TT01 has a very tight compartment for motor and gear. If you are using non-Tamiya pinion, make sure it is mounted appropriately so that it won’t scratch on the plastic surrounding it.
With a 55T spur, you can use a 29T pinion. 58T spur the max pinion is 25T. 61T spur the max pinion is 22T. A lot of the charts out there says 55T spur works only with max 28T pinion, but we have tested the use of 29T (mounting position D), it still fits in.
For stock silver can, the BEST possible configuration (performance and reliability wise) seems to be 58T spur and 24T pinion. If you use more aggressive setting the silver can may burn out fast.
Also, when the spur has been used for awhile, the teeth may go flat so you may need to change the motor mounting position (by moving one step up – refer to the instruction that comes with your motor mount) so to keep proper meshing.
If you have the proper gearing radio, even a stock brushed motor will run pretty fast:
