Originally Posted by mingnon
Is anyone running this in 21.5 class? if so what spur and pinion are you using
I was orginally going to run it 21.5 for Challenge Cup rounds. But decided to just keep it in stock instead.
The guys who are running 21.5 seem to be gearing for anything between 4.0 and 2.8 depending on track size and motor timing.
To get that low with the XI you'll need to go down to at least the 65t spur. You can fit as small as a 60 if you want to custom drill the holes in it. With a spur that small you can get at least a 42t pinion on there. To help you can use the root arm from the Zero vertical motor mount, or grind away some of the stock root arm.
3Racing have a new motor mount listed as coming soon on the spare parts section of the website. Its a horizontal motor mount, like the one on the Zero S, but obvioulsy redesigned for the XI. That would give you even more gearing options.
------- Testing ---------
So I hit the track today with some friends, shiny new XI converted to DH version. I settled on 5.75 front springs and 6.0 rear, sorex 36 rubber.
With the new servo position, I actually turned down the steering expo from -30 back to 0. The car has a nicer feel to it now then in the standard XI configuration. My first thought is the car now has loads more steering then it did. Especially on power through the sweepers, and the overall grip seems higher.
Something else I tried today was going to a front gear diff instead of the spool. It did cost me a tiny amount of steering through the sweepers, but with the new car that's still better then it was. It had a hint more turn in through the chicanes, and overall just felt nicer to drive. I was using 300000wt oil in the front diff, with 80wt (1000cst) in the rear.
My setup wasnt too different with the new chassis to the last. But the basics are:
Boosted 17.5, med-low grip asphalt, R9-R body, Sorex 36
3 hole piston
Longest upper arm length
ride height 5mm
shortest upper arm length
Ride height 5.5mm
Still need to fiddle with the rear. I'd like to try -2 toe with -2.5 camber. And add the roll bars back.