Trim v. Sub-Trim - Do you know the difference?

[@WellingtonIronman]

This is a neat explanation. My process for centering steering is always: 1) With the servo powered on and everything centred and zeroed out on the transmitter, attach the servo horn as close to perpendicular to the steering linkage as is possible 2) Using the subtrim, now set the servo horn to be exactly perpendicular to the steering linkage, so they form a 90 degree angle with each other. Ignore the position of the wheels at this point. This will ensure your steering is going to be equally progressive when turning in either direction. 3) now center the steering by adjusting the lengths of the steering linkage(s), and set the toe angle if applicable using the same method. Don't use trim/sub-trim for this. Get the steering as central as you can with these adjustments. I like to remove the pinion gear and roll the car across the floor to ensure it's tracking straight, but you can just drive it too. 4) now set the end points left and right to allow the steering to move as far as it physically can in both directions. You might end up with more steering one way than the other, that's OK, you're just making sure you know where the furthest point they can go to is. 4) next using the endpoint adjustments again, ensure the steering turns the car equally in both directions. One way to do this is place the car on the floor and drive a half circle in one direction on full lock, noting the start and ending position on the floor with a piece of chalk or something. Spin the car 180 on the spot by hand, then drive in the other direction on full lock and see if you end up back at the same place as you started. If you don't, your car has more steering in one direction than the other. In a crawler you may want to leave this as is so you have max steering in each direction, but in any other car you should reduce (not increase) the end point on one side until both sides turn equally. 5) Finally, using the trim, fine tune the steering so it is truly straight. It won't need much at all if anything. If it does, you've got something wrong and you need to go back to step 2. If you're racing you can also now use the steering dual rate to reduce the steering throw so the car isn't so sensitive, and the expo to dial out twitchiness around the straight ahead position.

[@BoomslangSuss]

I like the circle driving part. Thanks for sharing.

[@jerryvolpini7987]

Thank-you, you showed what I I've been telling people for years! Many of the manuals don't fully explain this and people can't understand why their wheels move so much more in one direction than the other. I was always taught to adjust sub-trim first.

[@BoomslangSuss]

Happy that I didn't undermine what you've been saying! Agreed - manuals do a terrible job of explaining most things.

[@Genicksalto]

Great explanation. Thank you!

[@BoomslangSuss]

Glad it was helpful!

[@pocketfuloducks1062]

Excellent, thank you!

[@henryoak2001]

Great video this explains why I was stripping servo horns and tearing up mounts as I was using sub trim to do that, my next question is when would I need to use subtrim

[@BoomslangSuss]

I explain the best order of steps in the video. Because your servo horn can only be set at 14° increments, the very first thing you do is use sub trim to set your zero point so the horn is exactly where you want it. Then don’t touch it after that. Then set your endpoints and do any fine-tuning with the trim.

[@henryoak2001]

@@BoomslangSuss thank you I found the video and followed the sequence you laid out, super helpful, I appreciate it. I’ve watched most of the videos and have learned so much.

[@BoomslangSuss]

@@henryoak2001 So happy it helped!