MG TC Wheel Cylinders

[timandgerda]

Hi - can someone please confirm the thread size for the front and rear wheel cylinders please? I am talking about what anchors the cylinder to the back plate. Thanks. Tim.

[timberstone]

Tim, Hope you do not think your TABC friends are ignoring you, so Merry Christmas and Happy Holidays !!

If you have the original Lockheed wheel cylinders the threads are 'merican
Not sure what threads any other wheel cylinders will have, but a recent rear wheel cylinder from China also had the 'merican threads.
Saying 'merican instead of UNF or ANF because even though the diameter is quarter inch the TPI is not common --seems to be fine threads per inch of about 28. Not usually stocked at the corner hardware store. (I will have to go look at my supply to count the TPI).
Seems that by the time I found the little bolts, they were the same cost as those sold by Doug Pelton.

Additionally, the ORIGINAL head size of the rear wheel cylinder bolts is either a BA or BSF size that is difficult to fit into common wrenches. These heads are commonly rounded by using the wrong sized wrench and ham hands. So, many rear wheel cylinders will be fitted with non-original bolts
-- so I too need to get the original bolts anyhow!!

[Duncan M]

Mounting bolts for wheel cyl's were originally 5/16 Whitworth bolts which are 18 TPI and the head was intentionally undersized to take a 1/4W wrench. 18 tpi 5/16W threads are similar to 5/16UNC 18 tpi. See: https://mossmotors.com/media/instructio ... 0_INST.pdf

[timberstone]

The full dimensions for fastening bolts (replacement and original) for the ORIGINAL Brake wheel cylinders are the following (as listed by From The Frame Up):
FRONT WHEELS
BSP134 5/16 UNC x 18 TPI length is 5/8” -- 2 replacement bolts required for each original wheel cylinders
BSP135 5/16 UNC x 18 TPI length is 5/8” with head 5/16” – Original bolt -- 2 required for each original wheel cylinder

REAR WHEELS
BSP123 ¼ UNF x 28 TPI length is ½” Replacement bolt for original cylinder 2 required for each original wheel cylinder
BSP124 ¼ UNF x 28 TPI length is ½” Original bolts with small 3/16BSF hex head 2 required for each original wheel cylinder

[timandgerda]

Thanks Duncan/Tim. I have checked my wheel cylinders with taps and found them to be 5/16 UNC and 1/4 UNF as you mention above.

[Duncan M]

Just for the record, the TC was not made with any UNC or UNF threadform bolts attached. The ones in front had BSW threads (18tpi) and a 1/4W head, and the rear cylinders were mounted with bolts with BSF threads (28tpi) and (I think) 3/16W heads.

Typically new hydraulic wheel cylinders come with new bolts with (obviously) compatible threads.