Community Forums

duanetf1234 · 03-23-2018, 12:16 PM

I have a 2018 Newmar DSDP 4369 on a Spartan Chassis.
I noticed that when my speedometer showed a speed – let’s say 60 MPH, my GPS showed a speed 5 MPH faster. Curious as to which was correct I had my wife drive her Lexus alongside when I was going 60 per my speedometer and she reported that I was really going 65 according to the Lexus, which concurred with my GPS.
I called Spartan and asked if there was an adjustment available to correct this and their response was “that difference is within our specifications”. I was surprised at this response to say the least.
So, be careful. You may be driving faster (or who knows) slower than you think if you have a Spartan chassis. I suggest you verify the accuracy of your speed indication.
Duane Frederiksen
2018 DSDP with Spartan Chassis

IBDAGRIZ · 03-23-2018, 12:26 PM

I've used the mile markers on the freeway to check my cars when swapping tires a bit taller than stock.

I prefer to drive at least 20 miles to see how close you really are compared to the odometer.

Griz

NealC · 03-23-2018, 12:55 PM

Wow. That's pretty sloppy. Keep that inaccuracy in mind with your tire max speed limit.

GaryKD · 03-23-2018, 01:43 PM

My speedo is the same as the Garmin GPS reading.

Rotten-Red · 03-23-2018, 01:44 PM

Quote:

Originally Posted by duanetf1234

I have a 2018 Newmar DSDP 4369 on a Spartan Chassis.
I noticed that when my speedometer showed a speed – let’s say 60 MPH, my GPS showed a speed 5 MPH faster. Curious as to which was correct I had my wife drive her Lexus alongside when I was going 60 per my speedometer and she reported that I was really going 65 according to the Lexus, which concurred with my GPS.
I called Spartan and asked if there was an adjustment available to correct this and their response was “that difference is within our specifications”. I was surprised at this response to say the least.
So, be careful. You may be driving faster (or who knows) slower than you think if you have a Spartan chassis. I suggest you verify the accuracy of your speed indication.
Duane Frederiksen
2018 DSDP with Spartan Chassis

That can be adjusted at Cummins.

Algoma · 03-23-2018, 04:06 PM

My Freightliner is within 1mph of the GPS so I don't think Spartan can justify a 10% difference. Maybe worth checking what the legal requirement is as I seem to remember it used to be 3%.

Rotten-Red · 03-23-2018, 04:41 PM

A while back I changed tire size. The larger tire slowed my speedometer by 3 mph. I took it to Cummins and they programmed in the new tire size and brought the speedometer back into accuracy. Mine matches right up with my Garmin.

It's possible someone may have entered the wrong information into the ECM, tire size or a drivetrain component. These speedometers are not like the old cable driven ones. Everything is electronic and if the wrong info is entered into the ECM they will not be accurate.

Tigerfan1 · 03-23-2018, 07:10 PM

I went from 275/70 to 275/80 tires and it registers 60 when I am actually going 65. When I was at Spartan to get my ball joints changed they adjusted the speedometer for that tire size. A year later I had some engine work done at Cummins they inadvertently reset the computer back to original specs and I am 5 mph slow again. Next time I am at Cummins I will have them reset it.

willipaul · 03-23-2018, 07:59 PM

mine is within 1mph of my good sam gps...

and i am also surprised at spartan's response...

siggyd · 03-23-2018, 08:09 PM

My GPS matches the speedometer at 60 mph. Tires are 305-70-22.5
Siggy

StuartS · 03-23-2018, 08:31 PM

2017 Spartan 43" Dutch Star & mine is within 1 mph of my Garmin RV GPS & Waze GPS.

Brigadoon · 03-23-2018, 09:10 PM

That's an easy fix. Most Cummins shops should be able to quickly reset your speedometer. They just plug in their laptop and punch in the new parameters. I have always found Spartan to be very responsive and knowledgeable any time I have called them. Disappointing that you had an unsatisfactory experience.