Originally Posted by
redbones
Thanks for the quick reply.
I'm going to run my LRP TCspec with a 17.5Duo(middle hole). The track has a 120ft straight and top speed do matter. Some people have suggested a 3.5fdr, but I think that is too much. I am looking at around 4.0. With the current pinion set that I have, I can go from 38 to 46. Which means I need a spur of about 75. But What worries me is the amount the motor can move. I don't want to buy a gear set that I won't be able to mesh at all. What would be a safe spur/pinion combo to achieve the FDR for the 17.5 class? Thanks
Well at the track that I posted the aerial shot of, when I was running a TC spec sphere, I ran mine on profile 8 and a 17.5 duo with middle timing and 4.3 fdr on my 416. Maybe wasn't the fastest car on the straight away but I wasn't far from it. At that track most of the time you can make is in the infield. But if your track is very high speed all the time with no tight turns, 3.5 4.0 would probably be good. If you could fit it, try a 90 spur with a 54 tooth pinion. That gets you a FDR 4.06. But with me I always try to run the biggest spur I can for more punch out of corners and gear to wear I top out about mid way of the straight. Yeah, people might catch you at the end of the straight, but you can leave them in the turns and thats where people make mistakes usually.