Originally Posted by Cloaked
I just picked up a 2nd hand T4 and will be running 21.5 blinky class.
I know I need an FDR between 3.00 to 3.5, so I went and ordered a 38t Pinion and a 69t Spur Kimbrough spur.
it was only afterwards I should probably ask one here haha, so what gearing should I be looking at for 21.5 blinky?
Sorry if this has been asked before I did a search for 21.5 but nothing specific came up.
FDR will also be impacted by the track you run at and the motor choice.
I see you are in Sydney. I run a T4 in 21.5 at SMA (Tempe) and use a 48 pitch, 64T Spur with a 43T pinion which gives you a 2.83 FDR – that is running a Reedy (V1) motor. Other guys will run lower gearing with an FDR around 3.2 if running a motor such as a Tekin Gen2 which prefers to rev more. There is usually a "sweet spot" combination of FDR and static timing for each motor.
Two things you will need to be careful with;
1. Do not put too much timing on the can itself if you intend on running the ridiculous gearing we are using. (At the NSW State Titles on the weekend, one of the drivers was running an FDR of 2.2 with no timing on the can – not a T4 though). Then temp check after 2 minutes and adjust as required.
2. Take care that the pinion does not foul on the motor mount screws. There’s not much room between the top deck on one side and the motor mount screws on the other. I believe this has been addressed with the recessed motor mount in the T4 ’14.
Not sure about the Kimbrough spur. I usually use Xray or RW Racing. Northern Beaches Hobby Centre (NBHC) and Powerhouse Performance both race at and sponsor SMA and will help with parts.
If you get to SMA come and see the seniors running T4’s – we will be happy to assist. You will find the guys at Castle Hill and Riverstone will also be very helpful. Riverstone is a smaller tighter track and gearing will be significantly shorter – and it’s usually cool inside so they run hotter tires.