I have a question about traction/stability control

[bjamesW32]

Forgive me but I hope this is a generic enough question to ask here.   I drive a Chevy city transit bus.   

 

 

We have a small fleet of these.   Upon delivery of the newest half dozen busses a lot of the drivers are uncomfortable driving them in the snow.  Complaints of getting stuck in one inch of snow?   Getting 'stranded' half way out into an intersection.    Inability to scale even the mildest of snowy grades.   A couple of the most veteran drivers do not like to be assigned to them.   I thought they might be exaggerating.   Yesterday I was assigned one of these newer buses for the first time.    Each of the above complaints quickly materialized for me.  It was maddening.   Everyone just writes it off to "shitty traction control" getting in the way of driving.  There is a dash panel switch that toggles it on and off and the dash leds announce that it is on or off accordingly.   But either mode makes no difference.   

 

I decided to get really curious.    I went back to the places where I got "stranded" in the snow and noticed in each case that my front tires were on dry clear pavement while the rears were on ice or snow.    I went through half a dozen tests in a vacant parking lot where I could safely position the bus accordingly....  front tires on clean pavement and rears on ice/snow.    Every time,  the moment the rears began to slip, the front brakes were engaged.  Actually locked up.    I cannot believe this is normal.  Is it?    It turns out that this explains every complaint heard so far from drivers.    On even mild snowy grades the bus would just shudder to a stop on the ascent the very moment the rear wheels lost traction.   The front wheels were getting locked up by the traction control.  All of this while accelerating, but not touching the brakes at all.   The only way to release the front brakes is to step on the brake pedal again.   On the very same grade I could ascend it without trouble as long as I kept it to 1mph and crawled carefully without allowing the rear wheels to break loose.   

 

The getting stranded at an intersection is as well explained.   if the front wheels enter the dry zone beyond the crosswalk and the rear wheels break loose even a little, the traction control locks the front brake and the bus is hanging out in the open intersection.   The drivers that complained about this said they were forced to stop and reverse out of traffic.   I'll have to explain to them that they can tap the brakes to release the front end and continue on carefully.    But this cannot be right.   Can it?

 

From an hour of search on the internet the only possible explanation I can find is that these transit busses may come with the full suite of traction and stability control software and (possibly?)  what ford and chevy refer to as "line lock" mode was accidentally enabled.  It fits the behavior to a T.   It's a mode designed for the race track to enable drivers to warm up their rear tires.  Spinning them automatically locks the front end and can be programmed to "launch" at certain points.    And sure enough, the service page on this mentions that tapping the brakes will override the lock and release the front end.   

 

I want to bring this up with my boss but don't want to look foolish for doing so.  Am I right to be concerned here?    Or are we all just being impatient with new technology and learning how to cope with it? 

 

Thanks for any suggestions. 

Edited December 21, 2022 by bjamesW32

[movario]

19 hours ago, bjamesW32 said:

I want to bring this up with my boss but don't want to look foolish for doing so.  Am I right to be concerned here?    Or are we all just being impatient with new technology and learning how to cope with it? 

 

Thanks for any suggestions. 

 

This new technology is over 30 years old. So even experienced drivers should know this technology by now. The way you describe that traction control is working at the moment doesn't seem to be right. Normally, the traction control should slow down the tire spinning to fast by applying the brakes and reducing engine torque. The wheels that stand still should be able to spin freely.

 

You could lift that vehicle off the ground so that all the wheels are able to spin freely. When you then start to "drive" you can check if the front wheels are really locked. If that is the case something is wrong.

 

Another question. That vehicle seems to be quite heavy with a lot of weight on the rear axles. Why are the wheels starting to loose traction so fast in the first place? Your choice of tires may not be right for a snowy environment.

[CamGTP]

We have a 2022 Chevy box truck that is part of our fleet with Penske for my work, the traction control can be pretty bad at times but it doesn't do what yours is doing. I can still power through wheel spin and it never locks the front wheels up, it just doesn't want to move real quick.

 

If you press the button on the dash the traction control turns off but then if you press and hold the button again for 10 seconds or so it should disable the stabilitrak feature that lets you basically do anything. But the catch is that the stabilitrak I believe turns itself back on again after 35 mph.