TT parts (bearings)

Thanks for the plug.

Regarding "high precision" bearings, there are two basic features you need to look for in bearing specs:

1. Clearance. Usually shown as C-3 or C3. This is the normal clearance you will use in model engines. You can also use what many of the Chinese manufacturers call "standard" which is between C2 and C3. The normal range is from C1 to C5 with the C5 being the loosest and C1 being the tightest. Using a bearing with the wrong clearance can cause the bearing to wear and fail prematurely or cause other parts in the engine to wear.

1. Tolerance. This is what "high precision" usually refers to. The standard used is the ABEC series from ABEC-1 to ABEC-7 with the ABEC-7 being the highest precision. Also note that this precision is only measuring the tolerance of the concentricity between the inner and outer races and nothing else that matters to us.

Neither of these say anything about the quality of the bearings, only the measurements. An ABEC-7 bearing is not "better" than an ABEC-3 for model engines. In fact, the added cost of ABEC-7 bearings does not justify their use.

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