Rallas

iTrader: (9)

This past week I installed identical pads and rotors on my dad's 99 non sport model and my 91 with 1.8 caliper brackets all around (NA 1.8 brackets but 1.6 calipers). I installed all new rotors and Carbotech XP10's in the front and XP8's in the rear on both cars for an upcoming track day. What gets me is that the brakes felt completely different between the two cars and leads me to my question. Are there any major changes between the NA 1.6 NA 1.8 and NB brake systems beyond the larger rotors?
The 99 brakes felt alot beter with more bite especially initial bite. Even once packing some heat into them they seemed to grab much harder than my NA brakes did.
Are there any major differences in the master cylinder bore diameter, boosters, caliper piston diameters or anything else that would cause the 99's brakes to have more of an assist? I think I have read that the later models have slightly larger caliper pistons, but I cannot find the thread again to see if it is big enough to change the hydraulic force multiplication with the same master.
I have a 96 brake master cylinder and booster from a car I parted 2 years ago, would it be worth swapping? Has anyone messed with this or am I just doing the usual over engineering?
Don't get me wrong, the brakes on the 91 work great, just not as great as the 99.

nitrodann

In australia the nb8b came with MUCh better brakes. bigger pistons and much larger rotors.

Dann

Rallas

iTrader: (9)

Does anyone have specs as to why the NB brakes would be better?

pimphand82

i remember reading that in the msm brake master has dual hydraulics. so i wouldnt be surprised if the nb's also uses the same master. nb's also have a diff. proportioning valve that balances out the force better front to back. combined with having larger rotors and calipers, nb should feel better.

richyvrlimited

iTrader: (1)

Does the NB have ABS?

ABS cars have more rear bias

thegrapist

The major difference is the newer the year the larger the master cylinder. (Na, 1.8 na, nb, then nb with sport brakes) A larger mc will give you a stiffer pedal but take more effort for the same hydraulic pressure. The proportioning valves are almost the same way with abs ones having the most rear bias. There's an article on Fm's page That's more detailed and informative

Rallas

iTrader: (9)

NB does not have ABS and they both have the exact same rotors and pads installed. I would understand a smaller MS piston, not bigger since the NB has a lot more bite with very little pedal pressure, where the NA seems to need more pedal effort to get the smae braking force. I was wondering about the proportioning valves. I don't think the differences in prop valve is causing what I am experiencing due to the fact that the differences between the different models is apparrant at higher brake pressures. I am noticing the big difference with the NB at initial bite and low pedal pressure.

I wish I had measured the Caliper pistons when I was replacing the pads/rotors on both cars.

pimphand82

brake fluid same? just going from dot 3-4 in my car i noticed a difference in pedal feel.

Rallas

iTrader: (9)

Same brake fluid, flushed and bled within 24hrs from each other.

thegrapist

http://forum.miata.net/vb/showthread.php?t=406624

and from the source:

http://forum.miata.net/vb/showthread.php?t=363284

Rallas

iTrader: (9)

Exactly what I was looking for! It explains perfectly the difference I felt between the two brake pedals.
The NB ones do have larger MC pistons (15/16) vs NA (7/8). The soffter pedal effort comes from almost twice as much assist from the booster on the larger piston.

I think I will try my brakes compared to his on track first before I make any changes to mine. Like Keith mentioned in his thread, the NB brakes might feel more modern and easy to use on the street, but they are harder to mudulate and will lock up easier.

Realy all I wanted to know with this thread is that I did not screw up the bedding proccess on my car and therefor ended up with brakes that were less than optimal compared to my dads. Especially when I paid $280 for the pads alone!!! That is an expensive bedding procedure error. Sorry, I am a cheap ***!

thegrapist

you're welcome. Now never doubt me again. But seriously, according to one of the dudes on m.net he said the larger master cylinders and matching boosters help create a stiffer pedal and make at the limit modulating easier. I have ss brake lines from the PO so i can't comment if they make a significant difference in pedal feel. Anyone want to chime in?

Rallas

iTrader: (9)

Well in the your first reply you only mentioned the larger pisto size, nothing about larger booster. Which would make sense! Thanks for the infor though. Its much better to hear from someone that has done it or done some real research than all the armchair engineering/racing that goes on.
Do you track your miata? The reason I ask is because modulating has 2 different meanings on the street and on the track.

sjmarcy

All Miatas are too front biased. Mostly two wheel braking with the rears sitting there as dazed and confused as a blonde bimbo during a Calculus test.

sixshooter

iTrader: (12)

Do you have any datalogs to support this?

Braineack

iTrader: (62)

(zack morris's phone)

I concur. With the statement.

thegrapist

I was joking, but yeah I don't have the first-hand experience to help you any further, I'd ask the tracktards on this forum for better brake advice. I have never tracked my (relatively stock) 99, I normally do track days (if and when I have money) in a rented SM or my brother's ms3 with hawk blues. The SM is (obviously) on 205 ra-1's and legal weight. The SM's 99 brakes are ok, (on ra-1's), but I still find myself locking up the fronts if I'm not paying close attention. The only thing I know for sure is the sport brakes on my 99 increase the bias to the rear, but I wish I had installed a proportioning valve when I installed them. Once I get a roll bar and my car is safe for a track day I think I'll be fine with my current setup and hawk blues.