Russell Brakes for the Mazda Miata: Which Parts Fit

By Core Brake Parts Tech Team — Circleville, OH warehouse

Russell makes one part we carry for the Mazda Miata: the Russell Street Legal stainless braided brake line kit, part number 685500, for the 1990-1997 first-generation (NA) Miata. It replaces the factory rubber flex hoses at the wheels, and Russell states its Street Legal hoses meet the federal brake hose standard, FMVSS 106. If you own a 1998 or later Miata, this kit is not listed for your car.

What the Russell 685500 kit is, and which Miatas it fits

The Russell 685500 street legal braided brake line kit for the 1990-1997 Miata is a set of pre-assembled flexible brake hoses built for the NA chassis. Russell describes its Street Legal brake hose kits as stainless steel braided hose with zinc-plated fittings, factory assembled for bolt-on installation, and says they meet the guidelines of the Department of Transportation FMVSS-571.106 requirements. Russell also notes its brake hose kits are for stock applications unless noted otherwise, which matters on a Miata because so many of them have been modified.

Russell is part of the Edelbrock Group, and the brand's core business is fluid transfer: hoses, hose ends and fittings for fuel, brake, clutch and transmission systems. That is why the Russell name shows up on brake lines rather than on pads or rotors. For the Miata, the braided line kit is the Russell part that fits.

Before ordering, confirm your car is stock at the brakes. If it has had a big brake kit, aftermarket calipers or suspension changes that relocate brackets, the hose length and fitting ends may not match what the kit was designed around.

How the NA Miata brake system works, and where the hoses sit

The NA Miata uses disc brakes at all four corners. Mazda's own parts catalog lists rear caliper pad sets for these years, so every wheel has a caliper that moves with the suspension. Hard steel lines run along the body, and a short flexible hose bridges the gap between the body and each caliper so the wheel can steer and travel up and down.

Those flexible hoses are the weak point on an old car. A rubber hose swells slightly each time you press the pedal, and that swelling is fluid volume that goes into stretching the hose instead of clamping the pads. As rubber ages it softens, cracks and can deteriorate internally. On a car built between 1990 and 1997, a hose that has never been changed is decades old.

A braided hose uses a smooth inner liner wrapped in stainless steel braid. The braid limits how much the hose can expand under pressure, which is the point Russell makes when it says replacing the rubber hose reduces brake hose expansion for more consistent braking. The result drivers notice is a firmer pedal with less travel before the brakes bite.

Symptoms that point to worn Miata brake hoses

• Soft or spongy pedal after a full bleed. If fresh fluid and a proper bleed have not firmed the pedal up, hose expansion is a likely cause.
• Cracks, bulges or wet spots on the hose. Turn the wheel to full lock and look at each hose with a flashlight. Any bulge or seepage means replace it now.
• A pull to one side or a wheel that drags. A hose that has deteriorated inside can act like a one-way valve and hold pressure on one caliper after you release the pedal. The wheel runs hot and the car pulls.
• Pedal that fades on a spirited drive or track day. Heat makes old rubber softer. Fade can also come from fluid or pads, so check those too.

Diagnose in order: check fluid level and condition, bleed the system, then inspect the hoses. If one caliper is dragging, crack its bleeder with the car safely on stands. If the wheel frees up, pressure was trapped upstream, and the hose is the usual suspect.

What street legal and the DOT marking actually mean

Federal Motor Vehicle Safety Standard 106 exists to reduce deaths and injuries from brake failure caused by hose or hose assembly rupture. It sets performance tests that a hydraulic brake hose assembly has to pass. Two examples from the regulation text:

• Whip resistance: the assembly must not rupture when run continuously on a flexing machine for 35 hours.
• Tensile strength: the assembly must withstand a 325 pound pull on a slow pull test, and 370 pounds on a fast pull test, without the hose separating from its end fittings.

The standard also governs labeling. A hydraulic brake hose assembly sold on its own is labeled with a band around the hose, or on the end fittings at the manufacturer's option, in block capital letters at least one-eighth of an inch high. The DOT symbol in that marking is the manufacturer's certification that the product conforms to the applicable safety standards. When you unbox a braided hose kit for a street car, look for that marking. Plenty of generic braided hoses carry no certification at all, and the stainless braid on the outside tells you nothing about how the hose is built inside.

Installing the kit: what to replace and what to watch

This is a moderate DIY job for someone who has bled brakes before. Each hose connects to a hard line at the body and to the caliper at the wheel. Use a flare-nut wrench on the hard-line fitting, because an open-end wrench rounds old fittings quickly. Soak the fittings with penetrant the day before on a car that has seen winter roads.

• Use new sealing washers wherever a banjo bolt meets the caliper, and follow the tightening specification in the factory service manual. Do not guess at torque on brake fittings.
• Check clearance at full lock and full droop. Turn the steering stop to stop and cycle the suspension. The hose must not rub the tire, wheel or suspension arms.
• Bleed the whole system. Opening every hose connection lets air into all four corners. A common sequence is to start at the wheel farthest from the master cylinder and work toward the closest, but confirm the order in the service manual.
• Use the fluid grade Mazda specifies for your car. It is marked on the master cylinder reservoir cap and listed in the owner's manual. Do not mix a silicone-based DOT 5 fluid into a system built for glycol fluid.

Fresh fluid is worth doing at the same time for a practical reason. FMVSS 116 sets a minimum boiling point of 401 F for new DOT 3 fluid and 446 F for DOT 4, but the wet boiling point minimums, measured after the fluid has taken on moisture, drop to 284 F and 311 F. Old fluid in a thirty-year-old car is closer to the wet number than the dry one.

Other Miata brake parts to pair with new lines

If the hoses are original, the pads, rotors and hardware are worth inspecting while the wheels are off. For NA and early NB cars we carry the EBC USR slotted front rotor set for the 1990-1994 Miata 1.6 and the EBC BSD V-slot front rotor set for the 1994-2001 Miata. Note the split at 1994: the 1.6 liter and 1.8 liter cars use different front rotor listings, so match the rotor to your model year and engine.

For track use on 1995-2005 cars, the Wilwood Forged Dynalite front big brake kit is a larger step. A big brake kit changes caliper mounting, so confirm the hose routing and fittings for that setup rather than assuming a stock-application hose kit carries over. You can also browse all brake lines, brake pads and brake hardware kits.

Frequently Asked Questions

Does the Russell 685500 kit fit a 1999 Miata?

No. Russell 685500 is listed for the 1990-1997 Miata MX-5 only. The 1999 and later cars are a different generation, so check our brake line collection for a listing that names your year.

Are Russell braided brake lines legal for street use?

Russell states its Street Legal brake hose kits meet the requirements of FMVSS 106, the federal standard for brake hoses. Look for the DOT marking on the hose band or fitting when you install them.

Will braided lines alone fix a spongy pedal?

Only if hose expansion is the cause. Air in the system, old fluid, a worn master cylinder or pads with poor contact can all cause a soft pedal. Bleed with fresh fluid first, then decide.

Do I need to bleed all four corners after installing the kit?

Yes. Every hose is opened, so air gets into each caliper circuit. Bleed the whole system and check for a firm pedal before driving.

Does Russell make brake pads or rotors for the Miata?

Not that we carry. Russell's product line is hoses, fittings and fluid transfer parts. For pads and rotors on the Miata, look at the EBC and Hawk parts listed for your model year.

Sources

1. Russell Performance - Street Legal Brake Hose Kits - construction, FMVSS-571.106 statement, reduced hose expansion, stock-application note
2. Edelbrock Group - Russell Performance - Russell as part of Edelbrock Group, fluid transfer product line
3. 49 CFR 571.106, FMVSS 106 Brake Hoses (LII, Cornell Law) - purpose, whip and tensile tests, labeling band and DOT certification
4. 49 CFR 571.116, FMVSS 116 Brake Fluids (LII, Cornell Law) - DOT 3 and DOT 4 dry and wet boiling point minimums
5. Mazda Parts Online - MX-5 Miata rear caliper pad set - NA Miata uses rear disc brakes with calipers