (pi x r^2).

36.5mm piston area is 1046.34mm^2, and we multiply that by 4 (because they're sliding calipers), so total effective area for dual piston front calipers is 4185.3 mm^2.

NA front calipers have 50.8mm pistons, so their area is 2026.82 mm^2. multiply that by 2 (also sliding calipers) for a total effective area of 4053.84 mm^2.

the turbo front calipers have about 3% more piston area than the NA calipers.

also, according to centric (brake caliper remanufacturer), the 93 turbos also got the 43mm pistons in the rear calipers, not just the 98 jspec cars.

your list should look like this:

  • Front
  • 1993+ Turbo dual piston front caliper [2x36.5mm = 4185.3mm?]
  • 1991-1992 Turbo dual piston front caliper [2x36.5mm = 4185.3mm?]
  • 1991+ N/A single piston front caliper [1x51mm = 4053.8mm?]
  • Rear
  • 1993+ Turbo single piston rear caliper [1x42.9mm = 2904.4mm?]
  • 1991-1992 Turbo/91+ NA single piston rear caliper [1x41.3mm = 2679.28mm?]

a mod can delete this post once the info is updated.
 
Discussion starter · #35 · (Edited)
Indeed you are correct. Haha an engineer can't do grade 6 math lol!

However, I'm not sure about the "effective" area you're talking about. The brake fluid only presses against the area of the piston so when you do the full calculation from brake line pressure through to brake caliper torque, you don't multiply that value by two. The load is just spread over the inner and outer pad via the caliper housing thats all. You do the multiplication later when you add the number of friction surfaces in.

Here are some great resource with all sorts of brake forumlae and whatnot:
http://www.engineeringinspiration.co.uk/brakecalcs.html
http://www.stoptech.com/tech_info/wp_brakebiasandperformance.shtml



So for the purposes of piston area, I think it should be like this:

Front
1993+ Turbo dual piston front caliper [2x36.5mm = 2092.6mm?]
1991-1992 Turbo dual piston front caliper [2x36.5mm = 2092.6mm?]
1991+ N/A single piston front caliper [1x51mm = 2026.8mm?]

Rear
1993+ Turbo single piston rear caliper [1x42.9mm =1452.2mm?]
1991-1992 Turbo/91+ NA single piston rear caliper [1x41.3mm = 1339.6mm?]



Do you concur?
 
sliding calipers act as if there are pistons on both sides.

from your first link:
reaction force from a sliding caliper is the same as an opposed piston one.
i suppose the math works out either way. i've always thought it easier to work the opposition forces in right away and just ignore the number of friction surfaces, in order to more easily compare when looking at both fixed and sliding calipers. for me, it's easier to think of a twin 36mm piston sliding caliper as effectively the same area as a 4 piston fixed caliper of the same piston size.

i suppose we can do it either way though, since the math works out the same in the end.
 
So just curious, I was always under the impression that 91/92 na cars had different brakes on the front than 93+ NA cars. That doesnt appear to be the case tho.
 
the pistons are the same size. the calipers on the earlier models are narrower though, accommodating up to a 25mm thick rotor, while the later gen can accommodate up to a 30mm rotor. the brackets are also made for smaller diameter rotors on the earlier cars as well.
 
Can anyone answer why there are different part numbers for the rear parking brake cables pre-92 and 92+? For example, pre-92 cites 46420-17050/46430-17050. Starting in 92, different part numbers show up: 46420-17070/46430-17070. No one ever seems to list this part when talking about switching over to 93+ turbo brakes...
 
Discussion starter · #40 ·
oneslug said:
Can anyone answer why there are different part numbers for the rear parking brake cables pre-92 and 92+? For example, pre-92 cites 46420-17050/46430-17050. Starting in 92, different part numbers show up: 46420-17070/46430-17070. No one ever seems to list this part when talking about switching over to 93+ turbo brakes...

The turbo rear rotors and caliper carriers are larger. Most likely the 1993+ cable is slightly shorter to account for this, however, the 1991/1992 cable will probably work fine on 1993+ brakes if you adjust it correctly.


Note that the 1993+ switchover for North American models happened in 1992 for Japan. So some new parts may be on North American 1992 models already depending on when they were built. In general, part switchovers can happen at any time during a model run if the new part is deemed to be more reliable or cheaper to produce.
 
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