NB8B brakes to NB8A

RS2000 · Postby **RS2000** » Mon Dec 14, 2015 2:44 pm

Question for those that have fitted NB8B brakes to an NB8A:

If you maintain the 8A master cylinder, is there much difference in pedal travel and/or feel ?
Cheers

Postby **beavis** » Mon Dec 14, 2015 3:33 pm

I remember reading somewhere that NB8A master was around 7/8" and NB8B was 15/16" ? (sorry for the americanised diameters, such is life)
If you want to know what size your master cylinder is, it is cast into the top of the master just under the reservoir.
Not sure if the boosters are the same?

The pistons are slightly larger (like 3mm?) in the 8B brakes, so you would end up with longer pedal feel if you retain the 8A master.

RS2000 · Postby **RS2000** » Mon Dec 14, 2015 3:51 pm

Thanks Beavis,
I realise all that, but I'd think that most people change to the larger discs & calipers, while leaving the smaller master.
I'm interested to know how much change there is to pedal operation & feel.
Cheers

RS2000 · Postby **RS2000** » Mon Dec 14, 2015 6:16 pm

Using the piston dia's shown here viewtopic.php?f=30&t=65932 the total increase in piston area for all four is 14%.
Doesn't sound much in theory, but I'm interested in real world opinions of pedal travel.

madjak · Postby **madjak** » Mon Dec 14, 2015 6:23 pm

Pedal travel will basically increase by the same percentage, which isn't much. Pad selection and how well you bleed your system probably has a bigger impact on pedal travel than the master cylinder.

Ice88 · Postby **Ice88** » Tue Dec 15, 2015 12:08 pm

The master cylinder on all NBs is the same at 15/16 from memory, its the booster that changes between the two.

There are two different model masters, one for ABS and one for non ABS. Both have the same bore.

RS2000 · Postby **RS2000** » Tue Dec 15, 2015 12:59 pm

My NB8A has a 7/8" M/C, which is 14.5% smaller in area to NB8B's. Not surprisingly, the total caliper piston area difference is the same.

Sorry to repeat, but anyone out there who has put NB8B calipers & discs on an NB8A notice or have a problem with increased pedal travel ?

Magpie · Postby **Magpie** » Wed Dec 16, 2015 8:18 am

NA6/8 at 44 lb/ft pedal pressure = 754/796 PSI brake line pressure. Booster is 4.74:1
NB at 44 lb/ft pedal pressure = 1038 PSI brake line pressure. Booster is 9.7:1
NB8B at 44 lb/ft pedal pressure = 638 PSI brake line pressure. Booster is 6.4:1

Pedal travel will not change much however EFFORT will due to the difference in booster ratio.

I went from NA6 to NB8B without a booster/master change and can't really remember if there was any appreciable change in travel/effort.

Can you get a test drive in a NB8B to feel what the OEM setup is like?

david_syd_au · Postby **david_syd_au** » Wed Dec 16, 2015 9:09 am

Modified my NB8A race car to use NB8B front brakes.
No noticeable change in travel or feel.

madjak · Postby **madjak** » Thu Dec 17, 2015 12:56 pm

Aren't the fronts the same cylinder size. It's only the rear that was increased.

RS2000 · Postby **RS2000** » Thu Dec 17, 2015 4:11 pm

Not according to this viewtopic.php?f=30&t=65932

StillIC · Postby **StillIC** » Thu Dec 17, 2015 6:12 pm

Magpie wrote:I went from NA6 to NB8B without a booster/master change and can't really remember if there was any appreciable change in travel/effort.

I did the opposite (NB8B to NA6) without a booster/master change, due to competition class restrictions, and also cannot remember feeling any difference in travel/effort. I don't even know what size master cylinder is in my car.