HPI Erratic Steering

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huff0442

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I recently finished building a HPI Baja SBK. My issue is the steering is very unpredictable. If I hit the slightest bump or even the crown of the road, it will dart quickly to one side or the other, making it almost undrivable. Driving on hard pack, asphalt or grass has the same results. My first thought was the steering servo saver (common issue), so I installed a TR HD servo saver from DDM. No help. So maybe it's the stock tires? Picked up a set of Mad Max assemblies from DDM, made no change. Thinking that alignment is the issue I picked up a Integy setup station to get some base line numbers. Below are my settings. Basically the stock setup:

Front:
Camber: -4
Toe: -2
Caster: 25 (hard to measure accurately)

Rear:
Camber: -5
Toe: -4
Caster: 5

This isn't my first RC. I've run 1/8 Nitro in the past and I've never had this many issues. Reaching out to the group here looking for advice. Am I missing something?

Thanks for your help,

Kevin
 
Ferrebee88 said:
Which servo are you using? What voltage are you running the servo? I can’t compare the a-rms to stock, but mine is very stable with the FLM extended aluminum a-arms.
Click to expand...
Spektrum S9120BL @ 6v. I'll upgrade it later to 7.4 LiPo but need to upgrade the T/B servo first.

However, I may have figured something out. I'm running a MOD kill switch. When I unplug it from the harness that goes to the engine (G320RC), it tracks straight as an arrow. Tried the plug/unplug test several times to confirm. Does that make sense? I have MOD inside my battery box with my receiver. Would moving the MOD and the wires going to the engine make a difference or is this just a flaky unit?
 
huff0442 said:
Spektrum S9120BL @ 6v. I'll upgrade it later to 7.4 LiPo but need to upgrade the T/B servo first.

However, I may have figured something out. I'm running a MOD kill switch. When I unplug it from the harness that goes to the engine (G320RC), it tracks straight as an arrow. Tried the plug/unplug test several times to confirm. Does that make sense? I have MOD inside my battery box with my receiver. Would moving the MOD and the wires going to the engine make a difference or is this just a flaky unit?
Click to expand...
i don't own a mod switch but just had a read of the instructions online and it should work fine fella,
but check the clip on ferrite filter is on the main wire to the coil, that could cause interference issues if its missing or damaged,
also try and place the switch in a different place away from servo wires in the battery box and try again,
its something simple cos the mod switches seem to be pretty simple in design, theres no dip switches to set cut off voltage etc,
 
spents said:
i don't own a mod switch but just had a read of the instructions online and it should work fine fella,
but check the clip on ferrite filter is on the main wire to the coil, that could cause interference issues if its missing or damaged,
also try and place the switch in a different place away from servo wires in the battery box and try again,
its something simple cos the mod switches seem to be pretty simple in design, theres no dip switches to set cut off voltage etc,
Click to expand...
The ferrite is place. I am going to try moving the wiring to the left side of the chassis to get father away from the servo's and see if that solves it.
 
I solved the issue! Moving the MOD kill switch had no affect. I read online that the Spektrum AVC is still active even when set to INHIBIT on the transmitter. You have to manually disable it at the receiver as the steering servo is always checking for center. This solved the problem. Tracks straight as it should! Thank you so much for the help and advice! If anyone else has this issue, here is the video about disabling AVC. https://www.rccaraction.com/spektrum-quick-hit-tech-tip-disable-avc-video/
 
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