answer needed
 

I am switching to 64P gearing. I want an FDR of 5.0 (or close to that). I understand I can get this by a variety of spur/pinion combinations. My question is this. For example If I go 88 spur and 44 pinion or 104 spur and 52 pinion i still get an FDR at 5.0, is one going to be better than the other. I want to get a single spur and then a couple pinions to get things dialed in. Please help me out. Another issue is if the combination I want will actually fit in my TC4. thanks in advance.

Some will argue that it does make a difference...but you are not likely to be able to tell.

i tried most combinations on my TRF when i bought it and i decided the best spur to use was the one that gave me the most scope for changing gearing easily only changing the pinion

i normally use about 96 to 99 depending on the track

but now on the indoor track i am running a 105 with a 33 tooth pinion

Niznai has a post here dealing with the physics of the gears spinning and what different sizes do to the loads on them and such.

With the belt drive cars, I usually only duplicate ratios with different gear combos to move my motor weight frontwards or backwards.

While the torque part of that is interesting and probably right...he fails to take in account that gears become more efficient when they have more teeth meshing. So any loss of efficiency due to the larger gears would be at least compensated for by the gained efficiency of more teeth being meshed.

In the end what it means is any losses or gains are so minimal they would not be noticed if even measurable.