Adaptive Cruise Control - Speed Less Than Target

[msenske]

Hey there. I was using the adaptive cruise control functionality on one of the highway portions of my drive home from work today and I noticed that the maximum speed I would attain was always 1mph less than what I set as my target speed. As an example, I set the target speed to 70mph and the vehicle held a constant speed of 69mph and never once hit 70mph. Obviously, the workaround was to set the cruise control to 71mph if I wanted the vehicle to maintain a constant 70mph, so it isn’t as if I was unable to overcome the issue and get the desired result, but it seemed very strange to me. I’ve never had a vehicle behave this way. Has anyone else experienced the same issue?

 

[LCColorado]

Hey there. I was using the adaptive cruise control functionality on one of the highway portions of my drive home from work today and I noticed that the maximum speed I would attain was always 1mph less than what I set as my target speed. As an example, I set the target speed to 70mph and the vehicle held a constant speed of 69mph and never once hit 70mph. Obviously, the workaround was to set the cruise control to 71mph if I wanted the vehicle to maintain a constant 70mph, so it isn’t as if I was unable to overcome the issue and get the desired result, but it seemed very strange to me. I’ve never had a vehicle behave this way. Has anyone else experienced the same issue?

It’s a Toyota thing, don’t worry about it. My wife’s 22 Highlander and 24 Grand Highlander did the same thing.

 

[Pierac]

My LC does the same.... Drives me nuts!

 

[glibglob]

Our rav4 and my previous tacoma did it too.

 

[trek805]

mine too. You will need to adjust for daylight savings to correct it

 

[Ed1]

Mine does the same - 1 mph less than set - but only sometimes. It may be related to whether vehicle is on a slight upward incline, but not sure yet. Most of the time on level road it is on target.

 

[Midwest Duo]

Noticed as well.

 

[uraniumrich]

The ability of the cruise control to maintain a constant, steady speed is a function of the control system and programming of the computer. With the computing power available today, the LC should do a better job both hitting the target speed and maintaining the target speed even with gentle variations in terrain (up/down hills). My LC not only doesn't hit the target speed, but I find that the speed will vary up and down in normal use. Toyota can (and should) do better on a $70K vehicle. Yes, the LC is new, but the software running the ACC, engine/transmission programming, and MultiMedia screen feel vastly undeveloped and in need of updates right out of the starting gate (and lots of complaints in the Forum.) You can only beat a dead horse for so long, then your arm gets tired. Or something like that.

 

[LCColorado]

The ability of the cruise control to maintain a constant, steady speed is a function of the control system and programming of the computer. With the computing power available today, the LC should do a better job both hitting the target speed and maintaining the target speed even with gentle variations in terrain (up/down hills). My LC not only doesn't hit the target speed, but I find that the speed will vary up and down in normal use. Toyota can (and should) do better on a $70K vehicle. Yes, the LC is new, but the software running the ACC, engine/transmission programming, and MultiMedia screen feel vastly undeveloped and in need of updates right out of the starting gate (and lots of complaints in the Forum.) You can only beat a dead horse for so long, then your arm gets tired. Or something like that.

This isn’t an LC specific thing, this is the same TSS 3.0 system that’s in many of their other cars. Maybe I’m just used to Toyotas at this point, but I find most of the things people get worked up about to be a non issue. The old TSS 2.5 system was SIGNIFICANTLY worse than 3.0. Having now driven about 13000 miles in TSS 3.0 equipped vehicles I actually think the new system is pretty good in comparison to what most other non German manufacturers are putting out.

In what situations are you finding the speed to vary? I hate to ask, but you are aware that the cruise control is adaptive right? It will slow you down for corners and based on the cars ahead.