NB sport brakes

[speed]

Does anyone know the factory front/rear bias of the 270mm fronts and 276mm rear brakes?
Is the factory proportioning valve the same on any other non abs MX5?
Are the rear calipers the same as the 251mm rear brakes?
Thanks!

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[GR124]

I was asking similar questions, mainly relating to the rear calipers. looks like the NB8A rear caliper piston is 32mm and the NB8B has a 35mm
This may help?

viewtopic.php?f=87&t=74090&start=30

https://youtu.be/c_bnu3u5JJ0

[StanTheMan]

here is what Ive found. I'm in the exact same place AS SPEED,
Ive had NB8A brakes for about a decade. The reason Patchy is patchy is because she locked up the fronts after upgrading the fronts only.

Ive just fitted the rears NB8A. they are a little smaller than the sports pack speed has.

I think all NB8B's came with ABS which means they may not have a proportioning valve?

https://www.flyinmiata.com/tech/stock_bpv.php

have a read through this thread as well.
https://forum.miata.net/vb/showthread.php?t=217829

For me, I'll be looking for a 99 proportioning va;lve(i think). if all else fails I might have to upgrade the brake pads to see if that works.

[StanTheMan]

weve also established hat the wilwood valve is not an option for either of us.

[speed]

Thanks GR124 and STM.

I did come across those links in my searching yesterday.

GR124, it is good to know that the rear calipers from NB to NB sports are different. Now I won't buy the wrong parts.

Re the stock bias valves, I'd understand it easier if they quoted in front/rear percentages.

I know the NA is 80/20.
What I'd like to know is what is the percentage split on a 2002 NB with no ABS?
Is it 76/24?

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[RS2000]

I know the NA is 80/20.
What I'd like to know is what is the percentage split on a 2002 NB with no ABS?
Is it 76/24?

I think your maths is incorrect.
I have both NB8A & NB8B factory manuals downloaded, & the proportioning is the same for non abs models.
Front & rear pressure is the same up to 570psi (knee point). After this, the rear pressure is about 80 to 82% of the front pressure.
Your figures show the rear to be only 25-30% of the front.
Cheers

[speed]

I think your maths is incorrect.
I have both NB8A & NB8B factory manuals downloaded, & the proportioning is the same for non abs models.
Front & rear pressure is the same up to 570psi (knee point). After this, the rear pressure is about 80 to 82% of the front pressure.
Your figures show the rear to be only 25-30% of the front.
Cheers

Thank you very much RS2000.

So knee point is the point at which rear brake pressure needs to be controlled.

I wonder if the NA proportion is the same to knee point. If thats the case I only need the rear discs and calipers
Is that right?

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[StanTheMan]

I thought the NA8 were slightly more biast towards the rear (after the Knee point) than the NA6's

[speed]

I thought the NA8 were slightly more biast towards the rear (after the Knee point) than the NA6's

Maybe so but my booster, master, prop valve is later than NA6.
Worth finding out though as yours is still NA6.

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[RS2000]

Up to the knee point, the front/rear ratio is 1/1 (i.e. equal pressure f & r). I have no info on what the NA knee point psi is though.
There is a big tolerance on the NB f/r ratio after the 569psi knee point. The manuals show the rear pressure to be 74% to 87% (average 80-81) of the front pressure, once the pressure exceeds 569psi.

[StanTheMan]

https://www.flyinmiata.com/tech/stock_bpv.php

the sizing is different between the 89-93 & 93&98

prop valves.JPG

I wonder if the B" value is the knee point?

[StanTheMan]

Ohh I think I have it figured out now with those numbers

A, is the knee point 427 (NA6) psi up to which where pressure is the same
B,maximum Psi?
B" is 597 which is what the rear is when the front brake is at 1000 psi

so that would mean the rear pressure on the NA6 would be about 60% of the front?

I kind of find that really hard to believe My rears lasted 25 years & 300K km....while the front were changed on the regular basis....

[speed]

so that would mean the rear pressure on the NA6 would be about 60% of the front?

I kind of find that really hard to believe My rears lasted 25 years & 300K km....while the front were changed on the regular basis....

Yes but in normal driving I brake scarcely, basically when coming to a set of traffic lights or if someone pulls out in front of me.
Weight distribution under inertia would also play a part. The fronts see more action regardless of the graphs and tables.

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[RS2000]

My info, supposedly for 98-05, is the same as 94-97, & very similar to 2002 non abs, on Stan's table:

IMG 98-2005 PV.pdf

[StanTheMan]

cheers RS2000

I' think I know what I'll be sourcing now