Speedometer/Cruise control discrepancy

[mick243]

My speedo seems to agree with gps speed. If I set the cruise control there is a difference between the set speed and the actual speed, EG, if I set the cruise to 100, the actual speed reported on the speedo is 103.
Is it possible/does anyone know how to adjust or correct this?

 

[theblet]

I hope you mean 100km/h

 

[Loudram]

His sig says he's an Aussie so he's probably talking about km/h. (I hope).

 

[Mystic Rhythms]

I have noticed that if I use cruise to increase my speed by more that a couple mph then the truck overshoots the target and seems to hang above the set point for a little while before dropping back down.
If I bump it up 1 or 2 mph it is fine, but if I hit it 5 or 10 mph it doesn't seem to like it.

 

[mick243]

Yes, I mean KPH.... but in this scenario I doubt the units matter - there is a 3% discrepancy between set point and delivered result.

and no, it doesnt matter if I bump it up in increments of 1 or 10, problem is the same.
If I'm doing a particular speed and hit "set" it will hold that speed (but if I'm doing 100 and hit "set" the cruise will show its set for 97). if I use the + to increase speed is when the problem occurs.

does anyone out there know how the speedo and cruise systems get their info from and how they interact, can they be calibrated?

 

[Darksteel165]

Yes, I mean KPH.... but in this scenario I doubt the units matter - there is a 3% discrepancy between set point and delivered result.

and no, it doesnt matter if I bump it up in increments of 1 or 10, problem is the same.
If I'm doing a particular speed and hit "set" it will hold that speed (but if I'm doing 100 and hit "set" the cruise will show its set for 97). if I use the + to increase speed is when the problem occurs.

does anyone out there know how the speedo and cruise systems get their info from and how they interact, can they be calibrated?

Have you tried replacing your battery?

It's normal for cruise control to do a few mph between your set speed
If I set it at 74mph In can expect it to sit around 73-74, but scoop down to 70-69, and up to 76.

You say that if you set it at a speed it will hold the speed, but show its set at something different?
Have you changed your tire size from stock?

100kph to 103kph is only a 2mph difference, that is well within the expected set speed for any vehicle I have owned (62.13mph to 64.00mph). Setting crise control to 62-63 (it's a fraction of the mph so if I round up setting 100KPH is like setting 62-63MPH, if the truck goes 103kph that's the same as 64mph, very close.

 

[mick243]

its a brand new truck - about 5 weeks old, everything as from the factory (except rhd conversion by ram australia, and I added wheel flares) so I'd really like to think the battery isnt toast already....
and around here there are some places where that discrepancy will cost your license, some places will book you for as little as 1KPH over the posted limit, and the vehicle traveling faster than indicated is a defectable offence.

 

[Darksteel165]

Sounds like you shouldn't be using cruise control if you expect it to never go over the set limit and you will lose your license for going 1 KPH over.

 

[mick243]

kinda true..... but then why buy a truck with a feature that's not useable......
and yes, the biggest issue really is our doucheknucke revenue raising politicians - but there is no hope of changing them, so I asked about the possibility of calibrating the system I have.....

 

[Darksteel165]

You can't expect any cruise control system to stay at the set limit 100% of the time.
If you are concerned about going 1 KPH over the set limit which is a fraction of a mph its unrealistic.

You should be setting it way under, or not using it.

I don't know of any calibration. It pulls it from the same system...

 

[J33P]

I have the same problem on my 2019. Dealer said its normal.which is BS, both other rebels my friends have if you set the cruise to 100 the speedo says 100.

I have even adjusted tire size ratio, no difference 3% like u said.

 

[kdoublep]

Mine is dead on balls accurate

 

[uku]

My speedo seems to agree with gps speed. If I set the cruise control there is a difference between the set speed and the actual speed, EG, if I set the cruise to 100, the actual speed reported on the speedo is 103.
Is it possible/does anyone know how to adjust or correct this?

Hi Mick, was just googling the c

My speedo seems to agree with gps speed. If I set the cruise control there is a difference between the set speed and the actual speed, EG, if I set the cruise to 100, the actual speed reported on the speedo is 103.
Is it possible/does anyone know how to adjust or correct this?

Hi Mick how ru mate?
Im from sydney Australia. Hubby picked up his new bighorn last week and same problem. Dealer told us that the speedo calculates spped from wheels whereas cruise control picks up from gps. Apparently there nothing you can do. I believe when you are paying $100k plus for a vehicle thats just not good enough. I also think its a safety issue as people may not realise they are going over the speed limit. Im going to try to make complaints higher up as RAM needs to fix this.

 

[Darksteel165]

Hi Mick, was just googling the c

Hi Mick how ru mate?
Im from sydney Australia. Hubby picked up his new bighorn last week and same problem. Dealer told us that the speedo calculates spped from wheels whereas cruise control picks up from gps. Apparently there nothing you can do. I believe when you are paying $100k plus for a vehicle thats just not good enough. I also think its a safety issue as people may not realise they are going over the speed limit. Im going to try to make complaints higher up as RAM needs to fix this.

I mean you can complain to Ram, but as far as I know you bought it from a reseller, not Ram. Ram doesn't manufacture trucks for Australia so a private company buys Ram's, then rips all the guts out and reassemble it (it's actually pretty cool to watch what they do) You are also paying a large importer fee, a big horn is worth half of what you pay even after currency conversions, but I know your options are limited over there.

I set my trucks speed using gps on my phone, and cruise control matches that speed.
Cruise control speed is not measured by the gps, some of the Ram's don't even have gps, they just don't know what to do so that's why they told you that.

 

[uku]

I don't know its just ****. I really can't believe that such a thing will be tolerated by the government. I will just have to research and find out which tree I need to bark up

 

[beetlespin]

Mine is dead on balls accurate

Yup