SX internal ratio changers
 

The internal transmission ratio's (2.4, 2.6, or 2.8:1) are changed i know by changing 34/22, 33/23 and 32/24 but which is which ? And do you only change them to get the desired ratio ?:)

As far as the manual goes I thing you will find that the overall ratios are as follows:-

34/22 = 2.78
33/23 (std) = 2.58
32/24 = 2.4

In Si Moss setup sheets it talks of a 36t idler but I cannot see that in the parts list and am unsure of the size of the other gear that would go with it.

Click here for a gear ratio chart spreadsheet in Excel format for the CAT SX.

As you've said, there are 3 different pairs of gears, which give you 3 differnet ratios. I have been using the kit std one for a while to be honest.

I ran my car on Friday indoors and ran the std pulleys and spur gear with a 21T pinion which gives an overall ratio of 10.21 and this was on a 5.5 Team Orion motor and LRP Spere TC ESC and felt that it had a very high top speed but felt that it was a bit gutless in the infield. When I have looked at the ratios I noticed that on my X-5 I used to use 16/108 which gave me an overall ratio of 11.81 so I may try getting closer to this so I expect an 18t pinion is nearest on the standard setup.

Good stuff, cheers boys.

What's the advantage of being able to change the internal ratio?

In a nutshell you can fine tune your car for optimized brushed and brushless ratio's.

Especially stock brushless!