I wonder.. Do you have a t-maxx? do you have a maxx with a .247 or a sirio .18 or any first had real world experience with them?

My maxx with a 247 and 1/8 scale 20/51 gearing vs my buddy's .18 sirio with stock 20/72 was no faster than my maxx. they were about equal on all counts. Trinity said to gear the sirio just like the stock 2.5 and it was. He had the engine running really strong too temps in the 240's.

T-maxxes suffer from pretty bad chassis flex especailly with they have super powerfull engines in them. that is why they strip lots of spur gears hence aluminum braces and alloy skids which helped solve that problem. It worked wonders on his maxx as he didn't strip out any more spur gears. The $10 traxxas forward only conversion is junk and breaks with any real power droped into it. heck I striped out my traxxas forward only with an os .15 CVx. So the only other alternative is a good and more expensive forward only converion. A .247 has a heck of a lot of power. easily more than the sirio but the sirio revs to a higher rpm. A .247 with a large clutchbell can easily have just as much top end speed as a sirio .18 and not loose in aceleration.