Optima gearing with modern motor

[VintageRacer]

Having recently bought some electronics with the intention of getting my Optima running again I have a question about gearing.

As far as I can determine the Optima has an internal ratio 3.03:1.
The instructions of my 17.5 LRP X12 recommends 7:1 overall ratio as a starting point.

I am using an after market tufnel and steel 'spur' with 39t.

By my maths this means I need to use either a 16t (under geared) or 17t (marginally over geared) pinion.

These are higher than I used to race with, usually using around 12-15t pinions with a 27 turn motor and I remember people using 10t with modified motors.

Can someone confirm I have calculated this correctly and reassure me I'm right before I a) buy a new pinion b) over heat my motor.

If this is right what would be the effect (other than reduced top speed) if I use my existing smaller pinions.

Cheers.

[Gayo]

Hi,

I am also building an Optima runner, but I will use some of my remaining brushed stuff. Thinking about 13x1, that should be close to your 17.5.

I find that brushless motors are rather tolerant with ratios. You can throw in whatever pinion you have, and if the car is not quick enough, just gear up, it will not affect acceleration. Run a few laps, then check motor temps. Too low or too high ratios makes the motor hot, so that should be closely monitored to find the best ratio.

Don't think too much about what we used to run back in the days. Motor magnets were weaker, brushes were soft and low quality, and I won't comment about batts!

Optimas are soo cool! Please post about your runs.