Rear brake caliper piston for Mazda Miata NA/NB

In between Mazda’s genuine parts you cannot find the caliper piston for Miata as a single item.
When you overhaul the front and rear brake caliper and you find rust the maker suggests the exchange of the caliper ASSY even if it is expensive.

When overhauling the brakes of Mazda Miata NA and NB the caliper piston has to be disassembled.
When we disassemble the brake caliper we can notice that the piston is quite rusty.

Maruha has added the front brake caliper for NA, NB (early model), NB (later model) into its line-up.

The rear side is linked with the piston inner part’s hand brake which makes it a complex construction.

For this reason, we cannot carry out the same simple machining as in the case of the front.

Hybrid piston

It has become possible to purchase the hybrid piston with the stainless sleeve.
This hybrid piston can resist rust better than the genuine part.

Rear side, caliper piston cleaning limits

If you wash the piston properly and clean it with oil the rust will disappear.

After the rust has been removed the piston looks like a lunar crater. This will later be the reason for the fluid leak. Because of the piston the fluid that wasn’t leaking before the O/H starts leaking after the O/H. However, there are cases when people don’t carry out O/H at all. Because of the rust the piston starts sticking and this influences the brakes in a negative way. For this reason, it is important to carry out the caliper’s O/H temporarily.

The blind spots at the time of the pads’ exchange

The caliper’s disassembly O/H starts with the brake pads’ exchange.
Because of the friction the pads become thin. They have to be exchanged with new thick pads. At this time we have to thrust the piston to the caliper’s inside. This is when the rust causes trouble.

At the rear side we use a 4mm hexagonal wrench, we rotate the inner adjusting gear and thrust the piston to the inside. However, the rusty piston is stuck and might easily damage the small adjusting gear and influences the O/H.

Caliper piston ASSY exchange

In the case of rust Maruha recommends an ASSY exchange.

Brake master

At the time of the caliper’s O/H the tandem master cylinder’s O/H or exchange is also a good idea.
Maruha has the original master pump too.
It is cheaper than the genuine product and its quality is very good.


Maruha Motors Co., Ltd.
Ushizuma 2095-6, Aoi-Ward
421- 2106 Shizuoka city, Shizuoka prefecture
TEL: 0081-54-294-0076
FAX: 0081-54-294-1312