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Rear Brake Wheel Cylinders

Gil’s Garage

Gil Baumgartner
CTCI Authenticity Chairman

This information applies to drum brake cars only. I have detected a potential problem when purchasing rear wheel cylinders for 1957 Thunderbirds. Some cylinders are being boxed wrong. The 1956 and 1957 rear wheel cylinders have a 15/16″ bore with 15/16′ internal rubber cups. The 1955 rear wheel cylinders have a 7/8″ bore with 7/8″ internal rubber cups. I have found 1955 wheel cylinders with 7/8″ bore in boxes marked for 1957 models P/N B7A 2261/2- A which should have a 15/16″ bore.

The potential problem is the smaller 7/8″ bore cylinders when installed on a 1957 with larger rear drums and shoes could cause rear wheel lock up especially on wet pavement. Wheel cylinder bore can be checked. by removing the rubber dust covers on the end.

The attached picture shows the small 7/8″ wheel cylinder on the left and the larger 15/16″ cylinder on the right. The cupped metal piston may differ in appearance as do the two in this picture.

Gil Baumgartner

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