I need better brakes! - Page 2

karl · 05-15-2009, 12:32 PM

91-92 turbo and all years N/A share the same rear rotors, calipers and pads. 91 turbos have 2-piston calipers, while the NA uses single piston, but both use the same rotors. the NA proportioning valve is also less aggressive (meaning it lowers rear pressure earlier and at a higher rate than the turbo so it uses the rear brakes less than the turbo does, but also has less weight over the rear axle than the turbo).

both share a 7/8" bore master cylinder.

93+ turbo brake rotors are slightly larger diameter and also are thicker, both front and rear. they use the same piston area in the front as the 91t, but have slightly larger rear caliper pistons, resulting in a little more rear brake bias.

the also move up to a 15/16" master cylinder bore.

i know that some manufacturers achieve the brake bias through the proportioning valve only. an example of this is GM- they use the same piston area at all 4 corners, and create the bias front to rear through the prop valve (and sometimes by differential bore master cylinders- meaning the bore for the rear brake circuit is larger than the bore for the front).

toyota designs the brake bias into the caliper piston area and rotor effective diameter. the master cylinders are uniform bore throughout, and the brake bias occurs from the piston area differential front to rear. the "proportioning valve" doesn't really do anything bias-wise except reduce pressure to the rear brakes under heavy braking to prevent the rears from locking up first. in fact, the prop valve doesn't do anything until about 800psi of line pressure, at which point it allows the rear pressure to increase at a lower rate per lb of pedal pressure than the front, increasing front bias the closer you get to lockup for stability's sake.

there are 4 master cylinder sizes that will fit the MR2 as a direct bolt-on, ranging from the stock 7/8" (14/16) to 17/16" (1 1/16") in 1/16" increments.

14/16" is stock for 91-92t and all N/A
15/16" is stock for 93t+
16/16" is stock on the tacoma and mk3 supra
17/16" is stock ONLY on the mid 90's 4runner with 4-wheel ABS

match ABS to ABS and non-ABS to non-ABS and each one is a direct bolt-on replacement. the only weird one is the 4runner with 2-wheel ABS which is identical to a non-abs master cylinder.

i'm using the 17/16 on my 91t and the pedal feel is fantastic, but the pedal does not move. often, these larger MCs will be easier to find in a pinch and cheaper as well.

larger master cylinder bore means LESS pressure generated for a given pedal effort, so braking effort is increased, but not to the point where it feels like the brakes are unassisted anymore.

if you can't tell, i've done a lot of brake research over the years

GENESIS · 05-19-2009, 09:08 PM

Quote:

Originally Posted by Jon3sgte

i just did the brakes on all 4 corners and my pedal still feels mushy. nowhere near like i think it should. I bled them twice and even took it to Big O to have them bleed them but the same result. Is this normal for the NA? this is my 3rd NA and I dont remember having this problem before. The pedal wont go to the floor but to me feels like it goes too far. Will braided lines help this? Switching to DOT 4 fluid? Rebuild kit for the rotors? turbo master cylinder? I am running slotted rotors. The car stops but not like it should.

assuming you bleeded it right check the master cylinder first,i had the same problem on my miata and found out that one of the piston on the front calipers were stuck.if anything upgrade to better pads and tires stock mr2 pads are ok but most occasions when i tear it up in the mountain I end up failing the stock pads especially on track days it will last me only one lap
ceramic or not.

Jon3sgte · 05-20-2009, 12:16 PM

i'm going to look into a new cylinder. is there a way to check the calipers?

Jon3sgte · 05-20-2009, 02:13 PM

Will my 91 NA resivoir work with any of those MC's listed above?

TomsMR2 · 05-21-2009, 07:44 AM

Quote:

Originally Posted by karl

the NA proportioning valve is also less aggressive (meaning it lowers rear pressure earlier and at a higher rate than the turbo so it uses the rear brakes less than the turbo does, but also has less weight over the rear axle than the turbo).

its not less aggressive. turbo brakes have more piston surface area.. you have to change the prop valve to get properly balanced brakes. if you have turbo brakes, you need a turbo prop valve for the car to properly stop. if you have na brakes, you similarly need an na prop valve. switching them up will result in worse than stock braking performance!

Quote:

i'm using the 17/16 on my 91t and the pedal feel is fantastic, but the pedal does not move. often, these larger MCs will be easier to find in a pinch and cheaper as well.

im using it too.. after 2 years i realize im really just pushing my foot real hard for the same amount of braking. its unnecessary, and wasted effort. i strongly dont recommend it to anyone for any reason (on stock brakes). you just dont need that much modulation!

420mr2 · 06-10-2009, 04:07 AM

Quote:

Originally Posted by Jon3sgte

i just did the brakes on all 4 corners and my pedal still feels mushy. nowhere near like i think it should. I bled them twice and even took it to Big O to have them bleed them but the same result. Is this normal for the NA? this is my 3rd NA and I dont remember having this problem before. The pedal wont go to the floor but to me feels like it goes too far. Will braided lines help this? Switching to DOT 4 fluid? Rebuild kit for the rotors? turbo master cylinder? I am running slotted rotors. The car stops but not like it should.

The same exact thing happened to me, I have a 1991 na with about 225k miles. I had to replace the ball joints, and ended up undoing the brake lines to get to the ball joints (which was a mistake) that led to me getting a bunch of air in my lines, and afterwards my brakes were terrible. then I bled them thoroughly, and my brakes worked perfect.

however, a few weeks later they went bad again, and this time it was worse. so i bled them again, which didn't work, then i bled them again, and it still didn't work. I went to autozone, and basically they said it's sticky calipers or the master cylinder. I doubt that it's sticky calipers, because the pedal goes all the way to the floor and i think sticky calipers would mean my brakes would come and go, but with the master cylinder, it seems i would consistenly have no brakes (which matches my symptoms much better)

anyway, I heard you can rebuild a master cylinder, any ideas on that?

or any more advice for me and Jon3sgte?

420mr2 · 06-10-2009, 04:13 AM

DAMN! just wrote a message and somehow I lost it....

wait...nevermind I see it's right up there ^^^

anyway...forgive me for being a noob on the forums...but I am getting better :P lol

KaDuWin · 06-10-2009, 09:28 AM

I hear you can rebuild it but I didn't find any kits for building them. I have a 91 and apparently Toyota used 3 or 4 different master cylinders on the MR1 from 91-95 models on the NA and Turbo. If it is the master cylinder I recommend you got to your local Toyota dealership match the VIN and get the part through them, that is what I had to do after a week of intense searching I was forced to get the OEM factory part.

Jon3sgte · 06-11-2009, 10:37 AM

a new MC is only $60 from autozone. Will our resivoirs work with any of the MC's listed above?

KaDuWin · 06-11-2009, 03:08 PM

I don't know, I wish I could say for sure but that is part of the issue with the MC for the MK2. Toyota used different MCs in 1991 as well as other years which are NOT all interchangeable from year to year.

Believe me I found a couple of places on line that carried MC for my MK2 but the issue was making sure that it was the right one for my year. After a lot of research I learned that Toyota used a particular design for the MC for MK2s produced from 1990 through Sept. of 1991, and then started using a different design from Sept through 1992 if my memory serves me right. Unfortunately they continued to change the MC design more from 92-95. If you have a 93 or 94-95 you will probably have an easier time than I did finding the right MC since Toyota became a bit more standardized with their usage of the MCs in the later years of production.

Redstar · 06-11-2009, 03:34 PM

Talk to Aaron, pay the money for a new OE master cylinder. It will come with a new resivoir + they fit correctly and rarely fail.

KaDuWin, see Karl's post at the top of the page. I can verify that a 94+, turbo, non-abs, MC will work correctly on an early '92 (prod date 10/91), NA, non-abs chassis. And just from this thread, Karl is using a mid 90's 4-runner MC on his '91T.

Swapping MC's is a very common MR2 brake mod, not sure where you ran into so much trouble.

Jon3sgte · 06-11-2009, 04:07 PM

i was just wondering if the resivoirs interchange. when i looked up new MC's online they alll showed the part without a resivoir.

KaDuWin · 06-11-2009, 08:31 PM

I wasn't disputing that it wouldn't work with the 94 or any other model accept the 91. The 1991 model produced from Jan of 1990-Oct of 1991 is the only model I was referring to in which I said it was rare to find the correct MC. According to two dealerships in my area both said that there are only 13 correct factory OEM MC left in the US. I bought one of them so technically there are 12. After searching high and low on the internet and talking to numerous auto parts websites, no one said that they had the correct MC for my early model. I have chassis #150 which was built Jan of 1990 so I missed the Oct 91 cut off date which you mentioned, which is the same thing which I was referring to in previous posts. That is why I had as much trouble as I did, my car is an extremely early model chassis #150.

Jon3sgte · 06-11-2009, 08:35 PM

i'll probably go with one of the non mr2 MC's listed above for the better pedal feel and some braided lines. i can probably find a resivoir to fit from a junk yard. i wonder why they changed MC's so much.

328FTW · 06-11-2009, 08:42 PM

You could use the whole master and the booster off another year car, at worst it means drilling a couple holes and maybe rerouting some lines. I change this stuff all the time and it doesn't take that much work to swap and saves the hassle of part tracking. Also given the amount of toyota stuff that matches up there is probably a celica or something with a MC that fits under a different number. Junkyards are a good place to try that sort of stuff out.

KaDuWin · 06-12-2009, 09:18 AM

Well they most likely changed the MC so much because every couple of years they kept making modifications to the MK2, for instance the LSD was modified and made much better in 93+, the 5 speed had a shorter throw and double pack synchros, in the 94 the cars got 5 more BHP, different asthetics, etc. So it was probably just on their list of "things to upgrade." You know how Toyota is, they are always trying to improve what they already got.

KaDuWin · 06-12-2009, 09:21 AM

Thanks I wish I had known, all that time I had speaking to Toyota and getting the same answer that because my car was produced so early, that the only MC that would was this really rare one which I got from Toyota. Originally I wanted to just swap out the NA MC to a Turbo MC and upgrade all of the brakes but those plans fell through LOL.

Redstar · 06-12-2009, 10:36 AM

Wierd, what was the part number of the MC you ended up with?

Did you buy it from Aaron or your local dealer? I know my local dealer has tired to pull the "it's discontinued" or "you have to buy the whole assebmly" BS when I was looking for a couple odd parts.

You jumped around a bit on your dates, is the cut off September or October of '91?

KaDuWin · 06-12-2009, 02:54 PM

I bought it from a local dealer, they didn't try and pull the "its discounted" routine with me or anything else. I don't think I still have the part number any more however, I will try to find it. They just said it was the first gen of MCs that Toyota used on the MR2 MK2, and after Oct of 91 they started to use a different (more common/available) MC. But I got that same story from 1 other dealer, and an after market website online. I have a very early chassis number, so I guess I would naturally have the most difficult time finding parts for my car. My chassis number is #150 and was built in the second week of Jan in 1990.

Redstar · 06-12-2009, 04:37 PM

Mine was built in October of 1991. I recently swapped out my original master cylinder for a brand new OEM 93+ turbo master cylinder. It works fine.

I just looked at Rock auto and Napa's websites, they list the same master cylinder's for 91 and 94 MR2's with 2.2L engines.

Browse around cardomain, there's a number of 91's with newer master cylinders.

Are you trying to say the master cylinder originally on your car is hard to find, or are you saying the master cylinder originally on your car is the only one that fits?

06-11-2009, 04:07 PM	#32 (permalink)
Jon3sgte Cage Fighter Join Date: Nov 2007 Location: Tucson, AZ Posts: 186 Thanks: 8 Thanked 1 Time in 1 Post iTrader Rating: (1/100% )	i was just wondering if the resivoirs interchange. when i looked up new MC's online they alll showed the part without a resivoir. Last edited by Jon3sgte; 06-11-2009 at 08:32 PM..

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05-15-2009, 12:32 PM	#21 (permalink)
karl slowbie Join Date: May 2006 Location: robbinsdale, MN Posts: 546 Thanks: 2 Thanked 54 Times in 42 Posts iTrader Rating: (0/0% )	91-92 turbo and all years N/A share the same rear rotors, calipers and pads. 91 turbos have 2-piston calipers, while the NA uses single piston, but both use the same rotors. the NA proportioning valve is also less aggressive (meaning it lowers rear pressure earlier and at a higher rate than the turbo so it uses the rear brakes less than the turbo does, but also has less weight over the rear axle than the turbo). both share a 7/8" bore master cylinder. 93+ turbo brake rotors are slightly larger diameter and also are thicker, both front and rear. they use the same piston area in the front as the 91t, but have slightly larger rear caliper pistons, resulting in a little more rear brake bias. the also move up to a 15/16" master cylinder bore. i know that some manufacturers achieve the brake bias through the proportioning valve only. an example of this is GM- they use the same piston area at all 4 corners, and create the bias front to rear through the prop valve (and sometimes by differential bore master cylinders- meaning the bore for the rear brake circuit is larger than the bore for the front). toyota designs the brake bias into the caliper piston area and rotor effective diameter. the master cylinders are uniform bore throughout, and the brake bias occurs from the piston area differential front to rear. the "proportioning valve" doesn't really do anything bias-wise except reduce pressure to the rear brakes under heavy braking to prevent the rears from locking up first. in fact, the prop valve doesn't do anything until about 800psi of line pressure, at which point it allows the rear pressure to increase at a lower rate per lb of pedal pressure than the front, increasing front bias the closer you get to lockup for stability's sake. there are 4 master cylinder sizes that will fit the MR2 as a direct bolt-on, ranging from the stock 7/8" (14/16) to 17/16" (1 1/16") in 1/16" increments. 14/16" is stock for 91-92t and all N/A 15/16" is stock for 93t+ 16/16" is stock on the tacoma and mk3 supra 17/16" is stock ONLY on the mid 90's 4runner with 4-wheel ABS match ABS to ABS and non-ABS to non-ABS and each one is a direct bolt-on replacement. the only weird one is the 4runner with 2-wheel ABS which is identical to a non-abs master cylinder. i'm using the 17/16 on my 91t and the pedal feel is fantastic, but the pedal does not move. often, these larger MCs will be easier to find in a pinch and cheaper as well. larger master cylinder bore means LESS pressure generated for a given pedal effort, so braking effort is increased, but not to the point where it feels like the brakes are unassisted anymore. if you can't tell, i've done a lot of brake research over the years

05-20-2009, 12:16 PM	#23 (permalink)
Jon3sgte Cage Fighter Join Date: Nov 2007 Location: Tucson, AZ Posts: 186 Thanks: 8 Thanked 1 Time in 1 Post iTrader Rating: (1/100% )	i'm going to look into a new cylinder. is there a way to check the calipers?

05-20-2009, 02:13 PM	#24 (permalink)
Jon3sgte Cage Fighter Join Date: Nov 2007 Location: Tucson, AZ Posts: 186 Thanks: 8 Thanked 1 Time in 1 Post iTrader Rating: (1/100% )	Will my 91 NA resivoir work with any of those MC's listed above?

06-10-2009, 04:13 AM	#27 (permalink)
420mr2 No Skills Join Date: Aug 2008 Location: Diamond Bar, CA Posts: 24 Thanks: 0 Thanked 0 Times in 0 Posts Blog Entries: 3 iTrader Rating: (0/0% )	DAMN! just wrote a message and somehow I lost it.... wait...nevermind I see it's right up there ^^^ anyway...forgive me for being a noob on the forums...but I am getting better :P lol

06-10-2009, 09:28 AM	#28 (permalink)
KaDuWin KaDuWin Join Date: Mar 2005 Posts: 163 Thanks: 15 Thanked 6 Times in 6 Posts iTrader Rating: (0/0% )	I hear you can rebuild it but I didn't find any kits for building them. I have a 91 and apparently Toyota used 3 or 4 different master cylinders on the MR1 from 91-95 models on the NA and Turbo. If it is the master cylinder I recommend you got to your local Toyota dealership match the VIN and get the part through them, that is what I had to do after a week of intense searching I was forced to get the OEM factory part.

06-11-2009, 10:37 AM	#29 (permalink)
Jon3sgte Cage Fighter Join Date: Nov 2007 Location: Tucson, AZ Posts: 186 Thanks: 8 Thanked 1 Time in 1 Post iTrader Rating: (1/100% )	a new MC is only $60 from autozone. Will our resivoirs work with any of the MC's listed above?

06-11-2009, 03:08 PM	#30 (permalink)
KaDuWin KaDuWin Join Date: Mar 2005 Posts: 163 Thanks: 15 Thanked 6 Times in 6 Posts iTrader Rating: (0/0% )	I don't know, I wish I could say for sure but that is part of the issue with the MC for the MK2. Toyota used different MCs in 1991 as well as other years which are NOT all interchangeable from year to year. Believe me I found a couple of places on line that carried MC for my MK2 but the issue was making sure that it was the right one for my year. After a lot of research I learned that Toyota used a particular design for the MC for MK2s produced from 1990 through Sept. of 1991, and then started using a different design from Sept through 1992 if my memory serves me right. Unfortunately they continued to change the MC design more from 92-95. If you have a 93 or 94-95 you will probably have an easier time than I did finding the right MC since Toyota became a bit more standardized with their usage of the MCs in the later years of production.

06-11-2009, 03:34 PM	#31 (permalink)
Redstar My other cars are jealous Join Date: Feb 2007 Location: Bellingham, WA Posts: 439 Thanks: 21 Thanked 40 Times in 29 Posts iTrader Rating: (12/100% )	Talk to Aaron, pay the money for a new OE master cylinder. It will come with a new resivoir + they fit correctly and rarely fail. KaDuWin, see Karl's post at the top of the page. I can verify that a 94+, turbo, non-abs, MC will work correctly on an early '92 (prod date 10/91), NA, non-abs chassis. And just from this thread, Karl is using a mid 90's 4-runner MC on his '91T. Swapping MC's is a very common MR2 brake mod, not sure where you ran into so much trouble.

06-11-2009, 08:31 PM	#33 (permalink)
KaDuWin KaDuWin Join Date: Mar 2005 Posts: 163 Thanks: 15 Thanked 6 Times in 6 Posts iTrader Rating: (0/0% )	I wasn't disputing that it wouldn't work with the 94 or any other model accept the 91. The 1991 model produced from Jan of 1990-Oct of 1991 is the only model I was referring to in which I said it was rare to find the correct MC. According to two dealerships in my area both said that there are only 13 correct factory OEM MC left in the US. I bought one of them so technically there are 12. After searching high and low on the internet and talking to numerous auto parts websites, no one said that they had the correct MC for my early model. I have chassis #150 which was built Jan of 1990 so I missed the Oct 91 cut off date which you mentioned, which is the same thing which I was referring to in previous posts. That is why I had as much trouble as I did, my car is an extremely early model chassis #150.

06-11-2009, 08:35 PM	#34 (permalink)
Jon3sgte Cage Fighter Join Date: Nov 2007 Location: Tucson, AZ Posts: 186 Thanks: 8 Thanked 1 Time in 1 Post iTrader Rating: (1/100% )	i'll probably go with one of the non mr2 MC's listed above for the better pedal feel and some braided lines. i can probably find a resivoir to fit from a junk yard. i wonder why they changed MC's so much.

06-11-2009, 08:42 PM	#35 (permalink)
328FTW Crazy Nasty Honey Badger Join Date: Aug 2008 Location: New Zealand Posts: 5,236 Thanks: 24 Thanked 266 Times in 239 Posts My Google Map iTrader Rating: (1/100% )	You could use the whole master and the booster off another year car, at worst it means drilling a couple holes and maybe rerouting some lines. I change this stuff all the time and it doesn't take that much work to swap and saves the hassle of part tracking. Also given the amount of toyota stuff that matches up there is probably a celica or something with a MC that fits under a different number. Junkyards are a good place to try that sort of stuff out.

06-12-2009, 09:18 AM	#36 (permalink)
KaDuWin KaDuWin Join Date: Mar 2005 Posts: 163 Thanks: 15 Thanked 6 Times in 6 Posts iTrader Rating: (0/0% )	Well they most likely changed the MC so much because every couple of years they kept making modifications to the MK2, for instance the LSD was modified and made much better in 93+, the 5 speed had a shorter throw and double pack synchros, in the 94 the cars got 5 more BHP, different asthetics, etc. So it was probably just on their list of "things to upgrade." You know how Toyota is, they are always trying to improve what they already got.

06-12-2009, 09:21 AM	#37 (permalink)
KaDuWin KaDuWin Join Date: Mar 2005 Posts: 163 Thanks: 15 Thanked 6 Times in 6 Posts iTrader Rating: (0/0% )	Thanks I wish I had known, all that time I had speaking to Toyota and getting the same answer that because my car was produced so early, that the only MC that would was this really rare one which I got from Toyota. Originally I wanted to just swap out the NA MC to a Turbo MC and upgrade all of the brakes but those plans fell through LOL.

06-12-2009, 10:36 AM	#38 (permalink)
Redstar My other cars are jealous Join Date: Feb 2007 Location: Bellingham, WA Posts: 439 Thanks: 21 Thanked 40 Times in 29 Posts iTrader Rating: (12/100% )	Wierd, what was the part number of the MC you ended up with? Did you buy it from Aaron or your local dealer? I know my local dealer has tired to pull the "it's discontinued" or "you have to buy the whole assebmly" BS when I was looking for a couple odd parts. You jumped around a bit on your dates, is the cut off September or October of '91?

06-12-2009, 02:54 PM	#39 (permalink)
KaDuWin KaDuWin Join Date: Mar 2005 Posts: 163 Thanks: 15 Thanked 6 Times in 6 Posts iTrader Rating: (0/0% )	I bought it from a local dealer, they didn't try and pull the "its discounted" routine with me or anything else. I don't think I still have the part number any more however, I will try to find it. They just said it was the first gen of MCs that Toyota used on the MR2 MK2, and after Oct of 91 they started to use a different (more common/available) MC. But I got that same story from 1 other dealer, and an after market website online. I have a very early chassis number, so I guess I would naturally have the most difficult time finding parts for my car. My chassis number is #150 and was built in the second week of Jan in 1990.

06-12-2009, 04:37 PM	#40 (permalink)
Redstar My other cars are jealous Join Date: Feb 2007 Location: Bellingham, WA Posts: 439 Thanks: 21 Thanked 40 Times in 29 Posts iTrader Rating: (12/100% )	Mine was built in October of 1991. I recently swapped out my original master cylinder for a brand new OEM 93+ turbo master cylinder. It works fine. I just looked at Rock auto and Napa's websites, they list the same master cylinder's for 91 and 94 MR2's with 2.2L engines. Browse around cardomain, there's a number of 91's with newer master cylinders. Are you trying to say the master cylinder originally on your car is hard to find, or are you saying the master cylinder originally on your car is the only one that fits?