KINGLS430

I took my car in for the 60,000 mile service the other day and i had noticed that the active radar was running about 4 mph off what i set it at so i asked them to recalibrate it so it would run the way it was supposed to. I was told the recalibration or the radar was impossable?! Mind you i have the same size rims and tires as the stock ones when the car was given to me has anyone had a similar problem?

GRAND_LS 4

iTrader: (2)

What you do you mean 4MPH off?

KINGLS430

Say i set my active cruise control at 75 mph the car will really be going 71 or 72 mph

GRAND_LS 4

iTrader: (2)

Let me ask you one more question to be sure. Do you mean that you set it to 75, and the speedo indicates 71, or 72?

Or that you paced it with another car, and figured that the speedo itself is wrong?

KINGLS430

i set the active cruise control at 75 and the speedomoter reads diffrent i also tested it by telling my friend to drive next to me at 75 mph we did this 3 or 4 times and it is not working correctly.

bigcory

ttt- curious about the fix

KINGLS430

I was told by the regional service manager that they have never experinced this problem before still looking for anwsers

GRAND_LS 4

iTrader: (2)

That is very strange. Haven't seen that myself before. Is the car under warranty btw? If so, they should replace parts involved till they get it right.

Has this started out of nowhere? To be honest, I wouldn't even know where to begin diagnosing this issue. Since it involves a lot of unknown variables.

KINGLS430

Th eprevious owner had the stock 18 inch rims on the car when he purchased it brand mew he thought the ride was too hard so he got the 16's put on and it softened the ride a lot the only thing the tech told the previous owner was that when he set the radar he would be going slower than it said he was going because of the diffrent size tires from the 16 inch rims to the 18 inch rims. This was the case when i got the car but now that i put the same size rims and tires as the car had stock i figured it would fix itself. And it has not i even tried resetting the computer and nothing has worked yet.

bigcory

So when you set it at 75, but the speedo reads 71, what does your friends speedo read when he paces you?

Minus the AR, is the speedo acurate when compared to your friends? This should be the same with stock size rims and tires(if the tires are larger it can effect this as well).

Is the difference between the AR setting and actual speed similar with varations in speed? Still off by 4mph at 40mph, 50mph, 70mph?

You said you attempted to reset the computer. By unplugging the battery terminals for an extended period of time? That would have been my first thought to try. Or pull the fuse for the AR for a few minutes then replace.

KINGLS430

when my friend was pacing me he was doing 75 on the dot. When i set it at 45 mph or lower it does the speed limit however when i go higher the speedo reads 3-4 mph below the selected speed. And yes the way i reset the comp was by unplugging the batery for about 2 hours.

VQT

You put back the stock rims back to the car, do you mean the 245-45-18 rims or 225-55-17 rims?

If you have a portable navigation which can tell the spped of the car, I think everyone of them do. Try that and see if any of your car speed, the portable navigation speed indicator and your friend car speed match. I bet you all three have different speed. I would say the portable navigation speed indicator is the most accurate one.

KINGLS430

They are 18x7.5 with 245/45 ZR18. What kind of portable navigation are you talking about like a garmin or a tom tom?

VQT

Yes, I have a Magellan and it can show the speed of the unit (the vehicle). I assume that Garmin or Tom Tom can do the same.

KINGLS430

I borrowed my friends magellan and the same thing happened it;s exactly 4 mph off