Given that brakes are primary safety items I figured potential buyers might also need a thread to help identify some things to look out for when departing from what Mazda engineers originally intended in the original design of NA6 or NA8 brakes.
Used Brake Hose
Sellers may not be able to vouch for age and condition of used brake hose. Also sport brake calipers are bit of a stretch for original hose at front. All up good excuse for right length ADR approved braided lines.
http://mx5cartalk.com/forum/viewtopic.php?f=30&t=52520
Rim clearance
Sport brakes factory fitted inside 16" rims and factory Enkie 15" rims. They appear not to fit in 14" rims and some 15" rims.
http://mx5cartalk.com/forum/viewtopic.php?f=30&t=33711&start=15
http://mx5cartalk.com/forum/viewtopic.php?f=30&t=45553
Space Saver
Sport brakes also need a larger diameter space saver spare also....one shown here http://mx5cartalk.com/forum/viewtopic.php?p=708307#p708307
Dust Shields
I have fitted sport brakes ok to an NA8 just pushed the dust shields sideways a little to clear the disc. On an NA6 given their much smaller diameter shields a little more elbow grease is required. http://omgpham.com/mx-5-brake-upgrade
Rear Brake Bias
I found the NA8 valve with these brakes (the one with the orange band) to be ok but still there is room for a valve with more rear bias as I still lock the fronts first even with extra grip from semi slicks at track temperature. Brake control is inherently more stable with a bit of front bias, but the NA6 brake proportioning valve is overly front biased in combination with sport brakes so definitely needs to be changed out. Some info:
http://www.flyinmiata.com/tech/stock_bpv.php
http://www.cardomain.com/ride/123711/1990-mazda-miata-mx-5/page-11/
Master Cylinders and Brake Boosters
The NA6, NA8 and NB8a master cylinder and boosters deliver adequate pressure to the larger diameter calipers of sport brakes but because of the smaller bore 7/8 " verses 15/16" is unable to deliver as much brake fluid required by the larger diameter calipers. Therefore the system is less tolerant to overheated fluid, entrained air, moisture, soggy brake hoses etc (more chance of running out of brake pedal). Suggests DOT 4 or maybe DOT 5.1 and more regular fluid changes required. Also another excuse for adding stiffer braided lines ! Do not use DOT 5 Silicon fluid as it is too spongy.
Interesting info on the subject. http://forum.miata.net/vb/showthread.php?t=363284
Light Vehicle Code of Practice
http://www.infrastructure.gov.au/roads/vehicle_regulation/bulletin/pdf/NCOP5_Section_LG_Brakes_V2_01Jan2011.pdf
After market adjustable brake proportioning valves are not recommended for road use. They can not be legally certified by an engineer because it is clearly foreseeable to the engineer that the brakes are simply adjustable to a different specification.
Use of OEM non-adjustable brake proportioning valves can be certified by an engineer if compliance required.
Use of NB8b brakes with NA6/8 master cylinders and boosters can also be certified by an engineer if compliance required.
Engineer certification will definitely not be required if non-ABS NB8b master cylinder, booster and proportional valve also used. These are not available on ADM MX5's though.
Trust this assists.......Feedback or questions welcome to build thread.
Keith
